JP2011138732A - Nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery for preventing the generation of gas during high temperature storage while maintaining battery performance and for preventing the degradation of battery capacity after high temperature storage. <P>SOLUTION: In the nonaqueous secondary battery wherein a positive electrode and a negative electrode are formed via electrolyte, a positive electrode active material in the positive electrode is coated with a polymer represented by formula I where Y is hydrogen, alkali metal or alkaline earth metal, Z<SB>1</SB>is a bivalent group having a substituted or unsubstituted phenylene group and/or an oxyphenylene group, m and n show the substitution number of a SO<SB>3</SB>Y group, m+n is 1-8, and x<SB>1</SB>/(x<SB>1</SB>+y<SB>1</SB>) is ≥0.001 and ≤1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous secondary battery such as a lithium ion battery.

  Non-aqueous secondary batteries such as lithium ion batteries have a high energy density, and are widely used in notebook personal computers, mobile phones and the like by taking advantage of their characteristics. In recent years, interest in electric vehicles has increased from the viewpoint of preventing global warming associated with an increase in carbon dioxide, and the application of lithium ion batteries as a power source has been studied. In particular, in the case of a lithium ion battery used for a portable device such as a notebook personal computer, higher capacity is required. Under such circumstances, development for increasing the capacity of batteries has been intensively advanced.

  A lithium ion battery is mainly composed of a positive electrode, a negative electrode, a separator, and an electrolyte. Further, the positive electrode has a positive electrode active material, a conductive material, and a binder, which are applied to an aluminum current collector. The negative electrode has a negative electrode active material, a binder, and, if necessary, a conductive material, and these are applied to a copper current collector for use. The increase in capacity of the lithium ion battery can be achieved, for example, by increasing the coating amount per unit area of the positive electrode and the negative electrode. However, if the coating amount is increased too much, the internal resistance increases and causes a decrease in battery performance. In addition, the positive electrode and the negative electrode are used by sandwiching a separator between the positive electrode and the negative electrode, winding it, and inserting it into a battery can. However, when the coating amount increases, the electrode breaks and the productivity decreases. Therefore, in order to increase the capacity of the battery, it is essential to increase the capacity of the positive electrode and the negative electrode active material itself.

On the other hand, LiCoO ₂ is often used as a conventional positive electrode active material. However, the capacity of the positive electrode single electrode that can be charged and discharged in the potential range of 4.3 V to 3.0 V is as low as about 150 mAh / g. Therefore, it is necessary to improve the material itself in order to further increase the capacity.

(Non-Patent Document 1) uses LiNi _0.74 Co _0.2 Al _0.06 O ₂ as a positive electrode active material, and considers increasing the capacity of the battery. This positive electrode active material can obtain a capacity of about 175 mAh / g in a potential range of 4.3 V to 3.0 V. In order to increase the capacity, it is effective to replace the transition metal of the positive electrode active material with Ni at a high rate.

  However, a lithium ion battery using a positive electrode active material substituted with Ni has a problem that when the battery is left at high temperature, gas is generated and the battery can expands. The cause of gas generation is mainly due to the decomposition of the electrolyte, and this phenomenon becomes remarkable in the positive electrode active material using Ni (Non-patent Document 2). The reason for this is considered that the positive electrode active material using Ni has high activity on the surface of the positive electrode active material and the electrolyte is easily decomposed. Moreover, when the lithium ion battery using the positive electrode active material containing Ni is stored at a high temperature, the battery capacity tends to be lower than that of other battery systems. This phenomenon is also considered to be caused by excessive decomposition of the electrolyte.

  In order to suppress the decomposition of the electrolyte, it is necessary to reduce the activity on the surface of the positive electrode active material. As a means for this, it is known to coat the surface of the positive electrode active material with a polymer. In this case, on the surface of the positive electrode active material, lithium ions move through the positive electrode interface when the battery is charged and discharged. Therefore, it is necessary that the polymer to be coated has ionic conductivity.

  (Patent Document 1) discloses a technique in which carboxymethyl cellulose is used as a polymer and a Ni-based positive electrode active material is coated. However, carboxymethyl cellulose has low ion conductivity, and if the coating thickness is increased, lithium ion migration at the positive electrode active material interface is hindered, which may reduce battery performance. Further, when the coating amount is reduced, there is a problem that the effect of suppressing gas generation is reduced.

JP 2006-236886 A

Electrochemistry, 71, No.12, p.1162 (2003) J. Electrochem.Soc., 1525 (11) A794 (2008)

  Accordingly, an object of the present invention is to provide a non-aqueous secondary battery in which gas generation during high-temperature storage is suppressed while maintaining battery performance in view of the above-described conventional situation. It is another object of the present invention to provide a non-aqueous secondary battery in which a decrease in battery capacity after high temperature storage is suppressed.

  Therefore, as a result of intensive studies by the present inventors, it was found that the above problems can be solved by coating the positive electrode active material with a polymer having a sulfone group represented by Formulas I to III, and the present invention was completed. did.

（式Ｉ中、Ｙは水素、アルカリ金属又はアルカリ土類金属であり、Ｚ_１は置換又は非置換のフェニレン基及び／又はオキシフェニレン基を有する２価の基であり、ｍ及びｎはＳＯ_３Ｙ基の置換数を示し、ｍ＋ｎが１〜８であり、ｘ_１／（ｘ_１＋ｙ_１）は０．００１以上１以下である）で表されるポリマーによって被覆されている前記非水二次電池。 That is, the gist of the present invention is as follows.
(1) In a nonaqueous secondary battery in which a positive electrode and a negative electrode are formed via an electrolyte, the positive electrode active material contained in the positive electrode is represented by the following formula I

(In Formula I, Y is hydrogen, alkali metal or alkaline earth metal, Z ₁ is a divalent group having a substituted or unsubstituted phenylene group and / or oxyphenylene group, and m and n are SO _3. The non-aqueous secondary coated with a polymer represented by the following formula: Y represents the number of substitutions, m + n is 1 to 8, and x ₁ / (x ₁ + y ₁ ) is from 0.001 to 1 battery.

（式ＩＩ中、Ｙは水素、アルカリ金属又はアルカリ土類金属であり、Ｚ_２は２価の基であり、Ａ_２はＨ、Ｃ、Ｎ、Ｏ、Ｃｌ、Ｂｒ、Ｆ、Ｓ及びＳｉから選択される一以上から構成される官能基であって、その官能基の一部がアルカリ金属又はアルカリ土類金属で置換されていても良く、Ｒ_２は水素又は炭素数１０以下の炭化水素基であり、ｘ_２／（ｘ_２＋ｙ_２）は０．００１以上１以下である）で表されるポリマーによって被覆されている前記非水二次電池。 (2) In the nonaqueous secondary battery in which the positive electrode and the negative electrode are formed via an electrolyte, the positive electrode active material contained in the positive electrode is represented by the following formula II

(In Formula II, Y is hydrogen, alkali metal or alkaline earth metal, Z ₂ is a divalent group, and A ₂ is from H, C, N, O, Cl, Br, F, S and Si. A functional group composed of one or more selected, a part of the functional group may be substituted with an alkali metal or an alkaline earth metal, and R ₂ is hydrogen or a hydrocarbon group having 10 or less carbon atoms And x ₂ / (x ₂ + y ₂ ) is 0.001 or more and 1 or less).

（式ＩＩＩ中、Ｙは水素、アルカリ金属又はアルカリ土類金属であり、Ｚ_３は２価の基であり、Ａ_３はＨ、Ｃ、Ｎ、Ｏ、Ｃｌ、Ｂｒ、Ｆ、Ｓ及びＳｉから選択される一以上から構成される官能基であって、その官能基の一部がアルカリ金属又はアルカリ土類金属で置換されていても良く、Ｒ_３は水素又は炭素数１０以下の炭化水素基であり、ｐはＳＯ_３Ｙ基の置換数を示し、ｐが１〜５であり、ｘ_３／（ｘ_３＋ｙ_３）は０．００１以上１以下である）で表されるポリマーによって被覆されている前記非水二次電池。 (3) In the nonaqueous secondary battery in which the positive electrode and the negative electrode are formed via an electrolyte, the positive electrode active material contained in the positive electrode is represented by the following formula III

(In Formula III, Y is hydrogen, alkali metal or alkaline earth metal, Z ₃ is a divalent group, and A ₃ is from H, C, N, O, Cl, Br, F, S and Si. A functional group composed of one or more selected, a part of the functional group may be substituted with an alkali metal or an alkaline earth metal, and R ₃ is hydrogen or a hydrocarbon group having 10 or less carbon atoms P represents the number of substitutions of SO ₃ Y group, p is 1 to 5, and x ₃ / (x ₃ + y ₃ ) is 0.001 or more and 1 or less). The non-aqueous secondary battery.

(4) The non-aqueous two according to any one of the above (1) to (3), wherein the weight ratio of the positive electrode active material to the polymer (weight of polymer / weight of positive electrode active material × 100) is 0.01 to 5. Next battery.

  According to the present invention, by using a positive electrode active material coated with a polymer represented by Formula I to Formula III, gas generation during high-temperature storage can be achieved without deteriorating battery performance while maintaining ionic conductivity. Can be suppressed. Furthermore, a decrease in battery capacity after high-temperature storage can also be suppressed.

Hereinafter, the present invention will be described in detail.
In the nonaqueous secondary battery of the present invention, the positive electrode and the negative electrode are formed via an electrolyte. The positive electrode includes a positive electrode active material, a conductive material, and a binder, and these are applied to a current collector such as aluminum. The negative electrode includes a negative electrode active material, a binder, and, if necessary, a conductive material, and these are applied to a current collector such as copper.

  In this invention, in one Embodiment, the positive electrode active material contained in a positive electrode is coat | covered with the polymer represented by the following formula I.

In the above formula I, Y is hydrogen, an alkali metal or an alkaline earth metal, and Z ₁ is a divalent group having a substituted or unsubstituted phenylene group and / or oxyphenylene group. M and n represent the number of substitutions of the SO ₃ Y group, and m + n is 1 to 8, preferably 1 to 4. A specific example is a case where m is 1 and n is 2. _{Further, x 1 / (x 1 +} y 1) is 0.001 or more and 1 or less, and preferably 0.1 to 0.9. When x ₁ / (x ₁ + y ₁ ) is 1, the substance of formula I is a homopolymer composed only of x ₁ components.

As the alkali metal and alkaline earth metal, Li, Na, K, Mg, Ca, Sr, Ba and the like are preferably used. In addition, as a divalent group having a phenylene group and / or an oxyphenylene group, a phenylene group (—C ₆ H ₄ —), an oxyphenylene group (—C ₆ H ₄ —O—), a biphenyleneoxy group (—C _{6 H 4 -C 6 H 4 -O} -), - C 6 H 4 -O-C 6 H 4 -O- group, and the like. These groups are other groups in the chain, for example, alkylene groups having 1 to 4 carbon atoms such as methylene group and ethylene group, alkenylene groups such as 1,2-vinylene group, and arylene groups such as 1,8-naphthylene group. Group, carbonyl group, ether group, ester group, amide group, sulfide group, disulfide group and the like may be contained. In addition, the benzene ring of the phenylene group and the oxyphenylene group may be unsubstituted or substituted. Examples of the substituent include alkyl groups having 1 to 4 carbon atoms such as a methyl group and an ethyl group, a hydroxy group, a methoxy group, Examples thereof include an alkoxy group having 1 to 4 carbon atoms such as an ethoxy group, and a halogen atom such as fluorine, chlorine, bromine and iodine. As Z _1, by selecting an organic group as described above, it is possible to improve oxidation resistance of the polymer of formula I, to maintain battery performance.

  When the substance represented by the formula I is a copolymer, any of a random copolymer, a block copolymer, and an alternating copolymer may be used. Further, the weight average molecular weight of the polymer of the formula I is not particularly limited, but is preferably about 300 to 5000000. The weight average molecular weight was determined by detecting with a differential refractometer in a solvent THF using a GPC analyzer using GL-R440 + R150 + R400M manufactured by Gelpack as a column, and converting it using polystyrene as a standard substance.

  In another embodiment, the positive electrode active material contained in the positive electrode is coated with a polymer represented by the following formula II.

In formula II, Y is hydrogen, alkali metal or alkaline earth metal, Z ₂ is a divalent group, and A ₂ is selected from H, C, N, O, Cl, Br, F, S and Si. One or more of these functional groups may be substituted with an alkali metal or an alkaline earth metal. R ₂ is hydrogen or a hydrocarbon group having 10 or less carbon atoms. Further, x ₂ / (x ₂ + y ₂ ) is 0.001 or more and 1 or less, preferably 0.1 or more and 0.9 or less. When x ₂ / (x ₂ + y ₂ ) is 1, the substance of formula II is a homopolymer composed only of x ₂ components.

As the alkali metal and alkaline earth metal, Li, Na, K, Mg, Ca, Sr, Ba and the like are preferably used. Z ₂ is applicable as long as it is a divalent group derived from a polymerizable monomer that can serve as a copolymer component. Specifically, it is a linear or branched alkylene group having 1 to 6 carbon atoms, 6 linear or branched alkenylene groups, or substituted or unsubstituted arylene groups formed by removing one hydrogen atom from a monocyclic or condensed polycyclic aryl group having 6 to 24 carbon atoms. . In these divalent groups, one or a plurality of other groups or atoms may be present between the carbon atoms. Examples of other groups or atoms include an etheric oxygen atom, a carbonyl group, an ester group, an amide group, and a sulfide group.

  Examples of the alkylene group include methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, 1-methylethylene group, 2-methylethylene group, 1-methyltrimethylene group, 2-methyltrimethylene group. 1,1-dimethylethylene group, 2-ethyltrimethylene and the like. Examples of alkenylene groups include vinylene, propenylene, butenylene, pentenylene, 1-methylvinylene, 1-methylpropenylene, 2-methylpropenylene, 1-methylpentenylene, 3 -A methylpentenylene group, 1-ethylvinylene group, 1-ethylpropenylene group, etc. are mentioned.

  Furthermore, examples of the monocyclic or condensed polycyclic aryl group having 6 to 24 carbon atoms include phenyl group, 1-naphthyl group, 2-naphthyl group, 1-anthryl group, 9-anthryl group, 2-phenanthryl group, 3 -Phenanthryl group, 9-phenanthryl group, 4-biphenyl group and the like can be mentioned. Examples of the substituent for the arylene group include alkyl groups having 1 to 4 carbon atoms such as a methyl group and an ethyl group, alkoxy groups having 1 to 4 carbon atoms such as a hydroxy group, a methoxy group, and an ethoxy group, fluorine, and chlorine. , Halogen atoms such as bromine and iodine.

A ₂ is a functional group composed of one or more selected from H, C, N, O, Cl, Br, F, S and Si, and is appropriately selected from the viewpoint of improving the adhesion of the copolymer to the positive electrode active material. Selected. Specific examples of A ₂ include a chain or cyclic saturated or unsaturated hydrocarbon group, alkoxy group, acyl group, hydroxy group, amino group, cyano group, sulfonyl group, nitroyl group, thiocarbonyl group, thionitrosyl group, tri Examples thereof include an alkylsilyl group.

Furthermore, examples of the hydrogen represented by R ₂ or the hydrocarbon group having 10 or less carbon atoms include hydrogen, an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, and an aryl group such as a phenyl group. . Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, and a methyl group and an ethyl group are particularly preferable. Examples of the alkenyl group include a vinyl group.

  When the substance represented by Formula II is a copolymer, any of a random copolymer, a block copolymer, and an alternating copolymer may be used. Moreover, the weight average molecular weight of the polymer of Formula II is not particularly limited, but is preferably about 300 to 5000000. The weight average molecular weight was obtained by detecting with a differential refractometer in a solvent THF with a GPC analyzer using GL-R440 + R450 + R400M manufactured by Gelpack as a column, and converting it using polystyrene as a standard substance.

  In yet another embodiment, the positive electrode active material contained in the positive electrode is coated with a polymer represented by the following formula III.

In formula III, Y is hydrogen, alkali metal or alkaline earth metal, Z ₃ is a divalent group, and A ₃ is selected from H, C, N, O, Cl, Br, F, S and Si. One or more of these functional groups may be substituted with an alkali metal or an alkaline earth metal. R ₃ is hydrogen or a hydrocarbon group having 10 or less carbon atoms. P represents the number of substitutions of the SO ₃ Y group. Specifically, p is 1 to 5, preferably 1 to 3. Further, x ₃ / (x ₃ + y ₃ ) is 0.001 or more and 1 or less, preferably 0.1 or more and 0.9 or less. When x ₃ / (x ₃ + y ₃ ) is 1, the substance of formula III is a homopolymer composed only of x ₃ components.

As the alkali metal and alkaline earth metal, Li, Na, K, Mg, Ca, Sr, Ba and the like are preferably used. Z ₃ is applicable as long as it is a divalent group derived from a polymerizable monomer that can be a copolymer component. Specifically, it is a linear or branched alkylene group having 1 to 6 carbon atoms, 6 linear or branched alkenylene groups, or substituted or unsubstituted arylene groups formed by removing one hydrogen atom from a monocyclic or condensed polycyclic aryl group having 6 to 24 carbon atoms. . In these divalent groups, one or a plurality of other groups or atoms may be present between the carbon atoms. Examples of other groups or atoms include an etheric oxygen atom, a carbonyl group, an ester group, an amide group, and a sulfide group.

  Examples of the alkylene group include methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, 1-methylethylene group, 2-methylethylene group, 1-methyltrimethylene group, 2-methyltrimethylene group. 1,1-dimethylethylene group, 2-ethyltrimethylene and the like. Examples of alkenylene groups include vinylene, propenylene, butenylene, pentenylene, 1-methylvinylene, 1-methylpropenylene, 2-methylpropenylene, 1-methylpentenylene, 3 -A methylpentenylene group, 1-ethylvinylene group, 1-ethylpropenylene group, etc. are mentioned.

  Furthermore, examples of the monocyclic or condensed polycyclic aryl group having 6 to 24 carbon atoms include phenyl group, 1-naphthyl group, 2-naphthyl group, 1-anthryl group, 9-anthryl group, 2-phenanthryl group, 3 -Phenanthryl group, 9-phenanthryl group, 4-biphenyl group and the like can be mentioned. Examples of the substituent for the arylene group include alkyl groups having 1 to 4 carbon atoms such as a methyl group and an ethyl group, alkoxy groups having 1 to 4 carbon atoms such as a hydroxy group, a methoxy group, and an ethoxy group, fluorine, and chlorine. , Halogen atoms such as bromine and iodine.

A ₃ is a functional group composed of one or more selected from H, C, N, O, Cl, Br, F, S and Si, and is appropriately selected from the viewpoint of improving the adhesion of the copolymer to the positive electrode active material. Selected. Specific examples of A ₃ include a linear or cyclic saturated or unsaturated hydrocarbon group, alkoxy group, acyl group, hydroxy group, amino group, cyano group, sulfonyl group, nitroyl group, thiocarbonyl group, thionitrosyl group, tri Examples thereof include an alkylsilyl group.

Furthermore, examples of the hydrogen represented by R ₃ or the hydrocarbon group having 10 or less carbon atoms include hydrogen, an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, and an aryl group such as a phenyl group. . Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, and a methyl group and an ethyl group are particularly preferable. Examples of the alkenyl group include a vinyl group.

  When the substance represented by Formula III is a copolymer, any of a random copolymer, a block copolymer, and an alternating copolymer may be used. Further, the weight average molecular weight of the polymer of the formula III is not particularly limited, but is preferably about 300 to 5000000. The weight average molecular weight was obtained by detecting with a differential refractometer in a solvent THF with a GPC analyzer using GL-R440 + R450 + R400M manufactured by Gelpack as a column, and converting it using polystyrene as a standard substance.

As the positive electrode active material, lithium ions are applicable to any capable of absorbing and desorbing material, for _{example, LiNi x Co y O 2 (} x + y = 1), or _{LiNi p Co q M r O 2} (p + q + r = 1 , M is B, Mg, Al, Si, P, V, Mn, Fe, Cu, Zn, Sr, In, Sn, and at least one element selected from the group consisting of lanthanoid elements). More _{specifically, LiCoO 2, LiNiO 2, LiMn} 2 O 4, LiNi 0.7 Co 0.3 O 2 and the like.

  As a method of coating the positive electrode active material with the polymer of the above formulas I to III, for example, the following method can be used. That is, a method in which a positive electrode active material is mixed and dried in an aqueous solution in which a polymer of Formula I to Formula III is dissolved, or the polymer and the positive electrode active material are mechanically mixed, and water is added to the resulting mixture and then dried. Or a method of spraying and drying the polymer dissolved in water on the positive electrode active material. At this time, an organic solvent can be used instead of water. Alternatively, the positive electrode active material is coated by adding the polymer of formula I to formula III to the slurry for preparing the positive electrode composition (including the positive electrode active material, the conductive material and the binder) to be applied to the current collector. May be.

  The weight ratio of the positive electrode active material to the polymer (the weight of the polymer / the weight of the positive electrode active material × 100) when the positive electrode active material is coated with the polymer of the formulas I to III depends on the gas generation suppression effect and the battery performance. It is set as appropriate in consideration of balance. Specifically, a range of 0.01 to 5 is appropriate, preferably 0.05 to 1, and more preferably 0.08 to 0.5.

  As the conductive material in the positive electrode, any material having conductivity can be applied. For example, carbon blacks such as ketjen black, acetylene black, channel black, furnace black, thermal black, natural graphite, artificial graphite, Examples thereof include graphites such as expanded graphite, conductive fibers such as carbon fibers and metal fibers, metal powders such as copper, aluminum, nickel and silver, and conductive polymers such as polyphenylene derivatives. Any of these may be used alone or in combination.

  The binder in the positive electrode can be appropriately selected from various thermoplastic resins and thermosetting resins, and is not particularly limited. Specific examples include polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoro. Propylene copolymer, ethylene-tetrafluoroethylene copolymer, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, fluorine And vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer and ethylene-acrylic acid copolymer. Any of these may be used alone or in combination.

  Examples of the current collector in the positive electrode include a metal plate such as aluminum, copper, stainless steel, and nickel, or a metal mesh.

  The positive electrode was prepared by mixing a positive electrode active material coated with the above-mentioned polymers of Formulas I to III with a conductive material and a binder and adding an appropriate solvent to form a paste-like positive electrode composition. It can be applied to the surface, dried, and compressed to increase the electrode density as necessary. Examples of the solvent for preparing the paste include N-methyl-2-pyrrolidone.

  In addition, as the negative electrode active material in the non-aqueous secondary battery of the present invention, a graphitized material obtained from natural graphite, petroleum coke, coal pitch coke, etc. is heat-treated at a high temperature of 2500 ° C. or higher, mesophase carbon, Examples thereof include crystalline carbon, carbon fiber, metals such as lithium, silver, aluminum, tin, silicon, indium, gallium, and magnesium, or alloys thereof, and materials having the above metal supported on the surface of carbon particles. The metal oxide may be used as a negative electrode active material. Furthermore, lithium titanate can also be used.

  A negative electrode is prepared by mixing a negative electrode active material with a binder and, if necessary, a conductive material and adding a suitable solvent to form a paste-like negative electrode composition on the surface of a current collector, followed by drying. And it can compress and form so that an electrode density may be raised as needed. Note that the same material as the positive electrode can be used for the conductive material, the binder, and the current collector.

  The electrolyte is obtained by dissolving a supporting electrolyte in a nonaqueous solvent. The nonaqueous solvent is not particularly limited as long as it can dissolve the supporting electrolyte, but the following solvents are preferably used. That is, organic solvents such as diethyl carbonate, dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, propylene carbonate, γ-butyl lactone, tetrahydrofuran, and dimethoxyethane are preferable, and any one or a mixture of two or more of these may be used. it can. Further, if necessary, a compound having an unsaturated double bond in the molecule, such as vinylene carbonate, or an aromatic compound such as cyclohexylbenzene or biphenyl may be added to the electrolyte.

The supporting electrolyte is not particularly limited as long as it is soluble in a non-aqueous solvent, but suitable examples include LiPF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₆ SO ₂ ) ₂ , LiClO _4. , LiBF ₄ , LiAsF ₆ , LiI, LiBr, LiSCN, Li ₂ B ₁₀ Cl ₁₀ , LiCF ₃ CO _{2 and the} like, and any one or a mixture of two or more of these may be used.

  The nonaqueous secondary battery of the present invention may include a separator between the negative electrode and the positive electrode. As the separator, polymer materials such as polyolefin, polyamide, and polyester, glass cloth made of fibrous glass fibers, and the like can be used. In particular, polyolefin is preferably used because it does not adversely affect the battery. Examples of such polyolefin include polyethylene, polypropylene, and the like, and those films can be used in an overlapping manner. Further, the air permeability (sec / 100 ml) of the separator is suitably about 10 to 1000, preferably 50 to 800, particularly preferably 90 to 700.

  The shape of the nonaqueous secondary battery of the present invention is not particularly limited, but can be, for example, a button type, a sheet type, a laminated type, a cylindrical type, a rectangular type, or the like. Further, a plurality of such non-aqueous secondary batteries can be connected in series and used as a power source for an electric vehicle.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, it is not limited to these.

  In Examples 1 to 11 and Comparative Examples 1 and 2, non-aqueous secondary batteries (lithium ion batteries) were produced according to the following procedure, and performance was evaluated.

(Preparation of positive electrode)
A positive electrode active material coated with a polymer (only polymer in Comparative Example 1 has no polymer), a conductive material (graphite manufactured by Nippon Graphite Co., Ltd., trade name: SP270), and a binder (polyvinylidene fluoride manufactured by Kureha Chemical Industry Co., Ltd., trade name: KF1120) The mixture was mixed at a weight ratio of 95: 2.5: 2.5 and charged into N-methyl-2-pyrrolidone to prepare a slurry solution. The slurry was applied to an aluminum foil having a thickness of 20 μm by a doctor blade method and dried. The coating amount was 200 g / m ² . Then, it pressed and cut | judged to the magnitude | size of 23 cm < ² >, and produced the positive electrode. Note that LiNi _0.8 Co _0.15 Al _0.05 O ₂ was used as the positive electrode active material.

(Preparation of negative electrode)
Graphite and the same binder as in the case of the positive electrode were mixed at a weight ratio of 95: 5 and charged into N-methyl-2-pyrrolidone to prepare a slurry solution. This slurry was applied to a copper foil having a thickness of 10 μm by a doctor blade method and dried. It pressed so that the bulk density of the composition on copper foil might be 1.0 g / cm < ³ >, and it cut | judged to the magnitude | size of 24 cm < ² >, and produced the negative electrode.

(Production of non-aqueous secondary battery)
A separator made of polyolefin was inserted between the positive electrode and the negative electrode to form an electrode group, and an electrolyte was injected there. Subsequently, the non-aqueous secondary battery was produced by enclosing with an aluminum laminate. Then, the battery was initialized by repeating charging / discharging 3 cycles. The battery was charged at a current value of 7 mA up to a preset upper limit voltage. The discharge was performed at a current value of 7 mA up to a preset lower limit voltage. The upper limit voltage was 4.2V and the lower limit voltage was 2.5V.

(Non-aqueous secondary battery evaluation method)
1. Initial capacity of non-aqueous secondary battery After the battery was initialized, it was charged and discharged for one cycle. The discharge capacity obtained at that time was defined as the initial capacity of the battery. As the charge / discharge conditions, the above-described initialization conditions were used.

2. High temperature storage test After confirming the initial capacity, the battery was charged to 4.2 V at a current value of 7 mA. Then, the battery was put into a 85 degreeC thermostat and preserve | saved for 24 hours. After storage at high temperature, the battery was removed and cooled to room temperature. The battery was once discharged to 2.5 V and then charged and discharged again. The discharge capacity obtained at that time was taken as the battery capacity after the high-temperature storage test. The capacity retention rate (%) was defined by dividing the battery capacity after this high-temperature storage test by the initial battery capacity.

  Furthermore, a battery for evaluating the gas generation amount was separately prepared, and similarly a high temperature storage test was performed. After the high temperature storage test, the battery was taken out, cooled to room temperature, and then the amount of gas generated was measured by collecting the gas with a syringe. The measurement results of the following Examples 1 to 11 and Comparative Examples 1 and 2 are shown together in Table 1.

(Example 1)
Polymer 1 (in formula II, Y: Na, —Z ₂ (A ₂ ) —: —CH (COONa) —CH ₂ —, R ₂ : methyl group, x ₂ / (x ₂ + y ₂ ): 0.5) 10 mg was dissolved in 100 g of water. Subsequently, 10 g of the positive electrode active material (LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) was added to the aqueous solution of polymer 1. Thereafter, water was evaporated in an oil bath heated to 95 ° C., and the polymer 1 was coated on the positive electrode active material. A positive electrode was produced using the positive electrode active material coated with this polymer 1 to obtain a non-aqueous secondary battery. The initial capacity of the battery was 70 mAh. The capacity retention rate after the high temperature storage test was 90%, and the gas generation amount was 0.7 ml.

(Example 2)
Instead of the polymer 1, the polymer 2 (in formula II, Y: Na, —Z ₂ (A ₂ ) —: —CH (COONa) —CH ₂ —, R ₂ : methyl group, x ₂ / (x ₂ + y ₂ ): A positive electrode active material was treated in the same manner as in Example 1 except that 0.01) was used, and a nonaqueous secondary battery was produced. The initial capacity of the battery was 70 mAh. The capacity retention rate after the high temperature storage test was 85%, and the amount of gas generated was 0.9 ml.

(Example 3)
A non-aqueous secondary battery was produced by treating the positive electrode active material in the same manner as in Example 1 except that the amount of polymer 1 was 200 mg. The initial capacity of the battery was 65 mAh. The capacity retention rate after the high temperature storage test was 88%, and the gas generation amount was 0.7 ml.

Example 4
Instead of polymer 1, polymer 3 (in formula III, Y: Na, —Z ₃ (A ₃ ) —: —CH (COONa) —CH ₂ —, R ₃ : methyl group, x ₃ / (x ₃ + y ₃ ): A positive electrode active material was treated in the same manner as in Example 1 except that 0.5) was used, and a non-aqueous secondary battery was produced. The initial capacity of the battery was 70 mAh. The capacity retention rate after the high temperature storage test was 90%, and the gas generation amount was 0.8 ml.

(Example 5)
In polymer 4 (formula I, Y: H, m + n: 2, -Z 1 -: biphenylene group _{(-C 6 H 4 -C 6 H} 4 -O -), x 1 / (x 1 + y 1) = 1 0.0) 10 mg was dissolved in 100 g of N-methylpyrrolidone. 10 g of the positive electrode active material (LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) was added to the polymer 4 solution. Thereafter, N-methylpyrrolidone was distilled off with an evaporator to coat polymer 4 on the positive electrode active material. A positive electrode was produced using the positive electrode active material coated with this polymer 4 to obtain a non-aqueous secondary battery. The initial capacity of the battery was 70 mAh. The capacity retention rate after the high temperature storage test was 92%, and the gas generation amount was 0.6 ml.

(Example 6)
A positive electrode active material was treated in the same manner as in Example 5 except that the amount of the polymer 4 was changed to 1 mg, and a nonaqueous secondary battery was produced. The initial capacity of the battery was 70 mAh. The capacity retention rate after the high temperature storage test was 90%, and the amount of gas generated was 1.0 ml.

(Example 7)
A positive electrode active material was treated in the same manner as in Example 5 except that the amount of the polymer 4 was changed to 200 mg, and a nonaqueous secondary battery was produced. The initial capacity of the battery was 65 mAh. The capacity retention rate after the high temperature storage test was 85%, and the amount of gas generated was 0.7 ml.

(Example 8)
Instead of the polymer 1, the polymer 5 (in formula II, Y: Na, —Z ₂ (A ₂ ) —: —CH (COONa) —CH ₂ —, R ₂ : methyl group, x ₂ / (x ₂ + y ₂ ): A positive electrode active material was treated in the same manner as in Example 1 except that 0.85) was used, and a nonaqueous secondary battery was produced. The initial capacity of the battery was 69 mAh. The capacity retention rate after the high temperature storage test was 88%, and the gas generation amount was 0.8 ml.

(Comparative Example 1)
A non-aqueous secondary battery was produced using a positive electrode active material not coated with a polymer. The initial capacity of the battery was 70 mAh. The capacity retention rate after the high temperature storage test was 70%, and the amount of gas generated was 1.4 ml.

(Comparative Example 2)
The positive electrode active material was treated in the same manner as in Example 1 except that sodium polyacrylate (SO ₃ Y in Formula II was COONa and y ₂ was 0) was used in place of polymer 1. A non-aqueous secondary battery was produced. The initial capacity of the battery was 67 mAh. The capacity retention rate after the high temperature storage test was 85%, and the amount of gas generated was 1.2 ml. The capacity retention rate was relatively low, and the amount of gas generation was the second largest after Comparative Example 1.

Claims (4)

In the nonaqueous secondary battery in which the positive electrode and the negative electrode are formed via an electrolyte, the positive electrode active material contained in the positive electrode is represented by the following formula I

(In Formula I, Y is hydrogen, alkali metal or alkaline earth metal, Z ₁ is a divalent group having a substituted or unsubstituted phenylene group and / or oxyphenylene group, and m and n are SO _3. The non-aqueous secondary coated with a polymer represented by the following formula: Y represents the number of substitutions, m + n is 1 to 8, and x ₁ / (x ₁ + y ₁ ) is from 0.001 to 1 battery. In the nonaqueous secondary battery in which the positive electrode and the negative electrode are formed via an electrolyte, the positive electrode active material contained in the positive electrode is represented by the following formula II

(In Formula II, Y is hydrogen, alkali metal or alkaline earth metal, Z ₂ is a divalent group, and A ₂ is from H, C, N, O, Cl, Br, F, S and Si. A functional group composed of one or more selected, a part of the functional group may be substituted with an alkali metal or an alkaline earth metal, and R ₂ is hydrogen or a hydrocarbon group having 10 or less carbon atoms And x ₂ / (x ₂ + y ₂ ) is 0.001 or more and 1 or less). In the nonaqueous secondary battery in which the positive electrode and the negative electrode are formed via an electrolyte, the positive electrode active material contained in the positive electrode is represented by the following formula III

(In Formula III, Y is hydrogen, alkali metal or alkaline earth metal, Z ₃ is a divalent group, and A ₃ is from H, C, N, O, Cl, Br, F, S and Si. A functional group composed of one or more selected, a part of the functional group may be substituted with an alkali metal or an alkaline earth metal, and R ₃ is hydrogen or a hydrocarbon group having 10 or less carbon atoms P represents the number of substitutions of SO ₃ Y group, p is 1 to 5, and x ₃ / (x ₃ + y ₃ ) is 0.001 or more and 1 or less). The non-aqueous secondary battery.   The non-aqueous secondary battery according to claim 1, wherein a weight ratio of the positive electrode active material to the polymer (weight of polymer / weight of positive electrode active material × 100) is 0.01 to 5. 5.