KR20220087853A - Electrode binder composition for rechargeable battery and electrode mixture including the same - Google Patents

Abstract

The present invention relates to a binder composition for a secondary battery and an electrode mixture comprising the same. The binder composition for a secondary battery of the present invention, while having excellent properties in binding force and mechanical properties, etc., can maintain the structural stability of the electrode even in repeated charge and discharge cycles, it is possible to improve the overall performance of the secondary battery.

Description

Binder composition and electrode mixture for secondary batteries

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

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing.

In recent years, 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, with high energy density and operating potential, A lot of research has been done on a lithium secondary battery having a long cycle life and a low self-discharge rate, and it has also been commercialized and widely used.

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

In a lithium secondary battery, 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 the lithium secondary battery is manufactured by mixing the active material and the binder component, dispersing it in a solvent to make a slurry, and then applying it to the surface of the current collector to form a mixture layer.

In general, in a lithium secondary battery, charging and discharging are performed while repeating the process in which lithium ions of a positive electrode are inserted and detached from the negative electrode, and in this repeated process, the bond between the electrode active material or the conductive material is loosened, and the contact between particles As the resistance increases, the self-resistance of the electrode may also increase.

Therefore, the binder used for the electrode must be able to maintain excellent bonding strength between the electrode active material and the current collector, and to act as a buffer against the expansion and contraction of the electrode active material due to the insertion and desorption of lithium ions from the electrode. do.

In particular, in recent years, in order to increase the discharge capacity of the electrode, natural graphite having a theoretical discharge capacity of 372 mAh/g is often mixed with a material such as silicon, tin, and a silicon-tin alloy having a large discharge capacity. Accordingly, as the charging and discharging are repeated, the volume expansion rate of the material is significantly increased, which causes the anode material to be separated, and as a result, the capacity of the battery is rapidly reduced and the lifespan is shortened.

In addition, a lithium ion battery may have a swelling phenomenon that swells due to the gas generated during the decomposition of the electrolyte inside the battery. The ring phenomenon is accelerated, and there may be problems in that the stability of the battery is deteriorated.

Therefore, a binder and an electrode material that can implement excellent binding force to prevent separation between the electrode active materials or between the electrode active material and the current collector, while maintaining the structural stability of the electrode even in repeated charge and discharge cycles There is an urgent need for research on it.

An object of the present specification is to provide a binder composition for a secondary battery capable of maintaining structural stability of an electrode even in repeated charging and discharging cycles while having excellent properties in binding force and mechanical properties.

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

In addition, the present specification is to provide a secondary battery electrode including the secondary battery electrode mixture.

In addition, the present specification is to provide a secondary battery including the secondary battery electrode.

According to one aspect of the present invention, a core-shell structure including a conjugated diene-based core and an acrylate-based shell, wherein the shell includes a repeating unit derived from a cyclic carbonate-based monomer, an emulsion polymer having a core-shell structure A binder composition for a secondary battery, including particles, is provided.

The cyclic carbonate-based monomer may be represented by Formula 1 below.

[Formula 1]

In Formula 1, X is an alkylene having 2 or 3 carbon atoms, meaning that the structure is a cyclic carbonate, R is a substituent connected to carbon of the cyclic carbonate, hydrogen, or having 1 to 3 carbon atoms an alkyl group, and when R is an alkyl group having 1 to 3 carbon atoms, it may be substituted with 1 to 3 in the ring, Y is a simple bond or alkylene having 1 to 3 carbon atoms, and Z is (meth)acrylate group or vinyl group.

According to an embodiment of the present invention, the core of the emulsion polymer particles includes a repeating unit derived from a conjugated diene-based monomer, a repeating unit derived from an aromatic vinyl-based monomer, a repeating unit derived from an alkyl (meth)acrylate-based monomer, and an unsaturated carboxylic acid-based repeating unit. It may include a monomer-derived repeating unit.

In this case, the core of the emulsion polymer particles may contain from about 50 to about 100 parts by weight of the repeating unit derived from the aromatic vinyl-based monomer based on 100 parts by weight of the repeating unit derived from the conjugated diene-based monomer, and the lower limit thereof is about 50 parts by weight or more, or about 60 parts by weight or more, or about 65 parts by weight or more, and the upper limit thereof may be about 100 parts by weight or less, or about 90 parts by weight or less, or about 80 parts by weight or less.

And, the core of the emulsion polymer particles may include about 5 to about 50 parts by weight of the repeating unit derived from the alkyl (meth)acrylate-based monomer, based on 100 parts by weight of the repeating unit derived from the conjugated diene-based monomer, The lower limit may be about 5 parts by weight or more, or about 10 parts by weight or more, or about 15 parts by weight or more, and the upper limit may be about 50 parts by weight or less, or about 40 parts by weight or less, or about 30 parts by weight or less.

In addition, the core of the emulsion polymer particle may include about 1 to about 20 parts by weight of the repeating unit derived from the unsaturated carboxylic acid-based monomer, based on 100 parts by weight of the repeating unit derived from the conjugated diene-based monomer, and the lower limit thereof is It may be about 1 part by weight or more, or about 2 parts by weight or more, or about 4 parts by weight or more, and the upper limit thereof may be about 20 parts by weight or less, or about 18 parts by weight or less, or about 16 parts by weight or less.

According to another embodiment of the present invention, the shell of the emulsion polymer particle may include a repeating unit derived from an alkyl (meth)acrylate-based monomer and a repeating unit derived from an unsaturated carboxylic acid-based monomer.

In this case, the shell of the emulsion polymer particle may include about 1 to about 20 parts by weight of the repeating unit derived from the cyclic carbonate-based monomer, based on 100 parts by weight of the alkyl (meth)acrylate-based repeating unit, and the lower limit thereof may be about 1 part by weight or more, or about 1.5 parts by weight or more, or about 2 parts by weight or more, and the upper limit thereof may be about 20 parts by weight or less, or about 15 parts by weight or less, or about 12 parts by weight or less.

In addition, the shell of the emulsion polymer particles may have a ratio of repeating units derived from a cyclic carbonate-based monomer of about 1 to about 15 wt%, based on the total weight of the shell, and the lower limit thereof is about 1 wt% or more, or about 1.3 wt% or more, and the upper limit thereof may be about 15 wt% or less, or about 10 wt% or less, or less than about 8 wt%.

In this case, the shell of the emulsion polymer particle may include about 20 to about 70 parts by weight of the repeating unit derived from the unsaturated carboxylic acid-based monomer based on 100 parts by weight of the repeating unit derived from the alkyl (meth)acrylate-based monomer. and the lower limit thereof may be about 20 parts by weight or more, or about 25 parts by weight or more, or about 30 parts by weight or more, and the upper limit thereof may be about 70 parts by weight or less, or about 65 parts by weight or less, or about 60 parts by weight or less. have.

At this time, the shell of the emulsion polymer particles may further include, optionally, about 5 to about 50 parts by weight of the repeating unit derived from the aromatic vinyl-based monomer, based on 100 parts by weight of the repeating unit derived from the alkyl (meth)acrylate-based monomer. . The lower limit may be about 5 parts by weight or more, or about 10 parts by weight or more, or about 15 parts by weight or more, and the upper limit may be about 50 parts by weight or less, or about 40 parts by weight or less, or about 30 parts by weight or less.

Representative examples of the conjugated diene-based monomer include at least one selected from the group consisting of 1,3-butadiene, isoprene, chloroprene and piperylene, and preferably 1,3-butadiene.

And, the alkyl (meth) acrylate-based monomer is methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acryl rate, 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 include at least one selected from the group consisting of lauryl methacrylate, cetyl methacrylate, and stearyl methacrylate.

In addition, the aromatic vinyl-based monomer is styrene, α-methylstyrene, β-methylstyrene, p-t-butylstyrene, chlorostyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene and divinyl. It may include one or more selected from the group consisting of benzene.

In addition, the unsaturated carboxylic acid-based monomer is at least one 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. may include

And the shell of the emulsion polymer particles may include a cross-linkage formed by a cross-linking agent.

In this case, the crosslinking agent may be a compound including both an acryloyl group and an ethylenically unsaturated bond in a molecule.

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

In this case, the secondary battery electrode mixture may further include a conductive material.

On the other hand, according to another aspect of the present invention; An electrode mixture layer comprising the secondary battery electrode mixture described above; and an electrode current collector; A secondary battery electrode is provided.

On the other hand, according to another aspect of the present invention; A secondary battery is provided, including the secondary battery electrode described above.

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

In addition, the terminology used herein is used only to describe exemplary embodiments, and is not intended to limit the present invention.

The singular expression includes the plural expression unless the context clearly dictates otherwise.

In this specification, terms such as "comprises", "comprises" or "have" are used to describe embodied features, numbers, steps, components, or combinations thereof, and include one or more other features, numbers, or steps. , components, combinations or additions thereof are not excluded.

Also in this specification, when it is said that each layer or element is formed "on" or "over" each layer or element, it means that each layer or element is formed directly on each layer or element, or other It means that a layer or element may additionally be formed between each layer, on the object, on the substrate.

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

Hereinafter, the present invention will be described in detail.

First, according to one aspect of the present invention, a core-shell structure including a conjugated diene-based core and an acrylate-based shell, wherein the shell includes a repeating unit derived from a cyclic carbonate-based monomer, a core-shell structure of A binder composition for a secondary battery is provided, comprising emulsified polymer particles.

An electrode binder used in a lithium secondary battery is an essential component for binding an electrode active material and a current collector, and various materials may be used for stable binding of each component and improving battery performance. However, certain components added to the binder may improve some performance, such as binding force, while at the same time reducing other performances by interaction with an electrolyte (eg, electrolyte impregnation), a trade-off may occur.

The inventors of the present invention, in a binder composition for a secondary battery comprising an emulsion of latex particles prepared by emulsion polymerization of a conjugated diene-based monomer and an acrylate-based monomer, implement a core-shell structure, but a second emulsification for shell formation When a cyclic carbonate-based monomer having a specific structure is additionally used during the polymerization process, the adhesive strength of the binder is greatly improved to prevent desorption between electrode active materials or between electrode active materials and the current collector, and at the same time realize stable binding. , found that by minimizing side effects such as electrolyte impregnation, it is possible to maintain excellent performance of the battery, such as charge capacity, and completed the present invention.

The binder composition for a secondary battery 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 each latex particle. have.

monomer

First, the latex particles may have a core-shell structure as described above, and these latex particles may be separately prepared through a first polymerization step for forming a core and a second polymerization step for forming a shell. At this time, it may be preferable that the core and the shell are composed of different components in consideration of particle stability and characteristics as a battery binder, which will be described later.

core

In the first emulsion polymerization for producing the core of the latex particles, a conjugated diene-based monomer is used, and thus, the core of the latex particle includes a repeating unit derived from the conjugated diene-based monomer.

When such a conjugated diene-based monomer is included as a component of the latex particles, the binder prepared therefrom can suppress the electrolyte swelling phenomenon at high temperature, and have elasticity due to the rubber component, thereby reducing the thickness of the electrode and , it can serve to not only reduce the gas generation phenomenon, but also improve the adhesive force so that the binding force between the electrode active material and the current collector can be maintained.

A representative example of the conjugated diene-based monomer may be at least one selected from the group consisting of 1,3-butadiene, isoprene, chloroprene and piperylene, preferably 1,3-butadiene.

And, in the first emulsion polymerization for preparing the core of the latex particle, an aromatic vinyl-based monomer may be further used, and thus, the latex particle may further include a repeating unit derived from the aromatic vinyl-based monomer. .

The aromatic vinyl monomer is 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, preferably styrene.

In this case, the core of the emulsion polymer particles may contain from about 50 to about 100 parts by weight of the repeating unit derived from the aromatic vinyl-based monomer based on 100 parts by weight of the repeating unit derived from the conjugated diene-based monomer, and the lower limit thereof is about 50 parts by weight or more, or about 60 parts by weight or more, or about 65 parts by weight or more, and the upper limit thereof may be about 100 parts by weight or less, or about 90 parts by weight or less, or about 80 parts by weight or less.

And, in the first emulsion polymerization for preparing the core of the latex particles, an alkyl (meth) acrylate-based monomer may be further used, and accordingly, the core of the latex particle is formed from an alkyl (meth) acrylate-based monomer. It may further include a repeating unit derived from it.

When the alkyl (meth) acrylate-based monomer is used, the prepared electrode has a relatively high degree of swelling, and thus the resistance of the electrode may be reduced and ionic conductivity may be increased.

The alkyl (meth) acrylate-based monomer is methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, 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, lauryl It may include at least one selected from the group consisting of methacrylate, cetyl methacrylate, and stearyl methacrylate.

And, the core of the emulsion polymer particles may include about 5 to about 50 parts by weight of the repeating unit derived from the alkyl (meth)acrylate-based monomer, based on 100 parts by weight of the repeating unit derived from the conjugated diene-based monomer, The lower limit may be about 5 parts by weight or more, or about 10 parts by weight or more, or about 15 parts by weight or more, and the upper limit may be about 50 parts by weight or less, or about 40 parts by weight or less, or about 30 parts by weight or less.

And, in the first emulsion polymerization for producing the core of the latex particles, an unsaturated carboxylic acid-based monomer may be further used, and accordingly, the core of the latex particles is a repeating unit derived from the unsaturated carboxylic acid-based monomer. may further include.

The unsaturated carboxylic acid-based monomer is a group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, and nadic acid It may include one or more selected from.

In addition, the core of the emulsion polymer particle may include about 1 to about 20 parts by weight of the repeating unit derived from the unsaturated carboxylic acid-based monomer, based on 100 parts by weight of the repeating unit derived from the conjugated diene-based monomer, and the lower limit thereof is It may be about 1 part by weight or more, or about 2 parts by weight or more, or about 4 parts by weight or more, and the upper limit thereof may be about 20 parts by weight or less, or about 18 parts by weight or less, or about 16 parts by weight or less.

If too much of the unsaturated carboxylic acid-based monomer is used, there may be a problem in that the generation of aggregates increases during the polymerization process, and when the unsaturated carboxylic acid-based monomer is used too little, the electrolyte impregnability of the binder to be prepared later increases. Problems may arise.

In addition, in the emulsion polymerization for producing the latex particles, hydroxyalkyl (meth)acrylate-based monomers or nitrile-based monomers may be further used, and accordingly, the latex particles include repeating units derived from these monomers can do.

shell

In the second emulsion polymerization for producing the shell of the latex particles, an alkyl (meth) acrylate-based monomer is used, and accordingly, the shell of the latex particles is a repeating unit derived from the alkyl (meth) acrylate-based monomer. includes

Specific details of the alkyl (meth) acrylate-based monomer are the same as described above.

And, in the second emulsion polymerization for preparing the shell of the latex particles, a cyclic carbonate-based monomer is further used, and thus, the latex particles may further include a repeating unit derived from the cyclic carbonate-based monomer. have.

The cyclic carbonate-based monomer may be represented by Formula 1 below.

[Formula 1]

In Formula 1, X is an alkylene having 2 or 3 carbon atoms, meaning that the structure is a cyclic carbonate, R is a substituent connected to carbon of the cyclic carbonate, hydrogen, or having 1 to 3 carbon atoms an alkyl group, and when R is an alkyl group having 1 to 3 carbon atoms, it may be substituted with 1 to 3 in the ring, Y is a simple bond or alkylene having 1 to 3 carbon atoms, and Z is (meth)acrylate group or vinyl group.

In the structure of Formula 1, the terminal vinyl group participates in the above-described emulsion polymerization to form a copolymer. Accordingly, the fourth repeating unit derived from the monomer compound represented by Formula 1 may be represented by Formula 1-1 or Formula 1-2 below.

[Formula 1-1]

[Formula 1-2]

In Formulas 1-1 and 1-2, X, Y, and R are as defined in Formula 1, and R ₁ is hydrogen or methyl.

In addition, in the repeating unit, the cyclic carbonate group may exist in a ring-opened state in the latex particles or in a state in which a cross-linkage is formed with another repeating unit.

In the repeating unit as described above, a cyclic carbonate group is positioned at the end. This cyclic carbonate group, in particular, has the same structure as ethylene carbonate or propylene carbonate, which are often used as electrolytes, and can help the movement of lithium ions in the electrode. However, since the additional reaction with ethylene carbonate or propylene carbonate does not proceed due to steric hindrance, the side effect of increasing the electrolyte impregnation property can be relatively suppressed, and the overall characteristics of the battery can be improved.

In addition, the terminal cyclic carbonate group as described above may form a crosslinking bonding structure through interaction with other functional groups after emulsion polymerization or emulsion polymerization.

That is, at least some of the cyclic carbonate groups included in the fourth repeating unit in the latex particles may exist in a state in which a cross-linkage is formed.

In addition, in the repeating unit as described above, a cyclic carbonate group is positioned at the terminal. These cyclic carbonate groups can form cross-links with other repeating units present in the core or shell, thereby further improving the structural stability of the latex particles.

In this aspect, the shell of the emulsion polymer particle may include about 1 to about 20 parts by weight of the repeating unit derived from the cyclic carbonate-based monomer based on 100 parts by weight of the alkyl (meth)acrylate-based repeating unit, and the The lower limit may be about 1 part by weight or more, or about 1.5 parts by weight or more, or about 2 parts by weight or more, and the upper limit may be about 20 parts by weight or less, or about 15 parts by weight or less, or about 12 parts by weight or less.

In addition, the shell of the emulsion polymer particles may have a ratio of repeating units derived from a cyclic carbonate-based monomer of about 1 to about 15 wt%, based on the total weight of the shell, and the lower limit thereof is about 1 wt% or more, or about 1.3 wt% or more, and the upper limit thereof may be about 15 wt% or less, or about 10 wt% or less, or less than about 8 wt%.

If the content of the repeating unit derived from the cyclic carbonate-based monomer in the latex particles is too low, the above-mentioned advantages may not be realized, and if the content is too high, the affinity with the electrolyte is too high, so that the electrolyte is impregnated The performance may increase and the overall performance of the battery may be deteriorated due to increased interaction with the electrolyte.

And, in the second emulsion polymerization for producing the shell of the latex particles, an unsaturated carboxylic acid-based monomer may be further used, and thus, the shell of the latex particles is a repeating unit derived from the unsaturated carboxylic acid-based monomer. may further include.

Specific details of the unsaturated carboxylic acid-based monomer are the same as described above.

In this case, the shell of the emulsion polymer particle may include about 20 to about 70 parts by weight of the repeating unit derived from the unsaturated carboxylic acid-based monomer based on 100 parts by weight of the repeating unit derived from the alkyl (meth)acrylate-based monomer. and the lower limit thereof may be about 20 parts by weight or more, or about 25 parts by weight or more, or about 30 parts by weight or more, and the upper limit thereof may be about 70 parts by weight or less, or about 65 parts by weight or less, or about 60 parts by weight or less. have.

When too much of the unsaturated carboxylic acid-based monomer is used, the occurrence of aggregates increases during the polymerization process, and the glass transition temperature of the polymer increases, which may cause a problem of electrode detachment, and the unsaturated carboxylic acid-based monomer If too little is used, there may be a problem in that the electrolyte impregnability of the binder to be manufactured later increases.

In addition, the shell of the emulsion polymer particles may further include about 5 to about 50 parts by weight of an aromatic vinyl-based monomer-derived repeating unit based on 100 parts by weight of the alkyl (meth)acrylate-based repeating unit-derived repeating unit. The lower limit may be about 5 parts by weight or more, or about 10 parts by weight or more, or about 15 parts by weight or more, and the upper limit may be about 50 parts by weight or less, or about 40 parts by weight or less, or about 30 parts by weight or less.

emulsion polymerization

These latex particles can be prepared by a generally known emulsion polymerization method, and, as described above, is prepared in a core-shell form. In order to prepare the latex particles in a core-shell form, the emulsion polymerization is a first emulsion polymerization to form a core and a second emulsion polymerization to form a shell surrounding the outer surface of the core, and may be carried out at least twice. have.

At this time, in each of the first and second emulsion polymerizations, the polymerization temperature and the polymerization time may be appropriately determined depending on the case. For example, the polymerization temperature may be from about 50 °C to about 200 °C, or from about 50 °C to about 100 °C, and the polymerization time may be from about 0.5 hours to about 20 hours, or from about 1 to about 10 hours.

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

In addition, an activator may be further included to promote the initiation of the reaction of the peroxide together with the polymerization initiator, and such activators include sodium formaldehyde sulfoxylate, sodium ethylenediaminetetraacetate, ferrous sulfate, and dextrose. At least one selected from the group consisting of may be used.

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.

Such an emulsifier is a material having a hydrophilic group and a hydrophobic group at the same time, and during the emulsion polymerization process, a micelle structure is formed, and polymerization of each monomer can occur inside the micellar structure.

Emulsifiers generally used in emulsion polymerization may be divided into anionic emulsifiers, cationic emulsifiers, and nonionic emulsifiers, and two or more types may be mixed in view 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. can

In addition, the nonionic emulsifier may be polyethylene oxide alkyl aryl ether, polyethylene oxide alkyl amine, or polyethylene oxide alkyl ester, which may be used alone or in combination of two or more, and by mixing an anionic emulsifier and a nonionic emulsifier It may be more effective when used, but the present invention is not necessarily limited to the type of such emulsifiers.

And, the emulsifier, for example, based on 100 parts by weight of the total monomer component used in the preparation of the latex particles, about 0.01 to about 10 parts by weight, about 0.05 to about 10 parts by weight, or about 0.1 to about 5 parts by weight can be used as wealth.

When the emulsifier is used too much, the particle size of the latex particles becomes small, which may cause a problem that the adhesive strength of the binder is lowered. The stability of the latex particles may also be deteriorated.

According to an embodiment of the present invention, the core-shell latex particles prepared by the above method may have an average particle diameter (Intensity average particle size, Di) of about 50 to about 200 nm.

menstruum

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

The solvent or material used as the dispersion medium is not particularly limited, and for example, water; alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, and hexanol; ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, cyclopentanone, and cyclohexanone; Methyl ethyl ether, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, diisobutyl ether, di-n-amyl ether, diisoamyl ether, methyl propyl ether, methyl isopropyl ether, methyl butyl ether, ethers such as ethyl isoamyl ether and tetrahydrofuran; lactones such as γ-butyrolactone and δ-butyrolactone; lactams such as β-lactam; Cyclic aliphatic, such as cyclopentane, cyclohexane, and cycloheptane; aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, propylbenzene, isopropylbenzene, and butylbenzene; aliphatic hydrocarbons such as heptane, octane, nonane, and decane; chain and cyclic amides such as dimethylformamide and N-methylpyrrolidone; esters such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, and methyl benzoate; etc. are mentioned, Among these, it is preferable in view of a process to use the dispersion medium with a boiling point of 80 degreeC or more, Preferably 85 degreeC or more.

In this case, the 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, in terms of stability and viscosity control of the latex particles, for example, , based on the total amount of the binder composition, a total solid content (TSC) may be used to be adjusted to about 5 to about 70% by weight.

When the solvent is used too little, there may be a problem that the stability of the latex particles is lowered, and when the solvent is used too much, the viscosity is lowered, the coating property may be weakened, and thus the overall performance of the battery is lowered problems may arise.

Electrode mixture and electrode

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

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

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

For example, the electrode mixture may be used for manufacturing the negative electrode. 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 wt% to 10 wt%, specifically 1 wt% to 5 wt%, based on the total weight (100 wt%) of the negative electrode mixture. When this is satisfied, the content of the negative active material may be relatively increased, and the discharge capacity of the electrode may be further improved.

On the other hand, since the binder has excellent properties in binding force and mechanical properties, etc., even if a graphite-based negative active material is used as the negative active material of the negative electrode mixture, as well as a negative active material having a higher capacity than that, between the negative active material and the negative active material, The binding force 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 by its own mechanical properties.

As such, the binder is suitable to be applied not only with the graphite-based negative active material but also with the negative active material having a higher capacity than that, in one embodiment of the present invention, the type of the negative active material is not particularly limited.

Specifically, the negative 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, Ti and the like capable of alloying with lithium and compounds containing these elements; composites of metals and their compounds with carbon and graphite materials; lithium-containing nitride; titanium oxide; Although lithium titanium oxide etc. are mentioned, It is not limited only to these. Among them, a carbon-based active material, a silicon-based active material, a tin-based active material, or a silicon-carbon-based active material is more preferable, and these may be used alone or in combination of two or more.

The negative electrode current collector is generally made to a thickness of 3 to 500 μm. Such a negative current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel. Carbon, nickel, titanium, silver, etc. surface-treated, aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, the bonding strength of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven body, and the like.

The negative electrode is prepared by coating an electrode mixture including a negative electrode active material and the binder on an anode current collector, drying and rolling, and, if necessary, may be prepared by further adding a conductive material, a filler, and the like.

The conductive material is not particularly limited as long as it has conductivity without causing a chemical change 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 nanotubes, carbon fibers, and metal fibers; 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 optionally used as a component for suppressing the expansion of the negative electrode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. A fibrous material such as glass fiber or carbon fiber may be used.

On the other hand, the electrode mixture is not limited to the negative electrode, and may be used in the preparation of the positive electrode. 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 active material may include a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Formula Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; 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 ; 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 is S, Se, F, Cl, and any one or more selected from the group consisting of I, -0.5<a<0.5, 0≤x<0.5, 0≤b≤0.1) a lithium iron phosphate system; Ni site-type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn _2-x M _x O ₂ (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1), Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu, or Zn) or lithium manganese composite oxide having a spinel structure represented by LiNi _x Mn _2-x O ₄ ; Lithium-nickel-manganese-cobalt represented by the formula Li(Ni _p Co _q Mn _r1 )O2 (where 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) based oxide, or Li(Ni _p1 Co _q1 Mn _r2 )O4 (here, 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.) Nickel-manganese cobalt 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 atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1) and lithium-nickel-cobalt-transition metal (M) oxide represented by , but is not limited thereto.

The positive electrode current collector is generally made to have a thickness of 3 to 500 μm. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel. Carbon, nickel, titanium, silver, etc. may be used on the surface of the surface-treated. The current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface thereof, and various forms such as a film, sheet, foil, net, porous body, foam body, and non-woven body are possible.

Among the negative electrode and the positive electrode, a generally known binder may be used for the electrode in which the above-described binder is not used. Representative examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, Polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or the like may be used, but is not limited thereto.

The negative electrode and the positive electrode may be prepared by mixing an active material and a binder, in some cases, a conductive material, a filler, and the like in a solvent to prepare a slurry-like electrode mixture, and applying the electrode mixture to each electrode current collector. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof will be omitted herein.

battery

Meanwhile, according to another aspect of the present invention, there is provided a secondary battery including the secondary battery electrode. Such a battery, specifically, a positive electrode; electrolyte; and a negative electrode.

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

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

The positive electrode and the negative electrode are the same as described above.

In the case of the separator, any one commonly used in lithium batteries may be used as it separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. That is, a low-resistance to ion movement of the electrolyte and excellent electrolyte moisture content may be used. For example, it may be selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of a nonwoven fabric or a woven fabric. For example, a polyolefin-based polymer separator such as polyethylene or polypropylene is mainly used for lithium ion batteries, and a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and optionally single-layer or multi-layer structure can be used.

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

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 including 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.

As the non-aqueous electrolyte, a non-aqueous electrolyte, an organic solid electrolyte, an inorganic solid electrolyte, and the like are used.

Examples of the non-aqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate. Bonate, gamma-butylolactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1, 3-dioxolane, 4- methyl-1, 3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives; Aprotic organic solvents such as sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl pyropionate, and ethyl propionate may be used. .

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, ions A polymer containing a sexually dissociating group or the like can 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 , Nitrides, halides, sulfates, etc. of Li such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ and the like may be used.

The lithium salt is a material readily 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, chloroborane lithium, lower aliphatic lithium carboxylate, 4 phenyl lithium borate, and the like can be used.

In addition, for the purpose of improving charge and discharge characteristics, flame retardancy, etc. in the electrolyte, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. may be added. have. In some cases, in order to impart incombustibility, a halogen-containing solvent such as carbon tetrachloride and ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics, and FEC (fluoro-ethylene) carbonate), propene sultone (PRS), and fluoro-propylene carbonate (FPC) can be further included.

The lithium secondary battery according to the present invention may be used not only in a battery cell used as a power source for a small device, but also as a unit battery in a medium/large battery module including a plurality of battery cells.

The binder composition for a secondary battery of the present invention can maintain the structural stability of the electrode even in repeated charging and discharging cycles while having excellent characteristics in binding force and mechanical properties, etc., thereby improving the performance of the secondary battery.

Hereinafter, through specific examples of the invention, the operation and effect of the invention will be described in more detail. However, these embodiments are merely presented as an example of the invention, and the scope of the invention is not defined thereby.

Electrolyte impregnation measurement

For the binders obtained in Examples and Comparative Examples, the electrolyte impregnation properties were measured as follows.

20 g of the binder obtained in the following Examples and Comparative Examples was taken, applied to a mold release-treated square, dried at 25 ° C. for 24 hours, and dried at 80 ° C. for 24 hours, and then peeled to prepare a film. The specimen was cut in a rectangular shape with a long horizontal length and the correct horizontal length was measured. (Ma)

After the length measurement was completed, the film was immersed in about 15 g of an electrolyte at 25° C. for 48 hours, and then the transverse length of the immersed specimen was measured. (Mb)

At this time, the electrolyte solution was prepared by mixing ethylene carbonate / ethyl methyl carbonate (mixing volume ratio of EC / EMC = 3/7).

The electrolyte impregnation property was calculated through Equation 1 below.

[Equation 1]

Electrolyte impregnation property (%) = ((Mb/Ma) ³ -1) * 100

particle size measurement

After diluting 0.02 g of the binder obtained in Examples and Comparative Examples in 20 g of distilled water, an average particle diameter (Di) value was measured using a particle size analyzer (NICOMP 380, Entegris). (Intensity average partition size, Di)

<Example 1>

Latex Particle Core Preparation - First Polymerization

As the monomer, 50 g of 1,3-butadiene, 35 g of styrene, 10 g of methyl methacrylate, and 5 g of a mixture of acrylic acid and itaconic acid in a ratio of 5:5 were used.

As a solvent, about 170 parts by weight of water was used based on 100 parts by weight of the total monomer components.

In a nitrogen-substituted polymerization reactor, about 3 parts by weight of sodium lauryl sulfate based on 100 parts by weight of a total of 100 parts by weight of the monomer components as water, the monomer, and the emulsifier component is added, and the temperature is raised to about 75° C., and then, as a polymerization initiator, 0.005 mol Potassium persulfate was added to initiate emulsion polymerization.

While maintaining the temperature at about 75° C., the reaction was carried out for about 7 hours to obtain a binder in the form of an emulsion.

Latex Particle Shell Preparation - Second Polymerization

As a monomer, n-butyl acrylate 68.5 g, methacrylic acid 25 g, acrylic acid 4.9 g, glycerol carbonate methacrylate ((2-oxo-1,3-dioxolan-4-yl)methyl methacrylate) 1.5 g, allyl 0.1 g of methacrylate was used.

In a nitrogen-substituted polymerization reactor, water, 400 g of the core binder prepared in the first polymerization, about 0.2 parts by weight of polyoxyethylene lauryl ether sulfate based on 100 parts by weight of a total of 100 parts by weight of the monomer component as the monomer, and the emulsifier component, and , while maintaining the temperature at about 80 °C, 0.35 parts by weight of ammonium persulfate relative to 100 parts by weight of the monomer component was added as a polymerization initiator to initiate emulsion polymerization.

While maintaining the temperature at about 80° C., the reaction was carried out for about 4 hours to obtain a binder in the form of an emulsion including latex particles having a core-shell structure. The pH was adjusted to 7.5 using an aqueous sodium hydroxide solution.

average particle diameter (Di) = 75 nm; Electrolyte impregnability = 36 %

<Example 2>

In the second polymerization in Example 1, n-butyl acrylate 67 g, methacrylic acid 25 g, acrylic acid 4.9 g, glycerol carbonate methacrylate ((2-oxo-1,3-dioxolan-4-yl) as a monomer The same procedure was followed except that 3 g of methyl methacrylate) and 0.1 g of allyl methacrylate were used to obtain an emulsion-type binder.

average particle diameter (Di) = 76 nm; Electrolyte impregnability = 38 %

<Example 3>

In the second polymerization in Example 1, as a monomer, 63 g of n-butyl acrylate, 25 g of methacrylic acid, 4.9 g of acrylic acid, and glycerol carbonate methacrylate ((2-oxo-1,3-dioxolan-4-yl ) The same procedure was followed except that 7 g of methyl methacrylate and 0.1 g of allyl methacrylate were used to obtain an emulsion-type binder.

average particle diameter (Di) = 76 nm; Electrolyte impregnability = 40 %

<Example 4>

In the second polymerization in Example 1, as a monomer, 68 g of n-butyl acrylate, 25 g of methacrylic acid, 4.9 g of acrylic acid, and vinyl ethylene carbonate (4-(vinyloxymethyl)-1,3-dioxolan-2-one) The same procedure was followed except that 2 g and 0.1 g of allyl methacrylate were used to obtain a binder in the form of an emulsion.

average particle diameter (Di) = 75 nm; Electrolyte impregnability = 35 %

<Example 5>

In the second polymerization in Example 1, as a monomer, 65 g of n-butyl acrylate, 25 g of methacrylic acid, 4.9 g of acrylic acid, and vinyl ethylene carbonate (4-(vinyloxymethyl)-1,3-dioxolan-2-one) 5 g, and 0.1 g of allyl methacrylate was used in the same manner to obtain a binder in the form of an emulsion.

average particle diameter (Di) = 77 nm; Electrolyte impregnability 38%

<Comparative Example 1>

During the second polymerization in Example 1, the same procedure was followed except that 70 g of n-butyl acrylate, 25 g of methacrylic acid, 4.9 g of acrylic acid, and 0.1 g of allyl methacrylate were used as monomers, and the emulsion form A binder was obtained.

average particle diameter (Di) 76 nm; Electrolyte impregnability 33%

<Reference Example 2>

In the second polymerization in Example 1, as a monomer, 69 g of n-butyl acrylate, 25 g of methacrylic acid, 4.9 g of acrylic acid, glycerol carbonate methacrylate ((2-oxo-1,3-dioxolan-4-yl ) The same procedure was followed except that 1 g of methyl methacrylate) and 0.1 g of allyl methacrylate were used to obtain an emulsion-type binder.

average particle diameter (Di) 75 nm; Electrolyte impregnability 35%

<Reference example 3>

In the second polymerization in Example 1, as a monomer, n-butyl acrylate 60 g, methacrylic acid 25 g, acrylic acid 4.9 g, glycerol carbonate methacrylate ((2-oxo-1,3-dioxolan-4-yl ) The same procedure was followed except that 10 g of methyl methacrylate) and 0.1 g of allyl methacrylate were used to obtain an emulsion-type binder.

average particle diameter (Di) = 77 nm; Electrolyte impregnability 45%

<Reference Example 4>

In the second polymerization in Example 4 , as a monomer, n-butyl acrylate 69 g, methacrylic acid 25 g, acrylic acid 4.9 g, vinyl ethylene carbonate (4-(vinyloxymethyl)-1,3-dioxolan-2-one) 1 g and 0.1 g of allyl methacrylate were used in the same manner except that an emulsion-type binder was obtained.

average particle diameter (Di) 76 nm; Electrolyte impregnability 33%

<Reference example 5>

In the second polymerization in Example 1, as a monomer, 62 g of n-butyl acrylate, 25 g of methacrylic acid, 4.9 g of acrylic acid, and vinyl ethylene carbonate (4-(vinyloxymethyl)-1,3-dioxolan-2-one) 8 g and 0.1 g of allyl methacrylate were used in the same manner except that an emulsion-type binder was obtained.

average particle diameter (Di) = 76 nm; Electrolyte impregnability 41%

Preparation of negative electrode mixture (Examples 1 to 5; Comparative Example 1; and Reference Examples 2 to 5)

Using water as a dispersion medium, 81.2 g of artificial graphite, 14.3 g of silicon oxide, 1.0 g of acetylene black, 2.3 g of the binder prepared above, and 1.2 g of carboxymethyl cellulose as a thickener were mixed based on the weight of 100 g of total solid content using water as a dispersion medium, and the total solid content was A slurry for a negative electrode was prepared so as to be 42 wt%.

Preparation of negative electrode mixture (Example 2-1; Comparative Example 1-1)

<Example 2-1>

Using water as a dispersion medium, based on the total solid content of 100 g by weight, 66.8 g of artificial graphite, 28.7 g of natural graphite, 1.0 g of acetylene black, 2.5 g of the binder prepared in Example 2 above, and 1.0 g of carboxymethyl cellulose as a thickener were mixed and , a slurry for a negative electrode was prepared so that the total solid content was 42 wt%.

<Comparative Example 1-1>

Using water as a dispersion medium, based on the total solid content of 100 g by weight, 66.8 g of artificial graphite, 28.7 g of natural graphite, 1.0 g of acetylene black, 2.5 g of the binder prepared in Comparative Example 1 above, and 1.0 g of carboxymethyl cellulose as a thickener were mixed and , a slurry for a negative electrode was prepared so that the total solid content was 42 wt%.

Cathode manufacturing

Using a comma coater, the negative electrode mixture was applied to a thickness of about 130 μm on copper foil, dried in a dry oven at 80° C. for 10 minutes, and then roll-pressed to a final thickness of 95 μm. After that, it was dried in a vacuum oven at 120° C. for 12 hours to obtain a negative electrode.

Coin cell manufacturing

A CR2032-type coin cell was manufactured by punching out the dry negative electrode and 150 μm lithium foil in a circle, in which case ethylene carbonate/ethylmethyl carbonate (EC/EMC) containing a porous polyethylene-based separator and 1 M lithium hexafluorophosphate (LiPF6) of mixed volume ratio = 3/7) mixed electrolyte was used.

Electrode adhesion test

In order to measure the adhesive force between the electrode mixture and the current collector, the surface of each of the electrodes prepared in Examples, Reference Examples, and Comparative Examples was cut and fixed on a slide glass, and 180 degree peel strength was measured while peeling off the current collector. .

After three or more measurements for each electrode, an average value was obtained.

life test

A charge/discharge experiment was performed on the battery prepared above. First, a charge/discharge test was performed three times with a charge-discharge current density of 0.1C, a charge-end voltage of 1.5 V (Li/Li+), and a final discharge voltage of 0.006 V (Li/Li+). Subsequently, a charge/discharge test was performed 30 times at a charge/discharge current density of 0.2 C, a charge end voltage of 1.5 V (Li/Li+), and a discharge end voltage of 0.006 V (Li/Li+). All the charging was performed with a constant current/constant voltage, and the final current of the constant voltage charging was set to 0.005C. After completing the test for a total of 33 cycles, the charging/discharging efficiency of the third cycle was obtained. Then, a capacity ratio obtained by dividing the charging capacity of 33 cycles by the charging capacity of 4 cycles was calculated and regarded as the capacity retention rate. These results are shown in the table below.

Film properties Electrode characteristics Battery characteristics Electrolyte impregnation (%) Adhesion (gf/cm) Capacity retention rate (%, 30 cycles) Example 1 36 19 78 Example 2 38 17 84 Example 2-1 - 37 - Example 3 40 16 77 Example 4 35 18 84 Example 5 38 17 83 Comparative Example 1 33 19 66 Comparative Example 1-1 - 25 - Reference Example 2 35 18 74 Reference Example 3 45 12 60 Reference Example 4 33 19 78 Reference Example 5 41 15 52

Referring to Table 1, first, when Example 2-1 and Comparative Example 1-1 are compared, it can be clearly seen that the adhesive strength of the Example is improved by about 50% compared to the Comparative Example.

In addition, in the case of other Examples or Reference Examples, a carbonate-based monomer having a structure similar to that of a carbonate-based electrolyte component used as an electrolyte was used to prepare a binder, and even though the charge/discharge capacity retention rate was greatly improved, the increase in electrolyte impregnation property compared to Comparative Examples It can be clearly seen that there is some degree of suppression.

Accordingly, when the binder of the above embodiment is applied to a secondary battery, it is thought that electrode expansion can be effectively suppressed during repeated charging and discharging processes.

Claims (16)

A core-shell structure including a conjugated diene-based core and an acrylate-based shell, wherein the shell includes emulsified polymer particles of a core-shell structure including repeating units derived from cyclic carbonate-based monomers, for secondary batteries binder composition.
According to claim 1,
The cyclic carbonate-based monomer is represented by the following formula (1), a binder composition for a secondary battery:
[Formula 1]

In Formula 1, X is an alkylene having 2 or 3 carbon atoms, meaning that the structure is a cyclic carbonate, R is a substituent connected to carbon of the cyclic carbonate, hydrogen, or having 1 to 3 carbon atoms an alkyl group, and when R is an alkyl group having 1 to 3 carbon atoms, it may be substituted with 1 to 3 in the ring, Y is a simple bond or alkylene having 1 to 3 carbon atoms, and Z is (meth)acrylate group or vinyl group.
According to claim 1,
The core of the emulsion polymer particles comprises a repeating unit derived from a conjugated diene-based monomer, a repeating unit derived from an aromatic vinyl-based monomer, a repeating unit derived from an alkyl (meth)acrylate-based monomer, and a repeating unit derived from an unsaturated carboxylic acid-based monomer, Binder composition for secondary batteries.
4. The method of claim 3,
The core of the emulsion polymer particles, with respect to 100 parts by weight of the repeating unit derived from the conjugated diene-based monomer, comprising 50 to 100 parts by weight of the aromatic vinyl-based monomer-derived repeating unit, a binder composition for a secondary battery.
4. The method of claim 3,
The core of the emulsion polymer particle, with respect to 100 parts by weight of the repeating unit derived from the conjugated diene-based monomer, the alkyl (meth) acrylate-based monomer-derived repeating unit comprising 5 to 50 parts by weight, a binder composition for a secondary battery.
4. The method of claim 3,
The core of the emulsion polymer particle, with respect to 100 parts by weight of the repeating unit derived from the conjugated diene-based monomer, comprises 1 to 20 parts by weight of the repeating unit derived from the unsaturated carboxylic acid-based monomer, the binder composition for a secondary battery.
According to claim 1,
The shell of the emulsion polymer particle is, the binder composition for a secondary battery comprising an alkyl (meth) acrylate-based repeating unit, a cyclic carbonate-based repeating unit, and an unsaturated carboxylic acid-based monomer-derived repeating unit.
8. The method of claim 7,
The shell of the emulsion polymer particles, with respect to 100 parts by weight of the alkyl (meth) acrylate-based repeating unit, the binder composition for a secondary battery comprising 1 to 20 parts by weight of the repeating unit derived from the cyclic carbonate-based monomer.
8. The method of claim 7,
The shell of the emulsion polymer particles, the ratio of the repeating unit derived from the cyclic carbonate-based monomer is 1 to 15 wt%, the binder composition for a secondary battery.
8. The method of claim 7,
The shell of the emulsion polymer particles, with respect to 100 parts by weight of the alkyl (meth) acrylate-based repeating unit, comprising 20 to 70 parts by weight of the repeating unit derived from the unsaturated carboxylic acid-based monomer, a binder composition for a secondary battery.
According to claim 1,
The shell of the emulsified polymer particles comprises a cross-linkage formed by a cross-linking agent, a binder composition for a secondary battery.
12. The method of claim 11,
The crosslinking agent is a compound containing both an acryloyl group and an ethylenically unsaturated bond in a molecule, a binder composition for a secondary battery.
According to any one of claims 1 to 12, comprising the binder composition for a secondary battery and an electrode active material according to any one of claims 1 to 12,
Secondary battery electrode mixture.
14. The method of claim 13,
A secondary battery electrode mixture further comprising a conductive material.
An electrode mixture layer comprising the secondary battery electrode mixture of claim 13; and
including an electrode current collector;
secondary battery electrode.
A secondary battery comprising the secondary battery electrode of claim 15 .