JP5760945B2 - Secondary battery electrode forming composition, secondary battery electrode, and secondary battery - Google Patents

Description

  The present invention relates to a composition for forming a secondary battery electrode, an electrode obtained using the composition, and a secondary battery obtained using the electrode.

  In recent years, small portable electronic devices such as digital cameras and mobile phones have been widely used. These electronic devices have always been required to minimize the volume and reduce the weight, and the batteries to be mounted are also required to be small, light, and have a large capacity. In addition, in a large-sized secondary battery for use in automobiles or the like, it is desired to realize a large-sized secondary battery instead of a conventional lead storage battery.

  In order to meet such demands, development of secondary batteries such as lithium ion secondary batteries and nickel metal hydride secondary batteries, for example, development of composite inks used for forming electrodes has been actively conducted. There is also an interest in a composition for forming an underlayer used for forming an underlayer of a composite material layer.

An important characteristic required for the composite ink used for forming the electrode and the composition for forming the underlayer includes uniformity in which the active material and the conductive assistant are appropriately dispersed.
This is because the dispersion state of the active material and the conductive auxiliary in the composition ink and the underlayer forming composition is the distribution state of the active material and the conductive auxiliary in the composite layer and the distribution state of the conductive auxiliary in the underlayer. This is because it affects the electrode physical properties and consequently the battery performance.
Therefore, dispersion of the active material and the conductive auxiliary agent is an important issue. In particular, carbon materials with excellent electrical conductivity (conducting aids) have a strong cohesive force due to their large structure and specific surface area, and should be uniformly mixed and dispersed, whether in the composite ink or in the composition for forming the underlayer. Is difficult.
And if the dispersibility and particle size control of the carbon material that is the conductive auxiliary agent is insufficient, the internal resistance of the electrode cannot be reduced because a uniform conductive network is not formed, and as a result, the performance of the electrode material is sufficient. The problem of being unable to withdraw.

  Moreover, when not only the conductive assistant but also the dispersion of the active material in the composite ink is insufficient, partial aggregation occurs in the composite layer formed from such a composite ink. In addition, resistance distribution occurs on the electrode due to partial aggregation, current concentration occurs when used as a battery, and problems such as partial heat generation and deterioration may occur.

  In addition, the composite ink and the composition for forming the underlayer are required to have appropriate fluidity to enable coating on the surface of the metal foil functioning as a current collector. Furthermore, in order to form a composite material layer or a base layer having a surface that is as flat as possible and having a uniform thickness, the composite ink or the base layer forming composition is required to have an appropriate viscosity.

  After the formation of the composite layer formed from the composite ink and the composition for forming the base layer, the metal foil as the base material is cut into pieces of a desired size and shape, or punched. It is pulled out. Therefore, the material layer and the base layer are required to have hardness that does not damage and softness that does not crack or peel off by cutting or punching.

  Furthermore, since the composite layer formed from the composite ink and the base layer formed from the composition for forming the base layer are exposed to the electrolyte in the battery, the composite layer and the base layer collapse, current collector There is a risk of causing peeling. Therefore, elution resistance in the electrolytic solution is also required for the composite material layer and the underlayer.

In Patent Documents 1 to 4, an active material and a conductive material are mixed, and this mixture is kneaded with a cellulose-based thickener aqueous solution, and then an aqueous binder such as tetrafluoropolyethylene and latex is further added and further kneaded. It is disclosed that a composite ink is obtained. However, these composite inks have a problem that the dispersed state is insufficient and the flexibility is poor, and a desired electrode cannot be produced, so that good battery performance cannot be obtained.
In order to solve these problems, a method of using a dispersant in addition to the conventional material has been developed when preparing a composite ink (see Patent Document 5). A good dispersion state of the ink is insufficient, and a desired electrode and a secondary battery are often not obtained. In particular, a composite ink in which the further dispersibility of the conductive assistant is uniform is desired.

  Further, Patent Document 6 discloses a binder composition for a secondary battery and an electrode using cross-linked resin fine particles. Even when these binder compositions are used, the active material and the conductive material are disclosed. When the dispersibility of the auxiliary agent is insufficient, the flexibility, adhesion to the current collector, and electrolytic solution elution resistance are insufficient, and desired electrodes and secondary batteries cannot be obtained.

Japanese Patent Laid-Open No. 2-15855 Japanese Patent Laid-Open No. 9-082364 JP 2003-142102 A JP 2010-165493 A JP-T-2006-51679 gazette WO2010 / 114119

  An object of the present invention is a composition for forming an electrode for forming a secondary battery having excellent charge / discharge cycle characteristics, and is excellent in dispersibility of an active material and a conductive auxiliary agent, and further to flexibility and a current collector. It is providing the composition for electrode formation excellent in the adhesiveness of this, and electrolysis solution elution resistance.

The present invention provides a binder composition comprising an amphoteric resin type dispersant (D) excellent in dispersibility of an electrode active material and a conductive additive, and resin fine particles excellent in adhesion to a current collector and elution resistance to electrolytic solution ( The above problem is solved by using C).
That is, the present invention comprises copolymerizing at least one of an electrode active material (A) or a carbon material (B) as a conductive additive, a binder composition (C) containing crosslinked resin fine particles, and the following monomer. A non-aqueous electrolyte secondary containing an amphoteric resin-type dispersant (D) obtained by neutralizing at least a part of carboxyl groups in the copolymer obtained with a basic compound and an aqueous liquid medium (E) The present invention relates to a composition for forming a battery electrode.
Ethylenically unsaturated monomer having an aromatic ring (d1): 5 to 70% by weight
Ethylenically unsaturated monomer having a carboxyl group (d2): 15 to 60% by weight
Ethylenically unsaturated monomer having an amino group (d3): 1 to 80% by weight
Ethylenically unsaturated monomers (d4) other than (d1) to (d3): 0 to 79% by weight
(However, the total of (d1) to (d4) is 100% by weight)

Further, the present invention, the non-aqueous electrolyte that cross-linked resin particles, characterized in that the following monomers the presence of a surfactant in water, a resin fine particles obtained by emulsion polymerization by radical polymerization initiators The present invention relates to a composition for forming a liquid secondary battery electrode.
(C1) an ethylenically unsaturated monomer having a monofunctional or polyfunctional alkoxysilyl group (c
1) and at least one monomer selected from the group consisting of monomers (c2) having two or more ethylenically unsaturated groups in one molecule: 0.1 to 5% by weight
(C2) Ethylenically unsaturated monomers (c3) other than the monomers (c1) to (c2): 95 to 99.9% by weight
(However, the total of the above (c1) to (c3) is 100% by weight)

Furthermore, this invention relates to the said composition for non-aqueous-electrolyte secondary battery electrode formation whose ethylenically unsaturated monomer (c3) is the following composition.
Ethylenically unsaturated monomer having a monofunctional or polyfunctional epoxy group (c4), monomeric ethylenically unsaturated monomer having a monofunctional or polyfunctional amide group (c5), and ethylene having a monofunctional or polyfunctional hydroxyl group At least one monomer selected from the group consisting of polymerizable unsaturated monomers (c6): 0.1 to 20% by weight
Ethylenically unsaturated monomers (c7) other than the monomers (c1), (c2), (c4) to (c6): 75 to 99.8% by weight
(However, the total of the above (c1) to (c3) is 100% by weight)

Furthermore, this invention relates to the said composition for non-aqueous-electrolyte secondary battery electrode formation characterized by the ethylenically unsaturated monomer (c7) being the following composition.
At least one monomer selected from the group consisting of an ethylenically unsaturated monomer (c8) having an alkyl group having 8 to 18 carbon atoms and an ethylenically unsaturated monomer (c9) having a cyclic structure: 30 ~ 95 wt%
Ethylenically unsaturated monomers other than the above (c1) to (c6), (c8) and (c9): 0 to 69.8% by weight
(However, the total of the above (c1) to (c3) is 100% by weight)

Further, in the present invention, the binder composition (C) containing crosslinked resin fine particles contains an uncrosslinked epoxy group-containing compound, an uncrosslinked amide group-containing compound, an uncrosslinked hydroxyl group-containing compound, and an uncrosslinked oxazoline group. The present invention relates to the composition for forming a non-aqueous electrolyte secondary battery electrode, comprising at least one uncrosslinked compound (F) selected from the group consisting of compounds.
Furthermore, the present invention includes a current collector and, the non-aqueous electrolyte secondary battery of the electrode mixture layer is formed from a composition for forming or electrode underlayer least comprises a further non-aqueous electrolyte secondary battery It relates to an electrode.
Furthermore, the present invention is a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution, wherein at least one of the positive electrode or the negative electrode is the electrode for a non- aqueous electrolyte secondary battery. The present invention relates to an electrolyte secondary battery.

  By using an amphoteric resin type dispersant, the dispersibility of the carbon material, which is an active material and a conductive auxiliary agent, is improved, and furthermore, by using a binder composition containing crosslinked resin fine particles, in addition to uniform dispersibility, Electrolytic solution elution was possible, and the electrode forming composition of the present invention could be obtained. The composition for electrode formation of the present invention can form a composite material layer and an undercoat layer that are excellent in flexibility and adhesion to a current collector, and can provide a secondary battery that is excellent in life such as charge / discharge cycle characteristics.

The secondary battery in this specification means a non-aqueous electrolyte secondary battery.
The electrode for a secondary battery can be obtained by various methods.
For example, on the surface of a current collector such as a metal foil,
(1) an ink-like composition containing an active material and a liquid medium (hereinafter referred to as composite ink),
(2) a mixed ink containing an active material, a conductive additive and a liquid medium;
(3) a mixed ink containing an active material, a binder and a liquid medium;
(4) A mixed ink containing an active material, a conductive additive, a binder, and a liquid medium,
It can be used to form a composite layer and obtain an electrode.

  Alternatively, an underlayer is formed on the surface of the current collector of the metal foil using a composition for forming an underlayer containing a conductive additive and a liquid medium, and the above composite ink (1 ) To (4) or other composite inks to form a composite layer and obtain an electrode.

In any case, it was described in detail in the section of the background art that the dispersion state of the active material and the conductive additive and the electrolytic solution elution resistance of the electrode mixture layer and the base layer influence the battery performance.
The amphoteric resin type dispersing agent (D) relaxes the aggregation of the active material and functions as a dispersing agent for the carbon material that is a conductive additive.
Therefore, the composition for forming a secondary battery electrode of the present invention can be utilized as a composite ink that requires an active material or a composition for forming an underlayer that does not require an active material.

First, the amphoteric resin type dispersant (D) in the present invention will be described.
The amphoteric resin type dispersant (D) in the present invention comprises an ethylenically unsaturated monomer (d1) having an aromatic ring, an ethylenically unsaturated monomer (d2) having a carboxyl group, and an ethylene having an amino group. Is obtained by neutralizing at least a part of the carboxyl group in the copolymer containing the basic unsaturated monomer (d3) as an essential component with a basic compound.

  The ethylenically unsaturated monomer constituting the amphoteric resin type dispersant (D) in the present invention means a monomer having one ethylenically unsaturated group in one molecule unless otherwise specified.

First, the ethylenically unsaturated monomer (d1) having an aromatic ring will be described.
Examples of the ethylenically unsaturated monomer (d1) having an aromatic ring used in the present invention include styrene, α-methylstyrene, and benzyl (meth) acrylate.

Next, the ethylenically unsaturated compound (d2) having a carboxyl group will be described.
The monomer (d2) used in the present invention is, as a carboxyl group-containing unsaturated compound, maleic acid, fumaric acid, itaconic acid, citraconic acid, or an alkyl or alkenyl monoester thereof, phthalic acid β- (meth) Acryloxyethyl monoester, isophthalic acid β- (meth) acryloxyethyl monoester, terephthalic acid β- (meth) acryloxyethyl monoester, succinic acid β- (meth) acryloxyethyl monoester, acrylic acid, methacrylic acid And crotonic acid, cinnamic acid, and the like. In particular, methacrylic acid and acrylic acid are preferable.

Next, the ethylenically unsaturated monomer (d3) having an amino group will be described.
The ethylenically unsaturated monomer (d3) having an amino group used in the present invention includes dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, methylethylaminoethyl (meth) acrylate, dimethylaminostyrene, diethylamino Examples include styrene.

Next, the monomer (d4) other than (d1) to (d3) will be described.
Examples of (meth) acrylate compounds include alkyl (meth) acrylates and alkylene glycol (meth) acrylates.

  More specifically, examples of the alkyl-based (meth) acrylate include alkyl (meth) acrylate having 1 to 22 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. ) When there is an acrylate and the purpose is to adjust the polarity, an alkyl group-containing acrylate having an alkyl group having 2 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, or a corresponding methacrylate is preferable.

Examples of the alkylene glycol (meth) acrylate include diethylene glycol mono (meth) acrylate and polyethylene glycol mono (meth) acrylate, which are monoacrylates having a hydroxyl group at the terminal and having a polyoxyalkylene chain, or corresponding monometas. Acrylate, etc.
Methoxyethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, etc., monoacrylate having an alkoxy group at the terminal and having a polyoxyalkylene chain or the corresponding monomethacrylate,
There are polyoxyalkylene-based acrylates having a phenoxy or aryloxy group at the terminal, such as phenoxyethylene glycol (meth) acrylate, or corresponding methacrylates.

  Examples of hydroxyl-containing unsaturated compounds other than the above include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate, 4-hydroxyvinylbenzene And so on.

Nitrogen-containing unsaturated compounds other than the above include monoalkylol (meth) acrylamides such as (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl- (meth) acrylamide,
Examples thereof include acrylamide-type unsaturated compounds such as N, N-di (methylol) acrylamide, N-methylol-N-methoxymethyl (meth) acrylamide, and dialalkylol (meth) acrylamide such as N, N-di (methoxymethyl) acrylamide. .

Furthermore, as other unsaturated compounds, perfluoromethylmethyl (meth) acrylate, perfluoroethylmethyl (meth) acrylate, 2-perfluorobutylethyl (meth) acrylate, 2-perfluorohexylethyl (meth) acrylate, etc. Perfluoroalkyl alkyl (meth) acrylates having a C 1-20 perfluoroalkyl group;
Perfluoroalkyl such as perfluorobutylethylene, perfluorohexylethylene, perfluorooctylethylene, perfluorodecylethylene, and perfluoroalkyl group-containing vinyl monomers such as alkylene, vinyltrichlorosilane, vinyltris (βmethoxyethoxy) silane, vinyl Examples thereof include silanol group-containing vinyl compounds such as triethoxysilane and γ- (meth) acryloxypropyltrimethoxysilane and derivatives thereof, and a plurality of them can be used from these groups.

  Examples of the fatty acid vinyl compound include vinyl acetate, vinyl butyrate, vinyl propionate, vinyl hexanoate, vinyl caprylate, vinyl laurate, vinyl palmitate, and vinyl stearate.

  Examples of the alkyl vinyl ether compound include butyl vinyl ether and ethyl vinyl ether.

  Examples of the α-olefin compound include 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene and the like.

Examples of vinyl compounds include allyl compounds such as allyl acetate, allyl alcohol, allylbenzene, and allyl cyanide, vinyl cyanide, vinylcyclohexane, vinyl methyl ketone, styrene, α-methylstyrene, 2-methylstyrene, and chlorostyrene. Can be mentioned.

  Examples of the ethynyl compound include acetylene, ethynylbenzene, ethynyltoluene, 1-ethynyl-1-cyclohexanol and the like. These can be used alone or in combination of two or more.

The ratio of the monomers constituting the copolymer in the amphoteric resin type dispersant (D) used in the present invention is such that the total of the monomers (d1) to (d4) is 100% by weight,
5 to 70% by weight of ethylenically unsaturated monomer (d1) having an aromatic ring,
15 to 60% by weight of ethylenically unsaturated monomer (d2) having a carboxyl group,
1 to 80% by weight of ethylenically unsaturated monomer (d3) having an amino group,
The other monomer (d4) other than (d1) to (d3) is 0 to 79% by weight.
Preferably, (d1): 20 to 70% by weight, (d2): 15 to 45% by weight, (d3): 1 to 70% by weight, (d4): 0 to 50% by weight.
More preferably, they are (d1): 30-70 weight%, (d2): 15-35 weight%, (d3): 1-40 weight%, (d4): 0-40 weight%.

  An active ring (A) or a carbon material, which will be described later, includes an aromatic ring derived from an ethylenically unsaturated monomer (d1) having an aromatic ring and an amino group derived from an ethylenically unsaturated monomer (d3) having an amino group. Presumed to be the main adsorption site to (B).

The ethylenically unsaturated monomer (d2) having a carboxyl group has a function of dissolving or dispersing a neutralized copolymer in an aqueous liquid medium.
Then, the active material (A) or the carbon material (B) is adsorbed via an aromatic ring or an amino group, neutralized, and the charge repulsion of the ionized carboxyl group, the active material (A) or the carbon material. It is considered that the dispersion state of (B) in the aqueous liquid medium can be kept stable.

The molecular weight of the copolymer obtained by copolymerizing the monomers (d1) to (d4) is not particularly limited, but the viscosity of the amphoteric resin dispersant (D) in a 20% solid content aqueous solution is preferably 5 to 100. 000 mPa · s, more preferably 10 to 50,000 mPa · s. When the viscosity of the amphoteric resin dispersant (D) is lower than the predetermined range and the molecular weight of the amphoteric resin dispersant (D) is higher than the predetermined range and the molecular weight of the amphoteric resin dispersant (D) is too high, the electrode active material There is a possibility of causing poor dispersion of (A) or the carbon material (B) which is a conductive additive.
In addition, the viscosity in this invention is the value measured on 25 degreeC conditions using the B-type viscosity meter.

The copolymer is obtained by copolymerizing a carboxyl group-containing unsaturated compound (d2), and it is preferable that the constituent ratio of the monomer having an anionic functional group in the copolymer is represented by the acid value as follows. That is, the acid value of the copolymer used is preferably in the range of 50 mgKOH / g to 400 mgKOH / g, and the acid value is preferably in the range of 80 mgKOH / g to 300 mgKOH / g.
When the acid value of the copolymer used in the present invention is lower than the above range, the dispersion stability of the dispersion tends to decrease and the viscosity tends to increase. Moreover, when the acid value of the copolymer used in the present invention is higher than the above range, the adhesion of the copolymer to the pigment surface tends to decrease, and the storage stability of the dispersion tends to decrease.
In addition, the acid value of the copolymer in the present invention is a value obtained by converting the measured acid value (mgKOH / g) into a solid content according to the potentiometric titration method of JIS K0070.

The amphoteric resin dispersant (D) can be obtained by various production methods.
For example, the monomers (d1) to (d4) are polymerized in an organic solvent that can be azeotroped with water. Thereafter, an aqueous liquid medium represented by water and a neutralizing agent are added to neutralize at least a part of the carboxyl groups, the azeotropic solvent is distilled off, and an aqueous solution of the amphoteric resin type dispersant (D) or An aqueous dispersion can be obtained.
The organic solvent at the time of polymerization is not particularly limited as long as it is azeotropic with water, but is preferably highly soluble in the copolymer, preferably ethanol, 1-propanol, 2-propanol, 1-butanol, 1-butanol is preferred.

Alternatively, it is copolymerized in a hydrophilic organic solvent, neutralized by adding water and an amine to make it aqueous, and as described above, the hydrophilic organic solvent is not distilled off, and an aqueous liquid medium containing the hydrophilic organic solvent and water In addition, a solution in which the amphoteric resin dispersant (D) is dissolved or dispersed can be obtained.
In this case, the hydrophilic organic solvent used is preferably one having high solubility in the copolymer, preferably glycol ethers, diols, more preferably (poly) alkylene glycol monoalkyl ethers having 3 to 6 carbon atoms. Alkanediols are good.

The following are mentioned as a neutralizing agent used for neutralization of a copolymer.
For example, inorganic alkaline agents such as ammonia water, various organic amines such as dimethylaminoethanol, diethanolamine, and triethanolamine, alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide, organic acids and mineral acids Etc. can be used. The copolymer as described above is dispersed or dissolved in an aqueous liquid medium.

  Next, the binder composition (C) containing crosslinked resin fine particles will be described. The cross-linked resin fine particles of the present invention are resin fine particles having an internal cross-linked structure (three-dimensional cross-linked structure), and it is important that the fine particles are cross-linked inside the particles. When the cross-linked resin fine particles have a cross-linked structure, the electrolytic solution elution resistance can be secured, and the effect can be enhanced by adjusting the cross-linking inside the particles. Further, when the cross-linked resin fine particles contain a specific functional group, it is possible to contribute to adhesion with the current collector or the electrode. Furthermore, the composition for secondary battery electrode formation excellent in flexibility can be obtained by adjusting the quantity of a crosslinked structure and a functional group. However, for the purpose of adjusting the flexibility of the binder, cross-linking of particles (inter-particle cross-linking) can be used together, but in this case, since a cross-linking agent is added later, the electrolyte solution of the cross-linking agent component In some cases, leakage of the electrode and variations in electrode fabrication may occur. For this reason, it is necessary to use a crosslinking agent to such an extent that the electrolyte solution resistance is not impaired.

The crosslinked resin fine particles used in the composition for forming a secondary battery electrode of the present invention are resin fine particles obtained by emulsion polymerization of an ethylenically unsaturated monomer in water in the presence of a surfactant with a radical polymerization initiator. It is. The crosslinked resin fine particles used in the present invention are preferably obtained by emulsion polymerization of an ethylenically unsaturated monomer containing the following monomers (c1) and (c2) in the following proportions.
(C1) From the group consisting of an ethylenically unsaturated monomer (c1) having a monofunctional or polyfunctional alkoxysilyl group, and a monomer (c2) having two or more ethylenically unsaturated groups in one molecule At least one monomer selected: 0.1 to 5% by weight
(C2) Ethylenically unsaturated monomers (c3) other than the monomers (c1) to (c2): 95 to 99.9% by weight
(However, the total of the above (c1) to (c3) is 100% by weight)

Of the ethylenically unsaturated monomers constituting the crosslinked resin fine particles in the present invention, (c1) and (c3) are monomers having one ethylenically unsaturated group in one molecule unless otherwise specified. It shows that.
<About the monomer group (C1)>
The functional group (alkoxysilyl group, ethylenically unsaturated group) possessed by the monomer contained in the monomer group (C1) is a self-crosslinking reactive functional group, and is mainly used for particle internal crosslinking during particle synthesis. Has the effect of forming. Electrolytic solution resistance can be improved by sufficiently carrying out internal crosslinking of the particles. Therefore, it is possible to obtain crosslinked resin fine particles by using a monomer contained in the monomer group (C1). In addition, by sufficiently carrying out particle crosslinking, the resistance to electrolytic solution can be improved.

  Examples of the monomer (c1) having one ethylenically unsaturated group and an alkoxysilyl group in one molecule include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ- Methacryloxypropyl tributoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxypropylmethyl Dimethoxysilane, γ-methacryloxymethyltrimethoxysilane, γ-acryloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane, etc. It is.

  Examples of the monomer (c2) having two or more ethylenically unsaturated groups in one molecule include allyl (meth) acrylate, 1-methylallyl (meth) acrylate, and 2-methylallyl (meth) acrylate. 1-butenyl (meth) acrylate, 2-butenyl (meth) acrylate, 3-butenyl (meth) acrylate, 1,3-methyl-3-butenyl (meth) acrylate, 2- (meth) acrylate 2- Chloroallyl, 3-chloroallyl (meth) acrylate, o-allylphenyl (meth) acrylate, 2- (allyloxy) ethyl (meth) acrylate, allyl lactyl (meth) acrylate, citronellyl (meth) acrylate, (meth) Geranyl acrylate, rosinyl (meth) acrylate, cinnamyl (meth) acrylate, diallyl maleate, diallyl itaconic acid (Meth) acrylic acid esters containing ethylenically unsaturated groups such as vinyl (meth) acrylate, vinyl crotonate, vinyl oleate, vinyl linolenate, 2- (2′-vinyloxyethoxy) ethyl (meth) acrylate ; Ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, diacryl Multifunctional (meth) acrylic acid esters such as 1,1,1-trishydroxymethylethane acid, 1,1,1-trishydroxymethylethane triacrylate, 1,1,1-trishydroxymethylpropanetriacrylic acid Divinylbenzene, divinyl adipate, etc. Vinyls; diallyl isophthalate, diallyl phthalate, etc. diallyl such as diallyl maleate and the like.

  The purpose of the alkoxysilyl group or ethylenically unsaturated group in the monomer (c1) or monomer (c2) is to introduce a cross-linked structure into the particle by self-condensation or polymerization mainly during the polymerization. However, a part of it may remain inside or on the surface after polymerization. The remaining alkoxysilyl group or ethylenically unsaturated group contributes to interparticle crosslinking of the binder composition. In particular, an alkoxysilyl group is preferable because it has an effect of improving adhesion to the current collector.

In the present invention, the monomer contained in the monomer group (C1) is used in an amount of 0.1 to 5% by weight in the whole ethylenically unsaturated monomer (100% by weight in total) used for emulsion polymerization. It is characterized by that. Preferably it is 0.5 to 3 weight%. When the monomer contained in the monomer group (C1) is less than 0.1% by weight, the particles are not sufficiently cross-linked, and the resistance to electrolytic solution is deteriorated. On the other hand, if it exceeds 5% by weight, there will be a problem in the polymerization stability at the time of emulsion polymerization, or even if it can be polymerized, there will be a problem in storage stability.

<About monomer group (C2)>
The crosslinked resin fine particles used in the binder composition containing the crosslinked resin fine particles of the present invention are the monomer (c1) having one ethylenically unsaturated group and an alkoxysilyl group in one molecule, and 1 In addition to the monomer (c2) having two or more ethylenically unsaturated groups in the molecule, the monomer group (C2) is an ethylenically unsaturated group other than the monomers (c1) and (c2). The monomer (c3) having a group can be obtained by emulsion polymerization at the same time.

The monomer (c3) is not particularly limited as long as it is a monomer other than the monomers (c1) and (c2) and has an ethylenically unsaturated group.
Monomer (c4) having one ethylenically unsaturated group and monofunctional or polyfunctional epoxy group in one molecule, one ethylenically unsaturated group and monofunctional or polyfunctional amide group in one molecule And at least one monomer selected from the group consisting of a monomer (c5) having one ethylenically unsaturated group and a monofunctional or polyfunctional hydroxyl group in one molecule (c6) And the monomer (c7) having an ethylenically unsaturated group other than the monomer and the monomers (c1), (c2), and (c4) to (c6) can be used.
By using the monomers (c4) to (c6), an epoxy group, an amide group, or a hydroxyl group can be left in the particles or on the surface of the cross-linked resin fine particles. The physical properties of can be improved. In the monomers (c4) to (c6), the functional group tends to remain inside or on the surface of the particles even after the particle synthesis, and the adhesion effect to the current collector is large even in a small amount. Moreover, a part of them may be used for the crosslinking reaction, and by adjusting the degree of crosslinking of these functional groups, it is possible to balance the resistance to electrolytic solution and the adhesion.

Examples of the monomer (c4) having one ethylenically unsaturated group and a monofunctional or polyfunctional epoxy group in one molecule include glycidyl (meth) acrylate and 3,4-epoxycyclohexyl (meth) acrylate. Etc.

  Examples of the monomer (c5) having one ethylenically unsaturated group and a monofunctional or polyfunctional amide group in one molecule include, for example, a primary amide group-containing ethylenically unsaturated monomer such as (meth) acrylamide. N-methylol acrylamide, N, N-di (methylol) acrylamide, alkylol (meth) acrylamides such as N-methylol-N-methoxymethyl (meth) acrylamide; N-methoxymethyl- (meth) acrylamide, Monoalkoxy (meth) acrylamides such as N-ethoxymethyl- (meth) acrylamide, N-propoxymethyl- (meth) acrylamide, N-butoxymethyl- (meth) acrylamide, N-pentoxymethyl- (meth) acrylamide; N, N-di (methoxymethyl) acrylamide, N-ethoxy Methyl-N-methoxymethylmethacrylamide, N, N-di (ethoxymethyl) acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N, N-di (propoxymethyl) acrylamide, N-butoxymethyl-N- (Propoxymethyl) methacrylamide, N, N-di (butoxymethyl) acrylamide, N-butoxymethyl-N- (methoxymethyl) methacrylamide, N, N-di (pentoxymethyl) acrylamide, N-methoxymethyl-N Dialkoxy (meth) acrylamides such as (pentoxymethyl) methacrylamide; dialkylamino (meth) acrylamides such as N, N-dimethylaminopropylacrylamide and N, N-diethylaminopropylacrylamide; N, N- Methyl acrylamide, N, N-dialkyl such as diethyl acrylamide (meth) acrylamides; and diacetone (meth) keto group, such as acrylamide-containing (meth) acrylamides and the like.

Examples of the monomer (c6) having one ethylenically unsaturated group and a monofunctional or polyfunctional hydroxyl group in one molecule include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. 4-hydroxybutyl (meth) acrylate, 2- (meth) acryloyloxyethyl-2-hydroxyethylphthalic acid, glycerol mono (meth) acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, allyl Examples include alcohol.

Some of the functional groups of the monomers contained in the monomers (c4) to (c6) may react during particle polymerization and be used for intraparticle crosslinking. In the present invention, the monomer contained in the monomers (c4) to (c6) is 0.1 to 20% by weight in the whole ethylenically unsaturated monomer (100% by weight in total) used for emulsion polymerization. It is used. Preferably it is 1 to 15 weight%, Most preferably, it is 2 to 10 weight%. When the monomers (c4) to (c6) in the whole ethylenically unsaturated monomers (100% by weight in total) used for the emulsion polymerization are less than 0.1% by weight, the inside of the particles after polymerization or on the surface The amount of remaining functional groups is reduced, and cannot sufficiently contribute to the improvement of the adhesion of the current collector. On the other hand, if it exceeds 20% by weight, there will be a problem in the polymerization stability at the time of emulsion polymerization, or even if it can be polymerized, there will be a problem in the storage stability.

The monomer (c7) is not particularly limited as long as it is a monomer having an ethylenically unsaturated group other than the monomers (c1), (c2), and (c4) to (c6). For example, a monomer (c8) having one ethylenically unsaturated group and an alkyl group having 8 to 18 carbon atoms in one molecule, one ethylenically unsaturated group in one molecule, and a cyclic structure And the monomer (c9). When the monomer (c8) and / or the monomer (c9) is used for the emulsion polymerization as the monomer (c7) (including other monomers as the monomer (c7)) The monomers (c8) and (c9) are all monomers having an ethylenically unsaturated group ((c1), (c2), (c4) to (c6) and (c7)). It is preferable that 30 to 95 weight% is contained in total. It is preferable to use the monomer (c8) or the monomer (c9) because the particle stability during particle synthesis and the resistance to electrolytic solution are excellent. If it is less than 30% by weight, the electrolyte solution resistance may be adversely affected. If it exceeds 95% by weight, the stability during particle synthesis will be adversely affected, or even if synthesis is possible, the temporal stability of the particles will be impaired. There is a case.

Examples of the monomer (c8) having one ethylenically unsaturated group and an alkyl group having 8 to 18 carbon atoms in one molecule include 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and myristyl. (Meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate and the like can be mentioned.

Examples of the monomer (c9) having one ethylenically unsaturated group and a cyclic structure in one molecule include alicyclic ethylenically unsaturated monomers and aromatic ethylenically unsaturated monomers. It is done. Examples of the alicyclic ethylenically unsaturated monomer include cyclohexyl (meth) acrylate and isobornyl (meth) acrylate, and examples of the aromatic ethylenically unsaturated monomer include benzyl (meth) acrylate. Phenoxyethyl (meth) acrylate, styrene, α-methylstyrene, 2-methylstyrene, chlorostyrene, allylbenzene, ethynylbenzene and the like.

Examples of the monomer (c7) other than the monomer (c8) and the monomer (c9) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and n-butyl (meth). ) Alkyl group-containing ethylenically unsaturated monomers such as acrylate, pentyl (meth) acrylate, heptyl (meth) acrylate; nitrile group-containing ethylenically unsaturated monomers such as (meth) acrylonitrile; perfluoromethylmethyl (meta ) Acrylate, perfluoroethylmethyl (meth) acrylate, 2-perfluorobutylethyl (meth) acrylate, 2-perfluorohexylethyl (meth) acrylate, 2-perfluorooctylethyl (meth) acrylate, 2-perfluoroiso Nonylethyl (meth) acrylate, 2-par Fluorononylethyl (meth) acrylate, 2-perfluorodecylethyl (meth) acrylate, perfluoropropylpropyl (meth) acrylate, perfluorooctylpropyl (meth) acrylate, perfluorooctyl amyl (meth) acrylate, perfluorooctylun Perfluoroalkyl group-containing ethylenically unsaturated monomer having 1 to 20 carbon atoms such as decyl (meth) acrylate; perfluorobutylethylene, perfluorohexylethylene, perfluorooctylethylene, perfluorodecyl Perfluoroalkyl such as ethylene, perfluoroalkyl group-containing ethylenically unsaturated compounds such as alkylene; polyethylene glycol (meth) acrylate, methoxypolyethylene Glycol (meth) acrylate, ethoxypolyethyleneglycol (meth) acrylate, propoxypolyethyleneglycol (meth) acrylate, n-butoxypolyethyleneglycol (meth) acrylate, n-pentoxypolyethyleneglycol (meth) acrylate, phenoxypolyethyleneglycol (meth) acrylate , Polypropylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, ethoxypolypropylene glycol (meth) acrylate, propoxypolypropylene glycol (meth) acrylate, n-butoxypolypropylene glycol (meth) acrylate, n-pentoxypolypropylene glycol (meta ) Acrylate, phenoxy polypropylene glycol (Meth) acrylate, polytetramethylene glycol (meth) acrylate, methoxypolytetramethylene glycol (meth) acrylate, phenoxytetraethylene glycol (meth) acrylate, hexaethylene glycol (meth) acrylate, methoxyhexaethylene glycol (meth) acrylate Ethylenically unsaturated compounds having a polyether chain such as: ethylenically unsaturated compounds having a polyester chain such as a lactone-modified (meth) acrylate; (meth) acrylic acid dimethylaminoethyl methyl chloride salt, trimethyl-3- (1- (Meth) acrylamide-1,1-dimethylpropyl) ammonium chloride, trimethyl-3- (1- (meth) acrylamidopropyl) ammonium chloride, and trime Quaternary ammonium base-containing ethylenically unsaturated compounds such as ru-3- (1- (meth) acrylamide-1,1-dimethylethyl) ammonium chloride; vinyl acetate, vinyl butyrate, vinyl propionate, vinyl hexanoate, caprylic acid Fatty acid vinyl compounds such as vinyl, vinyl laurate, vinyl palmitate and vinyl stearate; Vinyl ether ethylenically unsaturated monomers such as butyl vinyl ether and ethyl vinyl ether; 1-hexene, 1-octene, 1-decene, 1 Α-olefinic ethylenically unsaturated monomers such as dodecene, 1-tetradecene and 1-hexadecene; allyl monomers such as allyl acetate and allyl cyanide; vinyl such as vinyl cyanide, vinylcyclohexane and vinylmethylketone Monomer; acetylene, ethynyl Examples include ethynyl monomers such as toluene.

Examples of the monomer (c7) other than the monomer (c8) and monomer (c9) include maleic acid, fumaric acid, itaconic acid, citraconic acid, and alkyl or alkenyl monoesters thereof. , Phthalic acid β- (meth) acryloxyethyl monoester, isophthalic acid β- (meth) acryloxyethyl monoester, terephthalic acid β- (meth) acryloxyethyl monoester, succinic acid β- (meth) acryloxyethyl Carboxyl group-containing ethylenically unsaturated monomers such as monoesters, acrylic acid, methacrylic acid, crotonic acid and cinnamic acid; Tertiary butyl group-containing ethylenically unsaturated monomers such as tertiary butyl (meth) acrylate; Sulfonic acid group-containing ethylenically unsaturated monomers such as vinyl sulfonic acid and styrene sulfonic acid; -Hydroxyethyl) methacrylate unsaturated phosphate-containing ethylenically unsaturated monomers; diacetone (meth) acrylamide, acrolein, N-vinylformamide, vinyl methyl ketone, vinyl ethyl ketone, acetoacetoxyethyl (meth) Keto group-containing ethylenically unsaturated monomers such as acrylate, acetoacetoxypropyl (meth) acrylate, acetoacetoxybutyl (meth) acrylate (monomers having one ethylenically unsaturated group and a keto group in one molecule) Body).

When a keto group-containing ethylenically unsaturated monomer is used as the monomer (c7), a polyfunctional hydrazide compound having two or more hydrazide groups capable of reacting with a keto group as a crosslinking agent is mixed with the binder composition. A tough coating film can be obtained by crosslinking between a keto group and a hydrazide group. This has excellent electrolytic solution resistance and binding properties. Furthermore, since it is possible to achieve both durability and flexibility in a high temperature environment due to repeated charge / discharge and heat generation, a long-life non-aqueous secondary battery with reduced discharge capacity reduction in the charge / discharge cycle is obtained. Can do.

Among the monomers (c7), an ethylenically unsaturated monomer having a carboxyl group, a tertiary butyl group (tertiary butanol is removed by heat to form a carboxyl group), a sulfonic acid group, and a phosphoric acid group. The resin fine particles obtained by copolymerization of the body have the effect of improving the physical properties such as the adhesion of the current collector, while the functional groups remain in the particles and on the surface even after polymerization, and at the same time agglomeration during synthesis Can be prevented, and the stability of the particles after synthesis may be maintained.

A part of the carboxyl group, tertiary butyl group, sulfonic acid group, and phosphoric acid group may react during polymerization and be used for intraparticle crosslinking. In the case of using a monomer containing a carboxyl group, a tertiary butyl group, a sulfonic acid group, and a phosphoric acid group, the total amount of ethylenically unsaturated monomers used in the emulsion polymerization (100% by weight in total) is 0. The content is preferably 1 to 10% by weight, more preferably 1 to 5% by weight. When the monomer containing a carboxyl group, tertiary butyl group, sulfonic acid group, and phosphoric acid group is less than 0.1% by weight, the stability of the particles may be deteriorated. On the other hand, when the content exceeds 10% by weight, the hydrophilicity of the binder composition becomes too strong, and the electrolytic solution resistance may deteriorate. Furthermore, these functional groups may react during drying and be used for cross-linking within or between particles.

For example, a carboxyl group can react with an epoxy group during polymerization and drying to introduce a crosslinked structure into the resin fine particles. Similarly, a tertiary butyl group can react with an epoxy group in the same manner as described above since tertiary butyl alcohol is generated and a carboxyl group is formed when heat of a certain temperature or higher is applied.

These monomers (c7) are used in combination of two or more of the above-mentioned monomers in order to adjust the polymerization stability and glass transition temperature of the particles, as well as the film formability and film properties. Can be used. Further, for example, by using (meth) acrylonitrile in combination, there is an effect that rubber elasticity is exhibited.

<Method for producing crosslinked resin fine particles>
The crosslinked resin fine particles of the present invention are synthesized by a conventionally known emulsion polymerization method.

<Emulsifier used in emulsion polymerization>
As the emulsifier used in the emulsion polymerization in the present invention, a conventionally known one such as a reactive emulsifier having an ethylenically unsaturated group or a non-reactive emulsifier having no ethylenically unsaturated group may be arbitrarily used. it can.

Reactive emulsifiers having an ethylenically unsaturated group can be further roughly classified into anionic and nonionic nonionic ones. Especially when anionic reactive emulsifier or nonionic reactive emulsifier having an ethylenically unsaturated group is used, the dispersion particle size of the copolymer becomes finer and the particle size distribution becomes narrower, so it is used as a binder for secondary battery electrodes. In this case, the resistance to electrolytic solution can be improved. These anionic reactive emulsifiers or nonionic reactive emulsifiers having an ethylenically unsaturated group may be used singly or in combination.

Specific examples of the anionic reactive emulsifier having an ethylenically unsaturated group are illustrated below, but the emulsifiers that can be used in the present invention are not limited to those described below.

As an emulsifier, an alkyl ether type (as commercial products, for example, Aqualon KH-05, KH-10, KH-20, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Adeka Soap SR-10N, SR-20N manufactured by ADEKA Co., Ltd., Laterum PD-104 manufactured by Kao Corporation); sulfosuccinic acid ester system (for example, LATEMUL S-120, S-120A, S-180P, S-180A manufactured by Kao Corporation, Elemiol manufactured by Sanyo Chemical Co., Ltd.) JS-2 etc.); alkylphenyl ether type or alkylphenyl ester type (commercially available products include, for example, Aqualon H-2855A, H-3855B, H-3855C, H-3856, HS-05 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) , HS-10, HS-20, HS-30, ADEKA Corporation ADEKA rear SDX-222, SDX-223, SDX-232, SDX-233, SDX-259, SE-10N, SE-20N, etc.) (meth) acrylate sulfate ester (commercially available products include, for example, Japanese emulsifiers) Antox MS-60, MS-2N, Sanyo Kasei Kogyo Co., Ltd., Eleminol RS-30, etc.); Phosphate ester (for example, H-3330PL, Daiichi Kogyo Seiyaku Co., Ltd., stock) Adeka Soap PP-70 manufactured by the company ADEKA).

Nonionic reactive emulsifiers that can be used in the present invention include, for example, alkyl ether-based (commercially available products such as Adeka Soap ER-10, ER-20, ER-30, ER-40, manufactured by ADEKA Corporation, Laterum PD-420, PD-430, PD-450, etc. manufactured by Kao Corporation; alkyl phenyl ethers or alkyl phenyl esters (for example, Aqualon RN-10, RN- manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 20, RN-30, RN-50, ADEKA Corporation ADEKA rear soap NE-10, NE-20, NE-30, NE-40, etc.); (meth) acrylate sulfate ester system (commercially available products include, for example, RMA-564, RMA-568, RMA-1114, etc. manufactured by Nippon Emulsifier Co., Ltd.) .

  When the functional group-containing crosslinked resin fine particles of the present invention are obtained by emulsion polymerization, a non-reactive emulsifier having no ethylenically unsaturated group is used in combination with the reactive emulsifier having an ethylenically unsaturated group as described above. be able to. Non-reactive emulsifiers can be broadly classified into non-reactive anionic emulsifiers and non-reactive nonionic emulsifiers.

Examples of non-reactive nonionic emulsifiers include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene alkyl such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether Sorbitan monolaurate, sorbitan monostearate, sorbitan higher fatty acid esters such as sorbitan trioleate; polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate; polyoxyethylene monolaurate, Polyoxyethylene higher fatty acid esters such as polyoxyethylene monostearate; oleic acid monoglyceride, stearic acid monoglyceride Glycerine higher fatty acid esters such as chloride, polyoxyethylene-polyoxypropylene block copolymers, and the like can be exemplified polyoxyethylene distyrenated phenyl ether.

Examples of non-reactive anionic emulsifiers include higher fatty acid salts such as sodium oleate; alkyl aryl sulfonates such as sodium dodecylbenzene sulfonate; alkyl sulfate esters such as sodium lauryl sulfate; polyoxyethylene lauryl ether Polyoxyethylene alkyl ether sulfates such as sodium sulfate; polyoxyethylene alkylaryl ether sulfates such as polyoxyethylene nonylphenyl ether sodium sulfate; sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, polyoxyethylene lauryl sulfosuccinic acid Alkylsulfosuccinic acid ester salts such as sodium and derivatives thereof; polyoxyethylene distyrenated phenyl ether And the like can be exemplified sulfuric ester salts.

  The usage-amount of the emulsifier used in this invention is not necessarily limited, According to the physical property calculated | required when a crosslinked resin fine particle is finally used as a binder for secondary battery electrodes, it can select suitably. For example, the amount of the emulsifier is usually preferably 0.1 to 30 parts by weight, more preferably 0.3 to 20 parts by weight, based on 100 parts by weight of the total of ethylenically unsaturated monomers. More preferably, it is in the range of 5 to 10 parts by weight.

In the emulsion polymerization of the crosslinked resin fine particles of the present invention, a water-soluble protective colloid can be used in combination. Examples of water-soluble protective colloids include polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, and modified polyvinyl alcohol; cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose salt; Examples thereof include saccharides, and these can be used alone or in a combination of plural kinds. The amount of the water-soluble protective colloid used is 0.1 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, per 100 parts by weight of the total of ethylenically unsaturated monomers.

<Aqueous medium used in emulsion polymerization>
Examples of the aqueous medium used in the emulsion polymerization of the crosslinked resin fine particles of the present invention include water, and a hydrophilic organic solvent can be used as long as the object of the present invention is not impaired.

<Polymerization initiator used in emulsion polymerization>
The polymerization initiator used for obtaining the crosslinked resin fine particles of the present invention is not particularly limited as long as it has the ability to initiate radical polymerization, and a known oil-soluble polymerization initiator or water-soluble polymerization initiator is used. can do.

  The oil-soluble polymerization initiator is not particularly limited, and examples thereof include benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butyl peroxy (2-ethylhexanoate), and tert-butyl peroxide. Organic peroxides such as oxy-3,5,5-trimethylhexanoate, di-tert-butyl peroxide; 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4- Examples thereof include azobis compounds such as dimethylvaleronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1′-azobiscyclohexane-1-carbonitrile. These can be used alone or in combination of two or more. These polymerization initiators are preferably used in an amount of 0.1 to 10.0 parts by weight with respect to 100 parts by weight of the ethylenically unsaturated monomer.

In the present invention, it is preferable to use a water-soluble polymerization initiator. For example, ammonium persulfate, potassium persulfate, hydrogen peroxide, 2,2′-azobis (2-methylpropionamidine) dihydrochloride and the like are conventionally known. A thing can be used conveniently. Moreover, when performing emulsion polymerization, a reducing agent can be used together with a polymerization initiator if desired. Thereby, it becomes easy to accelerate the emulsion polymerization rate or to perform the emulsion polymerization at a low temperature. Examples of such a reducing agent include reducing organic compounds such as metal salts such as ascorbic acid, ersorbic acid, tartaric acid, citric acid, glucose, formaldehyde sulfoxylate, sodium thiosulfate, sodium sulfite, sodium bisulfite, Examples include reducing inorganic compounds such as sodium bisulfite, ferrous chloride, Rongalite, thiourea dioxide, and the like. These reducing agents are preferably used in an amount of 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the total ethylenically unsaturated monomer.

<Conditions for emulsion polymerization>
In addition, it can superpose | polymerize by a photochemical reaction, radiation irradiation, etc. irrespective of an above described polymerization initiator. The polymerization temperature is not less than the polymerization start temperature of each polymerization initiator. For example, in the case of a peroxide-based polymerization initiator, it may be usually about 70 ° C. The polymerization time is not particularly limited, but is usually 2 to 24 hours.

<Other materials used for reaction>
Further, if necessary, sodium acetate, sodium citrate, sodium bicarbonate, etc. as a buffering agent, and octyl mercaptan, 2-ethylhexyl thioglycolate, octyl thioglycolate, stearyl mercaptan, lauryl mercaptan as a chain transfer agent A suitable amount of mercaptans such as t-dodecyl mercaptan can be used.

  When a monomer having an acidic functional group such as a carboxyl group-containing ethylenically unsaturated monomer is used for the polymerization of the crosslinked resin fine particles, it can be neutralized with a basic compound before or after the polymerization. When neutralizing, it can be neutralized with ammonia or alkylamines such as trimethylamine, triethylamine and butylamine; alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine and aminomethylpropanol; and a base such as morpholine. . However, it is a highly volatile base that is highly effective in drying, and preferred bases are aminomethylpropanol and ammonia.

<Characteristics of cross-linked resin fine particles>
<Glass transition temperature>
Further, the glass transition temperature (hereinafter also referred to as Tg) of the crosslinked resin fine particles is preferably -30 to 70 ° C, more preferably -20 to 30 ° C. When Tg is less than −30 ° C., the binder excessively covers the electrode active material, and the impedance tends to increase. On the other hand, when Tg exceeds 70 ° C., the flexibility and tackiness of the binder become poor, and the adhesion of the electrode active material to the current collector and the moldability of the electrode may be inferior. The glass transition temperature is a value obtained using a DSC (differential scanning calorimeter).

  The measurement of the glass transition temperature by DSC (differential scanning calorimeter) can be performed as follows. About 2 mg of resin obtained by drying the cross-linked resin fine particles is weighed on an aluminum pan, the test container is set on a DSC measurement holder, and the endothermic peak of the chart obtained under a temperature rising condition of 10 ° C./min is read. The peak temperature at this time is defined as the glass transition temperature of the present invention.

<Particle structure>
In the present invention, the particle structure of the crosslinked resin fine particles may be a multilayer structure, so-called core-shell particles. For example, it is possible to localize a resin in which a monomer having a functional group is mainly polymerized in the core part or the shell part, or to provide a difference in Tg or composition between the core and the shell, thereby improving the curability and drying. Property, film formability, and mechanical strength of the binder can be improved.

<Particle size>
The average particle diameter of the crosslinked resin fine particles is preferably 10 to 500 nm, more preferably 30 to 250 nm, from the viewpoint of the binding property of the electrode active material and the stability of the particles. Further, when a large amount of coarse particles exceeding 1 μm are contained, the stability of the particles is impaired, so that the coarse particles exceeding 1 μm are preferably at most 5% by weight. In addition, the average particle diameter in the present invention represents a volume average particle diameter and can be measured by a dynamic light scattering method.

The average particle diameter can be measured by the dynamic light scattering method as follows. The cross-linked resin fine particle dispersion is diluted with water 200 to 1000 times depending on the solid content. About 5 ml of the diluted solution is injected into a cell of a measuring device [Microtrack manufactured by Nikkiso Co., Ltd.], and the measurement is performed after inputting the solvent (water in the present invention) and the refractive index conditions of the resin according to the sample. The peak of the volume particle size distribution data (histogram) obtained at this time is defined as the average particle size of the present invention.

<Uncrosslinked compound (F) added to polymerized fine resin particles>
The binder composition containing the crosslinked resin fine particles of the present invention includes, in addition to the crosslinked resin fine particles, an uncrosslinked epoxy group-containing compound, an uncrosslinked amide group-containing compound, an uncrosslinked hydroxyl group-containing compound, and an uncrosslinked And at least one uncrosslinked compound (F) selected from the group consisting of the oxazoline group-containing compounds (hereinafter sometimes referred to as compound (F)).

The “uncrosslinked functional group-containing compound” that is the compound (F) is an internal cross-linked structure (three-dimensional cross-linked structure) of the cross-linked resin fine particles of the present invention like the monomers contained in the monomer group (C1). Unlike the compound that forms (), it is a compound that is added after the resin fine particles are subjected to emulsion polymerization (polymer formation) (does not participate in the internal cross-linking of the resin fine particles). That is, “uncrosslinked” means not involved in the formation of the internal crosslinked structure (three-dimensional crosslinked structure) of the crosslinked resin fine particles of the present invention.

  The cross-linked resin fine particles have a cross-linked structure, so that the electrolytic solution resistance is secured, and by using the compound (F), it is selected from an epoxy group, an amide group, a hydroxyl group, and an oxazoline group in the compound (F). The at least one functional group may contribute to adhesion with the current collector or the electrode. Furthermore, the binder composition for secondary battery electrodes excellent in flexibility can be obtained by adjusting the amount of the crosslinked structure and functional group.

The crosslinked resin fine particles in the present invention must be crosslinked inside the particles. Electrolytic solution resistance can be ensured by appropriately adjusting the crosslinking inside the particles. Furthermore, the functional group-containing crosslinked resin fine particles are at least one selected from the group consisting of an uncrosslinked epoxy group-containing compound, an uncrosslinked amide group-containing compound, an uncrosslinked hydroxyl group-containing compound, and an uncrosslinked oxazoline group-containing compound. By adding the uncrosslinked compound (F), an epoxy group, an amide group, a hydroxyl group, or an oxazoline group acts on the current collector, and the adhesion to the current collector or the electrode can be effectively improved. Since the functional group contained in the compound (F) is stable by heat during long-term storage or electrode preparation, the effect of adhesion to the current collector is large even when used in a small amount. Furthermore, it is excellent in storage stability. Compound (F) may react with the functional group in the cross-linked resin fine particles for the purpose of adjusting the flexibility and the electrolytic solution resistance of the binder. If the functional group in the compound (F) is used too much for the reaction, the functional group capable of interacting with the current collector or the electrode is reduced. For this reason, the reaction between the crosslinked resin fine particles and the compound (F) needs to be at a level that does not impair the adhesion to the current collector or the electrode. In addition, when a part of the functional group contained in the compound (F) is used for the crosslinking reaction [when the compound (F) is a polyfunctional compound], by adjusting the degree of crosslinking of these functional groups, It is possible to balance the resistance to electrolytic solution and the adhesion.

<Uncrosslinked epoxy group-containing compound>
Examples of the uncrosslinked epoxy group-containing compound include epoxy group-containing ethylenically unsaturated monomers such as glycidyl (meth) acrylate and 3,4-epoxycyclohexyl (meth) acrylate; Radical polymerization resins obtained by polymerizing ethylenically unsaturated monomers containing monomers; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol Diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) Cyclohexane Polyfunctional epoxy compounds; bisphenol A- epichlorohydrin epoxy resins, and epoxy resins such as bisphenol F- epichlorohydrin type epoxy resin.

Among epoxy group-containing compounds, in particular, epoxy resins such as bisphenol A-epichlorohydrin type epoxy resins and bisphenol F-epichlorohydrin type epoxy resins, and ethylenically unsaturated monomers containing epoxy group-containing ethylenically unsaturated monomers. A radical polymerization resin obtained by polymerizing a saturated monomer is preferred. The epoxy resin can be expected to have a synergistic effect of improving the electrolytic solution resistance by having a bisphenol skeleton and improving the adhesion of the current collector by a hydroxyl group contained in the skeleton. In addition, the radical polymerization resin obtained by polymerizing an ethylenically unsaturated monomer containing an epoxy group-containing ethylenically unsaturated monomer has a higher adhesion to the current collector by having more epoxy groups in the resin skeleton. In addition, since it is a resin, an effect of improving the resistance to electrolytic solution can be expected as compared with the monomer.

<Uncrosslinked amide group-containing compound>
As an uncrosslinked amide group-containing compound, for example, a primary amide group-containing compound such as (meth) acrylamide; N-methylolacrylamide, N, N-di (methylol) acrylamide, N-methylol-N-methoxymethyl (meta) ) Alkylol (meth) acrylamide compounds such as acrylamide; N-methoxymethyl- (meth) acrylamide, N-ethoxymethyl- (meth) acrylamide, N-propoxymethyl- (meth) acrylamide, N-butoxymethyl- (meta ) Monoalkoxy (meth) acrylamide compounds such as acrylamide and N-pentoxymethyl- (meth) acrylamide; N, N-di (methoxymethyl) acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N, N -Di (Etoki Methyl) acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N, N-di (propoxymethyl) acrylamide, N-butoxymethyl-N- (propoxymethyl) methacrylamide, N, N-di (butoxymethyl) Dialkoxy (meth) acrylamides such as acrylamide, N-butoxymethyl-N- (methoxymethyl) methacrylamide, N, N-di (pentoxymethyl) acrylamide, N-methoxymethyl-N- (pentoxymethyl) methacrylamide Compounds; dialkylamino (meth) acrylamide compounds such as N, N-dimethylaminopropylacrylamide and N, N-diethylaminopropylacrylamide; N, N-dimethylacrylamide and N, N-diethylacrylamide Any dialkyl (meth) acrylamide compound; keto group-containing (meth) acrylamide compound such as diacetone (meth) acrylamide or the like, and the above amide group-containing ethylenically unsaturated monomers; Examples thereof include a radical polymerization resin obtained by polymerizing an ethylenically unsaturated monomer containing a monomer.

Among the amide group-containing compounds, radical polymerization resins obtained by polymerizing ethylenically unsaturated monomers including amide group-containing ethylenically unsaturated monomers such as acrylamide are particularly preferable. By having more amide groups in the resin skeleton, it is possible to improve the current collector adhesion, and by using the resin, the effect of improving the resistance to electrolytic solution compared to the monomer can be expected.

<Uncrosslinked hydroxyl group-containing compound>
Examples of the uncrosslinked hydroxyl group-containing compound include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate 4-hydroxyvinylbenzene, Hydroxyl group-containing ethylenically unsaturated monomers such as 1-ethynyl-1-cyclohexanol and allyl alcohol; radical polymerization obtained by polymerizing ethylenically unsaturated monomers containing the hydroxyl group-containing ethylenically unsaturated monomers Resins: linear aliphatic diols such as ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol; propylene glycol, neopentyl glycol 3-methyl-1,5 Pentanediol, 2,2-branched aliphatic diols such as diethyl-1,3-propanediol; and 1,4-bis cyclic diol such as (hydroxymethyl) cyclohexane.

  Among the hydroxyl group-containing compounds, radical polymerization resins obtained by polymerizing ethylenically unsaturated monomers including a hydroxyl group-containing ethylenically unsaturated monomer or cyclic diols are particularly preferable. The radical polymerization resin obtained by polymerizing ethylenically unsaturated monomers including hydroxyl group-containing ethylenically unsaturated monomers improves current collector adhesion by having more hydroxyl groups in the resin skeleton. In addition, the resin can be expected to have an effect of improving the resistance to electrolytic solution compared to the monomer. Moreover, cyclic diols can be expected to have an effect of improving the resistance to electrolytic solution by having a cyclic structure in the skeleton.

<Uncrosslinked oxazoline group-containing compound>
Examples of the uncrosslinked oxazoline group-containing compound include 2′-methylenebis (2-oxazoline), 2,2′-ethylenebis (2-oxazoline), and 2,2′-ethylenebis (4-methyl-2-oxazoline). ), 2,2′-propylenebis (2-oxazoline), 2,2′-tetramethylenebis (2-oxazoline), 2,2′-hexamethylenebis (2-oxazoline), 2,2′-octamethylene Bis (2-oxazoline), 2,2′-p-phenylenebis (2-oxazoline), 2,2′-p-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-p -Phenylenebis (4-methyl-2-oxazoline), 2,2'-p-phenylenebis (4-phenyl-2-oxazoline), 2,2'-m-phenylenebis (2-oxazoline), 2 , 2′-m-phenylenebis (4-methyl-2-oxazoline), 2,2′-m-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-m-phenylenebis ( 4-phenylenebis-2-oxazoline), 2,2′-o-phenylenebis (2-oxazoline), 2,2′-o-phenylenebis (4-methyl-2-oxazoline), 2,2′-bis (2-oxazoline), 2,2′-bis (4-methyl-2-oxazoline), 2,2′-bis (4-ethyl-2-oxazoline), 2,2′-bis (4-phenyl-2) -Oxazoline), and further an oxazoline group-containing radical polymerization resin.

Among oxazoline group-containing compounds, in particular, phenylene bis-type oxazoline compounds such as 2′-p-phenylenebis (2-oxazoline), or ethylenically unsaturated monomers containing an oxazoline group-containing ethylenically unsaturated monomer A radical polymerization resin obtained by polymerizing is preferred. The phenylenebis type oxazoline compound has an effect of improving the resistance to electrolytic solution by having a phenyl group in the skeleton. In addition, a radical polymerization resin obtained by polymerizing an ethylenically unsaturated monomer containing an oxazoline group-containing ethylenically unsaturated monomer has a current collector adhesion by having more oxazoline groups in the resin skeleton. In addition, by using a resin, the resistance to an electrolytic solution can be improved as compared with a monomer.

<Addition amount of compound (F), molecular weight>
The compound (F) is preferably added in an amount of 0.1 to 50 parts by weight, more preferably 5 to 40 parts by weight, based on 100 parts by weight of the solid content of the crosslinked resin fine particles. When the addition amount of the compound (F) is less than 0.1 parts by weight, the amount of the functional group contributing to the adhesion of the current collector is decreased, and may not sufficiently contribute to the improvement of the adhesion of the current collector. On the other hand, if it exceeds 50 parts by weight, the binder performance may be adversely affected such as leakage of the compound (F) into the electrolyte. Furthermore, two or more types of compounds (F) can be used in combination.

  Although the molecular weight of a compound (F) is not specifically limited, It is preferable that a weight average molecular weight is 1,000-1,000,000, Furthermore, 5,000-500,000 are more preferable. If the weight average molecular weight is less than 1,000, the adhesion effect to the current collector may not be sufficient, and if the weight average molecular weight exceeds 1,000,000, the viscosity of the compound may increase. There may be a case where handling properties at the time of electrode preparation are deteriorated. In addition, the said weight average molecular weight is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method. Furthermore, the compound (F) may be a compound that dissolves in a solvent or a compound that disperses.

<Composite ink>
As described above, the composition for forming a secondary battery electrode of the present invention can be used as a mixture ink or a composition for forming an underlayer. Therefore, a description will be given of a composite ink that essentially includes an active material, which is one of the preferred embodiments of the composition for forming a secondary battery electrode of the present invention. The composite ink includes a positive electrode composite ink or a negative electrode composite ink. The composite ink includes an electrode active material (A), a binder composition (C) containing crosslinked resin fine particles, and an amphoteric resin type dispersant ( D) and an aqueous liquid medium (E), and further a carbon material (B) which is a conductive additive can be used.

The positive electrode active material for the lithium ion secondary battery is not particularly limited, but metal oxides capable of doping or intercalating lithium ions, metal compounds such as metal sulfides, and conductive polymers are used. be able to.
Examples thereof include transition metal oxides such as Fe, Co, Ni, and Mn, composite oxides with lithium, and inorganic compounds such as transition metal sulfides. Specifically, transition metal oxide powders such as MnO, V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , layered structure lithium nickelate, lithium cobaltate, lithium manganate, spinel structure lithium manganate, etc. Examples thereof include composite oxide powders of lithium and transition metals, lithium iron phosphate materials that are phosphate compounds having an olivine structure, transition metal sulfide powders such as TiS ₂ and FeS, and the like.
In addition, conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can also be used. Moreover, you may mix and use said inorganic compound and organic compound.

The negative electrode active material for the lithium ion secondary battery is not particularly limited as long as it can be doped or intercalated with lithium ions. For example, metal Li, alloys thereof such as tin alloys, silicon alloys, lead alloys, etc., Li _X Fe ₂ O ₃ , Li _X Fe ₃ O ₄ , Li _X WO ₂ , lithium titanate, lithium vanadate, silicon Metal oxides such as lithium oxide, conductive polymers such as polyacetylene and poly-p-phenylene, amorphous carbonaceous materials such as soft carbon and hard carbon, artificial graphite such as highly graphitized carbon materials, or natural Examples thereof include carbonaceous powders such as graphite, carbon black, mesophase carbon black, resin-fired carbon materials, air-growth carbon fibers, and carbon fibers. These negative electrode active materials can be used alone or in combination.

Moreover, a conventionally well-known thing can be suitably selected as a positive electrode active material and negative electrode active material for nickel hydride secondary batteries. For example, the positive electrode active material is a nickel compound such as nickel hydroxide, nickel oxyhydroxide, or nickel oxide. Examples of the hydrogen storage alloy used as the active material of the negative electrode include AB5 type (rare earth type) such as LaNi5, AB / A2B type (titanium type) such as Tini and Ti2Ni, ZrNi type, MgNi type, and the like. In addition, LaNi of LaNi5 is replaced with Mish metal Mm, MnNi2Co3, MmNi4Co, etc. in which a part of Ni is replaced with Mn or Co, and alloy composition Mm (Ni, Mn, Co, etc.) m with Al added thereto. N, etc.).

  The size of these electrode active materials (A) is preferably in the range of 0.05 to 100 μm, and more preferably in the range of 0.1 to 50 μm. And it is preferable that the dispersed particle diameter of the electrode active material (A) in compound-material ink is 0.5-20 micrometers. The dispersed particle size referred to here is a particle size (D50) that is 50% when the volume ratio of the particles is integrated from the fine particle size distribution in the volume particle size distribution. A particle size distribution meter such as a dynamic light scattering type particle size distribution meter ("Microtrack UPA" manufactured by Nikkiso Co., Ltd.).

Next, the carbon material (B) which is a conductive support agent will be described.
The composite ink for forming a secondary battery electrode of the present invention preferably contains a carbon material (B) in order to further increase the conductivity of the formed electrode.
The carbon material (B), which is a conductive aid in the present invention, is not particularly limited as long as it is a conductive carbon material, but graphite, carbon black, conductive carbon fiber (carbon nanotube, carbon nanofiber) , Carbon fiber), fullerene and the like can be used alone or in combination of two or more. From the viewpoint of conductivity, availability, and cost, it is preferable to use carbon black.

  Carbon black is a furnace black produced by continuously pyrolyzing a gas or liquid raw material in a reactor, especially ketjen black using ethylene heavy oil as a raw material. Channel black that has been rapidly cooled and precipitated, thermal black obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, and particularly various types such as acetylene black using acetylene gas as a raw material, or 2 More than one type can be used in combination. Ordinarily oxidized carbon black, hollow carbon and the like can also be used.

  The oxidation treatment of carbon is performed by treating carbon at a high temperature in the air or by secondary treatment with nitric acid, nitrogen dioxide, ozone, etc., for example, such as phenol group, quinone group, carboxyl group, carbonyl group. This is a treatment for directly introducing (covalently bonding) an oxygen-containing polar functional group to the carbon surface, and is generally performed to improve the dispersibility of carbon. However, since it is common for the conductivity of carbon to fall, so that the introduction amount of a functional group increases, it is preferable to use the carbon which has not been oxidized.

As the specific surface area of the carbon black used increases, the number of contact points between the carbon black particles increases, which is advantageous in reducing the internal resistance of the electrode. Specifically, the specific surface area (BET) determined from the adsorption amount of nitrogen is 20 m ² / g or more and 1500 m ² / g or less, preferably 50 m ² / g or more and 1500 m ² / g or less, more preferably 100 m ^2. / G or more and 1500 m ² / g or less are desirable. When carbon black having a specific surface area of less than 20 m ² / g is used, it may be difficult to obtain sufficient conductivity, and carbon black of more than 1500 m ² / g may be difficult to obtain from commercially available materials. is there.

  Further, the particle size of the carbon black to be used is preferably 0.005 to 1 μm, particularly preferably 0.01 to 0.2 μm in terms of primary particle size. However, the primary particle diameter here is an average of the particle diameters measured with an electron microscope or the like.

It is desirable that the dispersed particle size in the composite ink of the carbon material (B), which is a conductive additive, be refined to 0.03 μm or more and 5 μm or less. It may be difficult to produce a composition having a dispersed particle size of the carbon material as the conductive aid of less than 0.03 μm. In addition, when a composition having a dispersed particle size of the carbon material as the conductive auxiliary agent exceeding 2 μm is used, there may be problems such as variations in the material distribution of the composite coating film and variations in the resistance distribution of the electrodes. .
The dispersed particle size referred to here is a particle size (D50) that is 50% when the volume ratio of the particles is integrated from the fine particle size distribution in the volume particle size distribution. A particle size distribution meter such as a dynamic light scattering type particle size distribution meter ("Microtrack UPA" manufactured by Nikkiso Co., Ltd.).

  Examples of commercially available carbon black include Toka Black # 4300, # 4400, # 4500, # 5500 (Tokai Carbon Co., Furnace Black), Printex L and the like (Degussa Co., Furnace Black), Raven 7000, 5750, 5250, 5000 ULTRA III, 5000 ULTRA, etc., Conductex SC ULTRA, Conductex 975 ULTRA, etc., PUER BLACK100, 115, 205, etc. (manufactured by Colombian, Furnace Black), # 2350, # 2400B, # 2600B, # 30050B, # 3030B, # 3030B, # 3030B 3350B, # 3400B, # 5400B, etc. (Mitsubishi Chemical Corporation, furnace black), MONARCH1400, 1300, 900, VulcanXC-7 2R, BlackPearls2000, etc. (Cabot, Furnace Black), Ensaco 250G, Ensaco 260G, Ensaco 350G, SuperP-Li (manufactured by TIMCAL), Ketjen Black EC-300J, EC-600JD (manufactured by Akzo), Denka Black, Denka Black HS Examples of graphite such as -100, FX-35 (manufactured by Denki Kagaku Kogyo Co., Ltd., acetylene black) include natural graphite such as artificial graphite, flake graphite, lump graphite, and earth graphite, but are not limited thereto. They may be used in combination of two or more.

  As the conductive carbon fibers, those obtained by firing from petroleum-derived raw materials are preferable, but those obtained by firing from plant-derived raw materials can also be used. For example, VGCF manufactured by Showa Denko Co., Ltd. manufactured with petroleum-derived raw materials can be mentioned.

Next, the aqueous liquid medium (E) will be described.
As the aqueous liquid medium (E) used in the present invention, it is preferable to use water, but if necessary, for example, a liquid medium compatible with water in order to improve the coating property to the current collector. May be used.
Liquid media compatible with water include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, and phosphoric acid esters , Ethers, nitriles and the like, and may be used as long as they are compatible with water.

  Furthermore, a film forming aid, an antifoaming agent, a leveling agent, a preservative, a pH adjuster, a viscosity adjuster, and the like can be blended in the composite ink as necessary.

Although it depends on the coating method, the viscosity of the composite ink is preferably 100 mPa · s or more and 30,000 mPa · s or less in the range of 30 to 90% by weight of the solid content.
It is preferable that the active material (A) is contained as much as possible within the viscosity range that can be applied. For example, the proportion of the active material (A) in the solid ink solid content is 80 wt% or more and 99 wt% or less. Is preferred.
Moreover, it is preferable that the ratio of the amphoteric resin type dispersant (D) in the solid ink solid content is 0.1 to 15% by weight.
When the carbon material (B) is included, the proportion of the carbon material (B) in the solid material ink solid content is preferably 0.1 to 15% by weight.

The composite ink of the present invention can be obtained by various methods.
However, the use of the carbon material (B) is arbitrary.
For example,
(4-1) An aqueous dispersion of an active material containing an active material (A), an amphoteric resin type dispersant (D), and an aqueous liquid medium (E) is obtained, and the carbon material (B) and A binder ink (C) containing crosslinked resin fine particles can be added to obtain a composite ink.
The binder composition (C) containing the carbon material (B) and the crosslinked resin fine particles can be added simultaneously, or after adding the carbon material (B), a binder may be added, and vice versa. Also good.
(4-2) Obtaining an aqueous dispersion of the conductive additive containing the carbon material (B), the amphoteric resin type dispersant (D) and the aqueous liquid medium (E), and adding the active material (A) to the aqueous dispersion A binder ink (C) containing crosslinked resin fine particles can be added to obtain a composite ink.
The active material (A) and the binder can be added simultaneously, or after adding the active material (A), the binder composition (C) containing crosslinked resin fine particles may be added, or vice versa. .
(4-3) An aqueous dispersion of an active material containing an active material (A), an amphoteric resin dispersant (D), a binder composition (C) containing crosslinked resin fine particles, and an aqueous liquid medium (E) is obtained. The carbon material (B) can be added to the aqueous dispersion to obtain a composite ink.
(4-4) An aqueous dispersion of a conductive additive containing a carbon material (B), an amphoteric resin type dispersant (D), a binder composition (C) containing crosslinked resin fine particles, and an aqueous liquid medium (E). An active material (A) can be added to the aqueous dispersion to obtain a composite ink.
(4-5) The active material (A), the carbon material (B), the amphoteric resin type dispersant (D), the binder composition (C) containing the crosslinked resin fine particles and the aqueous liquid medium (E) are mixed almost simultaneously. A composite ink can be obtained.

(Disperser / Mixer)
As an apparatus used for obtaining the composite ink, a disperser or a mixer which is usually used for pigment dispersion or the like can be used.
For example, mixers such as dispersers, homomixers, or planetary mixers; homogenizers such as “Clearmix” manufactured by M Technique, or “fillmix” manufactured by PRIMIX; paint conditioner (manufactured by Red Devil), ball mill, sand mill (Shinmaru Enterprises "Dynomill", etc.), Attritor, Pearl Mill (Eirich "DCP Mill", etc.), or Coball Mill, etc .; Media type dispersers; Wet Jet Mill (Genus, "Genus PY", Sugino Media-less dispersers such as “Starburst” manufactured by Machine, “Nanomizer” manufactured by Nanomizer, etc., “Claire SS-5” manufactured by M Technique, or “MICROS” manufactured by Nara Machinery; or other roll mills, etc. Although The present invention is not limited to these. Moreover, as the disperser, it is preferable to use a disperser that has been subjected to a metal contamination prevention treatment from the disperser.

  For example, when using a media-type disperser, a disperser in which the agitator and vessel are made of a ceramic or resin disperser, or the surface of the metal agitator and vessel is treated with tungsten carbide spraying or resin coating. Is preferably used. As the media, it is preferable to use glass beads, ceramic beads such as zirconia beads or alumina beads. Moreover, also when using a roll mill, it is preferable to use a ceramic roll. Only one type of dispersion device may be used, or a plurality of types of devices may be used in combination. Further, in the case of a positive or negative electrode active material in which particles are easily broken or crushed by a strong impact, a medialess disperser such as a roll mill or a homogenizer is preferable to a media type disperser.

<Underlayer forming composition>
As described above, the composition for forming a secondary battery electrode of the present invention can be used not only as a mixture ink but also as a composition for forming an underlayer.
The underlayer-forming composition contains a conductive additive (B), a binder composition (C) containing crosslinked resin fine particles, an amphoteric resin-type dispersant (D), and an aqueous liquid medium (E). About each component, it is the same as that of the case of compound ink.
The proportion of the carbon material (B) as a conductive additive in the total solid content of the composition used for the electrode underlayer is preferably 5% by weight or more and 95% by weight or less, and more preferably 10% by weight or more and 90% by weight or less. preferable. If the carbon material (B) as a conductive auxiliary agent is small, the conductivity of the underlayer may not be maintained. On the other hand, if the carbon material (B) as a conductive auxiliary agent is too much, the resistance of the coating film decreases. There is a case. Moreover, although the appropriate viscosity of electrode base layer ink is based on the coating method of electrode base layer ink, generally it is preferable to set it as 10 mPa * s or more and 30,000 mPa * s or less.

<Electrode>
The composite ink of the present invention can be applied and dried on a current collector to form a composite layer and obtain a secondary battery electrode.
Alternatively, the composition for forming an underlayer of the composition for forming a secondary battery electrode of the present invention is formed by forming an underlayer on the current collector, and providing a composite layer on the underlayer, for a secondary battery. An electrode can also be obtained. The composite material layer provided on the base layer may be formed using the above-described composite material inks (1) to (4) of the present invention, or may be formed using other composite material inks.

(Current collector)
The material and shape of the current collector used for the electrode are not particularly limited, and those suitable for various secondary batteries can be appropriately selected.
For example, examples of the material for the current collector include metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel. In the case of a lithium ion battery, aluminum is particularly preferable as the positive electrode material, and copper is preferable as the negative electrode material.
In general, foil on a flat plate is used as the shape, but the surface is roughened, porous foam, perforated foil, and mesh current collector. Can also be used.

There is no restriction | limiting in particular as a method of apply | coating mixed-material ink on a collector, A well-known method can be used.
Specific examples include die coating method, dip coating method, roll coating method, doctor coating method, knife coating method, spray coating method, gravure coating method, screen printing method or electrostatic coating method, and the like. Examples of methods that can be used include standing drying, blower dryers, hot air dryers, infrared heaters, and far-infrared heaters, but are not particularly limited thereto.
Moreover, you may perform the rolling process by a lithographic press, a calender roll, etc. after application | coating. The thickness of the electrode mixture layer is generally 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less. When the underlayer is provided, the thickness of the underlayer is generally 0.1 μm or more and 100 μm or less, preferably 0.5 μm or more and 50 μm or less.

<Secondary battery>
A secondary battery can be obtained by using the above electrode for at least one of a positive electrode and a negative electrode.
Secondary batteries include lithium-ion secondary batteries , sodium-sulfur secondary batteries, lithium-air secondary batteries, and the like. Conventionally known electrolytes and separators are appropriately used for each secondary battery. Can be used.

(Electrolyte)
A case of a lithium ion secondary battery will be described as an example. As the electrolytic solution, an electrolyte containing lithium dissolved in a non-aqueous solvent is used.
As the electrolyte, LiBF ₄ , LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₃ C , LiI, LiBr, LiCl, LiAlCl , LiHF 2, LiSCN, or LiBPh ₄ etc. but are not limited to.

The non-aqueous solvent is not particularly limited.
Carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate;
Lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone;
Glymes such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane;
Esters such as methyl formate, methyl acetate, and methyl propionate;
Sulfoxides such as dimethyl sulfoxide and sulfolane; and
Nitriles such as acetonitrile are exemplified. These solvents may be used alone or in combination of two or more.

  Furthermore, the electrolyte solution may be a polymer electrolyte that is held in a polymer matrix and made into a gel. Examples of the polymer matrix include, but are not limited to, an acrylate resin having a polyalkylene oxide segment, a polyphosphazene resin having a polyalkylene oxide segment, and a polysiloxane having a polyalkylene oxide segment.

(separator)
Examples of the separator include, but are not limited to, a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyamide nonwoven fabric and those obtained by subjecting them to a hydrophilic treatment.

(Battery structure / configuration)
The structure of the lithium ion secondary battery using the composition of the present invention is not particularly limited, but is usually composed of a positive electrode and a negative electrode, and a separator provided as necessary, a paper type, a cylindrical type, a button type, It can be made into various shapes according to the purpose of use, such as a laminated type.

  EXAMPLES The present invention will be described more specifically with reference to the following examples. However, the following examples do not limit the scope of rights of the present invention. In the examples and comparative examples, “part” represents “part by weight”.

(Dispersant synthesis example 1)
A reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer was charged with 200.0 parts of n-butanol and replaced with nitrogen gas. The inside of the reaction vessel was heated to 110 ° C., and a mixture of 100.0 parts of styrene, 60.0 parts of acrylic acid, 40.0 parts of dimethylaminoethyl methacrylate, and 12.0 parts of V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) The polymerization reaction was carried out dropwise over 2 hours. After completion of the dropwise addition, the mixture was further reacted at 110 ° C. for 3 hours, 0.6 parts of V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the reaction was further continued at 110 ° C. for 1 hour to obtain a copolymer (1) solution. Got. The weight average molecular weight of the copolymer (1) was about 10,000, and the acid value was 219.1 (mgKOH / g).
Further, after cooling to room temperature, 74.2 parts of dimethylaminoethanol was added for neutralization. This is the amount that neutralizes 100% of acrylic acid. Furthermore, after adding 400 parts of water and making it aqueous, it heated to 100 degreeC, butanol was azeotroped with water, and butanol was distilled off.
Dilution with water gave an aqueous solution or dispersion of an amphoteric resin dispersant (1) with a nonvolatile content of 20%. Moreover, the viscosity of the aqueous solution of the amphoteric resin type dispersant (1) having a nonvolatile content of 20% was 40 mPa · s.

(Dispersant Synthesis Examples 2 to 20)
The compounding compositions shown in Table 1 were synthesized in the same manner as in Synthesis Example 1 to obtain dispersants of Synthesis Examples 2-20.

Ｓｔ：スチレン
ＡＡ：アクリル酸
ＢｚＭＡ：ベンジルメタクリレート
ＤＭ：ジメチルアミノエチルメタクリレート
ＢＭＡ：メタクリル酸ブチル

St: Styrene AA: Acrylic acid BzMA: Benzyl methacrylate DM: Dimethylaminoethyl methacrylate BMA: Butyl methacrylate

<Preparation of aqueous dispersion of resin fine particles>
[Synthesis Example 21]
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser was charged with 40 parts of ion-exchanged water and 0.2 part of Adeka Soap SR-10 (manufactured by ADEKA) as a surfactant. 48.5 parts of methyl methacrylate, 50 parts of butyl acrylate, 1 part of acrylic acid, 0.5 part of 3-methacryloxypropyltrimethoxysilane, 53 parts of ion-exchanged water, and ADEKA rear soap SR-10 (ADEKA Corporation as a surfactant) 1% of the pre-emulsion that had previously been mixed with 1.8 parts was added. After raising the internal temperature to 70 ° C. and sufficiently substituting with nitrogen, 10% of 10 parts of a 5% aqueous solution of potassium persulfate was added to initiate polymerization. After maintaining the inside of the reaction system at 70 ° C. for 5 minutes, the remaining pre-emulsion and the remaining 5% aqueous solution of potassium persulfate were dropped over 3 hours while maintaining the internal temperature at 70 ° C., and stirring was further continued for 2 hours. . After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C. 25% aqueous ammonia was added to adjust the pH to 8.5, and the solid content was adjusted to 50% with ion exchange water to obtain a resin fine particle water dispersion. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

<Production of Compound (F) [Production of Epoxy Group-Containing Compound]>
[Production Example 1]
Into a reaction vessel equipped with a stirrer, thermometer, dropping funnel and refluxing vessel, 20 parts of isopropyl alcohol and 20 parts of water were charged, and 40 parts of methyl methacrylate, 40 parts of methyl acrylate and 20 parts of glycidyl methacrylate were separately added to the dropping tank 1, Moreover, 2 parts of potassium persulfate was dissolved in 30 parts of isopropyl alcohol and 30 parts of water, and charged into the dropping tank 2. After the internal temperature was raised to 80 ° C. and sufficiently substituted with nitrogen, the dropping tanks 1 and 2 were dropped over 2 hours to carry out polymerization. After completion of the dropwise addition, stirring was continued for 1 hour while maintaining the internal temperature at 80 ° C. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C., and an epoxy having a solid content of 50% A group-containing compound (methyl methacrylate / methyl acrylate / glycidyl methacrylate copolymer) solution was obtained. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

<Production of Compound (F) [Production of Amide Group-Containing Compound]>
[Production Example 2]
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a refluxing vessel was charged with 90 parts of water. Separately, 20 parts of acrylamide was dissolved in the dropping tank 1 and 2 parts of potassium persulfate was dissolved in 90 parts of water. The dropping tank 2 was charged. After the internal temperature was raised to 80 ° C. and sufficiently substituted with nitrogen, the dropping tanks 1 and 2 were dropped over 2 hours to carry out polymerization. After completion of dropping, stirring was continued for 1 hour while maintaining the internal temperature at 80 ° C. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C., and the amide having a solid content of 10% was obtained. A group-containing compound (polyacrylamide) solution was obtained. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

[Production Example 3]
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a refluxing vessel was charged with 40 parts of water. Separately, 40 parts of 2-ethylhexyl acrylate, 40 parts of styrene, and 20 parts of dimethylacrylamide were added to the dropping tank 1, and 2 parts of potassium sulfate was dissolved in 60 parts of water and charged into the dropping tank 2. After the internal temperature was raised to 80 ° C. and sufficiently substituted with nitrogen, the dropping tanks 1 and 2 were dropped over 2 hours to carry out polymerization. After completion of the dropping, stirring was continued for 1 hour while maintaining the internal temperature at 80 ° C. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C., and the amide having a solid content of 50% was obtained. A group-containing compound (2-ethylhexyl acrylate / styrene / dimethylacrylamide copolymer) solution was obtained. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

<Production of Compound (F) [Production of Hydroxyl-Containing Compound]>
[Production Example 4]
Into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a refluxing vessel, 20 parts of isopropyl alcohol and 20 parts of water are charged, and 40 parts of methyl methacrylate, 40 parts of butyl acrylate, and 20 parts of 2-hydroxyethyl methacrylate are separately added dropwise. In the tank 1, 2 parts of potassium persulfate was dissolved in 30 parts of isopropyl alcohol and 30 parts of water and charged into the dropping tank 2. After the internal temperature was raised to 80 ° C. and sufficiently substituted with nitrogen, the dropping tanks 1 and 2 were dropped over 2 hours to carry out polymerization. After completion of the dropping, stirring was continued for 1 hour while maintaining the internal temperature at 80 ° C. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C., and a hydroxyl group having a solid content of 50%. A containing compound (methyl methacrylate / butyl acrylate / 2-hydroxyethyl methacrylate copolymer) solution was obtained. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

[Synthesis Examples 22 to 41]
The compounding compositions shown in Table 2, Table 3, and Table 4 were synthesized in the same manner as in Synthesis Example 21, and resin fine particle aqueous dispersions of Synthesis Examples 22 to 41 were obtained. However, in Synthesis Examples 40 and 41, the resin aggregated during the emulsion polymerization, and the desired resin fine particles could not be obtained.

In addition, the description of the product name in Table 2 and Table 4 is as follows.
ADEKA rear soap SR-10; alkyl ether anionic surfactant (manufactured by ADEKA Corporation)
ADEKA rear soap ER-20; alkyl ether nonionic surfactant (manufactured by ADEKA Corporation)
Epoxy resin; product name Adeka Resin EM-1-60L, manufactured by ADEKA Corporation, epoxy equivalent 320, bisphenol A-epichlorohydrin type epoxy resin oxazoline-containing acrylic / styrene resin; product name Epocros K-2020E, manufactured by Nippon Shokubai Co., Ltd. , Oxazoline equivalent 550

(Carbon material dispersion for secondary battery electrode)
10 parts of acetylene black (Denka Black HS-100) as a carbon material which is a conductive additive, and 10 parts of an aqueous solution or an aqueous dispersion of the amphoteric resin type dispersant (1) described in Synthesis Example (1) (2% as solid content) Part) and 80 parts of water were mixed in a mixer, and further dispersed in a sand mill to obtain a carbon material dispersion (1) for a secondary battery electrode.

  With the formulation shown in Table 5, carbon material dispersions (2) to (24) for secondary battery electrodes were obtained in the same manner as the carbon material dispersion (1) for secondary battery electrodes.

(Composition for forming secondary battery electrode)
Composition for forming secondary battery electrode by mixing 30 parts of carbon material dispersion for secondary battery electrode shown in Table 5 and resin fine particle water dispersion shown in Tables 2 to 4 in an amount of 2 parts by weight in solid content (Table 6). Further, the degree of dispersion of the composition for forming a secondary battery electrode was determined by determination with a grind gauge (according to JISK5600-2-5). The evaluation results are shown in Table 6. The numbers in the table indicate the size of coarse particles. The smaller the value, the better the dispersibility and the more uniform secondary battery electrode forming composition.

(Electrolytic solution elution property of electrode obtained from secondary battery electrode forming composition)
The elution of the electrode obtained from the composition for forming a secondary battery electrode into the electrolytic solution is due to the electrode collapse after the battery is produced using the composition for forming a secondary battery electrode, and the peeling of the electrode layer from the current collector. It is desirable that the elution is not observed because it causes deterioration of battery characteristics. The evaluation of the electrolyte dissolution property was performed as follows. The composition for forming a secondary battery electrode shown in Table 6 was applied onto a 20 μm thick aluminum foil using a doctor blade, and then dried under reduced pressure to produce a composition film for forming a secondary battery electrode having a thickness of 5 μm. did. The obtained coating film was immersed in a 1: 1 (volume ratio) non-aqueous electrolyte solvent of ethylene carbonate and diethyl carbonate, stored in a 60 ° C. environment for 3 days, and then the state of the coating film was observed. The evaluation criteria are shown below, and the evaluation results are shown in Table 6.
○: “No disintegration or peeling of coating film”
Δ: “Partial disintegration and peeling of coating film are observed”
×: “Most of the coating film is disintegrated and peeled”

<Composite ink for lithium ion secondary battery electrode>, <Positive electrode>, <Coin-type battery>
[Example 16]
45 parts of LiCoO ₂ as a positive electrode active material, 2.5 parts of an aqueous solution of the amphoteric resin type dispersant (1) (0.5 parts as resin solids), 4 parts of the binder synthesized in Synthesis Example 21 (2 parts as solids) Then, 21.6 parts of water was mixed to produce a positive electrode material ink for a secondary battery electrode. The degree of dispersion of the composite ink was determined by determination with a grind gauge (according to JISK5600-2-5). Table 7 shows the evaluation results. The numbers in the table indicate the size of the coarse particles. The smaller the value, the better the dispersibility and the more uniform the ink mixture for secondary battery electrodes.
And after apply | coating this mixed-material ink for secondary battery electrodes for positive electrodes on the 20-micrometer-thick aluminum foil used as a collector using a doctor blade, it heat-drys under reduced pressure and the thickness of an electrode becomes 100 micrometers. Adjusted as follows.
Furthermore, the rolling process by a roll press was performed and the positive electrode whose thickness was set to 80 micrometers was produced.
The electrolyte dissolution property of the produced electrode was determined by the same method as that for the composition for forming a secondary battery electrode. Table 7 shows the evaluation results.

Next, the obtained positive electrode was punched into a diameter of 16 mm, a working electrode, a metallic lithium foil counter electrode, a separator (porous polypropylene film) inserted between the working electrode and the counter electrode, and an electrolytic solution (ethylene carbonate and diethyl carbonate). (Non-aqueous electrolyte solution in which LiPF ₆ is dissolved at a concentration of 1 M) in a mixed solvent in which the ratio of 1: 1 (volume ratio) is mixed. The coin-type battery was used in a glove box substituted with argon gas, and a predetermined battery characteristic evaluation was performed after the coin-type battery was produced.

(Electrode flexibility)
The electrode produced above was formed into a strip shape and wound so that the current collector side was in contact with a metal rod having a diameter of 3 mm, and cracks on the electrode surface that occurred during winding were determined by visual observation. The one that does not crack is more flexible.
○: “No cracks (a level where there is no practical problem)”
○ △: “In rare cases, cracks are seen (there is a problem, but the usable level)”
Δ: “Partial cracks are seen”
×: “Overall cracks are seen”

(Electrode adhesion)
Using the knife, the incision from the surface of the electrode to the depth reaching the current collector was cut into 6 grids in the vertical and horizontal directions at intervals of 2 mm. An adhesive tape was applied to the cut and immediately peeled off, and the degree of the active material falling off was determined by visual judgment. The evaluation criteria are shown below.
○: “No peeling (practical level)”
○ △: “Slightly peeled (problem but usable level)”
Δ: “About half peel”
×: “Peeling at most parts”

(Charge / discharge storage characteristics)
About the obtained coin-type battery, charging / discharging measurement was performed using the charging / discharging apparatus (SM-8 by Hokuto Denko).
When the active material to be used was LiFePO ₄ , constant current charging was continued to a charge end voltage of 4.2 V at a charging current of 1.0 mA (corresponding to 0.2 C). After the battery voltage reached 4.2 V, constant current discharge was performed at a discharge current of 1.0 mA until the discharge end voltage of 2.0 V was reached. These charging / discharging cycles were taken as one cycle, and 100 cycles of charging / discharging were repeated. The discharge capacity at the third cycle was defined as the initial discharge capacity (the initial discharge capacity was assumed to be 100% discharge capacity retention rate), and the discharge capacity retention rate after 100 cycles was calculated. (The closer to 100%, the better).
○: “Change rate is 95% or more. Particularly excellent.”
○ △: “Change rate is 90% or more and less than 95%. No problem at all”
Δ: “Change rate is 85% or more and less than 90%.
×: “Change rate is less than 85%.

Further, when the active material used is LiCoO ₂ , except that the charging current is 1.6 mA (equivalent to 0.2 C), the charging end voltage is 4.3 V, the discharging current is 1.6 mA, and the discharging end voltage is 2.8 V. As with LiFePO ₄ , charge / discharge storage characteristics can be measured.
Further, the active material to be used, in the case of _{LiNi1 / 3Mn1 / 3Co1 / 3O 2} , charging current 1.9 mA (0.2 C equivalent), charge voltage 4.3 V, the discharge current 1.9 mA, discharge end voltage Except for 2.8V, the charge / discharge storage characteristics can be measured in the same manner as LiFePO ₄ .
When the active material used is LiMn ₂ O ₄ , the charging current is 0.86 mA (corresponding to 0.2C), the charging end voltage is 4.3 V, the discharging current is 0.86 mA, and the discharging end voltage is 3.0 V. Except for the above, charge / discharge storage characteristics can be measured in the same manner as LiFePO ₄ .
Furthermore, when artificial graphite is used as the active material for the negative electrode (described later), the charging current is set to 0.8. . The charge / discharge storage characteristics can be measured in the same manner as LiFePO ₄ except that 85 mA (corresponding to 0.1 C), charge end voltage 0.1 V, discharge current 0.85 mA, and discharge end voltage 2.0 V.

[Examples 17 to 31], [Comparative Examples 10 to 25]
The combination of the active material shown in Table 7, the carbon material as the conductive auxiliary agent, the amphoteric resin type dispersant, the carbon material dispersion for the secondary battery electrode, the composition for forming the secondary battery electrode, and the resin fine particle water dispersion is changed. In the same manner as in Example 16 except that water was added so that the final solid content of the positive electrode secondary battery electrode mixture ink was 65% by weight, the positive electrode secondary battery electrode mixture ink and the positive electrode Obtained and evaluated in the same manner.

<Preparation of negative electrode for lithium ion secondary battery>
[Example 32]
94 parts of artificial graphite as a negative electrode active material, 2.5 parts of an aqueous solution of amphoteric resin-type dispersant (1) (0.5 parts as resin solids), 6 parts of resin fine particle aqueous dispersion synthesized in Synthesis Example 21 (solids) 3 parts) and 92.5 parts of water were mixed to prepare a composite ink for a secondary battery electrode for a negative electrode.
This negative electrode mixture ink was applied onto a copper foil having a thickness of 20 μm serving as a current collector using a doctor blade, and then dried by heating under reduced pressure so that the thickness of the electrode was adjusted to 100 μm. Rolling by roll press was performed to produce a negative electrode having a thickness of 80 μm, and the same evaluation as in the case of the positive electrode was performed. The charge / discharge retention characteristics were evaluated using an evaluation coin-type battery having a negative electrode as a working electrode and a metal lithium foil as a counter electrode.

[Examples 33 to 35], [Comparative Examples 26 to 32]
The combination of the active material shown in Table 7, the carbon material as the conductive auxiliary agent, the amphoteric resin type dispersant, the carbon material dispersion for the secondary battery electrode, the composition for forming the secondary battery electrode, and the resin fine particle water dispersion is changed. In the same manner as in Example 32 except that water was added so that the final solid content of the negative electrode secondary battery electrode mixture ink was 50% by weight, the negative electrode secondary battery electrode mixture ink and the negative electrode Obtained and evaluated in the same manner.

As shown in Table 7, when the composition for forming a secondary battery electrode of the present invention is used, the active material or the carbon material that is a conductive auxiliary agent is uniformly dispersed in the mixture ink. It is considered that the balance between flexibility and adhesiveness is achieved, and the charge / discharge storage characteristics are also improved in the battery characteristics.
As for this, when the carbon material that is the active material or the conductive assistant is insufficiently dispersed in the composite ink, a uniform conductive network as an electrode is not formed. It is considered that resistance distribution due to mechanical aggregation occurs, and current concentration occurs when used as a battery, so that deterioration is accelerated.
Moreover, when the dispersion control of the carbon material or the active material which is the conductive auxiliary agent is insufficient, the electrode adhesion tends to be insufficient. In particular, when the dispersion control of the carbon material that is a conductive additive is insufficient, the tendency is remarkable.
In addition, the present invention prevents the electrode from collapsing and peeling by suppressing the elution of the electrode coating film with respect to the electrolytic solution by an optimal combination of the dispersant and the resin fine particle water dispersion as the binder, and improves the battery characteristics. It is thought that. When the compatibility between the dispersant and the resin fine particle aqueous dispersion is poor as in the comparative example, it is considered that the electrode resistance increases or the electrode deteriorates due to the collapse or peeling of the electrode, and the durability of the battery is finally lowered. .
Therefore, when the composition for forming a secondary battery electrode of the present invention is used, the carbon material which is the active material and the conductive auxiliary agent is uniformly dispersed in the mixture ink, and further, the combination of the dispersant and the binder is By being good, it is considered that the dissolution of the electrode coating film with respect to the electrolytic solution is suppressed, so that the electrode is prevented from collapsing and peeling, and the inhibition of the battery reaction is reduced, thereby improving.

[Examples 36 and 37, Comparative Example 33]
The composition for forming a secondary battery electrode shown in Table 6 was applied onto an aluminum foil having a thickness of 20 μm as a current collector using a doctor blade, and then dried by heating to form a base layer so that the thickness became 5 μm. Formed.
Subsequently, after applying the mixture ink for secondary battery positive electrode shown in Table 7 on the said foundation layer, it dried under reduced pressure heating and obtained the positive electrode similarly to Example 16, and evaluated it similarly.

As shown in Table 8, when the composition for forming a secondary battery electrode of the present invention is used for the underlayer, it is even better than the evaluation results of Examples 18 and 27 in which the underlayer is not used. I understand that. This is presumably because the composition for forming a secondary battery electrode of the present invention made the contact portion between the current collector and the composite material layer more uniform and strong. However, the dispersion state of the composition for forming the secondary battery electrode for the underlayer of Comparative Example 6 and the elution resistance to the electrolytic solution are insufficient, and even in the case of using an electrode, it is compared with the evaluation result of Example 17. The result was inferior. This is presumably because the state of close contact between the current collector and the composite material layer was inadequate, resulting in a non-uniform state as an electrode as compared with the case where the base layer was not used.

Claims (7)

In a copolymer obtained by copolymerizing at least one of an electrode active material (A) or a carbon material (B) as a conductive additive, a binder composition (C) containing crosslinked resin fine particles, and the following monomers: A composition for forming a non-aqueous electrolyte secondary battery electrode, which contains an amphoteric resin type dispersant (D) obtained by neutralizing at least a part of the carboxyl group of the above with a basic compound and an aqueous liquid medium (E) .
Ethylenically unsaturated monomer having an aromatic ring (d1): 5 to 70% by weight
Ethylenically unsaturated monomer having a carboxyl group (d2): 15 to 60% by weight
Ethylenically unsaturated monomer having an amino group (d3): 1 to 80% by weight
Ethylenically unsaturated monomers (d4) other than (d1) to (d3): 0 to 79% by weight
(However, the total of (d1) to (d4) is 100% by weight) 2. The non-aqueous electrolyte solution according to claim 1, wherein the crosslinked resin fine particles are resin fine particles obtained by emulsion polymerization of the following monomers in water in the presence of a surfactant with a radical polymerization initiator. A composition for forming a secondary battery electrode.
(C1) an ethylenically unsaturated monomer (c1) having a monofunctional or polyfunctional alkoxysilyl group, and a monomer (c2) having two or more ethylenically unsaturated groups in one molecule At least one monomer selected: 0.1 to 5% by weight
(C2) Ethylenically unsaturated monomers (c3) other than the monomers (c1) to (c2): 95 to 99.9% by weight
(However, the total of the above (c1) to (c3) is 100% by weight) The composition for forming a nonaqueous electrolyte secondary battery electrode according to claim 2, wherein the ethylenically unsaturated monomer (c3) has the following composition.
Ethylenically unsaturated monomer having a monofunctional or polyfunctional epoxy group (c4), monomeric ethylenically unsaturated monomer having a monofunctional or polyfunctional amide group (c5), and ethylene having a monofunctional or polyfunctional hydroxyl group At least one monomer selected from the group consisting of polymerizable unsaturated monomers (c6): 0.1 to 20% by weight
Ethylenically unsaturated monomers (c7) other than the monomers (c1), (c2), (c4) to (c6): 75 to 99.8% by weight
(However, the total of the above (c1) to (c3) is 100% by weight) The composition for forming a nonaqueous electrolyte secondary battery electrode according to claim 3, wherein the ethylenically unsaturated monomer (c7) has the following composition.
At least one monomer selected from the group consisting of an ethylenically unsaturated monomer (c8) having an alkyl group having 8 to 18 carbon atoms and an ethylenically unsaturated monomer (c9) having a cyclic structure: 30 ~ 95% by weight
Ethylenically unsaturated monomers other than the above (c1) to (c6), (c8) and (c9): 0 to 69.8% by weight
(However, the total of the above (c1) to (c3) is 100% by weight) The binder composition (C) containing crosslinked resin fine particles is selected from the group consisting of an uncrosslinked epoxy group-containing compound, an uncrosslinked amide group-containing compound, an uncrosslinked hydroxyl group-containing compound, and an uncrosslinked oxazoline group-containing compound. The composition for forming a non-aqueous electrolyte secondary battery electrode according to any one of claims 1 to 4, wherein the composition comprises at least one uncrosslinked compound (F). A current collector, according to claim 1 to 5 non-aqueous electrolyte secondary having a either described non-aqueous electrolyte secondary battery mix layer is formed from the electrode-forming composition or electrode underlayer least more Secondary battery electrode. A non-aqueous electrolyte secondary battery having a positive electrode and the negative electrode and the electrolyte, wherein the positive electrode or at least one of the electrodes for nonaqueous electrolyte secondary battery according to claim 6, wherein said negative electrode, a nonaqueous electrolyte Liquid secondary battery.