KR101708364B1 - Composite binder for battery, anode and lithium battery containing the binder - Google Patents

Abstract

Inorganic particles; Binder polymers; And an organic / inorganic binder; and a negative electrode and a lithium battery including the composite binder.

Description

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

A composite binder for a battery, and a negative electrode and a lithium battery employing the composite binder.

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.

Therefore, there is a demand for a binder capable of improving the lifetime characteristics of the lithium battery by accepting and / or inhibiting the volume change of the non-carbon anode active material.

One aspect is to provide a composite binder for a battery having an improved tensile strength.

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

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

According to one aspect,

Inorganic particles;

Binder polymers; And

And an organic / inorganic binder.

According to another aspect,

A negative electrode comprising the composite binder is provided.

According to another aspect,

A lithium battery employing the negative electrode is provided.

According to one aspect, inorganic particles; Binder polymers; And the organic binder, the cycle characteristics of the lithium battery can be improved.

1 is a schematic diagram of a composite binder according to an exemplary embodiment.
Fig. 2 shows the tensile strength test results of the composite binder produced in Example 1 and Comparative Example 1. Fig.
3 is a schematic diagram of a lithium battery according to an exemplary embodiment.
Description of the Related Art
1: Lithium battery 2: cathode
3: anode 4: separator
5: Battery case 6: Cap assembly

Hereinafter, a composite binder for a battery according to exemplary embodiments, a negative electrode including the same, and a lithium battery employing the negative electrode will be described in more detail.

In one embodiment, the composite binder for a battery comprises inorganic particles; Binder polymers; And an organic binder. The composite binder for a battery includes inorganic particles and a binder polymer, and the inorganic binder can bind to the binder polymer with the binder to have high strength, so that the change in volume of the negative electrode active material upon acceptance and / The cycle characteristics of the lithium battery including the composite binder can be improved.

The composite binder may be a binder solution including a solvent before being applied to a cathode. For example, the binder polymer particles may be dispersed in the solvent and the inorganic particles may be dispersed again in the binder polymer particles. The inorganic particles may be dispersed entirely uniformly in the binder polymer particles or mainly dispersed around the surface of the particles of the binder polymer depending on the kind of the binder polymer.

Therefore, even after the solvent is removed from the binder solution, the inorganic particles in the composite binder may be dispersed in the binder polymer.

The organic binder may be disposed on at least a part of the inorganic particles to bind the inorganic particles and the binder polymer. The organic binder may completely cover the inorganic particles or partially exist in the island type on the surface of the inorganic particles. The composite binder may have, for example, the shape shown in FIG. 1 in the binder solution.

The inorganic particles may be hydrophilic particles having a hydroxyl group on the surface thereof. The hydrophilic particles may have high reactivity with the binder polymer and the organic binder. In addition, the inorganic particles may have an amorphous phase.

The average particle size of the inorganic particles may be 1 nm to 1000 nm. For example, the average particle size of the inorganic particles may be 1 nm to 100 nm. For example, the average particle size of the inorganic particles may be 10 nm to 100 nm. If the average particle size of the inorganic particles is too small, the preparation may not be easy. If the average particle size is too large, the hardness of the binder may be low.

The inorganic particles may be at least one selected from the group consisting of metal oxides and metalloid oxides. For example, the inorganic particles may be at least one selected from the group consisting of silica, alumina, titania, magnesium fluoride, and zirconia.

The inorganic particles may be used in a colloidal state. The inorganic particles in the colloidal state may have acidity, neutrality or alkalinity, but may be, for example, a pH of 8 to 11. If the pH is too low, the colloidal inorganic particles can flocculate and gel, and if the pH is too high, the storage stability may be deteriorated.

The organic binder may be a silane-based compound. The organic binder may be a hydrolyzate of a silane coupling agent. The silane coupling agent may be 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.

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.

The binder polymer may be any polymer having a polar functional group capable of forming a bond such as a hydrogen bond with an inorganic particle. The polar functional group may be a carboxyl group, a hydroxyl group, or the like.

The glass transition temperature of the binder polymer may be from -50 캜 to 60 캜. For example, the glass transition temperature of the binder polymer may be from -40 占 폚 to 20 占 폚. A suitable binder hardness within the glass transition temperature range can be obtained.

For example, the binder 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, Polyolefins such as ethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylate, polyacrylonitrile, polystyrene, ethylene propylene diene air Polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose and diacetylcellulose And < RTI ID = 0.0 > Not all information is available as long as they can be used as the aqueous binder in the art.

Monomers used for preparing the binder polymer 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 binder polymer 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.

The binder polymer may have various forms and may be used, for example, in an emulsion state. The particle size of the polymer particles dispersed in the emulsion may be 0.05 to 1 탆. For example, the particle size of the polymer particles may be 0.05 to 0.5 탆. For example, the particle size of the polymer particles may be 0.05 to 0.2 탆. If the particle size of the polymer particles dispersed in the emulsion is too small, the viscosity of the emulsion becomes high and the handling is not easy. If the particle size of the polymer particle is too large, the initial adhesion force may be decreased.

The emulsion may be in the range of pH 7-11 to maintain stability. Ammonia and hydroxides of alkali metals may be used as the pH adjusting agent.

The content of the binder polymer, the inorganic particles and the organic binder in the battery composite binder may be 1 to 30 parts by weight of the inorganic particles and 0.01 to 5 parts by weight of the organic binder with respect to 100 parts by weight of the binder polymer. For example, the mixing ratio may be 3 to 15 parts by weight of the inorganic particles and 0.01 to 5 parts by weight of the organic binder to 100 parts by weight of the binder polymer.

The negative electrode according to another embodiment includes the negative electrode active material and the above-described composite binder for a battery. The negative electrode may be manufactured, for example, by forming the negative electrode active material composition comprising the negative electrode active material and the composite binder for a battery into a predetermined shape or applying the negative electrode active material composition to a current collector such as copper foil .

Specifically, a negative electrode active material composition in which a negative electrode active material, a conductive material, the composite binder, and a solvent are mixed 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 metal that can be alloyed with lithium is at least one element selected from the group consisting of Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloys (Y is at least one element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, (Wherein Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination element thereof, and not a Sn element) ) And 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, Ti, Ge, P, As, Sb, Se, 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 an amorphous, plate-like, flake, spherical or fibrous shape, and the amorphous carbon may be soft carbon or hard carbon carbon black, carbon black, carbon fiber, copper carbon black, mesophase pitch carbonitride, calcined cokes, etc. The conductive material may include acetylene black, ketjen black, natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination of two or more. However, the present invention is not limited thereto. Anything that can be used as a conductive material in the field can be used. In addition, the above-described crystalline carbon-based material can be added as a conductive material.

In addition to the composite composite binder, conventional conventional binders may be further used. Exemplary 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 composite negative electrode active material, the conductive material, the binder, and the solvent is a level commonly used in a lithium battery. At least one of the conductive material, the binder and the solvent may be omitted depending on the use and configuration of the lithium battery.

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 which does not adversely affect the 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, binder and solvent in the positive electrode active material composition, the same materials as those of 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 binder, and the solvent is a level commonly used in a lithium battery. Depending on the application and configuration of the lithium battery, one or more of the conductive material, the binder, and the 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. 3, 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.

A separator may be disposed between the anode and the cathode to form a battery structure. The cell structure is laminated in a bi-cell structure, then impregnated with an organic electrolyte solution, and the obtained result 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 composite binder for a battery may be prepared by mixing a binder polymer emulsion, a silane coupling agent and an inorganic particle colloid.

For example, by adding a colloid of an inorganic particle to a binder polymer emulsion and then adding a silane coupling agent, colloidal inorganic particles penetrate into the binder polymer particles dispersed in the emulsion by diffusion or the like, and then the silane coupling agent The composite binder composition can be obtained by bonding the inorganic particles and the binder polymer through a hydrolysis reaction. The solvent in the composition may be water but is not necessarily limited to water, and any solvent capable of hydrogen bonding is possible.

The composite binder composition is generally prepared in a solution state. When the solvent is removed, the composite binder composition may be present in the electrode in the form of a binder polymer, a silane-based compound that is an organic binder, and inorganic particles.

The mixing ratio of the binder polymer emulsion, the silane coupling agent and the inorganic particle colloid in the composition may be 1 to 30 parts by weight of the inorganic particle colloidal dry powder and 0.01 to 5 parts by weight of the silane coupling agent based on 100 parts by weight of the binder polymer emulsion dry matter. For example, the mixing ratio may be 3 to 15 parts by weight of an inorganic particle colloidal dry powder and 0.01 to 5 parts by weight of a silane coupling agent based on 100 parts by weight of the dried binder polymer emulsion.

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 polymer emulsion)

Preparation Example 1:

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, 60 parts by weight of distilled water and 1.5 parts by weight of sodium dodecylbenzenesulfonate were added, The temperature was raised. Subsequently, 2 parts by weight of styrene was added to the reactor and stirred for 5 minutes. Then, 10 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 30 parts by weight of 2-ethylhexyl acrylate, 68 parts by weight of styrene, 2 parts by weight of acrylic acid, 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, 6 parts by weight of a 5% ammonium persulfate aqueous solution was added dropwise to the reactor for 3 hours. After completion of the dropwise addition of the monomer emulsion, the reaction was further carried out for 2 hours, followed by cooling to 20 DEG C, followed by decompression to remove the residual monomer to obtain a polymer emulsion. The particle size of the polymer particles dispersed in the emulsion was 100 to 200 nm.

Preparation Example 2:

After replacing nitrogen in a 10 L autoclave reactor, 60 parts by weight of distilled water and 1.5 parts by weight of sodium dodecylbenzenesulfonate were added and the temperature was raised to 70 占 폚. Subsequently, 2 parts by weight of styrene was added to the reactor, stirred for 5 minutes, and then 10 parts by weight of a 2% aqueous solution of potassium persulfate was added to the reactor to initiate the reaction. After 1 hour, 40 parts by weight of butadiene, 46 parts by weight of styrene, 10 parts by weight of methyl methacrylate, 3 parts by weight of itaconic acid, 1 part by weight of hydroxyethyl acrylate, 0.5 part by weight of sodium dodecylbenzenesulfonate, Was added dropwise to the reactor over a period of 4 hours. At the same time, 10 parts by weight of a 2% aqueous solution of potassium persulfate was added dropwise over 3 hours. After completion of the dropwise addition of the monomer emulsion, the reaction was further carried out for 3 hours, followed by cooling to 20 DEG C, followed by decompression to remove the residual monomer, and then a polymer emulsion was obtained.

(Preparation of composite binder)

Example 1

5 parts by weight, based on dry weight of colloidal silica (solid content 20% by weight) having an average particle size of 50 nm, based on the dry weight of the polymer emulsion (solid content 40% by weight) prepared in Preparation Example 1, , And the mixture was stirred for 10 minutes. Then, 0.2 part by weight of? -Glycidoxypropyltrimethoxysilane as a silane coupling agent was added and stirred for 20 minutes to prepare a composite binder composition.

Example 2

A composite binder composition was prepared in the same manner as in Example 1, except that the polymer emulsion prepared in Preparation Example 2 was used.

Example 3

A composite binder composition was prepared in the same manner as in Example 1, except that colloidal alumina (solid content 20 wt%) having an average particle diameter of 50 nm was used instead of colloidal silica having an average particle diameter of 50 nm (solid content 20 wt%).

Example 4

A composite binder composition was prepared in the same manner as in Example 2 except that colloidal alumina (solid content 20% by weight) having an average particle diameter of 50 nm was used instead of colloidal silica having an average particle diameter of 50 nm (solid content 20% by weight).

Comparative Example 1

The polymer emulsion prepared in Preparation Example 1 was used as a binder.

Comparative Example 2

The polymer emulsion prepared in Preparation Example 2 was used as a binder.

Comparative Example 3

Polyimide (20 wt%, Hitachi Chemical, HCI 1300) dissolved in a solvent of NMP (N-methylpyrrolidone) was directly used as a binder.

(Preparation of negative electrode and lithium battery)

Example 5

(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 composite binder prepared in Example 1 was added to prepare an active material slurry so that the weight ratio of Si-Fe alloy: graphite: CMC: composite binder (solid content) = 20: 77: 1: 2.

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.

Example 6

A negative electrode and a lithium battery were produced in the same manner as in Example 5 except that the composite binder prepared in Example 2 was used.

Example 7

A negative electrode and a lithium battery were prepared in the same manner as in Example 5 except that the composite binder prepared in Example 3 was used.

Example 8

A negative electrode and a lithium battery were prepared in the same manner as in Example 5 except that the composite binder prepared in Example 4 was used.

Comparative Example 4-5

A negative electrode and a lithium battery were prepared in the same manner as in Example 5 except that the binder prepared in Comparative Example 1-2 was used.

Comparative Example 6

(3M, Minnesota, USA, CV3) and artificial graphite (Hitachi Chemical, Tokyo, Japan, MAG) having an average particle size (d50) of 3 mu m were mixed in pure water, The binder was added to prepare an active material slurry so that the weight ratio of Si-Fe alloy: graphite: binder (solid content) = 18.97: 73.03: 8.

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.

Evaluation Example 1: Tensile test

Specimens were prepared using the composite binder composition of Example 1 and the binder composition of Comparative Example 1, respectively. The stress-strain diagram of FIG. 2 was prepared by measuring the strain according to the stress using a tensile tester manufactured by Instron according to ASTM specification.

As shown in Fig. 2, the composite binder of Example 1 had a significantly improved tensile strength as compared with the binder of Comparative Example 1. Fig.

Evaluation Example 2: Evaluation of charge / discharge characteristics

The coin cells prepared in Examples 5 to 8 and Comparative Examples 4 to 6 were subjected to constant current charging at a current of 0.2 C rate at 25 DEG C until the voltage reached 0.01 V (vs. Li) And the cells were subjected to constant-voltage charging until the current reached 0.01C. Then, at the time of discharging, the battery was discharged at a constant current of 0.2 C until the voltage reached 1.5 V (vs. Li) (Mars phase)

The lithium battery having undergone the above conversion step was charged with a constant current until the voltage reached 0.01 V (vs. Li) at a current of 0.5 C rate at 25 ° C, and charged at a constant voltage until the current became 0.01 C while maintaining the voltage at 0.01 V . Subsequently, a cycle of discharging at a constant current of 0.5 C was repeated 30 times until the voltage reached 1.5 V (vs. Li) at the discharge time.

Part of the charge-discharge test results are shown in Table 1 below. The charging / discharging efficiency and the capacity retention rate at the Mars stage are defined by the following equations (1) and (2). The performance of the lithium battery was qualitatively divided into phase and phase.

&Quot; (1) &quot;

Charging / discharging efficiency at the Mars stage = [Discharging capacity at the Mars stage / Charging capacity at the Mars stage] × 100

&Quot; (2) &quot;

Capacity retention rate = [Discharge capacity in 30 ^th cycle / Discharge capacity in 1 ^st cycle] × 100

At the Martian stage
Charge / discharge efficiency At 30 ^th cycle
Capacity retention rate Example 7 91.3 90.1 Example 8 91.8 89.9 Comparative Example 4 92.5 84.7 Comparative Example 5 92.4 84.8 Comparative Example 6 79.2 95.7

As shown in Table 1, the lithium batteries of Examples 7 to 8 exhibited similar initial efficiency and improved life characteristics as compared with the lithium batteries of Comparative Examples 4 to 5. On the other hand, the lithium battery of Comparative Example 6 improved lifetime characteristics by using a polyimide binder having a high strength, but the ionic conductivity was low and the initial efficiency was very low.

Therefore, the lithium battery including the composite binder of the present invention can simultaneously provide excellent initial efficiency and lifetime characteristics.

Claims (20)

Inorganic particles;
Binder polymers; And
An organic binder,
Wherein the inorganic binder binds the inorganic particles and the binder polymer,
Wherein the inorganic particles are at least one selected from the group consisting of silica, alumina, titania, magnesium fluoride, and zirconia,
Wherein the organic binder is a hydrolyzate of a silane coupling agent and the silane coupling agent comprises at least one 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,
Wherein the binder polymer is 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, polyethylene , Polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylate, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinyl One selected from the group consisting of pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose and diacetylcellulose &Lt; / RTI &gt;
Wherein a tensile modulus of the binder polymer is larger than that of the binder polymer. The composite binder for a battery according to claim 1, wherein the inorganic particles are dispersed in the binder polymer. The composite binder for a battery according to claim 1, wherein the inorganic binder is disposed on at least a part of the inorganic particles. The composite binder for a battery according to claim 1, wherein the inorganic particles are hydrophilic particles. The composite binder for a battery according to claim 1, wherein the inorganic particles are in an amorphous phase. The composite binder for a battery according to claim 1, wherein the inorganic particles have an average particle diameter of 1 nm to 1000 nm. delete delete delete delete delete The composite binder for a battery according to claim 1, wherein the silane coupling agent is at least one selected from the group consisting of a vinyl alkyl alkoxy silane, an epoxy alkyl alkoxy silane, a mercaptoalkyl alkoxy silane, a vinyl halosilane and an alkyl acyloxy silane. The composite binder for a battery according to claim 1, wherein the binder polymer has a glass transition temperature of -50 캜 to 60 캜. The composite binder for a battery according to claim 1, wherein the binder polymer comprises at least one functional group selected from the group consisting of a carboxyl group and a hydroxy group. delete Anode active material; And
An anode comprising the composite binder for a battery according to any one of claims 1 to 6 and 12 to 14. The negative electrode according to claim 16, wherein the negative active material is a non-carbon-based material. 17. The lithium secondary battery according to claim 16, wherein the negative electrode active material is 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 / RTI &gt; 17. The method of claim 16, wherein the negative electrode active material is Si, Sn, Pb, Ge, Al, SiOx (0 <x≤2), SnOy (0 <y≤2), Li 4 Ti 5 O 12, TiO 2, LiTiO 3 And Li ₂ Ti ₃ O ₇ . A lithium battery employing the negative electrode according to claim 16.

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