JP6536564B2 - Binder composition for lithium ion secondary battery, slurry composition for lithium ion secondary battery electrode, slurry composition for lithium ion secondary battery porous film, electrode for lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Description

  The present invention relates to a binder composition for a lithium ion secondary battery, and more particularly to a binder composition that can be suitably used for forming a negative electrode of a lithium ion secondary battery.

  Lithium ion secondary batteries are characterized by small size, light weight, high energy density, and capable of repeated charge and discharge, and are used in a wide range of applications. Therefore, in recent years, improvement of battery members, such as an electrode and a separator, is examined for the purpose of the further performance improvement of a lithium ion secondary battery.

  Here, an electrode for a lithium ion secondary battery usually includes a current collector and an electrode mixture layer formed on the current collector. Then, the electrode mixture layer is formed by, for example, applying a slurry composition obtained by dispersing an electrode active material, a binder composition containing a binder, and the like in a dispersion medium on a current collector and drying it. Be done.

  Therefore, in recent years, in order to achieve further performance improvement of a lithium ion secondary battery, improvement of an electrode active material and a binder composition used for forming an electrode mixture layer has been attempted. Specifically, for example, for the negative electrode of a lithium ion secondary battery, the battery capacity of the lithium ion secondary battery can be increased by adopting a silicon-based negative electrode active material as an electrode active material (negative electrode active material) for the negative electrode. Is being considered.

  However, while the silicon-based negative electrode active material has a high theoretical capacity and can increase the battery capacity of the lithium ion secondary battery, it greatly expands and contracts with charge and discharge. Therefore, in the case of a negative electrode using a silicon-based negative electrode active material, the silicon-based negative electrode active material itself is degraded due to expansion and contraction of the silicon-based negative electrode active material due to repeated charging and discharging (that is, structural destruction of the silicon-based negative electrode active material) Miniaturization) and / or breakage of the electrode plate structure to break the conductive path in the electrode. That is, in a lithium ion secondary battery including a negative electrode using a silicon-based negative electrode active material, there is a problem that the cycle characteristics are degraded due to expansion and contraction of the silicon-based negative electrode active material.

  Therefore, for a negative electrode using a silicon-based negative electrode active material, a binder composition containing a predetermined non-crosslinkable polyacrylic acid as a binder is used to absorb and reduce expansion and contraction of the silicon-based negative electrode active material. There has been proposed a technique for suppressing the decrease in cycle characteristics of the ion secondary battery (see, for example, Patent Document 1).

JP 2007-35434 A

  However, in the conventional binder composition containing the predetermined non-crosslinked polyacrylic acid as a binder, the expansion and contraction of the negative electrode active material can not be sufficiently absorbed and relaxed, and the cycle characteristics of the lithium ion secondary battery Could not be sufficiently suppressed.

  Here, for such a problem, for example, the deterioration of the cycle characteristics can be suppressed by increasing absorption of the expansion and contraction of the negative electrode active material by increasing the compounding amount of the binder, and the binder It is conceivable to suppress the deterioration of the cycle characteristics by enhancing the rigidity of the above and suppressing expansion and contraction of the negative electrode active material.

  However, when the compounding amount of the binder is increased by the increase of the content of the binder in the binder composition or the increase of the amount of the binder composition used, a slurry composition prepared using the binder composition There is a risk that the stability of the product may decrease, and the productivity of the negative electrode may decrease. In addition, when a binder having high rigidity is used, cracking of the binder and peeling from the negative electrode active material are easily generated in the negative electrode prepared using the binder composition, and as a result, the negative electrode is provided. In the lithium ion secondary battery, gas generation assumed to be caused by cracking and peeling of the binder is increased, and the high temperature storage characteristics of the lithium ion secondary battery may be deteriorated.

  Therefore, the present invention secures the stability of the slurry composition and the productivity of the electrode even when used in combination with an electrode active material that greatly expands and contracts with charge and discharge of a silicon-based negative electrode active material and the like. It is an object of the present invention to provide a binder composition for a lithium ion secondary battery capable of exhibiting excellent cycle characteristics and high temperature storage characteristics in a lithium ion secondary battery.

  The present inventors diligently studied for the purpose of solving the above-mentioned problems. Then, the present inventors obtained by copolymerizing an ethylenically unsaturated carboxylic acid and / or a salt thereof with a polyoxyalkylene structure and a polyfunctional compound having two or more ethylenically unsaturated bonds in a predetermined ratio. By using a binder composition containing the above copolymer as a binder, it is possible to ensure excellent stability of the slurry composition and productivity of the electrode, as well as excellent cycle characteristics and high temperature storage characteristics for a lithium ion secondary battery. I found that I could make it work. In addition, the present inventor describes a protective layer comprising a binder composition containing the above-mentioned copolymer as a binder, a protective layer consisting of a porous film for lithium ion secondary batteries on a substrate such as an electrode or a separator (referred to as "heat resistant layer" It has been found that it can also be suitably used in forming the And the present inventor completed the present invention based on the above-mentioned new knowledge.

  That is, the present invention aims to advantageously solve the above-mentioned problems, and the binder composition for a lithium ion secondary battery of the present invention comprises at least one of an ethylenically unsaturated carboxylic acid and a salt thereof. A copolymer obtained by polymerizing a monomer composition containing an ethylenically unsaturated carboxylic acid compound, and a polyfunctional compound having a polyoxyalkylene structure and two or more ethylenically unsaturated bonds, The proportion of the ethylenically unsaturated carboxylic acid compound in all the monomers is 70.0% by mass to 99.9% by mass, and the proportion of the polyfunctional compound in all the monomers Is at least 0.1 mass% and at most 30.0 mass%. Such a binder composition containing as a binder a copolymer obtained by polymerizing a monomer composition containing an ethylenically unsaturated carboxylic acid compound and a polyfunctional compound in a predetermined ratio is suitable for charging and discharging. Even when used in combination with an electrode active material that greatly expands and contracts with it, the cycle characteristics and high-temperature storage excellent in lithium ion secondary batteries while securing the stability of the slurry composition and the productivity of the electrode The characteristics can be exhibited. Moreover, if the binder composition which contains the copolymer mentioned above as a binder is used, the porous film for lithium ion secondary batteries which is excellent in heat-shrinkage property can also be obtained.

  Here, as for the binder composition for lithium ion secondary batteries of this invention, it is preferable that the said copolymer contains carboxylic acid lithium base. When the copolymer contains lithium carboxylate (-COOLi), the stability of the slurry composition prepared using the binder composition is further improved. In addition, the battery characteristics (for example, initial coulomb efficiency, cycle characteristics, high temperature storage characteristics, etc.) of the lithium ion secondary battery manufactured using the binder composition are further improved.

And as for the binder composition for lithium ion secondary batteries of this invention, it is preferable that the electrolyte solution swelling degree of the said copolymer is 5 to 50 mass%. If the electrolyte solution swelling degree of the copolymer is 5 to 50% by mass, cycle characteristics and high temperature storage characteristics of the lithium ion secondary battery produced using the binder composition can be sufficiently improved.
In the present invention, the “electrolyte swelling degree” can be measured using the measurement method described in the examples of the present specification.

  Moreover, this invention aims at solving the said subject advantageously, The slurry composition for lithium ion secondary battery electrodes of this invention is a binder composition for any lithium ion secondary batteries mentioned above And electrode active materials. Thus, when the slurry composition for a lithium ion secondary battery electrode including any of the binder composition for a lithium ion secondary battery and the electrode active material described above is used for forming an electrode mixture layer, productivity of the electrode can be increased. A lithium ion secondary battery can be obtained that exhibits excellent cycle characteristics and high temperature storage characteristics while ensuring the same.

  Here, in the slurry composition for a lithium ion secondary battery electrode of the present invention, the electrode active material is preferably a Si-containing material. By using a Si-containing material as the electrode active material, a high capacity lithium ion secondary battery can be obtained.

  Moreover, this invention aims at solving the said subject advantageously, The slurry composition for lithium ion secondary battery porous films of this invention is a binder for any of the lithium ion secondary batteries mentioned above Composition and non-conductive particles. As described above, when a porous film is manufactured using any of the above-described binder composition for lithium ion secondary batteries and the slurry composition for lithium ion secondary battery porous films including nonconductive particles, excellent cycle characteristics can be obtained. And a lithium ion secondary battery exhibiting high temperature storage characteristics.

  Moreover, this invention aims at solving the said subject advantageously, The electrode for lithium ion secondary batteries of this invention is a slurry composition for any lithium ion secondary battery electrodes mentioned above. An electrode mixture layer prepared by using is provided on a current collector. As described above, an excellent cycle can be obtained by using the electrode for a lithium ion secondary battery provided on the current collector with the electrode mixture layer prepared using any of the above-described slurry compositions for lithium ion secondary battery electrodes. A lithium ion secondary battery exhibiting properties and high temperature storage characteristics is obtained.

  Furthermore, this invention aims at solving the said subject advantageously, The lithium ion secondary battery of this invention is equipped with a positive electrode, a negative electrode, electrolyte solution, and a separator, At least one of the said positive electrode and a negative electrode Is the above-described electrode for a lithium ion secondary battery. As described above, when at least one of the positive electrode and the negative electrode is the electrode for a lithium ion secondary battery described above, a lithium ion secondary battery exhibiting excellent cycle characteristics and high temperature storage characteristics can be obtained.

  Furthermore, this invention aims at solving the said subject advantageously, The lithium ion secondary battery of this invention is equipped with a positive electrode, a negative electrode, electrolyte solution, and a separator, The said positive electrode, a negative electrode, and a separator At least one of the above is characterized by comprising a porous film formed using the above-mentioned slurry composition for a lithium ion secondary battery porous film. As described above, when the porous film formed using the above-described slurry composition for a lithium ion secondary battery porous film is provided in at least one of the positive electrode, the negative electrode, and the separator, excellent cycle characteristics and high temperature storage A lithium ion secondary battery exhibiting the characteristics is obtained.

  According to the binder composition for a lithium ion secondary battery of the present invention, it is possible to exhibit excellent cycle characteristics and high temperature storage characteristics in a lithium ion secondary battery while securing the stability of the slurry composition and the productivity of the electrode. Can. Moreover, according to the binder composition for lithium ion secondary batteries of this invention, the porous film for lithium ion secondary batteries which is excellent in thermal contraction resistance can be provided. Furthermore, according to the present invention, it is possible to provide a slurry composition for a lithium ion secondary battery electrode that exhibits excellent cycle characteristics and high temperature storage characteristics while securing the productivity of the electrode. Furthermore, according to the present invention, it is possible to provide a slurry composition for a lithium ion secondary battery porous film which exhibits excellent cycle characteristics and high temperature storage characteristics. Furthermore, according to the present invention, it is possible to provide an electrode for a lithium ion secondary battery which exhibits excellent cycle characteristics and high temperature storage characteristics. And according to the present invention, a lithium ion secondary battery excellent in cycle characteristics and high temperature storage characteristics can be provided.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the binder composition for a lithium ion secondary battery of the present invention can be used when preparing a slurry composition for a lithium ion secondary battery electrode. And the slurry composition for lithium ion secondary battery electrodes of this invention prepared using the binder composition for lithium ion secondary batteries of this invention can be used when forming the electrode of a lithium ion secondary battery it can.
Moreover, the binder composition for lithium ion secondary batteries of this invention can be used when preparing the slurry composition for lithium ion secondary battery porous films. And the slurry composition for lithium ion secondary battery porous films of this invention prepared using the binder composition for lithium ion secondary batteries of this invention is a porous film on the electrode of lithium ion secondary batteries, and a separator. Can be used to form a porous membrane-attached substrate.

(Binder composition for lithium ion secondary battery)
The binder composition for a lithium ion secondary battery of the present invention comprises a binder and a solvent. The binder composition for a lithium ion secondary battery of the present invention comprises an ethylenically unsaturated carboxylic acid compound comprising at least one of an ethylenically unsaturated carboxylic acid and a salt thereof, a polyoxyalkylene structure, and two or more ethylenic properties. It is characterized in that a copolymer obtained by polymerizing a monomer composition containing a polyfunctional compound having an unsaturated bond in a predetermined ratio is contained as a binder.

<Binder>
The binder is formed by forming an electrode mixture layer on the current collector using the slurry composition for lithium ion secondary battery electrodes prepared using the binder composition for lithium ion secondary batteries of the present invention. In the manufactured electrode, the component contained in the electrode mixture layer can be held so as not to be detached from the electrode mixture layer.
The binder was formed on a substrate such as an electrode or separator using the slurry composition for a lithium ion secondary battery porous film prepared using the binder composition for a lithium ion secondary battery of the present invention. In the porous membrane, the components contained in the porous membrane can be held so as not to be detached from the porous membrane.

And the binder used for the binder composition for lithium ion secondary batteries of this invention is obtained by superposing | polymerizing the monomer composition which contains an ethylenically unsaturated carboxylic acid compound and a polyfunctional compound in a predetermined | prescribed ratio It is necessary to contain a copolymer.
The binder composition for a lithium ion secondary battery of the present invention may optionally further contain a polymer other than the above-mentioned copolymer as a binder.

Here, the binder composition for a lithium ion secondary battery of the present invention is a copolymer obtained by polymerizing a monomer composition containing an ethylenically unsaturated carboxylic acid compound and a polyfunctional compound in a predetermined ratio. Since it contains, even if it is a case where it is used for manufacture of the slurry composition for electrodes, an electrode, and a lithium ion secondary battery in combination with the electrode active material which expands and contracts greatly with charge and discharge, the slurry composition for electrodes The lithium ion secondary battery can exhibit excellent cycle characteristics and high temperature storage characteristics while securing product stability and electrode productivity.
In addition, since the binder composition for a lithium ion secondary battery of the present invention contains the above-mentioned copolymer, the stability of the slurry composition for a porous film and the productivity of the substrate with a porous film are ensured. The porous film for lithium ion secondary batteries which is excellent in heat-resistant shrinkability can be provided.

  In addition, the stability of the slurry composition for electrodes of the present invention, the productivity of the electrode, and the cycle characteristics and the high temperature storage characteristics of the lithium ion secondary battery can be improved by containing the above-mentioned copolymer. Although the reason why it can be done is not clear, it is presumed to be due to the following reasons. That is, a copolymer obtained by polymerizing a monomer composition containing an ethylenically unsaturated carboxylic acid compound and a polyfunctional compound in a predetermined ratio can be obtained by polymerizing only an ethylenically unsaturated carboxylic acid compound. It develops tough polymer physical properties as compared to polymers. More specifically, the copolymer, while having a reasonably high stiffness, is due to the use of a predetermined amount of ethylenically unsaturated carboxylic acid compound and the formation of a cross-linked structure through the ethylenically unsaturated bond of the multifunctional compound, The polyoxyalkylene structure of the multifunctional compound exhibits adequate flexibility. Therefore, according to the said copolymer which has high rigidity moderately, expansion | swelling and shrinkage | contraction of an electrode active material can be suppressed and the fall of cycling characteristics can be suppressed. Further, according to the above-mentioned copolymer having appropriate flexibility, it is possible to suppress the cracking of the copolymer and the peeling from the electrode active material, and to suppress the deterioration of the high temperature storage characteristics. Furthermore, according to the above-mentioned copolymer, by the interaction between polymer chains such as the formation of a cross-linked structure via the ethylenically unsaturated bond of the polyfunctional compound, the electrode slurry is secured while the stability of the slurry composition is ensured. The solid content concentration of the slurry composition can be increased to increase the productivity of the electrode. In addition, since the polyoxyalkylene structure of a polyfunctional compound is familiar with the electrolyte solution normally used in a lithium ion secondary battery, it is guessed that a copolymer is excellent also in lithium ion conductivity. Therefore, according to the said copolymer, it is guessed that a good SEI (Solid Electrolyte Interface) film can also be formed on surfaces, such as an electrode active material.

  In addition, when the binder composition for a lithium ion secondary battery of the present invention is used for preparation of a slurry composition for a porous membrane and formation of a porous membrane, the above-mentioned tough polymer physical properties and formation of a crosslinked structure, etc. It is surmised that the heat shrinkage resistance of the porous membrane is improved and the stability of the slurry composition for a porous membrane and the securing of the productivity of the porous membrane-attached substrate are achieved by the interaction between polymer chains. Furthermore, the binder composition for a lithium ion secondary battery of the present invention is used to prepare a slurry composition for a porous film and a porous film, as in the case of using the binder composition for the electrode slurry composition and electrode of the present invention. It is presumed that the battery characteristics of the lithium ion secondary battery can be improved also when used for the formation of

[Copolymer]
The copolymer used as a binder of the binder composition for a lithium ion secondary battery of the present invention is obtained by polymerizing a monomer composition described in detail below. And, usually, in this copolymer, structural units derived from the monomers contained in the monomer composition are in the same ratio as the abundance ratio of each monomer in the monomer composition. Contains

[[Monomer composition]]
The monomer composition used for preparation of the copolymer contains, for example, a monomer, an additive such as a polymerization initiator, and a polymerization solvent. And a monomer composition contains an ethylenically unsaturated carboxylic acid compound and a polyfunctional compound in a predetermined ratio as a monomer. Specifically, when the amount of all the monomers in the monomer composition is 100% by mass, the monomer composition contains 70.0% by mass or more and 99.9% by mass or less of ethylenic acid. It contains a saturated carboxylic acid compound and a polyfunctional compound at 0.1% by mass to 30.0% by mass. The monomer composition may optionally further contain, as a monomer, another compound copolymerizable with the ethylenically unsaturated carboxylic acid compound and the polyfunctional compound.

-Ethylenically unsaturated carboxylic acid compound-
As the ethylenically unsaturated carboxylic acid compound, at least one of an ethylenically unsaturated carboxylic acid and a salt thereof can be used. And, as the ethylenically unsaturated carboxylic acids, ethylenically unsaturated monocarboxylic acids and their derivatives, ethylenically unsaturated dicarboxylic acids and their acid anhydrides and their derivatives, etc. may be mentioned. In addition, examples of the ethylenically unsaturated carboxylic acid salts include sodium salts, potassium salts and lithium salts of ethylenically unsaturated carboxylic acids.
In addition, an ethylenically unsaturated carboxylic acid and its salt may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Here, examples of the ethylenically unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, crotonic acid and the like. And as an example of the derivative of the ethylenically unsaturated monocarboxylic acid, 2-ethyl acrylic acid, isocrotonic acid, α-acetoxy acrylic acid, β-trans-aryloxy acrylic acid, α-chloro-β-E-methoxy acrylic Acids, β-diaminoacrylic acid and the like can be mentioned.
Moreover, as an example of ethylenically unsaturated dicarboxylic acid, maleic acid, fumaric acid, itaconic acid etc. are mentioned. And as an example of the acid anhydride of ethylenically unsaturated dicarboxylic acid, maleic anhydride, a diacrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride etc. are mentioned. Furthermore, examples of derivatives of ethylenically unsaturated dicarboxylic acids include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate And dodecyl maleate, octadecyl maleate, fluoroalkyl maleate and the like.

In the binder composition for a lithium ion secondary battery of the present invention, an ethylenically unsaturated carboxylic acid salt, preferably a lithium salt of an ethylenically unsaturated carboxylic acid can be used as the ethylenically unsaturated carboxylic acid compound. . Since the water solubility of the resulting copolymer can be enhanced by using an ethylenically unsaturated carboxylic acid salt, when preparing the copolymer using water as a polymerization solvent, it is possible to use in the monomer composition. Even if the monomer concentration of (1) is high, it is possible to prevent the non-uniform progress of the polymerization due to the precipitation of the copolymer. Therefore, the polymerization can be uniformly progressed while the productivity is enhanced by using a monomer composition having a high monomer concentration. In addition, when a lithium salt of an ethylenically unsaturated carboxylic acid is used, lithium carboxylate (-COOLi) is introduced into the obtained copolymer, and the stability of the slurry composition is further improved. This is because battery characteristics (for example, initial coulomb efficiency, cycle characteristics, high temperature storage characteristics, etc.) of the secondary battery are further improved.
Further, from the viewpoint of further improving the cycle characteristics and high-temperature storage characteristics of a lithium ion secondary battery produced using the binder composition for a lithium ion secondary battery of the present invention, an acrylic acid as the ethylenically unsaturated carboxylic acid compound is It is preferable to use an acid, methacrylic acid or a salt thereof, and it is more preferable to use an acrylic acid or an acrylic acid salt.

  And as for the monomer which the monomer composition used for preparation of a copolymer contains, the ratio which the above-mentioned ethylenic unsaturated carboxylic acid compound occupies needs to be 70.0 mass% or more and 99.9 mass% or less. The proportion of the ethylenically unsaturated carboxylic acid compound in the monomer is preferably 80.0% by mass or more, more preferably 90.0% by mass or more, and 99.5% by mass or less It is more preferable that it is 99.0 mass% or less. When the proportion of the ethylenically unsaturated carboxylic acid compound in the monomer is less than 70.0% by mass, the rigidity of the copolymer decreases and the copolymer is prepared using the binder composition for a lithium ion secondary battery of the present invention. Cycle characteristics of the lithium ion secondary battery. On the other hand, when the proportion of the ethylenically unsaturated carboxylic acid compound in the monomer is more than 99.9% by mass, the rigidity of the copolymer becomes excessively high and becomes brittle, and as a result, the lithium ion of the present invention The high temperature storage characteristic of the lithium ion secondary battery manufactured using the binder composition for secondary batteries falls.

-Multifunctional compound-
Examples of the polyfunctional compound, Formula _{:-( C m H 2m O) n} - [ in the formula, m is an integer of 1 or more, n represents an is an integer of 2 or more] and a polyoxyalkylene structure represented by And compounds having two or more ethylenically unsaturated bonds can be used.
In addition, the compound which has a polyoxyalkylene structure and two or more ethylenic unsaturated bonds may be used individually by 1 type, and may be used combining 2 or more types by arbitrary ratios.

［式中、ｎは２以上の整数である］で表されるポリエチレングリコールジアクリレート。
（ＩＩ）下記一般式：

［式中、ｎは２以上の整数である］で表されるポリテトラメチレングリコールジアクリレート。
（ＩＩＩ）下記一般式：

［式中、ｎ１およびｎ２は、２以上の整数であり、互いに同一でも、異なっていても良い］で表されるエトキシ化ビスフェノールＡジアクリレート。
（ＩＶ）下記一般式：

［式中、ｎ１、ｎ２およびｎ３は、２以上の整数であり、互いに同一でも、異なっていても良い］で表されるエトキシ化グリセリントリアクリレート。
（Ｖ）下記一般式：

［式中、ｎ１、ｎ２、ｎ３およびｎ４は、２以上の整数であり、互いに同一でも、異なっていても良い］で表されるエトキシ化ペンタエリスリトールテトラアクリレート。Here, as a polyfunctional compound, poly (meth) acrylate of the polyol which has a polyoxyalkylene structure, etc. are mentioned, for example. Specifically, the polyfunctional compounds are not particularly limited, and the following compounds (I) to (V) may be mentioned. In the present invention, "(meth) acrylate" refers to acrylate and / or methacrylate.
(I) The following general formula:

Polyethylene glycol diacrylate represented by [wherein n is an integer of 2 or more].
(II) The following general formula:

The polytetramethylene glycol diacrylate represented by [In the Formula, n is an integer greater than or equal to 2].
(III) The following general formula:

An ethoxylated bisphenol A diacrylate represented by [wherein n 1 and n 2 are integers of 2 or more and may be the same as or different from each other].
(IV) The following general formula:

An ethoxylated glycerin triacrylate represented by [wherein n1, n2 and n3 are integers of 2 or more and may be the same as or different from each other].
(V) the following general formula:

An ethoxylated pentaerythritol tetraacrylate represented by [wherein n1, n2, n3 and n4 are integers of 2 or more and may be the same as or different from each other].

In addition, it is possible to increase the solid content concentration while securing the stability of the slurry composition prepared using the binder composition for a lithium ion secondary battery of the present invention, and the productivity of the electrode or the base material with a porous film is obtained. From the viewpoint of enhancing the number, the number (functionality) of the ethylenically unsaturated bond of the polyfunctional compound is preferably 2 or more and 6 or less, and more preferably 2 or more and 4 or less.
Further, from the viewpoint of further enhancing the productivity of the electrode and the porous film-attached substrate, the polyfunctional compound is preferably a 2 to 6 functional polyacrylate, and more preferably a 2 to 4 functional polyacrylate. .

Furthermore, from the viewpoint of improving the stability of the slurry composition prepared using the binder composition for a lithium ion secondary battery of the present invention and the high temperature storage characteristics of a lithium ion secondary battery, polyoxyalkylenes possessed by polyfunctional compounds structure _{(- (C m H 2m O} ) n -) integer m of preferably 20 or less, more preferably 15 or less, particularly preferably 10 or less, it is 2 or more preferable. If the integer m is too large, the stability of the slurry composition may be reduced. In addition, when the integer m is too small, the rigidity of the copolymer may be increased, and the high temperature storage characteristics of the lithium ion secondary battery may be deteriorated.
Further, for the same reason, the integer n of the polyoxyalkylene structure (— (C _m H _{2 m} O) _n —) possessed by the polyfunctional compound is preferably 20 or less, more preferably 15 or less, The number is particularly preferably 10 or less, preferably 2 or more, more preferably 3 or more, and particularly preferably 4 or more. If the integer n is too large, the stability of the slurry composition may be reduced. In addition, when the integer n is too small, the rigidity of the copolymer may be increased, and the high temperature storage characteristics of the lithium ion secondary battery may be deteriorated. Incidentally, the polyfunctional compound is more in the molecule polyoxyalkylene structure _{(- (C m H 2m O} ) n -) in the case where a is in the average value above the range of integer n of a plurality of polyoxyalkylene structures It is preferable to be contained, and it is further preferable that the integer n of all the polyoxyalkylene structures is contained in the said range.

  And the monomer which the monomer composition used for preparation of a copolymer requires that the ratio for which the polyfunctional compound mentioned above accounts is 0.1 mass% or more and 30.0 mass% or less, The proportion of the polyfunctional compound in the body is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and preferably 20.0% by mass or less. More preferably, it is 0% by mass or less. If the proportion of the polyfunctional compound in the monomer is less than 0.1% by mass, the rigidity of the copolymer becomes excessively high, and a lithium prepared using the binder composition for a lithium ion secondary battery of the present invention The high temperature storage characteristics of the ion secondary battery are degraded. On the other hand, when the proportion of the polyfunctional compound in the monomer is more than 30.0% by mass, sedimentation of the electrode active material and the like in the slurry composition prepared using the binder composition for a lithium ion secondary battery of the present invention While the productivity of the electrode or the base material with a porous film is lowered, the rigidity of the copolymer is lowered, and the cycle characteristics of the lithium ion secondary battery produced using the binder composition are lowered.

-Other compounds-
As the other compound which is a monomer optionally blended, a known compound copolymerizable with the above-mentioned ethylenically unsaturated carboxylic acid compound and polyfunctional compound can be used. And, other compounds are not particularly limited, and the solubility parameter (SP value) of a compound having two or more ethylenic unsaturated bonds and having no polyoxyalkylene structure, and a copolymer The compound which can adjust the magnitude | size of is mentioned.

  Specifically, as a compound having two or more ethylenic unsaturated bonds and having no polyoxyalkylene structure, for example, 1,6-hexanediol diacrylate, 1,9-nonane diol di Poly (meth) acrylates of polyols having no polyoxyalkylene structure such as acrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate and the like can be mentioned.

  Moreover, as a compound which can adjust the magnitude | size of the solubility parameter (SP value) of a copolymer, the electrolyte solution normally used for a lithium ion secondary battery and the compound whose SP value is close, for example, methyl methacrylate, methyl acrylate, Ethyl acrylate, butyl acrylate, acrylonitrile, 2-ethylhexyl acrylate, vinyl acetate and the like can be mentioned.

In addition, it is preferable that the ratio for which the compound which has a 2 or more ethylenic unsaturated bond and does not have a polyoxyalkylene structure accounts in a monomer is 5 mass% or less. If the proportion in the monomer exceeds 5% by mass, the stability of the slurry composition prepared using the binder composition for a lithium ion secondary battery may be reduced.
Moreover, it is preferable that the ratio for which the compound which can adjust the magnitude | size of the solubility parameter (SP value) of a copolymer accounts in a monomer is 10 mass% or less. If the proportion of the monomer in the monomer exceeds 10% by mass, the rigidity of the copolymer may be reduced and the cycle characteristics of the lithium ion secondary battery may be reduced.

-Additives-
Examples of the additive to be added to the monomer composition include known additives which can be used for the polymerization reaction such as a polymerization initiator such as potassium persulfate and a polymerization accelerator such as tetramethylethylene diamine. In addition, the kind and compounding quantity of an additive can be arbitrarily selected according to the polymerization method etc.

-Polymerization solvent-
As the polymerization solvent to be mixed with the monomer composition, known solvents capable of dissolving or dispersing the above-mentioned monomers can be used depending on the polymerization method and the like. Among them, water is preferably used as the polymerization solvent. In addition, as the polymerization solvent, an aqueous solution of any compound, a mixed solution of a small amount of organic medium and water, or the like may be used.

[[Preparation of copolymer]]
A copolymer used as a binder of the binder composition for a lithium ion secondary battery of the present invention is a monomer composition obtained by mixing the above-mentioned monomer, additive and polymerization solvent by a known method. Can be obtained, for example, by radical polymerization. The solution obtained by polymerizing the above monomer composition and containing a copolymer and a polymerization solvent may be used as it is as a binder composition, or it may be subjected to solvent substitution or addition of an optional component. May be used as a binder composition.

  Here, as the polymerization method, known polymerization methods such as aqueous solution polymerization, slurry polymerization, suspension polymerization, emulsion polymerization and the like can be mentioned, but the removal operation of the solvent is unnecessary, the safety of the solvent is high, and the interface Aqueous solution polymerization using water as a polymerization solvent is preferable because there is no problem of mixing of the activator. In the aqueous solution polymerization, the monomer composition is adjusted to a predetermined concentration, and the dissolved oxygen in the reaction system is sufficiently replaced with an inert gas, and then a radical polymerization initiator is added, if necessary, heating or ultraviolet light And the like by light irradiation.

When using water as a polymerization solvent and polymerizing the above-mentioned monomer composition in water to prepare an aqueous solution containing a copolymer, adjust the pH of the aqueous solution to 7 or more and 12 or less after polymerization. Is preferred. This is because the stability of the slurry composition and the high temperature storage characteristics of the lithium ion secondary battery can be further enhanced by adjusting the pH to 7 to 12 by neutralizing the obtained aqueous solution.
Here, when a monomer composition containing an ethylenically unsaturated carboxylic acid is used as the ethylenically unsaturated carboxylic acid compound, a basic lithium compound should be used when the above aqueous solution is neutralized. Is preferred. When a basic lithium compound is used, the carboxylic acid group in the copolymer becomes a lithium carboxylate (-COOLi), and the stability of the slurry composition is further improved, and the battery characteristics of the lithium ion secondary battery ( For example, the initial coulomb efficiency, cycle characteristics, high temperature storage characteristics, etc. are further improved. In addition, lithium carbonate (Li ₂ CO ₃ ) or lithium hydroxide (LiOH) can be used as the basic lithium compound, and lithium hydroxide is preferably used.

[[Properties of copolymer]]
The copolymer used as a binder of the binder composition for a lithium ion secondary battery of the present invention, prepared as described above, preferably has an electrolyte solution swelling degree of 5% by mass or more, 7 More preferably, it is 10% by mass or more, particularly preferably 10% by mass or more, particularly preferably 15% by mass or more, and preferably 120% by mass or less, and 70% by mass or less Is more preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 38% by mass or less, particularly preferably 35% by mass or less, 30 It is further particularly preferred that it is not more than mass%. When the electrolyte swelling degree is 5% by mass or more, flexibility of the copolymer can be secured, cracking and peeling of the copolymer can be suppressed, and the high temperature storage characteristics of the lithium ion secondary battery can be enhanced. In addition, lithium ion conductivity can be secured, and a high quality SEI film can be formed on the surface of the electrode active material or the like to reduce the internal resistance and gas generation of the lithium ion secondary battery. On the other hand, if the degree of swelling of the electrolyte solution is 120% by mass or less, the rigidity of the copolymer can be secured, expansion and contraction of the electrode active material can be suppressed, and cycle characteristics of the lithium ion secondary battery can be improved. .
In addition, the electrolyte solution swelling degree of a copolymer can be adjusted by changing the kind and quantity of a monomer in a monomer composition. Specifically, for example, the degree of swelling of the electrolyte can be increased by increasing the amount of the multifunctional compound.

  Further, the copolymer after pH adjustment is preferably a water-soluble polymer, and specifically, 0.5 g of the copolymer adjusted to pH = 7.5 to 9.0 at 25 ° C. It is preferable that the insoluble content at the time of melt | dissolving solid content conversion) in 100 g of water is 10 mass% or less. In addition, the insoluble part at the time of melt | dissolving a copolymer in water can become a foreign material, when preparing a slurry composition or an electrode. And especially in an electrode, the said insoluble matter may become a voltage concentration point and may cause lithium precipitation etc.

[Other polymers]
The binder composition for lithium ion secondary batteries of this invention which contains the copolymer mentioned above as a binder may further contain polymers other than the copolymer mentioned above as a binder.

And as polymers other than the copolymer mentioned above, known polymers, such as a particulate-form polymer dispersible in the solvent of a binder composition, are mentioned. Specifically, examples of the particulate polymer include diene polymers such as a styrene-butadiene copolymer and an acrylonitrile-butadiene copolymer, an acrylic polymer, a fluoropolymer, and a silicone polymer. The combined use of the copolymer and the particulate polymer can further improve the cycle characteristics and high-temperature storage characteristics of the lithium ion secondary battery.
In addition, these polymers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Here, when a slurry composition, an electrode, a substrate with a porous film and a lithium ion secondary battery are manufactured using a polymer other than the above-mentioned copolymer as a binder, the polymer other than the copolymer is Alternatively, as described above, it may be mixed with the copolymer beforehand to be used as a binder composition and then used for preparation of the slurry composition, or when preparing the slurry composition without being mixed beforehand with the copolymer. The substance may be mixed with the copolymer together with the substance (that is, the preparation of the binder composition containing a polymer other than the copolymer as a binder and the preparation of the slurry composition may be simultaneously carried out).

<Solvent>
As a solvent of the binder composition for lithium ion secondary batteries of the present invention, a known solvent capable of dissolving or dispersing the above-mentioned binder can be used. Among them, water is preferably used as the solvent. In addition, at least one part of the solvent of a binder composition is not specifically limited, It can be set as the polymerization solvent contained in the monomer composition used when preparing a copolymer.

<Other ingredients>
The binder composition for a lithium ion secondary battery of the present invention may contain, in addition to the components described above, a thickener as a known component that can be optionally added to the binder composition. Specifically, the binder composition may contain, as other components optionally blended, carboxymethyl cellulose, polysaccharide thickener, natural thickener such as alginic acid and starch, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, etc. The synthetic thickeners of the above (but excluding those corresponding to the above-mentioned copolymer) may be contained.

  In addition, when manufacturing a slurry composition, an electrode, a base material with a porous film, and a lithium ion secondary battery using the other components mentioned above, other components are previously mixed with a copolymer as mentioned above. The binder composition may be used for preparation of the slurry composition, or may be mixed with the electrode active material or the like at the time of preparation of the slurry composition without being previously mixed with the copolymer ( That is, preparation of a binder composition containing other components and preparation of a slurry composition may be carried out simultaneously).

(Slurry composition for lithium ion secondary battery electrode)
The slurry composition for a lithium ion secondary battery electrode of the present invention comprises the above-described binder composition for a lithium ion secondary battery of the present invention and an electrode active material. And the slurry composition for lithium ion secondary battery electrodes of this invention can be preferably used as a slurry composition for lithium ion secondary battery negative electrodes.

(Slurry composition for lithium ion secondary battery negative electrode)
So, below, the slurry composition for lithium ion secondary battery negative electrodes which can be prepared using the binder composition for lithium ion secondary batteries of this invention is demonstrated first.

  Here, a slurry composition for a lithium ion secondary battery negative electrode which can be prepared using the binder composition for a lithium ion secondary battery of the present invention comprises the binder composition described above, a negative electrode active material, and a dispersion medium such as water. And other components optionally added. That is, the slurry composition for a lithium ion secondary battery negative electrode contains at least the above-described copolymer, a negative electrode active material, and a dispersion medium such as water, and optionally, other polymers such as a particulate polymer, And other ingredients such as thickeners.

<Anode active material>
Here, as described above, the binder composition for a lithium ion secondary battery of the present invention is combined with a negative electrode active material that expands and contracts greatly with charge and discharge to produce a slurry composition, a negative electrode and a lithium ion secondary battery Even in the case of using the lithium ion secondary battery, excellent cycle characteristics and high temperature storage characteristics can be exhibited while securing the stability of the slurry composition and the productivity of the negative electrode. Therefore, in the slurry composition for lithium ion secondary battery negative electrode, from the viewpoint of increasing the capacity of lithium ion secondary battery, a silicon based negative electrode active material and optionally other negative electrode active materials are used as the negative electrode active material. Is preferred.

[Silicon-based negative electrode active material]
Here, the silicon-based negative electrode active material is an active material containing silicon. Then, as the silicon-based negative electrode active material, for example, silicon (Si), an alloy containing silicon, SiO, SiO _x , a Si-containing material obtained by coating or compounding a Si-containing material with conductive carbon and conductive carbon Complex compounds and the like can be mentioned. These silicon-based negative electrode active materials may be used alone or in combination of two or more.

The alloy containing silicon includes, for example, an alloy composition containing silicon and at least one element selected from the group consisting of titanium, iron, cobalt, nickel and copper.
Moreover, as an alloy containing silicon, for example, an alloy composition containing silicon, aluminum, and a transition metal such as iron, and further containing a rare earth element such as tin and yttrium is also included.

SiO _x is a compound containing at least one of SiO and SiO ₂ and Si, and x is usually at least 0.01 and less than 2. Then, SiO _x can be formed, for example, by utilizing disproportionation reaction of silicon monoxide (SiO). Specifically, SiO _x can be prepared by heat treating SiO, optionally in the presence of a polymer such as polyvinyl alcohol, to produce silicon and silicon dioxide. The heat treatment can be performed at a temperature of 900 ° C. or higher, preferably 1000 ° C. or higher, in an atmosphere containing an organic gas and / or a vapor, after grinding and mixing SiO and optionally a polymer.

  As a composite of Si-containing material and conductive carbon, for example, a ground mixture of SiO, a polymer such as polyvinyl alcohol and optionally a carbon material is heat-treated under an atmosphere containing, for example, an organic gas and / or a vapor. Compounds can be mentioned. In addition, the composite is a method of coating the surface of the particles of SiO with a chemical vapor deposition method using an organic gas, etc. Composite particles of the particles of SiO and graphite or artificial graphite are formed by granulation (granulation It can also be obtained by known methods such as the method of

From the viewpoint of increasing the capacity of the lithium ion secondary battery, an alloy containing silicon and SiO _x are preferable as the silicon-based negative electrode active material.

[Other negative electrode active materials]
As a negative electrode active material used together with the said silicon-type negative electrode active material in the slurry composition for lithium ion secondary battery negative electrodes, a carbon-type negative electrode active material, a metal type negative electrode active material, etc. are mentioned.

[[Carbon-based negative electrode active material]]
Here, the carbon-based negative electrode active material refers to an active material having carbon as a main skeleton capable of inserting lithium (also referred to as "doping"), and as the carbon-based negative electrode active material, for example, a carbonaceous material and graphite Quality materials.

The carbonaceous material is a material having a low degree of graphitization (i.e., low crystallinity) obtained by heat-treating a carbon precursor at 2000 ° C. or less to carbonize it. The lower limit of the heat treatment temperature at the time of carbonization is not particularly limited, but can be, for example, 500 ° C. or more.
And, as a carbonaceous material, for example, graphitizable carbon which easily changes the structure of carbon depending on the heat treatment temperature, non-graphitizable carbon having a structure close to an amorphous structure represented by glassy carbon and the like can be mentioned. .
Here, as the graphitizable carbon, for example, a carbon material using a tar pitch obtained from petroleum or coal as a raw material can be mentioned. Specific examples thereof include coke, mesocarbon microbeads (MCMB), mesophase pitch carbon fibers, and pyrolytic vapor grown carbon fibers.
Moreover, as non-graphitizable carbon, for example, a phenol resin fired body, polyacrylonitrile carbon fiber, quasi-isotropic carbon, a furfuryl alcohol resin fired body (PFA), hard carbon and the like can be mentioned.

The graphitic material is a material having high crystallinity close to that of graphite, which is obtained by heat-treating graphitizable carbon at 2000 ° C. or higher. The upper limit of the heat treatment temperature is not particularly limited, but can be, for example, 5000 ° C. or less.
And as a graphite material, natural graphite, artificial graphite, etc. are mentioned, for example.
Here, as the artificial graphite, for example, artificial graphite obtained by heat treating carbon containing graphitizable carbon mainly at 2800 ° C. or higher, graphitized MCMB obtained by heat treating MCMB at 2000 ° C. or higher, and mesophase pitch carbon fiber at 2000 ° C. The graphitized mesophase pitch carbon fiber etc. which were heat-treated above are mentioned.

[[Metal based negative electrode active material]]
The metal-based negative electrode active material is an active material containing a metal, and usually contains an element capable of inserting lithium in its structure, and the theoretical electric capacity per unit mass when lithium is inserted is 500 mAh / An active material of g or more. As the metal-based negative electrode active material, for example, a single metal other than Si which can form lithium metal or lithium alloy (for example, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb Sn, Sr, Zn, Ti, etc.) and alloys thereof, and oxides, sulfides, nitrides, carbides, phosphides, etc. thereof.

  From the viewpoint of sufficiently increasing the capacity of the lithium ion secondary battery while suppressing expansion and contraction of the negative electrode active material, it is preferable to use a carbon-based negative electrode active material as the other negative electrode active material, and artificial graphite It is more preferable to use That is, the negative electrode active material is preferably a mixture of a silicon-based negative electrode active material and a carbon-based negative electrode active material such as artificial graphite.

<Dispersion medium>
As a dispersion medium of the slurry composition for lithium ion secondary battery negative electrodes, a known dispersion medium can be used, without being limited in particular. Among them, water is preferably used as the dispersion medium. In addition, at least one part of the dispersion medium of a slurry composition can be made into the solvent which the binder composition used for preparation of a slurry composition contained, without being specifically limited.

<Other ingredients>
The said slurry composition for lithium ion secondary battery negative electrodes may contain components, such as a electrically conductive material, a reinforcing material, a leveling agent, electrolyte solution additive, etc. other than the said component. These are not particularly limited as long as they do not affect the cell reaction, and known ones such as those described in WO 2012/115096 can be used. One of these components may be used alone, or two or more thereof may be used in combination at an arbitrary ratio.

(Preparation method of slurry composition for lithium ion secondary battery negative electrode)
The slurry composition for a lithium ion secondary battery negative electrode can be prepared by dispersing the above components in a dispersion medium. Specifically, mixing the above respective components with the dispersion medium using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, leash crusher, ultrasonic disperser, homogenizer, planetary mixer, film mix, etc. The slurry composition can be prepared by
Here, as the dispersion medium, usually, water is used, but an aqueous solution of any compound, a mixed solution of a small amount of organic medium and water, or the like may be used.

In addition, the ratio of each said component in a slurry composition can be adjusted suitably.
Here, from the viewpoint of securing the performance of the lithium ion secondary battery while enhancing the stability of the slurry composition and the productivity of the negative electrode, the content ratio of the copolymer in the slurry composition is 100 parts by mass of the negative electrode active material. The amount is preferably 0.5 parts by mass or more and 10 parts by mass or less.
In addition, when the slurry composition includes other polymers (polymers other than the above-described copolymer), the content ratio of the other polymers in the slurry composition is, from the viewpoint of preventing the occurrence of powder loss, The amount is preferably 0.05 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the negative electrode active material. Here, when the slurry composition contains another polymer and a Si-containing material, the content ratio of the other polymer in the slurry composition is 0.5 mass per 100 mass parts of the negative electrode active material. It is more preferable that it is less than 1 part. When using a Si-containing material, it is desirable that the content of the other polymer be less than that usually used from the viewpoint of suppressing the expansion.
Furthermore, when the slurry composition contains a thickener, the content ratio of the thickener in the slurry composition is 0.3 per 100 parts by mass of the negative electrode active material from the viewpoint of improving the stability of the slurry composition. It is preferable that it is mass part or more and 5.0 mass parts or less. Here, as a ratio of a thickener and a copolymer, 2: 1-1: 2 are preferable and 3: 2-2: 3 are more preferable.

(Slurry composition for lithium ion secondary battery positive electrode)
Next, the slurry composition for lithium ion secondary battery positive electrodes which can be prepared using the binder composition for lithium ion secondary batteries of this invention is demonstrated.

The slurry composition for a lithium ion secondary battery positive electrode which can be prepared using the binder composition for a lithium ion secondary battery of the present invention needs the above-mentioned binder composition, a positive electrode active material, and a dispersion medium such as water. And other components such as a conductive material and a thickener added accordingly. That is, the slurry composition for a lithium ion secondary battery positive electrode contains at least the above-described copolymer, a positive electrode active material, and a dispersion medium such as water, and optionally, other polymers such as particulate polymers, And other components such as a conductive material and a thickener. Here, the slurry composition for a lithium ion secondary battery positive electrode prepared using the binder composition for a lithium ion secondary battery of the present invention further includes a particulate polymer as a binder and as a thickener It is preferred to include carboxymethylcellulose.
In addition, as the dispersion medium and the other components of the slurry composition for lithium ion secondary battery positive electrode, since the same one as the above-mentioned slurry composition for lithium ion secondary battery negative electrode can be used, the following description will be given. I omit it.

<Positive electrode active material>
As the positive electrode active material, a compound containing a transition metal, for example, a transition metal oxide, a transition metal sulfide, a composite metal oxide of lithium and a transition metal, and the like can be used. In addition, as a transition metal, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo etc. are mentioned, for example.

Here, as the transition metal oxide, for example, MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ O-P ₂ O ₅ , non-crystal Quality MoO ₃ , amorphous V ₂ O ₅ , amorphous V ₆ O _{13 and the} like.
As a transition metal sulfide, TiS ₂ , TiS ₃ , amorphous MoS ₂ , FeS, etc. may be mentioned.
As a composite metal oxide of lithium and transition metal, a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel type structure, a lithium-containing composite metal oxide having an olivine type structure, etc. are mentioned Be

Examples of lithium-containing composite metal oxides having a layered structure include lithium-containing cobalt oxides (LiCoO ₂ ), lithium-containing nickel oxides (LiNiO ₂ ), lithium-containing composite oxides of Co—Ni—Mn (Li (Co) Mn Ni) O ₂ ), Ni-Mn-Al lithium-containing composite oxide, Ni-Co-Al lithium-containing composite oxide, solid solution of LiMaO ₂ and Li ₂ MbO ₃ and the like can be mentioned. As the lithium-containing complex oxide of Co-Ni-Mn, Li [ Ni 0.5 Co 0.2 Mn 0.3] O 2, Li [Ni 1/3 Co 1/3 Mn 1/3] such as O ₂ and the like. Moreover, as a solid solution of LiMaO ₂ and Li ₂ MbO ₃ , for example, xLiMaO ₂ · (1-x) Li ₂ MbO _{3 and the} like can be mentioned. Here, x represents a number satisfying 0 <x <1, Ma represents one or more transition metals having an average oxidation state of 3+, and Mb represents one or more transition metals having an average oxidation state of 4+. Represent. As such a solid solution, Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O _{2 and the} like can be mentioned.
In the present specification, the "average oxidation state" indicates the average oxidation state of the "one or more transition metals", and is calculated from the molar amount and the valence of the transition metal. For example, when “one or more transition metals” is composed of 50 mol% of Ni ²⁺ and 50 mol% of Mn ^{4 +} , the average oxidation state of “one or more transition metals” is (0. 5) x (2+) + (0.5) x (4 +) = 3 +.

As a lithium-containing composite metal oxide having a spinel type structure, for example, a compound in which part of Mn of lithium manganate (LiMn ₂ O ₄ ) or lithium manganate (LiMn ₂ O ₄ ) is substituted with another transition metal Can be mentioned. Specific examples include _{Li s [Mn 2-t Mc} t] O 4 , such as LiNi _0.5 Mn _1.5 O _4. Here, Mc represents one or more transition metals having an average oxidation state of 4+. Specific examples of Mc include Ni, Co, Fe, Cu, Cr and the like. Further, t represents a number satisfying 0 <t <1, and s represents a number satisfying 0 ≦ s ≦ 1. Note that, as a positive electrode active material, a lithium-excess spinel compound represented by Li _{1 + x} Mn _2-x O ₄ (0 <X <2) can be used.

As a lithium-containing composite metal oxide having an olivine type structure, for example, olivine type phosphorus represented by Li _y MdPO ₄ such as olivine type lithium iron phosphate (LiFePO ₄ ) or olivine type lithium manganese phosphate (LiMnPO ₄ ) And lithium acid compounds. Here, Md represents one or more types of transition metals having an average oxidation state of 3+, and examples thereof include Mn, Fe, Co, and the like. Further, y represents a number satisfying 0 ≦ y ≦ 2. Furthermore, the olivine-type lithium phosphate compound represented by Li _y MdPO ₄ may have Md partially substituted by another metal. Examples of metals that can be substituted include Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, Si, B and Mo.

(Preparation Method of Slurry Composition for Lithium Ion Secondary Battery Positive Electrode)
The slurry composition for a lithium ion secondary battery positive electrode can be prepared by dispersing the above respective components in a dispersion medium, as in the slurry composition for a lithium ion secondary battery negative electrode. In addition, the ratio of each said component in a slurry composition can be adjusted suitably.

(Electrode for lithium ion secondary battery)
The electrode for a lithium ion secondary battery of the present invention comprises an electrode mixture layer prepared using the above-described slurry composition for lithium ion secondary battery electrodes (negative electrode and positive electrode) on a current collector.
Here, at least the electrode active material and the copolymer as a binder are contained in the electrode mixture layer of the lithium ion secondary battery electrode of the present invention. In addition, each component contained in the electrode mixture layer is contained in the said slurry composition for lithium ion secondary battery electrodes, The suitable abundance ratio of these each component is the slurry for electrodes It is the same as the preferred abundance ratio of each component in the composition.
And since the electrode for lithium ion secondary batteries of this invention is prepared using the binder composition for lithium ion secondary batteries of this invention, its productivity is high and the cycle of lithium ion secondary batteries It is possible to suppress the deterioration of the characteristics and the high temperature storage characteristics.

<Manufacture of electrode for lithium ion secondary battery>
In addition, the electrode for lithium ion secondary batteries of this invention apply | coats the process (coating process) of apply | coating the slurry composition for lithium ion secondary battery electrodes of this invention on a collector, for example, The slurry composition for a lithium ion secondary battery electrode is dried to form an electrode mixture layer on a current collector (drying step).
In addition, the electrode for lithium ion secondary batteries of this invention dry-granulates the slurry composition for lithium ion secondary battery electrodes mentioned above, prepares composite particle, and it is an electrode on a collector using the said composite particle. It can also be manufactured by a method of forming a mixture layer.

[Coating process]
As a method of apply | coating the slurry composition for lithium ion secondary battery electrodes of this invention on a collector, it does not specifically limit but a well-known method can be used. Specifically, as a coating method, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brushing method, or the like can be used. At this time, the electrode slurry composition may be applied to only one side of the current collector, or may be applied to both sides. The thickness of the slurry film on the current collector before coating and before drying may be appropriately set according to the thickness of the electrode mixture layer obtained by drying.

  Here, as a current collector to which the slurry composition for an electrode is applied, a material having electrical conductivity and electrochemical durability is used. Specifically, as the current collector, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum or the like can be used. Among them, copper foil is particularly preferable as a current collector used for the negative electrode. Moreover, as a collector used for a positive electrode, aluminum foil is especially preferable. In addition, the said material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

[Drying process]
The method for drying the electrode slurry composition on the current collector is not particularly limited, and any known method can be used. For example, hot air, hot air, drying with low humidity, vacuum drying, infrared rays, electron beam, etc. The drying method by irradiation is mentioned. By thus drying the electrode slurry composition on the current collector, an electrode mixture layer is formed on the current collector, and an electrode for a lithium ion secondary battery comprising the current collector and the electrode mixture layer. You can get

The electrode mixture layer may be subjected to pressure treatment using a die press or a roll press after the drying step. The pressure treatment can improve the adhesion between the electrode mixture layer and the current collector.
Furthermore, when the electrode mixture layer contains a curable polymer, it is preferable to cure the polymer after the formation of the electrode mixture layer.

(Slurry composition for lithium ion secondary battery porous film)
The slurry composition for a lithium ion secondary battery porous film of the present invention includes the above-described binder composition for a lithium ion secondary battery of the present invention and nonconductive particles.

More specifically, the slurry composition for a lithium ion secondary battery porous film of the present invention comprises the above-mentioned binder composition, non-conductive particles, a dispersion medium such as water, and the like, if necessary. And the ingredients of That is, the slurry composition for a lithium ion secondary battery porous film comprises at least the above-described copolymer, non-conductive particles, and a dispersion medium such as water, and optionally, other weights such as particulate polymer and the like. It further contains other components such as coalescence and thickeners.
In addition, it is preferable that the slurry composition for lithium ion secondary battery porous films of this invention further contains a particulate-form polymer as a binder, and contains carboxymethylcellulose as a thickener.

<Non-conductive particles>
As the nonconductive particles, both inorganic fine particles and organic fine particles can be used, but usually inorganic fine particles are used. Among them, as a material of the nonconductive particles, a material which is stably present in the use environment of the lithium ion secondary battery and is electrochemically stable is preferable. Preferred examples of the material of the nonconductive particles from such a point of view include aluminum oxide (alumina), silicon oxide, magnesium oxide (magnesia), calcium oxide, titanium oxide (titania), BaTiO ₃ , ZrO, alumina-silica. Oxide particles such as complex oxides; Nitride particles such as aluminum nitride and boron nitride; Covalent crystal particles such as silicon and diamond; Poorly soluble ionic crystal particles such as barium sulfate, calcium fluoride and barium fluoride; Talc And clay fine particles such as montmorillonite; and the like. In addition, these particles may be subjected to element substitution, surface treatment, solid solution formation, etc., as necessary. Furthermore, the non-conductive particles may contain one kind of the above materials alone in one particle, or may contain two or more kinds in combination in an arbitrary ratio. . Further, as the nonconductive particles, two or more types of particles formed of different materials may be used in combination. Among these, from the viewpoint of the stability in the electrolytic solution and the potential stability when a porous film-coated substrate prepared using the slurry composition for a porous film is applied to a lithium ion secondary battery, the oxide Particles are preferable, and in particular titanium oxide, magnesium oxide and aluminum oxide are more preferable, and aluminum oxide is particularly preferable, from the viewpoint of low water absorption and excellent heat resistance (for example, resistance to high temperatures of 180 ° C. or higher).

<Dispersion medium>
The dispersion medium for the slurry composition for a lithium ion secondary battery porous membrane of the present invention is not particularly limited, and any known dispersion medium can be used. Among them, water is preferably used as the dispersion medium. In addition, at least one part of the dispersion medium of a slurry composition can be made into the solvent which the binder composition used for preparation of a slurry composition contained, without being specifically limited.

<Other ingredients>
The slurry composition for a lithium ion secondary battery porous film of the present invention may contain components such as a reinforcing material, a leveling agent, and an electrolytic solution additive, in addition to the above components. These are not particularly limited as long as they do not affect the function of the porous membrane, and known ones such as those described in WO 2012/115096 can be used. One of these components may be used alone, or two or more thereof may be used in combination at an arbitrary ratio.

(Preparation method of slurry composition for lithium ion secondary battery porous film)
The slurry composition for a lithium ion secondary battery porous film of the present invention disperses the above respective components in a dispersion medium, similarly to the slurry composition for a lithium ion secondary battery negative electrode and the slurry composition for a lithium ion secondary battery positive electrode Can be prepared by In addition, the ratio of each said component in a slurry composition can be adjusted suitably.

(Base with porous membrane for lithium ion secondary battery)
The slurry composition for a lithium ion secondary battery porous membrane of the present invention can be used for the production of a porous membrane-attached substrate for a lithium ion secondary battery.
Here, the porous film-attached substrate for a lithium ion secondary battery comprises a substrate comprising an electrode or a separator and a porous film formed on the substrate, and the porous film comprises at least non-conductive particles. And a copolymer as a binder. In addition, each component contained in the electrode mixture layer is contained in the slurry composition for lithium ion secondary battery porous films, and the preferable abundance ratio of each of these components is the porous film. It is the same as the preferred abundance ratio of each component in the slurry composition.
And since the said base material with a porous film for lithium ion secondary batteries is prepared using the binder composition for lithium ion secondary batteries of this invention, productivity is high and it is excellent in heat-shrinkage resistance. ing. In addition, battery characteristics of the lithium ion secondary battery can be improved.

<Manufacture of porous film-coated substrate for lithium ion secondary battery>
In addition, the said base material with a porous film for lithium ion secondary batteries apply | coats the process (application process) of apply | coating the slurry composition for lithium ion secondary battery porous films mentioned above on a base material, and a base material The slurry composition for a lithium ion secondary battery porous membrane is dried to form a porous membrane on a substrate (drying step).

  Here, in the coating step and the drying step for producing the porous film-coated substrate for a lithium ion secondary battery, the slurry composition for a porous film is coated on the substrate instead of applying the electrode slurry composition on the current collector. Since it can carry out like manufacture of the electrode for lithium ion secondary batteries mentioned above except the point which apply | coats a thing, below, description is abbreviate | omitted.

(Lithium ion secondary battery)
The lithium ion secondary battery of the present invention comprises a positive electrode, a negative electrode, an electrolytic solution, and a separator, and at least one of the positive electrode and the negative electrode is the above-described electrode for a lithium ion secondary battery. Alternatively, the lithium ion secondary battery of the present invention comprises a positive electrode, a negative electrode, an electrolytic solution and a separator, and at least one of the positive electrode, the negative electrode and the separator (that is, at least one substrate) A porous film formed by using the slurry composition for a secondary battery porous film is provided. The lithium ion secondary battery of the present invention uses a porous film formed using the electrode of the present invention for lithium ion secondary batteries or the slurry composition for the lithium ion secondary battery of the present invention. Excellent in cycle characteristics and high temperature storage characteristics.
In addition, although the lithium ion secondary battery using the said negative electrode for lithium ion secondary batteries is demonstrated below, as a lithium ion secondary battery of this invention, the lithium using the said positive electrode for lithium ion secondary batteries as a positive electrode An ion secondary battery is also mentioned.

<Positive electrode>
As a positive electrode of the said lithium ion secondary battery, the known positive electrode used as a positive electrode for lithium ion secondary batteries can be used. Specifically, as the positive electrode, for example, a positive electrode formed by forming a positive electrode mixture layer on a current collector can be used.
Note that as the current collector, one made of a metal material such as aluminum can be used. As the positive electrode mixture layer, a layer containing a known positive electrode active material, a conductive material, and a binder can be used.

<Electrolyte solution>
As the electrolytic solution, an electrolytic solution in which an electrolyte is dissolved in a solvent can be used.
Here, an organic solvent capable of dissolving an electrolyte can be used as the solvent. Specifically, as a solvent, alkyl carbonate solvents such as ethylene carbonate, propylene carbonate, γ-butyrolactone, etc., 2,5-dimethyltetrahydrofuran, tetrahydrofuran, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl acetate, dimethoxyethane It is possible to use one to which a viscosity adjusting solvent such as dioxolane, methyl propionate or methyl formate is added.
A lithium salt can be used as the electrolyte. As a lithium salt, the thing of Unexamined-Japanese-Patent No. 2012-204303 can be used, for example. Among these lithium salts, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferable as the electrolyte from the viewpoint of being easily dissolved in an organic solvent and exhibiting a high degree of dissociation.

<Separator>
As a separator, the thing of Unexamined-Japanese-Patent No. 2012-204303 can be used, for example. Among these, it is possible to reduce the film thickness of the entire separator, thereby increasing the ratio of the electrode active material in the lithium ion secondary battery to increase the capacity per volume, and it is possible to use polyolefin. A microporous membrane made of a resin of the type (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred.

(Method of manufacturing lithium ion secondary battery)
In the above lithium ion secondary battery, for example, a positive electrode and a negative electrode are stacked via a separator, and this is wound or folded according to the battery shape as needed, and put into a battery container, and the battery container is electrolyzed It can be manufactured by injecting and sealing a liquid. A fuse, an over current protection element such as a PTC element, an expanded metal, a lead plate, etc. may be provided if necessary to prevent the pressure rise inside the lithium ion secondary battery and the occurrence of overcharge and discharge and the like. . The shape of the lithium ion secondary battery may be, for example, a coin, a button, a sheet, a cylinder, a square, or a flat.

EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, “%” and “parts” representing amounts are based on mass unless otherwise specified.
In Examples and Comparative Examples, the electrolyte swelling degree of the copolymer, the glass transition temperature and the gel content of the particulate polymer, the stability of the slurry composition, the productivity of the electrode, and the cycle of the lithium ion secondary battery Properties and storage stability were evaluated using the following methods, respectively.

<Electrolyte swelling degree>
The aqueous solution containing the copolymer was dried in an environment with a humidity of 50% and a temperature of 23 to 25 ° C. to form a film having a thickness of 1 ± 0.3 mm. The formed film was dried by a vacuum drier at a temperature of 60 ° C. for 10 hours, and then cut and precisely weighed about 1 g. The mass of the obtained film piece is W0. The film piece was prepared by using an electrolyte (composition: LiPF ₆ solution with a concentration of 1.0 M (solvent: ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3/7 (volume ratio)) under an environment of 60.degree. The mixture was immersed in a mixed solvent for 3 days in 2 parts by volume of vinylene carbonate as an additive (solvent ratio added)) for swelling. Thereafter, the film piece was pulled up, the surface electrolyte was wiped lightly, and then the mass was measured. The mass of the film piece after swelling is taken as W1.
And electrolyte solution swelling degree was computed using the following formula.
Electrolyte swelling degree (% by mass) = {(W1−W0) / W0} × 100
<Glass transition temperature>
The aqueous dispersion containing the particulate polymer was dried for 3 days in an environment with a humidity of 50% and a temperature of 23 to 26 ° C. to form a film having a thickness of 1 ± 0.3 mm. The formed film was dried in a vacuum dryer at a temperature of 60 ° C. for 10 hours. Thereafter, using a dried film as a sample, a differential scanning calorimeter (manufactured by Nano Technology, DSC 6220 SII) under the conditions of a measurement temperature of −100 ° C. to 180 ° C. and a temperature rising rate of 5 ° C./minute according to JIS K7121. The glass transition temperature Tg (° C.) was measured using
<Gel content>
The aqueous dispersion containing the particulate polymer was dried in an environment with a humidity of 50% and a temperature of 23 to 25 ° C. to form a film having a thickness of 1 ± 0.3 mm. The formed film was dried in a vacuum dryer at a temperature of 60 ° C. for 10 hours. Thereafter, the dried film was cut into 3 to 5 mm squares, and approximately 1 g was precisely weighed. The mass of the film piece obtained by cutting is set to w0. The film pieces were immersed in 50 g of tetrahydrofuran (THF) for 24 hours. Then, the film piece pulled up from THF was vacuum-dried at a temperature of 105 ° C. for 3 hours, and the mass w1 of the insoluble matter was measured.
And gel content was computed using the following formula.
Gel content (mass%) = (w1 / w0) × 100
<Stability of Slurry Composition>
The prepared slurry composition was placed in a sealed plastic container and left for 3 days under a temperature of 25 ± 2 ° C. After that, the lower part of the slurry composition was palpated to confirm the presence or absence of settling of solids on the bottom of the container. The absence of sediment indicates that the stability of the slurry composition is high.
<Productivity of electrode>
The solid content concentration of the slurry composition prepared to have a viscosity of 1100 ± 100 mPa · s (measured with a B-type viscometer at 12 rpm) was evaluated based on the following criteria. It indicates that the higher the solid content concentration of the slurry composition, the easier the drying of the slurry composition and the higher the productivity.
A: Solid content concentration 40 mass% or more B: Solid content concentration 35 mass% or more and less than 40 mass% C: Solid content concentration 25 mass% or more and less than 35 mass% D: Solid content concentration less than 25 mass% Cycle characteristics of ion secondary battery>
The prepared lithium ion secondary battery was allowed to stand at a temperature of 25 ° C. for 5 hours after pouring the electrolyte. Next, charging was performed to a cell voltage of 3.65 V by a constant current method at a temperature of 25 ° C. and 0.2 C, and then aging was performed at a temperature of 60 ° C. for 12 hours. Then, the cell was discharged to a cell voltage of 2.75 V by a constant current method at a temperature of 25 ° C. and 0.2C. After that, CC-CV charging (upper limit cell voltage 4.20 V) was performed by a constant current method of 0.2 C, and CC discharge was performed to 3.00 V by a constant current method of 0.2 C.
Next, it was discharged to a cell voltage of 2.75 V by a constant current method at a temperature of 25 ° C. and 0.1C. Thereafter, charge and discharge operations were performed 100 cycles at a charge and discharge rate of 4.20 to 3.00 V and 0.5 C under an environment of a temperature of 45 ° C. Then, the capacity of the first cycle, that is, the initial discharge capacity X1 and the discharge capacity X2 at the 50th cycle are measured, and the capacity change rate represented by ΔC ′ = (X2 / X1) × 100 (%) is determined. It was evaluated according to the criteria of The larger the value of the rate of change in capacitance ΔC ′, the better the cycle characteristics.
A: ΔC ′ is 85% or more B: ΔC ′ is 83% or more and less than 85% C: ΔC ′ is 80% or more and less than 83% D: ΔC ′ is less than 80% <storage stability of lithium ion secondary battery>
The prepared lithium ion secondary battery was allowed to stand at a temperature of 25 ° C. for 5 hours after pouring the electrolyte. Next, the cell was charged to a cell voltage of 3.65 V by a constant current method at a temperature of 25 ° C. and 0.2 C, and then aging treatment was performed at a temperature of 60 ° C. for 12 hours. Then, the cell was discharged to a cell voltage of 2.75 V by a constant current method at a temperature of 25 ° C. and 0.2C. Thereafter, CC-CV charging (upper limit cell voltage 4.20 V) was performed by a constant current method of 0.2 C, and CC discharge was performed to a cell voltage of 3.00 V by a constant current method of 0.2 C.
Next, the cell volume (V0) of the lithium ion secondary battery was calculated by the Archimedes method. Thereafter, the cell voltage is charged to 4.20 V by a constant current method at a temperature of 25 ° C. and 0.2 C, and left for 3 days under conditions of a temperature of 80 ± 2 ° C. Thereafter, a constant current method at a temperature of 25 ° C. and 0.2 C The cell voltage was discharged to 2.75V. Thereafter, the volume (V1) of the cell was measured, the amount of generated gas was calculated by the following formula, and evaluated by the following criteria. The smaller the gas generation amount, the better the high temperature storage characteristics.
Gas generation amount (mL) = V1 (mL)-V0 (mL)
A: The amount of gas generation is less than 4 mL B: The amount of gas generation is 4 mL or more and less than 5 mL C: The amount of gas generation is 5 mL or more and less than 6 mL D: The amount of gas generation is 6 mL or more

Example 1
<Preparation of an aqueous solution containing a copolymer>
In a 1 L flask equipped with a septum, 720 g of ion exchanged water was charged, the temperature was raised to 40 ° C., and the inside of the flask was replaced with nitrogen gas at a flow rate of 100 mL / min. Next, 10 g of ion-exchanged water, 47.5 g of an 80% aqueous solution of acrylic acid as an ethylenically unsaturated carboxylic acid compound, polyethylene glycol diacrylate as a polyfunctional compound (manufactured by Kyoeisha Chemical Co., Ltd., light acrylate 9EG- A, n = 9 corresponding to compound (I), functional group = 2) 2.0 g and ethoxylated pentaerythritol tetraacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., ATM-35E, n1 + n2 + n3 + n4 = 35 compound (V) Correspondingly, the functional number = 4) and 0.4 g were mixed and injected into the flask by a syringe. Thereafter, 8.0 g of a 2.5% aqueous solution of potassium persulfate as a polymerization initiator was added to the flask by a syringe. Further, after 15 minutes, 40 g of a 2.0% aqueous solution of tetramethylethylenediamine as a polymerization accelerator was added by a syringe. After 4 hours, 4.0 g of a 2.5% aqueous solution of potassium persulfate as a polymerization initiator was added to the flask, and 20 g of a 2.0% aqueous solution of tetramethylethylenediamine as a polymerization accelerator was further added, and the temperature was The temperature was raised to 60.degree. C. to proceed the polymerization reaction. After 3 hours, the flask was vented to air to terminate the polymerization reaction and the product deodorized at a temperature of 80 ° C. to remove residual monomer.
Thereafter, the pH of the product was adjusted to 8 using a 10% aqueous solution of lithium hydroxide to obtain an aqueous solution containing copolymer A. And the electrolyte solution swelling degree of the copolymer A was measured. The results are shown in Table 1.
Preparation of Slurry Composition for Lithium Ion Secondary Battery Anode
An aqueous solution containing a negative electrode active material consisting of a mixture of 90 parts of artificial graphite which is a carbon-based negative electrode active material and 10 parts of SiO _X which is a silicon-based active material and a copolymer A as a binder composition in a planetary mixer A concentration of 4.5% was added to 3.0 parts of the solid equivalent, and the mixture was further diluted with ion-exchanged water to a solid concentration of 60%. Thereafter, the mixture was kneaded at a rotational speed of 40 rpm for 60 minutes to obtain a paste-like slurry. Furthermore, 80 parts of ion-exchanged water was added so that the viscosity was 1100 ± 100 mPa · s (measured with a B-type viscometer, 12 rpm), to prepare a slurry composition for lithium ion secondary battery negative electrode. In addition, solid content concentration of the slurry composition at this time was 42 mass%. And the stability of the slurry composition was evaluated. The results are shown in Table 1.
<Production of Negative Electrode for Lithium Ion Secondary Battery>
The above-mentioned slurry composition for lithium ion secondary battery negative electrodes is applied by a comma coater so that the amount of application is 8.8 to 9.2 mg / cm ^{2 on} the surface of a 20 μm thick copper foil as a current collector. It applied. The copper foil coated with the slurry composition for lithium ion secondary battery negative electrode is transported at a speed of 200 mm / min for 2 minutes in an oven at a temperature of 80 ° C. and for 2 minutes in an oven at a temperature of 120 ° C. Thus, the slurry composition on the copper foil was dried to obtain a negative electrode original fabric.
Then, the obtained negative electrode material sheet is pressed by a roll press so that the density is 1.63 to 1.67 g / cm ^3, and further, under the vacuum condition, for the purpose of removing water and further promoting crosslinking. The resultant was placed in an environment of 105 ° C. for 4 hours to obtain a negative electrode.
<Manufacture of positive electrode for lithium ion secondary battery>
In a planetary mixer, 100 parts of LiCoO ₂ as a positive electrode active material, 2 parts of acetylene black as a conductive material (manufactured by Denki Kagaku Kogyo Co., Ltd., HS-100), PVDF (polyvinylidene fluoride, as a binder) 2.) 2 parts of Kleha Chemical, KF-1100) is added, and 2-methyl pyrirodone as a dispersion medium is further added and mixed so that the total solid concentration becomes 67%, for lithium ion secondary battery positive electrode A slurry composition was prepared.
The obtained slurry composition for a lithium ion secondary battery positive electrode is coated on a 20 μm thick aluminum foil as a current collector with a comma coater so that the coating amount is 25.3 to 25.8 mg / cm ² Applied to Thereafter, the aluminum foil to which the slurry composition for lithium ion secondary battery positive electrode was applied was dried by transporting it in an oven at a temperature of 60 ° C. for 2 minutes at a speed of 0.5 m / min. Then, it heat-processed at the temperature of 120 degreeC for 2 minutes, and obtained the positive electrode original fabric.
Then, the obtained positive electrode material sheet is pressed by a roll press so that the density is 3.40 to 3.50 g / cm ^3, and further, for the purpose of removing water, the temperature is 120 ° C. under vacuum conditions. Placed in the environment for 3 hours to obtain a positive electrode.
<Manufacturing of lithium ion secondary battery>
A wound cell was produced using a single-layer polypropylene separator, the above-mentioned negative electrode and positive electrode, and placed in an aluminum packaging material. Thereafter, a 1.0 M LiPF ₆ solution (the solvent is a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3/7 (volume ratio) as an electrolytic solution, and 2 vol% of vinylene carbonate as an additive (solvent Filled). Furthermore, in order to seal the opening of the aluminum packaging material, heat sealing was performed at a temperature of 150 ° C. to close the aluminum packaging material, and a lithium ion secondary battery was manufactured. Then, the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Examples 2 to 4)
An aqueous solution containing a copolymer prepared in the same manner as copolymer A except that the monomers shown in Table 1 were used in the amounts shown in Table 1 was used as a binder composition except that an aqueous solution containing the copolymer was used as a binder composition. A slurry composition for lithium ion secondary battery negative electrode, a lithium ion secondary battery negative electrode, a lithium ion secondary battery positive electrode, and a lithium ion secondary battery were manufactured. In addition, the methyl methacrylate used in Example 2 is corresponded to the compound (other compound) which can adjust the magnitude | size of the solubility parameter (SP value) of a copolymer.
Then, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Example 5)
An aqueous solution containing a copolymer, a lithium ion solution, in the same manner as in Example 3, except that a 10% aqueous solution of lithium hydroxide was used instead of a 10% aqueous solution of lithium hydroxide to prepare an aqueous solution containing a copolymer. The slurry composition for secondary battery negative electrodes, the negative electrode for lithium ion secondary batteries, the positive electrode for lithium ion secondary batteries, and the lithium ion secondary battery were manufactured.
Then, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Examples 6 to 9)
An aqueous solution containing a copolymer prepared in the same manner as copolymer A except that the monomers shown in Table 1 were used in the amounts shown in Table 1 was used as a binder composition except that an aqueous solution containing the copolymer was used as a binder composition. A slurry composition for lithium ion secondary battery negative electrode, a lithium ion secondary battery negative electrode, a lithium ion secondary battery positive electrode, and a lithium ion secondary battery were manufactured.
Then, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Example 10)
An aqueous solution containing Copolymer B was prepared in the same manner as Copolymer A, except that the monomers shown in Table 1 were used in the amounts shown in Table 1. Moreover, the water dispersion liquid of the particulate-form polymer which consists of a styrene butadiene copolymer was prepared as follows.
And when preparing the slurry composition for lithium ion secondary battery negative electrodes, it changes to the aqueous solution containing the copolymer A, and the aqueous solution (solid content concentration: 4.5%) containing the copolymer B is 3 in solid content equivalent. Lithium ion secondary battery negative electrode in the same manner as in Example 1 except that 0 parts and an aqueous dispersion of a particulate polymer consisting of a styrene-butadiene copolymer was used in an amount of 0.3 parts in terms of solid content A slurry composition, a negative electrode for a lithium ion secondary battery, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery were manufactured.
Further, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.
<Preparation of Aqueous Dispersion of Particulate Polymer Composed of Styrene-Butadiene Copolymer>
65 parts of styrene, 35 parts of 1,3-butadiene, 2 parts of itaconic acid, 1 part of 2-hydroxyethyl acrylate, 0.3 parts of t-dodecyl mercaptan as a molecular weight modifier, dodecyl as an emulsifier in a 5 MPa pressure resistant container with a stirrer After 5 parts of sodium benzenesulfonate, 150 parts of ion exchange water as a solvent, and 1 part of potassium persulfate as a polymerization initiator were added and sufficiently stirred, the temperature was raised to 55 ° C. to start polymerization. .
The reaction was stopped by cooling when monomer consumption was 95.0%. A 5% aqueous solution of sodium hydroxide was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. Thereafter, unreacted monomers were removed by heating under reduced pressure. Thereafter, the temperature was lowered to 30 ° C. or lower to obtain an aqueous dispersion containing a particulate polymer comprising a styrene-butadiene copolymer. The gel content of the styrene-butadiene copolymer was 92% by mass, and the glass transition temperature (Tg) was 10 ° C.

(Example 11)
An example of using an aqueous dispersion of a particulate polymer consisting of a styrene butadiene acrylonitrile copolymer prepared as described below in place of the aqueous dispersion of a particulate polymer consisting of a styrene-butadiene copolymer Similarly to 10, a slurry composition for lithium ion secondary battery negative electrode, a lithium ion secondary battery negative electrode, a lithium ion secondary battery positive electrode and a lithium ion secondary battery were manufactured.
Further, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.
<Preparation of Aqueous Dispersion of Particulate Polymer Consisting of Styrene Butadiene Acrylonitrile Copolymer>
In a 5 MPa pressure-resistant container equipped with a stirrer, 35 parts of acrylonitrile, 65 parts of 1,3-butadiene, 0.3 parts of t-dodecyl mercaptan as a molecular weight modifier, 5 parts of sodium dodecylbenzene sulfonate as an emulsifier, ion exchanged water as a solvent After 150 parts of the reaction and 1 part of potassium persulfate as a polymerization initiator were charged and sufficiently stirred, the temperature was raised to 55 ° C. to start polymerization of the polymer to be the core portion.
27 parts of styrene, 15 parts of 1,3-butadiene, 16 parts of acrylonitrile, 1 part of acrylic acid, 2 parts of itaconic acid, molecular weight modifier, prepared in advance when the monomer consumption amounted to 80.0% Aqueous dispersion of 0.3 part of t-dodecyl mercaptan as a component, 5 parts of sodium dodecyl benzene sulfonate as an emulsifier, 150 parts of ion exchanged water as a solvent, and 1 part of potassium persulfate as a polymerization initiator The polymer was further charged to polymerize the polymer to be a shell portion, and was cooled to stop the reaction when the total monomer consumption was 95.0%. A 5% aqueous solution of sodium hydroxide was added to the aqueous dispersion containing the polymer thus obtained to adjust the pH to 8. Thereafter, unreacted monomers were removed by heating under reduced pressure. Thereafter, the temperature was lowered to 30 ° C. or lower to obtain an aqueous dispersion containing a particulate polymer composed of a styrene butadiene acrylonitrile copolymer. The gel content of the styrene butadiene acrylonitrile copolymer was 75% by mass, the glass transition temperature (Tg) of the core was -37 ° C., and the glass transition temperature (Tg) of the shell was 35 ° C. .

(Example 12)
Example 10 is the same as Example 10 except that instead of the aqueous dispersion of the particulate polymer consisting of a styrene-butadiene copolymer, an aqueous dispersion of a particulate polymer consisting of an acrylic polymer prepared as follows is used. Thus, a slurry composition for lithium ion secondary battery negative electrode, a lithium ion secondary battery negative electrode, a lithium ion secondary battery positive electrode and a lithium ion secondary battery were manufactured.
Further, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.
<Preparation of Aqueous Dispersion of Particulate Polymer Composed of Acrylic Polymer>
In a 5 MPa pressure resistant container with stirrer, 82 parts of butyl acrylate, 2 parts of acrylonitrile, 2 parts of methacrylic acid, 1 part of N-methylol acrylamide, 1 part of allyl glycidyl ether, 4 parts of sodium lauryl sulfate as an emulsifier, ion exchanged water 150 as a solvent A part and 0.5 parts of ammonium persulfate as a polymerization initiator were charged and sufficiently stirred, and then heated to a temperature of 80 ° C. to initiate polymerization.
The reaction was stopped by cooling when the monomer consumption amounted to 96.0%. A 5% aqueous solution of sodium hydroxide was added to the aqueous dispersion containing the acrylic polymer thus obtained to adjust the pH to 7. Thereafter, unreacted monomers were removed by heating under reduced pressure. Thereafter, the temperature was lowered to 30 ° C. or lower to obtain an aqueous dispersion containing a particulate polymer comprising an acrylic polymer. In addition, gel content of the acrylic polymer was 90 mass%, and glass transition temperature (Tg) was -50 degreeC.

(Example 13)
A slurry composition for a lithium ion secondary battery negative electrode, a negative electrode for a lithium ion secondary battery, a lithium ion secondary battery, in the same manner as in Example 10 except that the aqueous solution containing the copolymer A was used instead of the aqueous solution containing the copolymer B. A positive electrode for an ion secondary battery and a lithium ion secondary battery were manufactured.
Further, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Example 14)
At the time of preparation of the slurry composition for lithium ion secondary battery negative electrode, the compounding quantity of the aqueous solution (solid content concentration: 4.5%) containing the copolymer A is 1.5 parts in solid content equivalent, and it is carboxy as a thickener A slurry composition for a lithium ion secondary battery negative electrode, a negative electrode for a lithium ion secondary battery, in the same manner as in Example 1 except that 1.5 parts of a methylcellulose aqueous solution (manufactured by Nippon Paper Chemicals Co., Ltd., MAC 800 LC) was blended. A positive electrode for a lithium ion secondary battery and a lithium ion secondary battery were manufactured.
Further, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Comparative example 1)
In the same manner as in Example 1, except that a 1% aqueous solution of polyacrylic acid (manufactured by Aldrich, molecular weight = 12,250) was adjusted to pH 8 with an aqueous solution of lithium hydroxide was used instead of the aqueous solution containing copolymer A. The slurry composition for lithium ion secondary battery negative electrodes, the negative electrode for lithium ion secondary batteries, the positive electrode for lithium ion secondary batteries, and the lithium ion secondary battery were manufactured.
Then, in the same manner as Example 1, the electrolyte swelling degree of polyacrylic acid, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Comparative example 2)
An aqueous solution containing a copolymer prepared in the same manner as copolymer A except that the monomers shown in Table 1 were used in the amounts shown in Table 1 was used as a binder composition except that an aqueous solution containing the copolymer was used as a binder composition. A slurry composition for lithium ion secondary battery negative electrode, a lithium ion secondary battery negative electrode, a lithium ion secondary battery positive electrode, and a lithium ion secondary battery were manufactured. The pentaerythritol tetraacrylate used in Comparative Example 2 corresponds to a compound having two or more ethylenic unsaturated bonds and having no polyoxyalkylene structure.
Then, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Comparative examples 3 to 4)
An aqueous solution containing a copolymer prepared in the same manner as copolymer A except that the monomers shown in Table 1 were used in the amounts shown in Table 1 was used as a binder composition except that an aqueous solution containing the copolymer was used as a binder composition. A slurry composition for lithium ion secondary battery negative electrode, a lithium ion secondary battery negative electrode, a lithium ion secondary battery positive electrode, and a lithium ion secondary battery were manufactured.
Then, in the same manner as in Example 1, the electrolyte solution swelling degree of the copolymer, the stability of the slurry composition, the productivity of the electrode, and the cycle characteristics and storage stability of the lithium ion secondary battery were evaluated. The results are shown in Table 1.

In Table 1 below,
"AA" indicates acrylic acid,
"PEGDA" indicates polyethylene glycol diacrylate,
"EPETA" refers to ethoxylated pentaerythritol tetraacrylate,
"MMA" indicates methyl methacrylate
"PETA" indicates pentaerythritol tetraacrylate.

From Examples 1 to 14 and Comparative Examples 1 to 4 in Table 1, in Examples 1 to 14, the cycle characteristics excellent for lithium ion secondary batteries and the stability of the slurry composition and the productivity of the electrode are ensured. It can be seen that high temperature storage characteristics can be exhibited.
In addition, according to Examples 1 to 4 and 6 to 9 of Table 1, the slurry composition can be stabilized by adjusting the blending amount of the monomer when preparing the copolymer and the electrolytic solution swelling degree of the copolymer. It can be seen that it is possible to simultaneously achieve high levels of the properties, productivity of the electrode, and cycle characteristics and high temperature storage characteristics of the lithium ion secondary battery.
Furthermore, according to Examples 3 and 5 of Table 1, by using a lithium hydroxide aqueous solution at the time of neutralization of the aqueous solution containing the copolymer, by using a copolymer having a carboxylic acid lithium base, lithium ion secondary battery It can be seen that high temperature storage characteristics can be improved.
Moreover, it turns out that the cycling characteristics and high temperature storage characteristic of a lithium ion secondary battery can be improved from Example 2 and 10-13 of Table 1 by using a copolymer and a particulate-form polymer together.
Example 14 is an example in which carboxymethyl cellulose having high thixotropy and capable of improving the stability of the slurry composition at low cost is used in combination with the copolymer. And from Table 1, when high stability of a slurry composition is required etc., it turns out that lithium ion secondary batteries can be made to exhibit high performance by using a copolymer and carboxymethylcellulose together.

According to the binder composition for a lithium ion secondary battery of the present invention, it is possible to exhibit excellent cycle characteristics and high temperature storage characteristics in a lithium ion secondary battery while securing the stability of the slurry composition and the productivity of the electrode. Can.
Moreover, according to the slurry composition for lithium ion secondary battery electrodes of this invention, the cycle characteristic and high temperature storage characteristic excellent in the lithium ion secondary battery can be exhibited, ensuring productivity of an electrode.
Furthermore, according to the slurry composition for a lithium ion secondary battery porous film of the present invention, it is possible to exhibit excellent cycle characteristics and high temperature storage characteristics in a lithium ion secondary battery.
Furthermore, according to the electrode for a lithium ion secondary battery of the present invention, it is possible to exhibit excellent cycle characteristics and high temperature storage characteristics in a lithium ion secondary battery.
And according to the present invention, a lithium ion secondary battery excellent in cycle characteristics and high temperature storage characteristics can be provided.

Claims (9)

An ethylenically unsaturated carboxylic acid compound comprising at least one of an ethylenically unsaturated carboxylic acid and a salt thereof;
And a copolymer obtained by polymerizing a monomer composition containing a polyoxyalkylene structure and a polyfunctional compound having two or more ethylenic unsaturated bonds,
In the monomer composition, the ratio of the ethylenically unsaturated carboxylic acid compound in all the monomers is 70.0% by mass to 99.9% by mass, and the polyfunctional compound in all the monomers der ratio less 30.0 mass% 0.1 mass% of is,
The co electrolyte swelling degree of the polymer Ru der 120 wt% 28 wt% or more, the lithium ion secondary battery binder composition.   The binder composition for a lithium ion secondary battery according to claim 1, wherein the copolymer comprises lithium carboxylate.   The binder composition for lithium ion secondary batteries of Claim 1 or 2 whose electrolyte solution swelling degree of the said copolymer is 50 mass% or less.   The slurry composition for lithium ion secondary battery electrodes containing the binder composition for lithium ion secondary batteries as described in any one of Claims 1-3, and an electrode active material.   The slurry composition for lithium ion secondary battery electrodes of Claim 4 whose said electrode active material is Si containing material.   The electrode for lithium ion secondary batteries provided with the electrode mixture layer prepared using the slurry composition for lithium ion secondary battery electrodes of Claim 4 or 5 on a collector. Equipped with a positive electrode, a negative electrode, an electrolyte and a separator,
A lithium ion secondary battery, wherein at least one of the positive electrode and the negative electrode is an electrode for a lithium ion secondary battery according to claim 6.   The slurry composition for lithium ion secondary battery porous films containing the binder composition for lithium ion secondary batteries as described in any one of Claims 1-3, and nonelectroconductive particle. Equipped with a positive electrode, a negative electrode, an electrolyte and a separator,
A lithium ion secondary battery comprising a porous film formed by using the slurry composition for a lithium ion secondary battery porous film according to claim 8, at least one of the positive electrode, the negative electrode, and the separator.