KR101108446B1 - Conductive Agent for Surface Treatment for Hydrophobic Property and Secondary Battery Containing the Same - Google Patents

Abstract

The present invention is a conductive material used to improve the conductivity of an electrode active material, and provides a conductive material comprising hydrophobic surface treatment on the surface of the conductive material so as to exhibit high water repellency.

Since the conductive material can secure a predetermined conductivity while reducing the amount of water penetrated into the battery, the secondary battery including the same has excellent performance and lifespan characteristics.

Description

Conductive Agent for Surface Treatment with Hydrophobicity and Secondary Battery Containing the Same {Conductive Agent for Surface Treatment for Hydrophobic Property and Secondary Battery Containing the Same}

The present invention relates to a hydrophobic surface-treated conductive material, and more particularly, to a conductive material used to improve the conductivity of an electrode active material, wherein the surface of the conductive material is subjected to hydrophobic surface treatment to exhibit high water repellency. It relates to a conductive material configured and a secondary battery comprising the same.

As the technology development and demand for mobile devices increase, the demand for secondary batteries capable of charging and discharging as energy sources is rapidly increasing. Accordingly, many researches on secondary batteries capable of meeting various needs have been conducted. Representative examples of such secondary batteries include lithium secondary batteries.

The lithium secondary battery has a structure in which a non-aqueous electrolyte containing lithium salt is impregnated in an electrode assembly having a porous separator interposed between a positive electrode and a negative electrode on which an active material is coated on a current collector. Lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium composite oxide, and the like are mainly used as the cathode active material, and carbonaceous materials are mainly used as the cathode oxide.

Such a lithium secondary battery, for example, when the water content in the battery increases, it causes the decomposition of the electrolyte to generate an acid, the acid generated thereby promotes side reactions such as decomposition of the negative electrode SEI and dissolution of the positive electrode active material Ultimately, problems such as a decrease in battery capacity and an increase in internal resistance are caused. That is, since the performance of the lithium secondary battery is greatly affected by the moisture content in the battery, it is important to prevent the penetration of moisture in the battery manufacturing process.

Accordingly, the present invention provides a technique for minimizing the adsorption and inflow of water in the manufacturing process of the battery by hydrophobic treatment of the surface of the conductive material to exhibit the overall hydrophobicity of the components of the battery.

To date, there is no technique for performing hydrophobic treatment on the surface of the conductive material, and only some techniques for performing hydrophobic treatment on the surface of the negative electrode active material or the negative electrode mixture. For example, Japanese Patent Application Laid-Open No. 2002-015728 discloses a technique of hydrophobic treatment on the surface of a negative electrode active material, which is lithium metal included in an electrode mixture, to prevent dendrite growth at the negative electrode and to improve cycle characteristics of the battery. Doing. However, since the spinel crystal structure, which is a passage through which ions move, may be partially closed by performing a hydrophobic surface treatment on the lithium metal anode active material, the above technique may adversely affect battery characteristics due to the poor rate characteristics of ions. there is a problem.

In addition, Korean Patent Application Publication No. 195-0002099 discloses a technique of forming a hydrophobic layer on the surface of a negative electrode to prevent decomposition of an electrolyte and suppressing the internal pressure of a battery due to gas generation to improve high rate charging characteristics. However, this technique has a problem because it is not possible to prevent the moisture that can be sucked into the mixture during the preparation of the negative electrode mixture in the slurry state and the resulting side reactions.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application, after continuing in-depth research and various experiments, can exhibit high water repellency when the surface of the conductive material is subjected to hydrophobic surface treatment, thereby effectively inhibiting water adsorption and inflow into the electrode mixture, thereby effectively preventing the inside of the battery. Since it was possible to prevent side reactions caused by moisture and at the same time to secure a predetermined conductivity, it was confirmed that the high temperature storage characteristics of the battery could be improved, and thus the invention was completed.

Accordingly, the secondary battery conductive material according to the present invention is a conductive material used to improve the conductivity of an electrode active material, and is composed of hydrophobic surface treatment on the surface of the conductive material so as to exhibit high water repellency.

The lithium secondary battery is manufactured by mounting an electrode assembly including a cathode, an anode, and a separator interposed therebetween inside a battery case, injecting a non-aqueous electrolyte, and then sealing the case. Such lithium secondary batteries have a problem in that side reactions are caused by moisture penetrating into the electrode mixture or the electrolyte during the manufacturing of the electrode, and thus performance is degraded when stored at high temperature for a long time.

Therefore, in the present invention, by performing a hydrophobic surface treatment on the surface of the conductive material added to the electrode mixture in order to exhibit high water repellency, the adsorption or inflow of moisture into the battery during the manufacturing process of the electrode, or at least inhibited By preventing side reactions caused by moisture inside the battery, high temperature storage characteristics can be improved. Specifically, by performing a hydrophobic surface treatment, it is possible to prevent the decomposition of the electrolyte due to the action of moisture in the battery, thereby preventing the generation of acid and decomposition of the negative electrode SEI film, and the phenomenon that the positive electrode active material is dissolved. It can be minimized.

The hydrophobic surface treatment can be achieved, for example, by coating a hydrophobic material on the surface of the conductive material particles, and the coating method is not particularly limited, and may be selected from known methods or carried out by a new suitable method. For example, a hydrophobic material may be coated on the surface of the conductive material by chemical vapor deposition (CVD) or physical vapor deposition (PVD), and the chemical vapor deposition method may be a fluidized bed chemical vapor deposition method or a rotating three-dimensional image. Chemical vapor deposition, vibration chemical vapor deposition, and the like can be used, and physical vapor deposition can be used, such as sputtering, vacuum annual method, plasma coating method.

As the hydrophobic material, a substance such as an aromatic compound or a chlorine-containing solvent may be used. However, the hydrophobic material is preferably a silane compound and / or a siloxane compound which simultaneously exhibits improved adhesion and hydrophobic effect.

Examples of such silane compounds include vinyl silane compounds such as vinyl trichlorosilane, vinyl tris (2-methoxyethoxy) silane, vinyltriethoxysilane, and vinyltrimethoxysilane; (Meth) acrylic silane compounds such as 3-methacryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; Epoxy silane compounds such as 2- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, and 3-glycidyloxypropylmethyldiethoxysilane; N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3 Amino silane compounds such as -aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane; Alkoxy silane compounds, such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane; And 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and the like, but may be one or two or more selected from the group consisting of, but are not limited thereto.

In addition, examples of the siloxane compound may be selected from the group consisting of polymethylsiloxane, polydimethylsiloxane, polymethylvinylsiloxane, polymethylphenylsiloxane, oxyethylene-modified siloxane, polymethylhydrogensiloxane, octamethylcyclotetrasiloxane, and the like. It may be one or more than two.

In one preferred embodiment, the silane compound and / or siloxane compound is HMDS (hexamethyldisilazane), TMSCL (trimethyl chlorosilane), silicone oil (silicone oil), amino silane (amino silane), alkyl silane (alkyl silane), One or two or more selected from the group consisting of PDMS (polydimethyl siloxane) and DDS (dimethyl dichlorosilane) may be used. Since the hydrophobic material is composed of substituents having very low chemical reactivity, it does not cause side reactions in the electrochemical reaction system including a polar solvent, thereby preventing degradation of the battery and reducing capacity, and exhibiting excellent water repellency. It can greatly improve performance.

In some cases, hydrophobic functional groups may be generated on the surface of the conductive material particles by the hydrophobic surface treatment. Specifically, as a result of treating the surface of the conductive material by chemical, electrochemical or physical methods, hydrophobic functional groups are generated on the surface of the conductive material particles, and the conductive material itself may exhibit high hydrophobicity.

According to the experimental results performed by the inventors of the present application, when the hydrophobic material exceeds the predetermined amount of the electrode mixture, it acts as an electrical resistance rather than exerting the effect of inhibiting moisture penetration, thereby adversely affecting the speed characteristics of the battery. Confirmed. Therefore, in order to improve the high temperature storage characteristics due to moisture resistance when maintaining the speed characteristic of the battery, the hydrophobic material may preferably be added in an amount of 0.001 to 5% by weight based on the weight of the conductive material.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. Specific examples of commercially available conductive materials include Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, Ketjenblack, and EC, which are acetylene black series. (Armak Company), Vulcan XC-72 (Cabot Company) and Super P (Timcal) may also be KS-6 (Timcal), etc. It is not limited only to these.

In one preferred example, the conductive material may be carbon black. The carbon black is a fine powder of carbon obtained by incomplete combustion or pyrolysis of natural gas, petroleum, etc., and is widely used as a conductive material included in electrode mixtures because of its excellent conductivity, wide surface area, and chemical stability. . However, since it has highly reactive functional groups, such as a phenol group, a carbonyl group, a carboxyl group, a quinone group, and a lactone group, on the surface, it tends to exhibit the property to react with water. Therefore, the amount of water in the battery can be reduced by performing hydrophobic surface treatment on the surface of such carbon black to lower the reactivity with water.

The particle size of the carbon black is preferably a particle size of 100 nm or less as primary particles, so that the hydrophobic surface treatment can be easily performed while securing a predetermined conductivity.

The present invention also provides an electrode mixture comprising an electrode active material and a hydrophobic surface-treated conductive material as described above.

The electrode active material is a material for storing energy in the electrode mixture is divided into a positive electrode active material and a negative electrode active material.

The cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Li _{1 + x} Mn _{2 - x} O ₄ (Where x is 0 to 0.33), lithium manganese oxides such as LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3; Formula LiMn _2-x M _x O ₂ (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The negative electrode active material is, for example, carbon-based, such as non-graphitized carbon, graphite carbon; Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _{1 - x} Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, 3 of the periodic table) Metal composite oxides such as a group element, halogen, 0 <x ≦ 1, 1 ≦ y ≦ 3, 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , and metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used, and crystalline carbon, amorphous carbon, silicon-based active materials, tin-based active materials, silicon-carbon-based active materials and the like can also be used.

The conductive material serves to impart electrical conductivity in the electrode mixture, and may be added within 20% based on the total weight of the electrode mixture, and may preferably be included in 0.5 to 10%.

The present invention also provides a secondary battery comprising the electrode mixture, preferably a lithium secondary battery. The lithium secondary battery has a structure in which a lithium salt-containing non-aqueous electrolyte is impregnated into an electrode assembly having a separator interposed between a positive electrode and a negative electrode.

The positive electrode and the negative electrode are manufactured by coating, drying, and compressing the electrode mixture on a current collector, and if necessary, components such as a binder and a filler may be further included in addition to the components described above with respect to the composition of the electrode mixture. In addition, the positive electrode, the negative electrode, the electrolyte and the like can be used as is known in the art, such components are described in detail below.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver or the like can be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The binder is a component that assists in bonding the active material and the conductive material to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The separator is an insulating thin film interposed between the anode and the cathode and having high ion permeability and mechanical strength. The pore diameter of the separator is generally from 0.01 to 10 ㎛ ㎛, thickness is generally 5 ~ 300 ㎛. As such a separation membrane, for example, a sheet or a nonwoven fabric made of an olefin-based polymer such as polypropylene which is chemically resistant and hydrophobic, glass fiber, polyethylene or the like is used.

In some cases, a gel polymer electrolyte may be coated on the separator to increase battery stability. Representative of such gel polymers are polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile and the like. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

The lithium salt-containing non-aqueous electrolyte is composed of an organic solvent electrolyte and a lithium salt.

As said electrolyte solution, N-methyl- 2-pyrrolidinone, a propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, Gamma-butylo lactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolon, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolon, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxolon Aprotic organic solvents such as derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyroionate and ethyl propionate can be used. Can be.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, 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,} CH 3 SO 3 Li, CF 3 SO 3 Li, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 4-phenylborate, imide, and the like can be used.

In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, etc. Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, etc. It may be. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are provided to illustrate the present invention, and the scope of the present invention is not limited thereto.

[Production Example 1]

Super-P, a conductive material, was reacted with HMDS at 150 ° C to form a silane group in a functional group present on the surface of the conductive material, and washed with hexane to surface-treat the hydrophobic material on the conductive material.

Example 1

1-1. Manufacture of anode

95% by weight of LiCoO ₂ as a positive electrode active material, 2.5% by weight of Super-P surface-treated in Preparation Example 1, and 2.5% by weight of PVdF (binder) were added to NMP (N-methyl-2-pyrrolidone) as a solvent to mix the positive electrode. After preparing the slurry, a positive electrode was prepared by coating, drying and pressing on a long sheet aluminum foil.

1-2. Preparation of Cathode

95% by weight of artificial graphite as a negative electrode active material, 2.5% by weight of Super-P (conductive material) and 2.5% by weight of PVdF (binder), which were surface treated in Preparation Example 1, were added to NMP as a solvent to prepare a negative electrode mixture slurry. A negative electrode was prepared by coating, drying and pressing on a long sheet copper foil.

1-3. Manufacture of batteries

A lithium secondary battery was manufactured by injecting a 1M LiPF ₆ EC / EMC electrolyte solution with a separator (Celgard 2400 manufactured by Hoechst Celanese) interposed between the cathodes and cathodes of 1-1 and 1-2.

[Example 2]

A lithium secondary battery was manufactured in the same manner as in Example 1, except that a conductive material, which was not hydrophobically treated, was used for the cathode.

Example 3

A lithium secondary battery was manufactured in the same manner as in Example 1, except that a conductive material, which was not hydrophobically treated, was used for the negative electrode.

Example 4

A lithium secondary battery was manufactured in the same manner as in Example 1, except that a conductive material surface-treated with 1 wt% HMDS based on the weight of the conductive material was used.

Example 5

A lithium secondary battery was manufactured in the same manner as in Example 1, except that a conductive material surface-treated with 5 wt% HMDS based on the weight of the conductive material was used.

Comparative Example 1

A lithium secondary battery was manufactured in the same manner as in Example 1, except that a conductive material that was not hydrophobically surface treated for both the positive electrode and the negative electrode was used.

Comparative Example 2

A lithium secondary battery was manufactured in the same manner as in Example 1, except that a conductive material surface-treated with 7 wt% HMDS based on the weight of the conductive material was used.

Comparative Example 3

A lithium secondary battery was manufactured in the same manner as in Example 1, except that a conductive material surface-treated with 10 wt% HMDS based on the weight of the conductive material was used.

[Experimental Example]

One. Moisture Content Measurement Experiment

The moisture content of the electrodes prepared in Examples 1 to 5 and Comparative Examples 1 to 3, respectively, was measured and shown in Table 1 below.

2. High Temperature Storage Characteristics Evaluation Experiment

The batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 3, respectively, were stored at 60 ° C. for 2 weeks in a fully charged state, and then the capacity thereof was measured as shown in Table 1 below as a ratio to the initial capacity.

3. Speed characteristic evaluation experiment

After charging the batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 3 to 4.2 V, the capacity at the time of discharging at a current of 0.5 C and a current of 5 C, respectively, was measured and is shown in Table 1 as a ratio. It was.

TABLE 1

As shown in Table 1, the batteries of the embodiment according to the present invention, the water content of the positive electrode and the negative electrode is greatly reduced, the ratio of capacity to initial capacity after storage at high temperature is at least 80% or more very high, high current The capacity ratio of low current to power was very high, at least 87%. That is, by adding a hydrophobic surface-treated conductive material to the positive electrode mixture and / or negative electrode mixture, it can be confirmed that the capacity characteristics are improved by suppressing side reactions inside the battery due to moisture during high temperature storage. On the other hand, in the battery of Comparative Example 1, the moisture content of the positive electrode and the negative electrode is very high, it can be seen that the capacity is significantly reduced compared to the initial capacity after high temperature storage.

Also, as in the batteries of Comparative Examples 2 and 3, when the content of the hydrophobic particles exceeds the range of 5% by weight, the capacity ratio of the high temperature storage no longer increases, but rather the capacity ratio of the low current to the high current is increased. It can be seen that the decrease. In other words, the excess content of hydrophobic particles acts as a resistance in the interior of the electrode, hindering the flow of electricity. Therefore, it is preferable to add hydrophobic particles to the positive electrode or the negative electrode as in Examples 2 and 3, or to adjust the content of the hydrophobic particles within the range according to Examples 1, 4, and 5.

As described above, the conductive material according to the present invention is hydrophobic surface treatment is performed so as to exhibit a high water repellency on the surface by securing a predetermined conductivity while reducing the amount of moisture penetrated therein during the manufacturing process of the battery, It can improve the performance and life characteristics of the secondary battery.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (11)

A lithium secondary battery having a structure in which a lithium salt-containing non-aqueous electrolyte is impregnated into an electrode assembly having a separator interposed between a positive electrode and a negative electrode, At least one electrode of the positive electrode or the negative electrode includes a conductive material used to improve the conductivity of the electrode active material, and the surface of the conductive material is subjected to hydrophobic surface treatment to exhibit water repellency, the hydrophobic surface treatment is a hydrophobic material It is achieved by coating the surface of the conductive material particles, the hydrophobic material is a lithium secondary battery, characterized in that the silane compound and / or siloxane compound. delete delete According to claim 1, wherein the hydrophobic material is hexamethyldisilazane (HMDS), trimethyl chlorosilane (TMSCL), silicone oil (silicone oil), amino silane (amino silane), alkyl silane (alkyl silane), polydimethyl siloxane (PDMS), and DDS Lithium secondary battery, characterized in that one or two or more selected from the group consisting of (dimethyl dichlorosilane). The lithium secondary battery of claim 1, wherein the hydrophobic material is added in an amount of 0.001 to 5 wt% based on the weight of the conductive material. The lithium secondary battery according to claim 1, wherein a hydrophobic functional group is formed on the surface of the conductive material particles by the hydrophobic surface treatment. The lithium secondary battery of claim 1, wherein the conductive material is carbon black. The lithium secondary battery according to claim 7, wherein the carbon black has a particle diameter of more than 0 nm and less than or equal to 100 nm. delete delete delete