JP2013179041A - Composition for secondary battery electrode and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a composition for a secondary battery electrode, simultaneously achieving storage stability of a slurry, binding properties, and electrode flexibility, and further improving battery cycle characteristics; and a secondary battery.SOLUTION: A composition for a secondary battery electrode includes an active material, a dispersion medium comprising water as a main component and a resin, and the resin has at least one of the functional groups represented by formulae (A1) to (A3) on the side chain. [In the formulae, Rrepresents an alkyl group, an alkenyl group, an alkynyl group or an aryl group, R-Reach independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or an atom group which may form a salt with O.]

Description

  The present invention relates to a composition for a secondary battery electrode and a secondary battery using the same.

  Recently, secondary batteries called lithium ion batteries, which are attracting attention, use secondary batteries (so-called lithium ion secondary batteries) that use insertion and extraction of lithium in charge and discharge reactions, and precipitation and dissolution of lithium. They are roughly classified into secondary batteries (so-called lithium metal secondary batteries). These realize charging and discharging with a large energy density compared to lead batteries and nickel cadmium batteries. In recent years, application to portable electronic devices such as camera-integrated VTRs (video tape recorders), mobile phones, and notebook personal computers has become widespread by utilizing this characteristic. With the further expansion of applications, the development of secondary batteries that are lighter and have higher energy density as power sources for portable electronic devices is being promoted. Furthermore, in recent years, miniaturization, long life, and high safety have been strongly demanded.

  As an electrode of a lithium ion secondary battery or a lithium metal secondary battery (hereinafter collectively referred to simply as a lithium secondary battery), an active material constituting a positive electrode and a negative electrode and a binder resin are usually used. A mixed and cured member is applied. Patent Document 1 listed below discloses a composition containing an (meth) acrylic acid ester, acrylonitrile, and a vinyl monomer having an acid component as a binder component contained in an electrode composition. Thus, it is possible to provide a non-aqueous secondary battery having good charge / discharge cycle characteristics, high capacity, and good first cycle efficiency / manufacturability. Further, Patent Document 2 below discloses a material that uses a paste containing a negative electrode active material, a resin having an acidic functional group, and PVDF in an organic solvent. Thus, an electrode in which the negative electrode active material is sufficiently dispersed and variation in thickness and density is small can be produced.

JP-A-8-287915 JP 2010-61930 A

The technique disclosed in Patent Document 1 is based on the results of the applicant's research and development. On the other hand, the latest research has revealed that the above technology has been further improved to achieve high performance, especially in combination with a negative electrode active material composed of LTO (lithium titanate), which has recently been adopted. Binder resins that exhibit good performance have been found.
The present invention has been made on the basis of such research findings, and a secondary battery electrode composition and a secondary battery that simultaneously achieve slurry storage stability, binding properties, electrode flexibility, and improve battery cycle characteristics. The purpose is to provide. It is another object of the present invention to provide a secondary battery electrode composition and a secondary battery that are particularly compatible with a negative electrode active material made of LTO (lithium titanate).

The above problem has been solved by the following means.
(1) An active material, a dispersion medium containing water as a main component, and a resin, wherein the resin has at least one functional group of formulas (A1) to (A3) in a side chain. Secondary battery electrode composition.

〔式中、Ｒ^１１は、アルキル基、アルケニル基、アルキニル基、またはアリール基である。Ｒ^１２〜Ｒ^１６はそれぞれ独立に水素原子、アルキル基、アルケニル基、アルキニル基、アリール基、またはＯ⁻と塩を形成し得る原子もしくは原子群を表す。〕
（２）前記樹脂が下記式（１）で表される構造単位を含む（１）に記載の二次電池電極用組成物。

[Wherein R ¹¹ represents an alkyl group, an alkenyl group, an alkynyl group, or an aryl group. R ^{12 to} R ¹⁶ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or atomic group that can form a salt with O ⁻ . ]
(2) The composition for secondary battery electrodes according to (1), wherein the resin includes a structural unit represented by the following formula (1).

〔式中、Ｒは水素原子、ハロゲン原子、またはアルキル基を表す。Ｗは二価の連結基を表す。Ｚ^１１は前記式（Ａ１）〜（Ａ３）から選択される官能基を表す。〕
（３）前記樹脂が下記式（２）で表される構造単位と、（メタ）アクリル酸エステルモノマー由来の構造単位と、（メタ）アクリロニトリルモノマー由来の構造単位とを含む（１）または（２）に記載の二次電池電極用組成物。

[Wherein, R represents a hydrogen atom, a halogen atom, or an alkyl group. W represents a divalent linking group. Z ¹¹ represents a functional group selected from the above formulas (A1) to (A3). ]
(3) The resin includes a structural unit represented by the following formula (2), a structural unit derived from a (meth) acrylic acid ester monomer, and a structural unit derived from a (meth) acrylonitrile monomer (1) or (2 ) The composition for a secondary battery electrode according to.

〔式中、Ｒは水素原子、ハロゲン原子、またはアルキル基を表す。Ｌは鎖長が２原子以上の二価の連結基を表す。Ｚ^１２は−ＰＯ（ＯＲ^２１）_２または−ＯＰＯ（ＯＲ^２１）_２を表す。Ｒ^２１はそれぞれ独立に水素原子、アルキル基、アルケニル基、アルキニル基、アリール基、またはＯ⁻と塩を形成し得る原子もしくは原子群を表す。〕
（４）式（２）について、Ｒがメチル基であり、Ｌが繰り返し数１〜６のオリゴエチレンオキシ基または繰り返し数が１〜６のオリゴプロピレンオキシ基であり、Ｚ^１２が−ＰＯ（ＯＨ）_２である（３）に記載の二次電池電極用組成物。
（５）前記樹脂が下記式（３）で表される構造単位を含む（１）〜（４）のいずれか一項に記載の二次電池電極用組成物。

[Wherein, R represents a hydrogen atom, a halogen atom, or an alkyl group. L represents a divalent linking group having a chain length of 2 atoms or more. Z ¹² represents —PO (OR ²¹ ) ₂ or —OPO (OR ²¹ ) ₂ . R ²¹ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or group of atoms that can form a salt with O ⁻ . ]
(4) In formula (2), R is a methyl group, L is an oligoethyleneoxy group having 1 to 6 repeats or an oligopropyleneoxy group having 1 to 6 repeats, and Z ¹² is —PO (OH ₂ ) The composition for secondary battery electrodes according to (3), which is ₂ .
(5) The composition for secondary battery electrodes as described in any one of (1)-(4) in which the said resin contains the structural unit represented by following formula (3).

〔式中、Ｒは前記式（１）と同義である。Ｌ^１１、Ｌ^１２はそれぞれ独立に鎖長が２原子以上の二価の連結基を表す。Ｚ^１３は−ＰＯ（ＯＲ^２２）−または−ＯＰＯ（ＯＲ^２３）−を表す。Ｒ^２２およびＲ^２３はそれぞれ独立に水素原子、アルキル基、アルケニル基、アルキニル基、アリール基、またはＯ⁻と塩を形成し得る原子もしくは原子群を表す。〕
（６）前記樹脂における前記式（１）で表される構造単位の共重合比［Ｍ１］が、全体を１００（質量基準）としたときに１〜５０である（２）〜（５）のいずれか一項に記載の二次電池電極用組成物。
（７）（メタ）アクリル酸エステルモノマー由来の繰り返し単位の共重合比［Ｍａ］、（メタ）アクリロニトリル由来の繰り返し単位の共重合比［Ｍｂ］、前記式（１）で表される構造単位の共重合比［Ｍ１］が、Ｍａ：Ｍｂ：Ｍ１ ＝ ２０〜９５：１〜４０：１〜４０（全体が１００：質量基準）である（２）〜（６）のいずれか一項に記載の二次電池電極用組成物。
（８）前記樹脂が、平均粒径１０〜５００ｎｍの粒子状である（１）〜（７）のいずれか一項に記載の二次電池電極用組成物。
（９）前記活物質がチタン酸リチウムである（１）〜（８）のいずれか一項に記載の二次電池電極用組成物。
（１０）前記樹脂を、活物質１００質量部に対して、０．１質量部以上１０質量部以下で含有させた（１）〜（９）のいずれか一項に記載の二次電池電極用組成物。
（１１）集電体の少なくとも一つの面に、（１）〜（１０）のいずれか一項に記載の二次電池電極用組成物の膜が形成された電極合材。
（１２）（１１）に記載の電極合材を正極および／または負極として備えた二次電池。

[Wherein, R has the same meaning as the formula (1). L ¹¹ and L ¹² each independently represents a divalent linking group having a chain length of 2 atoms or more. Z ¹³ represents —PO (OR ²² ) — or —OPO (OR ²³ ) —. R ²² and R ²³ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or a group of atoms that can form a salt with O ⁻ . ]
(6) The copolymerization ratio [M1] of the structural unit represented by the formula (1) in the resin is 1 to 50 when the whole is 100 (mass basis). The composition for secondary battery electrodes as described in any one of Claims.
(7) Copolymerization ratio [Ma] of repeating units derived from (meth) acrylic acid ester monomers, Copolymerization ratio [Mb] of repeating units derived from (meth) acrylonitrile, of the structural unit represented by the formula (1) The copolymerization ratio [M1] is Ma: Mb: M1 = 20 to 95: 1 to 40: 1 to 40 (the whole is 100: based on mass) (2) to (6) Composition for secondary battery electrode.
(8) The composition for secondary battery electrodes according to any one of (1) to (7), wherein the resin is in the form of particles having an average particle diameter of 10 to 500 nm.
(9) The composition for secondary battery electrodes according to any one of (1) to (8), wherein the active material is lithium titanate.
(10) For the secondary battery electrode according to any one of (1) to (9), wherein the resin is contained in an amount of 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the active material. Composition.
(11) An electrode mixture in which a film of the composition for a secondary battery electrode according to any one of (1) to (10) is formed on at least one surface of a current collector.
(12) A secondary battery comprising the electrode mixture according to (11) as a positive electrode and / or a negative electrode.

  According to the composition for a secondary battery electrode and the secondary battery of the present invention, the storage stability of the slurry, the binding property, and the electrode flexibility can be achieved at the same time, and the battery cycle characteristics can be improved. In addition, the composition for a secondary battery electrode and the secondary battery of the present invention have particularly good compatibility with a negative electrode active material made of LTO (lithium titanate), and can effectively exhibit its high performance.

It is sectional drawing which shows typically the structure of the lithium secondary battery which concerns on preferable embodiment of this invention. FIG. 2 is an exploded perspective view showing a specific configuration of a lithium secondary battery according to a preferred embodiment of the present invention.

  The composition for secondary battery electrodes of the present invention exhibits the above excellent effect as an electrode mixture containing an active material by employing a binder having a specific phosphorus-containing group. The reason for this includes unexplained points, but especially in the highly basic lithium titanate, in the case of acrylic acid, etc. used in the past, the latex structure collapses due to hydrolysis, which reduces the stability over time of the electrode composition. It is thought that it was a factor to make it. In contrast, the resin structure employed in the present invention suppresses hydrolysis, and even if hydrolysis occurs, phosphoric acid, phosphonic acid ester, etc. can be recombined, and a good latex structure can be maintained. It is thought that it became. At the same time, it is considered that the deterioration of the binding property is effectively suppressed and the cycle characteristics are improved. Hereinafter, the present invention will be described in detail focusing on preferred embodiments thereof.

[Composition for secondary battery electrode]
The composition for secondary battery electrodes of the present invention contains an active material, a dispersion medium mainly containing water, and a specific resin. First, the characteristics of the resin will be described.
(Specific resin)
The specific resin has at least one functional group among the formulas (A1) to (A3).

・ R ^{11 to} R ¹⁶
R ¹¹ represents an alkyl group, an alkenyl group, an alkynyl group, or an aryl group. Preferable examples of the alkyl group, alkenyl group, alkynyl group and aryl group include examples of the substituent T described later.
R ^{12 to} R ¹⁶ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or atomic group that can form a salt with O ⁻ . Preferable examples of the alkyl group, alkenyl group, alkynyl group and aryl group include examples of the substituent T described later. The atoms or atomic groups capable of forming a salt with O ⁻ are, in formulas (A1) to (A3), R ^{12 to} R ¹⁶ as targets, and the oxygen atom to which they are bonded is O ^{− and} the cationic species to be bonded is Can be mentioned. For example, an alkali metal ion and an organic cation are mentioned. Examples of alkali metal ions include sodium ions, potassium ions, and lithium ions. Examples of the organic cation include alkylammonium consisting of an alkyl group having 1 to 5 carbon atoms, such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium. Particularly preferred examples include a hydrogen atom, sodium ion, potassium ion, and lithium ion.

  In this invention, it is preferable that the said resin contains the structural unit represented by following formula (1).

・ R
In the formula, R represents a hydrogen atom, a halogen atom, or an alkyl group. Preferable examples of the alkyl group include examples of the substituent T described later. Particularly preferred examples include a hydrogen atom, a methyl group, and a chlorine atom.

・ W
W represents a divalent linking group or a single bond. As the linking group, an alkylene group having 1 to 10 carbon atoms (more preferably 1 to 6 carbon atoms, more preferably 1 to 3), an alkenylene group having 2 to 6 carbon atoms (more preferably 2 or 3 carbon atoms), A carbonyl group, an ether group (—O—), a thioether group (—S—), an imino group (—NR—: R is an alkyl group having 1 to 3 carbon atoms), or a combination thereof is preferable. Among them, a single bond, a carbonyl group, an oxycarbonyl group, a carbonyloxy group, a carbonate group, an amide group, a urethane group, an alkylene group having 1 to 10 carbon atoms, a carbonyl (oligo) oxyalkylene group having 2 to 20 carbon atoms (- CO- (O-Lr) x-: x is an integer of 1 or more, Lr is an alkylene group, and so on), an (oligo) alkyleneoxy group having 1 to 20 carbon atoms (-(Lr-O-) x-), C2-C20 carbonyloxy (oligo) alkyleneoxy group (-COO- (Lr-O-) x-), C2-C20 carbonylaminoalkylene group, C2-C20 carbonylaminoalkyleneoxy group Is mentioned. Preferable examples include a carbonyl group, a carbonyl (oligo) oxyalkylene group having 2 to 20 carbon atoms, and a carbonyloxy (oligo) alkyleneoxy group having 2 to 20 carbon atoms. As a particularly preferred example, a carbonyl group, a carbonyl (oligo) oxyethylene group having a repeating number of 1 to 10 (preferably 1 to 6) (-CO- (O-Et) x-: Et is an ethylene group), and the repeating number is Examples thereof include 1 to 10 (preferably 1 to 6) carbonyl (oligo) oxypropylene groups (-CO- (O-Pr) x-: Pr is a propylene group).
The linking group W may further have a substituent, and examples of the substituent that may be included include the substituent T described below.

・ Z ¹¹
Z ¹¹ represents a functional group selected from the above formulas (A1) to (A3). Preferable ones are also as defined above.

  In the present invention, it is more preferable that the resin includes a structural unit represented by the following formula (2).

・ R
R is synonymous with the formula (1).

・ L
L represents a divalent linking group having a chain length of 2 atoms or more. Here, the chain length refers to the number of atoms (not including atoms adjacent to the shortest path) connecting O to Z ¹² (Z ^{13 in the} following formula (3)) at the shortest. Taking the repeating unit derived from A-9 as an example, the chain length of L is 2, and no hydrogen atom is contained. The upper limit of the chain length is not particularly limited, but is preferably 30 atoms or less, and more preferably 20 atoms or less. By setting it as this lower limit or more, it is preferable at the point which can interact effectively with the active material surface and can hold | maintain binding property. On the other hand, it is preferable to make it not more than the above upper limit value in that the density of the active material can be kept high. Specific examples of L include an alkylene group having 2 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, an arylene group having 6 to 20 carbon atoms, and an (oligo) alkyleneoxy group having 1 to 20 carbon atoms (-(Lr -O-) x-). Preferable examples include an alkylene group having 2 to 10 carbon atoms and an (oligo) alkyleneoxy group (— (Lr—O—) x—) having 2 to 18 carbon atoms. Particularly preferred examples include an ethylene group, a propylene group, an (oligo) ethyleneoxy group (-(Et-O-) x-) having 1 to 10 (preferably 1 to 6) repeats, and a number of 1 to 6 repeats. (Oligo) propyleneoxy group (-(Pr-O-) x-) is mentioned.
The linking group L may further have a substituent, and examples of the substituent that may be included include the substituent T described below.

・ Z ¹²
Z ¹² is preferably synonymous with Z ^11, and more preferably —PO (OR ²¹ ) ₂ or —OPO (OR ²¹ ) ₂ . R ²¹ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or group of atoms that can form a salt with O ⁻ . Preferred of R ²¹ has ^the same meaning as ^{R 16.}

  More preferably, the resin contains a structural unit represented by the following formula (3).

・ R
In formula, R is synonymous with the said General formula (1).

· ^{L 11, L 12}
L ¹¹ and L ¹² each independently represent a divalent linking group having a chain length of 2 atoms or more, and the preferred chain length is the same as L. Specific examples thereof include the same linking groups as those described above for L.

・ Z ¹³
Z ¹³ represents —PO (OR ²² ) — or —OPO (OR ²³ ) —. R ^{22 and} R ²³ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or a group of atoms that can form a salt with O ⁻ . Preferable R ²² is the same as R ¹² described above. Preferred of R ²³ is the same as the ^{R 16.}

When the specific resin is a copolymer, the copolymerization ratio [M1] of the structural unit represented by the formula (1) is not particularly limited, but is 1 to 50 when the whole is 100 (mass basis). It is preferable that it is 5-20.
When the specific resin of the present invention is a copolymer, it is derived from a structural unit represented by the formula (1) (preferably a structural unit represented by the formula (2) or the formula (3)) and a methacrylic acid ester monomer. Of repeating units (excluding the structural unit represented by the formula (1)), and more preferably including repeating units derived from (meth) acrylonitrile.
Copolymerization ratio [Ma] of repeating units derived from (meth) acrylic acid ester monomers, Copolymerization ratio [Mb] of repeating units derived from (meth) acrylonitrile, Copolymerization ratio of structural units represented by formula (1) [ M1] is preferably Ma: Mb: M1 = 20 to 95: 1 to 40: 1 to 40, more preferably 40 to 90: 5 to 20: 1 to 30, and most preferably 50 to 85: 5. -15: 1 to 20 (100: mass basis as a whole).

In addition, in this specification, it uses for the meaning containing the salt and its ion besides the said compound itself about the display of a compound. Moreover, it is the meaning including the derivative | guide_body which changed the predetermined part in the range with the desired effect.
In the present specification, a substituent that does not specify substitution / non-substitution (the same applies to a linking group) means that the group may have an arbitrary substituent. This is also synonymous for compounds that do not specify substitution / non-substitution. Preferred substituents include the following substituent T.

Examples of the substituent T include the following.
An alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, such as methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), alkenyl A group (preferably an alkenyl group having 2 to 20 carbon atoms, such as vinyl, allyl, oleyl, etc.), an alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, such as ethynyl, butadiynyl, phenylethynyl, etc.), A cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), an aryl group (preferably an aryl group having 6 to 26 carbon atoms, for example, Phenyl, 1-naphthyl, 4-methoxyphenyl, -Chlorophenyl, 3-methylphenyl and the like), a heterocyclic group (preferably a heterocyclic group having 2 to 20 carbon atoms, preferably a 5- or 6-membered ring carbon having at least one oxygen atom, sulfur atom or nitrogen atom) A heterocyclic group having 2 to 20 atoms is preferable, and examples thereof include 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzoimidazolyl, 2-thiazolyl, 2-oxazolyl, and the like, and an alkoxy group (preferably having 1 to 1 carbon atoms). 20 alkoxy groups such as methoxy, ethoxy, isopropyloxy, benzyloxy, etc.), aryloxy groups (preferably aryloxy groups having 6 to 26 carbon atoms, such as phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy and the like), an alkoxycarbonyl group (preferably having 2 to 2 carbon atoms) 0 alkoxycarbonyl groups such as ethoxycarbonyl, 2-ethylhexyloxycarbonyl, etc., amino groups (preferably containing an amino group having 0 to 20 carbon atoms, an alkylamino group, an arylamino group, such as amino, N, N-dimethylamino, N, N-diethylamino, N-ethylamino, anilino, etc.), sulfamoyl groups (preferably sulfonamido groups having 0 to 20 carbon atoms, such as N, N-dimethylsulfamoyl, N-phenyl) Sulfamoyl etc.), an acyloxy group (preferably an acyloxy group having 1 to 20 carbon atoms such as acetyloxy, benzoyloxy etc.), a carbamoyl group (preferably a carbamoyl group having 1 to 20 carbon atoms such as N, N-dimethylcarbamoyl, N-phenylcarbamoyl, etc.), acyl An amino group (preferably an acylamino group having 1 to 20 carbon atoms, such as acetylamino, benzoylamino, etc.), a sulfonamide group (preferably a sulfamoyl group having 0 to 20 carbon atoms, such as methanesulfonamide, benzenesulfonamide , N-methylmethanesulfonamide, N-ethylbenzenesulfonamide, etc.), hydroxy group, cyano group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), the above formulas (A1) to (A3) More preferably an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an amino group, an acylamino group, a cyano group or a halogen atom. Particularly preferably an alkyl group, an alkenyl group, a hetero Group, an alkoxy group, an alkoxycarbonyl group, an amino group, an acylamino group, a group represented by any one of the formulas (A1) ~ (A3), or a cyano group.

  When a compound or a substituent includes an alkyl group, an alkenyl group, etc., these may be linear or branched, and may be substituted or unsubstituted. When an aryl group, a heterocyclic group, or the like is included, they may be monocyclic or condensed, and may be substituted or unsubstituted.

  Although the preferable example of the monomer which comprises the said specific resin is given below, this invention is limited to this and is not interpreted.

Ａ−７、Ａ−８は混合物であることを意味する。混合比は任意であるが、上記の例示ではモル比で等量の混合物とする。

A-7 and A-8 mean a mixture. The mixing ratio is arbitrary, but in the above example, the mixture is equivalent in molar ratio.

  In the electrode composition of the present invention, the content of the specific resin is not particularly limited, but is preferably 0.1 parts by mass or more, and 0.5 parts by mass or more with respect to 100 parts by mass of the active material. It is more preferable. Although there is no upper limit in particular, it is preferable that it is 10 mass parts or less with respect to 100 mass parts of active material, and it is more preferable that it is 5 mass parts or less. By setting it to the above lower limit value or more, good binding properties can be maintained, which is preferable. By setting it to the upper limit or less, it is preferable because it has good charge / discharge cycle characteristics, a high capacity, and cycle stability can be maintained.

(Particle size)
The specific resin is preferably in the form of particles having an average particle size of 10 nm or more, and more preferably 30 nm or more. Although there is no particular upper limit, the average particle size is preferably 500 nm or less, and more preferably 200 nm or less. Although the measuring method of an average particle diameter is not limited, Unless it refuses, it is set as the volume average particle diameter measured by the method employ | adopted by the postscript Example. By setting it to the above lower limit value or more, storage stability can be maintained, which is preferable. By making it into the said upper limit or less, the adhesiveness to an electrode can be improved and it is preferable.

(Dispersion medium)
Although the dispersion medium applied to this invention is not specifically limited, In this invention, it is required that water is a main component. Thus, by using a medium containing water as a main component, it is preferable that the cost of solvent recovery required when an organic solvent is used can be reduced, and further, the environmental load can be reduced. The dispersion medium may contain a water-soluble component such as alcohol, alkali metal salt, or alkaline earth metal salt as long as the effects of the present invention are not impaired. Preferably, it is more preferable to use a medium consisting only of water, excluding inevitable impurities. Note that the main component in the medium means to occupy a majority in the volume of the medium.

(Active material)
Although the active material of this invention is not specifically limited, What is normally used for this kind of battery can be applied suitably. The active material is preferably a material capable of inserting and releasing metal ions belonging to Group 1 or Group 2 of the Periodic Table. Either a positive electrode active material or a negative electrode active material may be used, and among these, a negative electrode composition combined with a negative electrode active material is preferable. The form of ion exchange is not particularly limited, but may be an occlusion / release type or a precipitation dissolution type. Specific materials of the active material will be described in detail later.
Although it does not specifically limit as a density | concentration of the active material in a composition, From a viewpoint of improving the battery capacity per unit volume, 30-99.5 mass% is preferable and 70-99 mass% is more preferable.

  In the present invention, the composition means that two or more components exist substantially uniformly in a specific composition. Here, “substantially uniform” means that each component may be unevenly distributed within the range where the effects of the invention are exerted. The composition is not particularly limited as long as the above definition is satisfied, is not limited to a fluid liquid or a paste, and includes a solid or powder composed of a plurality of components. Furthermore, even when there is a sediment, it means that the composition maintains a dispersion state for a predetermined time by stirring.

(kit)
The electrode composition of the present invention may be a kit composed of a plurality of liquids or powders. For example, the first agent includes an active material, the second agent includes the specific resin, the first agent or the second agent contains a dispersion medium, or the third agent is a dispersion medium. Is mentioned. You may set the quantity of each component so that it may become the range prescribed | regulated above.

[Electrolyte]
(Organic solvent)
Examples of the organic solvent used in the electrolyte include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane. , Tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, propion Ethyl acid, methyl butyrate, methyl isobutyrate, methyl trimethyl acetate, ethyl trimethyl acetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N, N-dimethylformamide, N-methylpi Examples include loridinone, N-methyloxazolidinone, N, N′-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethyl sulfoxide, and dimethyl sulfoxide phosphoric acid. These may be used alone or in combination of two or more. Among them, at least one member selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate is preferable. Particularly, a high viscosity (high dielectric constant) solvent such as ethylene carbonate or propylene carbonate (for example, ratio A combination of a dielectric constant ε ≧ 30) and a low viscosity solvent such as dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate (for example, viscosity ≦ 1 mPa · s) is more preferable. This is because the dissociation property of the electrolyte salt and the ion mobility are improved.
However, the organic solvent (nonaqueous solvent) used in the present invention is not limited to the above examples.

  Moreover, the solvent may contain the cyclic carbonate which has an unsaturated bond. This is because the chemical stability of the electrolytic solution is further improved. Examples of the cyclic carbonate having an unsaturated bond include at least one selected from the group consisting of vinylene carbonate compounds, vinyl ethylene carbonate compounds and methylene ethylene carbonate compounds.

  Examples of the vinylene carbonate compound include vinylene carbonate (1,3-dioxol-2-one), methyl vinylene carbonate (4-methyl-1,3-dioxol-2-one), and ethyl vinylene carbonate (4-ethyl- 1,3-dioxol-2-one), 4,5-dimethyl-1,3-dioxol-2-one, 4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1,3 -Dioxol-2-one or 4-trifluoromethyl-1,3-dioxol-2-one and the like.

  Examples of the vinyl carbonate-based compound include vinyl ethylene carbonate (4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, and 4-ethyl. -4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolane-2 -One, 4,4-divinyl-1,3-dioxolan-2-one, 4,5-divinyl-1,3-dioxolan-2-one and the like.

  Examples of the methylene ethylene carbonate compound include 4-methylene-1,3-dioxolan-2-one, 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, and 4,4-diethyl-5-one. And methylene-1,3-dioxolan-2-one.

  These may be used alone or in combination of two or more. Among these, vinylene carbonate is preferable. This is because a high effect can be obtained.

(Group 1 or Group 2 ions, etc.)
The metal ions or salts thereof belonging to Group 1 or Group 2 of the periodic table contained in the electrolytic solution are appropriately selected depending on the intended use of the electrolytic solution. For example, lithium salt, potassium salt, sodium salt, calcium salt, magnesium salt and the like can be mentioned. When used in a secondary battery or the like, lithium salt is preferable from the viewpoint of output. When the electrolytic solution is used as an electrolyte of a non-aqueous electrolytic solution for a lithium secondary battery, a lithium salt may be selected as a metal ion salt. The lithium salt is not particularly limited as long as it is a lithium salt usually used for an electrolyte of a non-aqueous electrolyte solution for a lithium secondary battery. For example, those described below are preferable.

(L-1) Inorganic lithium salts: inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ ; perhalogenates such as LiClO ₄ , LiBrO ₄ , LiIO ₄ ; inorganic chloride salts such as LiAlCl ₄ etc.

(L-2) Fluorine-containing organic lithium salt: Perfluoroalkane sulfonate such as LiCF ₃ SO ₃ ; LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (FSO ₂ ) ₂ , Perfluoroalkanesulfonylimide salts such as LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ); perfluoroalkanesulfonylmethide salts such as LiC (CF ₃ SO ₂ ) ₃ ; Li [PF ₅ (CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li [PF ₅ (CF ₂ CF ₂ CF ₂ CF _{3 )], Li [PF 4 (} CF 2 CF 2 CF 2 CF 3) 2], Li [PF 3 (CF 2 CF 2 CF 2 CF 3) 3] fluoroalkyl fluoride such as potash Acid salts, and the like.

  (L-3) Oxalatoborate salt: lithium bis (oxalato) borate, lithium difluorooxalatoborate and the like.

Among these, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiClO ₄ , Li (Rf ¹ SO ₃ ), LiN (Rf ¹ SO ₂ ) ₂ , LiN (FSO ₂ ) ₂ , and LiN (Rf ¹ SO ₂ ) (Rf ² SO ₂ ) ₂ Lithium bis (oxalato) borate salts are preferred, LiPF ₆ , LiBF ₄ , LiN (Rf ¹ SO ₂ ) ₂ , LiN (FSO ₂ ) ₂ , and LiN (Rf ¹ SO ₂ ) ( More preferred are lithium imide salts such as Rf ² SO ₂ ) ₂ and lithium bis (oxalato) borate salts. Here, Rf ¹ and Rf ² each represent a perfluoroalkyl group.
In addition, the lithium salt used for electrolyte solution may be used individually by 1 type, or may combine 2 or more types arbitrarily.
The content of the metal ions belonging to Group 1 or Group 2 of the periodic table or the metal salt thereof in the electrolytic solution is added in an amount so as to obtain a preferable salt concentration described below in the method for preparing the electrolytic solution. The salt concentration is appropriately selected depending on the intended use of the electrolytic solution, but is generally 10% to 50% by mass, more preferably 15% to 30% by mass, based on the total mass of the electrolytic solution. In addition, when evaluating as an ion density | concentration, what is necessary is just to calculate by salt conversion with the metal applied suitably.

[Secondary battery]
A preferred embodiment of the secondary battery of the present invention will be described with reference to FIG. The lithium secondary battery 10 of this embodiment includes the above-described electrolyte solution 5 for a non-aqueous secondary battery, a positive electrode C capable of inserting and releasing lithium ions (positive electrode current collector 1, positive electrode active material layer 2), lithium A negative electrode A (negative electrode current collector 3, negative electrode active material layer 4) capable of insertion and release of ions or dissolution precipitation. In addition to these essential members, considering the purpose of use of the battery, the shape of the potential, etc., a separator 9 disposed between the positive electrode and the negative electrode, a current collecting terminal (not shown), an outer case, etc. (Not shown). If necessary, a protective element may be attached to at least one of the inside of the battery and the outside of the battery. By adopting such a structure, lithium ion exchanges a and b are generated in the electrolytic solution 5, and charging / discharging α / β can be performed. Electric power can be stored. Hereinafter, the configuration of the lithium secondary battery which is a preferred embodiment of the present invention will be described in more detail.

(Battery shape)
The battery shape to which the lithium secondary battery of the present embodiment is applied is not particularly limited, and examples thereof include a bottomed cylindrical shape, a bottomed square shape, a thin shape, a sheet shape, and a paper shape. Any of these may be used. Further, it may be of a different shape such as a horseshoe shape or a comb shape considering the shape of the system or device to be incorporated. Among them, from the viewpoint of efficiently releasing the heat inside the battery to the outside, a square shape such as a bottomed square shape or a thin shape having at least one surface that is relatively flat and has a large area is preferable.

  In a battery having a bottomed cylindrical shape, since the outer surface area with respect to the power generating element to be filled becomes small, it is preferable to design so that Joule heat generated by the internal resistance at the time of charging and discharging efficiently escapes to the outside. Moreover, it is preferable to design so that the filling ratio of the substance having high thermal conductivity is increased and the temperature distribution inside is reduced. FIG. 2 is an example of a bottomed cylindrical lithium secondary battery 100. This battery is a bottomed cylindrical lithium secondary battery 100 in which a positive electrode sheet 14 and a negative electrode sheet 16 overlapped with a separator 12 are wound and accommodated in an outer can 18.

(Members constituting the battery)
The lithium secondary battery according to this embodiment includes an electrolytic solution 5, positive and negative electrode composites C and A, and a separator basic member 9. Hereinafter, each of these members will be described.
(Electrolyte)
The above-mentioned thing can be utilized for the electrolyte solution used for the lithium secondary battery of this embodiment. In order to improve the performance of the battery, various additives can be used in the electrolytic solution depending on the purpose as long as the effects of the present invention are not impaired. As such an additive, such a functional additive such as an overcharge inhibitor, a negative electrode film forming agent, and a positive electrode protective agent may be used.

  Moreover, the combined use of a negative electrode film forming agent and a positive electrode protective agent, or the combined use of an overcharge inhibitor, a negative electrode film forming agent, and a positive electrode protective agent is particularly preferable.

  The content ratio of these functional additives in the non-aqueous electrolyte solution is not particularly limited, but is preferably 0.01% by mass or more, particularly preferably 0.1% by mass or more, respectively, with respect to the entire non-aqueous electrolyte solution. More preferably, it is 0.2% by mass or more, and the upper limit is preferably 5% by mass or less, particularly preferably 3% by mass or less, and further preferably 2% by mass or less. By adding these compounds, it is possible to suppress rupture / ignition of the battery at the time of abnormality due to overcharge, and to improve the capacity maintenance characteristic and cycle characteristic after high-temperature storage.

(Electrode mixture)
The electrode mixture is obtained by applying a dispersion of an active material and a conductive agent, a binder, a filler, etc. on a current collector (electrode substrate). In a lithium battery, the active material is a positive electrode active material. It is preferable to use a negative electrode mixture in which the positive electrode mixture and the active material are a negative electrode active material. Next, each component in the dispersion (electrode composition) constituting the electrode mixture will be described.

-Positive electrode active material You may use a particulate-form positive electrode active material for the electrode compound material for secondary batteries. As the positive electrode active material, a transition metal oxide capable of reversibly inserting and releasing lithium ions can be used, but a lithium-containing transition metal oxide is preferably used. Preferred examples of the lithium-containing transition metal oxide preferably used as the positive electrode active material include oxides containing lithium-containing Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, and W. Alkali metals other than lithium (elements of Group 1 (Ia) and Group 2 (IIa) of the periodic table) and / or Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P , B, etc. may be mixed. The mixing amount is preferably 0 to 30 mol% with respect to the transition metal.

  Among the lithium-containing transition metal oxides preferably used as the positive electrode active material, a lithium compound / transition metal compound (wherein the transition metal is selected from Ti, V, Cr, Mn, Fe, Co, Ni, Mo, W) It is more preferable that the mixture is synthesized so that the total molar ratio of the compound is 0.3 to 2.2.

Further, among the lithium compounds / transition metal compounds, Li _g M3O ₂ (M3 represents one or more elements selected from Co, Ni, Fe, and Mn. G represents 0 to 1.2. ) Or a material having a spinel structure represented by Li _h M4 ₂ O ₄ (M4 represents Mn. H represents 0 to 2). As M3 and M4, Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, and B may be mixed in addition to the transition metal. The mixing amount is preferably 0 to 30 mol% with respect to the transition metal.

The _Li g M3O material containing _2, among the materials having the spinel structure represented by _{Li h M4 2 O 4, Li} g CoO 2, Li g NiO 2, Li g MnO 2, Li g Co j Ni 1-j _{O 2, Li h Mn 2 O} 4, LiNi j Mn 1-j O 2, LiCo j Ni h Al 1-j-h O 2, LiCo j Ni h Mn 1-j-h O 2, LiMn h Al 2- _{h O 4, LiMn h Ni 2} -h O 4 ( where g .j representing a 0.02 to 1.2 represents a .h 0-2 representing the 0.1 to 0.9.) is particularly preferably, more preferably _{Li g CoO 2, Li h Mn} 2 O 4, LiCo j Ni h Al 1-j-h O 2, LiCo j Ni h Mn 1-j-h O 2, LiMn h Al 2-h O _4, LiMn _h Ni _2- O is _4. Of these, an electrode containing Ni is more preferable from the viewpoint of high capacity and high output. Here, the g value and the h value are values before the start of charge / discharge, and are values that increase / decrease due to charge / discharge. In particular,
LiCoO ₂ LiNi _0.85 Co _0.01 Al _0.05 O ₂ ,
LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiMn _1.8 Al _0.2 O ₄ ,
LiMn _1.5 Ni _0.5 O ₄ and the like.

As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ). ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other metals.

In the nonaqueous electrolyte secondary battery, the average particle size of the positive electrode active material used is not particularly limited, but is preferably 0.1 μm to 50 μm. No particular limitation is imposed on the specific surface area, preferably from 0.01m ² / g~50m ² / g by the BET method. Further, the pH of the supernatant when 5 g of the positive electrode active material is dissolved in 100 ml of distilled water is preferably 7 or more and 12 or less.

  In order to make the positive electrode active substance have a predetermined particle size, a well-known pulverizer or classifier is used. For example, a mortar, a ball mill, a vibration ball mill, a vibration mill, a satellite ball mill, a planetary ball mill, a swirling air flow type jet mill, a sieve, or the like is used. The positive electrode active material obtained by the firing method may be used after being washed with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.

・ Negative electrode active material The negative electrode active material used for the electrode mixture for the secondary battery is not particularly limited as long as it can reversibly insert and release lithium ions. Carbonaceous materials, tin oxide, silicon oxide, etc. Metal oxides, metal composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, and metals that can form alloys with lithium such as Sn and Si. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Of these, carbonaceous materials or lithium composite oxides are preferably used from the viewpoint of safety.

In the present invention, it is preferable to use lithium titanate, more specifically lithium-titanium oxide (LTO: Li [Li _1/3 Ti _5/3 ] O ₄ ) as the active material of the negative electrode. By using this as a negative electrode active material, the effect by the electrode composition of this invention mentioned above can increase, and the further superior manufacturing aptitude and the advantage on product performance can be exhibited.

  In the nonaqueous electrolyte secondary battery, the average particle size of the negative electrode active material used is preferably 0.1 μm to 60 μm. To obtain a predetermined particle size, a well-known pulverizer or classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling air flow type jet mill or a sieve is preferably used. When pulverizing, wet pulverization in the presence of water or an organic solvent such as methanol can be performed as necessary. In order to obtain a desired particle size, classification is preferably performed. The classification method is not particularly limited, and a sieve, an air classifier, or the like can be used as necessary. Classification can be used both dry and wet.

  The chemical formula of the compound obtained by the firing method can be calculated from an inductively coupled plasma (ICP) emission spectroscopic analysis method as a measurement method and a mass difference between powders before and after firing as a simple method.

-Conductive agent As the conductive agent, any electronic conductive material that does not cause a chemical change in the configured secondary battery may be used, and any known conductive agent may be used. Usually, natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber and metal powder (copper, nickel, aluminum, silver (Japanese Patent Laid-Open No. Sho 63- 148, 554), etc.), conductive fibers such as metal fibers or polyphenylene derivatives (described in JP-A No. 59-20,971) can be included as one kind or a mixture thereof. Among these, the combined use of graphite and acetylene black is particularly preferable. As addition amount of the said electrically conductive agent, 0.1-50 mass% is preferable, and 0.5-30 mass% is more preferable. In the case of carbon or graphite, 0.5 to 15% by mass is particularly preferable in the dispersion.

-Binder In the present invention, the specific resin is used as the binder. The details have already been mentioned.
Examples of the binder that may be combined within the range that does not impair the effects of the present invention include polysaccharides, thermoplastic resins, and polymers having rubber elasticity. Among them, for example, starch, carboxymethylcellulose, cellulose, diacetylcellulose, and the like. , Methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, sodium alginate, polyacrylic acid, sodium polyacrylate, polyvinylphenol, polyvinylmethylether, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylonitrile, polyacrylamide, polyhydroxy (meth) acrylate, styrene Water-soluble polymer such as maleic acid copolymer, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene Hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, 2 -(Meth) acrylic acid ester copolymer containing (meth) acrylic acid ester such as ethylhexyl acrylate, (meth) acrylic acid ester-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate , Styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluororubber, polyethylene oxide, polyester polyurethane resin, polyester An emulsion (latex) or suspension of terpolyurethane resin, polycarbonate polyurethane resin, polyester resin, phenol resin, epoxy resin or the like is preferable, and polyacrylate ester latex, carboxymethylcellulose, polytetrafluoroethylene, and polyvinylidene fluoride are more preferable. .

-Filler The electrode mixture may contain a filler. As the material for forming the filler, any fibrous material that does not cause a chemical change in the secondary battery can be used. Usually, fibrous fillers made of materials such as olefin polymers such as polypropylene and polyethylene, glass, and carbon are used. Although the addition amount of a filler is not specifically limited, 0-30 mass% is preferable in a dispersion.

-Current collector As the positive / negative electrode current collector, an electron conductor that does not cause a chemical change in a non-aqueous electrolyte secondary battery is used. As the current collector of the positive electrode, in addition to aluminum, stainless steel, nickel, titanium, etc., the surface of aluminum or stainless steel is preferably treated with carbon, nickel, titanium, or silver. Among them, aluminum and aluminum alloys are preferable. More preferred.

  As the negative electrode current collector, aluminum, copper, stainless steel, nickel, and titanium are preferable, and aluminum, copper, and a copper alloy are more preferable.

As the shape of the current collector, a film sheet shape is usually used, but a net, a punched material, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like can also be used. The thickness of the current collector is not particularly limited, but is preferably 1 μm to 500 μm. Moreover, it is also preferable that the current collector surface is roughened by surface treatment.
An electrode mixture of the lithium secondary battery is formed by a member appropriately selected from these materials.

(Separator)
The separator used in the secondary battery is not particularly limited as long as it is a material that mechanically insulates the positive electrode and the negative electrode, has ion permeability, and has oxidation / reduction resistance at the contact surface between the positive electrode and the negative electrode. Absent. As such a material, a porous polymer material, an inorganic material, an organic-inorganic hybrid material, glass fiber, or the like is used. These separators preferably have a shutdown function for ensuring safety, that is, a function of closing the gap at 80 ° C. or higher to increase resistance and interrupting current, and the closing temperature is 90 ° C. or higher and 180 ° C. or lower. Preferably there is. From the viewpoint of the strength of the separator, it is particularly preferable to use a separator reinforced with an inorganic material or glass fiber.

  The shape of the hole of the separator is usually circular or elliptical, and the size is 0.05 μm to 30 μm, preferably 0.1 μm to 20 μm. Furthermore, it may be a rod-like or irregular-shaped hole as in the case of making by a stretching method or a phase separation method. The ratio of these gaps, that is, the porosity, is 20% to 90%, preferably 35% to 80%.

  The polymer material may be a single material such as cellulose nonwoven fabric, polyethylene, or polypropylene, or may be a composite material of two or more types. What laminated | stacked the 2 or more types of microporous film which changed the hole diameter, the porosity, the obstruction | occlusion temperature of a hole, etc. is preferable.

  Examples of the inorganic material include oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate, and those having a particle shape or fiber shape are used. . As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 μm to 1 μm and a thickness of 5 μm to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, alumina particles having a 90% particle diameter of less than 1 μm are formed on both surfaces of the positive electrode as a porous layer using a fluororesin binder.

[Applications of secondary batteries]
Lithium secondary batteries can be used for various applications because secondary batteries with good cycleability can be manufactured.
Although there is no particular limitation on the application mode, for example, when installed in an electronic device, a notebook computer, a pen input personal computer, a mobile personal computer, an electronic book player, a mobile phone, a cordless phone, a pager, a handy terminal, a mobile fax machine, a mobile phone Copy, portable printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, minidisc, electric shaver, transceiver, electronic notebook, calculator, memory card, portable tape recorder, radio, backup power supply, memory card, etc. It is done. Other consumer products include automobiles, electric vehicles, motors, lighting equipment, toys, game equipment, road conditioners, watches, strobes, cameras, medical equipment (such as pacemakers, hearing aids, and shoulder grinders). Furthermore, it can be used for various military use and space use. Moreover, it can also combine with a solar cell.

  Although the metal ion used for charge transport in the secondary battery is not particularly limited, it is preferable to use a metal ion belonging to Group 1 or Group 2 of the periodic table. Among these, it is preferable to use lithium ions, sodium ions, magnesium ions, calcium ions, aluminum ions, and the like. There are many documents and books such as the patent documents listed at the beginning for general technical matters regarding secondary batteries using lithium ions, which are helpful. In addition, for secondary batteries using sodium ions, Journal of Electrochemical Society; Electrochemical Science and Technology, USA, 1980, Vol. 127, pages 2097-2099, and the like can be referred to. For magnesium ions, see Nature 407, p. 724-727 (2000) and the like can be referred to. For calcium ions, see J.H. Electrochem. Soc. , Vol. 138, 3536 (1991) and the like. In the present invention, it is preferable to apply to a lithium secondary battery because of its widespread use, but the other effects also have a desired effect and should not be construed as being limited thereto.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In addition, it is shown that it is a mass reference | standard when it only describes as% or part per content rate or a mixing | blending.

2-ethylhexyl acrylate AN; acrylonitrile St; styrene MMA; methyl methacrylate BA; n-butyl acrylate AA; acrylic acid DVB; divinylbenzene VDF; vinylidene fluoride HEA; 2-hydroxyethyl acrylate EA: ethyl acrylate

<Production and evaluation of evaluation sample>
(1) Resin synthesis example To a 1 L three-necked flask equipped with a reflux condenser and a gas introduction cock, 300.0 g of distilled water and 1.0 g of potassium persulfate were added, and nitrogen gas was introduced at a flow rate of 200 mL / min for 10 minutes. After that, the temperature was raised to 75. Liquids prepared in separate containers (2-ethylhexyl acrylate (Wako Pure Chemical Industries, Ltd.) 166.2 g, acrylonitrile (Tokyo Chemical Industry Co., Ltd.) 23.8 g, acid phosphooxyethyl methacrylate (Unichemical Corporation, Applicable to Exemplified Compound A-2) 10.0 g, distilled water 120.0 g, Adeka Soap SR-1025 (manufactured by Adeka Co., Ltd.) 16.0 g mixed to make an emulsified state) over 2.5 hours It was dripped. After completion of dropping, the temperature was raised to 85 ° C. and stirring was continued for 2 hours. Thereafter, the mixture was cooled to room temperature, 10% aqueous sodium hydroxide solution was slowly added to adjust the pH to 7.0, and an aqueous dispersion of resin P-1 was obtained. The solid concentration was 28% and the particle size was 107 nm.
Other exemplary polymers can be prepared in a similar manner (see Table A above). However, Resin Q-4 was synthesized according to the procedure described in (10) below.

(2) Measurement of average particle diameter The volume average particle diameter of the resin was measured using a laser diffraction / scattering particle size distribution analyzer LA-920 (manufactured by HORIBA).

(3) Preparation of composition for secondary battery electrode 1.45 of carboxymethyl cellulose (trade name “CMC2200”, manufactured by Daicel Finechem) separately prepared in a planetary mixer (TK Hibismix, manufactured by PRIMIX) 1 part of a 1% aqueous solution (in terms of solid content), 1 part of acetylene black, 97 parts of lithium titanate (trade name “Enamite LT-106”, manufactured by Ishihara Sangyo Co., Ltd.), and 1 part of the above resin (in terms of solid content) were added. And stirring at 40 rpm for 1 hour. Note that the same method can be used when graphite is used as the active material.

(4) Evaluation of change with time in viscosity of secondary battery electrode composition Viscosity η ₀ immediately after preparation of the composition for secondary battery electrode prepared in (3) above and viscosity η ₁ after passage of room temperature for one day, The measurement was carried out at 25 ° C. using Rheo Stress 600 (manufactured by HAAKE), and the evaluation was made by classifying as follows according to the rate of change in viscosity after one day.
A: Change rate of 5% or less B: Change rate of over 5% and 10% or less C: Change rate of 10% or more G: Gelled and cannot measure viscosity

(5) Production of secondary battery electrode The composition for a secondary battery electrode obtained in the above (3) was applied onto an aluminum foil having a thickness of 20 μm with an applicator having an arbitrary clearance. Heated at 1 ° C. for 1 hour and dried. Then, using a press machine, it pressurized so that it might become arbitrary densities, and the secondary battery electrode was obtained.

(6) Evaluation of adhesion When the adhesive tape was applied to the electrode sheet and peeled off at a constant speed, it was expressed as the ratio of the area of the part that did not peel off.

(7) Evaluation of electrode flexibility The surface on the current collector side of the electrode sheet cut out to a size of 2 cm × 10 cm is wound around a SUS rod having a diameter of 2 mm, and whether or not peeling occurs when the SUS rod is moved in the longitudinal direction Observed and expressed as the number of windings where peeling occurred.

(8) Production of 2032 type coin battery The secondary battery electrode obtained by said (5) was cut out to disk shape with a diameter of 14.5 mm, and was used as a negative electrode. In addition, a coin battery was manufactured using a positive electrode made of lithium cobaltate as an active material, a polypropylene separator (thickness 25 μm), and an electrolyte solution of 1M LiPF ₆ in ethylene carbonate / diethyl carbonate (volume ratio 1: 1). .

(9) Evaluation of cycle performance When using the coin battery obtained by (8) above and using lithium titanate as an active material, the battery voltage is 2.75 V at 0.2 C in a thermostatic bath at 30 ° C. After charging at a constant current until the battery voltage became 0.2V, the operation of performing a constant current discharge was repeated until the battery voltage became 1 V at 0.2 C, and the number of cycles when the discharge capacity reached 90% of the second time was expressed.
On the other hand, when graphite is used as the active material, the battery voltage becomes 2.75 V at 0.2 C after constant current charging in a thermostat at 30 ° C. until the battery voltage becomes 4.2 V at 0.2 C. The operation of performing constant current discharge was repeated until the discharge capacity was 90% of the second discharge capacity.

(10) Synthetic Example of Comparative Resin Polyvinylidene fluoride Q-4a having a hydroxyl group was synthesized as follows in accordance with JP 2010-61930 A. To a 2 L autoclave, 1040.0 g of distilled water, 0.8 g of methylcellulose, 2.5 g of ethyl acetate, 4.0 g of diisopropyl peroxydicarbonate, 396.0 g of vinylidene fluoride, 4.0 g of 2-hydroxyethyl acrylate, Stirring was continued at 28 ° C. for 45 hours. Thereafter, the polymer was dehydrated, washed with distilled water, and dried at 80 ° C. for 20 hours to obtain a polymer Q-4a. Subsequently, 100.0 g of Q-4a and 400 mL of chloroform were added to a 1 L three-necked flask equipped with a reflux condenser, a gas introduction cock, and a stirrer, and 100.0 g of polyphosphoric acid was added while stirring under a nitrogen stream. Later, stirring was continued for 2 hours while heating under reflux. Then, it poured into ice water, the solid substance was collected by filtration, washed with distilled water, and dried at 80 ° C. for 20 hours to obtain Comparative Resin Q-4.

As is apparent from the results shown in Table 1, the composition for secondary battery electrodes using the resin of the present invention, the secondary battery electrode and the secondary battery have excellent storage stability because of little change in viscosity over time, and adhesion. It can be seen that the electrode is excellent in flexibility and electrode flexibility and has good cycle performance. On the other hand, it turns out that each performance is inferior in the element of a comparative example. In addition, it can be seen that the effect of the present invention is more suitably exhibited when lithium titanate is used as the active material, and, for example, the cycle characteristics are greatly improved (for example, test No. 101 and C01, No. .. Compare 121 and C04.)
Further, Q-4 having a vinylidene fluoride skeleton as a resin is extremely inferior in change in viscosity with time, such as a gelled product formed in the liquid preparation, poor in binding properties, and inferior in cycle performance. The reason for this includes unexplained points, but when water is used as the main dispersion medium, Li in lithium titanate dissolves and the system shakes alkaline, which accelerates dehydrofluorination of the vinylidene fluoride structure. The resulting double bond is considered to be a cause of gelation.

DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Positive electrode active material 3 Negative electrode collector 4 Negative electrode active material 5 Electrolyte 6 Operating means 7 Wiring 9 Separator 10 Lithium secondary battery 12 Separator 14 Positive electrode sheet 16 Negative electrode sheet 18 Exterior can 20 also serving as negative electrode 22 Sealing plate 24 Positive electrode current collector 26 Gasket 28 Pressure sensitive valve body 30 Current interruption element 100 Bottomed cylindrical lithium secondary battery

Claims (12)

A secondary battery electrode comprising an active material, a dispersion medium mainly composed of water, and a resin, wherein the resin has at least one functional group of formulas (A1) to (A3) in a side chain Composition.

[Wherein R ¹¹ represents an alkyl group, an alkenyl group, an alkynyl group, or an aryl group. R ^{12 to} R ¹⁶ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or atomic group that can form a salt with O ⁻ . ] The composition for secondary battery electrodes according to claim 1, wherein the resin contains a structural unit represented by the following formula (1).

[Wherein, R represents a hydrogen atom, a halogen atom, or an alkyl group. W represents a divalent linking group. Z ¹¹ represents a functional group selected from the above formulas (A1) to (A3). ] 3. The resin according to claim 1 or 2, wherein the resin comprises a structural unit represented by the following formula (2), a structural unit derived from a (meth) acrylic acid ester monomer, and a structural unit derived from a (meth) acrylonitrile monomer. Secondary battery electrode composition.

[Wherein, R represents a hydrogen atom, a halogen atom, or an alkyl group. L represents a divalent linking group having a chain length of 2 atoms or more. Z ¹² represents —PO (OR ²¹ ) ₂ or —OPO (OR ²¹ ) ₂ . R ²¹ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or group of atoms that can form a salt with O ⁻ . ] In Formula (2), R is a methyl group, L is an oligoethyleneoxy group having 1 to 6 repeats or an oligopropyleneoxy group having 1 to 6 repeats, and Z ¹² is —PO (OH The composition for secondary battery electrodes according to claim 3, which is ₂ . The composition for secondary battery electrodes as described in any one of Claims 1-4 in which the said resin contains the structural unit represented by following formula (3).

[Wherein, R has the same meaning as the formula (1). L ¹¹ and L ¹² each independently represents a divalent linking group having a chain length of 2 atoms or more. Z ¹³ represents —PO (OR ²² ) — or —OPO (OR ²³ ) —. R ²² and R ²³ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an atom or a group of atoms that can form a salt with O ⁻ . ]   The copolymerization ratio [M1] of the structural unit represented by the formula (1) in the resin is 1 to 50 when the whole is 100 (mass basis). The composition for secondary battery electrodes as described.   Copolymerization ratio [Ma] of repeating units derived from (meth) acrylic acid ester monomers, Copolymerization ratio [Mb] of repeating units derived from (meth) acrylonitrile, copolymerization ratio of structural units represented by formula (1) [M1] is Ma: Mb: M1 = 20 to 95: 1 to 40: 1 to 40 (the whole is 100: based on mass) 7. The secondary battery electrode according to any one of claims 2 to 6. Composition.   The composition for secondary battery electrodes according to any one of claims 1 to 7, wherein the resin is in the form of particles having an average particle size of 10 to 500 nm.   The composition for secondary battery electrodes according to any one of claims 1 to 8, wherein the active material is lithium titanate.   The composition for secondary battery electrodes as described in any one of Claims 1-9 which made the said resin contain 0.1 mass part or more and 10 mass parts or less with respect to 100 mass parts of active materials.   The electrode compound material by which the film | membrane of the composition for secondary battery electrodes as described in any one of Claims 1-10 was formed in the at least 1 surface of an electrical power collector.   A secondary battery comprising the electrode mixture according to claim 11 as a positive electrode and / or a negative electrode.

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