KR101805543B1 - Composite binder composition for secondary battery, anode and lithium battery containing the binder - Google Patents

Abstract

A first nanoparticle having a glass transition temperature of 60 DEG C or higher or an average particle size of not more than 100 nm which does not have a glass transition temperature; And a first polymer binder having a glass transition temperature of 20 DEG C or lower, wherein the first polymer binder contains a polar functional group capable of chemically bonding with the first nanoparticle, a negative electrode And a lithium battery are presented.

Description

TECHNICAL FIELD The present invention relates to a binder composition for a secondary battery, and a cathode and a lithium battery employing the binder composition.

A binder composition for a rechargeable battery, and a negative electrode and a lithium battery employing the same.

Lithium batteries are used for a variety of applications by having high voltage and high energy density. For example, the field of electric automobiles (HEV, PHEV) and the like require a lithium battery which can operate at a high temperature and charge or discharge a large amount of electricity and must be used for a long time, and therefore has excellent discharge capacity and life characteristics.

The carbon-based material is porous and stable in terms of volume change during charging and discharging. However, in general, the carbon-based material has a low cell capacity due to the porous structure of carbon. For example, the theoretical capacity of high crystalline graphite is 372 mAh / g in the LiC ₆ composition.

A metal capable of alloying with lithium may be used as a negative electrode active material having a higher electric capacity than the carbon-based material. For example, metals capable of alloying with lithium are Si, Sn, Al, and the like. However, the metals capable of alloying with lithium are liable to be deteriorated, so that the life characteristics are low. For example, as Sn is repeatedly charged and discharged, aggregation and disintegration of Sn particles are repeated, and Sn particles are electrically disconnected.

Conventional polyimide and polyamideimide as a lithium battery binder have been proposed as a binder for suppressing electrode expansion. However, in a lithium polymer battery or the like requiring a step of winding and pressing an electrode to cure the electrode, Therefore, practical use is difficult.

As a lithium battery binder, a diene-based copolymer is widely used in a negative electrode. The diene-based copolymer binder is excellent in flexibility, but has a low strength when immersed in an electrolytic solution. Therefore, in the case of using a non-carbon based high-capacity anode active material such as Si or Sn, which is a metal capable of alloying with lithium, it is difficult to suppress the expansion of the electrode.

The diene-based copolymer binder is produced by known emulsion polymerization, suspension polymerization and the like. For example, a technique of continuously changing the polymer composition by power-phase polymerization or by making the particle structure into a two-phase structure in emulsion polymerization has been introduced. However, the polymeric binder in which the core / shell particle or the polymer composition is continuously changed can not obtain a balance of flexibility and strength after dipping in the electrolyte solution.

For example, if the Tg of the binder particle surface portion having the core / shell structure is increased to make the surface of the binder particle hard, the film formability may be lowered and the electrode strength may be lowered. When the surface of the binder particle having the core / shell structure is made to have a low Tg and the binder surface is made thin, the strength when the binder particle is immersed in the electrolyte is lowered. In addition, the polymer binder obtained by the method of continuously changing the polymer composition by the power feed polymerization can not obtain the balance between the flexibility and the strength after being immersed in the electrolytic solution.

Accordingly, there is a need for a binder capable of overcoming the limitations of the prior art and improving and / or suppressing the volume change of the non-carbon based negative electrode active material to improve the lifetime characteristics of the lithium battery.

One aspect is to provide a binder composition for a secondary battery having an improved strength.

Another aspect is to provide a negative electrode comprising the binder.

Another aspect is to provide a lithium battery employing the negative electrode.

According to one aspect,

First nanoparticles having an average particle diameter of 100 nm or less and

And a first polymer binder having a glass transition temperature of 20 DEG C or lower, wherein the first polymer binder contains a polar functional group capable of chemically bonding with the first nanoparticles.

According to another aspect,

An anode including the binder is provided.

According to another aspect,

A lithium battery employing the negative electrode is provided.

According to one aspect, there is provided a nanoparticle having an average particle size of 100 nm or less; And a first polymer binder having a glass transition temperature of 20 DEG C or lower, wherein the first polymer binder contains a polar functional group capable of chemically bonding with the first nanoparticle, The cycle characteristics of the battery can be improved.

1 is a schematic diagram of a lithium battery according to an exemplary embodiment.
2 is a schematic view of an apparatus for measuring elastic modulus and breaking strength.
Description of the Related Art
1: Lithium battery 2: cathode
3: anode 4: separator
5: Battery case 6: Cap assembly

Hereinafter, a binder composition for a secondary battery according to exemplary embodiments, a cathode including the same, and a lithium battery employing the cathode will be described in more detail.

Considering the problem that the flexibility is lowered in a conventional general secondary battery binder having a high Tg or high strength, the inventors of the present inventors have studied a method of maintaining the flexibility of the binder and the high film strength even after immersion in the electrolyte. As a result, By appropriately blending nanoparticles having a Tg of 60 ° C or higher and a glass transition temperature not containing the binder in the binder and containing the polar functional group capable of chemically bonding with the nanoparticles, the flexibility and charge / Which is capable of simultaneously suppressing the electrode swelling, can be realized at the same time.

As used herein, the binder composition is defined as a concept including both a state including a solvent and a state not including a solvent.

In one embodiment, the binder composition for a secondary battery comprises a first nanoparticle having an average particle size of 100 nm or less; And a first polymer binder having a glass transition temperature of 20 DEG C or lower, wherein the first polymeric binder contains a polar functional group capable of chemically bonding with the first nanoparticle. The polymer binder includes nanoparticles having an average particle diameter of 100 nm or less and a polymeric binder having a glass transition temperature of 20 DEG C or less. Since the polymeric binder contains a functional group capable of binding to nanoparticles, The cycle characteristics of the lithium battery including the binder composition can be improved by accepting and / or inhibiting the volume change of the negative electrode active material at the time of discharging. In particular, since the first polymer binder contains a functional group capable of binding with the first nanoparticles, the binder composition for a secondary battery can maintain a high elastic modulus even at a high temperature of 60 ° C or higher. In the binder composition for a secondary battery, the first polymer binder has no particular shape and can serve as a kind of matrix.

The average particle diameter of the first nanoparticles in the binder composition for a secondary battery may be 1 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be between 5 nm and 100 nm. For example, the average particle diameter of the first nanoparticles may be 10 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 20 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 30 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 30 nm to 80 nm. For example, the average particle diameter of the first nanoparticles may be 40 nm to 80 nm. For example, the average particle size of the first nanoparticles may be 50 nm to 80 nm. For example, the average particle size of the first nanoparticles may be 50 nm to 80 nm. For example, the average particle size of the first nanoparticles may be 60 nm to 80 nm. If the average particle diameter of the first nanoparticles is more than 100 nm, the strength of the binder may be lowered. If the average particle diameter is too small, the preparation may not be easy and the solid content may be decreased.

In the binder composition for a secondary battery, the first nanoparticles have a glass transition temperature of 60 캜 or higher, whereby the strength of the binder composition for a secondary battery can be improved.

For example, in the binder composition for a secondary battery, the glass transition temperature of the first nanoparticle may be higher than 60 ° C. For example, in the binder composition for a secondary battery, the first nanoparticle may have a glass transition temperature of 70 ° C or higher. For example, in the binder composition for a secondary battery, the first nanoparticle may have a glass transition temperature of 80 캜 or higher. For example, the glass transition temperature of the first nanoparticles in the binder composition for a secondary battery may be 90 ° C or higher.

The first nanoparticle having a glass transition temperature of 60 DEG C or higher may be, for example, polymer particles. For example, the first nanoparticles having a glass transition temperature of 60 DEG C or higher may be polyurethane particles, but not always limited thereto, and any polymer particles that can be used in the art can be used as long as the glass transition temperature is 60 DEG C or higher .

Alternatively, in the binder composition for a secondary battery, the first nanoparticles may have substantially no glass transition temperature. The fact that the first nanoparticles do not have a substantially glass transition temperature means that a significant change in the slope of the heat flow due to temperature in the differential scanning calorimeter (DSC) it means.

The first nanoparticle not having the glass transition temperature (Tg) means particles that do not soften, and include inorganic particles or polymer particles that are highly crosslinked and do not exhibit a glass transition temperature.

For example, the first nanoparticle having no glass transition temperature may be crosslinked polymethylmethacrylate. For example, the first nanoparticle not having the glass transition temperature may be at least one selected from the group consisting of colloidal silica,? -Alumina,? -Alumina, zirconium oxide, and magnesium fluoride, Anything that can be used as inorganic particles in the technical field is possible.

The purpose of using particles having a glass transition temperature of 60 DEG C or higher and having no glass transition temperature is to be used in combination with a polymer having a glass transition temperature of 20 DEG C or lower. In order to suppress the expansion of electrodes due to charge / It is necessary to use a glass transition temperature of 60 DEG C or more or not having a glass transition temperature in consideration of reaching 60 DEG C under the conditions of use.

When the glass transition temperature is lower than 60 캜, the electrode is softened and the strength is lowered when the temperature reaches 60 캜, depending on the conditions of use of the battery, so that expansion of the electrode can not be suppressed. Therefore, particles that do not soften up to a temperature of 60 占 폚 are preferable.

When the first nanoparticles are the organic particles, the first nanoparticles are the first polymer particles. Further, when two or more different polymer particles are additionally contained in the binder composition for a secondary battery of the present invention, the additional polymer particles may be referred to as second polymer particles, third polymer particles, and the like.

In the binder composition for a secondary battery, the first polymer binder has a glass transition temperature of 20 ° C or lower, so that the secondary battery binder composition can have both improved strength and excellent adhesion. For example, the first polymer binder may have a glass transition temperature of -60 캜 to 20 캜. For example, the first polymer binder may have a glass transition temperature of -60 캜 to less than 20 캜. For example, the first polymeric binder may have a glass transition temperature of -60 캜 to 10 캜. For example, the first polymer binder may have a glass transition temperature of -50 ° C to 10 ° C. For example, the first polymer binder may have a glass transition temperature of -40 ° C to 10 ° C. For example, the glass transition temperature of the first polymeric binder may be -30 ° C to 10 ° C. For example, the glass transition temperature of the first polymeric binder may be between -20 ° C and 10 ° C.

The first nanoparticle may contain a polar functional group capable of chemically bonding with the first polymeric binder. For example, the first nanoparticle may have a polar functional group on the particle surface. The polar functional group may form various bonds such as a hydrogen bond, a covalent bond, etc. with the polymeric binder. For example, the polar functional group may be a carboxyl group, a hydroxyl group, an amine group, a glycidyl group, and the like, but not limited thereto, and any polar functional group capable of forming a bond with a polymeric binder is possible.

The first polymeric binder may contain a polar functional group capable of chemically bonding with the first nanoparticle. For example, the first polymeric binder may have a polar functional group in at least a part of the main chain and / or the side chain. The polar functional group may form various bonds such as a hydrogen bond, a covalent bond, etc. with the first nanoparticle. The polar functional group may be a carboxyl group, a hydroxyl group, an amine group, a glycidyl group, or the like, but is not limited thereto, and any polar functional group capable of forming a bond with the first nanoparticle is possible.

The first nanoparticle and the first polymeric binder may form a composite. That is, the first nanoparticles and the first polymeric binder may have physical bonds such as a van der Waals bond, a polar functional group on the surface of the first nanoparticles and a polar functional group of the first polymeric binder, Lt; RTI ID = 0.0 > chemically < / RTI >

The binder composition for a secondary battery may further include at least one second nanoparticle having a glass transition temperature different from that of the first nanoparticle. For example, the binder composition for a secondary battery may include two or more nanoparticles having a different glass transition temperature or no glass transition temperature. For example, the binder composition for a secondary battery may comprise three or more nanoparticles having a different glass transition temperature or no glass transition temperature.

The binder composition for a secondary battery may further include one or more second polymeric binders having a glass transition temperature different from that of the first polymeric binder. For example, the binder composition for a secondary battery may include two or more polymeric binders having different glass transition temperatures. For example, the binder composition for a secondary battery may include three or more polymeric binders having different glass transition temperatures.

However, unless otherwise stated, the first polymeric binder means the entire polymeric binder further including a second polymeric binder or the like. This concept is also the same for the first nanoparticle.

The binder composition for a secondary battery may contain 1 to 60 parts by weight of the first nanoparticle solid component based on 100 parts by weight of the first polymer binder solid component. For example, in the binder composition for a secondary battery, 1 to 60 parts by weight of the first nanoparticles may be contained based on 100 parts by weight of the first polymer binder based on the solid content. For example, 5 to 60 parts by weight of the first nanoparticles may be included in 100 parts by weight of the first polymeric binder based on the solid content in the binder composition for a secondary battery. . For example, in the binder composition for a secondary battery, 5 to 50 parts by weight of the first nanoparticles may be contained relative to 100 parts by weight of the first polymer binder based on the solid content. For example, 5 to 40 parts by weight of the first nanoparticles may be contained in 100 parts by weight of the first polymeric binder based on the solid content in the binder composition for a secondary battery. If the content of the first nanoparticles is too small, the elasticity of the binder may deteriorate. If the content of the first nanoparticles is too high, the binding force may be deteriorated.

That is, in a cathode of a lithium secondary battery, in many cases, it is used in combination with a carbon material for the purpose of suppressing the influence of a material having a large volume change upon charging and discharging. In the case where the ratio of metal-based anode active material is high, It is necessary to increase the ratio of the first nanoparticle / first polymer binder. In addition, when the metal-based negative electrode active material is used in a small proportion, the ratio of the first nanoparticle / first polymeric binder is reduced and the binder composition for the secondary battery is softened The flexibility of the electrode can be improved. When the glass transition temperature of the first polymeric binder is high, since the battery binder becomes hard, the ratio of the first nanoparticle / first polymeric binder is made small in order to secure the flexibility of the electrode, It is necessary to stop the evil incense of.

In the binder composition for a secondary battery, the first nanoparticles may be dispersed in the first polymer binder. And the first nanoparticles may be dispersed in a matrix of the first polymeric binder. The first nanoparticles may be present alone in the first polymeric binder, and may have a form dispersed in a matrix of the first polymeric binder after the plurality of first nanoparticles aggregate to form secondary particles. The first nanoparticles may be uniformly dispersed in the first polymeric binder.

For example, the first nanoparticles may be irregularly dispersed within the first polymeric binder.

For example, the binder composition for a secondary battery includes a first polymer binder aggregate formed from at least two first polymeric binders, wherein the first nanoparticles are composed of at least two first polymer particles included in the first polymer binder aggregate And can be disposed at the interface between the binders. For example, the first nanoparticles may be disposed between a plurality of first polymeric binders.

For example, the first polymer may be irregularly disposed on the interface between the plurality of first polymeric binders.

Alternatively, the first nanoparticles may be disposed at the interface between the first polymeric binder and other battery components. For example, the first nanoparticles may be present at the interface between the first polymeric binder and the electrolyte. For example, the first nanoparticles may be present at an interface between the first polymeric binder and the negative electrode active material. For example, the first nanoparticles may be present at the interface between the first polymeric binder and the conductive material. For example, the first nanoparticles may be present at an interface between the first polymeric binder and the current collector. For example, the first nanoparticles may be present at the interface between the first polymeric binder and the separator. For example, the first polymer may be irregularly disposed on the interface with other battery components.

For example, if the first nanoparticles are polymer particles having a glass transition temperature of 60 DEG C or higher, no glass transition temperature, and an average particle diameter of 100 nm or less, the polymer material is not particularly limited. For example, the first nanoparticle may comprise a water-dispersible functional group. The first nanoparticles can be prepared by various methods such as emulsion polymerization and solution polymerization, and are not particularly limited. The reaction conditions used in the above method can also be appropriately adjusted by those skilled in the art.

For example, the first nanoparticle may be an aqueous dispersion such as a (meth) acrylate-based water dispersion, a diene-based latex, ethylene-acrylate, carboxy modified polyethylene, polyurethane, nylon, polyester, . ≪ / RTI >

For example, the first nanoparticle may be prepared by polymerizing a monomer capable of radical polymerization in a (meth) acrylate-based aqueous dispersion or in the case of a diene-based latex by emulsion polymerization, suspension polymerization or dispersion polymerization have.

The (meth) acrylate-based water dispersion may be prepared by polymerizing an ethylenically unsaturated carboxylic acid ester and other monomers copolymerizable with the ethylenically unsaturated carboxylic acid ester.

Specific examples of ethylenically unsaturated carboxylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, Amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate, hydroxypropyl acrylate, and acrylic acid lauryl; Methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate , N-hexyl methacrylate, 2-ethylhexyl methacrylate, hydroxypropyl methacrylate, methacrylic acid alkyl esters such as lauryl methacrylate, and substituted alkyl esters; Methyl crotonate, ethyl crotonate, propyl crotonate, butyl crotonate, isobutyl crotonate, n-amyl crotonate, isoamyl crotonate, n-hexyl crotonate, croton 2-ethylhexyl, crotonic acid Crotonic acid alkyl esters such as hydroxypropyl and substituted alkyl esters; Amino group-containing methacrylic acid esters such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; Unsaturated dicarboxylic acid monoesters such as mono-octyl maleate, monobutyl maleate, and monooctyl itaconate, and the like, but it is not limited to these, and it is possible to use an alkoxy group-containing methacrylate such as methoxypolyethylene glycol monomethacrylate Any that can be used as the ethylenically unsaturated carboxylic acid ester in the technical field is all possible.

Examples of the monomer copolymerizable with the ethylenically unsaturated carboxylic acid ester include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid and fumaric acid; Carboxylic acid esters having at least two carbon-carbon double bonds such as diethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate; Styrene-based monomers such as styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene,? -Methylstyrene, divinylbenzene; Amide-based monomers such as acrylamide, N-methylol acrylamide and acrylamide-2-methylpropanesulfonic acid; Alpha, beta -unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; Olefins such as ethylene and propylene; Diene-based monomers such as butadiene and isoprene; Halogen-containing monomers such as vinyl chloride and vinylidene chloride; Vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; Vinyl ethers such as allyl glycidyl ether, methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; Vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; Containing vinyl compounds such as N-vinylpyrrolidone, vinylpyridine, and vinylimidazole, but the present invention is not limited thereto. Any monomer that can be used as a monomer copolymerizable with an ethylenically unsaturated carboxylic acid ester in the art It is possible.

Among these copolymerizable monomers, at least one selected from the group consisting of carboxylic acid esters having at least two carbon-carbon double bonds, amide monomers,?,? -Unsaturated nitrile compounds, and vinyl ethers can be used .

Diene-based latex is a copolymer obtained from an aromatic vinyl unit, a conjugated diene unit, an ethylenically unsaturated carboxylic acid ester unit and an ethylenically unsaturated carboxylic acid unit.

The aromatic vinyl unit may be, for example, styrene,? -Methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, and the like, for example, styrene may be used.

The conjugated diene unit may be a conjugated diene compound such as 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, chloroprene and the like, especially 1,3-butadiene.

The ethylenically unsaturated carboxylic acid ester unit includes, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i- butyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, 2-hexyl (Meth) acrylate, ethylhexyl (meth) acrylate, ethyleneglycol ethyleneglycol, ethyleneglycol di (meth) acrylate, (Meth) acrylic acid esters and the like. For example, methyl (meth) acrylate, butyl (meth) acrylate, and the like. In particular, methyl (meth) acrylate may be used.

The ethylenically unsaturated carboxylic acid unit may be acrylic acid, (meth) acrylic acid, itaconic acid, fumaric acid, maleic acid, and the like.

The first nanoparticles may contain other polar functional group-containing compound units copolymerizable with the above-mentioned monomers. Examples of the polar functional group-containing compound unit include alkyl amides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylol acrylamide; Carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate; Acid anhydrides, monoalkyl esters, monoamides of ethylenically unsaturated dicarboxylic acids; Aminoalkyl esters of ethylenically unsaturated carboxylic acids such as aminoethyl acrylate, dimethylaminoethyl acrylate and butylaminoethyl acrylate; Aminoalkyl amides of ethylenically unsaturated carboxylic acids such as aminoethyl acrylamide, dimethylaminomethyl methacrylamide and methylaminopropyl methacrylamide; (Meth) acrylonitrile, and? -Croton acrylonitrile; Unsaturated aliphatic glycidyl esters such as glycidyl (meth) acrylate, and the like, but not always limited thereto, and any compound that can be used in the production of a copolymer as a compound containing a polar functional group in the art is possible.

The above-mentioned monomers necessarily include polar functional groups necessary for chemically bonding with the first polymeric binder. The polar functional group may be a polar functional group capable of chemically bonding with the first polymeric binder or binding the first nanoparticle and the first polymeric binder through the binder. For example, the monomer containing the polar functional group may be an OH group-containing monomer, a carboxyl group-containing monomer, a glycidyl group-containing monomer, an amino group-containing monomer, and the like, but not always limited thereto, As long as it can be used as an electronic device.

The first nanoparticles may not be swollen by being impregnated with the electrolytic solution. For example, the degree of swelling of the first nanoparticles with respect to the electrolytic solution may be 4 times or less. For example, the degree of swelling of the first nanoparticles with respect to the electrolytic solution may be three times or less. For example, the degree of swelling of the first nanoparticles with respect to the electrolytic solution may be less than two times. If the degree of swelling of the first nanoparticles with respect to the electrolytic solution is excessively large, the Tg of the first nanoparticles may be lowered to 60 캜 or lower. Therefore, when the operating temperature of the battery is increased, it may be difficult to suppress the rate of expansion of the electrode including the binder composition for the secondary battery. The degree of swelling is obtained from the weight ratio of the first nanoparticles before and after immersion in the electrolytic solution. That is, it indicates the extent to which the first nanoparticles absorb the electrolyte solution.

In order to suppress the degree of swelling of the first nanoparticles with respect to the electrolytic solution, dienic latexes in which styrene and butadiene account for 80% by weight or more of total monomers can be used. When an acrylic ester-based water dispersion is used, an ethylenically unsaturated carboxylic acid ester esterified with a higher alcohol having 6 or more carbon atoms, a polymer containing 80% by weight or more, such as 85% by weight or more of styrene as a whole monomer . Further, a bifunctional monomer having at least two carbon-carbon double bonds can be used to introduce a crosslinking structure into the first nanoparticles. The bifunctional monomer having two or more carbon-carbon double bonds may be at least two carbon-carbon bonds such as 2-vinylbenzene or ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane triacrylate, Or a carboxylic acid ester having a double bond. For example, 2-vinylbenzene, which can give hard particles, can be used.

Also, for example, the first nanoparticles may be selected from the group consisting of polyethylene, polypropylene, ethylene propylene copolymer, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polytetrafluoroethylene, polymethyl methacrylate, Polyvinyl acetate, polyisoprene, polychloroprene, polyester, polycarbonate, polyamide, polyacrylate, polymethyl methacrylate, polyurethane, acrylonitrile-butadiene-styrene copolymer, polyoxyethylene, polyoxy Acrylonitrile-styrene-acrylate copolymer, styrene-butadiene copolymer, acrylated styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile- Styrene-butadiene-styrene copolymer, acryl rubber, butyl rubber, Polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, polysulfone, polyvinyl alcohol, polyvinyl acetate, thermoplastic polyester rubber (PTEE), carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, and diacetylcellulose, but not limited thereto, and if they can be used as polymer particles in the art Everything is possible. In addition, the first nanoparticles described above may be crosslinked polymers.

The first nanoparticles may be water-based polymer particles or non-aqueous polymer particles. The water-based polymer particles mean water-dispersible polymer particles that can be easily dispersed or dissolved in water.

For example, the first nanoparticle may be a (meth) acrylic acid ester-based water dispersion, a gelatinous latex, an aqueous dispersion of polyurethane, nylon, polyester, or the like. The monomer may be, for example, an ethylenic unsaturated monomer such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, ethyl methacrylate, Unsaturated carboxylic acid alkyl esters; Cyano group-containing ethylenically unsaturated monomers such as acrylonitrile, methacrylonitrile,? -Chloroacrylonitrile and? -Cyanoethyl acrylonitrile; Conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and chloroprene; Ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and citraconic acid, and salts thereof; Aromatic vinyl monomers such as styrene, yl styrene, and vinyl naphthalene; Fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether; Vinyl pyridine; Non-conjugated diene monomers such as vinyl norbornene, dicyclopentadiene and 1,4-hexadiene; ? -Olefins such as ethylene and propylene; Ethylenically unsaturated amide monomers such as methacrylamide; Isocyanate monomers such as methylene diphenyl diisocyanate and toluene diisocyanate; Polyol monomers such as glycerin, ethylene glycol and propylene glycol; Etc., but not limited thereto, and any monomers that can be used in the technical field are all possible.

The first nanoparticles can be produced by various methods such as emulsion polymerization, solution polymerization, suspension polymerization and dispersion polymerization, and are not particularly limited. The reaction conditions used in the above method can also be appropriately adjusted by those skilled in the art.

The first nanoparticles are polymer particles having a Tg of 60 DEG C or higher and emulsify a polymer dissolved in a solvent or a method in which a polymer having crystallinity is heated and dissolved in a poor solvent at a temperature above the melting point, , A method in which a polymer containing a dissociable functional group is converted into a particulate phase in an alkali solution, and the like.

The first polymeric binder is added in order to impart flexibility to the electrode and ensure adhesion to the active material and the current collector, and the polymeric material is not particularly limited as long as it is a polymeric binder having a glass transition temperature of 20 ° C or lower. For example, the first polymeric binder may comprise a water-dispersible functional group. The first polymeric binder may be prepared by various methods such as emulsion polymerization and solution polymerization, and is not particularly limited. The reaction conditions used in the above method can also be appropriately adjusted by those skilled in the art.

For example, the monomer used in the production of the first polymeric binder is a monomer that can be used for radical polymerization. The monomers used in the production of the first polymeric binder may be used in combination with the monomers used for the production of the first nanoparticles.

The monomers used in the preparation of the first polymeric binder necessarily contain the polar functional groups necessary for chemically bonding with the first nanoparticles. The polar functional group may be a polar functional group capable of chemically bonding with the first nanoparticle or binding the first nanoparticle and the first polymer binder through a binder. For example, the monomer containing the polar functional group may be an OH group-containing monomer, a carboxy group-containing monomer, a glycidyl group-containing monomer, an amino group-containing monomer, etc., but is not limited thereto, As long as it can be used as a monomer to be used.

The first polymeric binder may not be swollen by being impregnated with the electrolytic solution. For example, the degree of swelling of the first polymeric binder with respect to the electrolytic solution may be 4 times or less. For example, the degree of swelling of the first polymeric binder with respect to the electrolytic solution may be three times or less. For example, the degree of swelling of the first polymeric binder with respect to the electrolytic solution may be two times or less. If the swelling degree of the first polymeric binder with respect to the electrolytic solution is excessively large, the strength of the binder may be low and it may be difficult to suppress the expansion ratio of the electrode including the binder composition for the secondary battery.

The swelling degree is obtained from the weight ratio of the first polymeric binder before and after immersion in the electrolytic solution. That is, it indicates the extent to which the first polymeric binder absorbs the electrolyte solution.

In order to suppress swelling of the first polymeric binder with respect to the electrolytic solution, a diene latex in which styrene and butadiene account for 80% by weight or more of the total monomers may be used. When an acrylic ester-based water dispersion is used, an ethylenically unsaturated carboxylic acid ester esterified with a higher alcohol having 6 or more carbon atoms, a polymer containing 80% by weight or more, such as 85% by weight or more of styrene as a whole monomer The first polymeric binder may be selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber , Fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylate, polyacrylonitrile , Polystyrene, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, poly But are not limited to, one or more selected from the group consisting of an ester resin, an acrylic resin, a phenol resin, an epoxy resin, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose and diacetylcellulose And can be used as a polymeric binder in the art.

The first polymeric binder may be an aqueous polymeric binder or a non-aqueous polymeric binder. The water-based polymeric binder means a water-dispersible polymeric binder which can be easily dispersed or dissolved in water.

The monomers used for preparing the first polymeric binder include, for example, ethylenically unsaturated carboxylic acid alkyl esters such as methyl methacrylate, butyl methacrylate, ethyl methacrylate and 2-ethylhexyl methacrylate; Cyano group-containing ethylenically unsaturated monomers such as acrylonitrile, methacrylonitrile,? -Chloroacrylonitrile and? -Cyanoethyl acrylonitrile; Conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and chloroprene; Ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and citraconic acid, and salts thereof; Aromatic vinyl monomers such as styrene, yl styrene, and vinyl naphthalene; Fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether; Vinyl pyridine; Non-conjugated diene monomers such as vinyl norbornene, dicyclopentadiene and 1,4-hexadiene; ? -Olefins such as ethylene and propylene; Ethylenically unsaturated amide monomers such as methacrylamide; Etc., but not limited thereto, and any monomers that can be used in the technical field are all possible.

The first polymeric binder may be prepared by various methods such as emulsion polymerization and solution polymerization, and is not particularly limited. The reaction conditions used in the above method can also be appropriately adjusted by those skilled in the art.

In the binder composition for a secondary battery, the gel content of the first polymeric binder may be 90% or less. In the binder composition for a secondary battery, since the first polymer binder containing a polar functional group capable of chemically bonding with the first nanoparticles and the first nanoparticles are used in combination to suppress the expansion of the electrode, It may have high mobility until it is chemically bonded with the first nanoparticles in order to facilitate bonding with the first nanoparticles.

Therefore, when the first polymeric binder is a diene latex, the gel content may be 90% or less. For example, when the first polymeric binder is a diene latex, the gel content may be 80% or less. When the first polymeric binder is a diene latex, the gel content may be 70% or less.

Further, when the first polymeric binder is an acrylate ester emulsion, since the crosslinking structure is introduced into the polymeric binder, the amount of the bifunctional monomer used can be reduced. For example, the bifunctional monomer may be used in an amount of 1% by weight or less, for example, 0.5% by weight or less, based on the total weight of the monomers. The bifunctional monomer is a bifunctional monomer having two or more carbon-carbon double bonds in one molecule. Examples of the bifunctional monomer include 2-vinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane Triacrylate and the like can be used.

For example, the first polymer binder can be produced by a common emulsion polymerization, suspension polymerization, or dispersion polymerization.

The emulsifier and dispersant used in emulsion polymerization, suspension polymerization and dispersion polymerization may be those used in usual emulsion polymerization, suspension polymerization, dispersion polymerization and the like. Benzenesulfonic acid salts such as sodium dodecylbenzenesulfonate and sodium dodecylphenylether sulfonate; Alkylsulfuric acid salts such as sodium laurylsulfate and sodium tetradodecylsulfate; Sulfosuccinates such as sodium dioctylsulfosuccinate and sodium dihexylsulfosuccinate; fatty acid salts such as sodium laurate; Ethoxy sulfates such as polyoxyethylene lauryl ether sulfate sodium salt and polyoxyethylene nonylphenyl ether sulfate sodium salt; Alkane sulfonates; Alkyl ether phosphate ester sodium salt; Nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene sorbitan lauryl ester, polyoxyethylene-polyoxypropylene block copolymer and the like. These may be used alone or in combination of two or more. The amount of the emulsifier and the dispersant to be added may be set arbitrarily, and may be about 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of the monomers. Depending on polymerization conditions, emulsifiers and dispersants may be omitted.

As the molecular weight modifier, in the case of diene-based latex, mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and n-octyl mercaptan; Halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide; Terpinolene; alpha -methylstyrene dimer, and the like.

Such a molecular weight modifier may be added before the initiation of polymerization or during polymerization. The molecular weight modifier may be used in a proportion of 0.01 to 10 parts by weight, for example, 0.1 to 5 parts by weight, based on 100 parts by weight of the monomer.

In the acrylic acid ester-based water dispersion, the molecular weight can be controlled by the polymerization reaction temperature and the addition rate of the monomers, so that the molecular weight regulator can be omitted.

The polymerization initiator may be one used in usual emulsion polymerization, dispersion polymerization, suspension polymerization and the like. For example, polymerization initiators include persulfates such as potassium persulfate and ammonium persulfate; Hydrogen peroxide; Organic peroxides such as benzoyl peroxide and cumene hydroperoxide and the like may be used alone or in combination with a redox polymerization initiator in combination with a reducing agent such as sodium sulfite, sodium thiosulfate, ascorbic acid, etc. . Further, it is also possible to use 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'- 4-dimethylvaleronitrile), dimethyl-2,2'-azobisisobutyrate, and 4,4'-azobis (4-cyanopentanoic acid); Azo compounds such as 2,2'-azobis (2-amino-di-propane) dihydrochloride, 2,2'-azobis (N, N'-dimethyleneisobutylamidine) , N'-dimethyleneisobutylamidine) dihydrochloride; Etc. may be used. The polymerization initiator may be used alone or in combination of two or more. The amount of the polymerization initiator to be used may be 0.01 to 10 parts by weight, for example, 0.1 to 10 parts by weight, for example, 0.1 to 5 parts by weight, based on 100 parts by weight of the total weight of the monomers.

An antioxidant, a preservative, a defoaming agent and the like may be optionally added to the binder composition for a secondary battery.

The binder composition for a secondary battery may further include a binder. The binder may react with polar functional groups present in the first nanoparticles and / or the first polymeric binder to form covalent bonds. For example, the first nanoparticle and the first polymeric binder may be more tightly bonded by the binder. In the binder composition for a secondary battery, the binder may exist in the form of a reaction product with the first nanoparticles and / or the first polymeric binder. When the binder is bound using the binder, the first nanoparticle having a glass transition temperature of 60 DEG C or higher and the first binder polymer having a glass transition temperature of 60 DEG C or lower can be crosslinked, Any one can be used as long as it is capable of reacting with the reactive functional group introduced into the polymer binder.

The binder may include functional groups that are reactive with polar functional groups. For example, the binder may comprise a functional group reactive with a carboxyl group. For example, the binder may include a functional group reactive with a hydroxyl group. For example, the binder may comprise a functional group that is reactive with the amine group. For example, the binder may comprise a functional group that is reactive with water.

For example, the binder may be a carbodiimide-based compound. Such binders include, for example, N, N'-di-o-tolylcarbodiimide, N, N'-diphetylcarbodiimide, N, N'-dioctyldecylcarbodiimide, N, N'-di-2,6-diisopropylphenyl carbodiimide, N, N'-di-2,6-diisopropylphenylcarbodiimide, Di-tert-butylphenylcarbodiimide, N, N'-di-p-nitrophenylcarbodiimide, N, N'-di- Carbodiimide, N, N'-di-p-hydroxyphenylcarbodiimide, N, N'-di-cyclohexylcarbodiimide, N, Bis-dicyclohexylcarbodiimide, ethylene-bis-diphenylcarbodiimide, benzene-2, dicyclohexylcarbodiimide, Diisocyanato-1,3,5-tris (1-methylethyl) homopolymer, 2,4-diisocyanato-1,3,5-tris (1-methylethyl) ProfDi A cyanate copolymer or a combination thereof, but is not necessarily limited to these as long as they can both be used as a carbodiimide compound in the art. In the binder, the carbodiimide compound may exist in the form of a reaction product with the first nanoparticles and / or the first polymeric binder. For example, the diimide bond of the carbodiimide-based compound may exist in the form of a reaction product in which a new covalent bond is formed by reacting with the polar functional group on the surface of the first nanoparticle.

For example, the binder may be a silane coupling agent.

For example, the silane coupling agent may include at least one member selected from the group consisting of an alkoxy group, a halogen group, an amino group, a vinyl group, a glycidoxy group, an acyloxy group and a hydroxyl group.

For example, the silane coupling agent may be at least one selected from the group consisting of vinyl alkyl alkoxy silane, epoxy alkyl alkoxy silane, mercaptoalkyl alkoxy silane, vinyl halosilane and alkyl acyloxy silane.

For example, the silane coupling agent is selected from the group consisting of vinyltris (? -Methoxyethoxy) silane,? -Methacryloxypropyltrimethoxysilane,? -Glycidoxypropyltrimethoxysilane,? - (3,4- Epoxycyclohexyl) ethyltrimethoxysilane,? -Glycidoxypropylmethyldiethoxysilane,? -Aminopropyltriethoxysilane,? -Mercaptopropyltrimethoxysilane,? -Chloropropyltrimethoxysilane, vinyl Trichlorosilane, and methyltriacetoxysilane, but not always limited thereto, and any silane coupling agent that can be used in the art can be used.

For example, a hydrazine compound, an isocyanate compound, a melamine compound, a urea compound, an epoxy compound, a carbodiimide compound, an oxazoline compound, and the like can be used, but not always limited thereto. Can be used. These compounds may be used alone or in combination.

In particular, an oxazoline compound, a carbodiimide compound, an epoxy compound, or an isocyanate compound may be used.

As other binders, those having self-crosslinking property and those having multivalent coordination sites can be used.

In addition, a commercial combination system can be used.

Specifically, APA series (APA-M950, APA-M980, APA-P250, APA-P280, etc.) of Otsuka Chemical Co., Ltd. can be used as the hydrazine compound.

As the isocyanate compound, BASONAT PLR8878, BASONAT HW-100 manufactured by BASF, Bayhydur 3100 manufactured by Sumitomo Bayer Urethane Co., Ltd., and Vijsur VPLS2150 / 1 manufactured by Sumitomo Bayer Urethane Co., Ltd. can be used.

As the melamine compound, Cymel 325 available from Mitsui Cytec Co., Ltd. can be used.

As the urea compound, the beccamine series manufactured by DIC can be used.

Adeka EM-0517, EM-0526, EM-051R, and EM-11-50B manufactured by ADEKA can be used as the epoxy compound.

V-02, V-02, V-04, E-01, E-02, V-01, V-03, V- 07, V-09, V-05, and the like.

(WS-500, WS-700, K-1010E, K-1020E, K-1030E, K-2010E, K-2020E and K-2030E) of Nihon Shokuba Co., Ltd. can be used as the oxazoline compound .

These are commercially available as dispersions or solutions containing a binder.

For example, the content of the binder used in the binder for the secondary battery may be 10 wt% or less based on the total weight of the reactants based on the dry weight. For example, the amount of binder used in the binder preparation may be up to 5 wt%, based on the total weight of the reactants, based on dry weight. For example, the amount of binder used in the binder preparation may be up to 3 wt% based on the total weight of the reactants, based on dry weight. For example, the amount of binder used in the binder preparation may be from greater than 0% to 3% by weight based on the total weight of reactants, based on dry weight. If the content of the binder is too low, polar functional groups necessary for stabilizing the particles may be insufficient, and if the content of the binder is too high, stable electrode slurry can not be produced.

In the binder composition for a secondary battery, the breaking strength of the film after impregnation with the electrolyte may be 30 kg / cm ^{2 or} more. For example, the binder composition for a secondary battery has a breaking strength of 30 kg / cm < 2 > after immersing the electrolyte in a polar non-aqueous solvent for 72 hours at 70 DEG C and then wiping the electrolyte solvent and measuring the tensile rate at a rate of 100 cm / ^{2 or} more. For example, the binder composition for a secondary battery may have a breaking strength of 35 kg / cm ^{2 or} more after impregnation with an electrolyte solution. For example, the binder composition for a secondary battery may have a breaking strength of 40 kg / cm ^{2 or} more after impregnation with an electrolyte solution. For example, the binder composition for a secondary battery may have a breaking strength of 50 kg / cm < ² > or more after impregnation with an electrolyte solution. For example, the binder composition for a secondary battery may have a breaking strength of 60 kg / cm < ² > or more after impregnation with an electrolyte solution. For example, the binder composition for a secondary battery may have a breaking strength of 70 kg / cm ^{2 or} more after impregnating the electrolyte.

The binder composition for a secondary battery obtainable by combining the first nanoparticle having a glass transition temperature of 60 占 폚 or higher and the first polymer binder having a glass transition temperature of 20 占 폚 or less as described above is preferably 0.5 to 10 parts by weight per 100 parts by weight of the negative electrode active material, Parts by weight, for example, 0.8 parts by weight to 3 parts by weight. If the content of the binder composition for the secondary battery is too small, expansion of the electrode due to charge and discharge can not be suppressed. If the content of the binder composition for the secondary battery is too large, the proportion of the binder composition in the battery increases, And the electrode resistance is increased.

The binder composition for a secondary battery according to another embodiment may further include a solvent. For example, the binder composition for a secondary battery includes first nanoparticles having an average particle diameter of 100 nm or less; A first polymeric binder particle having a glass transition temperature of 20 DEG C or lower; And a solvent, wherein the first polymeric binder particle may contain a polar functional group capable of chemically bonding with the first nanoparticle.

In the binder composition for a secondary battery, the first nanoparticles and the first polymeric binder may be dispersed in a solvent while maintaining the particle shape. For example, the binder composition for a secondary battery may be in an emulsion state. The binder composition for a secondary battery may be in the range of pH 7 to 11 in order to maintain stability. Ammonia and hydroxides of alkali metals may be used as the pH adjusting agent. If the particle diameters of the first nanoparticles and the first polymeric binder particles dispersed in the binder composition are too small, the viscosity of the emulsion increases and the handling thereof becomes difficult. If the particle diameters of the first nanoparticles and the first polymeric binder particles are excessively large, Can be reduced.

The first nanoparticles and the first polymeric binder particles may be mixed in the binder composition for a secondary battery further comprising the solvent. For example, in the binder composition for a secondary battery, the first nanoparticles and the first polymeric binder may be uniformly mixed in a solvent.

In the binder composition for a secondary battery further comprising the solvent, the first nanoparticles may have an average particle diameter of 1 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be between 5 nm and 100 nm. For example, the average particle diameter of the first nanoparticles may be 10 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 20 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 30 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 40 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 50 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 50 nm to 90 nm. For example, the average particle size of the first nanoparticles may be 60 nm to 80 nm. If the average particle diameter of the first nanoparticles is more than 100 nm, the strength of the secondary battery binder produced from the secondary battery binder composition may be reduced. If the average particle diameter is too small, the preparation may not be easy.

In the binder composition for a secondary battery further comprising the solvent, the average particle diameter of the polymeric binder particles may be 50 nm to 500 nm. For example, the average particle diameter of the polymeric binder particles may be 60 nm to 400 nm. For example, the average particle diameter of the polymeric binder particles may be 70 nm to 300 nm. For example, the average particle diameter of the polymeric binder particles may be 80 nm to 200 nm. The strength and the modulus of elasticity of the secondary battery binder obtained from the binder composition for a secondary battery can be improved in an average particle diameter range of the polymer binder particles.

The first polymeric binder particle may contain a polar functional group capable of chemically bonding with the first nanoparticle. For example, the first polymeric binder particle may have a polar functional group in at least a part of the main chain and / or the side chain. The polar functional group may form various bonds such as a hydrogen bond, a covalent bond, etc. with the first nanoparticle. The polar functional group may be a carboxyl group, a hydroxyl group, an amine group, a glycidyl group, or the like, but is not limited thereto, and any polar functional group capable of forming a bond with the first nanoparticle is possible.

In addition, the first nanoparticle may contain a polar functional group capable of chemically bonding with the first polymeric binder particle. For example, the first nanoparticle may have a polar functional group on the particle surface. The polar functional group may form various bonds such as a hydrogen bond, a covalent bond, etc. with the polymeric binder particle. For example, the polar functional group may be a carboxyl group, a hydroxyl group, an amine group, a glycidyl group, or the like, but not limited thereto, and any polar functional group capable of forming a bond with the polymeric binder particle is possible.

For example, in the binder composition for a secondary battery, which further comprises the solvent, more than 0 to 10 parts by weight of the binder may be included relative to 100 parts by weight of the first polymeric binder particles. For example, in the binder composition for a secondary battery, more than 0 to 5 parts by weight of the binder may be included based on 100 parts by weight of the first polymeric binder particles based on the dry weight. For example, in the binder composition for a secondary battery, more than 0 to 3 parts by weight of the binder may be included based on 100 parts by weight of the first polymer binder based on the dry weight.

For example, in the binder composition for a secondary battery further comprising the solvent, the mixing ratio of the first polymeric binder particles, the first nanoparticles, and the binder is, based on the dry weight, about 100 parts by weight of the first polymeric binder particles, 10 to 50 parts by weight of the particles and 0.01 to 5 parts by weight of the binder. For example, the mixing ratio may be 10 to 40 parts by weight of the first nanoparticles and 0.01 to 3 parts by weight of the binder based on 100 parts by weight of the first polymeric binder particles based on the dry weight.

The negative electrode according to another embodiment includes the negative electrode active material and the binder composition for the secondary battery described above.

The negative electrode may include a binder composition for a secondary battery in which first nanoparticles are dispersed in a first polymeric binder. In the binder composition for a secondary battery included in the negative electrode, the first polymer binder serves as a matrix and the first nanoparticles are dispersed in the matrix.

The negative electrode may be formed, for example, by forming the negative electrode active material composition containing the negative electrode active material and the binder composition for the secondary battery into a predetermined shape or by applying the negative electrode active material composition to a current collector such as copper foil .

Specifically, a negative electrode active material composition comprising a negative electrode active material, a conductive material, the binder composition for a secondary battery and a solvent as described above is prepared. The negative electrode active material composition is directly coated on the metal current collector to produce a negative electrode plate. Alternatively, the negative electrode active material composition may be cast on a separate support, and then the film peeled off from the support may be laminated on the metal current collector to produce a negative electrode plate. The negative electrode is not limited to the above-described form, but may be in a form other than the above-described form.

The negative electrode active material may be a non-carbon-based material. For example, the negative electrode active material includes at least one selected from the group consisting of a metal capable of forming an alloy with lithium, an alloy of a metal capable of forming an alloy with lithium, and an oxide of a metal capable of forming an alloy with lithium can do.

For example, the lithium-alloysable metal may be selected from the group consisting of Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloys (Y is an alkali metal, an alkaline earth metal, a Group 13-16 element, (The Y is an alkali metal, an alkaline earth metal, a Group 13 to 16 element, a transition metal, a rare earth element, or a combination element thereof, but not Sn), or the like . The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, Te, Po, or a combination thereof.

For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, or the like.

For example, the non-transition metal oxide may be SnO ₂ , SiO _x (0 <x <2), or the like.

The anode active material may include at least one selected from the group consisting of Si, Sn, Pb, Ge, Al, SiOx (0 <x? 2), SnOy (0 <y? 2), Li ₄ Ti ₅ O ₁₂ , TiO ₂ , LiTiO ₃ , Li ₂ Ti ₃ O ₇ , but it is not limited thereto, and any negative electrode active material used in the technical field can be used.

Also, a composite of the non-carbon based negative active material and the carbon-based material may be used, and in addition to the non-carbon based material, a carbon-based negative active material may be additionally included.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as natural graphite or artificial graphite in the form of non-shaped, flake, flake, spherical or fibrous type, and the amorphous carbon may be a soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, calcined coke, and the like.

As the conductive material, metal powders such as acetylene black, Ketjen black, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, copper, nickel, aluminum and silver, metal fibers, In addition, one or more conductive materials such as polyphenylene derivatives may be used in combination, but the present invention is not limited thereto, and any conductive material may be used as long as it can be used as a conductive material in the related art. In addition, the above-described crystalline carbon-based material can be added as a conductive material.

In addition to the above-described binder composition for a secondary battery, conventional conventional binders may be further used. Such conventional conventional binders include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, or styrene butadiene Rubber-based polymers, and the like can be used, but not limited thereto, and any of them can be used as long as they can be used as a bonding agent in the technical field.

As the solvent, N-methylpyrrolidone, acetone, water or the like may be used, but not limited thereto, and any solvent which can be used in the technical field can be used.

The content of the negative electrode active material, the conductive material, the general binder and the solvent is a level commonly used in a lithium battery. Depending on the use and configuration of the lithium battery, one or more of the conductive material, general binder, and solvent may be omitted.

The lithium battery according to another embodiment employs the above-described negative electrode. The lithium battery can be produced by the following method.

First, a negative electrode is prepared according to the negative electrode manufacturing method.

Next, a cathode active material composition in which a cathode active material, a conductive material, a binder and a solvent are mixed is prepared. The positive electrode active material composition is directly coated on the metal current collector and dried to produce a positive electrode plate. Alternatively, the cathode active material composition may be cast on a separate support, and then the film peeled from the support may be laminated on the metal current collector to produce a cathode plate.

The positive electrode active material may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide. However, May be used.

For example, Li _a A _1-b B _b D ₂ , wherein 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5; Li _a E _1-b B _b O _{2 -c} D _c wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05; LiE (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05) 2-b B b O 4-c D c; Li _a Ni _{1 -bc} Co _b B _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1- b c} Co _b B _c O _{2 -?} F _? Wherein? 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1- b c} Co _b B _c O _2-α F ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2; Li _a Ni _1-bc Mn _b B _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _1-bc Mn _b B _c O _2-α F _α wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2; Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2; Li _a Ni _b E _c G _d O ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8, and 0.001? B? 0.1); Li _a CoG _b O ₂ wherein, in the above formula, 0.90? A? 1.8, and 0.001? B? 0.1; Li _a MnG _b O ₂ (in the above formula, 0.90? A? 1.8, 0.001? B? 0.1); Li _a Mn ₂ G _b O ₄ wherein, in the above formula, 0.90? A? 1.8, and 0.001? B? 0.1; QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); In the formula of LiFePO ₄ may be used a compound represented by any one:

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or combinations thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise an oxide, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a coating element compound of the hydroxycarbonate of the coating element. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be any coating method as long as it can coat the above compound by a method that does not adversely affect physical properties of the cathode active material (for example, spray coating, dipping, etc.) by using these elements, It will be understood by those skilled in the art that a detailed description will be omitted.

For example, LiNiO ₂ , LiCoO ₂ , LiMn _x O ₂ x (x = 1, 2), LiNi _1-x Mn _x O ₂ (0 <x <1), LiNi _1-xy Co _x Mn _y O ₂ ? 0.5, 0? Y? 0.5), LiFeO ₂ , V ₂ O ₅ , TiS, MoS and the like can be used.

As the conductive material, the binder and the solvent in the positive electrode active material composition, the same materials as those for the negative electrode active material composition may be used. It is also possible to add a plasticizer to the cathode active material composition and / or the anode active material composition to form pores inside the electrode plate.

The content of the cathode active material, the conductive material, the general binder, and the solvent is a level commonly used in a lithium battery. Depending on the use and configuration of the lithium battery, one or more of the conductive material, general binder, and solvent may be omitted.

Next, a separator to be inserted between the positive electrode and the negative electrode is prepared. The separator can be used as long as it is commonly used in a lithium battery. A material having low resistance against the ion movement of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be nonwoven fabric or woven fabric. For example, a rewindable separator such as polyethylene, polypropylene, or the like is used for the lithium ion battery, and a separator having excellent organic electrolyte impregnation capability can be used for the lithium ion polymer battery. For example, the separator may be produced according to the following method.

A polymer resin, a filler and a solvent are mixed to prepare a separator composition. The separator composition may be coated directly on the electrode and dried to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled from the support may be laminated on the electrode to form a separator.

The polymer resin used in the production of the separator is not particularly limited, and any material used for the binder of the electrode plate may be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate or mixtures thereof may be used.

Next, the electrolyte is prepared.

For example, the electrolyte may be an organic electrolyte. In addition, the electrolyte may be a solid. For example, boron oxide, lithium oxynitride, and the like, but not limited thereto, and any of them can be used as long as they can be used as solid electrolytes in the art. The solid electrolyte may be formed on the cathode by a method such as sputtering.

For example, an organic electrolytic solution can be prepared. The organic electrolytic solution can be prepared by dissolving a lithium salt in an organic solvent.

The organic solvent may be any organic solvent which can be used in the art. Examples of the solvent include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, gamma -butyrolactone, dioxolane, , Dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether or mixtures thereof.

The lithium salt may also be used as long as it can be used in the art as a lithium salt. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl, LiI, or a mixture thereof.

As shown in FIG. 1, the lithium battery 1 includes an anode 3, a cathode 2, and a separator 4. The anode 3, the cathode 2 and the separator 4 described above are wound or folded and housed in the battery case 5. Then, an organic electrolytic solution is injected into the battery case 5 and is sealed with a cap assembly 6 to complete the lithium battery 1. The battery case may have a cylindrical shape, a rectangular shape, a thin film shape, or the like. For example, the lithium battery may be a thin film battery. The lithium battery may be a lithium ion battery. The lithium battery may be a lithium polymer battery.

A separator may be disposed between the anode and the cathode to form a battery structure. The cell structure is laminated or wound in a bi-cellular structure, then impregnated with an organic electrolytic solution, and the resulting product is received in a pouch and sealed to complete a lithium ion polymer battery.

In addition, a plurality of battery assemblies may be stacked to form a battery pack, and such battery pack may be used for all devices requiring high capacity and high output. For example, a notebook, a smart phone, an electric vehicle, and the like.

Particularly, the lithium battery is suitable for an electric vehicle (EV) because it has a high rate characteristic and a good life characteristic. For example, it is suitable for a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV).

The present invention will be described in more detail by way of the following examples and comparative examples. However, the examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

(Preparation of First Polymeric Binder Particle Emulsion)

Production Example 1 (Binder A)

Nitrogen was substituted in the inside of a flask reactor equipped with a condenser, a thermometer, a monomer emulsion feed pipe, a nitrogen gas feed pipe and a stirrer, and then 200 parts by weight of distilled water and 0.5 part by weight of sodium dodecylbenzenesulfonate were added. The temperature was raised. Then, 1.0 part by weight of potassium persulfate, 0.5 part by weight of sodium bisulfate, 0.2 part by weight of? -Methylstyrene dimer, 0.2 part by weight of t-dodecylmercaptan, 34 parts by weight of butadiene, 30 parts by weight of styrene, , 10 parts by weight of acrylonitrile, 7 parts by weight of methacrylic acid, and 2 parts by weight of acrylic acid was charged into a reactor at 45 캜, and the reaction was carried out. After the polymerization conversion reached 40%, 0.4 part by weight of t-dodecylmercaptan was added and the reaction was further carried out. When the polymerization conversion reached 80%, the reaction temperature was raised to 60 ° C and the reaction was further conducted for 6 hours , And the polymerization conversion reached 98%. Subsequently, the reaction solution was cooled to 20 DEG C, further reduced in pressure to remove residual monomers, and adjusted to a solids concentration of 40% while adjusting the pH to 7.0 with a 5 wt% aqueous lithium hydroxide solution to obtain an acrylic ester polymer emulsion. The average particle diameter of the polymeric binder particles dispersed in the emulsion was 120 nm. The Tg of the polymeric binder particle was 17 캜, and the gel content was 70%.

The polymeric binder contains a carboxyl group as a polar functional group.

Production Example 2 (Binder B)

Nitrogen was substituted in the inside of a flask reactor equipped with a condenser, a thermometer, a monomer emulsion feed pipe, a nitrogen gas feed pipe and a stirrer, and then 200 parts by weight of distilled water and 0.5 part by weight of sodium dodecylbenzenesulfonate were added. The temperature was raised. Then, 1.0 part by weight of potassium persulfate, 0.5 part by weight of sodium bisulfate, 0.2 part by weight of? -Methylstyrene dimer, 0.2 part by weight of t-dodecylmercaptan, 34 parts by weight of butadiene, 31 parts by weight of styrene, , 15 parts by weight of acrylonitrile, 2 parts by weight of methacrylic acid, 2 parts by weight of acrylic acid and 4 parts by weight of hydroxyethyl methacrylate were charged in a batch reactor at 45 ° C and the reaction was carried out. After the polymerization conversion reached 40%, 0.3 part by weight of t-dodecylmercaptan was added and the reaction was further carried out. When the polymerization conversion reached 80%, the reaction temperature was raised to 60 ° C and the reaction was further carried out for 6 hours , And the polymerization conversion reached 98%. Subsequently, the reaction solution was cooled to 20 DEG C, further reduced in pressure to remove residual monomers, and adjusted to a solids concentration of 40% while adjusting the pH to 7.0 with a 5 wt% aqueous lithium hydroxide solution to obtain an acrylic ester polymer emulsion. The average particle diameter of the polymer particles dispersed in the emulsion was 110 nm. The Tg of the polymeric binder particle was 11 캜, and the gel content was 72%.

The polymeric binder includes hydroxy as a polar functional group.

(Preparation of first nanoparticle emulsion)

Production Example 3

Nitrogen was substituted in the inside of a flask reactor equipped with a condenser, a thermometer, a monomer emulsion feed pipe, a nitrogen gas feed pipe and a stirrer, and then 500 parts by weight of distilled water and 3 parts by weight of sodium salt of dodecylbenzenesulfonic acid were added. The temperature was raised. Subsequently, 2 parts by weight of methyl methacrylate was added to the reactor, stirred for 5 minutes, and then 20 parts by weight of a 5% aqueous solution of ammonium persulfate was added to the reactor to initiate the reaction. After 1 hour, a monomer emulsion composed of 93 parts by weight of methyl methacrylate, 2 parts by weight of acrylic acid, 4 parts by weight of methacrylic acid, 1 part by weight of ethylene dimethacrylate, 0.5 part by weight of sodium dodecylbenzenesulfonate and 40 parts by weight of distilled water Was added dropwise to the reactor for 3 hours. At the same time, 10 parts by weight of a 5% aqueous solution of ammonium persulfate was added dropwise to the reactor for 3 hours. After the dropwise addition of the monomer emulsion was completed, the reaction was further carried out for 1 hour to reach a polymerization conversion rate of 98.9%. Subsequently, the reaction solution was cooled to 20 占 폚, the residual monomer was further removed by reduced pressure, and the solid content concentration was adjusted to 15% by adjusting the pH to 8.0 with a 5 wt% aqueous solution of lithium hydroxide to obtain an emulsion &Lt; / RTI &gt; The average particle diameter of the polymer particles dispersed in the emulsion was 70 nm.

Production Example 4

Nitrogen was substituted in the inside of a flask reactor equipped with a condenser, a thermometer, a monomer emulsion feed pipe, a nitrogen gas feed pipe and a stirrer, and then 500 parts by weight of distilled water and 3 parts by weight of sodium dodecylbenzenesulfonate were added, The temperature was raised. Subsequently, 2 parts by weight of methyl methacrylate was added to the reactor, stirred for 5 minutes, and then 20 parts by weight of a 5% aqueous solution of ammonium persulfate was added to the reactor to initiate the reaction. After 1 hour, a monomer emulsion composed of 99 parts by weight of methyl methacrylate, 1 part by weight of ethylene dimethacrylate, 2 parts by weight of sodium dodecylbenzenesulfonate and 40 parts by weight of distilled water was added dropwise to the reactor for 3 hours. At the same time, 10 parts by weight of a 5% aqueous solution of ammonium persulfate was added dropwise to the reactor for 3 hours. After the dropwise addition of the monomer emulsion was completed, the reaction was further carried out for 1 hour to reach a polymerization conversion rate of 98.7%. Subsequently, the reaction solution was cooled to 20 캜 and further reduced in pressure to remove residual monomers. The solid content concentration was adjusted to 15% by adjusting the pH to 8.0 with a 5 wt% aqueous solution of lithium hydroxide to obtain an emulsion containing polymer particles having a Tg of 108 캜 &Lt; / RTI &gt; The average particle size of the polymer particles dispersed in the emulsion was 90 nm.

Comparative Preparation Example 1

Nitrogen was substituted in the flask reactor equipped with a condenser, a thermometer, a monomer emulsion introducing tube, a nitrogen gas introducing tube and a stirrer, and then 200 parts by weight of distilled water, 0.5 part by weight of sodium dodecylbenzenesulfonate, , 0.5 parts by weight of sodium bisulfite, 33 parts by weight of styrene, 36 parts by weight of butadiene, 30 parts by weight of methyl methacrylate, 1 part by weight of itaconic acid, 0.1 part by weight of? -Methylstyrene dimer and 0.2 parts by weight of t-dodecylmercaptan The monomer mixture was charged batchwise into the reactor at 45 占 폚 and the reaction was carried out for 6 hours. After the polymerization conversion reached 70%, 66 parts by weight of styrene, 9 parts by weight of butadiene, 18 parts by weight of methyl methacrylate, 4 parts by weight of butyl acrylate, 1 part by weight of acrylic acid, 2 parts by weight of itaconic acid, 0.2 part by weight of dimer and 0.1 part by weight of t-dodecylmercaptan was continuously introduced at 60 DEG C over 7 hours. After the addition of the monomer mixture was completed, the reaction was further carried out at 70 캜 for 6 hours to reach a polymerization conversion rate of 98 to 99%. Subsequently, the reaction solution was cooled to 20 占 폚, the residual monomer was further removed by reduced pressure, and the solid content concentration was adjusted to 40% while adjusting the pH to 7.0 with a 5 wt% lithium hydroxide aqueous solution to obtain an emulsion containing polymer particles. The Tg of the copolymer obtained from the monomer constituting the core in the emulsion was 0 占 폚, and the Tg of the copolymer obtained from the monomer constituting the shell was 60 占 폚.

Comparative Production Example 2

After replacing nitrogen in a flask reactor equipped with a condenser, a thermometer, a monomer emulsion introducing tube, a nitrogen gas introducing tube and a stirrer, 1500 parts by weight of distilled water, 25 parts by weight of sodium dodecylbenzenesulfonate, , 400 parts by weight of styrene, 200 parts by weight of styrene, 5 parts by weight of divinylbenzene as a crosslinking agent, and 15 parts by weight of azobisbutyronitrile as a polymerization initiator were added and sufficiently stirred. After the monomer consumption amount reached 98%, 200 parts by weight of methyl methacrylate, 50 parts by weight of styrene, 5 parts by weight of divinylbenzene and 200 parts by weight of distilled water were added and thoroughly mixed to carry out the reaction to obtain a monomer consumption of 99.8% . Subsequently, the reaction solution was cooled to 20 占 폚, the residual monomer was further removed by reduced pressure, and the solid content concentration was adjusted to 40% while adjusting the pH to 7.0 with a 5 wt% lithium hydroxide aqueous solution to obtain an emulsion containing polymer particles. The solvent was removed from the emulsion and the gel content of the dried binder was 92%.

(Preparation of binder composition for secondary battery)

Example 1

30 parts by weight of a polymer emulsion having an average particle size of 70 nm (solids content of 15% by weight) prepared in Preparation Example 3 was added to 100 parts by weight of a dry weight of a polymer emulsion having an average particle diameter of 120 nm (binder A, solid content 40% And 1 part by weight of carbodiimide binder (Carbodilite V-02-L2, Nisshinbo Chemical Inc.) on the dry weight basis was added, followed by stirring for 10 minutes to prepare a binder composition for a secondary battery.

Example 2

A binder composition for a secondary battery was prepared in the same manner as in Example 1, except that 2 parts by weight of carbodiimide binder (Carbodilite V-02-L2, Nisshinbo Chemical Inc.) was added based on the dry weight.

Example 3

A binder composition for a secondary battery was prepared in the same manner as in Example 1, except that 4 weight parts of carbodiimide binder (Carbodilite V-02-L2, Nisshinbo Chemical Inc.) was added on a dry weight basis.

Example 4

20 parts by weight of a polymer emulsion having an average particle size of 70 nm (solid content: 15% by weight) prepared in Preparation Example 3 and 100 parts by weight of a dry weight of a polymer emulsion having an average particle diameter of 120 nm (binder B, solid content 40% And 1 part by weight of? -Glycidoxypropyltrimethoxysilane as a silane coupling agent was added thereto, followed by stirring for 10 minutes to prepare a binder composition for a secondary battery.

Example 5

Except that 2 parts by weight of? -Glycidoxypropyltrimethoxysilane, which is a silane coupling agent, was added to the binder composition for a secondary battery.

Example 6

And 4 parts by weight of? -Glycidoxypropyltrimethoxysilane as a silane coupling agent were added to the binder composition for a secondary battery.

Comparative Example 1

The emulsion prepared in Comparative Preparation Example 1 was directly used as a binder composition for a secondary battery.

Comparative Example 2

The emulsion prepared in Comparative Preparation Example 2 was directly used as a binder composition for a secondary battery.

Comparative Example 3 (Example in which particles having a Tg of 60 占 폚 or more were not added)

A polymer emulsion having an average particle diameter of 120 nm (binder A, solid content 40%) prepared in Preparation Example 1 was used as it is as a binder composition for a secondary battery.

(Preparation of negative electrode and lithium battery)

Example 7

(3M, Minnesota, USA, CV3) and artificial graphite (Hitachi Chemical, Tokyo, Japan, MAG) and carboxymethylcellulose (CMC) having an average particle size (d50) of 3 탆 were mixed in pure water, The active material slurry was prepared so that the weight ratio of Si-Fe alloy: graphite: CMC: binder (solid content) = 20: 77: 1: 2 by adding the binder composition for secondary battery prepared in Example 1 above.

The active material slurry was coated on the copper foil having a thickness of 10 mu m to a thickness of 90 mu m, dried at 110 DEG C for 0.5 hour, rolled to a thickness of 70 mu m to prepare a negative electrode plate, and then a coin cell (CR2016 type) .

In the cell manufacturing process, metal lithium was used as a counter electrode, a polyethylene separator (Star ^® 20) with a thickness of 20 μm was used as a separator, and EC (ethylene carbonate): EMC (ethylmethyl carbonate) (Diethyl carbonate) (3: 3: 4 by volume) mixed solvent, 1.15 M LiPF ₆ dissolved therein was used.

Examples 8 to 12

A negative electrode and a lithium battery were produced in the same manner as in Example 7 except that the binder compositions for secondary batteries prepared in Examples 2 to 6 were used respectively.

Comparative Examples 4 to 6

A negative electrode and a lithium battery were respectively prepared in the same manner as in Example 7 except that the binder composition for secondary battery prepared in Comparative Examples 1 to 3 was used.

Evaluation Example 1: Measurement of high temperature elastic modulus

The binder compositions for the secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 3 were coated on a substrate and dried at room temperature for 24 hours to remove the solvent. Then, the film was removed from the substrate to prepare binder specimens. The binder specimen was cut into a width of 0.8 cm, a length of 3 cm, and a thickness of 6 mm, and the strain-induced strain change was measured using a tensile tester manufactured by Instron in accordance with ASTM specification. The modulus of the binder at 60 ° C was calculated from the slope of the stress-strain graph. In Table 1 below, MPa is mega pascal.

The width of the binder specimen corresponds to B in Fig. 2, the length of the binder specimen corresponds to A in Fig. 2, and the thickness of the binder specimen corresponds to C in Fig.

Modulus of elasticity [MPa] Example 1 62 Example 2 81 Example 3 93 Example 4 54 Example 5 68 Example 6 81 Comparative Example 1 28 Comparative Example 2 - Comparative Example 3 10

As shown in Table 1, the secondary battery binder obtained from the binder compositions for secondary batteries of Examples 1 to 6 exhibited significantly improved elastic modulus as compared with the binders of Comparative Examples 1 to 3. The binder composition of Comparative Example 2 was unable to produce a binder film and could not measure its physical properties.

Evaluation Example 2: Measurement of breaking strength of electrolyte immersion film

The binder compositions for the secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 3 were poured into a Teflon petri dish having a diameter of 12 cm and dried at room temperature for 2 days to prepare binder films each having a thickness of 0.6 mm. The binder film was dried in a vacuum dryer at 70 캜 for 10 hours to sufficiently remove moisture. A binder specimen for strength measurement with a length of 5 cm and a width of 5 mm was prepared from the dried binder film.

The width of the binder specimen corresponds to B in Fig. 2, the length of the binder specimen corresponds to A in Fig. 2, and the thickness of the binder specimen corresponds to C in Fig.

The binder specimen was immersed in a mixed solvent of EC (ethylene carbonate): EMC (ethylmethyl carbonate): DEC (diethyl carbonate) (3: 5: 2 by volume) mixed solvent (electrolyte solution) at 70 DEG C for 72 hours, The breaking strength was measured using a tensile tester under the condition of a tensile speed of 100 cm / min.

Four specimens were measured and the fracture strength of the electrolyte immersion film was measured according to the following equation (1).

&Quot; (1) &quot;

Strength of specimen = Strength of specimen with strongest strength x 0.5 + Strength of specimen with strong second strength x 0.3 + Strength of specimen with strong strength x 0.1 + Strength of specimen with weakest strength x 0.1

The measurement results are shown in Table 2 below.

Breaking strength [kg / cm ² ] Example 1 40 Example 2 68 Example 3 82 Example 4 35 Example 5 52 Example 6 55 Comparative Example 1 7 Comparative Example 2 - Comparative Example 3 23

As shown in Table 2, the binder for the secondary battery obtained from the binder composition for the secondary battery of Examples 1 to 6 had a breaking strength of 30 kg / cm ² or more in the electrolyte-impregnated film in comparison with the binder of Comparative Examples 1 to 3 .

The binder composition of Comparative Example 2 was unable to produce a binder film and could not measure its physical properties.

Evaluation Example 3: Evaluation of charge / discharge characteristics and electrode expansion rate

The coin cells prepared in Examples 7 to 12 and Comparative Examples 4 to 6 were subjected to constant current charging at a current of 0.05 C rate at 25 DEG C until the voltage reached 0.01 V (vs. Li), and while maintaining 0.01 V The battery was subjected to constant-voltage charging until the current became 0.02C. Then, at the time of discharging, the battery was discharged at a constant current of 0.05 C until the voltage reached 1.5 V (vs. Li) (Mars phase)

The lithium battery having undergone the above conversion step was charged at a constant current of 0.2 C at a current of 25 C until the voltage reached 0.01 V (vs. Li), and was charged at a constant voltage until the current became 0.02 C while maintaining the voltage at 0.01 V . Next, discharge and discharge performance were evaluated at a constant current of 0.2 C until the voltage reached 1.5 V (vs. Li) at discharge.

Then, the lithium battery in which the initial capacity was evaluated was subjected to constant current charging at a current of 0.7 C rate at 25 DEG C until the voltage reached 0.01 V (vs. Li), and while maintaining 0.01 V, And the cycle of discharging at a constant current of 0.5 C until the voltage reached 1.5 V (vs. Li) at the time of discharging was repeated 100 times.

Part of the charge-discharge test results are shown in Table 3 below. The electrode expansion ratio is defined by the following equation (2).

The electrode expansion rate was calculated by subtracting the thickness of the negative electrode before assembling the battery and the thickness of the negative electrode after decomposing the battery after 30 cycles of charging and discharging after completing the constant current / Respectively. The measurement results are shown in Table 3 below.

The capacity retention rate is defined by the following equation (3).

&Quot; (2) &quot;

Electrode expansion rate [%] = [Thickness of negative electrode after 1 ^th cycle charging / Thickness of unused negative electrode] × 100

&Quot; (3) &quot;

Capacity retention rate = [Discharge capacity in 100 ^th cycle / Discharge capacity in 1 ^st cycle] × 100

Cycle life
[%] Electrode expansion rate
[%] Example 7 78 43 Example 8 81 40 Example 9 83 35 Example 10 75 45 Example 11 78 42 Example 12 80 39 Comparative Example 4 65 50 Comparative Example 5 - - Comparative Example 6 55 68

As shown in Table 3, the lithium batteries of Examples 7 to 12 have improved electrode expansion rates and improved life characteristics compared with the lithium batteries of Comparative Examples 4 to 6.

In the lithium battery of Comparative Example 5, the electrode could not be manufactured and the physical properties could not be measured.

Therefore, the lifetime characteristics of the lithium battery were improved by reducing the coefficient of electrode expansion in the lithium battery of the example including the binder having the improved strength or elastic modulus.

Claims (18)

A first nanoparticle having a glass transition temperature of 60 DEG C or higher and an average particle diameter of 1 nm to 90 nm; And
And a first polymer binder having a glass transition temperature of 20 DEG C or lower,
Wherein the first polymeric binder contains a polar functional group capable of chemically bonding with the first nanoparticle,
Wherein the polar functional group is at least one selected from the group consisting of a carboxyl group, a hydroxyl group, an amine group, and a glycidyl group. delete The binder composition for a secondary battery according to claim 1, wherein the first nanoparticles are polymer particles. The binder composition for a secondary battery according to claim 3, wherein the polymer particles are polyurethane. delete delete delete delete The binder composition for a secondary battery according to claim 1, wherein the first nanoparticles further comprise at least one inorganic particle selected from the group consisting of colloidal silica,? -Alumina,? -Alumina, zirconium oxide, and magnesium fluoride. delete The binder composition for a secondary battery according to claim 1, wherein the first nanoparticles contain a polar functional group capable of chemically bonding with the first polymeric binder. The binder composition for a secondary battery according to claim 1, which comprises 1 to 60 parts by weight of solid first nanoparticles relative to 100 parts by weight of solid first binder polymer. The binder composition for a secondary battery according to claim 1, wherein the gel content of the first polymeric binder is 90% or less. The binder composition for a secondary battery according to claim 1, further comprising a binder that chemically bonds the first nanoparticles and the first polymeric binder. The binder composition for a secondary battery according to claim 1, wherein the binder composition for a secondary battery further comprises a solvent. Anode active material; And
An anode comprising the binder composition for a secondary battery according to any one of claims 1 to 12, and a binder composition for a secondary battery according to any one of claims 3 to 4, 9 and 11 to 15. The lithium _secondary battery according to claim 16, wherein the negative electrode active material is at least one selected from the group consisting of Si, Sn, Pb, Ge, Al, SiO _x (0 <x ≦ 2), SnO _y (0 <y ≦ 2), Li ₄ Ti ₅ O ₁₂ , LiTiO _3, and Li ₂ Ti ₃ O ₇ . A lithium battery employing the negative electrode according to claim 17.

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