KR20200036177A - Binder composition for manufacturing positive electrode of lithium secondary battery, and positive electrode of lithium secondary battery manufactured thereby - Google Patents

Abstract

The present invention relates to a binder composition for producing a positive electrode for a lithium secondary battery, and a positive electrode for a lithium secondary battery produced thereby. The binder composition includes a binder and a gum. The gum is selected from the group consisting of xanthan gum, guar gum, gum arabic, locust bean gum, gellan gum, tara gum, acacia gum, tamarind gum and a combination thereof. The binder composition can improve the storage stability of the composition and the lifespan of a battery.

Description

Binder composition for manufacturing a cathode of a lithium secondary battery, and a cathode of a lithium secondary battery produced thereby, BINDER COMPOSITION FOR MANUFACTURING POSITIVE ELECTRODE OF LITHIUM SECONDARY BATTERY, AND POSITIVE ELECTRODE OF LITHIUM SECONDARY BATTERY MANUFACTURED THEREBY}

The present invention relates to a binder composition for preparing a positive electrode for a lithium secondary battery, and a positive electrode for a lithium secondary battery produced thereby.

Due to the necessity of developing eco-friendly electric vehicles and hybrid vehicles and the rapid development of smart IT devices, the demand for high-capacity high-power batteries is rapidly increasing. Currently, commercially available lithium ion batteries are attracting attention for development of lithium sulfur batteries, lithium selenium batteries, or lithium air batteries having a higher energy density because only limited energy density is used due to technical problems. Among these, sulfur and oxygen, which are positive electrode active materials in lithium sulfur batteries and lithium air batteries, have similar physicochemical properties, and have increased expectations for commercialization due to abundant resource reserves.

Lithium air batteries or lithium sulfur batteries that use lithium metal as a negative electrode and lithium or air as a positive electrode with high reducing power and voltage characteristics and high reversibility, are the reaction products Li ₂ O ₂ , LiOH, and Li ₂ S The amount of lithium ions per weight and volume stored in is much higher than that of LiCoO ₂ used as the anode of lithium ion batteries, and by using lithium metal as the cathode, compared to lithium ion batteries using graphite-based anodes with a maximum Li storage limit of LiC ₆ Since more charge can be stored, the theoretical energy density can be much higher than the lithium ion battery. However, despite the high theoretical energy density, since the actual energy density is as low as 20 to 45% of the theoretical value, lithium-air batteries and lithium-sulfur batteries have not yet been commercialized and are in the early stages of development.

Specifically, in the case of a lithium-air battery, a high overvoltage is required for Li ₂ O ₂ and Li ₂ O generated during charging to decompose into Li ions and O ₂ , and unlike lithium-ion batteries, external air can enter or exit. Due to the open structure, side reactions and electrolyte volatilization are likely to occur due to the inflow of impurities (moisture and carbon dioxide, etc.) from the outside air, and as a result, performance deteriorates rapidly.

In addition, in the case of a lithium-sulfur battery, Li ₂ S, which is the final product of the reaction with sulfur constituting the positive electrode, has an electrically non-conductive property. Accordingly, a lithium-sulfur battery uses an electrolyte having a high dielectric constant of tetraethylenglycol dimethylether (TEGDME), which reduces soluble polysulfide to a lower monomer polysulfide as it moves from the positive electrode to the negative electrode. , This causes a shuttle mechanism to return to the anode and back to the cathode. As a result, these insoluble Li ₂ S and Li ₂ S ₂ can accumulate at the cathode surface and other separation membrane interfaces. In addition, in the positive electrode, lithium polysulfide (Li ₂ S ₈ ), which is a reaction intermediate product, has a high solubility in the organic electrolyte, and is continuously melted during the discharge reaction, thereby reducing the amount of the positive electrode material, thereby causing a rapid decrease in capacity due to cycles. do. In addition, since the electrical conductivity of sulfur itself is very low, it is used in combination with conductive carbon or polymer, but in this case, the energy density of the entire cell is reduced due to a decrease in sulfur content.

In order to solve this problem, various methods such as designing a porous anode structure, developing additives for preventing overvoltage, or forming a surface treatment layer have been researched and developed. From the point of view of positive electrode development, lithium-air batteries dissipate and distribute uniformly without discharging Li ₂ O ₂ inside the dense conductive matrix, maximizing the reaction rate of lithium ions and oxygen during charging with smooth electron transfer. Therefore, a method of reducing the charging overvoltage has been studied. In addition, in the case of a lithium-sulfur battery, through the structural / compositional optimal design, the insulator Li ₂ S is uniformly dispersed and distributed in a dense conductive matrix, thereby facilitating the transfer of electrons and lithium ions and lowering the charge overvoltage. , A method of suppressing the dissolution of lithium polysulfide at the positive electrode has been studied.

Republic of Korea Patent Publication No. 10-2002-0092029

In order to improve the performance of a lithium secondary battery, the present invention can improve the storage stability of the composition and the life characteristics of the battery by using a binder composition in which a gum is added as a thickener to an existing binder for the positive electrode production of a lithium secondary battery. It is intended to provide a binder composition for producing a positive electrode of a lithium secondary battery.

According to a first aspect of the invention,

The present invention provides a binder composition for positive electrode production of a lithium secondary battery comprising a binder and gum.

In one embodiment of the invention, the binder

In one embodiment of the present invention, it is selected from the group consisting of the black xanthan gum, guar gum, gum arabic, locust bean gum, gellan gum, tara gum, acacia gum, tamarind gum and combinations thereof.

In one embodiment of the present invention, the black xanthan gum, guar gum or a combination thereof.

In one embodiment of the present invention, the black guar gum and xanthan gum are mixtures mixed in a weight ratio of 1: 1 to 4: 1.

In one embodiment of the present invention, 1 to 70% by weight based on the black binder is included in the binder composition.

According to the second aspect of the invention,

The present invention provides a positive electrode of a lithium secondary battery formed by applying a positive electrode material including the above-described binder composition, positive electrode active material, and conductive material on a current collector.

In one embodiment of the present invention, the positive electrode material includes 0.01 to 10 parts by weight of a binder composition based on 100 parts by weight of solids in the positive electrode material.

In one embodiment of the present invention, the positive electrode material includes 30 to 95 parts by weight of the positive electrode active material based on 100 parts by weight of solids in the positive electrode material.

In one embodiment of the present invention, the positive electrode material includes 2 to 60 parts by weight of the conductive material based on 100 parts by weight of solids in the positive electrode material.

According to a third aspect of the invention,

The present invention provides a lithium secondary battery comprising the positive electrode described above.

The binder composition according to the present invention can be stored for a long time without layer separation.

In addition, a lithium secondary battery, particularly a lithium sulfur battery, can adsorb polysulfide capable of deteriorating the life of the battery, thereby solving the problem of elution of polysulfide at the positive electrode, thereby improving the life of the battery.

Guar gum and the like, which are additional components of the binder composition, do not contain metal ions, such as sodium, which can degrade the life of the battery with a non-ionic material, and thus the possibility that the life of the battery decreases by adding gum is almost impossible none.

The specific examples provided according to the present invention can all be achieved by the following description. It should be understood that the following description is to describe preferred embodiments of the invention, and it is to be understood that the invention is not necessarily limited thereto.

Binder composition

Conventionally, various kinds of binders have been used to increase the adhesion of a positive electrode active material, a conductive material, or a positive electrode current collector when manufacturing a positive electrode for a lithium secondary battery. However, when only a binder is used without a separate thickener, there is a problem in that long-term storage of the slurry is poor and long-term stability of the prepared electrode is poor. In addition, in the case of a lithium sulfur battery among lithium secondary batteries, a sulfur-based positive electrode active material generated during charging / discharging is eluted in the form of polysulfide, resulting in deterioration of life, and the conventional binder effectively suppresses the elution of the polysulfide. It was difficult to do. Even in the case of metal ions such as Na, long-term life deterioration may occur in the presence of the electrode, which is also difficult to control with a conventional binder. Accordingly, the present invention is to provide a new binder composition that can solve the above-mentioned problems.

The present invention provides a binder composition for preparing a positive electrode of a lithium secondary battery including a binder and gum. The black is a non-volatile and viscous secretion from many plants and trees. The material may be a polysaccharide material, and the polysaccharide material may have a high molecular weight and be hydrophilic or hydrocolloidal. In the present invention, it serves as a black thickener included in the binder composition, and improves the physical properties of the slurry for preparing a positive electrode of a lithium secondary battery and the lifespan characteristics of the battery. In addition, it has the black adsorption property, it is possible to effectively control the polysulfide that can reduce the life of the battery can improve the life of the battery. The black non-ionic material hardly contains impurities such as metal ions such as sodium, which can degrade the life of the battery. The black water-soluble solvent may be uniformly dispersed to be included in the binder composition.

Black xanthan gum, guar gum, gum arabic, locust bean gum, gellan gum, tara gum, acacia gum, tamarind gum, and combinations thereof, which are included in the binder composition according to the present invention, may be selected from, but not limited to, It is not. According to an embodiment of the present invention, it may be the black xanthan gum, guar gum or a combination thereof. The xanthan gum and guar gum have a side chain of a six-carbon structure, and by these side chains, an additional network can be formed between molecules, thereby improving the functionality of the binder composition. In some cases, the black two or more gums may be used in combination, and a combination of guar gum and xanthan gum may be preferable because guar gum and xanthan gum can be more tightly bonded through interaction between functional groups of each other. When combining the guar gum and xanthan gum, it can be used in combination such that the weight ratio of guar gum: xanthan gum is 1: 1 to 4: 1, preferably 2: 1 to 3: 1.

1 to 20% by weight, preferably 2 to 15% by weight, more preferably 3 to 10% by weight based on the black binder may be included in the binder composition.

The binder is a material that is included to maintain the slurry composition forming the positive electrode in the current collector, and is a material that is well soluble in a solvent and can stably form a conductive network with the positive electrode active material composite and a conductive material described above. Any binder known in the art can be used, unless otherwise specified. For example, the binder may include a fluorine resin-based binder comprising polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); Rubber-based binders including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; Cellulose-based binders including carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; Polyalcohol-based binders; Polyolefin-based binders including polyethylene and polypropylene; Polyimide-based binders; Polyester-based binders; And silane-based binder; may be used a mixture or copolymer of one, two or more selected from the group consisting of. According to one embodiment of the present invention, the binder may be preferably a polyolefin-based binder, a polyalcohol-based binder, or a combination thereof.

Anode and lithium secondary battery comprising the same

The present invention provides a positive electrode for a lithium secondary battery prepared by the above-described binder composition. Specifically, the positive electrode for the lithium secondary battery may be a positive electrode in a lithium air battery, a lithium sulfur battery, a lithium selenium battery, a lithium tellurium battery, or a lithium flonium battery, except that it is manufactured using the above-described binder composition. Can be manufactured according to a conventional method for manufacturing a lithium secondary battery positive electrode. Since the binder composition according to the present invention can solve the problem of elution of polysulfide, which is a problem of lithium sulfur batteries, through adsorption of polysulfides, it can be more preferably used in lithium sulfur batteries. Hereinafter, a method of manufacturing a positive electrode for a lithium secondary battery using the above-described binder composition will be described in detail.

The positive electrode according to the present invention is formed by applying a positive electrode material to one or both surfaces of the positive electrode current collector. The positive electrode material includes the above-described binder composition, positive electrode active material, and conductive material.

The binder composition is as described above. The proportion of the binder composition in the positive electrode material may be selected in consideration of the performance of the desired battery. According to an embodiment of the present invention, the positive electrode material comprises 0.01 to 10 parts by weight, preferably 2 to 9 parts by weight, more preferably 4 to 8 parts by weight of a binder composition with respect to 100 parts by weight of solids in the positive electrode material. .

The positive electrode current collector is for supporting the positive electrode active material, and is generally made of a thickness of 3 to 500 μm, and has excellent conductivity and is not particularly limited as long as it is electrochemically stable in the voltage range of the lithium secondary battery. For example, the positive electrode current collector may be any metal selected from the group consisting of copper, aluminum, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof, and the stainless steel is carbon , May be surface-treated with nickel, titanium, or silver, and an aluminum-cadmium alloy may be preferably used as the alloy, and in addition, calcined carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer may be used. have.

The positive electrode current collector can form a fine unevenness on its surface to enhance the bonding force with the positive electrode active material, and various forms such as a film, sheet, foil, mesh, net, porous body, foam, and nonwoven fabric may be used.

The positive electrode active material may be any positive electrode active material available in the art for lithium secondary batteries. Specific examples of the positive electrode active material, lithium metal; Lithium cobalt oxides such as LiCoO ₂ ; Lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; Lithium copper oxide such as Li ₂ CuO ₂ ; Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Lithium nickel-based oxide represented by LiNi _{1 - x} M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); LiMn _{2 - x} MxO ₂ (where M = Co, Ni, Fe, Cr, Zn or Ta, x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, Ni, Cu Or Zn); Li-Ni-manganese-expressed as Li (Ni _a Co _b Mn _c ) O ₂ (where 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1) Cobalt oxide; Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Sulfur or disulfide compounds; Phosphates such as LiFePO ₄ , LiMnPO ₄ , LiCoPO ₄ and LiNiPO ₄ ; Fe ₂ (MoO ₄ ) ₃ and the like, but are not limited to these.

In particular, when the lithium secondary battery is a lithium sulfur battery, the positive electrode active material may include the elemental sulfur (S ₈ ), a sulfur-based compound, or a mixture thereof. Specifically, the sulfur-based compound may be Li ₂ S _n (n≥1), an organic sulfur compound, or a carbon-sulfur polymer ((C ₂ S _x ) _n : x = 2.5-50, n≥2). For the positive electrode active material, a compound (S-PAN) of sulfur (S) -based material and polyacrylonitrile (PAN) may be applied to effectively suppress the dissolution of lithium polysulfide.

The proportion of the positive electrode active material in the positive electrode material may be selected in consideration of the performance of the desired battery. According to one embodiment of the present invention, the positive electrode material contains 30 to 95 parts by weight, preferably 50 to 93 parts by weight, more preferably 70 to 90 parts by weight of the positive electrode active material with respect to 100 parts by weight of solids in the positive electrode material. .

The conductive material is a material that electrically connects the positive electrode active material and the electrolyte to serve as a path for electrons to pass from the current collector to the active material, and can be used without limitation as long as it does not cause a chemical change in a battery composed of porosity and conductivity. . For example, a carbon-based material having porosity may be used, and examples of the carbon-based material include carbon black, graphite fine particles, natural graphite, artificial graphite, graphite, graphene, activated carbon, carbon fiber, metal mesh, and the like. Metallic fibers; Conductive polymers such as polyphenylene derivatives; Metallic powders such as copper, silver, nickel, and aluminum; Or organic conductive materials such as polyphenylene derivatives. The conductive materials may be used alone or in combination.

Currently, commercially available products include acetylene black (such as Chevron Chemical Company or Gulf Oil Company), and Ketjen Black EC series (Armak Company (Armak Company) Company)), Vulcan XC-72 (manufactured by Cabot Company), Super C and Super P (manufactured by MMM).

The proportion of the conductive material in the positive electrode material can be selected in consideration of the performance of the desired battery. According to one embodiment of the present invention, the positive electrode material contains 2 to 60 parts by weight, preferably 3 to 40 parts by weight, more preferably 4 to 20 parts by weight of the conductive material with respect to 100 parts by weight of solids in the positive electrode material. .

The present invention provides a lithium secondary battery comprising the positive electrode described above. In manufacturing the lithium secondary battery, the rest of the configuration except for the positive electrode will be described in detail below.

The negative electrode according to the present invention is formed by applying a negative electrode material to one or both surfaces of the negative electrode current collector. The negative electrode material includes a negative electrode active material and optionally a conductive material and a binder.

If the negative electrode active material can be used as a negative electrode active material of a lithium secondary battery in the art, the type is not particularly limited. The negative active material may include, for example, one or more selected from the group consisting of lithium metal, lithium alloy, transition metal oxide, silicon-based material, and carbon-based material. In addition, the negative electrode active material is, for example, a material capable of reversibly intercalating or deintercalating lithium ions (Li ⁺ ), a material capable of reversibly reacting with lithium ions to form a lithium-containing compound, lithium Metal or lithium alloy.

The lithium alloyable metal is Sn, Al, Ge, Pb, Bi, Sb, Sn-Y1 alloy (Y1 is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or combinations thereof) Element, and not Sn). The elements Y1 include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

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

The silicon-based material may include one or more selected from silicon, a blend of silicon and carbon, a complex of silicon and carbon, and a silicon alloy. In addition, the silicon may include silicon particles, silicon nanowires, silicon nanorods, silicon nanotubes, silicon nanoribbons, or a combination thereof.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be amorphous, plate, flake, spherical or fibrous natural graphite or graphite such as artificial graphite, and the amorphous carbon is soft carbon (soft carbon: low temperature calcined carbon), hard carbon (hard carbon) carbon), mesophase pitch carbide, or calcined coke.

The negative electrode current collector, the conductive material, and the binder are materials commonly used in the related art, and may be used by changing them to suit the negative electrode based on the corresponding configuration in the positive electrode.

The lithium secondary battery according to the present invention includes a separator and an electrolyte together with the positive and negative electrodes described above, and the separator is interposed between the positive and negative electrodes.

The separator is for physically separating both electrodes in the lithium secondary battery of the present invention, and is usually used as a separator in a lithium secondary battery, and can be used without particular limitation. It is preferable that it has excellent moisture permeability.

The separator may be formed of a porous substrate. The porous substrate may be any porous substrate used in electrochemical devices. For example, a polyolefin-based porous membrane or non-woven fabric may be used, but is not particularly limited thereto. .

Examples of the polyolefin-based porous membrane include polyolefin-based polymers such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, polypropylene, polybutylene, and polypentene, respectively, alone or as a mixture of these. One membrane is mentioned.

The nonwoven fabric includes, in addition to the polyolefin nonwoven fabric, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate ), Polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, and polyethylenenaphthalate, respectively. Or the nonwoven fabric formed from the polymer which mixed these is mentioned. The structure of the nonwoven fabric may be a spunbond nonwoven fabric composed of long fibers or a melt blown nonwoven fabric.

The thickness of the porous substrate is not particularly limited, but may be 1 to 100 μm, preferably 5 to 50 μm.

The size and pores of the pores present in the porous substrate are also not particularly limited, but may be 0.001 to 50 μm and 10 to 95%, respectively.

The electrolyte contains lithium ions, and is intended to cause an electrochemical oxidation or reduction reaction at the positive electrode and the negative electrode through this.

The electrolyte may be a non-aqueous electrolyte solution or a solid electrolyte that does not react with lithium metal, but is preferably a non-aqueous electrolyte, and includes an electrolyte salt and an organic solvent.

The electrolyte salt contained in the non-aqueous electrolyte solution is a lithium salt. The lithium salt may be used without limitation as long as it is commonly used in an electrolyte for a lithium secondary battery. For example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , LiFSI, LiTFSI, CH ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, LiN (SO ₂ F) ₂ , lithium chloroborane, lower aliphatic lithium carboxylate, lithium 4-phenyl borate, lithium imide, and the like can be used.

As the organic solvent included in the non-aqueous electrolyte, those commonly used in the electrolyte for lithium secondary batteries can be used without limitation. According to one embodiment of the present invention, the organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent. Among them, an ether-based solvent can be typically used.

Specifically, the carbonate-based solvent is dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene Carbonate (EC), propylene carbonate (PC), or butylene carbonate (BC), and the like can be used.

Specifically, the ester-based solvent is methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethylethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, Valerolactone, mevalonolactone, carprolactone, and the like can be used.

Specifically, the ether-based solvent is dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, ethylpropyl ether, dimethoxyethane, diethoxyethane, methoxyethoxyethane, diethylene glycol dimethyl ether , Diethylene glycol diethyl ether, diethylene glycol methylethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methylethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene Glycol methylethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol methylethyl ether, diglyme, triglyme, tetraglyme, tetrahydrofuran, 2-methyltetrahydrofuran, or polyethylene glycol dimethyl ether It includes Le can be used.

Specifically, cyclohexanone may be used as the ketone-based solvent. As the alcohol-based solvent, specifically, ethyl alcohol, isopropyl alcohol, or the like can be used.

As the aprotic solvent, specifically, nitriles such as acetonitrile, amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane (DOL), or sulfolane may be used.

The non-aqueous organic solvent may be used alone or in combination of one or more, and the mixing ratio when used in combination with one or more may be appropriately adjusted according to the desired battery performance.

The electrolyte may further include LiNO ₃ . When the electrolyte solution includes the LiNO ₃ , it is possible to improve the shuttle suppressing effect. The electrolyte may include LiNO ₃ in an amount of 1 to 50% by weight based on the total weight of the electrolyte.

The electrolyte may include one or more selected from the group consisting of a liquid electrolyte, a gel polymer electrolyte, and a solid polymer electrolyte. Preferably it may be a liquid electrolyte.

The injection of the non-aqueous electrolyte may be performed at an appropriate step in the manufacturing process of the electrochemical device, depending on the manufacturing process of the final product and the required properties. That is, it can be applied before the electrochemical device assembly or at the final stage of the electrochemical device assembly.

The lithium secondary battery according to the present invention can perform lamination, stack, and folding processes of a separator and an electrode in addition to the general process of winding.

The shape of the secondary battery is not particularly limited and may be various shapes such as a cylindrical shape, a stacked shape, and a coin shape.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are provided only to more easily understand the present invention and the present invention is not limited thereto.

Example

Example  One

1. Preparation of anode

A binder composition was prepared by mixing polyalcohol with a mixture of guar gum (manufactured by Sigma-Aldrich) and xanthan gum (manufactured by Sigma-Aldrich) in a weight ratio of 3: 1. The mixture in the binder composition contained 30% by weight based on polyalcohol. In addition, sulfur (manufactured by Sigma-Aldrich) was mixed with CNT (Carbon Nanotube) using a ball mill, and then heat-treated at 155 ° C to prepare a positive electrode active material of a sulfur-carbon composite. Super P was prepared as a conductive material. The above-described positive electrode active material, conductive material and binder were added to water as a solvent and mixed with a mixer to prepare a composition for forming a positive electrode active layer. At this time, the mixing ratio was such that the positive electrode active material: conductive material: binder composition was 90: 5: 5 by weight ratio. The prepared positive electrode active material layer-forming composition was applied to an aluminum foil current collector and then dried at 50 ° C. for 2 hours to prepare a positive electrode (energy density of the positive electrode: 5.5 mAh / cm 2).

2. Manufacturing of lithium secondary battery

A lithium secondary battery was assembled by preparing a negative electrode, a separator, and an electrolyte as described below, together with the positive electrode prepared by the above-described method.

(1) Cathode

Lithium foil was used as the negative electrode.

(2) separator

A polyethylene membrane was used as the separator.

(3) Electrolytic solution

As an electrolyte, LiTFSI was mixed in a mixed solvent of dioxolane (DOL) and dimethyl ether (DME) at a concentration of 0.1 mol, and an electrolyte in which LiNO ₃ was added at 1% by weight compared to the electrolyte was used.

Example  2

When preparing the positive electrode, a positive electrode and a lithium secondary battery were prepared in the same manner as in Example 1, except that a polyalcohol was mixed with guar gum (30% by weight compared to polyalcohol) instead of a mixture of guar gum and xanthan gum to prepare a binder composition. Was prepared.

Example  3

In the preparation of the positive electrode, a positive electrode and a lithium secondary battery were prepared in the same manner as in Example 1, except that a polyalcohol was mixed with xanthan gum (30% by weight compared to polyalcohol) instead of a mixture of guar gum and xanthan gum to prepare a binder composition. Was prepared.

Comparative example  One

Example 1, except that a binder composition was prepared by mixing styrene-butadiene rubber (SBR, manufactured by Sigma-aldrich) with carboxymethyl cellulose (CMC, manufactured by Daicel) in a weight ratio of 7: 3 when preparing the positive electrode. A positive electrode and a lithium secondary battery were manufactured in the same manner as.

Experimental example

Experimental example  One

After preparing the binder composition according to Examples and Comparative Examples, the initial viscosity and the viscosity and sedimentation after storage for 10 days were measured and are shown in Table 1 below. For the viscosity, a Brookfield viscometer was used, and whether or not sedimentation occurred was visually confirmed.

Example 1 Example 2 Example 3 Comparative Example 1 Initial viscosity (cP) 25,000 17,000 13,000 6,500 Viscosity after storage for 10 days (cP) 35,000 20,000 20,000 7,200 Sedimentation × × × ○

According to Table 1, it was confirmed that the binder compositions according to Examples 1 to 3 were maintained at a high viscosity without sedimentation.

All simple modifications and variations of the present invention belong to the scope of the present invention, and the specific protection scope of the present invention will become apparent by the appended claims.

Claims (11)

A binder composition for preparing a positive electrode of a lithium secondary battery including a binder and gum. The method according to claim 1,
The binder is a binder composition for positive electrode production of a lithium secondary battery, characterized in that a polyolefin-based binder, a polyalcohol-based binder, or a combination thereof. The method according to claim 1,
The black xanthan gum, guar gum, gum arabic, locust bean gum, gellan gum, tara gum, acacia gum, tamarind gum and a binder composition for positive electrode production of a lithium secondary battery, characterized in that selected from the group consisting of a combination thereof. The method according to claim 3,
The black xanthan gum, guar gum or a binder composition for producing a positive electrode of a lithium secondary battery, characterized in that a combination thereof. The method according to claim 4,
The black guar gum and xanthan gum is a binder composition for producing a positive electrode of a lithium secondary battery, characterized in that a mixture in a weight ratio of 1: 1 to 4: 1. The method according to claim 1,
A binder composition for positive electrode production of a lithium secondary battery, characterized in that 1 to 70% by weight based on the black binder is included in the binder composition. A positive electrode of a lithium secondary battery formed by applying a positive electrode material comprising a binder composition according to claim 1, a positive electrode active material and a conductive material on a current collector. The method according to claim 7,
The positive electrode material is a positive electrode of a lithium secondary battery, characterized in that it comprises a binder composition of 0.01 to 10 parts by weight based on 100 parts by weight of solids in the positive electrode material. The method according to claim 7,
The positive electrode material is a positive electrode of a lithium secondary battery, characterized in that it contains a positive electrode active material 30 to 95 parts by weight based on 100 parts by weight of solids in the positive electrode material. The method according to claim 7,
The positive electrode material is a positive electrode of a lithium secondary battery, characterized in that it comprises a conductive material of 2 to 60 parts by weight based on 100 parts by weight of solids in the positive electrode material. Lithium secondary battery comprising the positive electrode according to claim 7.