JP2013026505A - Nonaqueous lithium type electricity storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous lithium type electricity storage element capable of achieving both high input/output characteristics at low temperature and high cycle life characteristics at high temperature.SOLUTION: In a nonaqueous lithium type electricity storage element, a nonaqueous electrolyte and an electrode laminate which is obtained by laminating a negative electrode body, a positive electrode body and a separator are housed in an outer packaging body, a negative electrode material is a carbon material, and a positive electrode material is an active carbon. The nonaqueous electrolyte includes a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent at a concentration of 0.5 mol/L or more. The nonaqueous solvent contains: an ordinary temperature molten salt formed of a cyclic quaternary ammonium organic compound cation and an anion comprising a nonmetallic element; and a cyclic carbonate and a chain carbonate. A percentage content of the ordinary temperature molten salt is 20-70% by volume.

Description

  The present invention relates to a non-aqueous lithium storage element.

  In recent years, midnight power storage systems, home-use distributed power storage systems based on solar power generation technology, power storage systems for electric vehicles, etc. have attracted attention from the viewpoint of global environment conservation and effective use of energy for resource saving. Yes.

  In these power storage systems, the first requirement is that the energy density of the power storage element used is high. As a promising candidate for a high energy density storage element capable of meeting such demands, development of lithium ion batteries has been energetically advanced.

  The second requirement is high output characteristics. For example, a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell electric vehicle) requires high output discharge characteristics in the power storage system during acceleration. ing.

  Currently, as a high power storage element, an electric double layer capacitor using activated carbon as an electrode (hereinafter also simply referred to as “capacitor”) has been developed, and durability (particularly cycle characteristics and high temperature storage characteristics) is high. It has an output characteristic of about 0.5 to 1 kW / L. These electric double layer capacitors have been considered as the most suitable storage element in the field where the above high output is required, but the energy density is only about 1 to 5 Wh / L, and the output duration time is not practical. It is a footpad.

  On the other hand, nickel-metal hydride batteries currently used in hybrid electric vehicles realize high output equivalent to electric double layer capacitors and have an energy density of about 160 Wh / L. However, research is underway energetically to further increase the energy density and output, further improve the stability at high temperatures, and increase the durability.

  In addition, research for higher output is also being conducted in lithium ion batteries. For example, a lithium-ion battery has been developed that can obtain a high output exceeding 3 kW / L at a discharge depth (that is, a value representing what percentage of the device discharge capacity is discharged) 50%. It is 100 Wh / L or less, and is designed to deliberately suppress the high energy density, which is the greatest feature of lithium ion batteries. Further, its durability (particularly cycle characteristics and high temperature storage characteristics) is inferior to that of an electric double layer capacitor. Therefore, in order to give practical durability, a lithium ion battery can be used only in a range where the depth of discharge is narrower than the range of 0 to 100%. For this reason, the capacity that can be actually used is further reduced, and research for further improving the durability is being actively pursued.

  As described above, there is a strong demand for practical use of a power storage element having high output density, high energy density, and durability. However, the existing power storage element described above has advantages and disadvantages. Therefore, a new power storage element that satisfies these technical requirements has been demanded, and development of a power storage element called a lithium ion capacitor has been actively developed as a promising candidate.

  A lithium ion capacitor is a type of storage element that uses a non-aqueous electrolyte containing an electrolyte containing lithium ions (that is, a non-aqueous lithium storage element), and in the positive electrode, an anion similar to an electric double layer capacitor is used. It is a power storage element that performs charge and discharge by a non-Faraday reaction by adsorption / desorption, and a Faraday reaction by occlusion / release of lithium ions in the negative electrode similar to a lithium ion battery.

  As described above, an electric double layer capacitor that charges and discharges by a non-Faraday reaction in both the positive electrode and the negative electrode has excellent output characteristics but low energy density. On the other hand, a lithium ion battery that is a secondary battery that charges and discharges by a Faraday reaction in both the positive electrode and the negative electrode is excellent in energy density but inferior in output characteristics. A lithium ion capacitor is a new power storage element that aims to achieve both excellent output characteristics and high energy density by performing charge and discharge by a non-Faraday reaction at the positive electrode and a Faraday reaction at the negative electrode.

  Applications using lithium ion capacitors include railways or construction machinery, and power storage for automobiles. In these applications, since the operating environment is harsh, it is necessary to have excellent temperature characteristics. Specifically, high input / output characteristics at low temperatures or high cycle life characteristics at high temperatures. As such a lithium ion capacitor, a power storage element in which a fluorinated cyclic carbonate is contained in an electrolytic solution has been proposed (see Patent Document 1). Although this storage element can provide a capacitor having low resistance and excellent characteristics at low temperature, the direct current internal resistance at −30 ° C. has increased about 20 times compared to that at room temperature, and is still the target. It cannot be said that performance has been expressed.

  Similarly, a power storage element in which vinylene carbonate or a derivative thereof is contained in an electrolytic solution has been proposed (see Patent Document 2). Although this storage element is said to be able to provide a capacitor with a high capacity retention rate during continuous charging at high temperatures, no results have been shown regarding the rate of increase in DC internal resistance or the change in input / output characteristics after testing. It cannot be said that the target performance has been expressed.

  In recent years, for the purpose of developing high input / output characteristics or high cycle life characteristics, development of a lithium ion battery using a room temperature molten salt as an electrolytic solution has been proposed (see Patent Documents 3 and 4). Patent Document 3 is characterized in that a mixed solvent of a room temperature molten salt and carbonate is used as an electrolyte solution solvent and contains 50% by volume or more of carbonate, and sufficient charge / discharge efficiency is obtained. However, there is no description regarding cycle durability, and its characteristics are unknown. Further, Patent Document 4 is characterized by mixing a cyclic carbonate or a chain carbonate or a cyclic carbonate having a C = C unsaturated bond with a room temperature molten salt as a solvent, and the cycle characteristics are improved. . However, there is no description regarding input / output characteristics at low temperatures, and the characteristics are unknown.

  On the other hand, development examples of improving the characteristics of lithium ion capacitors using room temperature molten salt as the electrolyte have not been known so far, and high input / output characteristics at low temperatures and high cycle life at high temperatures. There is no one that has both characteristics.

  As described above, in conventional lithium ion capacitors, high input / output characteristics at low temperatures and high cycle life characteristics at high temperatures are not sufficient.

JP 2006-286926 A JP 2006-286924 A JP 2003-288939 A JP 2006-85912 A

  An object of the present invention is to provide a non-aqueous lithium storage element capable of achieving both high input / output characteristics at low temperatures and high cycle life characteristics at high temperatures.

  As a result of intensive research to solve the above problems, the present inventors have developed an excellent output characteristic at low temperatures by mixing an appropriate amount of room temperature molten salt as an electrolyte solvent for a lithium ion capacitor. Furthermore, it has been found that since the decomposition of the electrolyte solvent can be suppressed as much as possible at high temperatures, high cycle life characteristics can be expressed.

  That is, the present invention provides the following non-aqueous lithium storage element.

  [1] A negative electrode body in which a negative electrode active material layer containing a negative electrode active material is provided on a negative electrode current collector, a positive electrode body in which a positive electrode current collector is provided with a positive electrode active material layer containing a positive electrode active material, and a separator are laminated. And a non-aqueous lithium-type electricity storage element in which a non-aqueous electrolyte solution containing an electrolyte containing lithium ions is housed in an exterior body, the negative electrode active material being a carbon material capable of occluding and releasing lithium ions The positive electrode active material is activated carbon, and the non-aqueous electrolyte is composed of a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent at a concentration of 0.5 mol / L or more. A room temperature molten salt formed from a cyclic quaternary ammonium organic cation and an anion composed of a nonmetallic element, and a cyclic carbonate and a chain carbonate, and the content of the room temperature molten salt is the room temperature molten salt The total volume of the annular carbonate and the chain carbonate is 20 vol% to 70 vol%, the non-aqueous lithium-type storage element.

  [2] The non-aqueous lithium storage element according to [1], wherein the cyclic quaternary ammonium organic cation contains at least one of an imidazolium cation or a pyridinium cation.

  [3] The cyclic quaternary ammonium organic cation includes 1-ethyl-3-methylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, 1,3-diethylimidazolium ion, 1-butyl-3. -The non-aqueous lithium storage element according to [2], which contains at least one selected from methylimidazolium ion or N-butylpyridinium ion.

[4] The non-aqueous lithium according to any one of [1] to [3], wherein the lithium salt contains lithium hexafluorophosphate (LiPF ₆ ) and / or lithium borofluoride (LiBF ₄ ). Type storage element.

[5] Any of [1] to [4], wherein the anion in the non-aqueous electrolyte includes at least one anion other than hexafluorophosphate ion (PF ₆ ⁻ ) and the hexafluorophosphate ion. 2. A non-aqueous lithium storage element according to item 1.

[6] The negative electrode active material is a composite porous material in which a carbon material is deposited on the surface of activated carbon, and the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is Vm1 ( cc / g), when the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is Vm2 (cc / g),
0.010 ≦ Vm1 ≦ 0.250,
The non-aqueous lithium storage element according to any one of [1] to [5], wherein 0.001 ≦ Vm2 ≦ 0.200 and 1.5 ≦ Vm1 / Vm2 ≦ 20.0 are satisfied.

[7] The positive electrode active material is derived from V1 (cc / g) mesopore amount derived from pores having a diameter of 20 to 500 mm calculated by the BJH method, and pores having a diameter of less than 20 mm calculated by the MP method. When the micropore amount is V2 (cc / g),
It is activated carbon that satisfies 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0, and has a specific surface area measured by the BET method of 1500 m ² / g to 3000 m ² / g. [1] The nonaqueous lithium-type electricity storage device according to any one of [6].

  According to the present invention, a non-aqueous lithium storage element capable of achieving both high input / output characteristics at low temperatures and high cycle life characteristics at high temperatures is provided.

Hereinafter, embodiments of the present invention will be described in detail.
[Storage element]
In the embodiment of the present invention, the storage element is a non-aqueous lithium type, and a negative electrode body in which a negative electrode active material layer including a negative electrode active material is formed, and a positive electrode active material layer including a positive electrode active material are formed. An electrode laminate in which a positive electrode body and a separator are laminated, and a non-aqueous electrolyte solution containing a lithium ion-containing electrolyte are housed in an exterior body.

[Electrolyte]
In the embodiment of the present invention, the electrolytic solution is a non-aqueous electrolytic solution, and includes a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent at a concentration of 0.5 mol / L or more. The non-aqueous solvent includes a room temperature molten salt formed of a cyclic quaternary ammonium organic cation and an anion composed of a nonmetallic element, and a cyclic carbonate and a chain carbonate. Moreover, the content rate of this room temperature molten salt is 20 volume%-70 volume% with respect to the non-aqueous solvent, ie, with respect to the sum total of this room temperature molten salt, this cyclic carbonate, and a chain carbonate.

The lithium salt may be a salt having a solubility of 0.5 mol / L or more in the electrolytic solution. For example, LiPF ₆ , LiBF ₄ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (SO ₂ C ₂ F ₅ ), LiN (SO ₂ CF ₃ ) (SO ₂ C ₂ F ₄ H ) And mixed salts thereof. The lithium salt preferably contains LiPF ₆ and / or LiBF ₄ from the viewpoint that high conductivity can be exhibited.

  The reason why the electricity storage device of the present invention can express high output characteristics at low temperatures is not limited, but there is a different anion species due to the presence of a room temperature molten salt in the electrolyte, Since the amorphous nature of the ion arrangement is improved and crystallization at the molecular level can be suppressed, it is considered that the high ion mobility is expressed as a factor. Therefore, the lithium salt is preferably a substance whose anion species is different from the anion species of the ambient temperature molten salt to be mixed, and it is preferable that two or more anion species exist in the electrolytic solution.

  Furthermore, the lithium salt concentration in the non-aqueous solvent is 0.5 mol / L or more, and a range of 0.5 to 2.0 mol / L is preferable. If the lithium salt concentration is 0.5 mol / L or more, there is a tendency that the capacity of the energy storage device is increased because sufficient anions are present. Moreover, if the lithium salt concentration is 2.0 mol / L or less, the undissolved lithium salt will not precipitate in the electrolyte solution, and the viscosity of the electrolyte solution will not become too high. This is preferable because there is a tendency that the output characteristics do not deteriorate and the output characteristics do not deteriorate.

  In addition, these lithium salts may be used independently or may be used in mixture of 2 or more types.

Next, the room temperature molten salt in the embodiment of the present invention will be described.
In the embodiment of the present invention, the room temperature molten salt of the electricity storage device is a substance formed from an anion composed of a cyclic quaternary ammonium organic cation and a nonmetallic element.

  The cyclic quaternary ammonium organic cation may have an aromatic ring or an aliphatic ring. Cyclic quaternary ammonium organic cation includes imidazolium cation, pyridinium cation, pyrazolium cation, triazolium cation, thiazolium cation, oxazolium cation, pyridazinium cation, pyrazinium cation, pyrrolium cation Pyrrolinium cation, pyrrolidinium cation, piperidinium cation and the like. Of these, imidazolium cation or pyridinium cation is particularly preferable.

  Examples of the imidazolium cation or pyridinium cation include, but are not limited to, 1-ethyl-3-methylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, 1,3-diethylimidazolium ion. , 1-butyl-3-methylimidazolium ion, or N-butylpyridinium ion is included in the non-aqueous solvent.

Further, the anion composed of a nonmetallic element is not particularly limited, but ClO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , CN ⁻ , COO ⁻ , SO ₂ CF ₂ ⁻ , N ( ^{_{CF 3 SO 2) 2 -,}} N (C 2 F 5 SO 2) 2 -, N (CF 3 SO 2) (C 2 F 5 SO 2) -, N (CF 3 SO 2) (C 4 F 9 SO ₂ ) ⁻ , C (CF ₃ SO ₂ ) ₃ ⁻ , C (C ₂ F ₅ SO ₂ ) ₃ ⁻ , p-toluenesulfonate, etc., among which BF ₄ ⁻ , PF ₆ ⁻ , N (CF _{3 ^{SO 2) 2 -, C (}} CF 3 SO 2) 3 -, bis (at least one selected from trifluoromethanesulfonyl) imide or p- toluenesulphonate are is preferably contained in the nonaqueous solvent. For the reasons described above, it is preferable that two or more kinds of anion species are present in the electrolytic solution. Therefore, a substance different from the anion species of the lithium salt may be used as the anion of the room temperature molten salt. preferable.

  In addition, these normal temperature molten salts may be used independently or may be used in mixture of 2 or more types.

Next, solvents other than the room temperature molten salt contained in the non-aqueous solvent will be described.
The non-aqueous solvent includes a cyclic carbonate and a chain carbonate as the organic solvent in addition to the room temperature molten salt. Examples of the cyclic carbonate include compounds typified by ethylene carbonate, propylene carbonate, butylene carbonate and the like. Examples of the chain carbonate include compounds typified by dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, dibutyl carbonate and the like. In the electricity storage device of the present invention, a nonaqueous electrolytic solution having both a high dielectric constant and a low viscosity can be obtained by mixing a cyclic carbonate and a chain carbonate in an electrolytic solution and further mixing a room temperature molten salt.

  In an embodiment of the present invention, in order to provide a non-aqueous lithium storage element that can achieve both high input / output characteristics at low temperatures and high cycle life characteristics at high temperatures, the content of the room temperature molten salt is And 20% by volume to 70% by volume, and more preferably 30% by volume to 60% by volume, based on the total of the cyclic carbonate and the chain carbonate (that is, based on the total volume of the nonaqueous solvent). If the ambient temperature molten salt is 20% by volume or more, it is considered that the ratio of the cyclic carbonate and the chain carbonate in the electrolytic solution is appropriately maintained, and the amount of decomposition of the solvent is reduced. Life characteristics are improved. On the other hand, when the room temperature molten salt is 70% by volume or less, the viscosity of the electrolytic solution becomes appropriate, and the input / output characteristics at low temperatures are improved.

Further, in the embodiment of the present invention, in addition to lithium salt, room temperature molten salt, cyclic carbonate and chain carbonate, for example, γ-butyrolactone, propiolactone, valerolactone, tetrahydrofuran, dimethoxyethane, di-acid, A compound such as ethoxyethane may be added as appropriate.
The anion in the nonaqueous electrolytic solution contains at least hexafluorophosphate ion (PF ₆ ⁻ ), and preferably contains two or more types of anions.

[Positive electrode active material]
Activated carbon can be used as the positive electrode active material contained in the positive electrode current collector. There are no particular restrictions on the type of activated carbon and its raw materials, but in order to achieve both high capacity (ie high energy density) and high power characteristics (ie high power density), the pores of the activated carbon can be optimally controlled. preferable. Specifically, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is calculated. When V2 (cc / g) is satisfied, 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied, and the specific surface area measured by the BET method is 1500 m ² / g or more and 3000 m ^2. Activated carbon that is less than / g is preferred.

  The mesopore amount V1 is preferably a value larger than 0.3 cc / g from the viewpoint of increasing the output characteristics when the positive electrode material is incorporated in the power storage element, and also from the viewpoint of suppressing a decrease in the capacity of the power storage element. , Preferably 0.8 cc / g or less. V1 is more preferably 0.35 cc / g or more and 0.7 cc / g or less, and further preferably 0.4 cc / g or more and 0.6 cc / g or less.

  On the other hand, the micropore volume V2 is preferably 0.5 cc / g or more in order to increase the specific surface area of the activated carbon and increase the capacity, and also suppresses the bulk of the activated carbon and increases the density as an electrode. From the viewpoint of increasing the capacity per unit volume, it is preferably 1.0 cc / g or less. The V2 is more preferably 0.6 cc / g or more and 1.0 cc / g or less, and further preferably 0.8 cc / g or more and 1.0 cc / g or less.

  Further, the ratio (V1 / V2) of the mesopore amount V1 to the micropore amount V2 is preferably in the range of 0.3 ≦ V1 / V2 ≦ 0.9. That is, V1 / V2 is preferably 0.3 or more from the viewpoint of increasing the ratio of the mesopore amount to the micropore amount to such an extent that the decrease in output characteristics can be suppressed while obtaining a high capacity. V1 / V2 is preferably 0.9 or less from the viewpoint of increasing the ratio of the micropore amount to the mesopore amount so that the decrease in capacity can be suppressed while obtaining high output characteristics. A more preferable range of V1 / V2 is 0.4 ≦ V1 / V2 ≦ 0.7, and a more preferable range of V1 / V2 is 0.55 ≦ V1 / V2 ≦ 0.7.

  In the present invention, the micropore volume and mesopore volume are values determined by the following method. That is, the sample is vacuum-dried at 500 ° C. all day and night, and the adsorption and desorption isotherm is measured using nitrogen as an adsorbate. Using the isotherm on the desorption side at this time, the micropore volume is calculated by the MP method, and the mesopore volume is calculated by the BJH method.

  The MP method uses a “t-plot method” (BC Lippens, JH de Boer, J. Catalysis, 4319 (1965)), and uses a micropore volume, a micropore area, and a micropore. Is a method for obtaining the distribution of M.M. It is a method devised by Mikhail, Brunauer, Bodor (RS Mikhal, S. Brunauer, EE Bodor, J. Colloid Interface Sci., 26, 45 (1968)). The BJH method is a calculation method generally used for analysis of mesopores and was proposed by Barrett, Joyner, Halenda et al. (EP Barrett, LG Joyner and P. Halenda, J Amer. Chem. Soc., 73, 373 (1951)).

  The average pore diameter of the activated carbon is preferably 17 mm or more, more preferably 18 mm or more, and most preferably 20 mm or more in order to maximize the output. Further, from the point of maximizing the capacity, it is preferably 25 mm or less. The average pore diameter described in the present specification is obtained by dividing the total pore volume per weight obtained by measuring each equilibrium adsorption amount of nitrogen gas at each relative pressure at the liquid nitrogen temperature by the BET specific surface area. Point to what you asked for.

BET specific surface area of the activated carbon is preferably from 1500 m ² / g or more 3000 m ² / g, more preferably not more than 1500 m ² / g or more 2500 m ² / g. When the BET specific surface area is 1500 m ² / g or more, good energy density is easily obtained. On the other hand, when the BET specific surface area is 3000 m ² / g or less, a large amount of binder is used to maintain the strength of the electrode. Since it is not necessary to put in, the performance per electrode volume tends to be high.

  The activated carbon having the above-described characteristics can be obtained using, for example, raw materials and processing methods as described below.

  In the embodiment of the present invention, the carbon source used as the raw material for the activated carbon is not particularly limited, and for example, plant raw materials such as wood, wood flour, coconut shell, by-products during pulp production, bagasse, and molasses. Fossil materials such as peat, lignite, lignite, bituminous coal, anthracite, petroleum distillation residue components, petroleum pitch, coke, coal tar; phenol resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin, celluloid And various synthetic resins such as epoxy resin, polyurethane resin, polyester resin, and polyamide resin; synthetic rubber such as polybutylene, polybutadiene, and polychloroprene; other synthetic wood, synthetic pulp, and their carbides. Among these raw materials, plant-based raw materials such as coconut shells and wood flour, and carbides thereof are preferable, and coconut shell carbides are particularly preferable.

  As a method of carbonization and activation for making these raw materials into the activated carbon, known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method can be adopted.

  As a carbonization method of these raw materials, nitrogen, carbon dioxide, helium, argon, xenon, neon, carbon monoxide, an exhaust gas such as combustion exhaust gas, or other gases mainly composed of these inert gases. The method of baking for about 30 minutes-about 10 hours at about 400-700 degreeC (preferably 450-600 degreeC) using mixed gas is mentioned.

  As a method for activating the carbide obtained by the carbonization method, a gas activation method in which firing is performed using an activation gas such as water vapor, carbon dioxide, or oxygen is preferably used. Among these, a method using water vapor or carbon dioxide as the activation gas is preferable.

  In this activation method, the carbide is supplied for 3 to 12 hours (preferably 5 to 11) while supplying the activation gas at a rate of 0.5 to 3.0 kg / h (preferably 0.7 to 2.0 kg / h). It is preferable to activate by heating to 800 to 1000 ° C. over a period of time, more preferably 6 to 10 hours.

  Furthermore, prior to the activation treatment of the carbide, the carbide may be activated in advance. In this primary activation, it is usually possible to activate the gas by firing the carbon material at a temperature below 900 ° C. using an activation gas such as water vapor, carbon dioxide or oxygen.

  By appropriately combining the firing temperature and firing time in the carbonization method, the activation gas supply amount, the heating rate and the maximum activation temperature in the activation method, the activated carbon having the above characteristics, which can be used in the embodiment of the present invention. Can be manufactured.

  The average particle size of the activated carbon is preferably 1 to 20 μm. The average particle size described in the present specification is the particle at which the cumulative curve becomes 50% when the cumulative curve is determined with the total volume being 100% when the particle size distribution is measured using a particle size distribution measuring device. Diameter (ie 50% diameter (Median diameter)).

  When the average particle size is 1 μm or more, the capacity per electrode volume tends to increase because the density of the active material layer is high. In addition, a small average particle size may lead to a drawback of low durability. On the other hand, when the average particle size is 20 μm or less, it tends to be suitable for high-speed charge / discharge. Furthermore, the average particle diameter is preferably 2 to 15 μm, more preferably 3 to 10 μm.

[Negative electrode active material]
The negative electrode active material contained in the negative electrode current collector is a carbon material that can occlude and release lithium ions. In addition to the carbon material, the negative electrode current collector can contain other materials that occlude and release lithium ions, such as lithium titanium composite oxides and conductive polymers. Examples of the carbon material include non-graphitizable carbon, graphitizable carbon, and composite porous material.

  More preferably, the negative electrode active material is a composite porous material formed by depositing a carbon material on the surface of activated carbon, and is derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method in the composite porous material. When the amount of mesopores to be obtained is Vm1 (cc / g) and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is Vm2 (cc / g), 0.010 ≦ Vm1 ≦ 0.250, The material satisfies 0.001 ≦ Vm2 ≦ 0.200 and 1.5 ≦ Vm1 / Vm2 ≦ 20.0.

  The negative electrode active material may be used alone or in combination of two or more.

  The composite porous material can be obtained, for example, by heat-treating activated carbon and a carbon material precursor in the coexistence state.

  Regarding the activated carbon used as a raw material for the composite porous material, as long as the obtained composite porous material exhibits desired characteristics, there are no particular restrictions on the raw material for obtaining the activated carbon, and petroleum-based, coal-based, plant-based, Commercial products obtained from various raw materials such as molecular systems can be used. In particular, it is preferable to use activated carbon powder having an average particle diameter of 1 μm or more and 15 μm or less. The average particle diameter is more preferably 2 μm or more and 10 μm or less. In addition, the measuring method of the said average particle diameter is the same as the measuring method used for the average particle diameter of the activated carbon which is the above-mentioned positive electrode active material.

  On the other hand, a carbon material precursor used as a raw material for the composite porous material is an organic material that can be dissolved in a solid, liquid, or solvent, which can be subjected to heat treatment to deposit the carbon material on activated carbon. Examples thereof include synthetic resins such as pitch, mesocarbon microbeads, coke, and phenol resin. Among these carbon material precursors, it is preferable in terms of production cost to use an inexpensive pitch. Pitch is roughly divided into petroleum pitch and coal pitch. Examples of petroleum pitches include crude oil distillation residue, fluid catalytic cracking residue (decant oil, etc.), bottom oil derived from thermal crackers, ethylene tar obtained during naphtha cracking, and the like.

  When the pitch is used, the composite porous material is obtained by depositing a carbon material on the activated carbon by thermally reacting the volatile component or pyrolysis component of the pitch on the surface of the activated carbon. In this case, at a temperature of about 200 to 500 ° C., the deposition of pitch volatile components or pyrolysis components into the activated carbon pores proceeds, and at 400 ° C. or higher, the reaction in which the deposited components become carbon materials proceeds. . The peak temperature during the heat treatment is appropriately determined according to the characteristics of the composite porous material to be obtained, the thermal reaction pattern, the thermal reaction atmosphere, etc., but is preferably 400 ° C. or higher, more preferably 450 ° C. to 1000 ° C. More preferably, the peak temperature is about 500 to 800 ° C. Moreover, the time which maintains the peak temperature at the time of heat processing should just be 30 minutes-10 hours, Preferably they are 1 hour-7 hours, More preferably, they are 2 hours-5 hours. For example, when the heat treatment is performed for 2 hours to 5 hours at a peak temperature of about 500 to 800 ° C., the carbon material deposited on the activated carbon surface is considered to be a polycyclic aromatic hydrocarbon.

  Examples of the method for producing the composite porous material include a method in which activated carbon is heat-treated in an inert atmosphere containing a hydrocarbon gas volatilized from a carbon material precursor, and the carbon material is deposited in a gas phase. In addition, a method in which activated carbon and a carbon material precursor are mixed and heat-treated in advance, or a method in which a carbon material precursor dissolved in a solvent is applied to activated carbon and dried and then heat-treated is also possible.

  The composite porous material is obtained by depositing a carbon material on the surface of activated carbon, but the pore distribution after the carbon material is deposited inside the pores of activated carbon is important. It can be defined by the amount of pores. In the present invention, the ratio of mesopore amount / micropore amount is particularly important as well as the absolute values of mesopore amount and micropore amount. That is, in one embodiment of the present invention, the amount of mesopores derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method in the composite porous material is Vm1 (cc / g), and the diameter of 20 mm calculated by the MP method is used. When the amount of micropores derived from pores less than Vm2 (cc / g) is 0.010 ≦ Vm1 ≦ 0.250, 0.001 ≦ Vm2 ≦ 0.200, and 1.5 ≦ Vm1 / Vm2 ≦ 20.0 is preferred.

  The mesopore amount Vm1 is more preferably 0.010 ≦ Vm1 ≦ 0.225, and further preferably 0.010 ≦ Vm1 ≦ 0.200. About micropore amount Vm2, 0.001 <= Vm2 <= 0.150 is more preferable, and 0.001 <= Vm2 <= 0.100 is still more preferable. The ratio of mesopore amount / micropore amount is more preferably 1.5 ≦ Vm1 / Vm2 ≦ 15.0, and further preferably 1.5 ≦ Vm1 / Vm2 ≦ 10.0. If the mesopore volume Vm1 is less than or equal to the upper limit (Vm1 ≦ 0.250), high charge / discharge efficiency with respect to lithium ions can be maintained, and the mesopore volume Vm1 and the micropore volume Vm2 are equal to or greater than the lower limit (0.010 ≦ Vm1, 0. If 001 ≦ Vm2), high output characteristics can be obtained.

  In addition, since mesopores with a large pore diameter have higher ionic conductivity than micropores, a mesopore amount is necessary to obtain high output characteristics. Since impurities such as moisture, which are thought to adversely affect the properties, are difficult to desorb, it is considered necessary to control the amount of micropores in order to obtain high durability. Therefore, it is important to control the ratio between the amount of mesopores and the amount of micropores. When the ratio is equal to or higher than the lower limit (1.5 ≦ Vm1 / Vm2), that is, the carbon material adheres more to the micropores than the mesopores of activated carbon. When the composite porous material after deposition has a large amount of mesopores and a small amount of micropores, high energy density, high output characteristics and high durability (cycle characteristics, float characteristics, etc.) can be obtained. When the ratio between the mesopore amount and the micropore amount is not more than the upper limit (Vm1 / Vm2 ≦ 20.0), high output characteristics can be obtained.

  In the present invention, the method for measuring the mesopore volume Vm1 and the micropore volume Vm2 is the same as that for the positive electrode active material described above.

  In one embodiment of the present invention, as described above, the mesopore / micropore ratio after the carbon material is deposited on the surface of the activated carbon is important. In order to obtain a composite porous material having a pore distribution range defined in the present invention, the pore distribution of activated carbon used as a raw material is important.

  In the activated carbon used for forming the composite porous material as the negative electrode active material, the mesopore amount derived from the pores having a diameter of 20 to 500 mm calculated by the BJH method is V1 (cc / g), the diameter calculated by the MP method. When the amount of micropores derived from pores less than 20 mm is V2 (cc / g), 0.050 ≦ V1 ≦ 0.500, 0.005 ≦ V2 ≦ 1.000, and 0.2 ≦ V1 / V2 It is preferable that ≦ 20.0.

  About mesopore amount V1, 0.050 <= V1 <= 0.350 is more preferable, and 0.100 <= V1 <= 0.300 is still more preferable. The micropore amount V2 is more preferably 0.005 ≦ V2 ≦ 0.850, and further preferably 0.100 ≦ V2 ≦ 0.800. The ratio of mesopore amount / micropore amount is more preferably 0.22 ≦ V1 / V2 ≦ 15.0, and further preferably 0.25 ≦ V1 / V2 ≦ 10.0. When the mesopore volume V1 of the activated carbon is 0.500 or less and when the micropore volume V2 is 1.000 or less, an appropriate amount is required to obtain the pore structure of the composite porous material of one embodiment of the present invention. Since it is sufficient to deposit a carbon material, the pore structure tends to be easily controlled. On the other hand, when the mesopore amount V1 of the activated carbon is 0.050 or more, when the micropore amount V2 is 0.005 or more, when V1 / V2 is 0.2 or more, and V1 / V2 is 20.0. In the following cases, the pore structure of the composite porous material of one embodiment of the present invention tends to be easily obtained from the pore distribution of the activated carbon.

  The average particle size of the composite porous material in the present invention is preferably 1 μm or more and 10 μm or less. About a lower limit, More preferably, it is 2 micrometers or more, More preferably, it is 2.5 micrometers or more. About an upper limit, More preferably, it is 6 micrometers or less, More preferably, it is 4 micrometers or less. If the average particle size is 1 μm or more and 10 μm or less, good durability is maintained. The measurement method of the average particle diameter of said composite porous material is the same as the measurement method used for the average particle diameter of the activated carbon of the above-mentioned positive electrode active material.

  In the above composite porous material, the atomic ratio of hydrogen atoms / carbon atoms (hereinafter also referred to as H / C) is preferably 0.05 or more and 0.35 or less, and 0.05 or more and 0.15. The following is more preferable. When H / C is 0.35 or less, the structure (typically polycyclic aromatic conjugated structure) of the carbon material deposited on the activated carbon surface is sufficiently developed, so the capacity (energy density) ) And charging / discharging efficiency is high. On the other hand, when H / C is 0.05 or more, since carbonization does not proceed excessively, a sufficient energy density can be obtained. H / C is measured by an elemental analyzer.

In addition, the composite porous material usually has an amorphous structure derived from the activated carbon as a raw material and a crystal structure mainly derived from the deposited carbon material. According to the X-ray wide angle diffraction method, the composite porous material preferably has a structure with low crystallinity in order to exhibit high output characteristics, and has a structure with high crystallinity in order to maintain reversibility in charge and discharge. From the (002) plane spacing d ₀₀₂ is 3.60 to 4.00 mm, and the crystallite size Lc in the c-axis direction obtained from the half width of this peak is 8.0 to 20.0 mm. Some are preferable, d ₀₀₂ is 3.60 to 3.75 Å, and the crystallite size Lc in the c-axis direction obtained from the half width of this peak is 11.0 to 16.0 よ り. preferable.

[Other components]
In an embodiment of the present invention, the nonaqueous lithium-type energy storage device includes a current collector, a component other than the active material in the active material layer, an electrode body, and a separator in addition to the above-described electrolyte solution, positive electrode active material, and negative electrode active material. Including exterior bodies. Hereinafter, these components will be described.

(Current collector)
The current collector is usually a metal foil that does not deteriorate such as elution and reaction in a power storage element. There is no restriction | limiting in particular as this metal foil, For example, copper foil, aluminum foil, etc. are mentioned. In the electricity storage device of the present invention, the positive electrode current collector is preferably an aluminum foil and the negative electrode current collector is preferably a copper foil.

  Further, the current collector may be a normal metal foil having no through hole or a metal foil having a through hole. The thickness of the current collector is not particularly limited but is preferably 1 to 100 μm. The thickness of the current collector of 1 μm or more is preferable because the shape and strength of the electrode body (positive electrode and negative electrode in the present invention) formed by fixing the active material layer to the current collector can be maintained. On the other hand, it is preferable that the current collector has a thickness of 100 μm or less because the weight and volume of the electricity storage element are appropriate and the performance per weight and volume tends to be high.

(Ingredients other than the active material in the active material layer)
As the active material layer, a known component contained in the active material layer of a known lithium ion battery, a capacitor, or the like can be used. In addition to the above-described positive electrode active material or negative electrode active material, the active material layer can contain known components such as a binder, a conductive filler, a thickener, and the like, and the type thereof is not particularly limited. Hereinafter, the details of the components of the active material layer in the non-aqueous lithium storage element will be described.

  The active material layer can contain a conductive filler, such as carbon black, if necessary. 0-30 mass parts is preferable with respect to 100 mass parts of active materials, and, as for the usage-amount of an electroconductive filler, 1-20 mass parts is more preferable. The conductive filler is preferably used from the viewpoint of high power density, but when the amount used is 30 parts by mass or less, the proportion of the amount of the active material in the active material layer is high, and the output per volume is high. This is preferable because the density tends to increase.

  In order to fix the above-mentioned active material and further the conductive filler used as necessary on the current collector as an active material layer, as a binder, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), fluorine Rubber, styrene butadiene copolymer, cellulose derivative and the like can be used. The amount of the binder used is preferably in the range of 3 to 20 parts by mass and more preferably in the range of 5 to 15 parts by mass with respect to 100 parts by mass of the active material. When the amount of the binder used is 20 parts by mass or less, since the binder does not cover the surface of the active material, ions can enter and exit quickly, and high power density tends to be obtained, which is preferable. On the other hand, when the usage-amount of a binder is 3 mass parts or more, since there exists a tendency which becomes easy to adhere an active material layer on a collector, it is preferable.

  The electrode body in the present invention may be one in which the active material layer is formed only on the upper surface (one surface) of the current collector or the upper and lower surfaces (both surfaces).

(Electrode body)
The electrode body is formed by fixing an active material layer to a current collector. In the electrode body, the thickness of the active material layer is usually preferably about 30 to 200 μm. It is preferable that the thickness of the active material layer be 30 μm or more because the ratio of the amount of active material to the entire power storage element increases and the energy density tends to increase. On the other hand, it is preferable that the thickness of the active material layer is 200 μm or less because the resistance inside the electrode is reduced and the output density tends to increase.

  The electrode body can be manufactured by an electrode manufacturing technique such as a known lithium ion battery or an electric double layer capacitor. For example, various materials including an active material are slurried with water or an organic solvent, and the active material layer is formed. It is obtained by coating on a current collector, drying, and pressing as necessary. Further, various materials including an active material can be dry-mixed without using a solvent, the active material can be press-molded, and then attached to the current collector using a conductive adhesive.

(Separator)
The formed positive electrode body and negative electrode body are laminated or wound around via a separator, and inserted into an outer package formed from a metal can or a laminated film. As the separator, a polyethylene microporous film or a polypropylene microporous film used in a lithium ion secondary battery, a cellulose nonwoven paper used in an electric double layer capacitor, or the like can be used.

  The thickness of the separator is preferably 10 μm or more and 50 μm or less. A thickness of 10 μm or more is preferable because self-discharge due to internal micro-shorts tends to be small. On the other hand, a thickness of 50 μm or less is preferable because the output characteristics of the storage element tend to be high.

(Exterior body)
A metal can, a laminate film, or the like can be used as the exterior body. The metal can is preferably made of aluminum. Moreover, as this laminate film, the film which laminated | stacked metal foil and the resin film is preferable, and the thing of the 3 layer structure which consists of an outer layer resin film / metal foil / interior resin film is illustrated. The outer layer resin film is for preventing the metal foil from being damaged by contact or the like, and a resin such as nylon or polyester can be suitably used. The metal foil is for preventing the permeation of moisture and gas, and foils of copper, aluminum, stainless steel and the like can be suitably used. The interior resin film protects the metal foil from the electrolyte contained therein and melts and seals it at the time of heat sealing. Polyolefin, acid-modified polyolefin, and the like can be suitably used.

(Lithium ion pre-doping method)
In the present invention, the negative electrode body can be previously doped with lithium ions. As a method for doping, a known method, for example, a method in which a negative electrode body is assembled in a state where a lithium metal foil is laminated on a negative electrode active material layer, and this is put in a nonaqueous electrolytic solution can be used. By doping with lithium ions, the capacity and operating voltage of the power storage element can be controlled.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

<Example 1>
[Preparation of positive electrode body]
The crushed palm shell carbide was carbonized in nitrogen in a small carbonization furnace at 500 ° C. for 3 hours. The treated carbide is placed in an activation furnace, 1 kg / h of steam is heated in a preheating furnace, and the temperature is raised to 900 ° C. over 8 hours. To obtain activated carbon. The obtained activated carbon was washed with water for 10 hours and then drained. Then, after drying for 10 hours in an electric dryer maintained at 115 ° C., pulverization was performed for 1 hour with a ball mill to obtain activated carbon 1. It was 4.2 micrometers as a result of measuring an average particle diameter using the Shimadzu Corporation laser diffraction type particle size distribution measuring device (SALD-2000J). In addition, the pore distribution was measured with a pore distribution measuring apparatus (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 2360 m ² / g, the mesopore volume (V1) was 0.52 cc / g, and the micropore volume (V2) was 0.88 cc / g.

  80.8 parts by mass of activated carbon 1, 6.2 parts by mass of ketjen black, 10 parts by mass of PVDF (polyvinylidene fluoride), 3.0 parts by mass of PVP (polyvinylpyrrolidone), and NMP (N-methylpyrrolidone) Mixing to obtain a slurry. Next, the obtained slurry was applied to one side of an aluminum foil having a thickness of 15 μm, dried, and pressed to obtain a positive electrode body having an active material layer thickness of 55 μm.

[Preparation of negative electrode body]
With respect to commercially available coconut shell activated carbon, the pore distribution was measured using nitrogen as an adsorbate with a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. The specific surface area was determined by the BET single point method. Further, as described above, using the isotherm on the desorption side, the mesopore amount was determined by the BJH method, and the micropore amount was determined by the MP method. As a result, the BET specific surface area was 1,780 m ² / g, the mesopore volume was 0.198 cc / g, the micropore volume was 0.695 cc / g, V1 / V2 = 0.29, and the average pore diameter was 21.2 mm. there were.

150 g of this coconut shell activated carbon is placed in a stainless steel mesh jar and placed on a stainless steel bat containing 270 g of a coal-based pitch (softening point: 50 ° C.). It installed in and performed the heat reaction. Heat treatment is performed in a nitrogen atmosphere by raising the temperature to 600 ° C. in 8 hours and holding at that temperature for 4 hours. Subsequently, after cooling to 60 ° C. by natural cooling, the composite porous material that is taken out from the furnace and becomes a negative electrode material The material 1 was obtained. When the obtained composite porous material 1 was measured in the same manner as the activated carbon 1, the BET specific surface area was 262 m ² / g, the mesopore volume (Vm1) was 0.1798 cc / g, and the micropore volume (Vm2) was 0.00. 0843 cc / g and Vm1 / Vm2 = 2.13.

  83.4 parts by mass of the composite porous material 1, 8.3 parts by mass of acetylene black, 8.3 parts by mass of PVDF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) are mixed to prepare a slurry. Obtained. Next, the obtained slurry was applied to one side of a copper foil having a thickness of 15 μm, dried and pressed to obtain a negative electrode body having an active material layer thickness of 60 μm. The electrode body was electrochemically doped with lithium ions corresponding to 760 mAh / g per unit weight of the composite porous material 1 using a lithium metal foil.

[Preparation of electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC), and 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (EMI.TFSI) which is a room temperature molten salt in a volume ratio of 16:64:20 A solution obtained by dissolving LiPF ₆ in a mixed solvent solution at a concentration of 1 mol / l was used as an electrolytic solution. At this time, the proportion of the mixed solvent of the room temperature molten salt is 20% by volume.

[Assembly and performance of storage element]
A cellulose nonwoven fabric separator (thickness: 30 μm) is laminated between the obtained negative electrode body and the positive electrode body, inserted into an exterior body formed from a laminate film, and the electrolyte solution is injected into the exterior body. Was sealed, and a non-aqueous lithium storage element was assembled.

  The produced power storage device was evaluated in a 25 ° C. environment. The battery was charged to 4.0 V with a current amount of 1.5 C, and then subjected to constant current constant voltage charging in which a constant voltage of 4.0 V was applied for 2 hours. Subsequently, the battery was discharged to 2.0 V with a current amount of 1.5 C. Next, the characteristics were evaluated in an environment of −30 ° C. The same charge as the above was performed, and the battery was discharged to 2.0 V with a current amount of 500C. The ratio of the discharge capacity at 500 C at -30 ° C. to the discharge capacity at 1.5 C at 25 ° C. was 11%.

  Further, a high temperature durability test was performed at 60 ° C. under the condition of 4.0 V application. The capacity retention rate and resistance magnification at the start of the test (0 h) and after 1000 h had been measured. The capacity retention rate (%) here is a numerical value represented by {(discharge capacity after elapse of 1000 h) / (discharge capacity at 0 h)} × 100 in the discharge capacity at a current amount of 1.5 C. is there. The resistance magnification is a numerical value represented by (resistance value at 0.1 Hz after elapse of 1000 h) / (resistance value at 0.1 Hz at 0 h). After 1000 hours, the capacity retention rate was 97%, and the resistance magnification was 1.6.

<Example 2>
[Preparation of positive electrode body]
It was produced in the same manner as in Example 1.

[Preparation of negative electrode body]
It was produced in the same manner as in Example 1.

[Preparation of electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC), and 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (EMI.TFSI), which is a room temperature molten salt, at a volume ratio of 10:40:50 A solution obtained by dissolving LiPF ₆ in a mixed solvent solution at a concentration of 1 mol / l was used as an electrolytic solution. At this time, the proportion of the mixed solvent of the room temperature molten salt is 50% by volume.

[Assembly and performance of storage element]
A non-aqueous lithium storage element was assembled in the same manner as in Example 1.
As a result of evaluating the produced storage element in the same manner as in Example 1, the ratio of the discharge capacity at -30 ° C. at 500 C to the discharge capacity at 25 ° C. at 1.5 C was 8.5%. Further, the capacity retention rate after elapse of 1000 hours was 97%, and the resistance magnification was 1.4.

<Example 3>
[Preparation of positive electrode body]
It was produced in the same manner as in Example 1.

[Preparation of negative electrode body]
It was produced in the same manner as in Example 1.

[Preparation of electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC), and 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (EMI.TFSI) which is a room temperature molten salt in a volume ratio of 6:24:70 A solution obtained by dissolving LiPF ₆ in a mixed solvent solution at a concentration of 1 mol / l was used as an electrolytic solution. At this time, the proportion of the mixed solvent of the room temperature molten salt is 70% by volume.

[Assembly and performance of storage element]
A non-aqueous lithium storage element was assembled in the same manner as in Example 1.
As a result of evaluating the produced power storage element in the same manner as in Example 1, the ratio of the discharge capacity at 500 C at -30 ° C. to the discharge capacity at 1.5 C at 25 ° C. was 6.3%. In addition, the capacity retention rate after 1000 hours was 98%, and the resistance magnification was 1.35.

<Example 4>
[Preparation of positive electrode body]
It was produced in the same manner as in Example 1.

[Preparation of negative electrode body]
It was produced in the same manner as in Example 1.

[Preparation of electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC) and room temperature molten salt 1,3-diethylimidazolium p-toluenesulfonate (EEI p-toluenesulfonate) at a volume ratio of 16:64:20 A solution obtained by dissolving LiPF ₆ in a mixed solvent solution at a concentration of 1 mol / l was used as an electrolytic solution. At this time, the proportion of the mixed solvent of the room temperature molten salt is 20% by volume.

[Assembly and performance of storage element]
A non-aqueous lithium storage element was assembled in the same manner as in Example 1.
As a result of evaluating the produced electric storage element in the same manner as in Example 1, the ratio of the discharge capacity at −30 ° C. at 500 C to the discharge capacity at 25 ° C. at 1.5 C was 10%. Further, the capacity retention rate after elapse of 1000 hours was 97%, and the resistance magnification was 1.6.

<Example 5>
[Preparation of positive electrode body]
It was produced in the same manner as in Example 1.

[Preparation of negative electrode body]
It was produced in the same manner as in Example 1.

[Preparation of electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC) and room temperature molten salt 1,3-diethylimidazolium p-toluenesulfonate (EEI p-toluenesulfonate) at a volume ratio of 10:40:50 A solution obtained by dissolving LiPF ₆ in a mixed solvent solution at a concentration of 1 mol / l was used as an electrolytic solution. At this time, the proportion of the mixed solvent of the room temperature molten salt is 50% by volume.

[Assembly and performance of storage element]
A non-aqueous lithium storage element was assembled in the same manner as in Example 1.
As a result of evaluating the produced power storage element in the same manner as in Example 1, the ratio of the discharge capacity at -30 ° C. at 500 C to the discharge capacity at 25 ° C. at 1.5 C was 7.8%. Moreover, the capacity retention rate after the lapse of 1000 hours was 97%, and the resistance magnification was 1.35.

<Example 6>
[Preparation of positive electrode body]
It was produced in the same manner as in Example 1.

[Preparation of negative electrode body]
It was produced in the same manner as in Example 1.

[Preparation of electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC) and room temperature molten salt 1,3-diethylimidazolium p-toluenesulfonate (EEI p-toluenesulfonate) in a volume ratio of 6:24:70 A solution obtained by dissolving LiPF ₆ in a mixed solvent solution at a concentration of 1 mol / l was used as an electrolytic solution. At this time, the proportion of the mixed solvent of the room temperature molten salt is 70% by volume.

[Assembly and performance of storage element]
A non-aqueous lithium storage element was assembled in the same manner as in Example 1.
As a result of evaluating the produced power storage element in the same manner as in Example 1, the ratio of the discharge capacity at −30 ° C. at 500 C to the discharge capacity at 25 ° C. at 1.5 C was 6.0%. In addition, the capacity retention rate after 1000 hours was 98%, and the resistance magnification was 1.35.

<Example 7>
[Preparation of positive electrode body]
It was produced in the same manner as in Example 1.

[Preparation of negative electrode body]
It was produced in the same manner as in Example 1.

[Preparation of electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC), and N-butylpyridinium tetrafluoroborate (BPy · BF ₄ ), which is a room temperature molten salt, in a mixed solvent solution having a volume ratio of 16:64:20, 1 mol / A solution obtained by dissolving LiPF ₆ at a concentration of 1 was used as the electrolyte. At this time, the proportion of the mixed solvent of the room temperature molten salt is 20% by volume.

[Assembly and performance of storage element]
A non-aqueous lithium storage element was assembled in the same manner as in Example 1.
As a result of evaluating the produced electric storage element in the same manner as in Example 1, the ratio of the discharge capacity at −30 ° C. at 500 C to the discharge capacity at 25 ° C. at 1.5 C was 10%. In addition, the capacity retention rate after 1000 hours was 97%, and the resistance magnification was 1.65.

<Example 8>
[Preparation of positive electrode body]
It was produced in the same manner as in Example 1.

[Preparation of negative electrode body]
It was produced in the same manner as in Example 1.

[Preparation of electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC), and N-butylpyridinium tetrafluoroborate (BPy · BF ₄ ), which is a room temperature molten salt, in a mixed solvent solution having a volume ratio of 10:40:50, 1 mol / A solution obtained by dissolving LiPF ₆ at a concentration of 1 was used as the electrolyte. At this time, the proportion of the mixed solvent of the room temperature molten salt is 50% by volume.

[Assembly and performance of storage element]
A non-aqueous lithium storage element was assembled in the same manner as in Example 1.
As a result of evaluating the produced electric storage element in the same manner as in Example 1, the ratio of the discharge capacity at -30 ° C. at 500 C to the discharge capacity at 25 ° C. at 1.5 C was 8.0%. Further, the capacity retention rate after elapse of 1000 hours was 97%, and the resistance magnification was 1.4.

<Example 9>
[Preparation of positive electrode body]
It was produced in the same manner as in Example 1.

[Preparation of negative electrode body]
It was produced in the same manner as in Example 1.

[Preparation of electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC), and N-butylpyridinium tetrafluoroborate (BPy · BF ₄ ), which is a room temperature molten salt, in a mixed solvent liquid having a volume ratio of 6:24:70, 1 mol / A solution obtained by dissolving LiPF ₆ at a concentration of 1 was used as the electrolyte. At this time, the proportion of the mixed solvent of the room temperature molten salt is 70% by volume.

[Assembly and performance of storage element]
A non-aqueous lithium storage element was assembled in the same manner as in Example 1.
As a result of evaluating the produced power storage element in the same manner as in Example 1, the ratio of the discharge capacity at -30 ° C. at 500 C to the discharge capacity at 1.5 C at 25 ° C. was 6.5%. Further, the capacity retention after 1000 hours was 98%, and the resistance magnification was 1.3.

<Comparative Example 1>
[Preparation of positive electrode body]
It was produced in the same manner as in Example 1.

[Preparation of negative electrode body]
It was produced in the same manner as in Example 1.

[Preparation of electrolyte]
A solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / l in a mixed solvent solution of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) in a volume ratio of 20:80 without adding room temperature molten salt. Used as electrolyte.

[Assembly and performance of storage element]
A non-aqueous lithium storage element was assembled in the same manner as in Example 1.
As a result of evaluating the produced electric storage element in the same manner as in Example 1, the ratio of the discharge capacity at -30 ° C. at 500 C to the discharge capacity at 25 ° C. at 1.5 C was 3.0%. Further, the capacity retention rate after 1000 hours was 95%, and the resistance magnification was 1.8.

  As mentioned above, it turns out that the electrical storage element which concerns on this invention is excellent in a low temperature characteristic and high temperature durability.

  The non-aqueous lithium storage element of the present invention can be suitably used in, for example, the field of a hybrid drive system that combines an internal combustion engine or a fuel cell, a motor, and a storage element in an automobile, and further assists for instantaneous power peak. .

Claims (7)

  A negative electrode body in which a negative electrode active material layer including a negative electrode active material is provided on a negative electrode current collector, a positive electrode body in which a positive electrode active material layer including a positive electrode active material is provided on a positive electrode current collector, and an electrode formed by laminating a separator A non-aqueous lithium-type energy storage device comprising a laminate and a non-aqueous electrolyte solution containing an electrolyte containing lithium ions in an outer package, wherein the negative electrode active material is a carbon material capable of occluding and releasing lithium ions, The positive electrode active material is activated carbon, and the non-aqueous electrolyte solution is composed of a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent at a concentration of 0.5 mol / L or more, and the non-aqueous solvent is a cyclic quaternary. A room temperature molten salt formed from an ammonium organic cation and an anion composed of a non-metallic element, and a cyclic carbonate and a chain carbonate, and the content of the room temperature molten salt is the room temperature molten salt, the cyclic salt The total volume of Boneto and the chain carbonate is 20 vol% to 70 vol%, the non-aqueous lithium-type storage element.   The non-aqueous lithium storage element according to claim 1, wherein the cyclic quaternary ammonium organic cation contains at least one of an imidazolium cation and a pyridinium cation.   The cyclic quaternary ammonium organic cation includes 1-ethyl-3-methylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, 1,3-diethylimidazolium ion, 1-butyl-3-methylimidazole. The non-aqueous lithium storage element according to claim 2, comprising at least one selected from a lithium ion or an N-butylpyridinium ion. The non-aqueous lithium storage element according to claim 1, wherein the lithium salt contains lithium hexafluorophosphate (LiPF ₆ ) and / or lithium borofluoride (LiBF ₄ ). The anion in the non-aqueous electrolyte includes at least one kind of anion other than hexafluorophosphate ion (PF ₆ ⁻ ) and the hexafluorophosphate ion according to claim 1. Non-aqueous lithium storage element. The negative electrode active material is a composite porous material in which a carbon material is deposited on the surface of activated carbon, and the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is Vm1 (cc / g ), When the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is Vm2 (cc / g),
0.010 ≦ Vm1 ≦ 0.250,
The non-aqueous lithium storage element according to claim 1, wherein 0.001 ≦ Vm2 ≦ 0.200 and 1.5 ≦ Vm1 / Vm2 ≦ 20.0 are satisfied. In the positive electrode active material, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method. Is V2 (cc / g),
It is activated carbon that satisfies 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0, and has a specific surface area measured by the BET method of 1500 m ² / g or more and 3000 m ² / g or less. Item 7. The non-aqueous lithium storage element according to any one of Items 1 to 6.