KR101985758B1 - Separator and rechargable lithium battery including the separator - Google Patents

Abstract

A porous substrate, and a coating layer disposed on one or both surfaces of the porous substrate, the coating layer comprising: (A) a filler having an average particle diameter of 0.3 to 2 탆; And a binder containing (B) an inorganic particle, an organic particle or a combination thereof, and an organic polymer, wherein the inorganic particles and the organic particles have a mean particle size of 5 nm to 200 nm and a lithium The present invention relates to a secondary battery.

Description

[0001] SEPARATOR AND RECHARGABLE LITHIUM BATTERY INCLUDING THE SEPARATOR [0002]

A separator, and the separator.

In a conventional non-aqueous lithium secondary battery, a separator made of an electrically insulating porous film is interposed between a positive electrode and a negative electrode, and an electrolyte solution in which a lithium salt is dissolved is impregnated in the pores of the film. Such non-aqueous lithium secondary batteries have excellent characteristics of high capacity and high energy density. However, if the positive electrode and the negative electrode repeatedly shrink and expand due to the charge-discharge cycle, the separator or the electrolyte easily reacts with the positive electrode and the negative electrode to easily deteriorate, short-circuiting occurs inside and outside the battery, and the battery temperature may rise sharply . When the temperature of the battery rises, the separator melts and rapidly shrinks or breaks, short-circuiting again, resulting in a short circuit.

In order to prevent this, a conventional separator has been widely used as a porous film made of polyethylene which is excellent in terms of shutdown characteristics, handling property and cost. Here, shutdown means that the battery temperature rises due to overcharging, external or internal short-circuit, etc., and a part of the separator is melted to close the gap and interrupt the current.

In order to improve the safety of non-aqueous lithium secondary batteries, attempts have been made to improve the heat resistance of electrode materials such as separators. In particular, attempts have been made to secure safety even when the separator rapidly shrinks or breaks inside the battery ought.

A separator having a low residual moisture content and a low shrinkage rate at a high temperature, and a lithium secondary battery excellent in life characteristics and safety characteristics.

An embodiment of the present invention provides a separator comprising a porous substrate and a coating layer disposed on one or both sides of the porous substrate. Wherein the coating layer comprises (A) a filler having an average particle diameter of 0.3 to 2 占 퐉; And (B) a binder comprising inorganic particles, organic particles or a combination thereof, and an organic polymer. The average particle size of the inorganic particles and the organic particles is 5 nm to 200 nm.

The separator may further include an adhesive layer disposed on the coating layer.

Wherein the adhesive layer comprises a binder (B) comprising an inorganic particle, an organic particle or a combination thereof, and an organic polymer; Acrylate binders; Rubber binder; Dienic binder; A styrenic binder; Or a combination thereof.

Another embodiment of the present invention includes a porous substrate, a coating layer disposed on one or both sides of the porous substrate, and an adhesive layer disposed on the coating layer, wherein the coating layer comprises: (A) And a binder resin, wherein the adhesive layer comprises (B) an inorganic particle, an organic particle, or a combination thereof, and a binder containing an organic polymer, and the average particle diameter of the inorganic particle and the organic particle is 5 nm to 200 nm In separator.

In the coating layer, the binder resin may include an acrylic resin, a rubber resin, a diene resin, a styrene resin, or a combination thereof.

The binder (B) may be in the form of an inorganic particle, an organic particle or a combination thereof mixed with an organic polymer.

The glass transition temperature of the organic polymer (T _g) may be up to -50 ℃ to 60 ℃.

The organic polymer may include a diene polymer, an acrylate polymer, a styrene polymer, a urethane polymer, a polyolefin polymer, or a combination thereof.

The organic particles may be composed of an acrylate compound or a derivative thereof, a diallyl phthalate compound or a derivative thereof, a polyimide compound or a derivative thereof, a urethane compound or a derivative thereof, a copolymer thereof, or a combination thereof.

The organic particles may be cross-linked polymers. Specifically, the organic particles may be crosslinked polymethylmethacrylate (PMMA).

The glass transition temperature of the organic particles may be 60 DEG C or higher.

The organic particles may be specifically polyurethane.

Wherein the inorganic particles are selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , SnO ₂ , CeO ₂ , NiO, CaO, ZnO, MgO, ZrO ₂ , Y ₂ O ₃ , SrTiO ₃ , BaTiO ₃ , MgF ₂ , _2, or a combination thereof.

The binder (B) may further include an inorganic particle and an organic polymer, and may further include a binder that connects the inorganic particle and the organic polymer. The binder may be, for example, a silane coupling agent.

The binder may be included in an amount of 0.03 to 10 parts by weight based on 100 parts by weight of the organic polymer.

In the binder (B), inorganic particles, organic particles or a combination thereof may be contained in an amount of 10 to 100 parts by weight based on 100 parts by weight of the organic polymer.

The storage modulus of the binder (B) at 40 ° C may be from 50 MPa to 200 MPa, and the storage modulus at 100 ° C may be from 30 MPa to 150 MPa.

The filler (A) is contained in an amount of 70 to 99% by weight based on the total amount of the coating layer.

The filler (A) may be an inorganic compound, an organic compound or a combination thereof.

The inorganic compound in the filler (A) may be alumina, silica, boehmite, magnesia, or a combination thereof.

The organic compound in the filler (A) may be an acrylate compound or a derivative thereof, a diallyl phthalate compound or a derivative thereof, a polyimide compound or a derivative thereof, a polyurethane compound or a derivative thereof, a copolymer thereof or a combination thereof ≪ / RTI >

The filler (A) may be in the form of a plate.

The aspect ratio of the filler (A) may be 1: 5 to 1: 100.

The length ratio of the long axis to the short axis of the filler (A) may be 1 to 3.

The average angle of the flat surface of the filler (A) with respect to one surface of the porous substrate may be 0 to 30 degrees.

The filler (A) may be a structure in which primary particles aggregate to form secondary particles.

The thickness of the coating layer may be 0.1 to 5 mu m.

The porous substrate may be glass fiber, polyester, Teflon, polyolefin, polytetrafluoroethylene (PTFE), polyacrylonitrile, or a combination thereof.

The thickness of the separator may be 5 to 30 占 퐉.

In another embodiment of the present invention, there is provided a positive electrode comprising a positive electrode active material; A negative electrode comprising a negative electrode active material; Non-aqueous electrolytic solution; And the above-described separator existing between the positive electrode and the negative electrode.

Other details of the embodiments of the present invention are included in the following detailed description.

The separator for a lithium secondary battery according to an embodiment of the present invention has a small residual water content and a low shrinkage rate at a high temperature. The lithium secondary battery including the lithium secondary battery separator has excellent life characteristics and safety characteristics.

FIG. 1 is a schematic view of a lithium secondary battery according to an embodiment. Referring to FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

As used herein, the term " alkyl group " means a " saturated alkyl group " which does not include any alkene or alkynyl group unless otherwise defined. The alkyl group may be branched, straight-chain or cyclic.

The alkyl group may be a C1 to C20 alkyl group, specifically a C1 to C10 alkyl group. Specifically, it may be a C1 to C6 lower alkyl group, a C7 to C10 intermediate alkyl group, or a C11 to C20 higher alkyl group.

Typical examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, an ethenyl group, a propenyl group, a butenyl group, a cyclopropyl group, Pentyl group, cyclohexyl group, and the like.

&Quot; An aromatic group " means a substituent in which all the elements of the cyclic substituent have p-orbital, and these p-orbital forms a conjugation. Specific examples thereof include an aryl group and a heteroaryl group.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. Whenever a portion of a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case where it is "directly on" another portion, but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

An embodiment of the present invention provides a separator comprising a porous substrate and a coating layer disposed on one or both sides of the porous substrate. (A) a filler; And (B) a binder comprising inorganic particles, organic particles or a combination thereof, and an organic polymer.

The separator has a low residual water content, a low shrinkage rate at a high temperature, and excellent heat resistance. Therefore, the battery including the same can prevent a short between the positive and negative electrodes and secure the stability of the battery.

The separator may further include an adhesive layer disposed on the coating layer.

That is, the separator may include a porous substrate, a coating layer disposed on one or both surfaces of the porous substrate, and an adhesive layer disposed on the coating layer.

In this case, the coating layer includes a filler (A), and at least one of the coating layer and the adhesive layer includes a binder (B) containing inorganic particles, organic particles or a combination thereof and an organic polymer.

The binder (B) containing the inorganic particles, organic particles or a combination thereof and the organic polymer may be contained in either the coating layer or the adhesive layer, or may be included in both the coating layer and the adhesive layer. In any case, the separator is excellent in heat resistance, has a small amount of residual water, and exhibits a small shrinkage rate at a high temperature.

Hereinafter, each component will be described.

(A) a filler

The filler (A) may serve as a support in the separator. When the separator is intended to shrink at a high temperature, the filler (A) can support the separator to suppress shrinkage of the separator. Further, the separator includes the filler (A), thereby ensuring a sufficient porosity and improving mechanical properties. A lithium secondary battery including such a separator can secure excellent stability.

The average particle size of the filler (A) may be about 0.3 to 2 mu m. Specifically, the average particle diameter of the filler may be about 0.3 to 1.5 mu m and about 0.3 to 1.0 mu m. This average particle size can be defined as the diameter of the number average particle measured using a laser scattering particle size distribution analyzer (for example, Horiba LA-920). When the average particle diameter of the filler (A) satisfies the above range, the coating layer including the filler (A) may have an appropriate thickness, and the separator including the filler (A) may have a proper porosity.

The filler (A) may be included in an amount of about 70 to 99 parts by weight based on 100 parts by weight of the coating layer. Specifically about 71 to 99, about 70 to 90, about 80 to 99, about 80 to 90, and about 90 to 99 parts by weight. When the content of the filler satisfies the above range, the separator comprising the same can ensure a high porosity and can achieve a sufficient adhesive force.

The filler (A) may specifically be an inorganic compound, an organic compound or a combination thereof.

The inorganic compound may be a metal oxide, a metalloid oxide, or a combination thereof. Specifically, the inorganic compound may be alumina, silica, boehmite, magnesia, or a combination thereof. The alumina, silica and the like are small in particle size, and are easy to make a dispersion.

The inorganic compound may be in the form of a sphere or a plate. Examples of plate-like inorganic compounds include alumina and boehmite. In this case, reduction of the area of the separator at a high temperature is further suppressed, a relatively large porosity can be ensured, and characteristics can be improved at the time of penetration evaluation of the lithium secondary battery.

When the inorganic compound is in the form of a plate, the aspect ratio of the inorganic compound may be about 1: 5 to 1: 100. Specifically, it can be about 1:10 to 1: 100, about 1: 5 to 1:50, and about 1:10 to 1:50.

The length ratio of the long axis to the short axis of the flat surface of the inorganic compound may be 1 to 3. Specifically, it may be 1 to 2, and the closer to 1, the better.

The aspect ratio and the length ratio of the major axis to the minor axis can be measured by a scanning electron microscope (SEM) photograph. When the aspect ratio of the inorganic compound satisfies the above range, or when the length ratio of the long axis to the short axis of the flat surface of the inorganic compound satisfies the above range, the reduction of the separator area at high temperature is further suppressed, The porosity can be ensured and the characteristics can be improved at the time of penetration evaluation of the lithium secondary battery.

When the inorganic compound is in the form of a plate, the average angle of the flat surface of the inorganic compound with respect to one surface of the porous substrate may be 0 to 30 degrees. Specifically, when it is close to zero degree, that is, when the one surface of the porous substrate and the flat surface of the inorganic compound are parallel. When the average angle of the flat surface of the inorganic compound with respect to one surface of the porous substrate is within the above range, the heat shrinkage of the porous substrate can be effectively prevented, and the separator having a small heat shrinkage ratio can be provided.

The organic compound may be a cross-linked polymer. The organic compound is the glass transition temperature; may be a highly cross-linked polymer does not appear (Glass Transition Temperature T _g). When a crosslinked polymer at a high level is used, the heat resistance is improved and the shrinkage ratio of the porous substrate at high temperature can be effectively suppressed.

The organic compound specifically includes an acrylate compound and a derivative thereof, a diallyl phthalate compound and a derivative thereof, a polyimide compound and a derivative thereof, a polyurethane compound and derivatives thereof, a copolymer thereof or a combination thereof can do.

For example, the organic compound as the filler may be crosslinked polystyrene, or crosslinked polymethyl methacrylate.

The filler may be a structure in which primary particles aggregate to form secondary particles. In this case, the porosity of the coating layer can be increased, and a lithium secondary battery excellent in high output characteristics can be provided.

(B) Binder

The binder includes inorganic particles, organic particles or a combination thereof, and also includes an organic polymer. The binder may be a mixture of the inorganic particles, organic particles, or a combination thereof, in the organic polymer.

First, the organic polymer will be described.

In the binder, the organic polymer may be specifically in the form of an emulsion, a suspension or a colloid, and may include, for example, a diene polymer, an acrylate polymer, a styrene polymer, a urethane polymer, a polyolefin polymer or a combination thereof.

The organic polymer 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, fluorine rubber, polytetrafluoroethylene, There may be mentioned polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylate, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, poly Polyvinyl alcohol, carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, diacetylcellulose, or a combination thereof may be used in combination with at least one compound selected from the group consisting of vinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, .

The organic polymer can be obtained by a known production method such as emulsion polymerization or solution polymerization using a polymerizable monomer. In the polymerization, the polymerization temperature, the pressure at the time of polymerization, the method of adding the polymerizable monomer and the like, and the additives (polymerization initiator, molecular weight adjuster, pH adjuster, etc.) to be used are not particularly limited.

Examples of the polymerizable monomer used for obtaining the organic polymer include ethylenically unsaturated carboxylic acids such as methyl (meth) acrylate, butyl (meth) acrylate, ethyl (meth) acrylate and 2-ethylhexyl Alkyl esters; Cyano group-containing ethylenically unsaturated monomers such as acrylonitrile, methacrylonitrile, fumaronitrile,? -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, alkylstyrene and vinylnaphthalene; Fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether; Vinyl pyridine; Nonconjugated diene monomers such as vinyl norbornene, dicyclopentadiene and 1,4-hexadiene; ? -Olefins such as ethylene and propylene; Ethylenically unsaturated amide monomers such as (meth) acrylamide; And sulfonic acid-based unsaturated monomers such as acrylamide methyl propane sulfonic acid and styrene sulfonic acid.

The polymerizable monomer having a crosslinkable functional group may be contained in an amount of 5% by weight or less, for example, 2% by weight or less of the total polymerizable monomers used for obtaining the organic polymer.

The crosslinkable functional group is a functional group that can be a crosslinking point when crosslinking the organic polymer, and may be, for example, a hydroxyl group, a glycidyl group, an amino group, an N-methylol group, a vinyl group, or the like. Specific examples of the polymerizable monomer having a crosslinkable functional group include hydroxy esters of ethylenically unsaturated carboxylic acids such as hydroxyethyl (meth) acrylate and hydroxyethyl (meth) acrylate; Glycidyl esters such as ethylenically unsaturated carboxylic acids such as glycidyl (meth) acrylate; Amino esters of ethylenically unsaturated carboxylic acids such as dimethylaminoethyl (meth) acrylate; Methylol group-containing ethylenically unsaturated amides such as N-methylol (meth) acrylamide and N, N-dimethylol (meth) acrylamide; Monomers having two or more vinyl groups such as ethylene di (meth) acrylate and divinylbenzene; And the like.

The crosslinkable functional group may form a chemical bond by reacting with an organic bonding functional group of a binder described below. This is discussed in detail in the description of the binder below.

In the production of the organic polymer, for example, a water-soluble initiator such as persulfate and an oil-soluble initiator such as benzoyl peroxide may be used as the polymerization initiator. Examples of the molecular weight adjuster include mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan; alpha -methylstyrene dimer; Sulfoxides such as dimethyl xanthogen disulfide and diisopropyl xanthan disulfide; Nitrile compounds such as 2-methyl-3-butenitrile and 3-pentenenitrile; These may be used alone or in combination of two or more. For example, as the emulsifier, an anionic surfactant, a nonionic surfactant, etc. may be used alone or in combination. Reactive surfactants and protective colloids can also be used.

The organic polymer may have, for example, a glass transition temperature (Tg) of about -50 to 60 캜, and specifically about -40 to 20 캜.

The organic polymer may have a particle diameter of from about 0.05 탆 to about 0.5 탆, specifically, from about 0.08 탆 to about 0.2 탆. The particles having the above range of size can be used to have an appropriate viscosity and the safety characteristics of the lithium secondary battery including the separator having the coating layer made therefrom can be improved.

In addition, the organic polymer may have a pH of about 7 to about 10.5 to maintain stability. As the pH adjuster, for example, ammonia, an alkali metal hydroxide (lithium hydroxide, sodium hydroxide, potassium hydroxide) and the like can be used.

The organic polymer may be obtained by a known emulsion polymerization method or a transesterification method. The production conditions of the emulsion polymerization method and the transesterification method are not particularly limited.

Hereinafter, the inorganic particles, organic particles, or combinations thereof will be described.

The inorganic particles, organic particles or a combination thereof can be uniformly dispersed in the coating layer.

The inorganic particles, the organic particles, or a combination thereof can be mixed with the organic polymer to provide appropriate strength and heat resistance to the separator, thereby improving the safety of the lithium secondary battery including the separator.

The average particle size of the inorganic particles, organic particles or combinations thereof may be about 5 to 200 nm. Specifically 5 to 150 nm, 5 to 100 nm, 10 to 100 nm, and 5 to 50 nm. An appropriate strength can be imparted to the separator coating layer by using an inorganic compound having a size within the above range.

The inorganic particles, organic particles or a combination thereof may be contained in an amount of 10 to 100 parts by weight based on 100 parts by weight of the organic polymer. Specifically 20 to 80 parts by weight, and 20 to 60 parts by weight. When the inorganic particles, the organic particles, or the combination thereof is included in the above-described range, sufficient strength can be obtained and sufficient adhesion can be exhibited.

The kind of the inorganic particles may be the same as or different from the inorganic compound contained in the filler (A). Specifically, the inorganic particles may be selected from metal oxides, metalloid oxides, and metal fluorides. Wherein the inorganic particles are selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , SnO ₂ , CeO ₂ , NiO, CaO, ZnO, MgO, ZrO ₂ , Y ₂ O ₃ , SrTiO ₃ , BaTiO ₃ , MgF ₂ , Mg (OH) _2, or combinations thereof, but is not limited thereto. And more specifically colloidal silica or alumina fine particles, but is not limited thereto.

The inorganic compound may have, for example, an amorphous phase.

The inorganic particles may be hydrophilic particles such as hydroxy groups on the surface. The inorganic compound in which such hydrophilic particles are formed on the surface may have higher reactivity to the organic polymer or binder.

Meanwhile, when the binder contains an inorganic particle and an organic polymer, the binder may further include a binder that connects the inorganic particle and the organic polymer.

The binder can form a covalent bond with the inorganic particles and / or the functional groups existing in the organic polymer, so that the inorganic particles and the organic polymer can more firmly bond.

That is, in the binder, the organic polymer and the inorganic particles are organically connected via a binder. As a result, the coating layer can have excellent heat resistance even when the content of the inorganic particles is small, and the surface area of the organic polymer exposed on the surface of the coating layer is increased, so that the adhesion to the electrode plate can be improved.

The binder may be in the form of a reaction product with the inorganic particles and / or the organic polymer in the binder.

The binder may include functional groups that are reactive with polar functional groups. For example, the binder may include a functional group having reactivity with a carboxyl group, a functional group having a reactivity with a hydroxyl group, a functional group having a reactivity with an amine group, a functional group having a reactivity with an amine group, or a combination thereof.

Specifically, the binder may be a carbodiimide-based compound. For example, N, N'-di-o-tolylcarbodiimide, N, N'-diphenylcarbodiimide, N, N'-dioctyldecylcarbodiimide, N'-di-2,6-di-2,6-di-t-butylphenylcarbodiimide, N, N'- Butylphenylcarbodiimide, N, N'-di-p-nitrophenylcarbodiimide, N, N'-di-p-aminophenylcarbodiimide , N, N'-di-p-toluylcarbodiimide, N, N'-di-cyclohexylcarbodiimide, N, Di-o-tolylcarbodiimide, p-phenylene-bisdicyclohexylcarbodiimide, hexamethylene-bisdicyclohexylcarbodiimide, ethylene-bisdiphenylcarbodiimide, benzene- (1-methylethyl) homopolymer, 2,4-diisocyanato-1,3,5-tris (1-methylethyl) and 2,6-diisopropyl diisocyanate of Copolymers, or combinations thereof, but not always limited thereto, and any of them can be used as the carbodiimide compound in the art.

The carbodiimide-based compound in the binder may be present in the form of a reaction product with the inorganic particles and / or the organic polymer. For example, the diimide bond of the carbodiimide compound may exist in the form of a reaction product in which a new covalent bond is formed by reacting with a polar functional group on the surface of the inorganic particle.

For example, the binder may be a silane coupling agent. The silane coupling agent is an organosilicon compound having a hydrolyzable functional group. The hydrolyzable functional group is a functional group capable of binding with inorganic particles such as silica after hydrolysis. 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, and a hydroxyl group.

The silane coupling agent may specifically 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.

Specific examples of the silane coupling agent include vinyl alkylalkoxysilanes such as vinyltris (? -Methoxyethoxy) silane and? -Methacryloxypropyltrimethoxysilane; epoxyalkylalkoxysilanes such as? -glycidoxypropyltrimethoxysilane,? - (3,4-epoxycyclohexyl) ethyltrimethoxysilane and? -glycidoxypropylmethyldiethoxysilane; aminoalkylalkoxysilanes such as? -aminopropyltriethoxysilane; mercaptoalkylalkoxysilanes such as? -mercaptopropyltrimethoxysilane; halogenated alkylalkoxysilanes such as? -chloropropyltrimethoxysilane; Vinyl halosilanes such as vinyl trichlorosilane; Alkyl acyloxysilanes such as methyltriacetoxysilane; And the like, but not limited thereto, and any silane coupling agent that can be used in the technical field is possible.

The binder may also comprise an organic binding functional group. The organic bonding functional group is reactive with the crosslinkable functional group contained in the organic polymer described above.

The binder containing the organic bonding functional group may be used in the case where a part of the hydrolyzable groups described above function as an organic bonding functional group and the organic bonding functional group is added to the organic silicon compound having the illustrated hydrolyzable group May be used. The binder may bind to the organic polymer through an organic bonding functional group.

In addition to the above binders, hydrazine compounds, isocyanate compounds, melamine compounds, urea compounds, epoxy compounds, carbodiimide compounds, oxazoline compounds and the like can be used. In particular, an oxazoline compound, a carbodiimide compound, an epoxy compound, or an isocyanate compound may be used. But are not limited to, and can be used as long as they can be used as bonding agents in the art. These compounds may be used alone or in combination.

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) 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.

As the epoxy compound, Denacor series (EM-150, EM-101 and the like) available from Nagase Chemtech Corp., Adegjin EM-00517, EM-0526, EM-051R and EM-11-50B available from ADEKA can be used.

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.

The binder may be included in an amount of 0.03 to 10 parts by weight based on 100 parts by weight of the organic polymer. Specifically, about 0.03 to 5 parts by weight, 0.03 to 1 part by weight, 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, and 0.1 to 1 part by weight may be included.

When the content of the binder satisfies the above range, the binder can sufficiently bond the organic polymer and the inorganic particles, and thus the lithium secondary battery including the binder can secure sufficient heat resistance. Also, when the content of the binder is within the above range, a large amount of the unreacted binder remains, and deterioration of the characteristics of the lithium secondary battery including the binder can be prevented.

The kind of the organic particles may be the same as or different from that of the organic compound contained in the filler (A).

Specifically, the organic particles may be an acrylate compound or a derivative thereof, a diallyl phthalate compound or a derivative thereof, a polyimide compound or a derivative thereof, a urethane compound or a derivative thereof, a copolymer thereof or a combination thereof.

For example, the organic particles may be cross-linked polymers.

The organic particles may have a glass transition temperature (T _g ) of 60 ° C or higher. Specifically, the glass transition temperature of the organic particles may be 60 캜 to 600 캜, 60 캜 to 500 캜, and 60 캜 to 400 캜.

The organic particles having a glass transition temperature of 60 占 폚 or higher may be, for example, polyurethane.

The organic particles may be introduced with functional groups such as a carboxyl group, a hydroxyl group and an epoxy group in order to increase the reactivity with the organic polymer.

The inorganic particles, organic particles or a combination thereof can be used in a colloidal state. The colloidal particles may have acidity, neutrality or alkalinity, but may be alkaline, for example, at a pH of about 8.5 to about 10.5. By using the particles contained in the colloidal solution within the above pH range, it is possible to prevent agglomeration and gelation between particles while maintaining excellent storage stability.

As described above, the binder may be an inorganic particle, an organic particle, or a combination thereof mixed with an organic polymer. After the organic polymer is crosslinked, the binder may have a high heat resistance. For example, the storage elastic modulus at 100 ° C may range from 30 MPa to 150 Lt; / RTI > When the storage elastic modulus at 100 deg. C satisfies the above range, the separator containing the same can sufficiently suppress shrinkage at high temperature and can achieve excellent heat resistance.

The storage of the binder at 40 DEG C may also be from 50 MPa to 200 MPa. If the elastic modulus of the binder at room temperature is too large, the separator may be cracked, and a problem of powder dropping may occur when applying the coating layer. If the storage elastic modulus at 40 ° C of the binder satisfies the above range, such a problem can be avoided.

The coating layer may be formed by mixing the filler (A) and the binder (B) to prepare a composition for forming a coating layer, and then coating the composition on the porous substrate.

The coating layer may be present on one side or both sides of the porous substrate. The thickness of the coating layer may be 0.1 to 5 mu m, 0.5 to 5 mu m, or 1 to 5 mu m based on one surface. When the thickness of the coating layer satisfies the above range, the lithium secondary battery including the lithium secondary battery can secure sufficient heat resistance and can prevent a reduction in the capacity of the lithium secondary battery.

The porous substrate may be glass fiber, polyester, Teflon, polyolefin, polytetrafluoroethylene (PTFE), polyacrylonitrile, or a combination thereof. For example, the porous substrate may include a polyolefin such as polyethylene and polypropylene, and a multilayer film of two or more layers may be used. A polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene three layer separator, a polypropylene / / Polypropylene three-layer separator or the like may be used.

As mentioned above, the separator may further include an adhesive layer on the coating layer.

The adhesive layer can improve the binding force between the electrode plate and the separator. That is, in a pouch-type battery using a flexible packaging material such as a laminate film, the gap between the electrode and the separator can be more stably bonded to prevent the occurrence of a gap due to detachment of the electrode and the separator, and the position of the separator can be fixed.

The adhesive layer may specifically include a binder (B) containing inorganic particles, organic particles or a combination thereof, and an organic polymer; Acrylate binders; Rubber binder; Dienic binder; A styrenic binder; Or a combination thereof.

That is, the adhesive layer may include the above-mentioned binder (B), or may include a commonly used binder.

The description of the binder (B) comprising the inorganic particles, organic particles or combinations thereof and the organic polymer contained in the adhesive layer is as described above.

The acrylate-based binder means an acrylate-based polymer or copolymer, and may be, for example, a poly (meth) acrylate, a polyalkyl (meth) acrylate, a polyacrylonitrile, or a combination thereof.

The rubber binder may be, for example, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluorine rubber, . ≪ / RTI >

The diene-based binder is a binder obtained by polymerizing or copolymerizing a diene-based monomer, and examples of the diene-based monomer include butadiene and isoprene. Specific examples of the polymers obtained by polymerizing the diene-based monomer include butadiene rubber, acrylic rubber, styrene / butadiene rubber, acrylonitrile / butadiene rubber, isoprene rubber, and ethylene-propylene-diene terpolymer.

The styrene-based binder may include 20 to 100% by weight of a styrene-based monomer; And 0 to 80% by weight of a vinyl monomer may be used. The vinyl monomer may be an acrylic monomer, a heterocyclic monomer, an unsaturated nitrile monomer, or a combination thereof. As the styrenic monomer, styrene, C1 to C10 alkyl-substituted styrene, halogen-substituted styrene, or a combination thereof may be used.

Another embodiment of the present invention includes a porous substrate, a coating layer disposed on one or both sides of the porous substrate, and an adhesive layer disposed on the coating layer, wherein the coating layer comprises: (A) And a binder resin, wherein the adhesive layer comprises (B) an inorganic particle, an organic particle, or a combination thereof, and a binder containing an organic polymer, and the average particle diameter of the inorganic particle and the organic particle is 5 nm to 200 nm In separator.

This is the case where a common binder resin is used for the coating layer, and a binder (B) containing inorganic particles, organic particles or a combination thereof and an organic polymer is used for the adhesive layer. The separator also has a small residual water content, a low shrinkage rate at high temperature, and excellent heat resistance.

The description of the filler (A) and the binder (B) is the same as described above, and therefore will not be described.

The binder resin contained in the coating layer can be used without limitation as long as it is a commonly used binder resin. Specifically, the binder resin may include an acrylic resin, a rubber resin, a diene resin, a styrene resin, or a combination thereof.

The acrylic resin is an acrylate-based polymer or copolymer, and may be, for example, a poly (meth) acrylate, a polyalkyl (meth) acrylate, a polyacrylonitrile, or a combination thereof.

Examples of the rubber-based resin include styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluorine rubber, . ≪ / RTI >

The diene-based resin is a resin obtained by polymerizing or copolymerizing a diene-based monomer, and examples of the diene-based monomer include butadiene and isoprene. Specific examples of the polymers obtained by polymerizing the diene-based monomer include butadiene rubber, acrylic rubber, styrene / butadiene rubber, acrylonitrile / butadiene rubber, isoprene rubber, and ethylene-propylene-diene terpolymer.

The styrene-based resin includes 20 to 100% by weight of a styrene-based monomer; And 0 to 80% by weight of a vinyl monomer can be used. The vinyl monomer may be an acrylic monomer, a heterocyclic monomer, an unsaturated nitrile monomer, or a combination thereof.

In another embodiment of the present invention, there is provided a positive electrode comprising a positive electrode active material; A negative electrode comprising a negative electrode active material; Non-aqueous electrolytic solution; And the separator existing between the positive electrode and the negative electrode.

The lithium secondary battery can be classified into a lithium ion battery, a lithium ion physical gel polymer battery, and a lithium ion chemical gel polymer battery depending on the kind of a separator and an electrolyte to be used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, , And can be divided into a bulk type and a thin film type depending on the size. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

1 is an exploded perspective view of a lithium secondary battery according to one embodiment. 1, the lithium secondary battery 100 has a cylindrical shape and includes a cathode 112, a cathode 114, a separator 113 disposed between the cathode 112 and the anode 114, An electrolyte 114 (not shown), an electrolyte (not shown) impregnated into the separator 113, a battery container 120, and a sealing member 140 for sealing the battery container 120. The lithium secondary battery 100 is constructed by laminating a cathode 112, a separator 113 and an anode 114 in this order and then winding them in a spiral wound state in the battery container 120.

The separator 113 separates the cathode 112 and the anode 114 and provides a passage for lithium ions. The detailed description is as described above. The total thickness of the separator can be determined according to the capacity of the target battery. For example, the thickness of the separator may be from about 5 to about 30 microns.

The negative electrode 112 includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating lithium ions, any carbonaceous anode active material commonly used in lithium ion secondary batteries can be used as the carbonaceous material. Typical examples thereof include crystalline carbon , Amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, fired coke, and the like.

Examples of the lithium metal alloy include lithium and a metal such as Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Alloys may be used.

As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-Q alloy (Q is an alkali metal, an alkaline earth metal, A transition metal, a rare earth element or a combination thereof and not Si), Sn, SnO ₂ , Sn-C composite, Sn-R (wherein R is an alkali metal, an alkaline earth metal, A rare earth element or a combination thereof, but not Sn). The specific elements of Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Sb, Bi, S, Se, Te, Po, or a combination thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The negative electrode active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to adhere the negative electrode active material particles to each other and to adhere the negative electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, Polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic resin, polyvinyl chloride, Styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but the present invention is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any material can be used as long as it does not cause any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, , Carbon-based materials such as carbon fibers; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The anode 114 includes a current collector and a cathode active material layer formed on the current collector.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, it is possible to use at least one of complex oxides of cobalt, manganese, nickel or a combination of metals and lithium, and specific examples thereof include compounds represented by any one of the following formulas. Li _a A _1-b R _b D ₂ wherein, in the formula, 0.90? A? 1.8 and 0? B? 0.5; Li _a E _1-b R _b O _{2 -c} D _c wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, and 0? C? 0.05; LiE (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05) 2-b R b O 4-c D c; Li _a Ni _{1- b c} Co _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1- b c} Co _b R _c O _{2 -?} Z _? Wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1- b c} Co _b R _c O _2-α Z ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 <α <2; Li _a Ni _1-bc Mn _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _1-bc Mn _b R _c O _{2 -?} Z _? Wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _1-bc Mn _b R _c O _2-α Z ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 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 (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a MnG _b O ₂ wherein, in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1; Li _a Mn ₂ G _b O ₄ (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 ; LiTO 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); And LiFePO _4.

In the above formula, A is Ni, Co, Mn or a combination thereof; R 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; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T 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, as a coating element compound, an oxide, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a 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 carried out by any of coating methods such as spray coating, dipping, and the like without adversely affecting the physical properties of the cathode active material by using these elements in the above compound. It is a content that can be well understood by people engaged in the field, so detailed explanation will be omitted.

The cathode active material layer also includes a binder and a conductive material.

The binder serves to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

As the current collector, Al may be used, but the present invention is not limited thereto.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethyl ethyl acetate, methyl propionate , Ethyl propionate,? -Butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. As the alcoholic solvent, ethyl alcohol, isopropyl alcohol and the like can be used. As the aprotic solvent, R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, An amide such as nitriles such as dimethylformamide, and dioxolanes such as 1,3-dioxolane, sulfolanes, and the like can be used.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In the case of the carbonate-based solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1: 1 to about 1: 9, the performance of the electrolytic solution may be excellent.

The non-aqueous organic solvent may further include the aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of about 1: 1 to about 30: 1.

The aromatic hydrocarbon-based organic solvent may be an aromatic hydrocarbon-based compound represented by the following formula (1).

[Chemical Formula 1]

In Formula 1, R ₁ to R ₆ are each independently hydrogen, halogen, a C1 to C10 alkyl group, a C1 to C10 haloalkyl group, or a combination thereof.

The aromatic hydrocarbon-based organic solvent is selected from the group consisting of benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3- , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4 - triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 - trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4-diiodotol Ene, 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, or may be a combination thereof.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound represented by the following formula (2) to improve battery life.

(2)

Wherein R ₇ and R ₈ are each independently hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a C1 to C5 fluoroalkyl group, and at least one of R ₇ and R ₈ Is a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a C1 to C5 fluoroalkyl group.

Representative examples of the ethylene carbonate-based compound include, for example, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, . When the vinylene carbonate or the ethylene carbonate compound is further used, the amount of the vinylene carbonate or the ethylene carbonate compound can be appropriately controlled to improve the life.

The lithium salt is dissolved in the non-aqueous organic solvent to act as a source of lithium ions in the battery to enable operation of a basic lithium secondary battery, and a material capable of promoting the movement of lithium ions between the positive electrode and the negative electrode to be. The lithium salt Representative examples are _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiC 4 F 9 SO 3, LiClO 4, LiAlO 2, LiAlCl 4, LiN (C x F 2x + 1 SO 2) (C y F 2y ₊₁ SO ₂₎ (where, x and y are natural numbers), LiCl, LiI, LiB ( C 2 O 4) 2 ( lithium bis oxalate reyito borate (lithium bis (oxalato) borate; LiBOB) , or in a combination thereof The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity Can exhibit excellent electrolyte performance, and lithium ions can effectively migrate.

Example

Hereinafter, examples and comparative examples of the present invention will be described. The following embodiments are only examples of the present invention, and the present invention is not limited to the following embodiments.

Manufacture of separator

Example 1

Colloidal silica (manufactured by Nissan Chemical Industries, Ltd., Snowtex 0, solid content 20% by weight, average particle diameter: 50 nm) was added to 100 parts by dry weight of a dienic binder (BM451B, T _{g of} 5 ° C, ) Was added and stirred. Then, 2 parts by weight of? -Glycidoxypropyltrimethoxysilane was added as a binder and stirred to prepare a binder composition.

6 parts by weight of the binder composition prepared above and 0.5 parts by weight of a dispersant (AARON T-40, Toa Synthetic Agent) were mixed with 100 parts by weight of alumina (Aldrich) as a filler to obtain a composition for forming a coating layer.

The composition for forming a coating layer thus obtained was gravure printed on both sides of a polyethylene separator base material having a thickness of 16 탆 to prepare a separator. The thickness of the coating layer was 3 mu m on one side.

Example 2

A separator was prepared in the same manner as in Example 1, except that 30 parts by dry weight of inorganic particle colloidal silica was added.

Example 3

A separator was prepared in the same manner as in Example 1, except that 40 parts by dry weight of inorganic particle colloidal silica was added.

Example 4

Diene-based binder to the organic polymer (Zeon Corp. in Japan BM451B, T _g 5 ℃, gelryang 90%) EPOSTAR2B20, particle size of the poly (methyl methacrylate) (PMMA, Nippon shows Cuba moved crosslinked with organic particles to 100 dry parts by weight of 38nm , Solid content concentration: 10%) were added and stirred. Then, 1 part by weight of Carbosilite V02L2 from Nissin Chemical Industry Co., Ltd. as a binder was added and stirred to prepare a binder composition.

Thereafter, a separator was produced in the same manner as in Example 1.

Example 5

A separator was prepared in the same manner as in Example 4, except that 30 parts by dry weight of the organic particles were added.

Example 6

A separator was prepared in the same manner as in Example 4, except that 40 parts by dry weight of the organic particles were added.

Comparative Example 1

A separator was produced in the same manner as in Example 1, except that a dienic binder (BM451B, manufactured by Japan Xiong Kogyo Co., Ltd., T _{g of} 5 占 폚, gel amount of 90%) was used alone as a binder composition.

Comparative Example 2

Use only the diene-based binder (Japan Zeon Corporation BM451B, T _g 5 ℃, gelryang 90%) as the binder composition, with the exception that no filler was prepared using the separator in the same manner as in Example 1.

That is, a diene binder (BM451B manufactured by Zeon Corporation, Japan, T _{g of} 5 占 폚, gel amount of 90%) was gravure printed on both sides of a polyethylene separator base material alone to prepare a separator.

Manufacture of lithium secondary battery

Examples 7 to 12 and Comparative Examples 3 to 4

(anode)

LiCoO ₂ as a cathode active material, polyvinylidene fluoride (PVDF) as a binder and carbon as a conductive agent were mixed at a weight ratio of 92: 4: 4, and then dispersed in N-methyl-2-pyrrolidone to prepare a cathode slurry Respectively. This slurry was coated on an aluminum foil having a thickness of 20 mu m, followed by drying and rolling to prepare a positive electrode.

(cathode)

Styrene-butadiene rubber as a binder and carboxymethylcellulose as a thickener were mixed in a weight ratio of 96: 2: 2 and then dispersed in water to prepare a negative electrode active material slurry. This slurry was coated on a copper foil having a thickness of 15 mu m, followed by drying and rolling to prepare a negative electrode.

(Preparation of electrode)

A pouch-shaped battery was produced using the prepared positive electrode, negative electrode, and separator prepared in Examples 1 to 6 and Comparative Examples 1 and 2. A mixed solution of ethyl carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) (volume ratio of 3/5/2) containing LiPF ₆ of 1.3 M concentration was used as the electrolyte solution.

Evaluation example: Measurement of high temperature shrinkage ratio of separator

The separators of Examples 1 to 6 and Comparative Examples 1 and 2 were heat treated in a convection oven at 130 캜 and 150 캜 for 10 minutes, respectively, and then taken out of the oven, cooled at room temperature and measured for shrinkage. The results are shown in Table 1 below.

Shrinkage (%) 130 ℃ 150 ℃ Example 1 2 17 Example 2 1.8 13 Example 3 1.5 9 Example 4 2.3 21 Example 5 2.1 15 Example 6 1.8 11 Comparative Example 1 6 60 Comparative Example 2 5 42

As shown in Table 1, the separators of Examples 1 to 6 had remarkably improved shrinkage as compared with the separators of Comparative Examples 1 and 2. It should be noted that the present invention is not limited to the above embodiments, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

100: lithium secondary battery 112: cathode
113: separator 114: positive electrode
120: battery container 140: sealing member

Claims (15)

Porous substrate, and
And a coating layer disposed on one or both sides of the porous substrate,
The coating layer
(A) a filler having an average particle diameter of 0.3 탆 to 2 탆; And
(B) a binder in which the inorganic particles are mixed with the organic polymer,
The average particle diameter of the inorganic particles is 5 nm to 200 nm,
Wherein the inorganic particles are contained in an amount of 20 to 60 parts by weight based on 100 parts by weight of the organic polymer,
The glass transition temperature (T _g) of the organic polymer has a separator -50 ℃ to 60 ℃.
The method of claim 1,
Wherein the separator further comprises an adhesive layer disposed on the coating layer.
3. The method of claim 2,
The adhesive layer comprises a binder (B) comprising inorganic particles and an organic polymer; Acrylate binders; Rubber binder; Dienic binder; A styrenic binder; Or a combination thereof.
Porous substrates,
A coating layer disposed on one side or both sides of the porous substrate, and
And an adhesive layer disposed on the coating layer,
The coating layer
(A) a filler having an average particle diameter of 0.3 탆 to 2 탆, and
And a binder resin,
The adhesive layer
(B) a binder in which the inorganic particles are mixed with the organic polymer,
The average particle diameter of the inorganic particles is 5 nm to 200 nm,
Wherein the inorganic particles are contained in an amount of 20 to 60 parts by weight based on 100 parts by weight of the organic polymer,
The glass transition temperature (T _g) of the organic polymer has a separator -50 ℃ to 60 ℃.
5. The method of claim 4,
In the coating layer, the binder resin includes an acrylic resin, a rubber resin, a diene resin, a styrene resin, or a combination thereof.
The method according to claim 1 or 4,
Wherein the inorganic particles are contained in an amount of 20 to 40 parts by weight based on 100 parts by weight of the organic polymer.
delete The method according to claim 1 or 4,
In the binder (B), the organic polymer is a diene polymer, an acrylate polymer, a styrene polymer, a urethane polymer, a polyolefin polymer, or a combination thereof.
The method according to claim 1 or 4,
In the binder (B)
The inorganic particles are _{Al 2 O 3, SiO 2,} TiO 2, SnO 2, CeO 2, NiO, CaO, ZnO, MgO, ZrO 2, Y 2 O 3, SrTiO 3, BaTiO 3, MgF, Mg (OH) 2 , Or a combination thereof.
The method according to claim 1 or 4,
Wherein the binder (B) further comprises a binder that connects the inorganic particles and the organic polymer.
11. The method of claim 10,
Wherein the binder is contained in an amount of 0.03 to 10 parts by weight based on 100 parts by weight of the organic polymer.
The method according to claim 1 or 4,
The storage modulus of the binder (B) at 40 캜 is 50 MPa to 200 MPa,
And a storage modulus at 100 占 폚 of 30 MPa to 150 MPa.
The method according to claim 1 or 4,
Wherein the filler (A) having an average particle diameter of 0.3 to 2 占 퐉 is contained in an amount of 70 to 99% by weight based on the total amount of the coating layer.
The method according to claim 1 or 4,
Wherein the filler (A) having an average particle diameter of 0.3 탆 to 2 탆 is an inorganic compound, an organic compound or a combination thereof.
The method of claim 14,
Wherein the inorganic compound is alumina, silica, boehmite, magnesia, or a combination thereof.

Images