KR20150034151A - Rechargeable lithium battery controlled particle size ratio of positive electrode active material and active carbon - Google Patents

Abstract

The present invention relates to a lithium secondary battery wherein the lithium secondary battery contains a negative electrode comprising a negative electrode active material, and a positive electrode comprising a cathode active material and an activated carbon, wherein the negative electrode active material during X-ray diffraction measurement using a CuKαα, the inter-layer distance (interlayer spacing, d_002) of (002) surface includes a carbon-based material of 0.34 nm to 0.50 nm, and the positive electrode active material contains a lithium iron phosphate compound, and wherein the average particle diameter of the activated carbon is not less than 1000% and not more than 3000% with respect to the average particle size of 100% of the positive electrode active material.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lithium secondary battery having a controlled particle size ratio between a positive electrode active material and an activated carbon (RECHARGEABLE LITHIUM BATTERY CONTROLLED PARTICLE SIZE RATIO OF POSITIVE ELECTRODE ACTIVE MATERIAL AND ACTIVE CARBON)

To a lithium secondary battery in which the particle size ratio of the cathode active material and the activated carbon is controlled.

2. Description of the Related Art Recently, with the realization of miniaturization and weight reduction of electronic equipment and generalization of use of portable electronic devices, researches on lithium secondary batteries having high energy density as a power source of portable electronic devices have been actively conducted.

The lithium secondary battery is composed of a negative electrode, a positive electrode and an electrolyte, and generates electrical energy by oxidation and reduction reactions when lithium ions are intercalated / deintercalated in the positive and negative electrodes.

As an anode active material of such a lithium secondary battery, lithium metal, carbon-based material, Si and the like are used.

As a cathode active material of the lithium secondary battery, a chalcogenide compound of a metal capable of intercalating and deintercalating lithium ions is used. Examples of the chalcogenide compound include LiCoO _2, LiMn ₂ O ₄ , LiNiO ₂ , LiNi _{1 x} Co _x O ₂ (0 < X < 1), LiMnO _2, or the like.

Recently, attempts have been made to obtain a low resistance by thinning an electrode to obtain a high output characteristic of a lithium secondary battery, but the satisfactory level has not been reached due to the characteristics of the active material itself. Thus, techniques for using activated carbon, which is a capacitor material, with an active material have been developed.

And a lithium secondary battery improved in high-rate characteristics and life characteristics.

In one embodiment of the present invention, a lithium secondary battery comprising a negative electrode comprising a negative electrode active material, and a positive electrode comprising a positive electrode active material and an activated carbon, wherein the negative electrode active material is a lithium secondary battery, And a carbonaceous material having a distance (d ₀₀₂ ) of 0.34 nm to 0.50 nm, wherein the cathode active material comprises lithium iron phosphate-based compounds, and the average particle diameter of the activated carbon is about 100% of the average particle diameter of the cathode active material To provide a lithium secondary battery having 1000% or more and 3000% or less

The average particle size of the activated carbon may be 1000% or more and 2500% or less with respect to 100% of the average particle size of the cathode active material.

The cathode active material may be an olivine structure.

The average particle diameter of the cathode active material may be 0.1 탆 to 20 탆.

The average particle size of the activated carbon may be 1 to 30 mu m.

The content of the activated carbon may be 1 to 40% by weight based on the total amount of the cathode active material and the activated carbon.

In the cathode, the carbon-based material having the interlayer distance of the (002) plane of 0.34 nm to 0.50 nm may be amorphous carbon.

The carbon-based material may be, for example, soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or a combination thereof.

The average particle diameter of the carbon-based material may be 1 탆 to 50 탆.

The cathode active material may be a structure of secondary particles in which primary particles are aggregated.

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

The lithium secondary battery according to one embodiment is excellent in high rate charge / discharge characteristics and life characteristics.

1 is a schematic view illustrating a structure of a lithium secondary battery according to an embodiment of the present invention.

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

In one embodiment of the present invention, there is provided a lithium secondary battery including a negative electrode including a negative electrode active material, and a positive electrode comprising a positive electrode active material and an activated carbon, wherein the lithium secondary battery, in which the particle size ratio of the positive electrode active material and the activated carbon is controlled according to the type of the positive electrode active material, Lt; / RTI &gt;

Specifically, the cathode active material is a lithium nickel oxide, a lithium cobalt oxide, a lithium manganese oxide, a lithium titanium oxide, a lithium nickel manganese oxide, a lithium nickel cobalt manganese oxide, a lithium nickel cobalt aluminum oxide, Wherein the average particle size of the activated carbon is more than 100% and less than 1000% with respect to 100% of the average particle size of the cathode active material.

Alternatively, the cathode active material includes a lithium iron phosphate-based compound, wherein the average particle size of the activated carbon is 1000% or more and 3000% or less with respect to 100% of the average particle diameter of the cathode active material.

Such lithium secondary batteries are excellent in high rate charge / discharge characteristics and life characteristics.

The lithium secondary battery will be described with reference to FIG. 1 is a schematic view showing a lithium secondary battery according to one embodiment.

1, a lithium secondary battery 100 according to an embodiment includes an electrode assembly 40 wound between a positive electrode 10 and a negative electrode 20 with a separator 30 interposed therebetween, And a case 50 having a built- The anode 10, the cathode 20 and the separator 30 may be impregnated with an electrolyte solution (not shown).

First, the anode 10 will be described.

The anode 10 includes a current collector and a cathode active material layer formed on the current collector, and the cathode active material layer includes a cathode active material and activated carbon.

The positive electrode active material includes lithium nickel based oxide, lithium cobalt based oxide, lithium manganese based oxide, lithium titanium based oxide, lithium nickel manganese based oxide, lithium nickel cobalt manganese based oxide, lithium nickel cobalt aluminum based oxide, In this case, the average particle diameter of the activated carbon may be more than 100% and less than 1000% with respect to 100% of the average particle diameter of the cathode active material. Specifically, it may be more than 100% and less than 900%, more than 100%, less than 800%, more than 100%, less than 700%, less than 100%, less than 600%, more than 100%

In this case, the cathode active material and the activated carbon are uniformly dispersed, and the active carbon is evenly distributed between the active material and the active material, so that a uniform electrode can be formed. Further, as uniform electrodes are formed, deterioration of a part of the electrodes due to repeated charging / discharging and high-rate input / output can be suppressed, and cycle life characteristics can be improved. If the activated carbon having the same or smaller particle diameter than the cathode active material is used, the contact area between the activated carbon and the cathode active material may be increased, but the effect of using the activated carbon is decreased. Particularly, High rate charging / discharging efficiency and cycle life characteristics are deteriorated.

In addition, the lithium secondary battery can further enhance the effect of using activated carbon, that is, the effect of physically adsorbing lithium ions and rapidly transferring the adsorbed lithium ions to the cathode active material. Especially, the effect of using activated carbon at high rate charging / discharging is further increased, so that the high rate charging / discharging efficiency and cycle life characteristics of the lithium secondary battery can be greatly improved.

The cathode active material may be a structure of secondary particles in which primary particles are aggregated, and the size of the secondary particles may be 1 to 20 탆. Specifically 1 to 18 占 퐉, 1 to 16 占 퐉, 1 to 14 占 퐉, 1 to 12 占 퐉, 1 to 10 占 퐉.

This means that, in one embodiment, the particle size of the cathode active material is 1 to 20 탆, and the average particle diameter of the activated carbon with respect to the average particle diameter of the cathode active material is more than 100% but less than 1000%.

The activated carbon is a carbon material having a large specific surface area and a strong adsorption property, physically adsorbing lithium ions and rapidly transferring the adsorbed lithium ions to the cathode active material.

The average particle size of the activated carbon may be 1 to 30 mu m. Specifically 1 to 28 탆, 1 to 26 탆, 1 to 24 탆, 1 to 22 탆, 1 to 20 탆, 1 to 18 탆, 1 to 16 탆, 1 to 14 탆, 1 to 12 탆, But it is not limited thereto. In this case, the cathode active material and the activated carbon are uniformly dispersed and the performance of the activated carbon can be maximized, thereby improving the high rate charge / discharge characteristics and lifetime characteristics of the lithium secondary battery.

The content of the activated carbon may be 1 to 40% by weight based on the total amount of the cathode active material and the activated carbon. Specifically, it may be 1 to 35% by weight, 1 to 30% by weight, 1 to 25% by weight, 1 to 20% by weight, 1 to 15% by weight and 1 to 10% by weight. In this case, the high rate charge / discharge characteristics and life characteristics of the lithium secondary battery can be improved.

As described above, in another embodiment of the present invention, the cathode active material includes a lithium iron phosphate-based compound, wherein the average particle size of the activated carbon is 1000% or more and 3000% or less with respect to 100% of the average particle diameter of the cathode active material. Lt; / RTI &gt;

The ratio of the average particle size of the activated carbon to the average particle size of the cathode active material is specifically 1000% or more and 2800% or less, 1000% or more and 2600% or less, 1000% or more and 2500% % &Lt; / RTI &gt;

In this case, the cathode active material and the activated carbon are uniformly dispersed, and the performance of the activated carbon is maximized, so that the high rate charge / discharge characteristics and life characteristics of the lithium secondary battery can be remarkably improved.

The positive electrode active material refers to an active material having an olivine structure. That is, in one embodiment, the cathode active material has an olivine structure, wherein the average particle size of the activated carbon with respect to the average particle diameter of the cathode active material is 1000% or more and 3000% or less.

The average particle diameter of the cathode active material or the olivine cathode active material including the lithium iron phosphate-based compound may be 0.1 탆 to 20 탆. Specifically, it may be 0.1 탆 to 15 탆, 0.1 탆 to 10 탆, 0.1 탆 to 9 탆, 0.1 탆 to 8 탆, and 0.1 탆 to 7 탆. The cathode active material may be a structure of secondary particles in which primary particles are aggregated, and the size of the secondary particles may be 0.1 to 20 탆.

That is, in one embodiment, when the particle size of the cathode active material is 0.1 탆 to 20 탆, the particle size of the activated carbon with respect to the particle size of the cathode active material is 1000% or more and 3000% or less. Such a lithium secondary battery is excellent in high rate charge / discharge characteristics and life characteristics.

The description of the activated carbon is as described above.

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

The cathode active material layer may further include a binder. The binder serves to adhere the positive electrode active materials to each other and to adhere the positive electrode active material to the current collector.

Examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymer containing ethylene oxide, polyvinyl pyrrolidone But are not limited to, polyurethane, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin and nylon.

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

The negative electrode will be described below.

The cathode 20 includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material.

The negative active material includes a carbon-based material having an interlayer spacing (d ₀₀₂ ) of (002) plane of 0.34 nm to 0.50 nm in X-ray diffraction measurement using CuKαα. In this case, insertion and desorption of lithium ions can be easily performed, and excellent high rate charge / discharge characteristics can be realized.

The interlayer distance (d ₀₀₂ ) of the carbon-based material may be specifically 0.34 nm to 0.45 nm, 0.34 nm to 0.40 nm, 0.34 nm to 0.37 nm, and 0.34 nm to 0.36 nm. When the inter-layer distance satisfies the above range, insertion and disconnection of lithium ions can be easily performed, thereby realizing excellent high rate charge / discharge characteristics.

The carbon-based material may be amorphous carbon. Unlike graphite, which is a crystalline carbon, the amorphous carbon is not limited in the insertion and desorption paths of lithium ions and is difficult to expand the electrode. Thus, the amorphous carbon exhibits high output characteristics and has a long life. Particularly, It can have a high reversible capacity.

Examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke, and the like. For example, the carbon-based material may be soft carbon.

The soft carbon means graphitizable carbon, which is arranged so that the atomic arrangement can easily form a layered structure, and is easily changed to a graphite structure with an increase in the heat treatment temperature. Since the soft carbon has a disordered crystal compared to graphite, there are many gates that assist in ion entry and exit, and diffusion of ions is easy because the degree of crystal disordering is lower than that of hard carbon. As a specific example, the carbon-based material may be low crystalline soft carbon.

The average particle diameter (D50) of the carbon-based material may be 1 탆 to 50 탆. Specifically 1 to 40 占 퐉, 1 to 30 占 퐉, 1 to 20 占 퐉, 5 to 50 占 퐉, 10 to 50 占 퐉, 5 to 15 占 퐉 and 6 to 12 占 퐉. In this case, suitable pores are present in the negative electrode composition, thereby generating a large number of activation sites that serve as passages or storage sites for lithium ions connecting the crystalline portions, thereby reducing the contact resistance, This is possible.

D50 means the particle size at 50% by volume in the cumulative size-distribution curve.

The carbonaceous material may be in various forms such as a spherical shape, a plate shape, a flake shape, a fiber shape and the like, and may be, for example, a needle shape.

The specific surface area of the carbon-based material may be 0.1 to 20 m ² / g, specifically 0.1 to 10 m ² / g, 1 to 20 m ² / g, 1 to 10 m ² / g, ² / g. When a carbonaceous material having a specific surface area in the above range is used as a negative electrode active material, a low-crystalline carbonaceous material can be obtained, thereby obtaining excellent high-rate characteristics and life characteristics at a high rate.

The tap density of the carbon-based material (tap density) is 0.30 to 10.00 g / cm ³ days and may, specifically, 0.60 to 10.00 g / cm ^3, 0.30 to 5.00 g / cm ^3, 0.60 to 5.00 g / cm ³ il . When a carbonaceous material having a tap density in the above range is used as a negative electrode active material, a low-crystalline carbonaceous material can be obtained, thereby obtaining excellent high-rate characteristics and life characteristics at a high rate.

The negative electrode active material layer may further include a binder.

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

The negative electrode active material layer may further include a conductive material.

The conductive material is used for imparting conductivity to the electrode. Any material can be used as long as it does not cause any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, , Carbon fiber such as carbon fiber, metal powder such as nickel, aluminum, silver or the like, metallic material such as metal fiber, polyphenylene derivative, or the like, or a conductive material including a mixture thereof.

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

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

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

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate , gamma-gamma -butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. As the alcoholic solvent, ethyl alcohol, isopropyl alcohol and the like can be used. As the aprotic solvent, R-CN (R is a linear, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, , A double bond aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolanes, and the like can be used .

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

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

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

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

[Chemical Formula 1]

In Formula 1, R ₁ to R ₆ are the same or different and selected from the group consisting of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group, and combinations thereof.

Specific examples of the aromatic hydrocarbon-based organic solvent include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-tri Fluorobenzene, 1,2,4-trifluorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1 , 2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, Examples of the solvent include 2,4-triiodobenzene, toluene, fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,3,4- Dichlorotoluene, 2,3-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2, 3-trifluorotoluene, 3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2 , 5-diiodotoluene, 2,3,4-triiodotoluene, 2,3,5-triiodotoluene, xylene, and combinations thereof.

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

(2)

In Formula 2, R ₇ and R ₈ are the same or different and selected from the group consisting of hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ), and an alkyl group having 1 to 5 fluorinated carbon atoms, At least one of R ₇ and R ₈ is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO ₂ ) and an alkyl group having 1 to 5 fluorinated carbon atoms, provided that R ₇ and R ₈ are both hydrogen .

Representative examples of the ethylene carbonate-based compound include diethylene carbonate, diethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, and the like, such as difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, . When such a life improving additive is further used, its amount can be appropriately adjusted.

The lithium salt is dissolved in an organic solvent to act as a source of lithium ions in the cell to enable operation of a basic lithium secondary battery and to promote the movement of lithium ions between the anode and the cathode. The lithium salt Representative examples are _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiN (SO 2 C 2 F 5) 2, Li (CF 3 SO 2) 2 N, LiN (SO 3 C 2 F 5) 2, _{LiC 4 F 9 SO 3, LiClO} 4, LiAlO 2, LiAlCl 4, LiN (C x F 2x + 1 SO 2) (C y F 2y + 1 SO 2) ( where, x and y are natural numbers), LiCl, The present invention includes one or two or more supporting electrolyte salts selected from the group consisting of LiI and LiB (C ₂ O ₄ ) ₂ (lithium bis (oxalato) borate (LiBOB) Is preferably used in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has an appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance and the lithium ion can move effectively.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. The separator may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene triple layer separator, a polypropylene / polyethylene / poly It is needless to say that a mixed multilayer film such as a propylene three-layer separator and the like can be used.

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

(Example 1)

5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle size of 6.8 mu m, 4 wt% of acetylene black (electrochemicals) conductive material, and 85 wt% of LiCoO ₂ having an average particle diameter of 6.6 mu m and polyvinylidene fluoride binder 6 % By weight were mixed in N-methylpyrrolidone solvent to prepare a cathode active material slurry.

The positive electrode active material slurry was coated on an Al foil having a thickness of 15 탆, dried at 100 캜, and pressed to prepare a positive electrode having a density of 2.6 (positive electrode active material layer).

85% by weight of soft carbon (Hitachi) anode active material having an average particle size of 10 탆, 5% by weight of acetylene black (electrochemical industry) and 10% by weight of polyvinylidene fluoride binder in a solvent of N-methylpyrrolidone To prepare a negative electrode active material slurry.

The negative electrode active material slurry was coated on a Cu foil having a thickness of 10 mu m, dried at 100 DEG C and then rolled to produce a negative electrode having a density of 1.2 (negative active material layer).

A separator was sandwiched between the positive electrode and the negative electrode prepared in the above process, and a jelly roll was prepared by winding in a cylindrical state. As the separator, a V25CGD microporous membrane having a thickness of 25 mu m was used.

The prepared jelly roll was placed in a 18650 size battery case, and an electrolytic solution was injected to prepare a lithium secondary battery. Ethylene carbonate and ethyl methyl carbonate mixed solution (3: 7 by volume) in which 1.0 M LiPF ₆ was dissolved were used as the electrolyte solution.

(Example 2)

The average particle diameter of 6.4㎛ of LiCoO ₂ 85% by weight, the activated carbon has an average particle diameter 6.65㎛ (Kuraray Co., pitch based), 5 wt% of acetylene black (electro and Chemicals, Inc.), 4 wt% of the conductive material and polyvinylidene fluoride binder 6 Except that the lithium salt of the lithium salt of the present invention was mixed in an N-methylpyrrolidone solvent to prepare a cathode active material slurry.

(Example 3)

5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 8.08 탆, 4 wt% of acetylene black (Electrochemical Industries) conductive material and 85 wt% of LiCoO ₂ having an average particle diameter of 6.6 탆 and polyvinylidene fluoride binder 6 Except that the lithium salt of the lithium salt of the present invention was mixed in an N-methylpyrrolidone solvent to prepare a cathode active material slurry.

(Example 4)

The average particle diameter of 5㎛ of LiCoO ₂ 85% by weight, the activated carbon has an average particle diameter 6.65㎛ (Kuraray Co., pitch based), 5 wt% of acetylene black (electro and Chemicals, Inc.), 4 wt% of the conductive material and polyvinylidene fluoride binder 6 Except that the lithium salt of the lithium salt of the present invention was mixed in an N-methylpyrrolidone solvent to prepare a cathode active material slurry.

(Example 5)

, 5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle size of 7 탆, 4 wt% of acetylene black (electrochemical industry) conductive material, and 85 wt% of LiCoO ₂ having an average particle diameter of 5 탆 and polyvinylidene fluoride binder 6 Except that the lithium salt of the lithium salt of the present invention was mixed in an N-methylpyrrolidone solvent to prepare a cathode active material slurry.

(Example 6)

The average particle diameter of 5㎛ of LiCoO ₂ 85% by weight, the activated carbon has an average particle diameter 8㎛ (Kuraray Co., pitch based), 5 wt% of acetylene black (electro and Chemicals, Inc.), 4 wt% of the conductive material and polyvinylidene fluoride binder 6 Except that the lithium salt of the lithium salt of the present invention was mixed in an N-methylpyrrolidone solvent to prepare a cathode active material slurry.

(Example 7)

, 5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 8 탆, 4 wt% of acetylene black (electrochemical industry) conductive material, and 85 wt% of Li (NiCoMn) O ₂ having an average particle diameter of 3.5 탆, 6 weight% of fluoride binder was mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry and the same procedure as in Example 1 was carried out except that the mixture density of the electrode plate was 2.4 g / cc. A battery was prepared.

(Example 8)

The average particle diameter of the Li 3.5㎛ (NiCoMn) O ₂ 85% by weight, activated carbon having an average particle diameter of 5㎛ (Kuraray Co., pitch based), 5 wt% of acetylene black (electro and Chemicals, Inc.), 4 wt% of the conductive material and polyvinylidene 6 weight% of fluoride binder was mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry and the same procedure as in Example 1 was carried out except that the mixture density of the electrode plate was 2.4 g / cc. A battery was prepared.

(Example 9)

5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle size of 14 탆, 4 wt% of acetylene black (Electrochemical Industries) conductive material, and 85 wt% of Li (NiCoMn) O ₂ having an average particle diameter of 3.5 탆, 6 weight% of fluoride binder was mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry and the same procedure as in Example 1 was carried out except that the mixture density of the electrode plate was 2.4 g / cc. A battery was prepared.

(Example 10)

, 5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 24 탆, 4 wt% of acetylene black (electrochemical industry) conductive material, and 85 wt% of LiN (NiCoMn) O ₂ having an average particle diameter of 3.5 탆, 6 weight% of fluoride binder was mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry and the same procedure as in Example 1 was carried out except that the mixture density of the electrode plate was 2.4 g / cc. A battery was prepared.

(Example 11)

, 5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 8 탆, 4 wt% of acetylene black (electrochemical industry) conductive material, and 85 wt% of LiFePO ₄ having an average particle diameter of 0.35 탆 and polyvinylidene fluoride binder 6 Except that the cathode active material slurry was prepared by mixing LiPF 6 and LiPO 4 in a solvent of N-methylpyrrolidone in an amount of 1 wt% to 1 wt%, and the electrode plate had a compound density of 1.9 g / cc. .

(Example 12)

5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 5 탆, 4 wt% of acetylene black (electrochemicals) conductive material and 85 wt% of LiFePO ₄ having an average particle diameter of 0.35 탆 and polyvinylidene fluoride binder 6 % By weight in a N-methylpyrrolidone solvent to prepare a positive electrode active material slurry, and a compound density of 1.9 g / cc, to prepare a lithium secondary battery.

(Comparative Example 1)

, 5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 4 탆, 4 wt% of acetylene black (Electrochemical Industries) conductive material and 85 wt% of LiCoO ₂ having an average particle diameter of 5 탆 and polyvinylidene fluoride binder 6 Except that the lithium salt of the lithium salt of the present invention was mixed in an N-methylpyrrolidone solvent to prepare a cathode active material slurry.

(Comparative Example 2)

, 5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle size of 3.85 탆, 4 wt% of acetylene black (electrochemicals) conductive material, and 85 wt% of LiCoO ₂ having an average particle diameter of 6.6 탆 and polyvinylidene fluoride binder 6 Except that the lithium salt of the lithium salt of the present invention was mixed in an N-methylpyrrolidone solvent to prepare a cathode active material slurry.

(Comparative Example 3)

, 5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 4 탆, 4 wt% of acetylene black (Electrochemical Industries) conductive material and 85 wt% of LiCoO ₂ having an average particle diameter of 5 탆 and polyvinylidene fluoride binder 6 Except that the lithium salt of the lithium salt of the present invention was mixed in an N-methylpyrrolidone solvent to prepare a cathode active material slurry.

(Comparative Example 4)

, 90 wt% of LiCoO ₂ having an average particle diameter of 5 탆, 0 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 6.8 탆, 4 wt% of acetylene black (electrochemicals) conductive material and polyvinylidene fluoride binder 6 % By weight was mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry and hard carbon was used as a negative electrode active material, thereby preparing a lithium secondary battery.

(Comparative Example 5)

90 wt% of LiNiCoMnO ₂ having an average particle diameter of 3.5 μm, 0 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 8 μm, 4 wt% of acetylene black (electrochemicals) conductive material and polyvinylidene fluoride binder 6 % By weight in a solvent of N-methylpyrrolidone to prepare a positive electrode active material slurry. In this case, in the same manner as in Example 1 except that the mixture density of the positive electrode was 2.4 g / cc and the hard carbon was used as the negative electrode active material Thereby preparing a lithium secondary battery.

(Comparative Example 6)

90 wt% of LiFePO ₄ having an average particle diameter of 0.35 μm, 0 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 8 μm, 4 wt% of acetylene black (electrochemicals) conductive material and polyvinylidene fluoride binder 6 % By weight in a solvent of N-methylpyrrolidone to prepare a positive electrode active material slurry. In this case, in the same manner as in Example 1 except that the mixture density of the positive electrode was 2.2 g / cc and the hard carbon was used as the negative electrode active material Thereby preparing a lithium secondary battery.

(Comparative Example 7)

5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 12 탆, 4 wt% of acetylene black (electrochemicals) conductive material and 85 wt% of LiFePO ₄ having an average particle diameter of 0.35 탆 and polyvinylidene fluoride binder 6 % By weight in an N-methylpyrrolidone solvent to prepare a positive electrode active material slurry. The slurry was prepared in the same manner as in Example 1 except that the mixture density of the positive electrode was 1.9 g / cc and hard carbon was used as the negative active material Thereby preparing a lithium secondary battery.

(Comparative Example 8)

5 wt% of activated carbon (Kuraray Co., pitch system) having an average particle diameter of 14 탆, ₄ wt% of acetylene black (electrochemicals) conductive material, and 85 wt% of LiFePO ₄ having an average particle diameter of 0.35 탆 and polyvinylidene fluoride binder 6 % By weight in a solvent of N-methylpyrrolidone to prepare a positive electrode active material slurry. In this case, in the same manner as in Example 1 except that the mixture density of the positive electrode was 2.2 g / cc and the hard carbon was used as the negative electrode active material Thereby preparing a lithium secondary battery.

Evaluation example 1: Initial capacity measurement

The lithium secondary batteries prepared according to Examples 1 to 12 and Comparative Examples 1 to 8 were subjected to constant current charging at a current of 0.2 C and terminated when the battery voltage reached 4.2 V. [ Subsequently, a constant current discharge was performed at a current of 0.2 C, and the process was terminated when the battery voltage reached 2.0 V. The capacity of the battery charged and discharged by this process was measured. The measured capacity was used as an initial capacity, and the results are shown in Table 1 below as a capacity of 0.2C.

Evaluation Example 2: High-speed discharge characteristic

Subsequently, a battery measured the initial capacity, a 1C current by performing a constant current charging, end, and 50C to a current was discharged down to 2.0V when the battery voltage becomes to be 4.2V. The capacity at this time was measured to calculate the 50 C discharge capacity ratio (50 C / 1 C,%) to the 1 C charge capacity. The results are shown in Table 1 below at a rate of 50 C as the high-rate discharge characteristics.

Evaluation Example 3: Life characteristics

The battery in which the initial capacity was measured was charged up to 4.2 V at 30 C and charged / discharged to discharge 2.0 V at 30 C was repeated 1000 times to measure the remaining capacity% of the 1000th discharge capacity with respect to the initial capacity. The results are shown in Table 1 below.

Evaluation Example 4: Electrical Conductivity Measurement

The electrical conductivities of the positive electrodes prepared in Examples 1 to 12 and Comparative Examples 1 to 8 were measured using an electrical conductivity meter (CIS Co., Ltd., resistance measuring equipment), and the results are shown in Table 1 .

anode Anode Active carbon particle size / active material particle diameter (%) Bipolar conductivity
(S / m) 0.2C capacity
(mAh / g) 50C rate
(50C / 1C) Remaining capacity%, 30C / 30C cycle
(1000th / first cycle,%) Example 1 LiCoO ₂ : 6.6 탆, 85 wt%
Activated carbon: 6.8 탆, 5 wt% Amorphous carbon 103 0.2 128 82% 89% Example 2 LiCoO ₂ : 6.4 탆, 85 wt%
Activated carbon: 6.65 占 퐉, 5 wt% Amorphous carbon 104 0.21 125 84% 88% Example 3 LiCoO ₂ : 6.6 탆, 85 wt%
Activated carbon: 8.08 탆, 5 wt% Amorphous carbon 122 0.14 132 81% 90% Example 4 LiCoO ₂ : 5 탆, 85 wt%
Activated carbon: 6.65 占 퐉, 5 wt% Amorphous carbon 133 0.11 129 83% 96% Example 5 LiCoO ₂ : 5 탆, 85 wt%
Activated carbon: 7 탆, 5 wt% Amorphous carbon 140 0.18 131 83% 91% Example 6 LiCoO ₂ : 5 탆, 85 wt%
Activated carbon: 8 탆, 5 wt% Amorphous carbon 160 0.17 125 83% 88% Example 7 LiNiCoMnO ₂ : 3.5 탆, 85 wt%
Activated carbon: 8 탆, 5 wt% Amorphous carbon 228 0.047 136 87% 85% Example 8 LiNiCoMnO ₂ : 3.5 탆, 85 wt%
Activated carbon: 5 탆, 5 wt% Amorphous carbon 142 0.043 132 86% 87% Example 9 LiNiCoMnO ₂ : 3.5 탆, 85 wt%
Activated carbon: 14 탆, 5 wt% Amorphous carbon 400 0.040 129 81% 84% Example 10 LiNiCoMnO ₂ : 3.5 탆, 85 wt%
Activated carbon: 24 탆, 5 wt% Amorphous carbon 685 0.038 128 71 80 Example 11 LiFePO ₄ : 0.35 탆, 85 wt%
Activated carbon: 8 탆, 5 wt% Amorphous carbon 2286 0.053 116 74% 83% Example 12 LiFePO ₄ : 0.35 탆, 85 wt%
Activated carbon: 5 탆, 5 wt% Amorphous carbon 1429 0.049 115 73% 81% Comparative Example 1 LiCoO ₂ : 5 탆, 85 wt%
Activated carbon: 4 탆, 5 wt% Amorphous carbon 40 0.092 129 65% 68% Comparative Example 2 LiCoO ₂ : 6.6 탆, 85 wt%
Activated carbon: 3.85 탆, 5 wt% Amorphous carbon 58 0.11 127 76% 66% Comparative Example 3 LiCoO ₂ : 5 탆, 85 wt%
Activated carbon: 4 탆, 5 wt% Amorphous carbon 80 0.117 129 80% 71% Comparative Example 4 LiCoO ₂ : 5 탆, 90 wt%
Activated carbon: 6.8 탆, 0 wt% Amorphous carbon 0 0.01 133 64% 61% Comparative Example 5 LiNiCoMnO ₂ : 3.5 탆, 90 wt%
Activated carbon: 8 탆, 0 wt% Amorphous carbon 0 0.023 138 65% 67% Comparative Example 6 LiFePO ₄ : 0.35 탆, 90 wt%
Activated carbon: 8 탆, 0 wt% Amorphous carbon 0 0.033 119 61% 64% Comparative Example 7 LiFePO ₄ : 0.35 탆, 85 wt%
Activated carbon: 12 탆, 5 wt% Amorphous carbon 3400 0.044 111 67% 69% Comparative Example 8 LiFePO ₄ : 0.35 탆, 85 wt%
Activated carbon: 14 탆, 5 wt% Amorphous carbon 4000 0.048 111 67% 70%

As shown in Table 1, it can be seen that the high rate characteristics (50C rate) and the remaining capacity% of the batteries of Examples 1 to 12 were much better than those of Comparative Examples 1 to 8.

From these results, it can be seen that a battery having excellent high output characteristics and cycle life characteristics can be provided according to the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, And it goes without saying that the invention belongs to the scope of the invention.

100: Lithium secondary battery
10: anode
20: cathode
30: Separator
40: electrode assembly

Claims (10)

A negative electrode including a negative electrode active material, and
A positive electrode comprising a positive electrode active material and activated carbon,
The negative electrode active material includes a carbon-based material having interlayer spacing (d ₀₀₂ ) of (002) plane of 0.34 nm to 0.50 nm in X-ray diffraction measurement using CuKαα,
Wherein the cathode active material comprises a lithium iron phosphate-based compound,
The average particle size of the activated carbon is preferably not less than 1000% and not more than 3000% of the average particle diameter of the cathode active material
Lithium secondary battery. The method of claim 1,
Wherein an average particle size of the activated carbon is 1000% or more and 2500% or less with respect to 100% of an average particle size of the cathode active material. The method of claim 1,
Wherein the cathode active material is an olivine structure. The method of claim 1,
Wherein the average particle diameter of the positive electrode active material is 0.1 to 20 占 퐉. The method of claim 1,
Wherein the activated carbon has an average particle diameter of 1 to 30 占 퐉. The method of claim 1,
Wherein the content of the activated carbon is 1 to 40% by weight based on the total amount of the cathode active material and the activated carbon. The method of claim 1,
Wherein the carbon-based material having the (002) plane interlayer distance of 0.34 nm to 0.50 nm is amorphous carbon. The method of claim 1,
The carbon-based material having the (002) plane interlayer distance of 0.34 nm to 0.50 nm is soft carbon, hard carbon, mesophase pitch carbide, fired cokes, or a combination thereof. The method of claim 1,
Wherein an average particle diameter of the carbon-based material having an interlayer distance of the (002) plane of 0.34 nm to 0.50 nm is 1 to 50 탆. The method of claim 1,
Wherein the positive electrode active material is a structure of secondary particles agglomerated with primary particles.

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