KR20150037330A - Rolling Machine Comprising Amorphous Carbon-Coated Press Rollers for Preparation of Electrode Sheet - Google Patents

Abstract

The present invention relates to an amorphous carbon-coated press roller and a rolling machine comprising the same, and more specifically, to a rolling machine for rolling an electrode sheet in which one or both surfaces of a current collector is coated with electrode composites, the rolling machine which comprises: a pair of press rollers rotating with each being spaced apart by a width narrower than a thickness of an electrode sheet, such that the electrode sheet can be rolled; and an amorphous carbon-coated layer coated on the surface of the press rollers.

Description

(Rolling Machine Comprising Amorphous Carbon-Coated Press Rollers for Preparation of Electrode Sheet)

The present invention relates to an electrode sheet rolling apparatus including a rolling roller coated with amorphous carbon and more particularly to an apparatus for rolling an electrode sheet coated with an electrode mixture on one surface or both surfaces of a current collector, And an amorphous carbon coating layer coated on the surfaces of the rolling rollers, the pair of rolling rollers rotating at a position spaced apart from each other by a width narrower than the thickness of the electrode sheet so as to be rolled while passing therethrough will be.

Lithium secondary batteries have been used not only as energy sources for mobile devices but also as power sources for electric vehicles (EVs) and hybrid electric vehicles (HEVs) in recent years. The use area is also expanding.

The manufacturing process of such a lithium secondary battery is roughly classified into an electrode process, a granulation process, and a chemical process. The electrode process may be divided into an active material mixing process, an electrode coating process, a rolling process, a slitting process, and a winding process.

Among them, the rolling process is a process of passing an electrode through two rolling rollers heated at high temperature to a desired thickness so as to increase the capacity density of the coated electrode and increase the adhesion between the electrode current collector and the electrode active material.

When such a rolling roller is subjected to a rolling process for a predetermined period of time, a thickness step is generated on the surface of the rolling roller which is in contact with the edge of the electrode sheet on which the active material is not applied or the non-coated portion due to wear of the electrode sheet and the rolling roller . In addition, when changing the type of the battery to be produced, the width of the electrode sheet to be rolled by each kind (for example, cylindrical battery, prismatic battery, polymer battery, etc.) There is a problem in that the thickness variation of the electrode sheets produced due to the increase in thickness is increased.

When the electrode sheet is manufactured using such a worn rolling roller, the electrochemical performance and safety of the battery cell is deteriorated due to the thickness deviation of the electrode sheet continuously generated.

In addition, when a thickness variation occurs in the past, there has been a problem that the worker manually adjusts the clearance between the rolling rollers or increases the productivity and manufacturing cost by replacing a new rolling roller.

Therefore, in order to prevent abrasion of the rolling roller, a technique of increasing the hardness of the surface of the rolling roller through a coating process has been applied. Particularly, hard chrome plating is inexpensive, And it is widely used, and the service can be easily provided.

However, the hard chrome-plated rolling roller has a relatively low surface hardness, and has not yet solved the problem of lowering the productivity and manufacturing cost in accordance with the short replacement period of the rolling roller.

Also, in recent years, the development of technology related to a device using a secondary battery has been accelerated, and various devices with a new structure have been put on the market.

Accordingly, there is a great need for a technique capable of solving the above problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

Specifically, it is an object of the present invention to provide a rolling apparatus capable of reducing the manufacturing cost and improving the reliability of the electrode sheet by improving the surface hardness of the rolling roller.

In order to achieve the above object, according to the present invention,

A pair of rolling rollers rotating at a position spaced apart from each other by a width narrower than the thickness of the electrode sheet so that the electrode sheet can be rolled while passing through the electrode sheet, And an amorphous carbon coating layer coated on the surface of the rolling rollers.

That is, by including the amorphous carbon coating layer coated on the surface of the rolling rollers, it is possible to have a surface hardness superior to that of the conventional rolling rollers, so that the replacement period of the rolling rollers becomes longer, and the thickness of the electrode sheet The amount of deviation can be reduced.

Since the thickness of the electrode sheet can be changed according to the type or the capacity of the battery cell produced by the rolling apparatus, the spaced apart positions of the rolling rollers can be adjusted according to the thickness of the electrode sheet, For example, 60% to 99% of the thickness of the electrode sheet.

In one specific example, the DLC coating can be applied to a substrate such as, for example, plasma enhanced chemical vapor deposition (PECVD), ion plating, laser ablation, and filtered vacuum arc plasma ) ≪ / RTI > coating).

The amorphous carbon coating may be a diamond-like-carbon (DLC) coating in more detail, but may be formed by one or more methods selected from the group consisting of oxynitride coating, TiAlN coating, TiN coating and TiCN coating, .

In the case of conventional hard chromium plating, although the coating thickness is thickly coated at 50 micrometers or more, there is a problem that the hardness of the coated surface is relatively low from 700 Hv or more to less than 1,000 Hv. On the other hand, the coating layer according to the present invention has a relatively thinner thickness than the hard chromium plating treatment, but exhibits excellent hardness.

In one specific example, the thickness of the amorphous carbon coating layer may be from 1 nanometer to 3 micrometers. In particular, when the thickness is less than 1 nanometer, the hardness required by the present invention can not be exhibited. On the other hand, if the thickness is more than 3 micrometers, the cost of the material increases and the coating time becomes long.

Since the rolling roller of the present invention has a surface hardness similar to that of diamond having the highest hardness, it is possible to increase the lifetime of the rolling apparatus, reduce the manufacturing cost, and reduce the thickness variation of the produced electrode sheet . Therefore, the surface hardness of the rolling roller according to the present invention may be 1000 Hv to 6000 Hv, more specifically, 2500 Hv to 5500 Hv, and more specifically, 3000 Hv to 5000 Hv.

When the friction coefficient of the rolling roller is low, the frictional force due to the rolling process is reduced, and the amount of wear on the surface of the rolling roller can be reduced. Therefore, the coefficient of friction of the rolling roller according to the present invention may be 0.1 to 0.2.

In one specific example, the rolling apparatus according to the present invention may further include a thickness control section, a spacing regulating section, an automatic executing section, a unique character recognizing section, a conveying roller, and a winding roll. A side schematic view of an exemplary rolling apparatus according to one embodiment is shown in FIG.

1, the rolling apparatus according to the present invention includes a rolling roller unit 100, a thickness control unit 200, a spacing space adjusting unit 300, an automatic execution unit 400, a unique character recognition unit 500, Conveying rollers 21, 22, 23, and 24, and a take-up roll 30.

The rolling roller unit 100 includes an upper rolling roller 110 and a lower rolling roller 120. The electrode sheet 10 is separated into a space between the upper rolling roller 110 and the lower rolling roller 120 And then rolled.

In one specific embodiment, the thickness control section measures the thickness of the center portion corresponding to 80 to 90% of the entire width of each of the electrode sheets located at the outermost one of the two or more rolled electrode sheets, The thickness value is compared with the preset reference electrode sheet thickness value, and the correction value is transmitted to the spacing space adjusting unit to adjust the thickness of the electrode sheet in real time by moving the upper rolling roller and the lower rolling roller up and down, respectively.

The present invention also provides a method of manufacturing an electrode for a secondary battery,

(a) coating an electrode mixture including an electrode active material, a binder, a conductive material, and a filler on one surface or both surfaces of a current collector and drying to form an electrode mixture coating layer;

(b) rolling the electrode material mixture coating layer using the electrode sheet rolling apparatus according to the present invention;

(c) applying the process (a) and the process (b) once or twice or more.

The electrode sheet produced using the electrode sheet rolling apparatus according to the present invention may have an electrode mixture coating layer including an electrode active material, a binder, a conductive material, and a filler on one surface or both surfaces of the current collector have.

The electrode active material may be a cathode active material or an anode active material, and a specific structure thereof will be described below.

In one specific example, the thickness of the electrode mixture coating layer may be between 5 micrometers and 400 micrometers. If the thickness of the coating layer is too small, the battery capacity decreases. On the other hand, if the thickness of the coating layer is too large, there is a possibility that the electrode mixture is desorbed and internal resistance is increased.

The density of the electrode active material may be 1.5 g / cc to 5 g / cc. When the density of the electrode active material is high, it is possible to maintain a large contact area with the current collector, and thus it is possible to form an excellent conductive network, so that the electric conductivity is excellent.

In one specific example, the present invention may be a secondary battery including the electrode sheet, and the secondary battery is not particularly limited as long as it is capable of providing a high voltage and a high current. For example, It can be a large lithium secondary battery.

The configuration of such a lithium secondary battery will be described below.

The lithium secondary battery includes a cathode which is produced by applying a mixture of a positive electrode active material, a conductive material and a binder (positive electrode material mixture) on a positive electrode collector, followed by drying and pressing and a substantially similar method, If necessary, a filler may be further added to the mixture.

The cathode current collector is generally made to have a thickness of 3 micrometers to 500 micrometers. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The cathode active material may be, for example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ) or a compound substituted with one or more transition metals; 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 , LiMnO ₂ and the like; Lithium copper oxide (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 ; A Ni-site type lithium nickel oxide represented by the formula 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); Formula _{LiMn 2-x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Lithium nickel manganese cobalt composite oxides such as LiNi _1/3 Mn _1/3 Co _1/3 O ₂ and LiNi _0.5 Mn _0.3 Ni _0.2 ; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and LiNi _x Mn _2-x O ₄ (0.01 ≦ x ≦ 0.6).

The conductive material is usually added in an amount of 1 wt% to 30 wt% based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black 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, aluminum, and nickel powder; Conductive whiskey 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.

The binder is a component that assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30 wt% based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, and various copolymers.

The filler is optionally used as a component for suppressing 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-based polymerizers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The negative electrode collector is generally made to have a thickness of 3 micrometers to 500 micrometers. Such an anode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a 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 collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The negative electrode active material may be, for example, graphite having a completely layered crystal structure such as natural graphite, soft carbon having a low crystalline layered crystal structure (a structure in which hexagonal honeycomb planes of carbon are arranged in layers) Carbon and graphite materials such as hard carbon, artificial graphite, expanded graphite, carbon fiber, hard graphitizable carbon, carbon black, carbon nanotube, fullerene, activated carbon and the like in which these structures are mixed with amorphous portions; _{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' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{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 Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like; Complexes of the above compounds may be used.

Such a lithium secondary battery may have a structure in which a lithium salt-containing electrolyte is impregnated in an electrode assembly having a separator interposed between a cathode and an anode.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 micrometer to 10 micrometers, and the thickness is generally 5 micrometers to 300 micrometers. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The electrolyte solution containing the lithium salt is composed of an electrolyte solution and a lithium salt. The electrolyte solution may be a non-aqueous organic solvent, an organic solid electrolyte, or an inorganic solid electrolyte, but is not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

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 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

In one _{example, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) A lithium salt of _2, and so on, highly dielectric solvent of DEC, DMC or EMC linear in FIG solvent cyclic carbonate and a low viscosity of the EC or PC Carbonate in a mixed solvent to prepare a non-aqueous electrolyte containing a lithium salt.

The present invention also provides a device using the lithium secondary battery as a power source or a power source, wherein the device is used for a mobile phone, a portable computer, a smart phone, a tablet PC, a smart pad, a netbook, a LEV (Light Electronic Vehicle) A car, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device.

The structure and manufacturing method of such a device are well known in the art, so a detailed description thereof will be omitted herein.

As described above, since the electrode sheet rolling apparatus according to the present invention includes the amorphous carbon coating layer on the surface of the rolling roller, the wear amount of the rolling roller generated in the rolling process can be reduced, It is possible to increase the replacement cycle of the rolling roller, thereby improving the productivity of the battery and reducing the manufacturing cost.

1 is a side schematic view of an exemplary rolling apparatus according to one embodiment of the present invention;
2 is a graph showing the surface hardness of a specimen produced according to an embodiment of the present invention and a comparative example;
3 is a graph showing the result of a taber abrasion test in an experimental example of the present invention;
4 is a conceptual diagram of the method of the tabar abrasion test;
Fig. 5 is a photograph of a specimen before the abrasion test of Examples and Comparative Examples of the present invention; Fig.
Fig. 6 is a photograph of a specimen after the abrasion test of Examples and Comparative Examples of the present invention.

Hereinafter, the present invention will be described in more detail with reference to some embodiments thereof, but the scope of the present invention is not limited thereto.

≪ Example 1 >

As shown in FIG. 4, a diamond-like-carbon (DLC) coating layer is formed on a surface of a specimen of a bearing steel (SUJ2) having a thickness of 3 mm by plasma enhanced chemical vapor deposition (PECVD) The surface hardness, the coating thickness, and the friction coefficient of the specimen are shown in Table 1 below.

≪ Comparative Example 1 &

As shown in FIG. 4, the surface of a specimen made of a bearing steel (SUJ2) having a thickness of 3 mm was plated with hard chromium (Hard Cr) to prepare a specimen. The surface hardness, The results are shown in Table 1 below.

Example 1 Comparative Example 1 Exterior Matte black (see FIG. 4) The glossy metal (see Figure 4) Vickers Hardness (Hv) 3,000 to 5,000 700 to 1,000 Coating thickness
(Micrometer) 0.1 to 0.2 Over 50 Coefficient of Friction (μ) 0.1 to 0.2 0.41

<Experimental Example>

Three specimens according to Example 1 and Comparative Example 1 were prepared according to the following abrasion measurement method and subjected to wear tests. The results are shown in the graph of FIG.

(Wear measurement)

In order to measure the abrasion resistance of the plated material, a taber abrasion test was performed. Specifically, as shown in FIG. 4, the Taber abrasion test is carried out by putting a specimen on a rotatable disk, pressing two uniform abrasion wheels with a load of 1 kgf, and then rotating the specimen at 70 rpm And the changed specimen weight was measured before and after abrading at 1,000, 3,000, and 5,000 test times, respectively.

2, the hardness of Comparative Example is 700 Hv to 1,000 Hv, whereas the hardness of Example 1 is 3,000 Hv, although the coating thickness of the coating layer is thinner than that of the Comparative Example. To 5,000 Hv. On the other hand, it can be seen that the coefficient of friction is lower when DLC coating is applied.

3, the amount of abrasion of Example 1 is 5.7 mg when the number of abrasion tests is 1,000, 8.6 mg when the abrasion number is 3,000, and 19.8 mg when the abrasion resistance is 5,000. That is, it can be seen that as the number of times of wear test increases, the difference in wear amount becomes larger.

Therefore, in Example 1 of the present invention, as compared with the comparative example, not only the shape of each test number is small, but also the amount of wear to be increased according to the wear time which can determine the life of the rolling roller is also smaller.

In summary, the rolling roller having the amorphous carbon coating layer according to the present invention is excellent in mechanical properties, so that the wear amount of the surface area is relatively small in the rolling process, so that the electrode sheet of superior quality can be manufactured, So that the manufacturing cost can be reduced.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (15)

An apparatus for rolling an electrode sheet coated with an electrode mixture on one surface or both surfaces of a current collector,
A pair of rolling rollers rotating at a position spaced apart from each other by a width narrower than the thickness of the electrode sheet so that the electrode sheet can be rolled while passing therethrough; And
An amorphous carbon coating layer coated on the surface of the rolling rollers;
Wherein the electrode sheet rolling apparatus comprises: 2. The electrode sheet rolling apparatus according to claim 1, wherein the rolling rollers are spaced apart from each other by a distance of 60% to 99% of the thickness of the electrode sheet. The electrode sheet rolling apparatus according to claim 1, wherein the amorphous carbon coating is a diamond-like-carbon (DLC) coating. 4. The method of claim 3, wherein the DLC coating is formed by plasma enhanced chemical vapor deposition (PECVD), ion plating, laser ablation, and filtered vacuum arc plasma coating. Wherein the electrode sheet is rolled by one or more methods selected from the group consisting of the following. The electrode sheet rolling apparatus according to claim 1, wherein the thickness of the amorphous carbon coating layer is 1 nanometer to 3 micrometers. The electrode sheet rolling apparatus according to claim 1, wherein the surface hardness of the rolling roller is 1000 Hv to 6000 Hv. The electrode sheet rolling apparatus according to claim 1, wherein the rolling roller has a coefficient of friction of 0.1 to 0.2. 2. The electrode sheet rolling apparatus according to claim 1, wherein the rolling apparatus further comprises a thickness control section, a spacing space adjusting section, an automatic executing section, a unique character recognizing section, a conveying roller, and a winding roll. A method for producing an electrode sheet for a secondary battery,
(a) coating an electrode mixture including an electrode active material, a binder, a conductive material, and a filler on one surface or both surfaces of a current collector and drying to form an electrode mixture coating layer;
(b) rolling the electrode material mixture coating layer using the electrode sheet rolling apparatus according to any one of claims 1 to 8;
(c) applying the process (a) and the process (b) one or more times;
&Lt; / RTI &gt; 9. An electrode sheet produced by using the electrode sheet rolling apparatus according to any one of claims 1 to 9, wherein the electrode sheet comprises an electrode active material, a binder, a conductive material, and a filler on one surface or both surfaces of the current collector Wherein an electrode mixture coating layer is formed on the surface of the electrode sheet. The electrode sheet for a secondary battery according to claim 10, wherein the thickness of the electrode mixture coating layer is 5 micrometers to 400 micrometers. The electrode sheet for a secondary battery according to claim 10, wherein the electrode active material has a density of 1.5 g / cc to 5 g / cc. A lithium secondary battery comprising the electrode sheet according to claim 10. A device using the lithium secondary battery according to claim 13 as a power source or a power source. 15. The method of claim 14, wherein the device is selected from the group consisting of a mobile phone, a portable computer, a smart phone, a tablet PC, a smart pad, a netbook, a LEV (Light Electronic Vehicle), an electric vehicle, a hybrid electric vehicle, Device. &Lt; / RTI &gt;

Images