KR20160138960A - Binder composition for lithium-ion secondary battery electrodes, slurry composition for lithium-ion secondary battery electrodes, lithium-ion secondary battery electrode, and lithium-ion secondary battery - Google Patents

Abstract

An object of the present invention is to provide a binder composition for a lithium ion secondary battery electrode which is capable of producing a lithium ion secondary battery having a low internal resistance and excellent both in productivity and tackiness. The binder composition for an electrode of a lithium ion secondary battery of the present invention comprises 10 to 80 mass% of a lithium salt of an unsaturated acid (monomer a), 5 to 40 mass% of an unsaturated acid (monomer b), and an alpha, beta -unsaturated nitrile ) And 10 to 85% by mass of a polymer obtained by polymerizing a monomer composition, and a dispersion medium.

Description

FIELD OF THE INVENTION The present invention relates to a binder composition for a lithium ion secondary battery electrode, a slurry composition for a lithium ion secondary battery electrode, an electrode for a lithium ion secondary battery, and a lithium ion secondary battery, LITHIUM-ION SECONDARY BATTERY ELECTRODE, AND LITHIUM-ION SECONDARY BATTERY}

The present invention relates to a binder composition for a lithium ion secondary battery electrode, a slurry composition for a lithium ion secondary battery electrode, an electrode for a lithium ion secondary battery, and a lithium ion secondary battery.

Lithium ion secondary batteries are small and light in weight, have high energy density and are capable of repeated charging and discharging, and are used in a wide range of applications. Therefore, in recent years, improvement of battery members such as electrodes has been studied for the purpose of further enhancing the performance of lithium ion secondary batteries.

Here, the electrode for a lithium ion secondary battery generally comprises a current collector and an electrode composite layer formed on the current collector. The electrode composite layer may be formed by, for example, a binder composition containing a polymer as a binder, a slurry composition obtained by dispersing an electrode active material or the like in a dispersion medium such as an organic solvent or water, and drying the dispersion to dry the electrode active material With a polymer.

Therefore, in order to further improve the performance of the lithium ion secondary battery, improvement of the binder composition or slurry composition used for electrode formation has been attempted.

Specifically, it has been proposed to use a binder composition containing a polymer containing a plurality of monomer units at a specific ratio in the production of an electrode such as a lithium ion battery. For example, Patent Document 1 discloses a resin composition containing 80 to 99.9% by weight of a repeating unit derived from a monomer containing a nitrile group and having a repeating unit derived from an ethylenically unsaturated compound such as a vinyl monomer having a carboxylic acid group in an amount of 0.1 to 20 wt% % Is contained in the binder composition as a binder to improve the stability of the slurry composition prepared using the binder composition and the binder composition and to improve the cycle characteristics of the secondary battery produced using the binder composition It is reported that it can be done.

Patent Document 1: International Publication No. 2012/091001

However, in the synthesis of the polymer contained in the conventional binder composition, a large amount of polymerization reaction product precipitates during the polymerization reaction due to the use of a monomer containing a nitrile group, and the polymerization reaction tends to stop at an early stage have. Therefore, the conversion rate (polymerization conversion rate) of the monomer to the polymer is as high as 70%, which is high, the cost of the material is high, and a manufacturing problem in which post treatment for removing residual monomers (for example, filtration treatment) there was.

In addition, in the above-mentioned conventional binder composition, there is another manufacturing problem that when the blending amount of the vinyl monomer having a carboxylic acid group is increased in order to improve the binding property as a polymer, polymerization reaction products aggregate during the polymerization reaction.

Further, there is room for improvement in that the conventional binder composition has a high internal resistance of the lithium ion secondary battery produced by using the binder composition.

Therefore, it is an object of the present invention to provide a binder composition for a lithium ion secondary battery electrode which is capable of producing a lithium ion secondary battery having a low internal resistance and excellent both in productivity and tackiness. Another object of the present invention is to provide a lithium ion secondary battery electrode slurry composition capable of preparing an electrode for a lithium ion secondary battery having a low internal resistance and an excellent peak strength. It is another object of the present invention to provide an electrode for a lithium ion secondary battery having a low internal resistance and an excellent fill strength.

It is another object of the present invention to provide a lithium ion secondary battery having a low internal resistance.

Means for Solving the Problems The present inventors have conducted intensive studies for the purpose of solving the above problems. The present inventors have found that a polymer obtained by polymerizing a monomer comprising a specific compound at a specific ratio has high binding property and can be prepared with high productivity and can reduce the internal resistance when used in the production of a lithium ion secondary battery And completed the present invention.

That is, the present invention aims at solving the above problems advantageously. The binder composition for a lithium ion secondary battery electrode of the present invention comprises 10 to 80% by mass of a lithium salt of an unsaturated acid (monomer a) A polymer obtained by polymerizing a monomer composition comprising 5 to 40% by mass of a monomer b) and 10 to 85% by mass of an alpha, beta -unsaturated nitrile (monomer c), and a dispersion medium. Thus, by polymerizing the lithium salt (unsaturated acid a), unsaturated acid (monomer b) and alpha, beta -unsaturated nitrile (monomer c) of unsaturated acid in a predetermined ratio, a polymer having high binding property and the polymer The binder composition for a lithium ion secondary battery electrode can be prepared with high productivity. According to the binder composition containing the polymer, a lithium ion secondary battery having a low internal resistance can be produced.

Here, in the binder composition for a lithium ion secondary battery electrode of the present invention, it is preferable that the?,? - unsaturated nitrile (monomer c) is acrylonitrile. This is because when the?,? - unsaturated nitrile (monomer c) is acrylonitrile, the mechanical strength and oxidation resistance of the obtained polymer can be improved.

The present invention is also intended to solve the above problems advantageously, and the slurry composition for a lithium ion secondary battery electrode of the present invention is characterized by including the above-described binder composition for an electrode for lithium ion secondary batteries and an electrode active material . As described above, according to the slurry composition for a lithium ion secondary battery electrode comprising the binder composition for a lithium ion secondary battery electrode described above, it is possible to prepare an electrode for a lithium ion secondary battery having excellent peel strength and low internal resistance.

The slurry composition for a lithium ion secondary battery electrode of the present invention preferably further comprises a polymer other than the above-mentioned polymer. This is because by incorporating a polymer other than the polymer described above into the slurry composition for a lithium ion secondary battery electrode, the adhesion between the electrode composite layer and the current collector and the output characteristics of the resulting lithium ion secondary battery can be improved.

Further, in the slurry composition for a lithium ion secondary battery electrode of the present invention, it is preferable that the polymer other than the above-mentioned polymer is a fluorine-containing polymer. By including the fluorine-containing polymer in the slurry composition for a lithium ion secondary battery electrode, the adhesion between the electrode composite layer and the current collector and the output characteristics of the resulting lithium ion secondary battery can be further improved.

The electrode for a lithium ion secondary battery of the present invention is characterized in that the electrode composite layer prepared using the slurry composition for a lithium ion secondary battery electrode described above is provided on a current collector, . Such an electrode for a lithium ion secondary battery has a low internal resistance and an excellent peel strength.

The lithium ion secondary battery of the present invention has 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 a lithium ion secondary battery, And is an electrode for a battery. Such a lithium ion secondary battery has a low internal resistance.

According to the present invention, it is possible to provide a binder composition for a lithium ion secondary battery electrode that can produce a lithium ion secondary battery having a low internal resistance and excellent both in productivity and tackiness. Further, according to the present invention, it is possible to provide a slurry composition for a lithium ion secondary battery electrode capable of preparing an electrode for a lithium ion secondary battery having a low internal resistance and an excellent peak strength. Further, according to the present invention, it is possible to provide an electrode for a lithium ion secondary battery having a low internal resistance and an excellent peak strength.

Further, according to the present invention, a lithium ion secondary battery having a low internal resistance can be provided.

Hereinafter, embodiments of the present invention will be described in detail.

Here, the binder composition for a lithium ion secondary battery electrode of the present invention can be used for preparing a slurry composition for a lithium ion secondary battery electrode. The slurry composition for a lithium ion secondary battery electrode of the present invention is prepared using the binder composition for an electrode for lithium ion secondary batteries of the present invention and an electrode active material, and is used when an electrode of a lithium ion secondary battery is manufactured. In addition, the electrode for a lithium ion secondary battery of the present invention can be manufactured by using the slurry composition for a lithium ion secondary battery electrode of the present invention. Further, the lithium ion secondary battery of the present invention is characterized by using the electrode for a lithium ion secondary battery of the present invention.

(Binder composition for lithium ion secondary battery electrode)

The binder composition for an electrode of a lithium ion secondary battery of the present invention comprises 10 to 80 mass% of a lithium salt of an unsaturated acid (monomer a), 5 to 40 mass% of an unsaturated acid (monomer b), and an alpha, beta -unsaturated nitrile ) And 10 to 85% by mass of a polymer obtained by polymerizing a monomer composition, and a dispersion medium. Further, the binder composition for a lithium ion secondary battery electrode of the present invention may optionally contain other components than the polymer and the dispersion medium.

<Polymer>

The polymer contained in the binder composition for a lithium ion secondary battery electrode of the present invention can be obtained by polymerizing a component (for example, a positive electrode active material, a negative electrode active material Or the like) can be supported so as not to come off from the electrode composite layer.

The polymer contained in the binder composition for a lithium ion secondary battery electrode of the present invention contains a lithium salt of an unsaturated acid (monomer a), an unsaturated acid (monomer b), and an alpha, beta -unsaturated nitrile (monomer c) In a predetermined ratio. In addition, the monomer composition may optionally contain a monomer other than the monomer (hereinafter sometimes referred to as &quot; other monomer &quot;).

In the polymer contained in the binder composition for a lithium ion secondary battery electrode of the present invention, the ratio of the unit derived from the lithium salt of the unsaturated acid (monomer a) and the unit derived from the unsaturated acid (monomer b) Therefore, the lithium ion in the unit derived from the lithium salt of the unsaturated acid is coordinately bonded to a part of the acid group in the unit derived from the unsaturated acid to form a crosslinked structure. The cross-linking structure improves the mechanical strength and electrolyte resistance of the polymer. The polymer thus obtained can exhibit excellent binding properties and can improve the battery characteristics (for example, cycle characteristics and high temperature storage characteristics) of the lithium ion secondary battery when used in the production of the lithium ion secondary battery.

Further, the polymer contained in the binder composition for a lithium ion secondary battery electrode of the present invention contains a unit derived from a lithium salt of an unsaturated acid (monomer a), and thus has excellent lithium ion conductivity. Therefore, when the binder composition containing the polymer is used, the internal resistance of the electrode and the lithium ion secondary battery can be reduced.

In addition, in the synthesis of the polymer contained in the binder composition for a lithium ion secondary battery electrode of the present invention, electrostatic repulsion is caused by the presence of a lithium salt (anion component) derived from a lithium salt of an unsaturated acid (monomer a). Therefore, even when the unsaturated acid (monomer b) is used to increase the binding property of the polymer, aggregation of polymerization reactants during the polymerization reaction can be avoided. In addition, in the synthesis of the polymer, since the lithium salt of the unsaturated acid (monomer a), the unsaturated acid (monomer b) and the alpha, beta -unsaturated nitrile (monomer c) are used in combination as the monomer, Can be inhibited from being precipitated and the conversion of the monomer to the polymer (polymerization conversion rate) can be greatly improved. In view of these points, the binder composition for a lithium ion secondary battery electrode of the present invention containing the above-mentioned polymer and the polymer can easily or unnecessitate a post-treatment for removing residual monomers, It can be prepared at a higher productivity because it can be made more inexpensive. In addition, as is apparent from the above description, it is very important in the present invention that the monomer composition contains the monomer a from the time of polymerization. After the monomer b and the monomer c are polymerized, the unit derived from the monomer b is lithium By chlorinating, the above-mentioned effect can not be obtained.

Hereinafter, each monomer contained in the monomer composition used for preparing the polymer contained in the binder composition for a lithium ion secondary battery electrode of the present invention will be described in detail.

[Lithium salt of unsaturated acid (monomer a)]

The monomer composition requires at least a lithium salt of an unsaturated acid (monomer a).

Here, among the unsaturated acid salts, the lithium salt of the unsaturated acid is used as an essential component. For example, only the other salts such as the sodium salt of the unsaturated acid and the potassium salt of the unsaturated acid are used and the lithium salt of the unsaturated acid is not used , There is a possibility that the obtained polymer may inhibit the movement of lithium ions in the lithium ion secondary battery (for example, insertion into the electrode active material and desorption from the electrode active material). The solubility in an organic solvent tends to be relatively lowered, so that a desired effect (for example, improvement in cell performance, etc.) can not be obtained.

The lithium salt of the unsaturated acid is not particularly limited, and examples thereof include a lithium salt of an unsaturated carboxylic acid, a lithium salt of an unsaturated sulfonic acid, and a lithium salt of an unsaturated phosphonic acid. Of these, as the lithium salt of the unsaturated acid, it is preferable to use a lithium salt of an unsaturated carboxylic acid or a lithium salt of an unsaturated sulfonic acid. Lithium salts of unsaturated carboxylic acids and unsaturated sulfonic acids are easy to obtain, and because of the high polymerization reactivity, the productivity of the binder composition can be further increased by using these lithium salts. In addition, the lithium salt of the unsaturated carboxylic acid and the lithium salt of the unsaturated sulfonic acid have a high degree of dissociation of lithium ions, so that the use of these lithium salts can further reduce the internal resistance of the lithium ion secondary battery.

Examples of the lithium salt of the unsaturated carboxylic acid include lithium salts of?,? - unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; Lithium salts of?,? - unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid; A lithium salt of a partial esterified product of an alpha, beta -unsaturated polycarboxylic acid such as monomethyl maleate or monoethyl itaconate; And lithium salts of unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid and lumenic acid.

Examples of the lithium salt of the unsaturated sulfonic acid include lithium such as vinylsulfonic acid, o-styrenesulfonic acid, m-styrenesulfonic acid, p-styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) Salts, and various substituents thereof.

Examples of the lithium salt of the unsaturated phosphonic acid include lithium salts such as vinylphosphonic acid, o-styrene phosphonic acid, m-styrene phosphonic acid and p-styrene phosphonic acid, and various substituents thereof.

The monomer composition may contain a lithium salt of one kind of unsaturated acid singly or may contain a lithium salt of two or more kinds of unsaturated acids in an optional ratio.

As the lithium salt of the above-mentioned unsaturated acid, lithium acrylate, lithium methacrylate and lithium p-styrenesulfonate are particularly preferable from the viewpoint of further increasing the degree of dissociation of lithium ions and further decreasing the internal resistance of the lithium ion secondary battery.

As the lithium salt of the unsaturated acid, for example, a lithium salt of a commercially available unsaturated acid may be used, and it may be prepared by reacting an unsaturated acid with a basic lithium compound such as lithium hydroxide monohydrate or lithium carbonate Do.

In the present invention, the content of the lithium salt of the unsaturated acid in the monomer composition should be 10 mass% or more, but it is preferably 15 mass% or more. If the content of the lithium salt of the unsaturated acid in the monomer composition is less than 10% by mass, the polymerization stability can not be maintained at a high level, and the polymerization reaction product coagulates during the polymerization reaction, so that it is not possible to prepare the polymer with high productivity . The content of the lithium salt of the unsaturated acid in the monomer composition is required to be 80 mass% or less, preferably 60 mass% or less, and more preferably 50 mass% or less. When the content of the lithium salt of the unsaturated acid in the monomer composition exceeds 80% by mass, sufficient flexibility is not imparted to the obtained polymer and the binding property is lowered, and the electrode prepared using such a polymer is wound to produce a lithium ion secondary battery This may cause breakage of the electrode or the like at the time of manufacturing the battery.

[Unsaturated acid (monomer b)]

Further, the monomer composition needs to contain at least an unsaturated acid (monomer b).

The unsaturated acid is not particularly limited, and examples thereof include an unsaturated carboxylic acid, an unsaturated sulfonic acid, and an unsaturated phosphonic acid. Of these unsaturated acids, unsaturated carboxylic acids and unsaturated sulfonic acids are preferably used. The unsaturated carboxylic acid and unsaturated sulfonic acid are easily available and can improve the binding property of the polymer and further improve the adhesion between the electrode composite layer and the current collector.

Examples of the unsaturated carboxylic acid include an?,? - unsaturated monocarboxylic acid such as acrylic acid, methacrylic acid and crotonic acid; Alpha, beta -unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid; Partial esters of?,? - unsaturated polycarboxylic acids such as monomethyl maleate and monoethyl itaconate; And unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid and lumenic acid.

Examples of the unsaturated sulfonic acid include vinyl sulfonic acid, o-styrenesulfonic acid, m-styrenesulfonic acid, p-styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) .

Examples of the unsaturated phosphonic acid include vinyl phosphonic acid, o-styrene phosphonic acid, m-styrene phosphonic acid, p-styrene phosphonic acid, and various substituents thereof.

The monomer composition may contain one kind of unsaturated acid singly or two or more kinds of unsaturated acids in an arbitrary ratio.

As the above-mentioned unsaturated acid, acrylic acid, methacrylic acid, p-styrenesulfonic acid, p-styrenesulfonic acid and the like are preferably used as the unsaturated acid from the viewpoints of further improving the adhesion between the electrode composite layer and the current collector, And vinylsulfonic acid are preferable, and acrylic acid and methacrylic acid are particularly preferable.

As the unsaturated acid, for example, a commercially available unsaturated acid may be used, and a part of the commercially available unsaturated acid may be substituted with halogen or the like.

In the present invention, the content of the unsaturated acid in the monomer composition is required to be 5% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more. When the content of the unsaturated acid in the monomer composition is less than 5% by mass, the adhesion between the current collector and the electrode composite layer can not be sufficiently improved when the electrode composition for a lithium ion battery is prepared using the binder composition comprising the obtained polymer. The content of the unsaturated acid in the monomer composition is required to be 40 mass% or less, preferably 30 mass% or less, and more preferably 20 mass% or less. If the content of the unsaturated acid in the monomer composition exceeds 40% by mass, aggregation of polymerization reactants can not be effectively prevented during the polymerization reaction. This is because the lithium ion conductivity of the polymer is lowered and the internal resistance of the electrode and the lithium ion secondary battery may rise.

[alpha, beta -unsaturated nitrile (monomer c)]

Further, the monomer composition needs to contain at least an alpha, beta -unsaturated nitrile (monomer c).

The?,? - unsaturated nitrile is not particularly limited and includes acrylonitrile, methacrylonitrile, and various substituents thereof.

The monomer composition may contain one kind of?,? - unsaturated nitrile alone or two or more kinds of?,? - unsaturated nitrile in an arbitrary ratio.

Here, as the above-mentioned?,? - unsaturated nitrile, acrylonitrile or methacrylonitrile is preferable, and acrylonitrile is more preferable from the viewpoint of ensuring a high level of mechanical strength and oxidation resistance of the resulting polymer. By securing a high mechanical strength and oxidation resistance of the polymer, it is possible to exert a favorable binding property to the polymer and to exhibit good battery characteristics (for example, high-temperature cycle characteristics and high-temperature storage characteristics) in a lithium ion secondary battery .

As the?,? - unsaturated nitrile, for example, commercially available?,? - unsaturated nitrile can be used. Also, it is also possible to use a product obtained by substituting a part of such commercially available?,? - unsaturated nitrile with a halogen or the like It is possible.

In the present invention, the content of?,? - unsaturated nitrile in the monomer composition should be 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, 35% by mass or more. If the content of?,? - unsaturated nitrile in the monomer composition is less than 10% by mass, the resulting polymer does not have sufficient mechanical strength and the adhesion between the current collector and the electrode composite layer can not be sufficiently improved. (For example, high-temperature cycle characteristics and high-temperature storage characteristics) may be lowered. The content of?,? - unsaturated nitrile in the monomer composition should be 85 mass% or less, preferably 75 mass% or less, and more preferably 70 mass% or less. If the content of?,? - unsaturated nitrile in the monomer composition exceeds 85% by mass, there is a possibility that a sufficiently high polymerization conversion rate can not be achieved, and the obtained polymer becomes too hard. Using such a polymer, an electrode for a lithium ion secondary battery and lithium This is because it is difficult to manufacture an ion secondary battery.

[Other monomers]

In addition, the monomer composition may optionally include monomers other than the above-mentioned monomers (other monomers). The other monomer is not particularly limited, and for example, a monomer (monomer d) having a glass transition point Tg of the homopolymer lower than room temperature when a homopolymer having a weight average molecular weight of more than 10,000 is formed can be mentioned.

[[Monomer d]]

When the monomer composition contains the monomer d, the flexibility of the obtained polymer can be improved and a high binding property can be ensured.

The monomer composition may contain one kind of monomer d alone or two or more kinds of monomers d in an arbitrary ratio.

Here, if the monomer d is a monomer having a glass transition point Tg of less than room temperature, preferably less than 0 ° C, more preferably less than -20 ° C, when the homopolymer having a weight average molecular weight of more than 10,000 is formed, And is not particularly limited, and examples thereof include (meth) acrylic acid esters. Examples of such (meth) acrylic esters include (meth) acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate and butyl (meth) acrylate.

In the present specification, the term &quot; (meth) acryl &quot; in the (meth) acrylate or the like refers to acryl and / or methacryl.

In the present invention, the content of the monomer d in the monomer composition is preferably 70 mass% or less, more preferably 45 mass% or less, and further preferably 20 mass% or less. When the content of the monomer d is 70 mass% or less, the amount of the unit derived from the lithium salt, the unsaturated acid and the?,? - unsaturated nitrile of the unsaturated acid in the polymer is sufficiently secured, and the desired effect It is because.

[Preparation of Polymer]

The polymer contained in the binder composition for a lithium ion secondary battery electrode of the present invention is not particularly limited, and a monomer composition containing each of the above-mentioned monomers (monomer a, monomer b, monomer c and other monomers) in the above- , For example, in an aqueous solvent.

When the monomer a (lithium salt of an unsaturated acid) is a compound obtained by lithium chloride of the monomer b (unsaturated acid) in the monomer composition, the monomer b is not particularly limited, and the monomer b, the monomer c and optionally other monomers To prepare a monomer composition precursor, and part of the monomer b in the monomer composition precursor is lithium-chlorinated with a basic lithium compound to prepare a monomer composition a. In this case, the content of the monomer b in the monomer composition precursor depends on the amount of the monomer b which becomes lithium chloride to be monomer a and the amount of the monomer b to be contained in the monomer composition, based on the amount of the monomer a and the monomer b desired to be contained in the monomer composition. The sum of the amounts may be used.

Here, the production method of the polymer is not particularly limited, and any of the solution polymerization method, the suspension polymerization method, the bulk polymerization method and the emulsion polymerization method can be used.

As the polymerization method, addition polymerization such as ion polymerization, radical polymerization or living radical polymerization can be used. As the polymerization initiator, a known polymerization initiator can be used.

In the production of the polymer, since the above-mentioned polymer composition is used, the polymerization conversion rate of the monomer can be 90% or more, and inevitably 95% or more. Therefore, since the residual amount of each monomer after the polymerization reaction is greatly reduced, it becomes possible to easily or unnecessitate the post-treatment of the residual monomer, and the material cost becomes lower.

The polymer produced as described above contains units derived from the monomers contained in the monomer composition used in the polymerization in the same ratio as the abundance ratio of each monomer in the monomer composition.

<Dispersion>

The binder composition for a lithium ion secondary battery electrode of the present invention contains a dispersion medium. Here, the dispersion medium may be an aqueous solvent used in producing the polymer or an organic solvent. Specifically, when the dispersion liquid of the polymer obtained by polymerizing the monomer composition in an aqueous solvent is used as the binder composition, the dispersion medium may be an aqueous solvent such as water or an aqueous solution used in the polymerization. Further, for example, when the monomer composition is polymerized in an aqueous solvent, and then the aqueous solvent is replaced with an organic solvent to form a binder composition, an organic solvent may be used. The organic solvent is not particularly limited, and examples thereof include N-methylpyrrolidone (NMP), acetonitrile, acetylpyridine, cyclopentanone, dimethylformamide, dimethylsulfoxide, methylformamide, methylethylketone, furfural, Ethylenediamine and the like. As the dispersion medium, an organic solvent is preferable, and N-methyl pyrrolidone (NMP) is more preferable.

The binder composition for a secondary battery electrode of the present invention may contain one kind of solvent alone or two or more kinds of solvents in an arbitrary ratio as the dispersion medium.

<Other ingredients>

The binder composition for a lithium ion secondary battery electrode of the present invention may contain, in addition to the above-mentioned components, a known optional component that can be compounded in the binder composition. It may also contain residues such as polymerization initiators used for polymerization of the polymer.

(Slurry composition for lithium ion secondary battery electrode)

The slurry composition for a lithium ion secondary battery electrode of the present invention includes the above-described binder composition for an electrode of a lithium ion secondary battery and an electrode active material. In the slurry composition for a lithium ion secondary battery electrode of the present invention, the polymer contained in the slurry composition for a lithium ion secondary battery electrode functions as at least a part of the binder. The use of such a slurry composition for a lithium ion secondary battery electrode can provide an electrode for a lithium ion secondary battery having an excellent fill strength and a low internal resistance, A low lithium ion secondary battery can be provided.

Here, the slurry composition for a lithium ion secondary battery electrode of the present invention may optionally contain a conductive material, a polymer other than the polymer contained in the binder composition, and other optional additives in addition to the above-described binder composition for electrode for a lithium ion secondary battery and the electrode active material May be included.

<Electrode Active Material>

The electrode active material is a substance that exchanges electrons in the electrodes (positive and negative electrodes) of a lithium ion secondary battery. Hereinafter, the electrode active material (positive electrode active material, negative electrode active material) used in the slurry composition for a lithium ion secondary battery electrode of the present invention will be described in detail.

[Positive electrode active material]

The positive electrode active material to be mixed with the slurry composition of the present invention is not particularly limited and a known positive electrode active material used in the positive electrode of a lithium ion secondary battery can be used. Specifically, 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. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.

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 OP ₂ O ₅ , amorphous MoO ₃ , amorphous V ₂ O ₅ , amorphous V ₆ O ₁₃ , and the like.

Examples of transition metal sulfides include TiS ₂ , TiS ₃ , amorphous MoS ₂ , and FeS.

Examples of the composite metal oxide of lithium and a transition metal include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure.

Examples of the lithium-containing composite metal oxide having a layered structure include lithium-containing cobalt oxide (LiCoO ₂ ), lithium-containing nickel oxide (LiNiO ₂ ), lithium-containing complex oxide of Co-Ni-Mn, lithium Containing complex oxide, a lithium-containing complex oxide of Ni-Co-Al, solid solution of LiMaO ₂ and Li ₂ MbO ₃ , and the like. Examples of solid solutions of LiMaO ₂ and Li ₂ MbO ₃ include xLiMaO ₂ (1-x) Li ₂ MbO ₃ and the like. Wherein x represents a number satisfying 0 < x < 1, Ma represents at least one transition metal having an average oxidation state of 3+, and Mb represents at least one transition metal having an average oxidation state of 4+.

In the present specification, the "average oxidation state" refers to the average oxidation state of the above "one or more transition metals" and is calculated from the molar amount of the transition metal and the valence. For example, when "at least one transition metal" 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) + (0.5) x (4+) = 3+.

Examples of the lithium-containing composite metal oxide having a spinel structure include compounds obtained by replacing a part of Mn of lithium manganese oxide (LiMn ₂ O ₄ ) or lithium manganese oxide (LiMn ₂ O ₄ ) with another transition metal have. Specific examples thereof include Li _s [Mn _2-t Mc _t ] O ₄ . Where 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. T represents a number satisfying 0 < t < 1, and s represents a number satisfying 0? S? 1. As the positive electrode active material, a lithium excess spinel compound represented by Li _{1 + x} Mn _{2 - x} O ₄ (0 <X <2) may be used.

Examples of the lithium-containing composite metal oxide having an olivine structure include olivine-type lithium phosphate compounds represented by Li _y MdPO ₄ such as olivine-type iron phosphate lithium (LiFePO ₄ ) and olivine-type manganese phosphate lithium (LiMnPO ₄ ) have. Here, Md represents one or more kinds of transition metals having an average oxidation state of 3+, and examples thereof include Mn, Fe, and Co. Y represents a number satisfying 0? Y? 2. The olivine-type lithium phosphate compound represented by Li _y MdPO ₄ may be partially substituted with another metal having Md. Examples of the substitutable metal include Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, Si, B and Mo.

Among them, lithium-containing cobalt oxide (LiCoO ₂ ), a lithium-containing complex oxide of Co-Ni-Mn, or a lithium-containing complex oxide of Co-Ni-Mn is used as the positive electrode active material from the viewpoint of improving the cycle characteristics and the initial capacity of the secondary battery using the positive electrode formed using the slurry composition. It is preferable to use olivine-type iron phosphate lithium (LiFePO ₄ ).

From the viewpoint of increasing the amount of the lithium ion secondary battery using the positive electrode formed using the slurry composition, it is preferable to use a positive electrode active material containing at least one of Mn and Ni as the positive electrode active material. Specifically, from the viewpoint of high capacity of the lithium ion secondary battery, LiNiO ₂ , LiMn ₂ O ₄ , lithium excess spinel compound, LiMnPO ₄ , Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ , Li [Ni _1/3 Co _{1 / 3} Mn _1/3 ] O ₂ , Li [Ni _{0 . 17} Li _{0 . 2} Co _{0 . 07} Mn _{0 . 56} ] O ₂ , LiNi _{0 . 5} Mn _{1 . 5} O ₄ spinel such as a compound of the desirable, and LiNiO _2, Li-excess to be used as the positive electrode active _{material, Li [Ni 0.5 Co 0.2 Mn} 0.3] O 2, Li [Ni 1/3 Co 1/3 Mn 1/3] O ₂ , Li [Ni _{0 . 17} Li _{0 . 2} Co _{0 . 07} Mn _{0 . 56} ] O ₂ is more preferably used as the positive electrode active material, and it is particularly preferable to use Li [Ni _0.5 Co _0.2 Mn _0.3 ] O ₂ as the positive electrode active material.

The particle size or specific surface area of the positive electrode active material is not particularly limited and can be the same as that of the conventional positive electrode active material.

Here, in the case where the slurry composition for a lithium ion secondary battery electrode of the present invention is used as a positive electrode, the content of the positive electrode active material in the slurry composition is not particularly limited. For example, the content of the positive electrode active material in the slurry composition is preferably 100 parts by mass Is not less than 90 parts by mass nor more than 98 parts by mass. By setting the content of the positive electrode active material within this range, the capacity of the lithium ion secondary battery can be improved while keeping the internal resistance of the positive electrode for the lithium ion secondary battery to an appropriate level.

[Negative electrode active material]

The negative electrode active material to be mixed with the slurry composition of the present invention is not particularly limited and a known negative electrode active material used in the negative electrode of a lithium ion secondary battery can be used. Specifically, as the negative electrode active material, a material capable of absorbing and desorbing lithium is generally used. Examples of the substance capable of intercalating and deintercalating lithium include a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material obtained by combining them.

[[Carbon-based negative electrode active material]]

The carbon-based negative electrode active material refers to an active material having carbon as the main skeleton capable of inserting lithium (also referred to as "dope"). Examples of the carbon-based negative electrode active material include carbonaceous materials and graphite materials.

Examples of the carbonaceous material include easily graphite carbon which easily changes the structure of carbon by the heat treatment temperature or nanocrystalline graphite carbon which has a structure close to the amorphous structure typified by glassy carbon And the like.

As the graphitic carbon, for example, there can be mentioned a carbon material obtained by using tar pitch obtained from petroleum or coal as a raw material. Specific examples thereof include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, and pyrogenic gas-phase grown carbon fibers.

Examples of the non-graphitizable carbon include phenol resin fired bodies, polyacrylonitrile carbon fibers, pseudo-isotropic carbon, furfuryl alcohol resin fired bodies (PFA), hard carbon, and the like.

Examples of the graphite material include graphite (graphite) such as natural graphite and artificial graphite.

[[Metal negative electrode active material]]

Metal-based negative electrode active material is an active material containing a metal, and usually includes an element capable of inserting lithium into its structure, and has a theoretical capacity per unit mass of 500 mAh / g or more when lithium is inserted. Examples of the metal-based active material include a single metal (for example, Ag, Al, Ba, Bi, Cu, Sb, Si, Sn, Sr, Zn, Ti, etc.) and alloys thereof, and their oxides, sulfides, nitrides, silicides, carbides and phosphides.

Among the metal negative electrode active materials, an active material containing silicon (silicon negative electrode active material) is preferable. This is because the capacity of the lithium ion secondary battery can be increased by using the silicon based negative electrode active material.

Examples of the silicon based negative electrode active material include silicon (Si), an alloy containing silicon, a composite material of a Si-containing material and a conductive carbon formed by coating or compounding SiO 2, SiO _x , or Si-containing material with conductive carbon have. These silicon based negative electrode active materials may be used singly or in combination of two or more kinds.

Examples of the alloy containing silicon include alloy compositions containing silicon, transition metals such as aluminum and iron, and rare earth elements such as tin and yttrium.

SiO _x is a compound containing Si and at least one of SiO and SiO ₂ , and x is usually 0.01 or more and less than 2. And SiO _x can be formed, for example, by using a disproportionation reaction of silicon monoxide (SiO 2). Specifically, SiO _x can be prepared by heat-treating SiO in the presence of a polymer such as polyvinyl alcohol optionally to produce silicon and silicon dioxide. Further, the heat treatment can be carried out at a temperature of 900 占 폚 or higher, preferably 1000 占 폚 or higher, in an atmosphere containing SiO 2 and optionally a polymer, and then containing an organic gas and / or a vapor.

Examples of the composite material of the Si-containing material and the conductive carbon include a compound obtained by subjecting SiO and a polymer such as polyvinyl alcohol and optionally a pulverized mixture of a carbon material to heat treatment in an atmosphere containing, for example, an organic gas and / . A method of coating the surface of the SiO particles by chemical vapor deposition using an organic gas or the like, a method of granulating (granulating) the SiO particles and the graphite or the artificial graphite by a mechanochemical method And can also be obtained by a known method.

The particle size or specific surface area of the negative electrode active material is not particularly limited and can be the same as that of the negative electrode active material conventionally used.

Here, when the slurry composition for a lithium ion secondary battery electrode of the present invention is used as a negative electrode, the content of the negative electrode active material in the slurry composition is not particularly limited. For example, the content of the negative electrode active material in the slurry composition is preferably 100 parts by mass Is not less than 90 parts by mass nor more than 98 parts by mass. By setting the content of the negative electrode active material within this range, the capacity of the lithium ion secondary battery can be improved while keeping the internal resistance of the negative electrode for the lithium ion secondary battery to an appropriate level.

<Binder composition>

The above-mentioned polymer contained in the binder composition functions as at least a part of the binder material in the electrode composite layer of the electrode for a lithium ion secondary battery prepared using the slurry composition for a lithium ion secondary battery electrode.

The slurry composition for a lithium ion secondary battery electrode of the present invention is prepared by mixing the above-described binder composition for a lithium ion secondary battery electrode with, for example, 0.1 part by mass or more and 10 parts by mass or less, More preferably 0.5 parts by mass or more and 5 parts by mass or less. By setting the content of the binder composition within this range, it is possible to improve the output characteristics of the lithium ion secondary battery while obtaining a desired effect such as reduction of the internal resistance of the electrode for the lithium ion secondary battery.

&Lt; Conductive material &

The conductive material is for securing electrical contact between the electrode active materials. The conductive material is not particularly limited, and a known conductive material can be used. Specifically, examples of the conductive material for the positive electrode of a lithium ion secondary battery include a conductive carbon material such as acetylene black, Ketchenblack (registered trademark), carbon black, and graphite; Fibers of various metals, foils and the like can be used. Among them, acetylene black, Ketjenblack (registered trademark), carbon black, and the like are used as the conductive material from the viewpoints of improving the electrical contact between the positive electrode active materials and improving the electrical characteristics of the lithium ion secondary battery using the positive electrode formed using the slurry composition. It is preferable to use graphite, and acetylene black and Ketchen Black (registered trademark) are particularly preferably used.

The blending amount of the conductive material in the lithium ion secondary battery positive electrode slurry composition of the present invention is not particularly limited, but is preferably 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the positive electrode active material. If the blend amount of the conductive material is too small, it is not possible to ensure sufficient electrical contact between the electrode active materials, and the electrical characteristics of the lithium ion secondary battery can not be sufficiently secured. On the other hand, if the amount of the conductive material is too large, the stability of the slurry composition is lowered, the density of the electrode composite layer in the electrode is lowered, and the capacity of the lithium ion secondary battery can not be sufficiently increased.

<Other Polymers>

Here, the slurry composition for a lithium ion secondary battery electrode of the present invention contains, as a binder, a polymer other than the polymer (hereinafter sometimes referred to as &quot; other polymer &quot;) in addition to the polymer contained in the binder composition It may be. When the above-mentioned other polymer is included in the slurry composition for a lithium ion secondary battery electrode, the adhesion between the electrode composite layer and the current collector is further improved, and the output characteristics of the resulting secondary battery can be improved.

Other polymers include fluorine-containing polymers, acrylonitrile polymers, and the like. Examples of the fluorine-containing polymer include a polymer containing 30% by mass or more of vinylidene fluoride units, for example, polyvinylidene fluoride, and the acrylonitrile polymer preferably contains an acrylonitrile unit in an amount of more than 85% Polymers, such as polyacrylonitrile. Of these, the fluorine-containing polymer is more preferable from the viewpoint of further improving the adhesion between the electrode composite layer and the current collector and further improving the output characteristics of the lithium ion secondary battery.

In the case where the slurry composition for a lithium ion secondary battery electrode of the present invention contains a polymer (other polymer) other than the polymer contained in the above-mentioned binder composition, the content of the other polymer is not particularly limited, Is preferably 10% by mass or more and 90% by mass or less, and more preferably 20% by mass or more and 80% by mass or less, based on the solids content and the total amount of the other polymer. By setting the content of the other polymer in this range, the adhesion between the electrode composite layer and the current collector can be further improved, and the output characteristics of the lithium ion secondary battery can be further improved.

<Other additives>

The slurry composition for a lithium ion secondary battery electrode of the present invention may contain, in addition to the above components, a component such as a viscosity adjuster such as a reinforcing material, an antioxidant or a thickener, a surfactant, a dispersant, or an electrolyte additive having a function of suppressing the decomposition of an electrolyte May be contained. These other additives may be those known in the art, for example, those described in International Publication No. 2012/036260, and those described in Japanese Patent Laid-Open Publication No. 2012-204303.

<Preparation of slurry composition for lithium ion secondary battery electrode>

The slurry composition for a lithium ion secondary battery electrode of the present invention can be prepared by dissolving or dispersing the respective components in an organic solvent. Specifically, each of the components and the organic solvent are mixed using a mixer such as a ball mill, a sand mill, a bead mill, a pigment disperser, a brain ball, an ultrasonic disperser, a homogenizer, a planetary mixer, Can be prepared.

As the organic solvent, the organic solvent contained in the binder composition may be used as it is, or an organic solvent may be added at the time of preparing the slurry composition. The mixing of the components and the organic solvent may be carried out usually at room temperature to 80 ° C for 10 minutes to several hours.

(Electrode for Lithium Ion Secondary Battery)

The electrode for a lithium ion secondary battery of the present invention is provided with an electrode composite layer prepared using the slurry composition for a lithium ion secondary battery electrode obtained as described above on a current collector and includes at least an electrode active material, Lt; / RTI &gt; polymer. Each component such as the electrode active material contained in the electrode composite layer was contained in the slurry composition for lithium ion secondary battery electrode of the present invention and the proportional proportion of each component thereof was measured for the lithium ion secondary battery electrode Is the same as that of each component in the slurry composition. Since the electrode for a lithium ion secondary battery of the present invention uses the binder composition of the present invention, it has a high peak strength and a low internal resistance.

&Lt; Preparation of electrode for lithium ion secondary battery >

The electrode for a lithium ion secondary battery of the present invention can be produced by, for example, applying a slurry composition for a lithium ion secondary battery electrode obtained as described above to a current collector and forming a slurry composition for a lithium ion secondary battery electrode Dried. That is, the electrode for a lithium ion secondary battery is obtained, for example, by a coating step of the slurry composition and a drying step of the slurry composition.

[Application step]

The method of applying the slurry composition for a lithium ion secondary battery electrode onto a current collector is not particularly limited and a known method can be used. As the specific application method, a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method and the like can be used. At this time, the slurry composition may be applied to only one surface of the current collector or both surfaces thereof. The thickness of the slurry film on the current collector before application and after drying can be appropriately set in accordance with the thickness of the electrode composite layer obtained by drying.

Here, the current collector to which the slurry composition is applied is not particularly limited as long as it is an electrically conductive and electrochemically durable material. From the viewpoint of heat resistance, the material of the current collector is preferably a metal such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold and platinum. Among them, for example, aluminum is particularly preferable for positive electrode, and copper is preferable for negative electrode. The material of the current collector may be used singly or two or more kinds may be used in combination at an arbitrary ratio.

[Drying process]

The method for drying the slurry composition on the current collector is not particularly limited and a known method can be used. For example, a drying method by hot air, hot air, low-humidity air, vacuum drying, . By drying the slurry composition on the current collector in this manner, an electrode composite layer is formed on the current collector to obtain an electrode for a lithium ion secondary battery having a current collector and an electrode composite layer.

After the drying step, the electrode composite layer may be subjected to pressure treatment using a die press or a roll press. By the pressure treatment, the adhesion between the electrode composite layer and the current collector can be improved and the porosity of the electrode can be lowered.

Another example of the method for producing the electrode for a lithium ion secondary battery of the present invention is a powder forming method. The powder forming method is a method in which a slurry composition for preparing an electrode for a lithium ion secondary battery is prepared, composite particles containing an electrode active material or the like are prepared from the slurry composition, the composite particles are supplied onto a current collector, Pressing and molding to form an electrode composite layer to obtain an electrode for a lithium ion secondary battery. As the slurry composition, the slurry composition as described above may be used.

(Lithium ion secondary battery)

The lithium ion secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolyte, and a separator, and at least one of the positive electrode and the negative electrode uses the electrode for a lithium ion secondary battery of the present invention. Since the lithium ion secondary battery of the present invention uses the electrode for lithium ion secondary battery described above, it has a low internal resistance.

<Electrode>

As described above, the electrode for a lithium ion secondary battery of the present invention is used as at least one of a positive electrode and a negative electrode. That is, the positive electrode of the lithium ion secondary battery of the present invention may be an electrode for a lithium ion secondary battery of the present invention and the negative electrode of a negative electrode may be a known negative electrode, and the negative electrode of the lithium ion secondary battery of the present invention is an electrode for a lithium ion secondary battery of the present invention, And the positive electrode and the negative electrode of the lithium ion secondary battery of the present invention may be electrodes for the lithium ion secondary battery of the present invention.

<Electrolyte>

As the electrolyte for the lithium ion secondary battery, for example, a nonaqueous electrolyte solution in which a supporting electrolyte is dissolved in a nonaqueous solvent is used. As the supporting electrolyte, a lithium salt is usually used. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (CF ₃ SO _{2) 2} NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Of these, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li, which are easily soluble in solvents and exhibit high dissociation, are preferred. These may be used singly or in combination of two or more in an arbitrary ratio. The higher the degree of dissociation of the supporting electrolyte, the higher the lithium ion conductivity. Therefore, the lithium ion conductivity can be controlled by the type of the supporting electrolyte.

The non-aqueous solvent is not particularly limited as long as it can dissolve the supporting electrolyte. Examples of the non-aqueous solvent include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC) and methyl ethyl carbonate (MEC); esters such as? -butyrolactone and methyl formate; Ethers such as 1,2-dimethoxyethane and tetrahydrofuran; Sulfur compounds including sulfolane and dimethyl sulfoxide; And the like. Among them, carbonates are preferable because of high dielectric constant and stable wide potential range. The non-aqueous solvent may be used alone or in combination of two or more in an arbitrary ratio.

The electrolytic solution may contain an additive. Examples of the additive include carbonate compounds such as vinylene carbonate (VC). One kind of additives may be used alone, or two or more kinds of additives may be used in combination at an arbitrary ratio. Examples of the electrolytic solution other than the above include polymer electrolytes such as polyethylene oxide and polyacrylonitrile; A gelated polymer electrolyte impregnated with an electrolyte solution in the polymer electrolyte; Inorganic solid electrolytes such as LiI and Li ₃ N; May be used.

<Separator>

As the separator, for example, those described in JP-A-2012-204303 can be used. Among these, from the viewpoint that the thickness of the entire separator is made thinner and the capacity per unit volume can be increased by raising the ratio of the electrode active material in the lithium ion secondary battery, it is preferable to use a polyamide resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) Sclera is preferred.

<Manufacturing Method of Lithium Ion Secondary Battery>

As a specific method for producing the lithium ion secondary battery of the present invention, for example, a positive electrode and a negative electrode are superimposed with a separator interposed therebetween, and the battery is put into a battery container by winding or folding according to the shape of the battery, And a method of sealing it. Expendable metal as needed; An overcurrent prevention element such as a fuse or a PTC element; A lead plate or the like may be inserted so as to prevent an increase in pressure inside the battery and overcharge discharge. The shape of the secondary battery may be a coin type, a button type, a sheet type, a cylindrical type, a square type, or a flat type.

Example

Hereinafter, the present invention will be described concretely based on examples, but the present invention is not limited to these examples. In the following description, &quot;% &quot; and &quot; part &quot; representing amounts are on a mass basis unless otherwise specified.

In the following examples, as a mode of the present invention, a lithium ion secondary battery was produced by using the binder composition for a lithium ion secondary battery electrode of the present invention only for a positive electrode.

In the Examples and Comparative Examples, the polymerization conversion rate of the monomers, the peak intensity of the positive electrode for a lithium ion secondary battery, and the low temperature characteristics, high temperature storage characteristics and high temperature cycle characteristics of the lithium ion secondary battery were evaluated by the following methods, respectively.

<Polymerization Conversion of Monomer>

In the preparation of the monomer composition, the total weight of the respective monomers (the total weight of the charged monomers), the total weight of the deionized water (weight of the input) and the total weight of all the raw materials (total weight of the charged raw materials) charged into the autoclave were precisely weighed.

Further, when polymerization was carried out using the monomer composition, a part of the obtained polymerization reaction product was first taken and the weight (weight of the polymerization reaction product before drying) was precisely weighed. Then, the collected weight reactant was dried in a hot-air dryer at a temperature of 120 DEG C for 1 hour, and the weight (weight of polymerization reactant after drying) was precisely weighed. Here, (weight of polymerization reactant after drying) / (weight of polymerization reactant before drying) x 100 was calculated, and the solid fraction (%) of the polymerization reaction product was determined.

(Total weight of the input raw material) x (solid content of the weight reactant) - {(total weight of the input raw material) - (weight of the input water) - (total weight of the input monomer)} / (total weight of the input monomer) The conversion rate (%) was determined.

<Peel Strength of Positive Electrode for Lithium Ion Secondary Battery>

The prepared positive electrode was cut into a rectangle having a width of 1.0 cm and a length of 10 cm to prepare a test piece. Then, a cellophane tape was attached to the surface of the test piece on the side of the positive electrode composite layer. At this time, the cellophane tape specified in JIS Z1522 was used. Then, the stress was measured when the test piece was peeled from the one end side toward the other end side at a speed of 50 mm / minute while the cellophane tape was fixed to the test stand. The measurement was carried out ten times, and an average value of the stress was obtained. The average stress value was determined as the peel strength (N / m) and evaluated according to the following criteria. The larger the fill strength, the better the bondability of the binder and the higher the adhesion of the positive electrode composite layer to the current collector.

A: Peel strength of 30 N / m or more

B: Peel strength of 20 N / m or more and less than 30 N / m

C: Peel strength of 10 N / m or more and less than 20 N / m

D: Peel strength less than 10 N / m

<Low-temperature characteristics of lithium ion secondary battery>

In order to evaluate the low-temperature characteristics of the produced lithium ion secondary battery, the IV resistance was measured as follows. After charging to 50% of the SOC (state of charge) at a temperature of -10 ° C and 1 C (C is the rated capacity (mA) / hour (h)), 50% of the SOC is centered Charging for 15 seconds at 0.5 C, 1.0 C, 1.5 C and 2.0 C, and discharging for 15 seconds, respectively, and the battery voltage after 15 seconds in each case (charging side and discharging side) And the slope thereof was obtained as an IV resistance (?) (IV resistance at charging and IV resistance at discharging). The obtained IV resistance value (?) Was evaluated according to the following criteria. The smaller the IV resistance value, the lower the internal resistance and the better the low temperature characteristic.

A: IV resistance is 10Ω or less

B: IV resistance is more than 10 Ω and less than 15 Ω

C: IV resistance is more than 15Ω and less than 20Ω

D: IV resistance exceeds 20Ω

&Lt; High Temperature Storage Characteristics of Lithium Ion Secondary Battery >

The prepared lithium ion secondary battery was charged to 4.3 V at a constant current of 0.1 C under an environment of 25 캜 and then stored at 80 캜 for 100 hours. (OCV) before the start of storage at 80 DEG C and OCV of the cell after storage at 80 DEG C for 100 hours were measured and stored at 80 DEG C for OCV before the start of storage at 80 DEG C for 100 hours The OCV retention ratio was calculated by the following criteria. The higher the OCV retention rate, the better the high-temperature storage characteristics, that is, the better the life characteristics.

A: OCV retention rate of 99.0% or more

B: OCV retention rate of 98.5% or more and less than 99.0%

C: OCV retention rate is 98.0% or more and less than 98.5%

D: OCV retention rate less than 98.0%

<High-temperature cycle characteristics of lithium ion secondary battery>

The prepared lithium ion secondary battery was charged at 4.2 V by a constant current method of 1.0 C under an atmosphere of 45 캜, and discharging to 3.0 V was performed for one cycle. This operation was repeated for 100 cycles. The charge / discharge capacity retention ratio (%) indicated by the ratio of the electric capacity at the end of 100 cycles to the electric capacity at the end of 5 cycles ((electric capacity at the end of 100 cycles / electric capacity at the end of 5 cycles) × 100) Respectively. The higher the charge-discharge capacity retention rate, the better the high-temperature cycle characteristics.

A: The charge / discharge capacity retention rate is 95% or more

B: charge / discharge capacity retention rate is 90% or more and less than 95%

C: charge / discharge capacity retention rate is 85% or more and less than 90%

D: charge / discharge capacity retention rate is less than 85%

(Example 1)

&Lt; Preparation of monomer composition >

30 parts of methacrylic acid, 300 parts of deionized water and 7.3 parts of lithium hydroxide monohydrate were placed in an autoclave equipped with a stirrer and stirred for 10 minutes to lithium chloride a part of methacrylic acid with lithium hydroxide to obtain lithium methacrylate 16 , And 15 parts of methacrylic acid as monomer b was obtained. Subsequently, 69 parts of acrylonitrile as the monomer c was added to the obtained aqueous solution to prepare a monomer composition.

<Preparation of binder composition for lithium ion secondary battery electrode>

0.5 part of potassium persulfate as a polymerization initiator was added to the monomer composition obtained as described above and the polymerization was carried out at 70 DEG C for 3 hours and at 85 DEG C for 3 hours after substitution with nitrogen to obtain a homogeneous aqueous dispersion &Lt; / RTI &gt;

350 parts of N-methylpyrrolidone (NMP) was added to 100 parts of the aqueous dispersion (solid content: 24.75 parts), water was evaporated under reduced pressure and 40.62 parts of NMP was evaporated to obtain a binder composition for a lithium ion secondary battery electrode (Solid content concentration: 8%).

The composition and the polymerization conversion rate of the prepared monomer composition at the time of polymerizing the polymer are shown in Table 1.

&Lt; Preparation of Slurry Composition for Positive Electrode of Lithium Ion Secondary Battery >

100 parts of LiCoO ₂ (manufactured by Nippon Kayaku Co., Ltd., product name: CELSED C-10N) as a positive electrode active material, 2 parts of acetylene black as a conductive material, and 1 part of a binder composition prepared in the manner described above, N-methylpyrrolidone was further added so as to have a viscosity of 4000 to 5000 mPa · s, followed by mixing with a planetary mixer to prepare a slurry composition for positive electrode of a lithium ion secondary battery.

&Lt; Preparation of positive electrode for lithium ion secondary battery >

The slurry composition for positive electrode was applied to an aluminum foil having a thickness of 18 탆 and dried at 120 캜 for 3 hours, followed by roll pressing to obtain a positive electrode having a positive electrode mixture layer having a thickness of 50 탆. The peel strength of the obtained positive electrode was evaluated. The results are shown in Table 1.

<Fabrication of negative electrode for lithium ion secondary battery>

98 parts of graphite having a volume average particle diameter of 20 mu m as a negative electrode active material and a specific surface area of 4.2 m &lt; ² &gt; / g, 1.0 part of a 40% by mass aqueous dispersion of a styrene-butadiene copolymer (BM- 400B, manufactured by Nippon Zeon Co., And 1.0 part (corresponding to solid content) of sodium salt of carboxymethylcellulose as a viscosity adjuster were mixed, and water was added thereto again, followed by mixing with a planetary mixer to prepare a slurry composition for negative electrode. The slurry composition for negative electrode was coated on one side of a copper foil having a thickness of 10 mu m and dried at 110 DEG C for 3 hours, followed by roll pressing to obtain a negative electrode having a negative electrode laminate layer having a thickness of 60 mu m.

<Fabrication of Laminate Cell Type Lithium Ion Secondary Battery>

A battery container was manufactured using a laminate film made of an aluminum sheet and a polypropylene resin covering both sides thereof. Subsequently, the electrode composite layer was removed from the ends of each of the positive electrode and the negative electrode described above to form a portion where the copper foil or aluminum foil was exposed. Ni taps were welded to portions where the aluminum foil of the positive electrode was exposed, and Cu taps were welded to portions where the copper foil of the negative electrode was exposed. The obtained tabbed positive electrode and tabbed negative electrode were superimposed with a separator made of a microporous polyethylene film interposed therebetween. The direction of the electrode surface was a direction in which the surface of the positive electrode on the positive electrode composite material layer side and the surface of the negative electrode on the negative electrode material mixture layer side were opposed to each other. The overlapped electrode and the separator were wound and stored in the battery container. Then, an electrolytic solution was injected thereto. As an electrolyte solution, ethylene carbonate and diethyl carbonate to a 25 ℃, a volume ratio of 1: was dissolved to a concentration of 1 mol / L of LiPF ₆ in a mixed solvent of 2 was used as prepared.

And then the laminate film was sealed to fabricate a laminate cell type secondary battery which is a lithium ion secondary battery of the present invention. The obtained laminate cell type secondary battery was evaluated for low temperature characteristics, high temperature storage characteristics and high temperature cycle characteristics. The results are shown in Table 1.

(Examples 2 and 3)

Except that the amount of methacrylic acid, lithium hydroxide monohydrate, and acrylonitrile was changed at the time of preparation of the monomer composition so that the composition of the monomer composition was as shown in Table 1. In the same manner as in Example 1, A positive electrode, a negative electrode and a secondary battery were prepared and prepared, and various evaluations were carried out. The results are shown in Table 1.

(Example 4)

The blending amount of acrylonitrile at the time of preparation of the monomer composition was changed so that the composition of the monomer composition was as shown in Table 1, and butyl acrylate (having a weight average molecular weight of 10,000 or more and a Tg of -54 占 폚 or less ) Was prepared and prepared in the same manner as in Example 1, except that the monomer composition was blended in the monomer composition as shown in Table 1 to prepare a binder composition for electrodes, a slurry composition for a positive electrode, a positive electrode, a negative electrode and a secondary battery, . The results are shown in Table 1.

(Example 5)

A binder composition for a electrode, a slurry composition for a positive electrode, a positive electrode, a negative electrode and a secondary battery were prepared and prepared in the same manner as in Example 1 except that the monomer composition prepared as described below was used. The results are shown in Table 1.

&Lt; Preparation of monomer composition >

29.78 parts of acrylic acid, 300 parts of deionized water and 8.6 parts of lithium hydroxide monohydrate were added to an autoclave equipped with a stirrer and stirred for 10 minutes to convert a part of acrylic acid into lithium chloride with lithium hydroxide to obtain 16 parts of lithium acrylate as monomer a, To obtain an aqueous solution containing 15 parts of acrylic acid. Subsequently, 69 parts of acrylonitrile as monomer c was added to the obtained aqueous solution to prepare a monomer composition.

(Examples 6 and 7)

Except that the amount of acrylic acid, lithium hydroxide monohydrate, and acrylonitrile was changed during the preparation of the monomer composition so that the composition of the monomer composition was as shown in Table 1, the binder composition for electrodes, A slurry composition, a positive electrode, a negative electrode, and a secondary battery were prepared and prepared, and various evaluations were conducted. The results are shown in Table 1.

(Example 8)

The mixing amount of acrylonitrile at the time of preparation of the monomer composition was changed so that the composition of the monomer composition was as shown in Table 1 and butyl acrylate as the monomer d was added to the monomer composition so that the content of the monomer d was as shown in Table 1 , A positive electrode slurry composition, a positive electrode, a negative electrode and a secondary battery were prepared and prepared, and various evaluations were carried out. The results are shown in Table 1.

(Example 9)

A binder composition for a electrode, a slurry composition for a positive electrode, a positive electrode, a negative electrode and a secondary battery were prepared and prepared in the same manner as in Example 1 except that the monomer composition prepared as described below was used. The results are shown in Table 1.

&Lt; Preparation of monomer composition >

16 parts of lithium p-styrenesulfonate (LiSS, manufactured by Tohto Yuki Kagaku K.K.) as monomer a, 15 parts of methacrylic acid as monomer b, 69 parts of acrylonitrile as monomer c, And 300 parts of deionized water were added and mixed to prepare a monomer composition.

(Examples 10 and 11)

Styrene sulfonic acid lithium salt, methacrylic acid and acrylonitrile in the preparation of the monomer composition so that the composition of the monomer composition was as shown in Table 1, the binder composition for electrodes , A positive electrode slurry composition, a positive electrode, a negative electrode, and a secondary battery were prepared and manufactured, and various evaluations were conducted. The results are shown in Table 1.

(Example 12)

The mixing amount of acrylonitrile at the time of preparation of the monomer composition was changed so that the composition of the monomer composition was as shown in Table 1 and butyl acrylate as the monomer d was added to the monomer composition so that the content of the monomer d was as shown in Table 1 A negative electrode composition, a positive electrode slurry composition, a positive electrode, a negative electrode and a secondary battery were prepared and prepared in the same manner as in Example 9, and various evaluations were conducted. The results are shown in Table 1.

(Example 13)

Except that 0.5 part of the binder composition was used in an amount corresponding to the solid content and 0.5 part of polyvinylidene fluoride (PVDF) (product name: KF # 7208, product of Kureha Kagaku Co., Ltd.) , A positive electrode slurry composition, a positive electrode, a negative electrode, and a secondary battery were prepared and manufactured, and various evaluations were conducted. The results are shown in Table 1.

(Comparative Example 1)

A negative electrode composition for a positive electrode, a positive electrode slurry composition, a positive electrode, a negative electrode and a secondary battery were prepared and prepared in the same manner as in Example 1 except that the monomer composition prepared as described below and the binder composition for a lithium ion secondary battery electrode were used , And various evaluations were conducted. The results are shown in Table 1.

&Lt; Preparation of monomer composition >

15 parts of methacrylic acid as monomer b, 85 parts of acrylonitrile as monomer c and 300 parts of deionized water were added to an autoclave equipped with a stirrer to prepare a monomer composition.

<Preparation of binder composition for lithium ion secondary battery electrode>

0.5 part of potassium persulfate as a polymerization initiator was added to the monomer composition obtained as described above, and the mixture was kept at 70 DEG C for 3 hours and at 85 DEG C for 3 hours to carry out polymerization. Subsequently, the coarse- Thereby obtaining an aqueous dispersion containing particles.

1 part of aluminum sulfate was added to this aqueous dispersion, and the solid was washed twice by filtration with water to obtain a solid polymer. To 2475 parts of this polymer, 350 parts of N-methylpyrrolidone (NMP) was added, and water was evaporated under reduced pressure and 40.62 parts of NMP was evaporated to obtain a binder composition for a lithium ion secondary battery electrode (solid concentration: 8% ).

(Comparative Examples 2 and 3)

Except that the compounding amount of methacrylic acid, lithium hydroxide monohydrate, and acrylonitrile was changed so that the composition of the monomer composition was as shown in Table 1, and the amount of the binder composition for electrodes, the positive electrode A positive electrode, a negative electrode and a secondary battery were prepared and prepared, and various evaluations were carried out. The results are shown in Table 1.

(Comparative Example 4)

A binder composition for a electrode, a slurry composition for a positive electrode, a positive electrode, a negative electrode and a secondary battery were prepared and prepared in the same manner as in Example 1 except that the monomer composition prepared as described below was used. The results are shown in Table 1.

&Lt; Preparation of monomer composition >

27.26 parts of methacrylic acid, 300 parts of deionized water and 6.8 parts of sodium hydroxide were placed in an autoclave equipped with a stirrer and stirred for 10 minutes so that a part of the methacrylic acid was sodium chloride with sodium hydroxide. Then, 16 parts of sodium methacrylate, To obtain an aqueous solution containing 15 parts of an acid. Subsequently, 69 parts of acrylonitrile was added to the obtained aqueous solution to prepare a monomer composition.

From Examples 1 to 13 in Table 1, it was found that a polymer composition can be polymerized at a conversion rate of 99% or more by using a monomer composition containing a monomer a to a monomer c in a predetermined ratio, and a binder composition containing such a polymer It is understood that the peel strength of the electrode for a lithium ion secondary battery and the low temperature characteristics, high temperature storage characteristics, and high temperature cycle characteristics of the lithium ion secondary battery can be consolidated at a high level.

In particular, it can be seen from Examples 1 to 12 that the various characteristics can be further improved by adjusting the content of the monomers a to c in the monomer composition.

On the other hand, in Comparative Example 1 of Table 1, since the monomer composition does not contain the monomer a and the content of the monomer c is large, the conversion rate of the polymerization is remarkably low and the polymerization reaction products aggregate during the polymerization . In addition, it can be seen that the lithium ion secondary battery produced using the binder composition of Comparative Example 1 has a high internal resistance and deteriorates the high-temperature storage characteristics and the high-temperature cycle characteristics.

Further, in Comparative Example 2 of Table 1, since the monomer composition excessively contains the monomer a, sufficient flexibility is not imparted to the obtained polymer, and the content of the monomer b is small, so that the peel strength can not be maintained. Further, it can be seen that the high-temperature storage characteristics and the high-temperature cycle characteristics deteriorate due to the excess of the monomer a and the low content of the monomer c.

In Comparative Example 3 shown in Table 1, the monomer composition contained monomer a, but the content of monomers b and c was outside of the predetermined range, so that the lithium ion conductivity and oxidation resistance of the polymer were lowered, The high-temperature storage characteristics and the high-temperature cycle characteristics of the lithium ion secondary battery produced using the composition deteriorate.

In addition, in Comparative Example 4 of Table 1, since the sodium salt is used in place of the lithium salt of the unsaturated acid, the internal resistance of the lithium ion secondary battery is increased and the high temperature storage characteristics and the high temperature cycle characteristics are deteriorated .

It is also understood from Examples 1 and 13 of Table 1 that, in preparing a slurry composition for a lithium ion secondary battery electrode, in addition to the binder composition containing the polymer polymerized using the monomer composition containing the monomers a to c in a predetermined ratio , And it can be seen that various characteristics can be obtained even when a polymer other than such a polymer, for example, a fluorine-containing polymer is blended.

Industrial availability

According to the present invention, it is possible to provide a binder composition for a lithium ion secondary battery electrode that can produce a lithium ion secondary battery having a low internal resistance and excellent both in productivity and tackiness.

Further, according to the present invention, it is possible to provide a slurry composition for a lithium ion secondary battery electrode capable of preparing an electrode for a lithium ion secondary battery having a low internal resistance and an excellent peak strength.

Further, according to the present invention, it is possible to provide an electrode for a lithium ion secondary battery having a low internal resistance and an excellent peak strength.

Further, according to the present invention, a lithium ion secondary battery having a low internal resistance can be provided.

Claims (7)

A monomer composition comprising 10 to 80 mass% of a lithium salt of an unsaturated acid (monomer a), 5 to 40 mass% of an unsaturated acid (monomer b), and 10 to 85 mass% of an alpha, beta -unsaturated nitrile (monomer c) A polymer composition comprising a polymer obtained by polymerization, and a dispersion medium; and a binder composition for a lithium ion secondary battery electrode.
The method according to claim 1,
Wherein the?,? - unsaturated nitrile (monomer c) is acrylonitrile.
A slurry composition for a lithium ion secondary battery electrode, comprising the binder composition for an electrode for lithium ion secondary batteries according to claim 1 or 2 and an electrode active material.
The method of claim 3,
And further comprising a polymer other than the polymer.
5. The method of claim 4,
Wherein the polymer other than the polymer is a fluorine-containing polymer.
An electrode for a lithium ion secondary battery, comprising an electrode composite layer prepared by using the slurry composition for a lithium ion secondary battery electrode according to any one of claims 3 to 5 on a current collector.
A lithium ion secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, 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.