KR20130092439A - Composite binder for battery, anode and lithium battery containing the binder - Google Patents

Abstract

PURPOSE: A battery complex binder is provided to improve the lifetime and cycle property of a lithium battery by accepting and/or suppressing the volume change of non-carbon system negative electrode active materials. CONSTITUTION: A battery complex binder comprises inorganic particles, binder polymers and organic and inorganic binders. The inorganic particles are dispersed within the binder polymers. The organic and inorganic binders are arranged in at least a portion of the inorganic particles. The inorganic particles are at least one selected from a group consisting of metal oxide and metalloid oxide. The organic and inorganic binders are silane compounds or silane coupling agents. A negative electrode includes negative electrode active materials and the complex binder for a battery.

Description

Combined binder for battery, anode and lithium battery containing the binder

It relates to a battery composite binder, a negative electrode and a lithium battery employing the same.

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

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

Provided is a battery composite binder comprising an organic-inorganic binder.

According to another aspect,

A negative electrode including 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; Cycle characteristics of the lithium battery can be improved by including a composite binder including and an organic-inorganic binder.

1 is a schematic diagram of a composite binder according to an exemplary embodiment.
2 is a tensile strength test results of the composite binder prepared in Example 1 and Comparative Example 1.
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 battery composite binder according to exemplary embodiments, a negative electrode including the same, and a lithium battery using the negative electrode will be described in more detail.

In another embodiment, a battery composite binder includes inorganic particles; Binder polymers; And organic-inorganic binders. The battery composite binder includes an inorganic particle and a binder polymer, and the organic-inorganic binder may have a high strength by binding the inorganic particle and the binder polymer, thereby accommodating and / or inhibiting a volume change of the negative electrode active material during charging and discharging. By doing so, the cycle characteristics of the lithium battery including the composite binder can be improved.

The composite binder may be a binder solution containing a solvent before being applied to the negative electrode. 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 uniformly dispersed in the binder polymer particles as a whole according to the kind of the binder polymer, or mainly dispersed around the surface of the particles of the binder polymer.

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

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

The inorganic particles may be hydrophilic particles in which a hydroxyl group or the like may exist on a surface thereof. The hydrophilic particles may be highly reactive with the binder polymer and the organic-inorganic binder. In addition, the inorganic particles may have an amorphous phase.

The average particle diameter of the inorganic particles may be 1nm to 1000nm. For example, the average particle diameter of the inorganic particles may be 1nm to 100nm. For example, the average particle diameter of the inorganic particles may be 10nm to 100nm. If the average particle diameter of the inorganic particles is too small, it may not be easy to manufacture. If the average particle diameter 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 the colloidal state. The colloidal inorganic particles may be acidic, neutral or alkaline, but may be, for example, pH 8-11. When the pH is too low, the colloidal inorganic particles may aggregate and gel, and when the pH is too high, storage stability may decrease.

The organic-inorganic binder may be a silane compound. The organic-inorganic binder may be a hydrolyzate of the 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 bonding with inorganic particles such as silica after hydrolysis. For example, the silane coupling agent may include one or more 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 an inorganic particle and a hydrogen bond. 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 -50 ℃ to 60 ℃. For example, the glass transition temperature of the binder polymer may be -40 ℃ to 20 ℃. A suitable binder hardness can be obtained within the glass transition temperature range.

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, 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 to prepare the binder polymers include, for example, ethylene 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; Ethylenic unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, 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; Α-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 in an emulsion state, for example. The particle diameter of the polymer particles dispersed in the emulsion may be 0.05 to 1㎛. For example, the particle size of the polymer particles may be 0.05 to 0.5㎛. For example, the particle size of the polymer particles may be 0.05 to 0.2㎛. When the particle size of the polymer particles dispersed in the emulsion is too small, the viscosity of the emulsion is high, and handling is not easy. When the particle size of the polymer particles is too large, the initial adhesive strength may decrease.

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.

In the battery composite binder, the content of the binder polymer, the inorganic particles, and the organic / inorganic binder may be 1 to 30 parts by weight of the inorganic particles and 0.01 to 5 parts by weight of the inorganic binder based on 100 parts by weight of the binder polymer. For example, the mixing ratio may be 3 to 15 parts by weight of inorganic particles and 0.01 to 5 parts by weight of inorganic binder based on 100 parts by weight of the binder polymer.

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

Specifically, a negative electrode active material composition containing a negative electrode active material, a conductive material, the composite binder and a solvent is prepared. The negative electrode active material composition is directly coated on a metal current collector to prepare a negative electrode plate. Alternatively, the negative electrode active material composition may be cast on a separate support, and then a film peeled from the support may be laminated on a metal current collector to prepare 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.

Specifically, 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 , Li ₂ It may be one or more selected from the group consisting of Ti ₃ O ₇ , but is not necessarily limited to these, any non-carbon-based negative active material may be used as long as used in the art.

In addition, a composite of the non-carbon-based negative electrode active material and the carbon-based material may also be used, and may further include a carbon-based negative electrode active material in addition to the non-carbon-based material.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite, and the amorphous carbon may be soft carbon (low temperature calcined carbon) or hard carbon (hard). carbon, mesophase pitch carbide, calcined coke, etc. The conductive material may be acetylene black, ketjen black, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, Metal powders, such as nickel, aluminum, silver, metal fiber, etc. can be used, and also conductive materials, such as a polyphenylene derivative, can be used 1 type or in mixture of 1 or more types, It is not limited to these, 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, a conventional general binder may be additionally used. Known conventional binders include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polytetrafluoroethylene and mixtures thereof or styrene butadiene Rubber-based polymers and the like can be used, but are not limited to these, any one that can be used as a binder in the art can be used.

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

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

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

For example, LiNiO ₂ , LiCoO ₂ , LiMn _x O _2x (x = 1, 2), LiNi _1-x Mn _x O ₂ (0 <x <1), LiNi _1-xy Co _x Mn _y O ₂ (0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5), LiFeO ₂ , V ₂ O ₅ , TiS, MoS and the like can be used.

In the positive electrode active material composition, the same conductive material, binder, and solvent may be used as the case of the negative electrode active material composition. 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 amount of the positive electrode active material, the conductive material, the binder, and the solvent is at a level commonly used in lithium batteries. 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. For example, 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 , Benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide , Dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether or a mixture 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 a positive electrode 3, a negative electrode 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 positive electrode and the negative electrode 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, it can be used in notebooks, smartphones, electric vehicles and the like.

In particular, the lithium battery is suitable for an electric vehicle (EV) because of its high rate characteristics and longevity characteristics. For example, it is suitable for a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV).

The battery composite binder may be prepared by mixing a binder polymer emulsion, a silane coupling agent and an inorganic particle colloid.

For example, colloidal inorganic particles are added to the binder polymer emulsion followed by the addition of the silane coupling agent, so that the colloidal inorganic particles penetrate into the binder polymer particles dispersed in the emulsion by diffusion or the like, and then the silane coupling agent is The composite binder composition may 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, any solvent capable of hydrogen bonding.

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

In the composition, the mixing ratio of the binder polymer emulsion, the silane coupling agent and the inorganic particle colloid may be 1 to 30 parts by weight of the inorganic particle colloid 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 powder. For example, the mixing ratio may be 3 to 15 parts by weight of the inorganic particle colloid 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 powder.

The present invention will be described in more detail by way of the following examples and comparative examples. However, the examples are provided to illustrate the present invention, and the scope of the present invention is not limited only to these examples.

(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 5% aqueous solution of ammonium persulfate was added dropwise to the reactor for 3 hours. After the completion of the dropwise addition of the monomer emulsion, the reaction was further performed for 2 hours, cooled to 20 ° C., and then removed under reduced pressure to obtain a polymer emulsion. The particle diameter of the polymer particles dispersed in the emulsion was 100-200 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 the completion of the dropwise addition of the monomer emulsion, the reaction was further performed for 3 hours, cooled to 20 ° C., and then removed under reduced pressure to remove the residual monomer, thereby obtaining a polymer emulsion.

(Manufacture of Compound Binder)

Example 1

5 parts by weight of dry weight of colloidal silica (solid content 20% by weight) having an average particle diameter of 50 nm to 100 parts by weight of dry weight of the polymer emulsion (solid content 40% by weight) prepared in Preparation Example 1 with lithium hydroxide pH 8 The mixture was added to the mixture and stirred for 10 minutes, and then 0.2 part by weight of γ-glycidoxypropyltrimethoxysilane, which was 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 having a mean particle size of 50 nm (solid content of 20 wt%) was used instead of colloidal silica having a mean particle size of 50 nm (solid content of 20 wt%).

Example 4

A composite binder composition was prepared in the same manner as in Example 2, except that colloidal alumina having a mean particle size of 50 nm (solid content of 20 wt%) was used instead of colloidal silica having a mean particle size of 50 nm (solid content of 20 wt%).

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 as it is.

Comparative Example 3

Polyimide (20% by weight, Hitachi Chemical, HCI 1300) dissolved in NMP (N-methyl pyrrolidone) solvent was obtained directly and used as a binder.

(Preparation of negative electrode and lithium battery)

Example 5

Si-Fe alloy active material (3M, Minnesota, USA, CV3), artificial graphite (Hitachi Kasei, Tokyo, Japan, MAG) and carboxymethyl cellulose (CMC) having an average particle diameter (d50) of 3 µm were mixed in pure water, and The composite binder prepared in Example 1 was added to prepare an active material slurry such that a 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) .

Metal lithium was used as a counter electrode in the cell manufacturing. A 20 μm thick polyethylene separator (Star ^® 20) was used as the separator, and EC (ethylene carbonate): EMC (ethyl methyl carbonate): DEC was used as the electrolyte. (Diethyl carbonate) (3: 3: 4 volume ratio) What dissolved 1.15 M LiPF ₆ in the mixed solvent was used.

Example 6

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

Comparative Example 6

Si-Fe alloy active material (3M, Minnesota, USA, CV3) and artificial graphite (Hitachi Chemicals, Tokyo, Japan, MAG) having an average particle diameter (d50) of 3 μm were mixed in pure water, and prepared in Comparative Example 3 above. The binder was added to prepare an active material slurry such that a 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) .

Metal lithium was used as a counter electrode in the cell manufacturing. A 20 μm thick polyethylene separator (Star ^® 20) was used as the separator, and EC (ethylene carbonate): EMC (ethyl methyl carbonate): DEC was used as the electrolyte. (Diethyl carbonate) (3: 3: 4 volume ratio) What dissolved 1.15 M LiPF ₆ in the mixed solvent was used.

Evaluation Example 1 Tensile Test

Specimens were each prepared using the composite binder composition of Example 1 and the binder composition of Comparative Example 1. The binder specimens were prepared using a tensile tester manufactured by Instron in accordance with ASTM to measure strain according to stress to prepare a stress-strain diagram of FIG. 2.

As shown in FIG. 2, the composite binder of Example 1 was significantly improved in tensile strength compared to the binder of Comparative Example 1.

Evaluation Example 2: Evaluation of charge / discharge characteristics

The coin cells prepared in Examples 5 to 8 and Comparative Examples 4 to 6 were charged at a constant current until the voltage reached 0.01 V (vs. Li) at a current of 0.2 C at 25 ° C., while maintaining 0.01 V. Constant voltage charge was carried out until current became 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 time of discharge.

Some of the charge and discharge test results are shown in Table 1 below. Charge and discharge efficiency and capacity retention rate in the chemical conversion step is defined by the following equations (1) and (2). The performance of the lithium battery was qualitatively divided into upper and lower parts.

&Quot; (1) &quot;

Charge / discharge efficiency in the chemical phase = [discharge capacity in the chemical phase / charge capacity in the chemical phase] × 100

&Quot; (2) &quot;

Capacity maintenance rate = [30 discharge capacity / 1 ^st cycle discharge capacity at in ^th cycle] × 100

In the Mars phase
Charge and 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 lifetime characteristics as compared to the lithium batteries of Comparative Examples 4 to 5. On the other hand, the lithium battery of Comparative Example 6 using a high-strength polyimide binder improved the life characteristics, but the initial efficiency was very low due to the low ion conductivity.

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

Claims (20)

Inorganic particles;
Binder polymers; And
An organic-inorganic binder; Battery composite binder comprising a. The composite binder of claim 1, wherein the inorganic particles are dispersed in the binder polymer. The composite binder according to claim 1, wherein the organic-inorganic binder is disposed on at least a portion of the inorganic particles. The composite binder of claim 1, wherein the inorganic particles are hydrophilic particles. The composite binder of claim 1, wherein the inorganic particles are in an amorphous phase. The composite binder according to claim 1, wherein the inorganic particles have an average particle diameter of 1 nm to 1000 nm. The composite binder of claim 1, wherein the inorganic particles are at least one selected from the group consisting of metal oxides and metalloid oxides. The composite binder according to claim 1, wherein the inorganic particles are at least one selected from the group consisting of silica, alumina, titania, magnesium fluoride and zirconia. The composite binder according to claim 1, wherein the organic-inorganic binder is a silane compound. The composite binder according to claim 1, wherein the organic-inorganic binder is a hydrolyzate of a silane coupling agent. The binder according to claim 10, wherein 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. The composite binder according to claim 10, wherein the silane coupling agent is at least one selected from the group consisting of vinylalkylalkoxysilane, epoxyalkylalkoxysilane, mercaptoalkylalkoxysilane, vinylhalosilane and alkylacyloxysilane. The composite binder according to claim 1, wherein the binder polymer has a glass transition temperature of -50 ° C to 60 ° C. The composite binder of claim 1, wherein the binder polymer comprises one or more functional groups selected from the group consisting of carboxyl groups and hydroxy groups. The method of claim 1, wherein the binder polymer is a styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluorine rubber, poly Tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylate, polyacrylonitrile, polystyrene, ethylene propylene Diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylmethylcellulose, hydroxypropyl cellulose and diacetyl cellulose Compound Vine containing one or more selected from the group consisting of . Anode active material; And
A negative electrode comprising the battery composite binder according to any one of claims 1 to 15. The negative electrode of claim 16, wherein the negative electrode active material is a non-carbon based material. The method of 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. A cathode comprising a. The method of claim 16, wherein the anode 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 One or more negative electrode selected from the group consisting of. A lithium battery employing the negative electrode according to claim 16.

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