WO2019065151A1

WO2019065151A1 - Non-aqueous secondary cell, non-aqueous electrolyte used in same, and method for manufacturing non-aqueous secondary cell

Info

Publication number: WO2019065151A1
Application number: PCT/JP2018/033101
Authority: WO
Inventors: 喜多房次; 水野悠
Original assignee: マクセルホールディングス株式会社; 三井化学株式会社
Priority date: 2017-09-29
Filing date: 2018-09-06
Publication date: 2019-04-04
Also published as: JPWO2019065151A1; JP7069189B2

Abstract

The purpose of the present invention is to provide a non-aqueous secondary cell having exceptional charge/discharge cycle characteristics at a high voltage, a non-aqueous electrolyte used in the non-aqueous secondary cell, and a method for manufacturing the non-aqueous secondary cell. This non-aqueous secondary cell comprises a positive electrode, a negative electrode, and a non-aqueous electrolyte. When the positive electrode, after charging is performed to 4.5 V with a 1/3 C current and then discharging is performed to 3 V with a 1/3 C current, is cleaned with methyl ethyl carbonate and then vacuum dried, and then the surface of the positive electrode is analyzed by X-ray photoelectron spectroscopy, Rf/Ro is 0.05-1.3 inclusive, or Rc/Ro is 0.05-0.75 inclusive, where Ro (atom%) represents the proportion of oxygen atoms, Rf (atom%) represents the proportion of fluorine atoms, and Rc (atom%) represents the proportion of carbon atoms in which the binding energy of the 1s orbit is 289-291 eV, said atoms being contained at the surface of the positive electrode.

Description

Non-aqueous secondary battery, non-aqueous electrolyte used therefor, and method of manufacturing the non-aqueous secondary battery

The present invention relates to a non-aqueous secondary battery, a non-aqueous electrolyte used therefor, and a method of manufacturing the non-aqueous secondary battery.

In recent years, with the development of portable electronic devices such as mobile phones and notebook personal computers, and the commercialization of electric vehicles, etc., secondary batteries of small size, light weight, high capacity and high energy density are required. It is coming.

Currently, non-aqueous secondary battery capable of meeting this requirement, especially in the lithium-ion battery, the positive electrode active material in the lithium cobalt oxide (Li _x CoO _2), lithium nickelate (Li _x NiO _2), nickel - cobalt - lithium manganate _{_{_{with: (Li x Ni y1 Co y2}}} Mn y3 O 2 0.9 <x <1.1,0 <y1 ~ 3 <1, y1 + y2 + y3 = 1) lithium-containing composite oxide or a composite thereof and mixtures of such Graphite or the like is used as the negative electrode active material. And with the further development of the applicable equipment of the non-aqueous secondary battery, the further high capacity-ization and high energy density formation of the non-aqueous secondary battery are calculated | required.

One of methods for achieving high capacity and high energy density of the non-aqueous secondary battery is to charge the positive electrode active material with high voltage and use it. However, with the increase in energy density and voltage of non-aqueous secondary batteries, the decrease in charge-discharge cycle characteristics of the batteries has become remarkable.

In the past, in order to suppress the decrease in charge-discharge cycle characteristics under high voltage, it has been proposed to make the positive electrode active material form a solid solution of different metals and coat the surface of the positive electrode with metal oxide. There is a problem that the stability is poor and the film is degraded due to the interaction between the film and the electrolyte. Further, for the same purpose, various studies have been made to coat the surface of the positive electrode with an organic substance, an alkali metal salt or an alkaline earth salt. However, in the case of a film made of an organic compound, unless a film is generally formed using a high voltage resistant material such as a fluorine compound, it can not withstand use as a film for high voltage. In addition, since a film made of an organic compound is easily swollen by the electrolytic solution, it is considered that the film effect of blocking the electrolytic solution and the positive electrode is low. Furthermore, when the coating is formed of an alkali metal salt or an alkaline earth salt, the coating is easily dissolved in the electrolytic solution, and the coating tends to absorb the electrolytic solution, and there is a problem that the coating effect is reduced.

For example, Non-Patent Document 1 describes an example in which a positive electrode active material is coated with an inorganic oxide. Thereby, the side reaction of the active material can be suppressed, but there is a possibility that the electron conductivity of the surface of the active material is inhibited. Patent Document 1 describes an example in which the surface of an active material is coated with a polyvalent fluorine-containing organic lithium salt, and by covering with a fluorine compound that is resistant to high voltage, the electrolyte is subjected to high voltage. Although the reaction is suppressed, it is not a simple method, and there is also concern about an increase in resistance. Patent Document 2 proposes that a protective film material is added to the positive electrode paint, and a thermally actuated protective film is formed on the surface of the positive electrode material to improve the safety of the battery. Due to the addition, the resistance of the electrode may be increased. Although Patent Document 3 proposes that a porous protective film is formed on the surface of an electrode (in particular, a negative electrode), it is considered to be less effective in suppressing the reaction between an electrolytic solution and a positive electrode because it is porous. Moreover, the specific example which forms a protective film in the positive electrode surface in patent document 3 is not described.

Also, conventionally, various electrolyte additives have been studied to ensure safety. Cyclohexylbenzene, biphenyl, etc. are representative examples, but in a battery of the type in which the battery is charged to a high voltage of about 4.35 V, the additive reacts in the normal state of charge, and in practical use In many cases, additives can not be used. Also, even with normal 4.2 V charging, some of the additives react to affect the battery performance. Therefore, there is a need for an electrolytic solution additive that can be used even under high voltage and can ensure safety.

Patent Document 4 proposes a non-aqueous secondary battery which can be used even under high voltage, and describes the use of a compound having two or more nitrile groups in the molecule as an electrolytic solution additive of the battery, Specifically, the use of dinitriles such as succinonitrile is described. On the other hand, in Patent Document 4, in consideration of the reactivity of the electrode, the addition amount of the compound having two or more nitrile groups in the molecule is in a desirable range of 1% by mass or less.

Further, Patent Document 5 proposes a non-aqueous electrolyte secondary battery using a dinitrile such as glutaronitrile at a high concentration as an electrolyte additive. Although Patent Document 5 describes the improvement of charge and discharge cycle characteristics, evaluation of the charge and discharge cycle characteristics is performed using lithium metal as a counter electrode, and there is a problem in the reaction of the negative electrode. In general, nitriles have an effect of suppressing battery swelling and the like, but there is a problem in the reactivity of the negative electrode, and it is known that the charge and discharge cycle characteristics also have a problem in our examination.

JP 2012-243696 A JP, 2010-157512, A JP, 2009-301765, A JP 2008-108586 A Unexamined-Japanese-Patent No. 9-161845 gazette

The present invention solves the above problems, and provides a non-aqueous secondary battery excellent in charge and discharge cycle characteristics at high voltage, a non-aqueous electrolyte used therefor, and a method of manufacturing the non-aqueous secondary battery. It is.

The first non-aqueous secondary battery of the present invention is a non-aqueous secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the surface of the positive electrode is at least one selected from Component 1, Component 2 and Component 3. It is characterized in that it is coated with one component, the component 1 is a sugar analog compound, the component 2 is a metal salt, and the component 3 is a nitrogen-containing compound.

The second non-aqueous secondary battery of the present invention is a non-aqueous secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolytic solution, and the non-aqueous electrolytic solution or the positive electrode contains a fluorine-containing compound or a carbonic acid compound. The non-aqueous electrolyte contains an additive other than vinylene carbonate, and the concentration of the additive in the non-aqueous electrolyte is 0.05% by mass or more and 3% by mass or less.

The non-aqueous electrolyte of the present invention is a non-aqueous electrolyte used in the non-aqueous secondary battery of the present invention, characterized in that it contains at least one selected from a fluorine-containing compound and a carbonic acid compound.

The first method for producing a non-aqueous secondary battery according to the present invention is a method for producing the non-aqueous secondary battery according to the present invention, wherein at least one component selected from Component 1, Component 2 and Component 3 And a step of applying the treatment liquid to the surface of the positive electrode, wherein the component 1 is a sugar analog compound, the component 2 is a metal salt, and the component 3 is a step of preparing the treatment solution A nitrogen-containing compound, and the positive electrode is a positive electrode after pressing.

The second method for producing a non-aqueous secondary battery according to the present invention is a method for producing the non-aqueous secondary battery according to the present invention, wherein at least one component selected from component 1, component 2 and component 3 Comprising the steps of: preparing a non-aqueous electrolyte containing the following; assembling a battery using the positive electrode, the negative electrode, and the non-aqueous electrolyte; and charging and discharging the assembled battery, wherein The compound is a compound, the component 2 is a metal salt, and the component 3 is a nitrogen-containing compound.

According to the present invention, it is possible to provide a non-aqueous secondary battery excellent in charge and discharge cycle characteristics at high voltage, a non-aqueous electrolyte used therefor, and a method of manufacturing the non-aqueous secondary battery.

FIG. 1 is a plan view showing an example of the non-aqueous secondary battery.

(First Embodiment of Nonaqueous Secondary Battery)
The first embodiment of the non-aqueous secondary battery of the present invention comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, and the surface of the positive electrode is coated with at least one component selected from component 1, component 2 and component 3. The component 1 is a sugar analog compound, the component 2 is a metal salt, and the component 3 is a nitrogen-containing compound.

By coating the surface of the positive electrode with the above components, a stable film can be formed on the surface of the positive electrode even under high voltage, and the contact between the positive electrode and the non-aqueous electrolyte can be reduced to perform charge and discharge cycles under high voltage. Characteristics can be improved.

In addition, the present inventors consider coating the surface of the positive electrode with the above components, and by setting the surface of the positive electrode to a specific surface state, the additive effect of the electrolytic solution can be further improved, which is high. It was confirmed that the charge and discharge cycle characteristics under voltage could be improved with certainty. Specifically, after charging the battery to 4.5 V with a 1/3 C current, the positive electrode after discharging to 3 V with a 1/3 C current is washed with methylethyl carbonate and then vacuum dried, and then the above When the surface of the positive electrode is analyzed by X-ray photoelectron spectroscopy, the content ratio of oxygen atoms is Ro (atomic%), the content ratio of fluorine atoms is Rf (atomic%), and the binding energy of 1s orbital on the surface of the positive electrode Rf / Ro is 0.05 or more and 1.3 or less, or Rc / Ro is 0.05 or more and 0.75 or less, where Rc (atomic%) is a carbon atom content ratio of 289 to 291 eV The surface condition proved to be favorable.

Hereinafter, each element of this embodiment will be described in detail.

<Component 1, Component 2 and Component 3>
Conventionally, high voltage resistant fluorine-based compounds that are difficult to react under high voltage have been widely used as substances to be contained in the electrolyte solution and the electrode when the charge voltage of the battery exceeds 4.2 V in lithium standard . On the other hand, as a result of studies by the present inventors, compounds containing nitrogen atoms that are easily reacted at high voltages, and polymers having OH groups that have been considered undesirable for use in batteries, etc. Was found to be highly effective in improving the charge and discharge cycle characteristics. Specifically, they are a sugar analog compound (component 1), a metal salt (component 2) and a nitrogen-containing compound (component 3). In particular, many of the sugar analogues (component 1) have an OH group, and the nitrogen-containing compounds (component 3) have a nitrogen atom moiety which is susceptible to oxidation, and conventionally they are used under high voltage It is not usually used with the positive electrode. However, as a result of daringly examining substances that are not usually used in high voltage rechargeable batteries, the present inventors confirmed that they are effective in improving the charge and discharge cycle characteristics under high voltage. The components 1 to 3 exhibit the effect by containing the positive electrode as a component other than a binder, but the effect is exhibited particularly by causing the surface to be present in large amounts on the surface of the positive electrode, and the surface of the positive electrode is selected from component 1, component 2 and component 3. Coating with at least one component is most effective. Further, specific substances corresponding to the components 1 to 3 are preferably one substance and classified into a plurality of components, for example, magnesium lignin sulfonate is a sugar analog compound (component 1), and Since it is also a metal salt (component 2), it is a preferable component.

[Component 1]
Component 1 above is a sugar analog compound. The above sugar analogues include sugars and related substances. The above saccharides include monosaccharides such as glucose, polysaccharides such as sucrose, starch, amylose, amylopectin, glycogen, cellulose, pectin, glucomannan and the like. Also, α-, β-, γ-cyclodextrin, deoxyribose, fucose, rhamnose, glucuronic acid, galacturonic acid, glucosamine, galactosamine, glycerin, xylitol, sorbitol, ascorbic acid (vitamin C), glucuronolactone, gluconolactone Etc. are also included in the saccharides. Further, related substances of the above-mentioned saccharides include lignin, lignin derivative, alginic acid, alginate and the like which are compounds having a plurality of OH groups, and compounds having a plurality of OH groups include carboxymethylcellulose and hydroxymethylcellulose etc. .

As said saccharides, polysaccharides, such as sucrose, are desirable, As a compound which has multiple said OH groups, carboxymethylcellulose, hydroxymethylcellulose, lignin compounds (lignin, lignin derivative), alginic acid, and alginate are desirable.

The molecular weight of the above-mentioned sugar analog compound is preferably 200 or more, more preferably 500 or more, and most preferably 1000 or more so as to be difficult to dissolve in the electrolytic solution.

Although it is not clear why the compound having the originally unstable OH group is effective at high voltage as the above component, it is unclear that the change of molecular state by high voltage and the hydrogen bond between the molecules are acting Conceivable. Moreover, it is desirable not to contain the fluorine atom in the said component. If a fluorine atom is contained in the above component, dissolution and swelling of the coating tend to occur, and the protective effect of the positive electrode tends to decrease.

[Component 2]
Component 2 is a metal salt, preferably an alkali metal salt or an alkaline earth metal salt, more preferably a magnesium salt or a sodium salt. Further, phosphorus-based salts, sulfates and carboxylates are desirable, and phosphorus-based salts are particularly desirable. The salt of the phosphorus-based, for example, monofluorophosphate (M _A2 PO ₃ F), metaphosphate _{_{_{((M A PO 3) n}}} ), pyrophosphate (M _A4 P ₂ O ₇₎ . M _A in the above chemical formula represents a metal element, and the valence is 1 to 3.

Moreover, as said component 2, a poly-acid salt is also desirable. The above-mentioned poly acid salt is a designation indicating a salt containing a molecule represented by the chemical formula [M _x O _y ] ^n- (where M is Mo, V, W, Ti, Al, Nb, etc.). For example, salts of tungstic acid, molybdic acid, vanadic acid, manganic acid and the like can be mentioned. The above-mentioned phosphorus-based salts and poly-acid salts are desirable because they are stable even at high voltage and difficult to dissolve in the electrolyte.

[Component 3]
Component 3 is a nitrogen-containing compound. It is desirable that the nitrogen-containing compound be partially in the form of a salt. This is because the nitrogen-containing compound becomes water soluble and the electrode processing becomes easy. In general, nitrogen-containing compounds are believed to be weak at high voltages and prone to battery degradation. However, many nitrogen-containing compounds are likely to be reactive at high voltages, but often exhibit good coverage after reaction.

Examples of the nitrogen-containing compound include amines, amides, imides, amino acids and proteins. On the other hand, since the above nitrogen-containing compound may not sufficiently obtain a coating effect when it is dissolved in a non-aqueous electrolytic solution, it may be a salt or a compound having a molecular weight of 200 or more so as not to dissolve easily. Desirably, the salt is more desirable. The anion moiety of the nitrogen-containing compound salt is preferably a carboxylic acid group, a sulfonic acid group or a phosphoric acid group. Examples of the nitrogen-containing compound salts include diethylenetriaminepentaacetic acid salts such as diethylenetriaminepentaacetic acid pentasodium, ethylenediaminetetraacetic acid salts such as ethylenediaminetetraacetic acid tetrasodium, other magnesium salts, and polypeptides such as sodium polyglutamate and the like Examples include salts, proteins, aspartate, sodium hyaluronate (derived from chicken crown), polyimide salts, polyamide salts, polyallylamine and the like. It is desirable for the compound to have a plurality of salt portions in one molecule, more desirably 4 or more portions, and most desirably 5 or more portions of the salt. More preferably, the nitrogen-containing compound salt is an acetate of an amine.

Moreover, it is desirable not to contain the fluorine atom in the said component. If a fluorine atom is contained in the above component, dissolution and swelling of the coating tend to occur, and the protective effect of the positive electrode tends to decrease.

[Coating of positive electrode]
It is desirable that the coating of the positive electrode is performed with the components 1 to 3 as at least a main component. Although an insulating material such as alumina or an additive can be added as a secondary component, if the secondary component is increased, the electrolytic solution may infiltrate from the part of the secondary component and the protective effect of the coating may be impaired. A specific method of coating the positive electrode can be carried out by applying a treatment liquid containing at least the components 1 to 3 on the surface of the positive electrode. In that case, the proportion of the solid content of the components 1 to 3 in the treatment liquid is desirably 50% by mass or more, more desirably 70% by mass or more, and most desirably 90% by mass or more.

Moreover, as another coating method of the said positive electrode, after making the said components 1 to 3 contain in a positive electrode active material, or making the said components 1 to 3 contain in a non-aqueous electrolyte, and assembling a battery, There is a method to charge and discharge.

Whichever method is used to coat the positive electrode, it is desirable to form the above-mentioned film on the positive electrode after pressing, from the viewpoint of securing the electron conduction of the positive electrode and the prevention of the film breakage.

<Surface condition of positive electrode>
With the surface condition of the positive electrode, as described above, after charging the battery to 4.5 V with a current of 1/3 C, the positive electrode after discharging to 3 V with a current of 1/3 C was washed with methyl ethyl carbonate After that, when the surface of the positive electrode is analyzed by X-ray photoelectron spectroscopy (XPS) after vacuum drying, the oxygen atom content ratio Ro (atomic%) and the fluorine atom content ratio on the surface of the positive electrode Assuming that the content ratio of carbon atoms having Rf (atomic%) and 1s orbital bonding energy of 289 to 291 eV is Rc (atomic%), Rf / Ro is 0.05 or more and 1.3 or less, or Rc / Ro Surface state of the positive electrode which is 0.05 or more and 0.75 or less. In the surface state of the positive electrode, it is considered that a film is formed on the surface of the positive electrode. The film may be formed by the action of the coating of the positive electrode with the components 1 to 3 described above, or may be formed by the action of a specific component or a specific additive contained in the non-aqueous electrolyte described later.

The Rf / Ro is preferably 0.05 or more, more preferably 0.1 or more, and preferably 1.3 or less, more preferably 1.0 or less, and most preferably 0.5 or less. The Rc / Ro is preferably 0.05 or more, more preferably 0.1 or more, and preferably 0.75 or less, more preferably 0.6 or less, and most preferably 0.5 or less. When these values are too large, the electrode protection performance of the formed film tends to be low. When the values are too small, the electrode protection performance is high, but the electrical characteristics due to the increase in resistance tend to be deteriorated.

It is under investigation whether it is desirable that the above Rf / Ro and the above Rc / Ro are within the above range, but the surface of the positive electrode is formed in a state of containing various compounds containing oxygen (eg, active Oxygen of substance, oxygen of electrolyte decomposition product etc.). In addition, the content of oxygen is also second highest to carbon, while oxygen is an important element for ion migration and electrode protection. For example, in the case of a metal oxide positive electrode, oxygen is a constituent element of the active material, and is involved in ion transport and reactivity. Further, the product formed on the surface of the positive electrode is also an important component for film formation such as a carbonic acid compound (carbonate, carbonate etc.), a phosphoric acid compound, a sulfuric acid compound, an alcoholate, an ether compound etc. and its formation reaction.

Here, when the above Rf / Ro and the above Rc / Ro are within the above range, a good protective film is formed in a specific state on the surface of the positive electrode, and the 1s orbital binding energy is 289 to 291 eV carbon atom It is considered to mean that it is possible to suppress formation of the product of the decomposition of the electrolytic solution such as the carbon-containing compound or the fluorine compound contained on the surface of the positive electrode. That is, the above carbon-containing compound is mainly considered to be a carbonic acid compound, and may generate CO ₂ under high voltage, so it is not preferable to add too much. Further, although the fluorine present on the surface of the positive electrode is derived from the fluorine compound component such as LiPF ₆ in the electrolytic solution and the fluorine compound component contained in the positive electrode, when a large amount of this fluorine is present on the surface of the positive electrode It is difficult to do so, the battery characteristics are degraded, and the non-uniform reaction also occurs, and the high voltage cycle characteristics may also be degraded. On the other hand, since the above carbon-containing compounds and fluorine compounds are also involved in electrode protection and ion transport, it is presumed that the absence of a small amount affects the electrical characteristics.

When the positive electrode is in the surface state, the total content of cobalt (Co), nickel (Ni), manganese (Mn) and iron (Fe) on the surface of the positive electrode is reduced by the formation of the film. If it is too low, the electrical properties will be impaired. Therefore, when the surface of the positive electrode is subjected to XPS analysis, the total content ratio of Co, Ni, Mn and Fe on the surface of the positive electrode is preferably 0.1 atomic% or more, more preferably 0.2 atomic% or more. 0.5 atomic% or more is most preferable, 15 atomic% or less is preferable, 5 atomic% or less is more preferable, and 3 atomic% or less is most preferable.

When the above positive electrode is coated with the above-mentioned phosphorus salt, sulfate, polyacid salt, nitrogen-containing compound, etc., phosphorus (P), sulfur (S), metal components (Mo, V, W) on the surface of the above positive electrode It is desirable that each content ratio of Ti, Al, Nb, etc., and nitrogen (N) be in a specific range.

Specifically, when the surface of the positive electrode is subjected to XPS analysis, the content of each of S, metal components (Mo, V, W, Ti, Al, Nb, etc.) and N is preferably 0.1 atomic% or more. 0.2 atomic% or more is more desirable, 0.5 atomic% or more is the most desirable, and 1 atomic% or less is desirable, and 0.5 atomic% or less is more desirable. Similarly, the content of P is preferably 0.5 atomic percent or more, more preferably 1 atomic percent or more, most preferably 2 percent or more, and most preferably 10 atomic percent or less, and 5 atomic percent or less. More desirable. When these values are too large, the electrode protection performance of the formed film tends to be low. When the values are too small, the electrode protection performance is high, but the electrical characteristics due to the increase in resistance tend to be deteriorated.

As described above, the XPS analysis of the surface of the positive electrode described that after charging the battery to 4.5 V with a current of 1/3 C, the positive electrode after discharging to 3 V with a current of 1/3 C was washed with methyl ethyl carbonate Although later performed after vacuum drying, the washing of the positive electrode is usually performed in an inert atmosphere. The XPS measurement apparatus uses, for example, an XPS measurement apparatus "AXIS-NOVA" manufactured by Kratos Co., Ltd., and performs observation in the range of 700 μm × 300 μm as an X-ray source using monochromatized AlKα (1486.6 eV). When the sample is set in the above apparatus, it is preferable to use a transfer vessel so that the sample is kept as free from moisture as possible.

Next, each element of the non-aqueous secondary battery of the present embodiment will be described by exemplifying a representative lithium ion battery. The lithium ion battery includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator.

<Positive electrode>
For the positive electrode, for example, one having a structure having a positive electrode mixture layer containing a positive electrode active material, a conductive additive, a binder and the like on one side or both sides of a current collector can be used.

As the positive electrode active material, a lithium-containing transition metal oxide or the like capable of inserting and extracting lithium ions is used. Examples of lithium-containing transition metal oxides include those used in conventionally known lithium ion batteries. Specifically, Li _y CoO ₂ (where 0 ≦ y ≦ 1.1), Li _z NiO ₂ (where 0 ≦ z ≦ 1.1), Li _p MnO ₂ (wherein is 0 ≦ p ≦ 1.1.), Li q Co r M 2 1-r O 2 ( where, M ² is, Mg, Mn, Fe, Ni , Cu, Zn, Al, Ti, from Ge and Cr At least one metal element selected from the group consisting of 0 ≦ q ≦ 1.1, 0 <r <1.0), Li _s Ni _1-t M ³ _t O ₂ (where M is an integer) ³ is at least one metal element selected from the group consisting of Mg, Mn, Fe, Co, Cu, Zn, Al, Ti, Ge and Cr, and 0 ≦ s ≦ 1.1, 0 <t < 1.0, Li _f Mn _v Ni _w Co _1-vw O ₂ (where 0 ≦ f ≦ 1.1, 0 <v <1.0, 0 <w <1.0). And other layered structures Arm containing transition metal oxides and the like, may be used only one of these may be used in combination of two or more.

As the binder, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylate, polyimide, polyamideimide, etc. are suitably used. .

Moreover, as said conductive support agent, For example, Graphite (graphite carbon materials), such as natural graphite (sculpt graphite etc.), artificial graphite etc .; Acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black And carbon materials such as carbon black; carbon fibers; and the like.

The positive electrode is prepared, for example, by preparing a paste- or slurry-like positive electrode mixture-containing coating material in which the positive electrode active material, the binder, and the conductive auxiliary agent are dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP). The composition is applied to one side or both sides of the current collector, dried and then subjected to a pressing process as required. However, the positive electrode is not limited to one manufactured by the above manufacturing method, and may be manufactured by another manufacturing method.

The thickness of the positive electrode mixture layer is preferably, for example, 10 to 100 μm per side of the current collector. The density of the positive electrode mixture layer is calculated from the mass and thickness of the positive electrode mixture layer per unit area stacked on the current collector, and is preferably 3.0 to 4.5 g / cm ³ . As a composition of the said positive mix layer, it is preferable that the quantity of a positive electrode active material is 60-95 mass%, for example, it is preferable that the quantity of a binder is 1-15 mass%, and the quantity of a conductive support agent is The content is preferably 3 to 20% by mass.

When the surface of the positive electrode is coated by applying the treatment liquid containing at least the components 1 to 3 on the surface of the positive electrode, the porosity of the positive electrode mixture layer is preferably 22% or more and 25% or more. More preferably, 28% or more is most desirable, 35% or less is desirable, 32% or less is more desirable, and 29% or less is most desirable. If the porosity of the positive electrode mixture layer is too large, most of the treatment solution will infiltrate into the positive electrode and the covering effect on the surface becomes low, and if too small, the covering formed by the above components Is limited to the surface, and the coating strength is reduced.

As the current collector of the above positive electrode, the same one as conventionally used for the positive electrode of a lithium ion battery can be used, and it is made of, for example, aluminum, stainless steel, nickel, titanium or their alloys. A foil, a punched metal, an expanded metal, a net, etc. may be mentioned, and usually, an aluminum foil having a thickness of 10 to 30 μm is suitably used.

<Negative electrode>
For the negative electrode, for example, a negative electrode mixture layer containing a negative electrode active material, a binder and the like can be used on one side or both sides of the current collector.

As the negative electrode active material contained in the above-mentioned negative electrode mixture layer, a compound which can deintercalate lithium or a material containing an element which can be alloyed with lithium can be used, but a graphitic carbon material is preferably used. As the graphitic carbon material, those used in conventionally known lithium ion batteries are suitable. For example, natural graphite such as scale-like graphite; pyrolytic carbons, mesophase carbon microbeads (MCMB), Artificial graphite obtained by graphitizing a graphitizable carbon such as carbon fiber at 2800 ° C. or higher. Further, as a material containing an element capable of alloying with lithium, a metal (Si, Sn, etc.) capable of being alloyed with lithium or an alloy thereof may be mentioned, but the general composition formula SiO _x (however, atomic ratio of O to Si) A material containing Si and O represented by x) as 0.5 ≦ x ≦ 1.5 can also be used.

As a binder used for the said negative mix layer, the same thing as the binder illustrated as a binder of the positive electrode mentioned above can be used.

Further, a conductive material may be further added to the negative electrode mixture layer as a conductive aid. The conductive material is not particularly limited as long as it does not cause a chemical change in the lithium ion battery. For example, various carbon blacks such as acetylene black and ketjen black, carbon nanotubes, carbon fibers and the like may be used. A species or two or more species can be used.

The negative electrode is prepared, for example, by preparing a paste-like or slurry-like negative electrode mixture-containing coating material in which a negative electrode active material and a binder, and further, if necessary, a conductive auxiliary agent is dispersed in a solvent such as NMP or water. The composition is applied to one side or both sides of the current collector, dried, and then subjected to a pressing process as required. However, the negative electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by another manufacturing method.

The thickness of the negative electrode mixture layer is preferably, for example, 10 to 100 μm per side of the current collector. The density of the negative electrode mixture layer is preferably 1.0 to 1.9 g / cm ³ . In the composition of the negative electrode mixture layer, the amount of the negative electrode active material is preferably 80 to 99% by mass, the amount of the binder is preferably 1 to 20% by mass, and the conductive auxiliary agent is used. It is preferable that the conductive aid be used in such a range that the amount of the negative electrode active material and the amount of the binder satisfy the above-mentioned suitable values.

As the current collector of the negative electrode, a foil made of copper or nickel, a punching metal, a net, an expanded metal or the like may be used, but a copper foil is usually used. The upper limit of the thickness of the negative electrode current collector is preferably 30 μm when the thickness of the entire negative electrode is reduced to obtain a battery of high energy density, and the lower limit of the thickness is 5 μm to ensure mechanical strength. Is preferred.

<Non-aqueous electrolyte>
As the non-aqueous electrolytic solution, a non-aqueous electrolytic solution in which an electrolyte salt such as an inorganic lithium salt or an organic lithium salt is dissolved in an organic solvent is used.

Examples of the organic solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC) Γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric triester , Trimethoxymethane, dioxolane derivatives, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl Ethers, include aprotic organic solvents such as 1,3-propane sultone, it may be used those either alone, or in combination of two or more.

Examples of the inorganic lithium _{_{salt, LiClO 4, LiBF 4, LiPF}} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, lower aliphatic carboxylic acids Li, LiAlCl _4, LiCl, LiBr And LiI, chloroborane Li, tetraphenylborate Li and the like, and these may be used alone or in combination of two or more.

Examples of the organic lithium salt include LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ and LiC _n1 F _{2n1 + 1} SO ₃ (2 ≦ n1 ≦ 7), LiN (Rf ₁ OSO ₂ ) ₂ [wherein, Rf ₁ is a fluoroalkyl group. And the like, and these may be used alone or in combination of two or more.

The concentration of the electrolyte salt in the nonaqueous electrolyte solution, for example, preferably from 0.2 ~ 3.0mol / dm ^3, more preferably from ^{0.5 ~ 1.5mol / dm 3, 0} . More preferably, it is 9 to 1.3 mol / dm ³ .

As described above, after charging the battery to 4.5 V with a 1/3 C current, the positive electrode after discharging to 3 V with a 1/3 C current is washed with methyl ethyl carbonate and then vacuum dried, and then the above positive electrode In the surface of the positive electrode, the content ratio of oxygen atoms is Ro (atomic%), the content ratio of fluorine atoms is Rf (atomic%), and the surface of the positive electrode is analyzed by X-ray photoelectron spectroscopy (XPS) Assuming that the content ratio of a carbon atom having a binding energy of 289 to 291 eV is Rc (atomic%), Rf / Ro is 0.05 or more and 1.3 or less, or Rc / Ro is 0.05 or more and 0.75 or less In order to obtain the surface state of the positive electrode, the non-aqueous electrolyte preferably contains a fluorine-containing compound as the lithium salt, and preferably contains a carbonic acid compound as the organic solvent. The non-aqueous electrolyte may include at least one of the fluorine-containing compound and the carbonic acid compound, but preferably contains both the fluorine-containing compound and the carbonic acid compound. However, the said fluorine-containing compound and the said carbonic acid compound may be contained in the positive electrode.

As a non-aqueous electrolytic solution for obtaining the surface state of the above positive electrode, at least one linear carbonate selected from dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, and at least one cyclic selected from ethylene carbonate and propylene carbonate It is particularly preferable to use a non-aqueous electrolytic solution in which LiPF ₆ (lithium hexafluorophosphate) is dissolved in a solvent containing carbonate.

In order to improve the charge / discharge cycle characteristics and to improve safety such as high-temperature storage characteristics and overcharge prevention, the non-aqueous electrolyte can contain the following additives as appropriate. Examples of the additive include an acid anhydride, a sulfonic acid ester, dinitrile, 1,3-propanesultone, diphenyl disulfide, cyclohexylbenzene, vinylene carbonate (VC), biphenyl, fluorobenzene, t-butylbenzene, cyclic fluorinated Carbonate [trifluoropropylene carbonate (TFPC), fluoroethylene carbonate (FEC), etc.] or linear fluorinated carbonate [trifluorodimethyl carbonate (TFDMC), trifluorodiethyl carbonate (TFDEC), trifluoroethyl methyl carbonate (TFE MC) Etc.], fluorinated ethers [Rf ₂ -OR ₄ (where Rf ₂ is a fluorine-containing alkyl group, R ₄ is an organic group which may contain fluorine)], phosphoric acid ester [ Ethyldiethylphosphonoacetate (EDPA): (C ₂ H ₅ O) ₂ (P = O) -CH ₂ (C = O) OC ₂ H ₅ ], tris (trifluoroethyl) phosphate (TFEP): (CF ₃ CH ₂ O) ₃ P = O, triphenyl phosphate (TPP): (C ₆ H ₅ O) ₃ P = O, etc. (including derivatives of the above-mentioned compounds).

An additive that is effective in improving charge / discharge cycle characteristics under high voltage when used in combination with the above-mentioned positive electrode coating is a compound having two or more nitrile groups in the molecule. Examples of the compound having two or more nitrile groups in the molecule include succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,7 8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethyl succinonitrile, 2-methylglutaronitrile, 4-dicyanopentane, 2,6-dicyanoheptane, Examples thereof include dinitriles such as 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane and 1,2-dicyanobenzene. In addition, part of these dinitriles and the like may be fluorinated.

The concentration of the compound having two or more nitrile groups in the molecule in the non-aqueous electrolyte is preferably 0.1% by mass or more, more preferably 2% by mass or more, and most preferably 10% by mass or more. % By mass or less is desirable, 30% by mass or less is more desirable, and 20% by mass or less is the most desirable.

<Separator>
The separator preferably has sufficient strength and can hold a large amount of non-aqueous electrolytic solution, for example, polyethylene (PE) or polypropylene (PP) having a thickness of 5 to 50 μm and an opening ratio of 30 to 70%. And the like can be used. The microporous membrane constituting the separator may be, for example, one using only PE or one using PP, may contain an ethylene-propylene copolymer, and may be made of PE It may be a laminate of a porous membrane and a microporous membrane made of PP.

In addition, as the separator, a porous layer mainly composed of a resin having a melting point of 140 ° C. or less and a porous layer mainly composed of a resin having a melting point of 150 ° C. or more or an inorganic filler having a heat resistance temperature of 150 ° C. It is also possible to use a laminated separator composed of B). The porous layer (A) is mainly for securing the shutdown function, and when the internal temperature of the lithium ion battery reaches the melting point of the resin which is the main component of the porous layer (A). The resin according to the porous layer (A) melts to close the pores of the separator, resulting in a shutdown that suppresses the progress of the electrochemical reaction. On the other hand, the porous layer (B) has a function of preventing a short circuit due to direct contact between the positive electrode and the negative electrode even when the internal temperature of the lithium ion battery rises, and has a melting point of 150.degree. The function is ensured by the resin or the inorganic filler having a heat resistant temperature of 150 ° C. or higher. That is, when the battery becomes high temperature, the positive and negative electrodes may be generated directly when the separator is thermally shrunk by the porous layer (B) which is hardly shrunk even when the grip porous layer (A) is shrunk. It is possible to prevent a short circuit due to contact. Further, since the heat-resistant porous layer (B) acts as a skeleton of the separator, the heat shrinkage of the porous layer (A), that is, the heat shrinkage itself of the whole separator can be suppressed. Here, the "melting point" means a melting temperature measured using a differential scanning calorimeter (DSC) according to the Japanese Industrial Standard (JIS) K7121, and "the heat resistant temperature is 150 ° C or higher" Means that no deformation such as softening is observed at least at 150 ° C.

The thickness of the above-mentioned separator (a separator comprising a microporous membrane made of polyolefin, or the above-mentioned laminated separator) is more preferably 10 to 30 μm.

<Electrode body>
As an electrode body used for the non-aqueous secondary battery of the present embodiment, a laminated electrode body in which the positive electrode and the negative electrode are laminated via the separator, or winding in which the laminated electrode body is further wound in a spiral shape An electrode body is mentioned.

<Form of battery>
The form of the lithium ion battery is not particularly limited. For example, any of coin type, button type, sheet type, laminated type, cylindrical type, flat type, square type, large type used in electric vehicles etc. Good.

<Characteristics of non-aqueous secondary battery>
The charge voltage of the non-aqueous secondary battery of the present embodiment is preferably 4.35 V or more, more preferably 4.45 V or more, and most preferably 4.55 V or more based on lithium. It is because the electrode protection effect by the positive electrode coating of this embodiment works more effectively as the charging voltage becomes higher. Moreover, as for the said charging voltage, 5.5 V or less is desirable. If the charging voltage is too high, there is a risk of decomposition of the protective film itself. Furthermore, when the charge voltage of the lithium ion battery is preferably 4.4 V or more, more preferably 4.55 V or more based on lithium, the continuous heat generation state of the battery starts from a lower temperature, so the electrolysis containing the above-mentioned dinitrile The combination with the solution is more optimal.

In the non-aqueous secondary battery of the present embodiment, after charging to 4.35 V with a current of 1/3 C, discharging to 3 V with a current of 1/3 C is one cycle, and 100 cycles to the discharge capacity at 1 cycle The ratio (%) of the discharge capacity at that time is 4.35V capacity maintenance rate: RL, after charging to 4.5V with 1 / 3C current, discharging to 3V with 1 / 3C current is one cycle, When the ratio (%) of the discharge capacity at 100 cycles to the discharge capacity at one cycle is 4.5 V capacity maintenance ratio: RH, the capacity maintenance ratio ratio RH / RL can be 0.75 or more. The above capacity retention ratio: RH / RL is more preferably 0.8 or more, and most preferably 0.9 or more. That is, in the non-aqueous secondary battery of the present embodiment, the decrease in charge-discharge cycle characteristics can be suppressed to a low level even under high voltage. If the charge voltage is different from that of the present embodiment, the capacity retention ratio in the charge / discharge cycle test at that charge voltage is taken as RH ', and the same charge / discharge cycle test is performed at a voltage 0.15 V lower than the charge voltage. When the capacity retention ratio in this case is RL ′, RH ′ / RL ′ is more preferably 0.8 or more, and most preferably 0.9 or more.

Further, in the conventional non-aqueous secondary battery fabricated in the same manner as the non-aqueous secondary battery of the present embodiment except that the positive electrode was not coated, after charging to 4.35 V with a 1/3 C current, 1 Assuming that discharging to 3 V with a current of 3 C is one cycle, and the ratio (%) of discharge capacity at 100 cycles to the discharge capacity at 1 cycle is 4.35 V capacity retention ratio: RLC, 1/3 C current After charging to 4.5V, discharging to 3V with 1 / 3C current is one cycle, and the ratio (%) of discharge capacity at 100 cycles to discharge capacity at one cycle is 4.5V capacity maintenance ratio: In the case of RHC, the 4.35 V capacity maintenance ratio improvement ratio A calculated at the following equation (1) from RL of the present embodiment and the conventional RLC at 4.35 V, and RH of the present embodiment and the conventional at 4.5 V RHC In comparison with the 4.5 V capacity maintenance ratio improvement ratio B calculated by the following equation (2), in the present embodiment, the 4.5 V capacity maintenance ratio improvement ratio B is 4.35 V capacity contrary to the initial expectation. It can be made larger than the maintenance rate improvement rate A.
A = [(RL−RLC) / RLC] × 100 (1)
B = [(RH-RHC) / RHC] x 100 (2)

Also, if the value of B / A obtained from the 4.5 V capacity maintenance ratio improvement ratio B and the 4.35 V capacity maintenance ratio improvement ratio A is 1 or more, it indicates that the charge and discharge cycle characteristics at high voltage are high. . Therefore, B / A is preferably 1 or more, more preferably 5 or more, and most preferably 10 or more.

Further, even when the charging voltage is different from that of the present embodiment, the capacity maintenance rate improvement ratio at the charging voltage is B ′, and the capacity maintenance rate improvement ratio at the charging voltage 0.15 V lower than the charging voltage is A ′. Sometimes, B '/ A' is preferably 1 or more, more preferably 5 or more, and most preferably 10 or more.

(Second Embodiment of Nonaqueous Secondary Battery)
A second embodiment of the non-aqueous secondary battery of the present invention comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the non-aqueous electrolyte or the positive electrode contains a fluorine-containing compound or a carbonic acid compound, and the non-aqueous electrolysis The solution contains an additive other than vinylene carbonate, and the concentration of the additive in the non-aqueous electrolyte solution is 0.05% by mass or more and 3% by mass or less.

By using the non-aqueous secondary battery having the above configuration, after charging the battery to 4.5 V with a 1/3 C current, the positive electrode after discharging to 3 V with a 1/3 C current is washed with methyl ethyl carbonate After vacuum drying, the surface of the positive electrode is analyzed by X-ray photoelectron spectroscopy (XPS). The content of oxygen atoms in the surface of the positive electrode is Ro (atomic%) and the content ratio of fluorine atoms If Rf (atomic%) and the content ratio of carbon atoms with a 1s orbital bond energy of 289 to 291 eV is Rc (atomic%), Rf / Ro is 0.05 or more or 1.3 or less, or Rc / Rc Ro can be 0.05 or more and 0.75 or less. Thereby, charge / discharge cycle characteristics under high voltage can be improved.

As the fluorine-containing compound and the carbonic acid compound, the same compounds as those used in the non-aqueous secondary battery of the first embodiment described above can be used.

Moreover, as additives other than the said vinylene carbonate, a nitrogen-containing compound is desirable, and a non-fluorine-type (fluorine-free) nitrogen-containing compound is more desirable. Furthermore, in the nitrogen-containing compound, it is desirable that at least one H atom is bonded to the nitrogen atom, and it is more preferable that two H atoms be bonded to the nitrogen atom. Examples of the nitrogen-containing compound include amines and amides, with amines being particularly desirable. More specifically, diethylene glycol bisaminopropyl ether, diethylene oxide bishexamethylene triamine, dicyclohexylamine and the like can be used as the nitrogen-containing compound.

The concentration of the additive in the non-aqueous electrolyte is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and preferably 3% by mass or less, and more preferably 1% by mass or less. The above-mentioned additive reacts with the positive electrode to form a film. When the amount is too small, a sufficient film is not formed, and when it is too large, the resistance becomes high.

The configuration other than the above-described configuration of the non-aqueous secondary battery of the present embodiment can be the same as the configuration of the non-aqueous secondary battery of the first embodiment described above.

(Embodiment of manufacturing method of non-aqueous secondary battery)
The first embodiment of the method for producing a non-aqueous secondary battery of the present invention is a method for producing the non-aqueous secondary battery according to the above-mentioned first embodiment, which is selected from Component 1, Component 2 and Component 3. Providing a treatment liquid containing at least one component, and applying the treatment liquid to the surface of the positive electrode, wherein the component 1 is a sugar analog compound, and the component 2 is a metal salt The component 3 is a nitrogen-containing compound, and the positive electrode is a positive electrode after pressing.

The components 1 to 3 may be the same as those used in the non-aqueous secondary battery of the first embodiment described above.

The reason for using the positive electrode after press treatment as the positive electrode is to adjust the porosity of the positive electrode mixture layer of the positive electrode. In addition, in the positive electrode after the pressing process, the conductive network is already formed, and by performing the coating process in that state, the influence on the conductivity is small, and the coating to the conductive material may also be performed. It is preferable in terms of battery characteristics.

The porosity of the positive electrode mixture layer is preferably 22% or more, more preferably 25% or more, and most preferably 28% or more, and preferably 35% or less, more preferably 32% or less, and most preferably 29% or less. desirable. If the porosity of the positive electrode mixture layer is too large, most of the treatment solution will infiltrate into the positive electrode and the covering effect on the surface becomes low, and if too small, the covering formed by the above components Is limited to the surface, and the coating strength is reduced.

In the present embodiment, when the positive electrode is immersed in the treatment solution for 10 seconds, taken out and left for 5 seconds, the mass increase rate of the positive electrode before and after the immersion treatment is 3 when the mass of the positive electrode is measured. % Or more is desirable, 20% or more is more desirable, and 50% or less is desirable. If the said mass increase rate exists in the said range, the surface of a positive electrode can be wetted moderately with the said process liquid.

The concentration of the component in the treatment liquid is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, most preferably 0.1% by mass or more, and preferably 20% by mass or less, 10% by mass. % Or less is more desirable, and 2% by mass or less is most desirable. When the concentration is too low, the covering effect is reduced, and when the concentration is too high, it is difficult to control the amount of coating and the resistance of the electrode increases.

The coating amount of the surface of the positive electrode of the treatment liquid, a dry component mass conversion of the processing solution, 0.0002 mg / cm ² or more is desirable, 0.002 mg / cm ² or more and more preferably, 0.008 mg / Cm ² or more is most desirable, and 0.5 mg / cm ² or less is desirable, 0.15 mg / cm ² or less is more desirable, and 0.1 mg / cm ² or less is most desirable. When the application amount is too small, the covering effect is reduced, and when the application amount is too large, the resistance of the electrode is increased.

Moreover, 2nd Embodiment of the manufacturing method of the non-aqueous secondary battery of this invention is a method of manufacturing the non-aqueous secondary battery of the above-mentioned 1st Embodiment, Comprising: The component 1, the component 2, and the component 3 Preparing a non-aqueous electrolyte containing at least one component selected from the following: assembling a battery using the positive electrode, the negative electrode, and the non-aqueous electrolyte, and charging / discharging the assembled battery. The component 1 is a sugar analog compound, the component 2 is a metal salt, and the component 3 is a nitrogen-containing compound.

Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
The laminate type lithium ion battery shown in FIG. 1 was produced as follows.

[Production of positive electrode]
First, 100 parts by mass of LiCoO ₂ (manufactured by Nippon Chemical Industrial Co., Ltd., "C20F") which is a positive electrode active material, 3 parts by mass of acetylene black which is a conductive additive, and 3 parts by mass of PVDF which is a binder (solid content as NMP solution Was mixed uniformly with the solvent NMP to prepare a positive electrode mixture-containing paste. Next, the obtained positive electrode mixture-containing paste is applied on one side of a current collector made of an aluminum foil having a thickness of 20 μm so that the coating amount is 18.0 mg / cm ² as the solid content of the positive electrode mixture-containing paste. After coating and drying, calendering is performed to adjust the thickness of the positive electrode mixture layer to a total thickness of 75 μm, and cut so as to have a length of 30 mm and a width of 30 mm, leaving a tab weld. The positive electrode was prepared. Furthermore, the active material of the tab weld of this positive electrode was removed, and the tab was welded to the tab weld to form a lead.

After measuring the mass of the positive electrode, the positive electrode is immersed in ion exchange water for 10 seconds, taken out, left for 5 seconds, and then the mass of the positive electrode is measured. The mass increase rate before and after the immersion treatment of the positive electrode Was 35%.

[Coating treatment of positive electrode]
Diethylene triamine pentaacetic acid pentasodium (approx. 40% by mass aqueous solution, corresponding to Component 2 and Component 3) manufactured by Tokyo Chemical Industry Co., Ltd. is diluted with ion-exchanged water, and a 1 mass% aqueous solution of diethylenetriamine pentaacetic acid pentasodium is shown in this example. Prepared as a processing solution of Next, using the coating rod which wound cellulose on the surface of the positive electrode produced above, the above-mentioned processing solution is applied by about 1 mg / cm ² application amount, and then the above-mentioned positive electrode is dried at 120 ° C. The processed positive electrode was produced.

[Fabrication of negative electrode]
100 parts by mass of graphite ("MAGE" manufactured by Hitachi Chemical Co., Ltd.) which is a negative electrode active material, 1 part by mass of CMC which is a binder (supply solid content as a 1% by mass aqueous solution) and 1.5 parts by mass of SBR It mixed in a certain ion exchange water and prepared negative mix containing paste. Next, the obtained negative electrode mixture-containing paste is applied to one side of a 16.5 μm thick copper foil so that the amount of application becomes 12.7 mg / cm ² as the solid content of the negative electrode mixture-containing paste and dried. Then, calendering is performed to adjust the thickness of the negative electrode mixture layer to a total thickness of 113 μm, and cut so as to have a length of 32 mm and a width of 32 mm, leaving a tab welded portion to produce a negative electrode. did. Furthermore, a tab was welded to the tab weld of this negative electrode to form a lead.

[Preparation of separator]
As a separator, what cut | disconnected the polyethylene microporous film with a thickness of 25 micrometers in length 45 mm and width 40 mm was prepared.

[Preparation of Nonaqueous Electrolyte]
1.0 mol of LiPF ₆ is dissolved in 1 kg of a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) at a volume ratio of 1: 3 to prepare a mixed solution, and 100 parts by mass of the mixed solution is further added 2 parts by mass of vinylene carbonate (VC) and 3 parts by mass of succinonitrile were added to prepare a non-aqueous electrolyte.

[Assembly of battery and charge]
The positive electrode and the negative electrode were stacked with the separator interposed therebetween to prepare a three-layer laminated electrode body of positive electrode / separator / negative electrode. The obtained laminated electrode body was housed in an outer package made of an aluminum laminate film, and after the non-aqueous electrolyte was injected, sealing was performed. Finally, charge and discharge the laminate type lithium ion battery at 10 mA (rate corresponding to 1/3 C), upper limit voltage 4.35 V (Li basis: 4.45 V), lower limit voltage 3 V five times. It was a laminate type lithium ion battery.

The top view of the produced laminated | stacked lithium ion battery is shown in FIG. In FIG. 1, in the laminate type lithium ion battery 10, a laminated electrode body and a non-aqueous electrolyte are accommodated in an outer package 11 made of a rectangular aluminum laminate film in plan view. The positive electrode external terminal 12 and the negative electrode external terminal 13 are drawn from the same side of the exterior body 11.

(Example 2)
A laminate-type lithium ion battery of Example 2 was produced in the same manner as in Example 1 except that the concentration of pentasodium diethylenetriaminepentaacetate was changed to 2% by mass in the treatment liquid used for the coating treatment of the positive electrode.

(Example 3)
A laminate-type lithium ion battery of Example 3 was produced in the same manner as in Example 1 except that the concentration of pentasodium diethylenetriaminepentaacetate was changed to 5% by mass in the treatment liquid used for the coating treatment of the positive electrode.

(Example 4)
A laminate-type lithium ion battery of Example 4 was produced in the same manner as in Example 1 except that succinonitrile was not added to the non-aqueous electrolytic solution.

(Example 5)
A laminate-type lithium ion battery of Example 5 was produced in the same manner as in Example 1 except that the addition amount of succinonitrile in the non-aqueous electrolytic solution was changed to 20 parts by mass.

(Example 6)
Non-aqueous electrolysis using a 1% by mass aqueous solution of tetrasodium ethylenediaminetetraacetate (corresponding to Component 2 and Component 3) in place of the 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetate in the treatment solution used for the coating treatment of the positive electrode A laminated lithium ion battery of Example 6 was produced in the same manner as in Example 1 except that succinonitrile was not added to the solution.

(Example 7)
In the treatment solution used for the coating treatment of the positive electrode, 1 mass% of fructan (corresponds to component 1) and 0.9 mass% of gamma glutamic acid (corresponds to component 3) instead of a 1 mass% aqueous solution of pentasodium diethylenetriaminepentaacetate A laminate-type lithium ion battery of Example 7 was produced in the same manner as in Example 1 except that the mixed aqueous solution was used, and succinonitrile was not added to the non-aqueous electrolytic solution.

(Example 8)
The treatment liquid used for the coating treatment of the positive electrode was replaced with a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetic acid, and a 1% by mass aqueous solution of Li ₂ MoO ₄ (corresponding to component 2) was used. Similarly, a laminate-type lithium ion battery of Example 8 was produced.

(Example 9)
In the treatment solution used for the coating treatment of the positive electrode, a 1% by mass aqueous solution of Li ₂ MoO ₄ (corresponding to component 2) is used instead of a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetate A laminated lithium ion battery of Example 9 was produced in the same manner as in Example 1 except that the nitrile was not added.

(Example 10)
In the treatment solution used for the coating treatment of the positive electrode, a 1% by mass aqueous solution of Li ₂ WO ₄ (corresponding to component 2) is used instead of a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetate to form a non-aqueous electrolyte A laminated lithium ion battery of Example 10 was produced in the same manner as in Example 1 except that the nitrile was not added.

(Example 11)
In the treatment solution used for the coating treatment of the positive electrode, 5 of lignin sulfonic acid sodium (corresponding to Component 1 and Component 2) made of sodium lignin sulfonate in place of a 1% by mass aqueous solution of diethylenetriamine pentaacetic acid pentasodium A laminate-type lithium ion battery of Example 11 was produced in the same manner as in Example 1 except that a mass% aqueous solution was used, and succinonitrile was not added to the non-aqueous electrolytic solution.

(Example 12)
In the treatment solution used for the coating treatment of the positive electrode, 1 of sodium lignin sulfonate (corresponding to Component 1 and Component 2) of lignin sulfonic acid sodium instead of 1% by mass aqueous solution of diethylenetriamine pentaacetic acid pentasodium A laminated lithium ion battery of Example 12 was produced in the same manner as Example 1 except that the addition amount of succinonitrile in the non-aqueous electrolyte was changed to 20 parts by mass using a mass% aqueous solution.

(Example 13)
In the treatment solution used for the coating treatment of the positive electrode, the 1% by mass aqueous solution of sucrose (corresponding to Component 1) is used instead of the 1% by mass aqueous solution of pentasodium diethylenetriamine pentaacetate, and the addition of succinonitrile in the non-aqueous electrolyte A laminated lithium ion battery of Example 13 was made in the same manner as Example 1 except that the amount was 20 parts by mass.

(Example 14)
In the treatment solution used for the coating treatment of the positive electrode, an example was used except that a 0.1 mass% aqueous solution of carboxymethylcellulose (CMC, corresponding to component 1) was used instead of a 1 mass% aqueous solution of diethylenetriamine pentaacetic acid pentasodium. In the same manner as in Example 1, a laminate-type lithium ion battery of Example 14 was produced.

(Example 15)
In the treatment solution used for the coating treatment of the positive electrode, a 0.1 mass% aqueous solution of carboxymethylcellulose (CMC, corresponding to component 1) is used instead of a 1 mass% aqueous solution of pentasodium diethylenetriaminepentaacetate to prepare a non-aqueous electrolyte A laminated lithium ion battery of Example 15 was produced in the same manner as in Example 1 except that succinonitrile was not added.

(Example 16)
In the treatment solution used for the coating treatment of the positive electrode, a 1% by mass aqueous solution of sodium alginate (corresponding to Component 1 and Component 2) is used instead of a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetic acid to form a non-aqueous electrolyte A laminated lithium ion battery of Example 16 was made in the same manner as Example 1 except that the amount of addition of sinonitrile was 20 parts by mass.

(Example 17)
Used in the processing solution used in the coating process of the positive electrode, in place of the 1 wt% aqueous solution of diethylenetriaminepentaacetic acid pentasodium, monofluorophosphate, sodium 1 mass% aqueous solution of (Na ₂ PO ₃ F, component 2 corresponds to), A laminate-type lithium ion battery of Example 17 was produced in the same manner as in Example 1 except that succinonitrile was not added to the non-aqueous electrolytic solution.

(Example 18)
In the treatment solution used for the coating treatment of the positive electrode, a 1% by mass aqueous solution of Na ₃ PO ₄ (corresponding to component 2) is used instead of a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetic acid to form a non-aqueous electrolyte. A laminated lithium ion battery of Example 18 was produced in the same manner as in Example 1 except that the nitrile was not added.

(Example 19)
In the treatment solution used for the coating treatment of the positive electrode, a 1% by mass aqueous solution of sodium metaphosphate [corresponding to (NaPO ₃ ) _n , component 2] is used instead of a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetate A laminated lithium ion battery of Example 19 was produced in the same manner as Example 1, except that succinonitrile was not added to the electrolytic solution.

Example 20
In the treatment solution used for the coating treatment of the positive electrode, a 1 mass% aqueous solution of sodium pyrophosphate (Na ₄ P ₂ O ₇ , corresponding to component 2) is used instead of a 1 mass% aqueous solution of pentasodium diethylenetriamine pentaacetate. A laminated lithium ion battery of Example 20 was produced in the same manner as Example 1, except that succinonitrile was not added to the water electrolyte.

(Example 21)
Non-aqueous electrolyte solution using a 1% by mass aqueous solution of 3-sulfopropyl potassium methacrylate (corresponding to component 2) in place of the 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetate in the treatment liquid used for the coating treatment of the positive electrode A laminated lithium ion battery of Example 21 was produced in the same manner as in Example 1 except that succinonitrile was not added.

(Example 22)
In the treatment solution used for the coating treatment of the positive electrode, a 1% by mass aqueous solution of lithium dibenzenesulfonic acid imide (corresponding to Component 2 and Component 3) is used instead of a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetate A laminated lithium ion battery of Example 22 was made in the same manner as Example 1, except that succinonitrile was not added to the electrolytic solution.

(Example 23)
In the treatment solution used for the coating treatment of the positive electrode, a 1% by mass aqueous solution of β-cyclodextrin (corresponding to Component 1) is used instead of a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetate to form a non-aqueous electrolyte. A laminated lithium ion battery of Example 23 was made in the same manner as Example 1 except that the nitrile was not added.

(Example 24)
In the treatment solution used for the coating treatment of the positive electrode, a 1% by mass aqueous solution of α-cyclodextrin (corresponding to Component 1) is used instead of a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetate to form a non-aqueous electrolyte. A laminated lithium ion battery of Example 24 was produced in the same manner as in Example 1 except that the nitrile was not added.

(Example 25)
In the treatment solution used for the coating treatment of the positive electrode, a 1% by mass aqueous solution of sodium alginate (corresponding to Component 1 and Component 2) is used instead of a 1% by mass aqueous solution of pentasodium diethylenetriaminepentaacetic acid to form a non-aqueous electrolyte A laminated lithium ion battery of Example 25 was made in the same manner as Example 1 except that no sinonitrile was added.

(Example 26)
In the treatment solution used for the coating treatment of the positive electrode, 1 mass of alginic acid and sodium alginate (corresponding to 50% partially neutralized alginic acid product, component 1 and component 2) instead of a 1 mass% aqueous solution of diethylenetriamine pentaacetic acid pentasodium A laminated lithium ion battery of Example 26 was produced in the same manner as in Example 1 except that the% aqueous solution was used and the succinonitrile was not added to the non-aqueous electrolytic solution.

(Example 27)
In the treatment solution used for the coating treatment of the positive electrode, 0.3 mass of sodium polyacrylate (molecular weight: 30,000, corresponding to component 1 and component 2) instead of 1 mass% aqueous solution of pentasodium diethylenetriamine pentaacetate A laminate-type lithium ion battery of Example 27 was produced in the same manner as in Example 1 except that a 20% aqueous solution was used, and succinonitrile was not added to the non-aqueous electrolytic solution.

(Example 28)
In the treatment solution used for the coating treatment of the positive electrode, a 0.3 mass% aqueous solution of polyacrylic acid (molecular weight: 250,000, corresponding to component 1) is used instead of a 1 mass% aqueous solution of pentasodium diethylenetriamine pentaacetate. A laminate-type lithium ion battery of Example 28 was produced in the same manner as in Example 1 except that succinonitrile was not added to the water electrolyte solution.

(Example 29)
A mixed solution was prepared by dissolving 1.0 mol of LiPF ₆ in 1 kg of a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) at a volume ratio of 1: 3 without coating the positive electrode by applying the treatment liquid. The non-aqueous electrolyte is prepared by adding 2 parts by mass of vinylene carbonate (VC), 3 parts by mass of succinonitrile, and 0.3 parts by mass of diethylene glycol bisaminopropyl ether to 100 parts by mass of the mixture. A laminated lithium ion battery of Example 29 was produced in the same manner as in Example 1 except for preparing and using this non-aqueous electrolyte.

(Comparative example 1)
A laminate-type lithium ion battery of Comparative Example 1 was produced in the same manner as in Example 1 except that the coating treatment of the positive electrode by the application of the treatment liquid was not performed and succinonitrile was not added to the non-aqueous electrolyte.

(Comparative example 2)
A laminate-type lithium ion battery of Comparative Example 2 was produced in the same manner as Example 1, except that the coating treatment of the positive electrode by application of the treatment liquid was not performed.

Next, the following evaluation test is performed on the batteries of Examples 1 to 29 and Comparative Examples 1 and 2 described above, and the positive electrode surfaces of Examples 1, 5, 11, 12, 19, 20, and 29 and Comparative Examples 1 and 2. XPS analysis was performed.

<Charge / discharge cycle test>
[4.35 V charge and discharge cycle test]
The charge and discharge were repeated 100 times under the conditions of a current of 10 mA (corresponding to a current value of 1/3 C), an upper limit voltage of 4.35 V, and a lower limit voltage of 3 V. Based on this, the ratio (%) of the discharge capacity at 100 cycles to the discharge capacity at 1 cycle is calculated as 4.35 V capacity retention ratio: RL for Examples 1 to 29, and 4.4 for Comparative Example 1. The 35 V capacity maintenance rate was calculated as RLC 1, and the comparative example 2 was calculated as 4.35 V capacity maintenance rate: RLC 2.

[4.5 V charge and discharge cycle test]
The charge and discharge were repeated 100 times under the conditions of a current of 10 mA (corresponding to a current value of 1/3 C), an upper limit voltage of 4.5 V, and a lower limit voltage of 3 V. Based on this, the ratio (%) of the discharge capacity at 100 cycles to the discharge capacity at 1 cycle is calculated as a 4.5 V capacity retention ratio: RH for Examples 1 to 29, and for Comparative Example 1, 4. The 5 V capacity maintenance rate was calculated as RHC 1, and the comparative example 2 was calculated as 4.5 V capacity maintenance rate: RHC 2.

[Calculation of 4.35 V capacity maintenance rate improvement ratio A]
For Examples 1 to 29 and Comparative Example 2, the improvement ratio A of 4.35 V capacity retention ratio was calculated by the following formula A.
A = [(RL−RLC1) / RLC1] × 100

[Calculation of 4.5 V capacity maintenance rate improvement ratio B]
For Examples 1 to 29 and Comparative Example 2, the 4.5 V capacity maintenance ratio improvement ratio B was calculated by the following formula B.
B = [(RH-RHC1) / RHC1] × 100

[Calculation of B / A]
B / A was calculated from the 4.35 V capacity retention ratio improvement ratio A and the 4.5 V capacity retention ratio improvement ratio B.

<Heating test>
The external terminal of the laminate type lithium ion battery was cut, and an imide tape was wound around the cut portion for insulation while keeping the battery configuration, and it was wrapped with aluminum foil to prepare a measurement sample. Thereafter, the measurement sample is inserted into a stainless steel sample container with a pressure of 100 atm pressure and a calorimeter "C80" manufactured by Setaram Co., and the sample container is further inserted into the main body of "C80", 1 from 40 ° C to 300 ° C. The temperature rising test was conducted at ° C./min, the heat generation of the battery was measured, and the temperature of the heat generation peak of the battery observed at 200 ° C. or higher was measured.

<XPS analysis>
After charging and discharging once under the conditions of current 10 mA (corresponding to a current value of 1/3 C), upper limit voltage 4.5 V, lower limit voltage 3 V, the battery is disassembled to take out the positive electrode, and the above positive electrode is in an inert atmosphere. After washing with methyl ethyl carbonate, it was dried under vacuum. After that, using an XPS measurement apparatus “AXIS-NOVA” manufactured by Kratos, using monochromatized AlKα (1486.6 eV) as an X-ray source, in an analysis area of 700 μm × 300 μm, Pass Energy: 20 eV from an inert atmosphere Vacuum drawing was performed, and XPS analysis of the surface of the positive electrode was performed. In the above-mentioned XPS analysis, peak position correction is performed at the peak position (binding energy of 1s orbital: 284.4 eV) of the conductive support agent (carbon black) contained in the positive electrode, and for peak division, position peak and peak width Were separated.

As a result of the XPS analysis, the content of oxygen atom is Ro (atomic%), the content of fluorine atom is Rf (atomic%), and the carbon atom with 1s orbital bond energy of 289 to 291 eV on the surface of the positive electrode Rf / Ro and Rc / Ro were calculated by setting the ratio to Rc (atomic%). In addition, the content ratio of other atoms on the surface of the positive electrode was also measured.

Tables 1 and 2 show the presence or absence of the nitrile compound in the positive electrode surface treatment agent and the non-aqueous electrolyte used in Examples 1 to 29 and Comparative Examples 1 and 2 described above. Moreover, the result of the said evaluation test and the XPS analysis of the positive electrode surface is shown in Table 3 and Table 4. Moreover, in Table 3 and Table 4, the content ratio of N: nitrogen atom, P: phosphorus atom, S: sulfur atom, M: active material metal component is also shown as another atomic ratio.

From Tables 1 to 4, it is possible to use a positive electrode coated with at least one of a sugar analog compound (component 1), a metal salt (component 2) and a nitrogen-containing compound (component 3), or a battery using a positive electrode with a specific surface condition It can be seen that excellent charge and discharge cycle characteristics can be obtained under high voltage. In addition, it is understood that the safety can be improved and the charge and discharge cycle characteristics can be improved by using a dinitrile compound which is originally poor in the charge and discharge cycle characteristics for the electrolytic solution.

According to the present invention, a non-aqueous secondary battery excellent in charge and discharge cycle characteristics at high voltage can be provided, and the non-aqueous secondary battery of the present invention is a secondary battery of small size, light weight, high capacity and high energy density. It can be used as a battery for portable electronic devices such as a mobile phone or a notebook personal computer requiring a battery, or a battery for an electric car.

DESCRIPTION OF SYMBOLS 10 laminated type lithium ion battery 11 exterior body 12 positive electrode external terminal 13 negative electrode external terminal

Claims

A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, comprising:
After charging to 4.5 V with 1/3 C current, the positive electrode after discharging to 3 V with 1/3 C current is washed with methyl ethyl carbonate and then vacuum dried, and then the surface of the positive electrode is subjected to X-rays When analyzed by photoelectron spectroscopy
In the surface of the positive electrode, the content ratio of oxygen atom is Ro (atomic%), the content ratio of fluorine atom is Rf (atomic%), and the content ratio of carbon atoms having 1s orbital bond energy of 289 to 291 eV is Rc (atomic% And if
A non-aqueous secondary battery characterized in that Rf / Ro is 0.05 or more and 1.3 or less, or Rc / Ro is 0.05 or more and 0.75 or less.
The non-aqueous secondary battery according to claim 1, satisfying any of the following (1) to (3) in the analysis of the surface of the positive electrode by X-ray photoelectron spectroscopy.
(1) The content ratio of nitrogen atoms in the surface of the positive electrode is 0.1 atomic percent or more and 1 atomic percent or less (2) The content ratio of phosphorus atoms in the surface of the positive electrode is 0.5 atomic percent or more and 10 atomic percent or less (3 The total content of cobalt, nickel, manganese and iron on the surface of the positive electrode is 0.1 atomic% or more and 15 atomic% or less
The surface of the positive electrode is a group consisting of lignin compounds, polyacid salts, monofluorophosphates, metaphosphates, pyrophosphates, diethylenetriaminepentaacetate, ethylenediaminetetraacetates, polypeptides or salts thereof, and polyallylamines The non-aqueous secondary battery according to claim 1, wherein the non-aqueous secondary battery is coated with at least one component selected from the group consisting of
The non-aqueous secondary battery according to claim 1, wherein the positive electrode contains at least one selected from a fluorine-containing compound and a carbonic acid compound.
The positive electrode includes a positive electrode mixture layer,
The non-aqueous secondary battery according to claim 1, wherein the porosity of the positive electrode mixture layer is 22% or more and 35% or less.
A method for producing the non-aqueous secondary battery according to any one of claims 1 to 5, comprising:
Preparing a treatment liquid to be applied to the surface of the positive electrode;
Applying the treatment liquid to the surface of the positive electrode,
The treatment liquid is selected from the group consisting of lignin compounds, polyacid salts, monofluorophosphates, metaphosphates, pyrophosphates, diethylenetriaminepentaacetates, ethylenediaminetetraacetates, polypeptides or salts thereof, and polyallylamines. A method of manufacturing a non-aqueous secondary battery comprising at least one selected component.
The positive electrode includes a positive electrode mixture layer,
The manufacturing method of the non-aqueous secondary battery of Claim 6 including the process of press-processing the said positive mix layer layer, and the process of apply | coating the said process liquid on the surface of the positive electrode mix layer by which the press process was carried out.
The method for manufacturing a non-aqueous secondary battery according to claim 7, wherein the porosity of the positive electrode mixture layer is set to 22% or more and 35% or less in the step of pressing the positive electrode mixture layer.
The concentration of the component in the treatment liquid is 0.01% by mass or more and 20% by mass or less,
The coating amount of the surface of the positive electrode of the treatment liquid, a dry component mass conversion of the treatment liquid, nonaqueous secondary of claim 6 is 0.0002 mg / cm 2 or more 0.5 mg / cm 2 or less How to make a battery.
A method for producing the non-aqueous secondary battery according to any one of claims 1 to 5, comprising:
At least one selected from the group consisting of lignin compounds, poly acid salts, monofluorophosphates, metaphosphates, pyrophosphates, diethylenetriamine pentaacetates, ethylenediaminetetraacetates, polypeptides or salts thereof, and polyallylamines Preparing a non-aqueous electrolyte containing the components of the species;
Assembling a battery using a positive electrode, a negative electrode, and the non-aqueous electrolyte;
And d) charging the assembled battery to a voltage of 4.35 V or higher and discharging the assembled battery.
A non-aqueous electrolyte for producing the non-aqueous secondary battery according to any one of claims 1 to 5.
The non-aqueous electrolytic solution according to claim 11, comprising at least one selected from a fluorine-containing compound and a carbonic acid compound.
The non-aqueous electrolytic solution according to claim 11, comprising a compound having two or more nitrile groups in the molecule.
The non-aqueous electrolytic solution according to claim 13, wherein the concentration of the compound having two or more nitrile groups in the molecule is 0.1% by mass or more and 50% by mass or less.
At least one selected from the group consisting of lignin compounds, poly acid salts, monofluorophosphates, metaphosphates, pyrophosphates, diethylenetriamine pentaacetates, ethylenediaminetetraacetates, polypeptides or salts thereof, and polyallylamines The non-aqueous electrolytic solution according to claim 11, comprising a component of a species.