JP2013038072A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery achieving excellent high-temperature cycle characteristics and inhibiting degradation in low-temperature discharge characteristics in the cycle.SOLUTION: The nonaqueous electrolyte secondary battery comprises a nonaqueous electrolytic solution containing a lithium salt and a nonaqueous solvent in which the lithium salt is dissolved, and a negative electrode and a positive electrode capable of absorbing and desorbing lithium ions. The negative electrode contains a negative electrode active material composed of a carbonaceous material whose surface oxygen concentration O/C, obtained by X-ray photoelectron spectroscopy, is 0.8 atom% or higher, and the nonaqueous electrolytic solution contains a compound having an isocyanate group.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more specifically, to a non-aqueous electrolyte containing a specific compound having an isocyanate group as an electrolyte and a negative electrode with a surface oxygen content (O / O) determined by X-ray photoelectron spectroscopy. C) relates to a non-aqueous electrolyte secondary battery including a negative electrode active material made of a carbonaceous material having a specific ratio.

  Non-aqueous electrolyte secondary batteries such as lithium secondary batteries are widely used as power sources for so-called portable electronic devices such as mobile phones and notebook computers, to in-vehicle power sources for automobiles and large power sources for stationary applications. It is being put into practical use. However, with the recent high performance of electronic devices and the application to in-vehicle power supplies for driving and large power supplies for stationary applications, the demand for applied secondary batteries is increasing, and the high performance of the battery characteristics of secondary batteries is increasing. For example, it is required to achieve a high level of improvement in capacity, for example, high capacity, high-temperature storage characteristics, cycle characteristics, and high-speed charge / discharge characteristics.

  The electrolyte used for the non-aqueous electrolyte lithium secondary battery is usually composed mainly of an electrolyte and a non-aqueous solvent. The main components of the nonaqueous solvent include cyclic carbonates such as ethylene carbonate and propylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; cyclic carboxylic acid esters such as γ-butyrolactone and γ-valerolactone. It is used.

As one of the efforts to improve the long-term durability of lithium secondary batteries, by adding a specific compound to the above electrolyte, a passive film is formed on the negative electrode in the initial stage of use of the battery. Efforts are being made to suppress side reactions such as reductive decomposition of solvents.
Examples of such compounds include compounds containing an isocyanate group in the molecule. Patent Document 1, Patent Document 2 and Patent Document 3 disclose that cycle stability is improved by adding a low-molecular compound having an isocyanate group, a chain isocyanate compound or a diisocyanate compound to the electrolyte solution, respectively. ing.

  In addition to the electrolytic solution, there is an attempt to improve the performance of the battery by modifying the surface of the negative electrode active material. For example, Patent Document 4 discloses that a lithium ion secondary battery using an aqueous binder can be charged at high speed by mechanochemically treating graphite particles and hydrophilizing the surface of the graphite particles. ing. However, such a chemically active surface can be expected to have higher performance by application, for example, in combination with an appropriate electrolyte component, but such technical development is still not sufficient.

JP 2005-259641 A JP 2006-164759 A JP 2007-242411 A JP 2003-132889 A

As described above, when a compound containing an isocyanate group in the molecule (hereinafter referred to as “isocyanate compound” as appropriate) is included in the electrolyte, an improvement in durability can be expected. May not appear in This is because an appropriate battery design based on the action mechanism of the isocyanate compound has not been made, and the surface physical properties of the negative electrode active material must be appropriately selected in order to further improve the long-term stability of the battery. .

  As a result of intensive studies to solve the above problems, the inventors have found that the negative electrode used in the non-aqueous electrolyte secondary battery has a surface oxygen content (O / C) required by X-ray photoelectron spectroscopy. By including at least one compound having an isocyanate group in the non-aqueous electrolyte containing a negative electrode active material composed of a carbonaceous material of 0.8 atom% or more, the cycle characteristics at high temperature are remarkably improved, and the cycle The present inventors have found that a non-aqueous electrolyte secondary battery with small deterioration in low-temperature discharge characteristics can be realized, and have completed the present invention.

That is, the gist of the present invention is as follows.
A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte solution containing a lithium salt and a non-aqueous solvent for dissolving the lithium salt, a negative electrode capable of occluding and releasing lithium ions, and a positive electrode, comprising: X-ray photoelectron spectroscopy A negative electrode active material made of a carbonaceous material having a surface oxygen content (O / C) of 0.8 atom% or more determined by the method, and the non-aqueous electrolyte contains a compound having an isocyanate group This is a non-aqueous electrolyte secondary battery.

  Another gist of the present invention is that at least a part of the compound having an isocyanate group is a compound represented by the general formula (1).

(Wherein, A represents a hydrogen atom, a halogen atom, a vinyl group, an isocyanate group, or a _C 1 ~
C represents a _{2 0} aliphatic hydrocarbon group (which may have a hetero atom) or a C ₆ -C _{2 0} aromatic hydrocarbon group (which may have a hetero atom). B is an oxygen atom, S ₂ O ₂ , OSO ₂ , SO 3, OCO, COO, or a C ₁ to C ₂₀ aliphatic hydrocarbon group (which may have a hetero atom), or C _{6 to} C _{2. 0 represents} an aromatic hydrocarbon group (which may have a hetero atom). )
Another gist of the present invention is that at least a part of the compound represented by the general formula (1) is a compound represented by the formula (2).

(Wherein x is 4 to 12)
Another gist of the present invention is that at least a part of the isocyanate group-containing compound has a compound represented by the general formula (1) and / or an average functional group number of 2 or more and a number average molecular weight of 300 to 5000. The polyisocyanate.
Another gist of the present invention is that the isocyanate compound is contained in an amount of 0.01% by mass or more and 5% by mass or less based on the entire non-aqueous solvent.

Another gist of the present invention is that the surface oxygen content (O / C) obtained from the X-ray photoelectron spectroscopy is 1.0 atom% or more.
Still another subject matter of the present invention, the negative electrode, the Raman R value, defined as the ratio of the peak intensity of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 in the argon ion laser Raman spectroscopy is 0.10 or more And including a negative electrode active material containing at least one carbonaceous material.

  Another gist of the present invention is to provide surface oxygen of the carbonaceous material by a mechanochemical treatment in the presence of oxygen.

The present invention provides a non-aqueous electrolyte battery in which the cycle endurance characteristics of the battery are significantly improved, particularly in the design of high capacity lithium secondary batteries. The reason for this is estimated as follows.
According to the present invention, by including an isocyanate compound in the electrolytic solution, a high-quality film that effectively suppresses reductive decomposition of the solvent is formed on the surface of the negative electrode active material. Furthermore, a part of the film seems to be firmly bound by a strong interaction with the oxygen functional group on the surface of the negative electrode active material. As a result, the physical and chemical stability of the coating during repeated charging and discharging is increased, and the reductive decomposition inhibiting effect can be maintained for a long time.

  Further, the effect of the isocyanate compound on the cycle characteristics is bordered by the oxygen functional group amount on the surface of the negative electrode active material, that is, the surface oxygen content (O / C) of about 0.8 atom% obtained from X-ray photoelectron spectroscopy. It has been found that the effect tends to increase dramatically as the surface oxygen content (O / C) increases. The reason for this is not clear at present, but it seems that the strength of the above-mentioned interaction depends on the amount of oxygen functional groups.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments, and can be arbitrarily modified and implemented.
1. Negative electrode The negative electrode used for the non-aqueous electrolyte secondary battery of the present invention is a negative electrode capable of occluding and releasing lithium ions, and includes a specific negative electrode active material. The negative electrode active material used for the negative electrode is described below.

<Negative electrode active material>
As a carbonaceous material used as a negative electrode active material,
(1) natural graphite,
(2) a carbonaceous material obtained by heat-treating an artificial carbonaceous material and an artificial graphite material at least once in the range of 400 to 3200 ° C;
(3) a carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different crystallinities and / or has an interface in contact with the different crystalline carbonaceous materials,
(4) A carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different orientations and / or has an interface in contact with the carbonaceous materials having different orientations,
Is preferably a good balance between initial irreversible capacity and high current density charge / discharge characteristics. Moreover, the carbonaceous materials (1) to (4) may be used alone or in combination of two or more in any combination and ratio.

  Examples of the artificial carbonaceous material and artificial graphite material of (2) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, those obtained by oxidizing these pitches, needle coke, pitch coke and Carbon materials that are partially graphitized, furnace black, acetylene black, organic pyrolysis products such as pitch-based carbon fibers, carbonizable organic materials and their carbides, or carbonizable organic materials are benzene, toluene, xylene, quinoline And a solution dissolved in a low-molecular organic solvent such as n-hexane, and carbides thereof.

<X-ray parameters>
The d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method of carbonaceous materials is preferably 0.335 nm or more, and is usually 0.360 nm or less. 350 nm or less is preferable, and 0.345 nm or less is more preferable. Further, the crystallite size (Lc) of the carbonaceous material obtained by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.

<Volume standard average particle size>
The volume-based average particle diameter of the carbonaceous material is a volume-based average particle diameter (median diameter) obtained by a laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and 7 μm. The above is particularly preferable, and is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, further preferably 30 μm or less, and particularly preferably 25 μm or less.

When the volume-based average particle size is in the above range, the loss of the initial battery capacity due to the increase in irreversible capacity can be suppressed, and uniform electrode application is possible when the electrode preparation step by application is included.
The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by weight aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This can be performed using a meter (LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.

<Raman R value, Raman half width>
The Raman R value of the carbonaceous material is a value measured using an argon ion laser Raman spectrum method, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1.5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.
Further, the Raman half-width in the vicinity of 1580 cm ^{−1 of the} carbonaceous material is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and usually 100 cm ⁻¹ or less, and 80 cm ⁻¹ or less. Preferably, 60 cm ⁻¹ or less is more preferable, and 40 cm ⁻¹ or less is particularly preferable.

The Raman R value and the Raman half-value width are indices indicating the crystallinity of the surface of the carbonaceous material, but the carbonaceous material has an appropriate crystallinity from the viewpoint of chemical stability, while the interlayer in which Li enters by charge / discharge. It is preferable that the crystallinity is such that it does not disappear. In the case where the density of the negative electrode is increased by press after applying to the current collector, it is preferable to take account of this because crystals tend to be oriented in a direction parallel to the electrode plate.
When the Raman R value or the Raman half-value width is in the above range, the reaction between the carbonaceous material and the nonaqueous electrolytic solution can be suppressed, and the deterioration of the load characteristics due to the disappearance of the site can be suppressed.

The measurement of the Raman spectrum, using a Raman spectrometer (manufactured by JASCO Corporation Raman spectrometer), the sample is naturally dropped into the measurement cell and filled, and while irradiating the sample surface in the cell with argon ion laser light, This is done by rotating the cell in a plane perpendicular to the laser beam. The resulting Raman spectrum, the intensity IA of a peak PA around 1580 cm ^-1, and measuring the intensity IB of the peak PB around 1360 cm ^-1, and calculates the intensity ratio R (R = IB / IA) . The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of the present invention. Further, the half width of the peak PA near 1580 cm ⁻¹ of the obtained Raman spectrum is measured, and this is defined as the Raman half width of the carbonaceous material of the present invention.

Moreover, said Raman measurement conditions are as follows.
Argon ion laser wavelength: 514.5nm
・ Laser power on the sample: 15-25mW
・ Resolution: 10-20cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
・ Raman R value, Raman half width analysis: Background processing
-Smoothing processing: Simple average, 5 points of convolution

<BET specific surface area>
BET specific surface area of the carbonaceous material is a value of the measured specific surface area using the BET method is usually 0.1 m ² · ^{g -1} or more, 0.7 m ² · ^{g -1} or more, 1. more preferably 0m2 · ^{g -1} or more, particularly preferably 1.5 m ² · ^{g -1} or more, generally not more than 100 m ² · ^{g -1,} preferably ^{25 m} 2 · ^{g -1} or less, ^{15 m} 2 · g ⁻¹ or less is more preferable, and 10 m ² · g ⁻¹ or less is particularly preferable.

When the value of the BET specific surface area is in the above range, precipitation of lithium on the electrode surface can be suppressed, while gas generation due to reaction with the non-aqueous electrolyte can be suppressed.
The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the carbonaceous material of the present invention.

<Circularity>
When the circularity is measured as the degree of the sphere of the carbonaceous material, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”, and is theoretical when the circularity is 1. Become a true sphere. The circularity of the particles having a particle size of 3 to 40 μm in the range of the carbonaceous material is desirably closer to 1, and is preferably 0.1 or more, more preferably 0.5 or more, and more preferably 0.8 or more, 0.85 or more is more preferable, and 0.9 or more is particularly preferable.
The greater the degree of circularity of the carbonaceous material, the better the filling property and the resistance between particles, so that the high current density charge / discharge characteristics are improved. Therefore, it is preferable that the circularity is as high as the above range.

  The circularity is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity determined by the measurement is defined as the circularity of the carbonaceous material of the present invention.

  The method for improving the circularity is not particularly limited, but a sphere-shaped sphere is preferable because the shape of the interparticle void when the electrode body is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, a mechanical / physical processing method of granulating a plurality of fine particles by the binder or the adhesive force of the particles themselves, etc. Is mentioned.

<Tap density>
The tap density of the carbonaceous material is usually 0.1 g · cm ⁻³ or more, and 0.5 g · cm ^−3.
The above is preferable, 0.7 g · cm ⁻³ or more is more preferable, 1 g · cm ⁻³ or more is particularly preferable, 2 g · cm ⁻³ or less is preferable, 1.8 g · cm ⁻³ or less is more preferable, 1 It is particularly preferably not more than .6 g · cm ⁻³ . When the tap density is in the above range, battery capacity can be ensured and increase in resistance between particles can be suppressed.

  The tap density is measured by passing a sieve having a mesh opening of 300 μm, dropping the sample onto a 20 cm 3 tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring instrument (for example, a tap manufactured by Seishin Enterprise Co., Ltd.). Using a denser, tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the mass of the sample. The tap density calculated by the measurement is defined as the tap density of the carbonaceous material of the present invention.

<Orientation ratio>
The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is in the above range, excellent high-density charge / discharge characteristics can be ensured. The upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.

The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. Set the molding obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN · m ^{-2 so} that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material of the present invention.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degree Light receiving slit = 0.15 mm
Scattering slit = 0.5 degree / measurement range and step angle / measurement time:
(110) plane: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds

<Aspect ratio (powder)>
The aspect ratio (major axis / minor axis) of the carbonaceous material of the negative electrode active material is usually 0.05 or more, preferably 0.07 or more, more preferably 0.1 or more, particularly preferably 0.14 or more, and usually It is 20 or less, preferably 15 or less, more preferably 10 or less, and particularly preferably 7 or less.

If the aspect ratio is too small or too large, the particle shape becomes flat or needle-like, so it tends to be oriented parallel to the current collector in the electrode, and expansion due to Li insertion is in one direction. Tends to occur and the cycle characteristics tend to deteriorate.
On the other hand, if the aspect ratio is in the above range, when the electrode density is increased to increase the capacity, the carbonaceous material becomes a shape close to a sphere or a cube, and the carbonaceous material is not easily crushed. It is preferable because peeling of the resin hardly occurs and cycle characteristics are improved.

Furthermore, the voids between carbonaceous materials are likely to be large, Li diffusion between particles is accelerated, and an improvement in rate characteristics can be expected. Furthermore, since the carbonaceous material is not easily crushed, it is difficult for the carbonaceous material to be oriented in the negative electrode, the expansion of the electrode accompanying charging / discharging can be suppressed, and the conductive path between the active materials is maintained, thereby improving cycle characteristics. Therefore, it is preferable.
In addition, since the expansion of the electrode can be suppressed, it is easy to secure the space inside the battery, and even if a small amount of gas is generated due to oxidative decomposition, there is a space inside the battery, so there is little increase in internal pressure, and it is difficult for the battery to expand. preferable.

  The aspect ratio is measured by magnifying and observing the carbonaceous material particles with a scanning electron microscope. Carbonaceous material particles when three-dimensional observation is performed by selecting arbitrary 50 graphite particles fixed to the end face of a metal having a thickness of 50 μm or less and rotating and tilting the stage on which the sample is fixed. The longest diameter A and the shortest diameter B orthogonal thereto are measured, and the average value of A / B is obtained. The aspect ratio (A / B) obtained by the measurement is defined as the aspect ratio of the carbonaceous material of the present invention.

  The method for obtaining the spheroidized graphite particles having an aspect ratio in the above range is not particularly limited. For example, the graphite particles are repeatedly subjected to mechanical action such as compression, friction, shearing force including the interaction of particles mainly with impact force. It is preferable to use an apparatus given in the above. Specifically, it has a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, shearing force, etc. is applied to the carbon material introduced inside. It is preferable to use an apparatus that performs surface treatment. Moreover, it is preferable to have a mechanism that repeatedly gives a mechanical action by circulating a carbon material, or a mechanism that does not have a circulation mechanism but connects a plurality of apparatuses. As an example of a preferable apparatus, there can be mentioned a hybridization system manufactured by Nara Machinery Co., Ltd.

<Mixed secondary material>
The sub-material mixing means that two or more types of carbonaceous materials having different properties are contained in the negative electrode and / or the negative electrode active material. The properties referred to here are selected from the group consisting of X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. Shows more than one characteristic.

As a particularly preferred example of mixing these secondary materials, the volume-based particle size distribution is not symmetrical when centered on the median diameter, containing two or more carbonaceous materials having different Raman R values, And X-ray parameters are different.
As an example of the effect of the admixture of secondary materials, carbonaceous material such as graphite (natural graphite, artificial graphite), carbon black such as acetylene black, and amorphous carbon such as needle coke is contained as a conductive material. Reducing electrical resistance.

  When mixing a conductive material as a secondary material mixture, one type may be mixed alone, or two or more types may be mixed in any combination and ratio. The mixing ratio of the conductive material to the carbonaceous material is usually 0.1% by mass or more and 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 45% by mass or less. Yes, 40 mass% or less is preferable. When the mixing ratio is in the above range, the effect of reducing electric resistance can be secured and an increase in initial irreversible capacity can be suppressed.

<Surface oxygen content (abbreviated as O / C value)>
The surface oxygen content in the present invention can be measured using X-ray photoelectron spectroscopy (XPS).
The surface oxygen content O / C value is measured using an X-ray photoelectron spectrometer as an X-ray photoelectron spectroscopy measurement, the measurement object is placed on a sample stage so that the surface is flat, and Kα ray of aluminum is used as an X-ray source. The spectra of C1s (280 to 300 eV) and O1s (525 to 545 eV) are measured by multiplex measurement. The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and O1s spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and O, respectively. The obtained O / C atomic concentration ratio O / C (O atom concentration / C atom concentration) × 100 is defined as the oxygen-containing functional group amount O / C value of the carbon material.

  The O / C value is 0.8 atom% or more, preferably 1.0 atom% or more, more preferably 1.5 atom% or more, and further preferably 3.0 atom% or more. The upper limit is usually 15 atom% or less, preferably 10% or less, more preferably 7.5 atom% or less. When the O / C value is in the above range, the effects of the present invention can be sufficiently achieved, and the reactivity with the electrolytic solution is increased, thereby preventing charge / discharge efficiency from decreasing and gas generation from increasing.

<Control of oxygen-containing functional groups>
Usually, an arbitrary amount of oxygen functional groups are present on the surface of the carbonaceous material depending on the type and production history, but the carbonaceous material used in the present invention may positively introduce oxygen functional groups.
As a method for introducing an oxygen-containing functional group onto the surface of the carbonaceous material, a known method or any newly invented method can be used. For example, oxidation with nitric acid, permanganate, dichromate, hypochlorite, ammonium persulfate, hydrogen peroxide, ozone and other oxidizing agents, treatment with coupling agents such as silane compounds, polymer grafting In addition to known methods such as plasma treatment, newly developed methods can also be used, and these methods may be combined.

Other oxygen-containing functional group introduction methods include mechanochemical treatment in a liquid or gas atmosphere containing oxygen atoms. Use of this method is preferable because the amount of oxygen functional group introduced can be easily controlled depending on the atmosphere and processing conditions.
The apparatus to be used is not particularly limited as long as it is an apparatus that can simultaneously apply a compressive force and a shearing force to an object to be processed. As such an apparatus, for example, a kneader such as a pressure kneader or two rolls, a rotating ball mill, a hybridization system (manufactured by Nara Machinery Co., Ltd.), Mechano Micros (manufactured by Nara Machinery Co., Ltd.), etc. are used. can do.

The ambient atmosphere of the object to be processed is not particularly specified as long as a functional group can be imparted to the surface at the time of processing, but a liquid or gas containing oxygen atoms is desirable. If the treatment itself is about 20 mol% oxygen, which is an atmospheric composition, functional groups are sufficiently imparted, but these effects cannot be expected in a nitrogen atmosphere.
The oxygen concentration is usually 0.1 mol% or more, preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 20 mol% or more, and usually 80 mol% or less, preferably 50 mol% or less, more preferably Is 40 mol% or less. If the partial pressure of oxygen applied is too low, functional grouping will be insufficient and the effect of improving cycle characteristics will tend to be difficult to obtain. .

In addition to the atmospheric composition, monodentate alcohols typified by water, methanol, ethanol, isopropyl alcohol, multidentate alcohols typified by ethylene glycol and propylene glycol, as well as ethers and ester compounds are preferably used. it can. As the gas, ozone, carbon monoxide, SO _x , NO _{x and the} like can be preferably used.
Conversely, the oxygen functional group amount may be controlled by a method of desorbing the functional group. For example, when calcination is performed in an atmosphere containing an inert gas or a reducing gas, the oxygen functional group can be gasified and easily desorbed.

<Configuration and production method of negative electrode>
Any known method can be used for producing the electrode as long as the effects of the present invention are not significantly impaired. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector described later, dried, and then pressed. can do.

(Current collector)
As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the negative electrode current collector include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.
In addition, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, or the like when the current collector is a metal material. Among these, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable.
The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and is usually 100 μm or less, preferably 50 μm or less. This is because if the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be too low, and conversely if it is too thin, handling may be difficult.

(Thickness ratio between current collector and negative electrode active material layer)
The ratio of the thickness of the current collector to the negative electrode active material layer is not particularly limited, but the value of “(the thickness of the negative electrode active material layer on one side immediately before the nonaqueous electrolyte injection) / (thickness of the current collector)” However, 150 or less is preferable, 20 or less is more preferable, 10 or less is particularly preferable, 0.1 or more is preferable, 0.4 or more is further preferable, and 1 or more is particularly preferable. If the ratio of the thickness of the current collector to the negative electrode active material layer is too large, the current collector tends to generate heat due to Joule heat during high current density charge / discharge. In addition, if the ratio of the thickness of the current collector to the negative electrode active material layer is too small, the volume ratio of the current collector to the negative electrode active material tends to increase, and the battery capacity tends to decrease.

(Binder)
The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used in manufacturing the electrode.
Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate , Soft resinous polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. And a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions). These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  Moreover, when the functional group which couple | bonds with an isocyanate group exists in the molecule | numerator of a binder, the physical strength of the film | membrane component induced | guided | derived from an isocyanate compound will increase, and a cycling characteristic may be improved more. Preferred functional groups include amino groups, hydroxyl groups, and carboxyl groups. Such a binder is blended in a range that does not affect the physical properties and coating properties of the slurry.

The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, 0.5% by mass
The above is more preferable, 0.6% by mass or more is particularly preferable, 20% by mass or less is preferable, 15% by mass or less is more preferable, 10% by mass or less is further preferable, and 8% by mass or less is particularly preferable. When the ratio of the binder to the negative electrode active material is too large, the binder ratio in which the binder amount does not contribute to the battery capacity increases, and the battery capacity tends to decrease. Moreover, when the ratio of a binder is too small, there exists a tendency which causes the strength reduction of a negative electrode.

  In particular, when a rubbery polymer typified by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0 .6% by mass or more is more preferable, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. It is preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

(Slurry forming solvent)
The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N- Examples include dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.
In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and slurry it using a latex such as SBR. In addition, these solvents may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

(Thickener)
A thickener is normally used in order to adjust the viscosity of the slurry at the time of producing a negative electrode active material layer. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  Further, when using a thickener, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Moreover, it is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is more preferable. When the ratio of the thickener to the negative electrode active material is too small, applicability tends to be remarkably lowered. Moreover, when there are too many ratios of a thickener, the ratio of the negative electrode active material which occupies for a negative electrode active material layer will fall, and there exists a tendency for the capacity | capacitance of a battery to fall and the resistance between negative electrode active materials to increase.

(Electrode density)
The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g · cm ⁻³ or more. but more preferably, particularly preferably 1.3 g · ^{cm -3} or more, preferably 2.2 g · ^{cm -3} or less, more preferably 2.1 g · ^{cm -3} or less, 2.0 g · ^{cm -3} or less Further preferred is 1.9 g · cm ⁻³ or less. If the density of the negative electrode active material present on the current collector is too large, the negative electrode active material particles will be destroyed, increasing the initial irreversible capacity, and the non-aqueous electrolyte solution near the current collector / negative electrode active material interface. There is a tendency for high current density charge / discharge characteristics to deteriorate due to a decrease in permeability. On the other hand, if the density is too small, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume tends to decrease.

(Thickness of negative electrode plate)
The thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited. Above, preferably 20 μm or more, more preferably 30 μm or more, and usually 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

(Surface coating of negative electrode plate)
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said negative electrode plate. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

2. Non-aqueous electrolyte 2-1. Electrolyte <Lithium salt>
As the electrolyte, a lithium salt is usually used. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used. Specific examples include the following.

For _{example, LiPF 6, LiBF 4, LiClO} 4, LiAlF 4, LiSbF 6, inorganic lithium salts LiTaF 6, LiWF ₇ and the like;
Lithium tungstates such as LiWOF ₅ ;
HCO ₂ Li, CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF ₃ CF ₂ CO ₂ Li, CF ₃ CF ₂ CF ₂ Carboxylic acid lithium salts such as CO ₂ Li, CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ Li;
_{CH 3 SO 3 Li, CH 2} FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3 CF 2 CF 2 SO 3 Li, CF 3 CF 2 CF 2 CF 2 Sulfonic acid lithium salts such as SO ₃ Li;
LiN (FCO) ₂ , LiN (FCO) (FSO ₂ ), LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Lithium imide salts such as lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) ;
Lithium metide salts such as LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ ;
In addition, LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₃ CF ₃ , LiBF ₃ C _{2 F 5, LiBF 3 C 3} F 7, LiBF 2 (CF 3) 2, LiBF 2 (C 2 F 5) 2, LiBF 2 (CF 3 SO 2) 2, LiBF 2 (C 2 F 5 SO 2) 2 Fluorine-containing organic lithium salts such as
And dicarboxylic acid complex lithium salts such as lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, and the like.

Among them, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiTaF ₆ , LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) _3, etc. are output characteristics, high rate charge / discharge characteristics, high temperature storage characteristics, cycle This is particularly preferable from the viewpoint of improving the characteristics and the like.

  The concentration of the lithium salt in the nonaqueous electrolytic solution is not particularly limited as long as the effects of the present invention are not impaired, but the electric conductivity of the electrolytic solution is in a good range, and good battery performance is ensured. Therefore, the total molar concentration of the lithium salt in the non-aqueous electrolyte is usually 0.3 mol / L or more, preferably 0.4 mol / L or more, more preferably 0.5 mol / L or more, and usually 3 mol / L. L or less, preferably 2.5 mol / L or less, more preferably 2.0 mol / L or less. When the total molar concentration of the lithium salt is within the above range, effects such as low temperature characteristics, cycle characteristics, and high temperature characteristics are improved. In addition, the electric conductivity of the electrolytic solution is sufficient, and the decrease in electric conductivity due to the increase in viscosity and the decrease in battery performance are prevented.

Moreover, you may use the said lithium salt in arbitrary combinations.
2-2. Solvent As the non-aqueous solvent, saturated cyclic and chain carbonates, carbonates having at least one fluorine atom, cyclic and chain carboxylic acid esters, ether compounds, sulfone compounds, and the like can be used. These nonaqueous solvents may be used in any combination.

<Saturated cyclic carbonate>
Examples of the saturated cyclic carbonate include those having an alkylene group having 2 to 4 carbon atoms. Specifically, examples of the saturated cyclic carbonate having 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

A saturated cyclic carbonate may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
The blending amount of the saturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. However, the lower limit of the blending amount when one kind is used alone is usually in 100% by volume of the non-aqueous solvent. 5 volume% or more, preferably 10 volume% or more, and usually 95 volume% or less, preferably 90 volume% or less, more preferably 85 volume% or less. The blending amount of the saturated cyclic carbonate is within the above range, avoiding a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte, and a large current discharge characteristic of the non-aqueous electrolyte battery, stability to the negative electrode It becomes easy to make the cycle characteristics within a good range. In addition, the viscosity of the non-aqueous electrolyte solution is set in an appropriate range, and the decrease in ionic conductivity is suppressed, and as a result, the load characteristics of the non-aqueous electrolyte battery are easily set in a favorable range.

<Chain carbonate>
As a chain carbonate, a C3-C7 thing is preferable.
Specifically, as the chain carbonate having 3 to 7 carbon atoms, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, Examples include n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate.

Among them, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferable. is there.
A chain carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The amount of the chain carbonate is usually 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and usually 90% by volume or less, preferably 85% by volume in 100% by volume of the non-aqueous solvent. It is as follows. When the blended amount of the chain carbonate is in the above range, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, the decrease in ionic conductivity is suppressed, and the large current discharge characteristics of the non-aqueous electrolyte battery are thus in a good range. And it will be easier. Further, it is easy to avoid a decrease in electrical conductivity due to a decrease in dielectric constant of the nonaqueous electrolyte solution, and to make the large current discharge characteristics of the nonaqueous electrolyte battery within a favorable range.

<Carbonates having fluorine atoms>
As carbonates having fluorine atoms, both saturated chain carbonates having fluorine atoms (hereinafter also referred to as fluorinated saturated chain carbonates) and saturated cyclic carbonates having fluorine atoms (hereinafter also referred to as fluorinated saturated cyclic carbonates) are used. Can be used.

  The number of fluorine atoms in the fluorinated saturated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated saturated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or may be bonded to different carbons. Examples of the fluorinated saturated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.

Examples of the fluorinated dimethyl carbonate derivative include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoromethyl) carbonate, and the like.
Fluorinated ethyl methyl carbonate derivatives include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2-trimethyl Examples include fluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.

  Fluorinated diethyl carbonate derivatives include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2-trifluoro). Ethyl) carbonate, 2,2-difluoroethyl-2′-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2′-fluoroethyl carbonate, 2,2, Examples include 2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and the like.

As the fluorinated saturated chain carbonate, 2,2,2-trifluoroethyl methyl carbonate and bis (2,2,2-trifluoroethyl) carbonate are particularly preferable.
Moreover, a fluorinated saturated chain carbonate may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
Examples of the fluorinated saturated cyclic carbonate include derivatives of saturated cyclic carbonates having an alkylene group having 2 to 6 carbon atoms, such as ethylene carbonate derivatives. Examples of the ethylene carbonate derivative include fluorinated products of ethylene carbonate or ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms), and particularly those having 1 to 8 fluorine atoms. Is preferred.

  Specifically, monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4- Fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethyl Le ethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate.

Examples of the fluorinated saturated cyclic carbonate include monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, and 4,
Particularly preferred is at least one selected from the group consisting of 5-difluoro-4,5-dimethylethylene carbonate. These provide high ionic conductivity and preferably form an interface protective coating.

Moreover, a fluorinated saturated cyclic carbonate may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
The blending amount in the case of using a carbonate having at least one fluorine atom is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass in 100% by mass of the non-aqueous electrolyte solution. In addition, it is usually 90% by mass or less, preferably 85% by mass or less, and more preferably 80% by mass or less.

  In particular, when a carbonate having at least one fluorine atom is used as a solvent, the blending amount is usually 5% by mass or more, preferably 7% by mass or more, more preferably 10% by mass or more in 100% by mass of the non-aqueous electrolyte. Moreover, it is 90 mass% or less normally, Preferably it is 70 mass% or less, More preferably, it is 50 mass% or less. By being in the above range, when the battery is operated at a high voltage, the secondary decomposition reaction of the non-aqueous electrolyte can be suppressed, the battery durability can be enhanced, and the electrical conductivity of the non-aqueous electrolyte is extremely low. Decline can be prevented. When used as a solvent, a fluorinated saturated carbonate is preferable among carbonates having at least one fluorine atom.

  On the other hand, the blending amount in the case of using a carbonate having at least one fluorine atom as an auxiliary agent is usually 0.01% by mass or more, preferably 0.1% by mass or more, in 100% by mass of the non-aqueous electrolyte. Preferably it is 0.2 mass% or more, and is 5 mass% or less normally, Preferably it is 4 mass% or less, More preferably, it is 3 mass% or less. By being in the above range, durability can be improved without excessively increasing the charge transfer resistance, so that charge / discharge durability at a high current density can be improved.

Even when two or more carbonates having at least one fluorine atom are used in combination, it is preferable to adjust within the above range.
In addition, although the case where the carbonate having at least one fluorine atom is used as a solvent and an auxiliary was described, in the actual use, there is no clear boundary line in the solvent or the auxiliary, and the non-limiting ratio is An aqueous electrolyte solution can be prepared.

<Cyclic carboxylic acid ester>
Examples of the cyclic carboxylic acid ester include those having 3 to 12 total carbon atoms in the structural formula. Specific examples include gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone, and the like. Among these, gamma butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

A cyclic carboxylic acid ester may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
The compounding amount of the cyclic carboxylic acid ester is usually 5% by volume or more, preferably 10% by volume or more, and usually 50% by volume or less, preferably 40% by volume or less in 100% by volume of the non-aqueous solvent. By being in the said range, it becomes easy to improve the electrical conductivity of a non-aqueous electrolyte solution, and to improve the large current discharge characteristic of a non-aqueous electrolyte battery. In addition, the viscosity of the non-aqueous electrolyte solution is set in an appropriate range, the decrease in electrical conductivity is avoided, the increase in negative electrode resistance is suppressed, and the large current discharge characteristics of the non-aqueous electrolyte secondary battery are easily set in a favorable range. .

<Chain carboxylic acid ester>
Examples of the chain carboxylic acid ester include those having 3 to 7 carbon atoms in the structural formula. Specifically, methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, acetic acid-n-butyl, isobutyl acetate, acetic acid-t-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, Isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyric acid-n- Examples include propyl and isopropyl isobutyrate.

Among them, methyl acetate, ethyl acetate, acetate-n-propyl, acetate-n-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. It is preferable from the viewpoint of improvement of ionic conductivity.
A chain carboxylic acid ester may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.

  The amount of the chain carboxylic acid ester is usually 10% by volume or more, preferably 15% by volume or more, and usually 60% by volume or less, preferably 50% by volume or less in 100% by volume of the non-aqueous solvent. By being in the said range, it becomes easy to improve the electrical conductivity of a non-aqueous electrolyte solution, and to improve the large current discharge characteristic of a non-aqueous electrolyte battery. Moreover, increase in negative electrode resistance is suppressed, and the large current discharge characteristics and cycle characteristics of the non-aqueous electrolyte battery are easily set in a favorable range.

<Ether compound>
As the ether compound, a chain ether having 3 to 10 carbon atoms in which part of hydrogen may be substituted with fluorine, and a cyclic ether having 3 to 6 carbon atoms are preferable.
Examples of the chain ether having 3 to 10 carbon atoms include diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2,2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2 -Trifluoroethyl) ether, (2-fluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl) (1,1,2,2-tetrafluoro) Ethyl) ether, ethyl-n-propyl ether, ethyl (3-fluoro-n-propyl) ether, ethyl (3,3,3-trifluoro-n-propyl) Ether, ethyl (2,2,3,3-tetrafluoro-n-propyl) ether, ethyl (2,2,3,3,3-pentafluoro-n-propyl) ether, 2-fluoroethyl-n-propyl Ether, (2-fluoroethyl) (3-fluoro-n-propyl) ether, (2-fluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (2-fluoroethyl) (2, 2,3,3-tetrafluoro-n-propyl) ether, (2-fluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, 2,2,2-trifluoroethyl -N-propyl ether, (2,2,2-trifluoroethyl) (3-fluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (3,3,3-trifluoro Olo-n-propyl) ether, (2,2,2-trifluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (2 , 2,3,3,3-pentafluoro-n-propyl) ether, 1,1,2,2-tetrafluoroethyl-n-propyl ether, (1,1,2,2-tetrafluoroethyl) (3 -Fluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl) ) (2,2,3,3-tetrafluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) Ether, di-n-propyl Ether, (n-propyl) (3-fluoro-n-propyl) ether, (n-propyl) (3,3,3-trifluoro-n-propyl) ether, (n-propyl) (2,2,3 , 3-tetrafluoro-n-propyl) ether, (n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (3-fluoro-n-propyl) ether, ( 3-Fluoro-n-propyl) (3,3,3-trifluoro-n-propyl) ether, (3-fluoro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether , (3-fluoro-n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (3,3,3-trifluoro-n-propyl) ether, (3 3,3-triflu (Ro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl) (2,2,3,3,3-penta Fluoro-n-propyl) ether, di (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-propyl) (2,2,3 3,3-pentafluoro-n-propyl) ether, di (2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, methoxy (2 -Fluoroethoxy) methane, methoxy (2,2,2-trifluoroethoxy) methanemethoxy (1,1,2,2-tetrafluoroethoxy) methane, diethoxymethane, ethoxy (2-fur Roethoxy) methane, ethoxy (2,2,2-trifluoroethoxy) methane, ethoxy (1,1,2,2-tetrafluoroethoxy) methane, di (2-fluoroethoxy) methane, (2-fluoroethoxy) ( 2,2,2-trifluoroethoxy) methane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methanedi (2,2,2-trifluoroethoxy) methane, (2,2, 2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methane, di (1,1,2,2-tetrafluoroethoxy) methane, dimethoxyethane, methoxyethoxyethane, methoxy (2-fluoroethoxy) ) Ethane, methoxy (2,2,2-trifluoroethoxy) ethane, methoxy (1,1,2,2-tetrafluoroeth) Xyl) ethane, diethoxyethane, ethoxy (2-fluoroethoxy) ethane, ethoxy (2,2,2-trifluoroethoxy) ethane, ethoxy (1,1,2,2-tetrafluoroethoxy) ethane, di (2 -Fluoroethoxy) ethane, (2-fluoroethoxy) (2,2,2-trifluoroethoxy) ethane, (2-fluoroethoxy) (1,1,
2,2-tetrafluoroethoxy) ethane, di (2,2,2-trifluoroethoxy) ethane, (2,2,2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, Examples include di (1,1,2,2-tetrafluoroethoxy) ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

Examples of the cyclic ether having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1 , 4-dioxane and the like, and fluorinated compounds thereof.
Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability to lithium ions and improve ion dissociation. Of these, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are preferable because they have low viscosity and give high ionic conductivity.

An ether type compound may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
The compounding amount of the ether compound is usually 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and usually 70% by volume or less, preferably 60% by volume in 100% by volume of the non-aqueous solvent. Hereinafter, it is more preferably 50% by volume or less. By being within the above range, it is easy to ensure the improvement effect of the lithium ion dissociation degree of the chain ether and the improvement of the ionic conductivity derived from the decrease in the viscosity. It is easy to avoid a situation where the capacity is reduced due to co-insertion with ions.

<Sulfone compounds>
As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable. The number of sulfonyl groups in one molecule is preferably 1 or 2. Examples of the cyclic sulfone include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones that are monosulfone compounds; trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones that are disulfone compounds. Among these, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.
As sulfolanes, sulfolane and / or sulfolane derivatives (hereinafter also referred to as sulfolanes including sulfolane) are preferable. As the sulfolane derivative, one in which one or more hydrogen atoms bonded to the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group is preferable.

Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methyl Sulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoro Methyl sulfolane, 2- Trifluoromethylsulfolane, 3-trifluoromethylsulfolane, 2-fluoro-3- (trifluoromethyl) sulfolane, 3-fluoro-3- (trifluoromethyl) sulfolane, 4-fluoro-3- (trifluoromethyl) sulfolane , 5-fluoro-3- (trifluoromethyl) sulfolane and the like are preferable in terms of high ionic conductivity and high input / output.

  As the chain sulfone, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n- Butyl methyl sulfone, n-butyl ethyl sulfone, t-butyl methyl sulfone, t-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, Trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trif Oromethylsulfone, perfluoroethylmethylsulfone, ethyltrifluoroethylsulfone, ethylpentafluoroethylsulfone, di (trifluoroethyl) sulfone, perfluorodiethylsulfone, fluoromethyl-n-propylsulfone, difluoromethyl-n-propylsulfone Trifluoromethyl-n-propylsulfone, fluoromethylisopropylsulfone, difluoromethylisopropylsulfone, trifluoromethylisopropylsulfone, trifluoroethyl-n-propylsulfone, trifluoroethylisopropylsulfone, pentafluoroethyl-n-propylsulfone, Pentafluoroethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone Emissions, pentafluoroethyl -n- butyl sulfone, pentafluoroethyl -t- butyl sulfone, and the like.

  Among them, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone , Monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoro Ethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone, tri Ruoroechiru -n- butyl sulfone, trifluoroethyl -t- butyl sulfone, trifluoromethyl -n- butyl sulfone, trifluoromethyl -t- butyl sulfone is preferred because a higher high output ionic conductivity.

A sulfone type compound may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
The compounding amount of the sulfone compound is usually 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and usually 40% by volume or less, preferably 35% in 100% by volume of the non-aqueous solvent. Volume% or less, More preferably, it is 30 volume% or less. By being in the above-mentioned range, it is easy to obtain durability improvement effects such as cycle characteristics and storage characteristics, and the viscosity of the non-aqueous electrolyte solution can be set to an appropriate range to avoid a decrease in electrical conductivity. When charging / discharging the non-aqueous electrolyte battery at a high current density, it is easy to avoid a situation in which the charge / discharge capacity retention rate decreases.

<Compound having an isocyanate group>
The compound having an isocyanate group in the present invention (hereinafter appropriately referred to as “isocyanate compound”) is not particularly limited as long as it is a compound having at least one isocyanate group in the molecule.
As an isocyanate compound, what is represented by following General formula (1) is preferable.

In the above formula, A represents a hydrogen atom, a halogen atom, a vinyl group, an isocyanate group, or a C ₁ to C ₂₀ aliphatic hydrocarbon group (which may have a hetero atom) or C _{6 to} C _20. Represents an aromatic hydrocarbon group (which may have a hetero atom). B is an oxygen atom, S ₂ O ₂ , OSO ₂ , SO 3, OCO, COO, or a C ₁ to C ₂₀ aliphatic hydrocarbon group (which may have a hetero atom), or C _{6 to} C _{2. 0 represents} an aromatic hydrocarbon group (which may have a hetero atom).

Examples include the following compounds.
Diisocyanato sulfone, diisocyanato ether, trifluoromethane isocyanate, pentafluoroethane isocyanate, trifluoromethanesulfonyl isocyanate, pentafluoroethanesulfonyl isocyanate, benzenesulfonyl isocyanate, p-toluenesulfonyl isocyanate, 4-fluorobenzenesulfonyl isocyanate, 1,3 -Diisocyanatopropane, 1,3-diisocyanatopropene, 1,3-diisocyanato-2-fluoropropane, 1,4-diisocyanatobutane, 1,4-diisocyanato-2-butene, 1,4-diisocyanato -2-fluorobutane, 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanatopentane, 1,5-diisocyanato-2-pentene, 1, -Diisocyanato-2-methylpentane, 1,6-diisocyanatohexane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1, 6-diisocyanato-3,4-difluorohexane, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,7-diisocyanatoheptane, 1,8- Diisocyanatooctane, 1,9-diisocyanatononane, 1,10-diisocyanatodecane, 1,12-diisocyanatodecane, 1-isocyanatoethylene, isocyanatomethane, 1-isocyanatoethane, 1- Isocyanato-2-methoxyethane, 3-isocyanato-1-propene, isocyanato Ropropane, 2-isocyanatopropane, 1-isocyanatopropane, 1-isocyanato-3-methoxypropane, 1-isocyanato-3-ethoxypropane, 2-isocyanato-2-methylpropane, 1-isocyanatobutane, 2-isocyanate Natobutane, 1-isocyanato-4-methoxybutane, 1-isocyanato-4-ethoxybutane, methyl isosinatoformate, isanatocyclopentane, 1-isocyanatopentane, 1-isocyanato-5-methoxypentane, 1-isocyanato -5-ethoxypentane, 2- (isocyanatomethyl) furan, isocyanatocyclohexane, 1-isocyanatohexane, 1-isocyanato-6-methoxyhexane, 1-isocyanato-6-ethoxyhexane, ethyl isocyanatoacetate, Socyanatocyclopentane, isocyanatomethyl (cyclohexane), 1-isocyanatoheptane, ethyl 3-isocyanatopropanoate, isocyanatocyclooctane, 2-isocyanatoethyl-2-methyl acrylate, 1-isocyanatooctane, 2 −
Isocyanato-2,4,4-trimethylpentane, butylisocyanatoacetate, ethyl 4-isocyanatobutanoate, 1-isocyanatononane, 1-isocyanatoadamantane, 1-isocyanatodecane, ethyl 6-isocyanatohexano 1,2-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1,2-diisocyanatocyclohexane, 1,3 -Diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-1,1'-diisocyanate, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclohexylmethane-4, 4'-diisocyanate, isophorone diisocyanate, 1,6,11-triisocyanatoundecane, 4-isocyanatomethyl-1,8
-Octamethylene diisocyanate, 1,3,5-triisocyanate methylbenzene, bicyclo [2.2.1] heptane-2,5-diylbis (methyl = isocyanate), bicyclo [2.2.1] heptane-2,6 -Diylbis (methyl = isocyanate), 1,3,5-tris (6-isocyanatohex-1-yl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 4- (isocyanatomethyl) octamethylene = diisocyanate, 1-isocyanatoundecane, diisocyanatobenzene, toluene diisocyanate, xylene diisocyanate, tolylene diisocyanate, ethyl diisocyanatobenzene, trimethyldiisocyanatobenzene, diisocyanatonaphthalene, Diisocyanatobiphenyl, di E methane diisocyanate, 2,2-bis (isocyanatomethyl) hexafluoropropane, methoxycarbonyl isocyanate, methoxy sulfonyl isocyanates, allyl isocyanate, vinyl isocyanate.

Among them, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, 1,8-diisocyanatooctane, 1,9 -Diisocyanatononane, 1,10-diisocyanatodecane, toluene diisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane-1,1'-diisocyanate, dicyclohexylmethane- 2,2′-diisocyanate, dicyclohexylmethane-3,3′-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, isophorone diisocyanate, 1,6,11-triisocyanatoundecane, 4-isocyanatomethyl-1,8 -Octameth Diisocyanate, 1,3,5-triisocyanate methylbenzene, bicyclo [2.2.1] heptane-2,5-diylbis (methyl = isocyanate), bicyclo [2.2.1] heptane-2,6-diylbis (Methyl = isocyanate), 1,3,5-tris (6-isocyanatohex-1-yl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2, 4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 4- (isocyanatomethyl) octamethylene diisocyanate, methoxycarbonyl isocyanate, and methoxysulfonyl isocyanate are preferred.

Of these, 1,6-diisocyanatohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate , Methoxycarbonyl isocyanate, and methoxysulfonyl isocyanate are particularly preferable.
The reason why the above compound is preferable is that the raw materials are industrially easily available, the production cost of the electrolytic solution is kept low, the isocyanate compound is easily dissolved in the non-aqueous electrolytic solution, and the electrode surface The point that the reactivity is optimal is mentioned.

Moreover, the diisocyanate compound which has a structure shown by following formula (2) is preferable since the tolerance with respect to the physical deformation | transformation of the expansion | swelling / contraction of an electrode accompanying charging / discharging can be improved effectively. This is because chain-like methylene groups are incorporated into the film and / or electrode structure to impart appropriate elasticity to such a structure. Therefore, for this purpose, the length of the methylene group is important. In the formula, x is preferably 4 to 12, and more preferably 4 to 8. Specifically, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, 1,8-diisocyanatooctane, etc. Is mentioned.

  Moreover, the isocyanate compound used for this invention may use the polyisocyanate manufactured by using the diisocyanate compound shown by Formula (2) as a main raw material. From the viewpoint of ease of production, polyisocyanates having one or more skeletons selected from uretdione, oxadiaditrione, biuret, urethane, allophanate and isocyanurate are preferably used. Two or more of each skeleton may be contained in the molecule.

The number average molecular weight of the polyisocyanate is usually 200 or more, preferably 300 or more, and usually 10,000 or less, preferably 5000 or less, more preferably 3000 or less. When the number average molecular weight is in the above range, dissolution in the electrolytic solution tends to be easy.
The average number of functional groups is 2 or more, preferably 3 or more, and is usually 12 or less, preferably 10 or less, more preferably 8 or less. When the average number of functional groups is within the above range, the stability of the film can be increased, and an increase in charge transfer resistance of the positive electrode due to the increase in functional groups is acceptable.

  The isocyanate compound used in the present invention also includes so-called blocked isocyanate, which is blocked with a blocking agent to enhance storage stability. Examples of the blocking agent include alcohols, phenols, organic amines, oximes, and lactams. Specific examples include n-butanol, phenol, tributylamine, diethylethanolamine, methyl ethyl ketoxime, and ε-caprolactam. Etc.

For the purpose of promoting a reaction based on an isocyanate compound and obtaining a higher effect, a metal catalyst such as dibutyltin dilaurate or an amine catalyst such as 1,8-diazabicyclo [5.4.0] undecene-7 is used. Use in combination is also preferred.
The isocyanate compound of this invention may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The concentration of the isocyanate compound in the composition of the non-aqueous electrolyte solution of the present invention is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably Is 0.1% by mass or more, and is usually 5% by mass or less, preferably 3% by mass or less, more preferably 1.5% by mass or less. If it is the said range, while being able to fully improve the chemical and physical stability in a battery, the excessive increase in resistance by film formation can be suppressed.
In addition, a commercially available thing may be used for an isocyanate compound, and when manufacturing, the manufacturing method is not limited, What was manufactured by the well-known method can be used.

<1-4. Auxiliary>
In addition to the above-mentioned electrolyte, non-aqueous solvent, and isocyanate compound, an auxiliary may be appropriately added to the non-aqueous electrolyte of the present invention depending on the purpose. Examples of the auxiliary agent include a cyclic carbonate having an unsaturated bond shown below, an unsaturated cyclic carbonate having a fluorine atom, an overcharge inhibitor, and other auxiliary agents.

(Cyclic carbonate having an unsaturated bond)
The cyclic carbonate having an unsaturated bond (hereinafter sometimes abbreviated as “unsaturated cyclic carbonate”) also has an effect of improving the battery life because it forms a film on the negative electrode surface.
The unsaturated cyclic carbonate is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon double bond and / or a carbon-carbon triple bond, and any unsaturated carbonate can be used. The cyclic carbonate having an aromatic ring is also included in the unsaturated cyclic carbonate.

Examples of the unsaturated cyclic carbonate include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, Catechol carbonates, ethynyl carbonates, propargyl carbonate and the like can be mentioned.
As vinylene carbonates, vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4 , 5-diallyl vinylene carbonate and the like.

  Specific examples of the ethylene carbonate substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5- Vinylethylene carbonate, 4-allyl-5-vinylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl-5-phenylethylene carbonate, allylethylene carbonate, Examples include 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, and the like.

  Among them, particularly preferable unsaturated cyclic carbonates for use in combination with the compound of the present invention include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate. 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl Since ethylene carbonate, 4-allyl-5-vinylethylene carbonate, and ethynyl ethylene carbonate form a stable interface protective film, they are more preferably used.

  The molecular weight of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is usually 50 or more, preferably 80 or more, and usually 250 or less, preferably 150 or less. By being in the said range, it is easy to ensure the solubility of the unsaturated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention is fully easy to be expressed. The molecular weight of the unsaturated cyclic carbonate is not particularly limited as to the method for producing the unsaturated cyclic carbonate, and can be produced by arbitrarily selecting a known method.

  An unsaturated cyclic carbonate may be used individually by 1 type, or may have 2 or more types by arbitrary combinations and ratios. Moreover, the compounding quantity of unsaturated cyclic carbonate is not restrict | limited in particular, As long as the effect of this invention is not impaired remarkably, it is arbitrary. The blending amount of the unsaturated cyclic carbonate is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more in 100% by mass of the non-aqueous electrolyte solution. 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less. Within the above range, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved, and further, the decrease in the discharge capacity retention rate due to the decrease in the high temperature storage characteristics can be suppressed, while the resistance due to excessive film formation is reduced. Increase can be suppressed.

(Fluorinated unsaturated cyclic carbonate)
As the fluorinated cyclic carbonate, it is also preferable to use a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter sometimes abbreviated as “fluorinated unsaturated cyclic carbonate”). The number of fluorine atoms contained in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, the number of fluorine atoms is usually 6 or less, preferably 4 or less, and most preferably 1 or 2 fluorine atoms.

Examples of the fluorinated unsaturated cyclic carbonate include a fluorinated vinylene carbonate derivative, a fluorinated ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon double bond.
Fluorinated vinylene carbonate derivatives include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-5- And vinyl vinylene carbonate.

  Examples of the fluorinated ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon double bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5. -Vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate 4,5-diflu B-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4- Examples thereof include phenylethylene carbonate.

  Among them, particularly preferred fluorinated unsaturated cyclic carbonates for use in combination with the compounds of the present invention include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4- Allyl-5-fluorovinylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4, 4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro- , 5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate are stable. Since an interface protective film is formed, it is used more suitably.

  The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. If it is the said range, it will be easy to ensure the solubility of the fluorinated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed. The production method of the fluorinated unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

A fluorinated unsaturated cyclic carbonate may be used individually by 1 type, and may have 2 or more types by arbitrary combinations and ratios. Moreover, the compounding quantity of a fluorinated unsaturated cyclic carbonate is not restrict | limited in particular, As long as the effect of this invention is not impaired remarkably, it is arbitrary. The blending amount of the fluorinated unsaturated cyclic carbonate is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more in 100% by mass of the non-aqueous electrolyte. Moreover, it is 5 mass% or less normally, Preferably it is 4 mass% or less, More preferably, it is 3 mass% or less. Within the above range, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved, and further, the decrease in the discharge capacity retention rate due to the decrease in the high temperature storage characteristics can be suppressed, while the resistance increase due to excessive film formation Can be suppressed.

(Overcharge prevention agent)
In the non-aqueous electrolyte solution of the present invention, an overcharge inhibitor can be used in order to effectively suppress battery explosion / ignition when the non-aqueous electrolyte secondary battery is in an overcharged state or the like. .
As an overcharge inhibitor, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, Partially fluorinated products of the above aromatic compounds such as o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like And a fluorine-containing anisole compound. Of these, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, terphenyl partially hydrogenated, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. These may be used alone or in combination of two or more. When two or more kinds are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, Using at least one selected from aromatic compounds not containing oxygen, such as t-amylbenzene, and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, and the like is an overcharge prevention property and a high temperature storage property. From the standpoint of balance.

  The amount of the overcharge inhibitor is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The overcharge inhibitor is usually 0.1% by mass or more and usually 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. Further, it is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, further preferably 0.5% by mass or more, and preferably 3% by mass or less, more preferably 2% by mass or less. is there. If it is the said range, the overcharge prevention effect can fully be aimed at, On the other hand, battery characteristics, such as a high temperature storage characteristic, can be ensured.

<Other auxiliaries>
Other known auxiliary agents can be used in the non-aqueous electrolyte solution of the present invention. Other auxiliary agents include lithium monofluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium fluorosulfonate, trifluoromethanesulfonic acid Examples of the lithium salt include lithium, lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, and lithium tetrafluorooxalatophosphate. By adding these auxiliaries, cycle characteristics and low-temperature discharge characteristics can be improved.

Further, as an auxiliary capable of improving capacity maintenance characteristics and cycle characteristics after high temperature storage, carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, anhydrous glutar Carboxylic anhydrides such as acid, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; Spiro compounds such as 2,4,8,10-tetraoxaspiro [5.5] undecane and 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane; ethylene sulfite; 1,3-propane sultone, 1-fluoro-1,3-propa Sultone, 2-fluoro-1,3-propane sultone,
3-fluoro-1,3-propane sultone, 1-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3 -Fluoro-1-propene-1,3-sultone, 1,4-butane sultone, 1-butene-1,4-sultone, 3-butene-1,4-sultone, methyl fluorosulfonate, ethyl fluorosulfonate, methane Sulfur-containing compounds such as methyl sulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl 2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and - nitrogen-containing compounds such as methyl succinimide; heptane, octane, nonane, decane, hydrocarbon compounds cycloheptane, etc., fluorobenzene, difluorobenzene, hexafluorobenzene, fluorinated aromatic compounds such as benzotrifluoride, and the like. These auxiliary agents may be used alone or in combination of two or more.

  The blending amount of other auxiliary agents is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The other auxiliary agent is usually 0.01% by mass or more and usually 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. The blending amount of other auxiliaries is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 3% by mass or less, more preferably 1% by mass or less. If it is the said range, the bad influence to a battery can be suppressed, fully exhibiting the effect of an adjuvant.

  The non-aqueous electrolyte solution described above includes those existing inside the non-aqueous electrolyte battery according to the present invention. Specifically, the components of the non-aqueous electrolyte such as lithium salt, solvent, and auxiliary agent are separately synthesized, and the non-aqueous electrolyte is prepared from the substantially isolated one by the method described below. In the case of a nonaqueous electrolyte solution in a nonaqueous electrolyte battery obtained by pouring into a separately assembled battery, the components of the nonaqueous electrolyte solution of the present invention are individually placed in the battery, In order to obtain the same composition as the non-aqueous electrolyte solution of the present invention by mixing in a non-aqueous electrolyte battery, the compound constituting the non-aqueous electrolyte solution of the present invention is further generated in the non-aqueous electrolyte battery. The case where the same composition as the aqueous electrolyte is obtained is also included.

3. Battery Configuration The non-aqueous electrolyte battery of the present invention is suitable for use as an electrolyte for a secondary battery, for example, a lithium secondary battery, among non-aqueous electrolyte batteries. Hereinafter, a non-aqueous electrolyte battery using the non-aqueous electrolyte of the present invention will be described.
The non-aqueous electrolyte secondary battery of the present invention can adopt a known structure. Typically, the negative electrode and the positive electrode capable of occluding and releasing ions (for example, lithium ions), and the non-aqueous electrolyte of the present invention described above. An aqueous electrolyte solution.

4). Positive electrode <Positive electrode active material>
The positive electrode active material used for the positive electrode is described below.
(composition)
The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. For example, a material containing lithium and at least one transition metal is preferable. Specific examples include lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.

V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable as the transition metal of the lithium transition metal composite oxide. Specific examples include lithium-cobalt composite oxides such as LiCoO ₂ , LiMnO ₂ , LiMn. Examples thereof include lithium / manganese composite oxides such as ₂ O ₄ and Li ₂ MnO ₄ and lithium / nickel composite oxides such as LiNiO 2. Further, some of the transition metal atoms that are the main components of these lithium transition metal composite oxides are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si. Specific examples include lithium-nickel-cobalt-aluminum composite oxides, lithium-cobalt-nickel composite oxides, lithium-cobalt-manganese composite oxides, lithium- Nickel / manganese composite oxide, lithium / nickel / cobalt / manganese composite oxide, and the like can be given. Among these, lithium / nickel / manganese composite oxide and lithium / nickel / cobalt / manganese composite oxide are preferable because of good battery characteristics.

Specific examples of the substituted ones include, for example, Li _{1 + a} Ni _0.5 Mn _0.5 O ₂ , Li _{1 + a} Ni _0.8 Co _0.2 O ₂ , Li _{1 + a} Ni _0.85 Co _0.10 Al _{0. 05} O ₂ , Li _{1 + a} Ni _0.33 Co _0.33 Mn _0.33 O ₂ , Li _{1 + a} Ni _0.45 Mn _0.45 Co _0.1 O ₂ , Li _{1 + a} Ni _0.475 Mn _0.475 Co _{0 .05} O ₂ , Li _{1 + a} Mn _1.8 Al _0.2 O ₄ , Li _{1 + a} Mn ₂ O ₄ , Li _{1 + a} Mn _1.5 Ni _0.5 O ₄ , xLi ₂ MnO _3. (1-x) Li _{1 + a} MO ₂ (M = transition metal, such as a metal selected from the group consisting of Li, Ni, Mn, and Co) (a; 0 <a ≦ 3.0). The ratio of these substituted metal elements in the composition formula is appropriately adjusted depending on the relationship between the battery characteristics of the battery using the element and the cost of the material.

The lithium-containing transition metal phosphate compound is Li _x MPO ₄ (M = a kind of element selected from the group consisting of group 4 to group 11 transition metals in the periodic table, x is 0 <x <1. 2), and the transition metal (M) includes V, Ti, Cr, Mg, Zn, Ca, Cd, Sr, Ba, Co, Ni,
It is preferably at least one element selected from the group consisting of Fe, Mn and Cu, and more preferably at least one element selected from the group consisting of Co, Ni, Fe and Mn. For example, iron phosphates such as LiFePO ₄ , Li ₃ Fe ₂ (PO4) ₃ , LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , manganese phosphates such as LiMnPO ₄ , nickel phosphates such as LiNiPO ₄ A part of transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Nb. And those substituted with other metals such as Si.

Among these, iron phosphates such as LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , LiFeP ₂ O ₇ are preferably used because they are less likely to cause metal elution at a high temperature and in a charged state and are inexpensive. It is done.
In addition, the above-mentioned “having Li _x MPO ₄ as a basic composition” means not only the composition represented by the composition formula but also a part of a site such as Fe in the crystal structure substituted with another element. Is also included. Furthermore, it means that not only a stoichiometric composition but also a non-stoichiometric composition in which some elements are deficient or the like is included. Other elements to be substituted are preferably elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si. When the substitution of other elements is performed, the content is preferably 0.1 mol% or more and 5 mol% or less, more preferably 0.2 mol% or more and 2.5 mol% or less.

The said positive electrode active material may be used independently and may use 2 or more types together.
Further, foreign elements may be introduced into the lithium transition metal-based compound powder of the present invention. Different elements include B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sn, Sb. Te, Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu , Bi, N, F, Cl, Br, or I. These foreign elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a single element or compound on the particle surface or grain boundary. May be unevenly distributed.

(Surface coating)
Moreover, you may use what the substance of the composition different from this adhered to the surface of the said positive electrode active material. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

  For example, these surface adhering substances are dissolved or suspended in a solvent, impregnated and added to the positive electrode active material, and dried. After the surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, It can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously. In addition, when making carbon adhere, the method of making carbonaceous adhere mechanically later in the form of activated carbon etc. can also be used, for example.

The amount of the surface adhering substance is by mass with respect to the positive electrode active material, preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and the upper limit, preferably 20% or less, more preferably, as the lower limit. Is used at 10% or less, more preferably 5% or less. The surface adhering substance can suppress the oxidation reaction of the electrolyte solution on the surface of the positive electrode active material, and can improve the battery life. In the case where it is too high, the resistance may increase in order to inhibit the entry and exit of lithium ions, so this composition range is preferable.
In the present invention, a material in which a material having a different composition is attached to the surface of the positive electrode active material is also referred to as “positive electrode active material”.

(shape)
Examples of the shape of the positive electrode active material particles include a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, and a column shape, which are conventionally used. It is preferable that the secondary particles have a spherical shape or an elliptical shape. In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, it is preferable that the primary particles are aggregated to form secondary particles, rather than a single particle active material having only primary particles, in order to relieve expansion and contraction stress and prevent deterioration. In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so that the expansion and contraction of the electrode during charging and discharging is small, and the electrode is produced. The mixing with the conductive material is also preferable because it is easy to mix uniformly.

(Median diameter d ₅₀ )
The median diameter d ₅₀ of the positive electrode active material particles (secondary particle diameter when primary particles are aggregated to form secondary particles) is preferably 0.1 μm or more, more preferably 0.5 μm or more, and further The upper limit is preferably 20 μm or less, more preferably 18 μm or less, still more preferably 16 μm or less, and most preferably 15 μm or less. If the lower limit is not reached, a high tap density product may not be obtained. If the upper limit is exceeded, it takes time to diffuse lithium in the particles, so that the battery performance may be lowered, or the positive electrode of the battery, that is, the active material When a conductive material, a binder, or the like is slurried with a solvent and applied as a thin film, problems such as streaking may occur. Here, by mixing two or more kinds of the positive electrode active materials having different median diameters d ₅₀ , the filling property at the time of forming the positive electrode can be further improved.

In the present invention, the median diameter d ₅₀ is measured by a known laser diffraction / scattering particle size distribution measuring apparatus. When LA-920 manufactured by HORIBA is used as a particle size distribution meter, a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.

(Average primary particle size)
When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is preferably 0.03 μm or more, more preferably 0.05 μm or more, and still more preferably 0.8. The upper limit is preferably 5 μm or less, more preferably 4 μm or less, still more preferably 3 μm or less, and most preferably 2 μm or less. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, or the specific surface area is greatly reduced, so that there is a high possibility that battery performance such as output characteristics will deteriorate. is there. On the other hand, when the value falls below the lower limit, there is a case where problems such as inferior reversibility of charge / discharge are usually caused because crystals are not developed.

  In the present invention, the primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.

<Configuration and manufacturing method of positive electrode>
The structure of the positive electrode will be described below. In the present invention, the positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. Manufacture of the positive electrode using a positive electrode active material can be performed by a conventional method. That is, a positive electrode active material, a binder, and, if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.

  The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. Moreover, an upper limit becomes like this. Preferably it is 95 mass% or less, More preferably, it is 93 mass% or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is preferably 1.5 g / cm ³ or more as a lower limit, more preferably 2 g / cm ³ , further preferably 2.2 g / cm ³ or more, and preferably 4.0 g as an upper limit. / cm ³ or less, more preferably 3.8 g / cm ³ or less, more preferably 3.6 g / cm ³ or less. If it exceeds this range, the permeability of the electrolyte solution to the vicinity of the current collector / active material interface decreases, and the charge / discharge characteristics particularly at a high current density decrease, and a high output may not be obtained. On the other hand, if it is lower, the conductivity between the active materials is lowered, the battery resistance is increased, and a high output may not be obtained.

(Conductive material)
A known conductive material can be arbitrarily used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more in the positive electrode active material layer, and the upper limit is usually 50% by mass or less, preferably It is used so as to contain 30% by mass or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. Conversely, if the content is higher than this range, the battery capacity may decrease.

(Binder)
The binder used for manufacturing the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that can be dissolved or dispersed in a liquid medium used during electrode manufacturing may be used. Resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber , Rubber polymers such as butadiene rubber and ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / Ethylene copolymer, styrene Thermoplastic elastomeric polymer such as isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer Soft resinous polymers such as polymers; Fluoropolymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers; alkali metal ions (especially lithium ions) And a polymer composition having ion conductivity. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and the upper limit is usually 80% by mass or less, preferably 60%. It is not more than mass%, more preferably not more than 40 mass%, most preferably not more than 10 mass%. If the ratio of the binder is too low, the positive electrode active material cannot be sufficiently retained, and the mechanical strength of the positive electrode is insufficient, which may deteriorate battery performance such as cycle characteristics. On the other hand, if it is too high, battery capacity and conductivity may be reduced.

(Thickener)
A thickener can be used normally in order to adjust the viscosity of the slurry used for manufacture of a positive electrode active material layer. In particular, when an aqueous medium is used, it is preferable to make a slurry using a thickener and a latex such as styrene-butadiene rubber (SBR). The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios. When a thickener is further added, the ratio of the thickener to the active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more. The upper limit is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Below this range, applicability may be significantly reduced. If it exceeds, the ratio of the active material in the positive electrode active material layer may decrease, and there may be a problem that the capacity of the battery decreases and a problem that the resistance between the positive electrode active materials increases.

(Current collector)
The material of the positive electrode current collector is not particularly limited, and a known material can be arbitrarily used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material. A thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape. Although the thickness of the thin film is arbitrary, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the thin film is thinner than this range, the strength required for the current collector may be insufficient. Conversely, if the thin film is thicker than this range, the handleability may be impaired.
Moreover, it is also preferable from the viewpoint of reducing the electronic contact resistance between the current collector and the positive electrode active material layer that a conductive additive is applied to the surface of the current collector. Examples of the conductive assistant include noble metals such as carbon, gold, platinum, and silver.

(Thickness of positive plate)
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the positive electrode active material layer obtained by subtracting the thickness of the metal foil (current collector) from the positive electrode plate is set on one side of the current collector. On the other hand, the lower limit is preferably 10 μm or more, more preferably 20 μm or more, and the upper limit is preferably 500 μm or less, more preferably 450 μm or less.

(Positive electrode surface coating)
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said positive electrode plate. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

5. Separator Normally, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.
The material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Among them, a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.

  As materials for the resin and glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 8 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

Furthermore, when a porous material such as a porous sheet or nonwoven fabric is used as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, and 45%
The above is more preferable, and it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.
On the other hand, as inorganic materials, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Used.

  As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the above-mentioned independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and using a fluororesin as a binder.

  The Gurley value of the separator represents the difficulty of air passage in the film thickness direction, and is expressed as the number of seconds required for 100 ml of air to pass through the film. Means that it is difficult to get through. That is, a smaller value means better communication in the thickness direction of the film, and a larger value means lower communication in the thickness direction of the film. Communication is the degree of connection of holes in the film thickness direction. If the Gurley value of the separator of the present invention is low, it can be used for various purposes. For example, when used as a separator for a non-aqueous lithium secondary battery, a low Gurley value means that lithium ions can be easily transferred and is preferable because of excellent battery performance. Although the Gurley value of a separator is arbitrary, Preferably it is 10-1000 second / 100ml, More preferably, it is 15-800 second / 100ml, More preferably, it is 20-500 second / 100ml. If the Gurley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, which is preferable as a separator.

6). Battery design <Electrode group>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape through the separator. Either is acceptable. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .

  When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

<Exterior case>
The material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

  In an exterior case using metals, the metal is welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things. Examples of the outer case using the laminate film include a case where a resin-sealed structure is formed by heat-sealing resin layers. In order to improve sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

<Protective element>
Protective elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, whose resistance increases when abnormal heat generation or excessive current flows, cut off current flowing in the circuit due to sudden rise in battery internal pressure or internal temperature in abnormal heat generation A valve (current cutoff valve) or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element is designed so as not to cause abnormal heat generation or thermal runaway even without the protective element.

<Exterior body>
The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body. This exterior body is not particularly limited, and any known one can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.
The shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.
<Example 1>
[Negative electrode]
A carbonaceous material having the following physical properties was used as the negative electrode active material. Specifically, the d value (interlayer distance) of the lattice plane (002 plane) of the negative electrode active material measured by the above method is 0.336 nm, the volume-based average particle diameter is 11.6 μm, and the BET specific surface area is 3. Natural graphite having 4 m ² / g, tap density of 0.99 g · cm ⁻³ , Raman R value of 0.33, and O / C value of 0.91 was used.

98 parts by mass of the negative electrode active material, 100 parts by mass of an aqueous dispersion of sodium carboxymethyl cellulose (concentration of 1% by mass of sodium carboxymethyl cellulose) and an aqueous dispersion of styrene-butadiene rubber (styrene) as a thickener and binder, respectively. 1 part by mass of a butadiene rubber concentration of 50% by mass was added and mixed with a disperser to form a slurry. The obtained slurry was applied to a copper foil having a thickness of 18 μm, dried, rolled to an electrode density of 1.7 g / cm ³ with a press, and the cut out was used as the negative electrode.

[Positive electrode]
Using 90 parts by mass of lithium nickel manganese cobaltate (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) as a positive electrode active material, 7 parts by mass of carbon black and polyvinylidene fluoride 3
After mixing parts by mass, N-methyl-2-pyrrolidone was added to form a slurry, which was uniformly coated on both sides of an aluminum foil having a thickness of 15 μm and dried, and then the density of the positive electrode active material layer was 2.6 g · cm ^{−. 3} was pressed to obtain a positive electrode.

[Electrolyte]
Under a dry argon atmosphere, fully dried LiPF6 was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4) so that the total amount of the non-aqueous electrolyte was 1 mol / L. (This electrolyte may be referred to as a “reference electrolyte”). To the reference electrolyte, 1,6-diisocyanatohexane (HDI) was added to 0.5% by mass to prepare a non-aqueous electrolyte.

[Lithium secondary battery]
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode. The battery element thus obtained was wrapped in a cylindrical aluminum laminate film, injected with an electrolytic solution, and then vacuum sealed to produce a sheet-like non-aqueous electrolyte secondary battery. Furthermore, in order to improve the adhesion between the electrodes, the sheet-like battery was sandwiched between glass plates and pressurized.

[Battery evaluation]
[Run-in operation]
In a constant temperature bath at 25 ° C., the sheet-like non-aqueous electrolyte secondary battery was charged at constant current-constant voltage to 4.1 V at 0.2 C, and then discharged to 3.0 V at 0.2 C. This was performed for 5 cycles to stabilize the battery. In addition, 1C is a current value when discharging the entire capacity of the battery in one hour.

[Evaluation of cycle characteristics]
The battery after the running-in operation was charged with a constant current corresponding to 2C at 60 ° C., and then discharged with a constant current of 2C as one cycle, and 750 cycles were performed. Here, 1C represents a current value that discharges the reference capacity of the battery in one hour, 2C represents a current value that is twice that, and 0.2C represents a current value that is 1/5 of the current value. The capacity retention rate was calculated from the formula of (discharge capacity at the 750th cycle) ÷ (discharge capacity at the first cycle) × 100.

[Evaluation of low-temperature discharge characteristics]
For a battery charged by an amount of electricity corresponding to 50% of the initial capacity, 0.3C, 0.5C, 1.0C, 1.5C, 2.0C, and 2.5C under an environment of −30 ° C. Each was discharged for 10 seconds, and the voltage for the second second was measured. In the current-voltage curve thus obtained, a current value at 3 V was calculated, and this value was used as a low temperature discharge characteristic (output). The rate of change in the low temperature discharge characteristics was determined from the formula {(low temperature discharge characteristics after running-in) − (low temperature discharge characteristics after 1000 cycles)} ÷ (low temperature discharge characteristics after running-in) × 100.

<Example 2>
A carbonaceous material having the following physical properties was used as the negative electrode active material. Specifically, the d value (interlayer distance) of the lattice plane (002 plane) of the negative electrode active material is 0.336 nm, the volume reference average particle size is 9.8 μm, the BET specific surface area is 4.2 m ² / g, the tap density. There 1.00 g · ^{cm -3,} the Raman R value is 0.39, O / C value using natural graphite is 1.02. A battery was assembled using the same positive electrode and electrolytic solution as in Example 1 except that the negative electrode active material was changed, and only the capacity retention rate was obtained in the same manner.

<Example 3>
A carbonaceous material having the following physical properties was used as the negative electrode active material. Here, the negative electrode active material was baked at 1000 ° C. in a nitrogen atmosphere and then oxidized with hydrogen peroxide. Specific physical property values include a d value (interlayer distance) of the lattice plane (002 plane) of the negative electrode active material of 0.336 nm, a volume-based average particle diameter of 9.7 μm, a BET specific surface area of 3.7 m ² / g, Natural graphite having a tap density of 1.00 g · cm ⁻³ , a Raman R value of 0.51, and an O / C value of 1.50 was used. A battery was assembled using the same positive electrode and electrolyte as in Example 1 except that the negative electrode active material was changed, and the capacity retention rate was similarly determined.

<Example 4>
A carbonaceous material having the following physical properties was used as the negative electrode active material. Here, the negative electrode active material was mechanochemically treated in air. Specific physical property values include a d value (interlayer distance) of the lattice plane (002 plane) of the negative electrode active material of 0.336 nm, a volume-based average particle diameter of 9.7 μm, a BET specific surface area of 4.4 m ² / g, Natural graphite having a tap density of 0.94 g · cm ⁻³ , a Raman R value of 0.39, and an O / C value of 4.07 was used. A battery was assembled using the same positive electrode and electrolyte as in Example 1 except that the negative electrode active material was changed, and the capacity retention rate was similarly determined.

<Example 5>
A carbonaceous material having the following physical properties was used as the negative electrode active material. Here, the negative electrode active material was mechanochemically treated in air. Specific physical property values include a d value (interlayer distance) of the lattice plane (002 plane) of the negative electrode active material of 0.336 nm, a volume-based average particle size of 9.7 μm, a BET specific surface area of 4.5 m ² / g, Natural graphite having a tap density of 0.91 g · cm ⁻³ , a Raman R value of 0.50, and an O / C value of 6.2 was used. A battery was assembled using the same positive electrode and electrolyte as in Example 1 except that the negative electrode active material was changed, and the capacity retention rate was similarly determined.

<Comparative Example 1>
As the negative electrode active material, a material obtained by firing the same active material as in Example 1 in the presence of hydrogen was used. Specific physical property values include a d-value (interlayer distance) of the lattice plane (002 plane) of the negative electrode active material of 0.336 nm, a volume-based average particle diameter of 11.6 μm, a BET specific surface area of 3.4 m ² / g, and a tap. The density is 0.99 g · cm ⁻³ , the Raman R value is 0.28, and the O / C value is 0.41. A battery was assembled using the same positive electrode and electrolyte as in Example 1 except that the negative electrode active material was changed, and the capacity retention rate was similarly determined.

<Comparative example 2>
As the negative electrode active material, a material obtained by firing the same active material as in Example 5 at 1000 ° C. in a nitrogen atmosphere was used. Specific physical property values include a d-value (interlayer distance) of the lattice plane (002 plane) of the negative electrode active material of 0.336 nm, a volume-based average particle diameter of 9.7 μm, a BET specific surface area of 4.5 m ² / g, and a tap. The density is 0.91 g · cm ⁻³ , the Raman R value is 0.46, and the O / C value is 0.59. A battery was assembled using the same positive electrode and electrolyte as in Example 1 except that the negative electrode active material was changed, and the capacity retention rate was similarly determined.

<Comparative Example 3>
A battery was assembled using the same negative electrode and positive electrode as in Comparative Example 2 except that the electrolytic solution was changed to the reference electrolytic solution, and the capacity retention rate was similarly determined.
<Comparative example 4>
A battery was assembled using the same negative electrode and positive electrode as in Example 1 except that the electrolytic solution was changed to the reference electrolytic solution, and the capacity retention rate was similarly determined.

<Comparative Example 5>
A battery was assembled using the same negative electrode and positive electrode as in Example 2 except that the electrolytic solution was changed to the reference electrolytic solution, and the capacity retention rate was similarly determined.
<Comparative Example 6>
A battery was assembled using the same negative electrode and positive electrode as in Example 5 except that the electrolytic solution was changed to the reference electrolytic solution, and the capacity retention rate was similarly determined.
For the batteries of Example 2, Example 5, Comparative Example 2, Comparative Example 3, Comparative Example 5 and Comparative Example 6, the cycle test was continued up to 1000 cycles, and the change rate of the low-temperature discharge characteristics was obtained.

  As is apparent from Table 1, when a negative electrode having an O / C value within the range of the present invention and a non-aqueous electrolyte solution containing the isocyanate compound of the present invention were combined (Examples 1 to 5), O / C When the negative electrode whose value is outside the scope of the present invention and the non-aqueous electrolyte solution containing the isocyanate compound of the present invention are combined (Comparative Examples 1-2) and when the isocyanate compound of the present invention is not contained in the non-aqueous electrolyte solution ( It turns out that it is excellent in cycle capacity maintenance compared with Comparative Examples 3-6).

  In addition, the degree of the effect on the cycle retention rate becomes prominent with the O / C value near 0.8 as a threshold, and the cycle retention rate tends to increase as the O / C value increases. The degree of increase is greater when the isocyanate compound is contained in the non-aqueous electrolyte. That is, the higher the O / C value, the higher the efficacy of the compound of the present invention. In general, it is desirable that the battery has stable performance against repeated use. However, according to the present invention, the change in the low-temperature discharge characteristics associated with the cycle test can be greatly suppressed (Examples 2 and 5 and Comparative Example 5). , 6 comparison). As described above, when an isocyanate compound is contained in the nonaqueous electrolytic solution, the effect tends to be significantly increased depending on the O / C value.

  The reason for exhibiting such excellent battery durability is that the formation of a high-quality film that effectively suppresses the reductive decomposition of the solvent by the isocyanate compound, and that part of the film is composed of oxygen functional groups on the surface of the negative electrode active material. This is presumed to be firmly bound by the strong interaction between them.

Claims (8)

  A non-aqueous electrolyte solution comprising a lithium salt and a non-aqueous solvent that dissolves the lithium salt, a negative electrode capable of occluding and releasing lithium ions, and a positive electrode, wherein the negative electrode is X It contains a negative electrode active material made of a carbonaceous material having a surface oxygen content (O / C) of 0.8 atom% or more obtained from line photoelectron spectroscopy, and the non-aqueous electrolyte contains a compound having an isocyanate group A non-aqueous electrolyte secondary battery. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein at least part of the compound having an isocyanate group is a compound represented by the general formula (1).

(Wherein, A represents a hydrogen atom, a halogen atom, a vinyl group, an isocyanate group, or a _C 1 ~
C represents a _{2 0} aliphatic hydrocarbon group (which may have a hetero atom) or a C ₆ -C _{2 0} aromatic hydrocarbon group (which may have a hetero atom). B is an oxygen atom, S ₂ O ₂ , OSO ₂ , SO 3, OCO, COO, or a C ₁ to C ₂₀ aliphatic hydrocarbon group (which may have a hetero atom), or C _{6 to} C _{2. 0 represents} an aromatic hydrocarbon group (which may have a hetero atom). ) The non-aqueous electrolyte secondary solution according to claim 1 or 2, wherein at least a part of the compound represented by the general formula (1) is a compound represented by the general formula (2). battery.

(Wherein x is 4 to 12)   The at least one part of the compound which has the said isocyanate group contains the polyisocyanate whose average functional group number is 2 or more and whose number average molecular weight is 300-5000, The any one of Claims 1-3 characterized by the above-mentioned. Non-aqueous electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the isocyanate compound is contained in an amount of 0.01% by mass to 5% by mass with respect to the entire non-aqueous solvent.   The surface oxygen content (O / C) calculated | required from the said X-ray photoelectron spectroscopy is 1.0 atom% or more, The non-aqueous electrolyte solution 2 of any one of Claims 1-5 characterized by the above-mentioned. Next battery. The negative electrode, the Raman R value, defined as the ratio of the peak intensity of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 in the argon ion laser Raman spectroscopy to contain at least one or more carbonaceous material is 0.10 or more The non-aqueous electrolyte secondary battery according to claim 1, comprising a negative electrode active material.   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein surface oxygen of the carbonaceous material is applied by a method of mechanochemical treatment in an oxygen atmosphere.