KR102645707B1 - Electrode binder composition for rechargeable battery and electrode mixture including the same - Google Patents

Abstract

The present invention relates to a binder composition for secondary batteries and an electrode mixture containing the same. More specifically, it has excellent properties in terms of binding force, mechanical properties, etc., while maintaining the structural stability of the electrode at high temperatures, thereby improving the heat resistance of the secondary battery. It relates to a binder composition for secondary batteries that can be improved and an electrode mixture containing the same.

Description

Binder composition and electrode mixture for secondary battery electrodes {ELECTRODE BINDER COMPOSITION FOR RECHARGEABLE BATTERY AND ELECTRODE MIXTURE INCLUDING THE SAME}

The present invention relates to a binder composition for secondary batteries and an electrode mixture containing the same.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative or clean energy is increasing, and as part of this, the most actively researched field is the field of secondary batteries using electrochemistry.

Recently, as technology development and demand for portable devices such as portable computers, portable phones, and cameras increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, those with high energy density and operating potential are Much research has been conducted on lithium secondary batteries with long cycle life and low self-discharge rate, and they have also been commercialized and widely used.

In addition, as interest in environmental issues grows, much research is being conducted on electric vehicles and hybrid vehicles that can replace fossil fuel engines, which are one of the main causes of air pollution. Lithium secondary batteries are used in these electric vehicles and hybrid vehicles. It is also used as a power source for automobiles.

In lithium secondary batteries, lithium transition metal oxide is generally used as a positive electrode active material, and a graphite-based material is used as a negative electrode active material. The electrode of a lithium secondary battery is manufactured by mixing the active material and the binder component, dispersing them in a solvent to create a slurry, and then applying this to the surface of the current collector to form a mixture layer.

Generally, lithium secondary batteries are charged and discharged by repeating the process of insertion and desorption of lithium ions from the positive electrode into the negative electrode. During this repeated process, the bond between the electrode active material or conductive material is loosened, and the contact resistance between particles is reduced. As this increases, the self-resistance of the electrode may also increase.

Therefore, the binder used in the electrode must be able to maintain excellent binding force between the electrode active material and the current collector, while also buffering against expansion and contraction of the electrode active material due to insertion and detachment of lithium ions from the electrode.

In particular, recently, in order to increase the discharge capacity of the electrode, natural graphite, which has a theoretical discharge capacity of 372 mAh/g, is often used in combination with materials such as silicon, tin, and silicon-tin alloy, which have a large discharge capacity. Accordingly, as charging and discharging are repeated, the volume expansion rate of the material significantly increases, which causes separation of the negative electrode material, resulting in a rapid decrease in battery capacity and a shortened lifespan.

In addition, lithium-ion batteries may swell due to gas generated when the electrolyte inside the battery decomposes, causing swelling. When the temperature of the battery rises with the use of electronic products, decomposition of the electrolyte is accelerated and swelling occurs. The ringing phenomenon may accelerate and the stability of the battery may deteriorate.

Therefore, there is an urgent need for research on binders and electrode materials that can achieve excellent bonding power to the extent of preventing separation between electrode active materials or between electrode active materials and the current collector, while maintaining the structural stability of the electrode even at high temperatures. This is the situation.

The present specification seeks to provide a binder composition for a secondary battery that has excellent properties in terms of binding force, mechanical properties, etc., while maintaining the structural stability of the electrode even through repeated charge and discharge cycles.

In addition, the present specification seeks to provide a secondary battery electrode mixture containing the binder composition for secondary batteries.

Additionally, the present specification seeks to provide a secondary battery electrode containing the secondary battery electrode mixture.

Additionally, the present specification seeks to provide a secondary battery including the secondary battery electrode.

According to one aspect of the present invention,

Repeating units derived from conjugated diene monomers; A group consisting of a repeating unit derived from an aromatic vinyl monomer, a repeating unit derived from an alkyl (meth)acrylate monomer, a repeating unit derived from a (meth)acryl amide monomer, a repeating unit derived from a nitrile monomer, and a repeating unit derived from an unsaturated carboxylic acid monomer. Emulsified polymer particles comprising one or more repeating units selected from; and

containing pigments;

A binder composition for secondary battery electrodes is provided.

The pigment may exist in a dispersed form within the emulsified polymer particles or in a form adsorbed on the surface of the emulsified polymer.

At this time, the emulsified polymer particles are: A) conjugated diene-based latex particles; and B) acrylate-based latex particles; It may include one or more of the following.

According to one embodiment of the invention, the conjugated diene-based latex particles include: a1) a first repeating unit derived from a conjugated diene-based monomer; a2) repeating units derived from aromatic vinyl monomers, a3) repeating units derived from alkyl (meth)acrylate monomers, and a4) repeating units derived from hydroxy alkyl (meth)acrylate monomers. repeat unit; and a6) a conjugated diene-based copolymer comprising a third repeating unit derived from an unsaturated carboxylic acid-based monomer, and more specifically, a latex particle of a terpolymer comprising at least three different repeating units.

At this time, the conjugated diene-based latex particles, based on the total weight of the conjugated diene-based latex particles, include a1) about 40 to about 65 wt% of the first repeating unit derived from the conjugated diene-based monomer; a2) repeating units derived from aromatic vinyl monomers, a3) repeating units derived from alkyl (meth)acrylate monomers, and a4) repeating units derived from hydroxy alkyl (meth)acrylate monomers. About 30 to about 50 wt% repeat units; and a6) about 1 to about 15 wt% of a third repeating unit derived from an unsaturated carboxylic acid monomer.

And, according to another embodiment of the invention, the acrylate-based latex particles include: b1) a fourth repeating unit derived from an alkyl (meth)acrylate-based monomer; and b2) a repeating unit derived from an aromatic vinyl monomer, b3) a hydroxyalkyl (meth)acrylate monomer, and b4) a repeating unit derived from an unsaturated carboxylic acid monomer. You can.

At this time, the acrylate-based latex particles, based on the total weight of the acrylate-based latex particles, b1) about 50 to about 80 wt% of the fourth repeating unit derived from an alkyl (meth)acrylate-based monomer; and b2) a repeating unit derived from an aromatic vinyl monomer, b3) a hydroxyalkyl (meth)acrylate monomer, and b4) a fifth repeating unit selected from the group consisting of a repeating unit derived from an unsaturated carboxylic acid monomer. It may contain about 50 wt%.

In addition, the binder composition for secondary battery electrodes contains about 95 to about 99.99 wt% of emulsified polymer particles, based on the total weight of solid content, that is, the total weight of solid content excluding the solvent in the composition; and about 0.01 to about 5 wt% of pigment.

The pigment may include any one or more of organic pigments and inorganic pigments.

In addition, the binder composition for secondary battery electrodes may further include an aqueous solvent.

Meanwhile, according to another aspect of the invention, a secondary battery electrode mixture containing the above-described binder composition for secondary battery electrodes and an electrode active material is provided.

The secondary battery electrode mixture may further include a conductive material.

Meanwhile, according to another aspect of the invention, an electrode mixture layer comprising the above-described secondary battery electrode mixture; and an electrode current collector; A secondary battery electrode is provided.

And, according to another aspect of the invention, a secondary battery including the above-described secondary battery electrode is provided.

In the present invention, terms such as first and second are used to describe various components, and the terms are used only for the purpose of distinguishing one component from other components.

Additionally, the terminology used herein is only used to describe exemplary embodiments and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise,” “comprise,” or “have” are intended to designate the presence of implemented features, numbers, steps, components, or combinations thereof, and are intended to indicate the presence of one or more other features or It should be understood that this does not exclude in advance the possibility of the presence or addition of numbers, steps, components, or combinations thereof.

Additionally, in the present invention, when each layer or element is referred to as being formed “on” or “on” the respective layers or elements, it means that each layer or element is formed directly on the respective layers or elements, or other This means that layers or elements can be additionally formed between each layer, on the object, or on the substrate.

Since the present invention can be subject to various changes and can take various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Hereinafter, the present invention will be described in detail.

According to one aspect of the present invention,

Repeating units derived from conjugated diene monomers; A group consisting of a repeating unit derived from an aromatic vinyl monomer, a repeating unit derived from an alkyl (meth)acrylate monomer, a repeating unit derived from a (meth)acryl amide monomer, a repeating unit derived from a nitrile monomer, and a repeating unit derived from an unsaturated carboxylic acid monomer. Emulsified polymer particles comprising one or more repeating units selected from; and

containing pigments;

A binder composition for secondary battery electrodes is provided.

The inventors of the present invention found that, in a binder composition for secondary battery electrodes, when a specific combination of monomers and a specific pigment are used together to produce emulsified polymer particles, that is, latex particles, coloring or color matching can be imparted to the binder composition. In addition, it was discovered that the dielectric properties of the binder itself could be adjusted or heat resistance and weather resistance could be improved by using the properties of the material used as a pigment, and the present invention was completed.

First, the binder composition for a secondary battery electrode according to an embodiment of the present invention includes emulsified polymer particles of a specific monomer, that is, latex particles, and each monomer may exist in the form of a repeating unit derived from the monomer in the latex particle. You can.

At this time, the emulsified polymer particles are, more specifically, A) conjugated diene-based latex particles; and B) acrylate-based latex particles; It may include one or more of the following.

Conjugated diene-based latex particles

According to one embodiment of the invention, the conjugated diene-based latex particles include: a1) a first repeating unit derived from a conjugated diene-based monomer; a2) repeating units derived from aromatic vinyl monomers, a3) repeating units derived from alkyl (meth)acrylate monomers, and a4) repeating units derived from hydroxy alkyl (meth)acrylate monomers. repeat unit; and a6) a conjugated diene-based copolymer comprising a third repeating unit derived from an unsaturated carboxylic acid-based monomer, and more specifically, a latex particle of a terpolymer comprising at least three different repeating units.

First, in emulsion polymerization to produce the conjugated diene-based latex particles, a conjugated diene-based monomer may be used, and accordingly, the conjugated diene-based latex particles include a repeating unit derived from the conjugated diene-based monomer, that is, the first May contain repeat units.

Representative examples of the conjugated diene monomer may be one or more selected from the group consisting of 1,3-butadiene, isoprene, chloroprene, and piperylene, and preferably 1,3-butadiene.

When these conjugated diene-based monomers are included as a component of latex particles, the binder produced from them can suppress the electrolyte swelling phenomenon at high temperatures, have elasticity due to the rubber component, and reduce the thickness of the electrode. , it not only reduces the gas generation phenomenon, but also plays a role in improving adhesion so that the cohesion between the electrode active material and the current collector can be maintained.

In the emulsion polymerization for producing the conjugated diene-based latex particles, in addition to the conjugated diene-based monomer, a2) aromatic vinyl-based monomer, a3) alkyl (meth)acrylate-based monomer, and a4) hydroxyalkyl (meth) One or more monomers selected from the group consisting of acrylate-based monomers may be used, and accordingly, the conjugated diene-based latex particles may include a repeating unit derived from the above-described monomer, that is, a second repeating unit.

The aromatic vinyl monomer consists of styrene, α-methylstyrene, β-methylstyrene, p-t-butylstyrene, chlorostyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, and divinylbenzene. It may be one or more monomers selected from the group, and preferably, may be styrene.

In addition, the alkyl (meth)acrylate monomers include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, and isoamyl acrylate. Latex, n-ethylhexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, lauryl acrylate, ceryl acrylate, stearyl acrylate, It may be one or more selected from the group consisting of lauryl methacrylate, cetyl methacrylate, and stearyl methacrylate.

And, the hydroxyalkyl (meth)acrylate monomers include hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxymethyl methacrylate, and hydroxyethyl methacrylate. It may be one or more selected from the group consisting of acrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate.

In addition, in emulsion polymerization for producing the conjugated diene-based latex particles, an unsaturated carboxylic acid-based monomer may be used, and accordingly, the conjugated diene-based latex particles contain a repeating unit derived from the above-described monomer, that is, the third repeat. May include units.

In addition, the unsaturated carboxylic acid monomer may be one or more selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, and nadic acid. there is.

In addition, the conjugated diene-based latex particles prepared by emulsion polymerization of the above-mentioned monomers have a low degree of electrolyte swelling and a high bonding force with the current collector, which can improve the lifespan characteristics of the electrode, and a binder composition containing such latex particles It can improve the overall performance of lithium secondary batteries.

At this time, the conjugated diene-based latex particles, based on the total weight of the conjugated diene-based latex particles, include a1) about 40 to about 65 wt% of the first repeating unit derived from the conjugated diene-based monomer; a2) repeating units derived from aromatic vinyl monomers, a3) repeating units derived from alkyl (meth)acrylate monomers, and a4) repeating units derived from hydroxy alkyl (meth)acrylate monomers. About 30 to about 50 wt% repeat units; and a6) may include about 1 to about 15 wt% of a third repeating unit derived from an unsaturated carboxylic acid-based monomer, preferably, based on the total weight of the conjugated diene-based latex particles, a1) a first repeating unit derived from a conjugated diene-based monomer. Units from about 45 to about 60 wt%; a2) repeating units derived from aromatic vinyl monomers, a3) repeating units derived from alkyl (meth)acrylate monomers, and a4) repeating units derived from hydroxy alkyl (meth)acrylate monomers. About 40 to about 50 wt% repeat units; and a6) about 4 to about 10 wt% of a third repeating unit derived from an unsaturated carboxylic acid monomer.

If the relative content range is outside the above-mentioned range, the glass transition temperature of the binder may be lowered, causing a problem of lowered adhesive strength, or conversely, the glass transition temperature of the binder may be increased and rigidity may be increased, resulting in decreased flexibility and adhesive strength. Problems may arise.

Acrylate-based latex particles

According to one embodiment of the invention, the acrylate-based latex particles include: b1) a fourth repeating unit derived from an alkyl (meth)acrylate-based monomer; and b2) a repeating unit derived from an aromatic vinyl monomer, b3) a hydroxyalkyl (meth)acrylate monomer, and b4) a repeating unit derived from an unsaturated carboxylic acid monomer, comprising at least one fifth repeating unit selected from the group consisting of , it may be an acrylate-based copolymer, more specifically, a latex particle of a binary copolymer containing at least two different repeating units.

First, in emulsion polymerization to produce the acrylate-based latex particles, an alkyl (meth)acrylate-based monomer may be used, and accordingly, the acrylate-based latex particles are derived from an alkyl (meth)acrylate-based monomer. It may include a repeating unit, that is, a fourth repeating unit.

In addition, the alkyl (meth)acrylate monomers include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, and isoamyl acrylate. Latex, n-ethylhexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, lauryl acrylate, ceryl acrylate, stearyl acrylate, It may be one or more selected from the group consisting of lauryl methacrylate, cetyl methacrylate, and stearyl methacrylate.

In the emulsion polymerization for producing the acrylate-based latex particles, in addition to the alkyl (meth)acrylate-based monomer, b2) a repeating unit derived from an aromatic vinyl-based monomer, b3) a hydroxyalkyl (meth)acrylate-based monomer, and b4) one or more monomers selected from the group consisting of repeating units derived from unsaturated carboxylic acid-based monomers may be further used, and thus the acrylate-based latex particles include repeating units derived from the above-mentioned monomers, that is, the fifth repeating May include units.

The aromatic vinyl monomer consists of styrene, α-methylstyrene, β-methylstyrene, p-t-butylstyrene, chlorostyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, and divinylbenzene. It may be one or more monomers selected from the group, and preferably, may be styrene.

And, the hydroxyalkyl (meth)acrylate monomers include hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxymethyl methacrylate, and hydroxyethyl methacrylate. It may be one or more selected from the group consisting of acrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate.

In addition, the unsaturated carboxylic acid monomer may be one or more selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, and nadic acid. and metal salts thereof can also be used.

In addition, acrylate-based latex particles prepared by emulsion polymerization of the above-mentioned monomers have a low degree of electrolyte swelling and a high bonding force with the current collector, which can improve the lifespan characteristics of the electrode, and a binder composition containing such latex particles It can improve the overall performance of lithium secondary batteries.

At this time, the acrylate-based latex particles, based on the total weight of the acrylate-based latex particles, include: b1) about 50 to about 80 wt% of a fourth repeating unit derived from an alkyl (meth)acrylate-based monomer; and b2) a repeating unit derived from an aromatic vinyl monomer, b3) a hydroxyalkyl (meth)acrylate monomer, and b4) a fifth repeating unit selected from the group consisting of a repeating unit derived from an unsaturated carboxylic acid monomer. It may contain about 50 wt%, and preferably, based on the total weight of the acrylate-based latex particles, b1) about 65 to about 75 wt% of a fourth repeating unit derived from an alkyl (meth)acrylate-based monomer; and b2) a repeating unit derived from an aromatic vinyl monomer, b3) a hydroxyalkyl (meth)acrylate monomer, and b4) a fifth repeating unit selected from the group consisting of a repeating unit derived from an unsaturated carboxylic acid monomer. It may contain about 35 wt%.

If the relative content is outside the above-mentioned range, the strength of the binder may be reduced or the affinity with the electrolyte may be reduced, and accordingly, problems such as deterioration of adhesion and high temperature stability may occur.

pigment

Meanwhile, the binder composition for secondary battery electrodes according to one embodiment of the present invention includes a pigment. At this time, the pigment may include any one or more of organic pigments and inorganic pigments.

These pigments can primarily impart coloring or coloring properties to the manufactured latex particles and binder composition for secondary battery electrodes.

Conventionally used binder compositions for secondary battery electrodes are usually colorless and transparent or have the form of a white emulsion in which white emulsified polymer particles, that is, latex particles, are dispersed in a solvent. However, in the case of such binder compositions, it is difficult to distinguish them from other reagents or additives in secondary battery manufacturing or experiments for secondary battery performance evaluation, causing a problem of delaying the manufacturing or testing process.

The binder composition for secondary battery electrodes according to one aspect of the present invention can impart coloring or color matching properties to the binder by including at least one of organic pigments and inorganic pigments, and thus can be easily used in other binder compositions, Or, there are characteristics that can visually distinguish it from a reagent.

In addition, since the inorganic or organic pigments have unique chemical properties depending on the individual material, they can adjust the dielectric properties of the binder itself or improve the heat resistance and weather resistance of electrodes manufactured from such binders. You can.

For example, in the case of organic pigments, color matching can be improved by adjusting the transmission spectrum or absorption spectrum of the film of the resin composition, such as transmitting or blocking light of a specific desired wavelength by changing the chemical structure or sensory conversion, Depending on its molecular structure, high temperature stability, etc. can be imparted to the binder composition.

Such organic pigments include, for example, phthalocyanine-based pigments, anthraquinone-based pigments, quinacridone-based pigments, pyranthrone-based pigments, dioxazine-based pigments, thioindigo-based pigments, diketopyrrolopyrrole-based pigments, quinophthalone-based pigments, Threne-based pigments, indoline-based pigments, isoindoline-based pigments, isoindolinone-based pigments, benzofuranone-based pigments, perylene-based pigments, aniline-based pigments, azo-based pigments, azomethine-based pigments, condensed azo-based pigments, carbon black, Metal complex pigments, lake pigments, toner pigments, or fluorescent pigments can be mentioned. From the viewpoint of heat resistance, examples include anthraquinone-based pigments, quinacridone-based pigments, pyranthrone-based pigments, diketopyrrolopyrrole-based pigments, benzofuranone-based pigments, perylene-based pigments, condensed azo-based pigments, and carbon black. However, the present invention is not necessarily limited thereto.

Specific examples of the phthalocyanine-based pigment include copper phthalocyanine-based compounds, copper halide phthalocyanine-based compounds, or metal-free phthalocyanine-based compounds.

Anthraquinone-based pigments specifically include, for example, aminoanthraquinone-based compounds, diaminoanthraquinone-based compounds, anthrapyrimidine-based compounds, flavanthrone-based compounds, anthanthrone-based compounds, indanthrone-based compounds, and pyrantrone. type compounds or violanthrone type compounds.

Specific examples of the azo pigment include disazo compounds or polyazo compounds.

As another example, inorganic pigments have the advantage of improving heat resistance and weather resistance of electrodes manufactured using a binder composition.

Inorganic pigments specifically include, for example, titanium oxide, barium carbonate, zirconium oxide, zinc sulfide, lead white, calcium carbonate, barium sulfate, white carbon, alumina white, silicon dioxide, kaolin clay, talc, bentonite, bengala, molybdenum red. , molybdenum orange, chrome vermillion, yellow lead, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, Victoria green, ultramarine blue, royal blue, cobalt blue, cerulean blue. , cobalt silica blue, cobalt zinc silica blue, manganese violet, cobalt violet, graphite, etc.

In addition, the binder composition for secondary battery electrodes contains about 95 to about 99.99 wt% of emulsified polymer particles, based on the total weight of solid content, that is, the total weight of solid content excluding the solvent in the composition; and about 0.01 to about 5 wt% of pigment, preferably about 98 to about 99.9 wt% of emulsified polymer particles; and about 0.1 to about 2 wt% pigment, or about 99.5 to about 99.9 wt% emulsified polymer particles; and about 0.1 to about 0.5 wt% of pigment.

If it is outside the above range, the adhesive strength of the binder may be reduced, heat resistance may be reduced, and stability at high temperatures may be greatly reduced.

emulsion polymerization

Emulsion polymer particles, that is, latex particles, contained in the binder composition according to one embodiment of the present invention may be manufactured by a generally known emulsion polymerization method, as described above.

At this time, the polymerization temperature and polymerization time can be appropriately determined depending on the case. For example, the polymerization temperature may be from about 50° C. to about 200° C. and the polymerization time may be from about 0.5 hours to about 20 hours.

As a polymerization initiator usable in the emulsion polymerization, inorganic or organic peroxides may be used. For example, water-soluble initiators including potassium persulfate, sodium persulfate, ammonium persulfate, etc., cumene hydroperoxide, and benzoyl peroxide. Oil-soluble initiators containing oxides and the like can be used.

In addition, an activator may be further included to promote the initiation of the reaction of peroxide along with the polymerization initiator, and such activator includes sodium formaldehyde sulfoxylate, sodium ethylenediaminetetraacetate, ferrous sulfate, and dextrose. One or more types selected from the group consisting of may be used.

emulsifier

Additionally, the emulsifier used in the emulsion polymerization may include at least one emulsifier selected from the group consisting of anionic emulsifiers, cationic emulsifiers, and nonionic emulsifiers.

These emulsifiers are substances that have both hydrophilic and hydrophobic groups. During the emulsion polymerization process, they form a micelle structure and allow polymerization of each monomer to occur inside the micelle structure.

Emulsifiers commonly used in emulsion polymerization can be divided into anionic emulsifiers, cationic emulsifiers, and nonionic emulsifiers, and two or more types are sometimes used in combination in terms of polymerization stability in emulsion polymerization.

Specifically, in the case of the anionic emulsifier, sodium dodecyl diphenyl ether disulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium lauryl sulfate, sodium dodecyl benzene sulfonate, dioctyl sodium sulfosuccinate, etc. You can.

In addition, the nonionic emulsifier may be polyethylene oxide alkyl aryl ether, polyethylene oxide alkyl amine, or polyethylene oxide alkyl ester. These can be used alone or in combination of two or more types, and can be used by mixing an anionic emulsifier and a nonionic emulsifier. Although it may be more effective when used, the present invention is not necessarily limited to these types of emulsifiers.

And, the emulsifier is, for example, about 0.01 to about 10 parts by weight, about 1 to about 10 parts by weight, or about 3 to about 5 parts by weight, based on a total of 100 parts by weight of monomer components used in the production of the latex particles. It can be used as wealth.

If too much emulsifier is used, the particle size of the latex particles becomes smaller, which may cause the problem of lowering the adhesive strength of the binder. If too little emulsifier is used, the stability of polymerization in the emulsion polymerization reaction is reduced, and the resulting The stability of latex particles may also decrease.

menstruum

According to one embodiment of the invention, the binder composition for secondary battery electrodes may further include an aqueous solvent in addition to the above-described emulsified polymer particles, that is, latex particles.

At this time, in terms of stability and viscosity control of the latex particles, the aqueous solvent may be used in an amount of about 50 to about 1,000 parts by weight, preferably about 100 to about 300 parts by weight, based on 100 parts by weight of the latex particles, for example For example, based on the total amount of the binder composition, the total solid content (TSC) may be adjusted to about 9 to about 67 wt%.

If too little solvent is used, the stability of the latex particles may deteriorate, and if too much solvent is used, the viscosity may decrease and the adhesive strength of the binder may weaken, thereby reducing the overall performance of the battery. Deterioration problems may occur.

Electrode mixture and electrode

Meanwhile, according to another aspect of the present invention, a secondary battery electrode mixture comprising the above-described binder composition for secondary battery electrodes and an electrode active material is provided.

And, according to another aspect of the present invention, an electrode mixture layer containing such a secondary battery electrode mixture; A secondary battery electrode is provided, including an electrode current collector.

Except for the binder described above, the electrode active material, electrode current collector, etc. used in the electrode mixture and electrode of the present invention may each contain generally known components.

For example, the electrode mixture can be used to manufacture a cathode. That is, the electrode mixture may be a negative electrode mixture, and the electrode active material may be a negative electrode active material.

Here, the binder may be included in an amount of 1% to 10% by weight, specifically 1% to 5% by weight, based on the total weight (100% by weight) of the anode mixture. When this is satisfied, the content of the negative electrode active material can be relatively increased and the discharge capacity of the electrode can be further improved.

On the other hand, since the binder has excellent properties in terms of binding force, mechanical properties, etc., even when a graphite-based negative electrode active material is used as the negative electrode active material of the negative electrode mixture, as well as when a higher capacity negative electrode active material is used, between the negative electrode active material and the negative electrode active material, Cohesion between the negative electrode active material and the negative electrode current collector can be maintained, and expansion of the negative electrode active material can be suppressed due to its own mechanical properties.

As such, the binder is suitable for application not only with graphite-based negative electrode active materials but also with higher capacity negative electrode active materials, so in one embodiment of the present invention, the type of the negative electrode active material is not particularly limited.

Specifically, the negative electrode active material includes, for example, carbon and graphite materials such as natural graphite, artificial graphite, carbon fiber, and non-graphitizable carbon; Metals such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt, and Ti, which can be alloyed with lithium, and compounds containing these elements; Complexes of metals and their compounds with carbon and graphite materials; lithium-containing nitride; titanium oxide; Lithium titanium oxide and the like may be mentioned, but are not limited to these alone. Among them, carbon-based active materials, silicon-based active materials, tin-based active materials, or silicon-carbon-based active materials are more preferable, and they may be used alone or in combination of two or more.

The negative electrode current collector is generally made with a thickness of 3 to 500 ㎛. This negative electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, the surface of copper or stainless steel. Surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, like the positive electrode current collector, the bonding power of the negative electrode active material can be strengthened by forming fine irregularities on the surface, and can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

The negative electrode is manufactured by applying an electrode mixture containing a negative electrode active material and the binder onto a negative electrode current collector, followed by drying and rolling. If necessary, it can be manufactured by further adding a conductive material, filler, etc.

The conductive material is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The filler is selectively used as a component that suppresses expansion of the cathode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery. For example, it may be an olipine polymer such as polyethylene or polypropylene; Fibrous materials such as glass fiber and carbon fiber can be used.

Meanwhile, the electrode mixture is not limited to negative electrodes and can also be used to manufacture positive electrodes. That is, the electrode mixture may be a positive electrode mixture, and the electrode active material may be a positive electrode active material.

The positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ) or a compound substituted with one or more transition metals; Lithium manganese oxide with the formula Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _{2 ,} etc.; lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Chemical formula Li _1+a Fe _1-x M _x PO _4-b A _b (where M is at least one selected from the group consisting of Mn, Ni, Co, Cu, Sc, Ti, Cr, V and Zn, and A At least one selected from the group consisting of S, Se, F, Cl and I, and expressed as -0.5<a<0.5, 0=x<0.5, 0≤=b≤=0.1); Ni site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3; Chemical _{formula LiMn 2 - x M} a lithium manganese composite oxide expressed as Ni, Cu or Zn) or a lithium manganese composite oxide with a spinel structure expressed as LiNi _x Mn _2-x O ₄ ; Lithium-nickel-manganese-cobalt expressed by the chemical formula Li(Ni _p Co _q Mn _r1 )O2 (where 0＜p＜1, 0＜q＜1, 0＜r1＜1, p+q+r1=1) Lithium-based oxide, or expressed as Li(Ni _p1 Co _q1 Mn _r2 )O4 (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.) Nickel-manganese cobalt-based oxide, or Li(Ni _p2 Co _q2 Mn _r3 M _s2 )O2 (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, p2, q2, r3, and s2 are the atomic fractions of independent elements, respectively: 0＜p2＜1, 0＜q2＜1, 0＜r3＜1, 0＜s2＜1, p2+q2+r3+s2=1) Examples include, but are not limited to, lithium-nickel-cobalt-transition metal (M) oxide expressed as .

The positive electrode current collector is generally made to have a thickness of 3 to 500 ㎛. This positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel. A surface treated with carbon, nickel, titanium, silver, etc. may be used. The current collector can increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and can be in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

Among the cathode and the anode, a generally known binder may be used for the electrode in which the above-described binder is not used. Representative examples include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, Polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. can be used, but are not limited to these.

The negative electrode and the positive electrode can be manufactured by mixing an active material and a binder, and in some cases, a conductive material, a filler, etc. in a solvent to form a slurry-like electrode mixture, and applying this electrode mixture to each electrode current collector. Since this electrode manufacturing method is widely known in the field, detailed description will be omitted in this specification.

battery

Meanwhile, according to another aspect of the present invention, a secondary battery including the secondary battery electrode is provided. These batteries include, specifically, an anode; electrolyte; and a cathode.

The secondary battery may be implemented as a lithium secondary battery.

The lithium secondary battery can be manufactured by impregnating an electrode assembly including a positive electrode, a separator, and a negative electrode with a non-aqueous electrolyte.

The anode and the cathode are as described above.

In the case of the separator, any membrane commonly used in lithium batteries can be used as it separates the cathode and anode and provides a passage for lithium ions to move. That is, one that has low resistance to ion movement in the electrolyte and has excellent electrolyte moisturizing ability can be used. For example, it is selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of non-woven or woven fabric. For example, in lithium ion batteries, polyolefin-based polymer separators such as polyethylene and polypropylene are mainly used, and coated separators containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and can optionally be single-layer or multi-layer. It can be used as a structure.

In some cases, a gel polymer electrolyte may be coated on the separator to increase battery stability. Representative examples of such gel polymers include polyethylene oxide, polyvinylidene fluoride, and polyacrylonitrile.

However, when a solid electrolyte other than the non-aqueous electrolyte is used, the solid electrolyte may also serve as a separator.

The non-aqueous electrolyte may be a liquid electrolyte containing a non-aqueous organic solvent and a lithium salt. The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

Non-aqueous electrolytes, organic solid electrolytes, inorganic solid electrolytes, etc. are used as the non-aqueous electrolyte.

Examples of the non-aqueous electrolyte solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate. Bonate, gamma-butylo lactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxo Run, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxoren, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxy methane, di Aprotic organic solvents such as oxoran derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl pyropionate, and ethyl propionate. can be used.

The organic solid electrolyte includes, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, poly vinylidene fluoride, ion Polymers containing a dissociative group, etc. may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitride, halide, sulfate, etc. of Li such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ may be used.

The lithium salt is a material that is easily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiSCN, LiC(CF ₃ SO ₂ ) ₃ , (CF ₃ SO ₂ ) ₂ NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4 phenyl borate, etc. can be used.

In addition, the electrolyte solution contains, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, and nitroamine for the purpose of improving charge/discharge characteristics, flame retardancy, etc. Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. . In some cases, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be further included to provide incombustibility, and carbon dioxide gas may be further included to improve high-temperature preservation characteristics, and FEC (fluoro-ethylene carbonate), PRS (propene sultone), FPC (fluoro-propylene carbonate), etc. may be further included.

The lithium secondary battery according to the present invention can not only be used in battery cells used as a power source for small devices, but can also be used as a unit battery in medium to large-sized battery modules containing a plurality of battery cells.

In the specification of the present invention, a binder composition for a secondary battery has excellent properties in terms of binding force, mechanical properties, etc., while maintaining the structural stability of the electrode at high temperatures, thereby improving the performance of the secondary battery.

Hereinafter, the operation and effects of the invention will be described in more detail through specific examples of the invention. However, these examples are merely presented as examples of the invention and do not determine the scope of the invention rights.

<Example>

Example 1: Preparation of conjugated diene-based latex particles

In a pressure stirrer, 250 g of distilled water, 50 g of 1,3-butadiene, 34 g of styrene, 10 g of methyl methacrylate, 4 g of acrylic acid, 2 g of sodium acrylate, 0.4 g of sodium lauryl sulfate as an emulsifier, and potassium as a polymerization initiator. 0.5 g of persulfate was added to initiate the emulsion polymerization reaction. While sufficiently stirring, the condition was maintained at about 70° C. for 10 hours to obtain an emulsion-type binder with a solid content of about 40 wt%. As a pigment, 0.1 part by weight of copper phthalocyanine blue was added based on 100 parts by weight of the emulsion type binder and stirred for 1 hour to complete the final binder.

Comparative Example 1: Preparation of conjugated diene-based latex particles

Proceed in the same manner as Example 1 above, except that no pigment was used, An emulsion-type binder with a solid content of about 40 wt% was obtained.

Example 2: Preparation of acrylate-based latex particles

In a pressure stirrer, 70 g of butyl acrylate, 20 g of styrene, 5 g of acrylic acid, 5 g of hydroxy butylacrylate, 0.4 g of NaHCO ₃ as a buffer, and 0.4 g of sodium lauryl sulfate as an emulsifier were used, and the same amount of distilled water as the monomer component was added. After adding them, they were mixed and the temperature was raised to 75°C. Emulsion polymerization reaction was initiated by adding 0.5 g of ammonium persulfate as a polymerization initiator. While sufficiently stirring, conditions were maintained at about 75° C. for 6 hours to obtain an emulsion-type binder with a solid content of about 40 wt%. As a pigment, 0.1 part by weight of copper phthalocyanine blue was added based on 100 parts by weight of the emulsion type binder and stirred for 1 hour to complete the final binder.

Comparative Example 2: Production of acrylate-based latex particles

Except that the pigment was not used, the same procedure as Example 2 was performed to obtain an emulsion-type binder with a solid content of about 40 wt%.

Cathode mixture manufacturing

Using water as a dispersion medium, 10 kg of slurry was prepared by mixing 44.5 parts by weight of artificial graphite, 0.5 parts by weight of acetylene black, 0.5 parts by weight of carboxymethyl cellulose, and 54.5 parts by weight of water, based on a total of 100 parts by weight, and adding the slurry of the above example. A negative electrode mixture was prepared by mixing 0.23 g of binder.

cathode manufacturing

Using a comma coater, the cathode mixture was applied to a copper foil to a thickness of about 100 ㎛, dried in a dry oven at 80 ° C., and then rolled-pressed to a final thickness of 60 ㎛, making the cathode Obtained.

Dry state adhesion evaluation

The negative electrode plate prepared above was cut to a certain size and fixed on a glass slide, the current collector was peeled off, and the 180 degree peeling strength was measured. This was repeated 5 times, and the average values are summarized in Table 1 below.

Thermal stability evaluation

With the cathode, a 36 Ah pouch-type cell was manufactured. The cell was placed in a temperature-controlled chamber, and the temperature inside the chamber was raised to 150°C at a rate of 5°C per minute. The temperature was maintained at 150°C for about 30 minutes, then the temperature was raised to 155°C at a rate of 5°C per minute, and the temperature was maintained for about 30 minutes. Continuing to increase the temperature in the same manner was repeated until fire or explosion occurred, and the final temperature was recorded.

Capacity retention rate evaluation

The 36Ah pouch-type cell is stored in a chamber set at 25 degrees, connected to a charger and discharger, and charged under 1C CC/CV conditions in a voltage range of 2.5 to 4.15 V (CV terminates at 5% current), and discharged at 1C CC. was repeated. The rest period between charging and discharging and discharging and charging was 20 minutes.

Charging and discharging were repeated a total of 500 times, and the maintenance rate of the 500th discharge capacity compared to the initial capacity is summarized in Table 1 below.

Thermal stability evaluation Dry state adhesion
(Unit: gf/cm) Capacity maintenance rate
(%) Example 1 165℃ 42 97.5 Example 2 165℃ 29 96.7 Comparative Example 1 155℃ 39 97.0 Comparative Example 2 155℃ 25 96.1

Referring to the table above, it can be seen that the binder composition according to an embodiment of the present invention is superior to the comparative example in terms of thermal stability, dry state adhesion, and capacity retention rate. In particular, high temperature stability is superior to the comparative example. You can clearly see that it is about 10 degrees higher than that.

Accordingly, when manufacturing a battery by applying the binder composition according to an embodiment of the present invention, the structural stability of the electrode can be maintained at high temperature, the heat resistance of the secondary battery can be improved, and the overall battery performance under high temperature conditions can be improved. It is thought that it can be improved.

Claims (13)

Repeating units derived from conjugated diene monomers; A group consisting of a repeating unit derived from an aromatic vinyl monomer, a repeating unit derived from an alkyl (meth)acrylate monomer, a repeating unit derived from a (meth)acryl amide monomer, a repeating unit derived from a nitrile monomer, and a repeating unit derived from an unsaturated carboxylic acid monomer. Emulsified polymer particles comprising one or more repeating units selected from; and
Contains pigments,
The emulsified polymer particles include: A) conjugated diene-based latex particles; and B) acrylate-based latex particles,
The conjugated diene-based latex particles are, relative to the total weight of the conjugated diene-based latex particles,
a1) 40 to 65 wt% of the first repeating unit derived from a conjugated diene monomer;
a2) repeating units derived from aromatic vinyl monomers, a3) repeating units derived from alkyl (meth)acrylate monomers, and a4) repeating units derived from hydroxy alkyl (meth)acrylate monomers. 30 to 50 wt% of repeat units; and
a6) Contains 1 to 15 wt% of a third repeating unit derived from an unsaturated carboxylic acid monomer,
The acrylate-based latex particles are, relative to the total weight of acrylate-based latex particles,
b1) 50 to 80 wt% of a fourth repeating unit derived from an alkyl (meth)acrylate monomer; and
20 to 50 wt of at least one fifth repeating unit selected from the group consisting of b2) repeating units derived from aromatic vinyl monomers, b3) hydroxyalkyl (meth)acrylate monomers, and b4) repeating units derived from unsaturated carboxylic acid monomers Contains %,
95 to 99.99 wt% of emulsified polymer particles, based on the total weight of solids; and 0.01 to 5 wt% of pigment;
The pigment is a phthalocyanine pigment,
Binder composition for secondary battery electrodes.
delete delete delete delete delete delete delete According to paragraph 1,
A binder composition for secondary battery electrodes, further comprising an aqueous solvent.
A secondary battery electrode mixture comprising the binder composition for secondary battery electrodes of claim 1 and an electrode active material.
According to clause 10,
A secondary battery electrode mixture further containing a conductive material.
An electrode mixture layer comprising the secondary battery electrode mixture of claim 10; and
Containing an electrode current collector; Secondary battery electrode.
A secondary battery comprising the secondary battery electrode of claim 12.