KR101684347B1 - Electrode Assembly Having Insulating Material Added on Outermost Surface and Secondary Battery Comprising the Same - Google Patents

Abstract

More particularly, the present invention relates to an electrode assembly in which an insulating material is added to an outermost surface and a secondary battery including the same, and more particularly, to an electrode assembly in which a separator is interposed between an anode and a cathode, Wherein each of the electrodes has a structure in which an electrode active material layer is coated on one or both surfaces of the sheet-like collector; And an insulating material is added to an outermost surface of the electrode assembly.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode assembly having an insulating surface on an outermost surface thereof,

More particularly, the present invention relates to an electrode assembly in which an insulating material is added to an outermost surface and a secondary battery including the same, and more particularly, to an electrode assembly in which a separator is interposed between an anode and a cathode, Wherein each of the electrodes has a structure in which an electrode active material layer is coated on one or both surfaces of a sheet-like collector, and an insulating material is added to an outermost surface of the electrode assembly. .

As the technology development and demand for mobile devices have increased, the demand for secondary batteries has increased sharply as an energy source. Among such secondary batteries, lithium secondary batteries having high energy density and operating potential, long cycle life, Have been commercialized and widely used.

In addition, as the interest in environmental issues grows, researches on electric vehicles and hybrid electric vehicles that can replace fossil fuel-based vehicles such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, . Although nickel-metal hydride secondary batteries are mainly used as power sources for such electric vehicles and hybrid electric vehicles, researches on the use of lithium secondary batteries having high energy density and discharge voltage have been actively carried out and some of them have been commercialized.

The secondary battery may be classified according to how the electrode assembly having the anode / separator / cathode structure is formed. Typically, the jelly-roll having the structure in which the anode and the cathode are wrapped with the separator interposed therebetween, (Stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, and stacked / folded type Electrode assemblies.

Such a secondary battery is generally manufactured by incorporating an electrode assembly composed of a positive electrode plate and a negative electrode plate coated with an anode and a negative electrode active material, and a separator interposed therebetween, in a pouch-shaped case of an aluminum laminate sheet.

FIG. 1 schematically shows a general structure of a typical conventional pouch-type secondary battery as an exploded perspective view.

1, the pouch type secondary battery 10 includes an electrode assembly 30, electrode taps 40 and 50 extending from the electrode assembly 30, electrodes 40 and 50 welded to the electrode taps 40 and 50, Leads 60 and 70, and a battery case 20 for accommodating the electrode assembly 30. [

The electrode assembly 30 is a power generation element in which an anode and a cathode are sequentially stacked with a separation membrane interposed therebetween. The electrode assembly 30 has a stacked or stacked / folded structure. The electrode tabs 40 and 50 extend from each electrode plate 30 of the electrode assembly 30 and the electrode leads 60 and 70 are connected to a plurality of electrode tabs 40 and 50 extending from each electrode plate, Respectively, and a part of the battery case 20 is exposed to the outside. An insulating film 80 is attached to the upper and lower surfaces of the electrode leads 60 and 70 in order to increase the degree of sealing with the battery case 20 and at the same time to ensure an electrically insulated state.

The battery case 20 is made of an aluminum laminate sheet, provides a space for accommodating the electrode assembly 30, and has a pouch shape as a whole. 1, a plurality of positive electrode tabs 40 and a plurality of negative electrode tabs 50 may be coupled to the electrode leads 60 and 70. In the stacked electrode assembly 30, The inner top is spaced from the electrode assembly 30.

On the other hand, in a lithium secondary battery used in a conventional small-sized battery, a lithium-cobalt composite oxide having a layered structure is used for the anode and a graphite-based material is used for the cathode. In the case of the lithium cobalt composite oxide, Soine cobalt is very expensive and has a drawback in that it is not suitable for electric vehicles in terms of safety. Therefore, a lithium manganese composite oxide having a spinel structure composed of manganese, which is inexpensive and excellent in safety, may be suitable as the anode of a lithium secondary battery for an electric vehicle, and lithium-titanium oxide may be suitable as a cathode.

In general, the lithium manganese oxide of the spinel structure has an advantage of being excellent in thermal stability, low in cost, and easy to synthesize. However, it has a problem of low capacity, poor lifetime due to side reaction, poor high temperature characteristics and low conductivity . For example, when the battery is overcharged at a high voltage, decomposition reaction of the cathode active material occurs, dendrite growth of lithium metal at the cathode, decomposition reaction of the electrolyte occur, and the like.

Therefore, there is a high need for a technique for suppressing side reactions of the positive electrode and the negative electrode active material at a high voltage without deteriorating the battery characteristics.

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

The inventors of the present application confirmed that the side reactions described above were located at the outermost part of the battery cell and easily occurred on the electrode surface exposed to the electrolyte solution through the in-depth research and many experiments, thereby deteriorating the performance of the battery.

Accordingly, it is an object of the present invention to provide an electrode assembly for a lithium ion secondary battery in which an insulating material is added to an outermost surface of an electrode assembly, And to solve the problems such as deterioration of cell performance caused by participating in the cell reaction, and to provide a secondary battery which can improve the safety and life characteristics of the battery.

In order to achieve the above object, a secondary battery according to the present invention is a secondary battery in which an electrode assembly having a separator interposed between an anode and a cathode is embedded in a case together with an electrolytic solution, Wherein an electrode active material layer is applied to the electrode assembly, and an insulating material is added to an outermost surface of the electrode assembly.

In general, a lithium manganese-based oxide containing Mn in an amount of 50 mol% or more based on the total amount of transition metals is required to be charged at a high voltage of at least 4.4 to 5 V to obtain a high capacity. However, when the positive electrode active material is overcharged to 4.4 V or more, decomposition reaction of the positive electrode active material occurs as described above, and dendritic growth of lithium metal and decomposition reaction of the electrolyte occur in the negative electrode. In addition, the heat is accompanied by such a process, and the decomposition reaction and a number of side reactions proceed rapidly, and the electrolyte is consumed to deteriorate the performance of the battery. Particularly, such a side reaction occurs at the outermost part of the battery cell And can be easily generated on the electrode surface exposed to the electrolyte solution.

On the other hand, in the secondary battery according to the present invention, since the insulating material is added to the outermost surface of the electrode assembly, a side reaction or an outermost position between the current collector and the electrolyte, which is located at the outermost periphery of the electrode assembly, It is possible to solve problems such as deterioration of cell performance caused by the electrode material participating in the cell reaction.

In one specific example, the positive electrode may be a compound containing a lithium transition metal oxide having a spinel structure represented by the following formula (1) as a positive electrode active material.

Li _{1 + x} M _y Mn _2-xy O ₄ (1)

Wherein 0? X? 0.3, 0? Y? 1,

M is at least one selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Or more.

The secondary battery according to the present invention is particularly effective when an anode mixture coated with a lithium titanium oxide negative electrode active material such as Li _4/3 Ti _5/3 O _{4 is used} as a negative electrode. .

In some cases, one or more other lithium transition metal oxides known in the art may be added to the compound of Formula 1 to constitute a cathode active material. Other lithium transition metals known in the art may be added to the lithium titanium oxide One or more metal oxides may be mixed to constitute the cathode active material.

For example, the insulating resin may be an electrically insulating polymer resin or an electrically insulating polymer complex. Specific examples of the insulating resin include polypropylene (PP) resin, And may be at least one selected from the group consisting of polyethylene terephthalate (PET) and polyethylene (PE).

In addition, the insulating material may be a coating material, a film-like member, or the like. In the case of the film-like member, for example, one surface of the insulating material and the outermost surface of the electrode assembly may be coupled to each other in an overlapped state. In one specific example, an insulating material An adhesive may be applied to one surface of the substrate and bonded by an adhesive method. In some cases, one surface of the insulator may be bonded by thermal fusion within a range in which the electrode assembly is not deteriorated by heat.

A method of adhering one surface of an insulating material by an adhesive, wherein the adhesive includes various materials that provide an adhesive force capable of sufficiently maintaining adhesion of an insulating material to an outermost surface of an electrode assembly without affecting the operation of the battery For example, acrylic adhesive, SBR adhesive, or the like can be used.

In another specific example, the insulating material may be added to the outermost surface of the electrode assembly in the form of an insulating powder, and such insulating powder may be made of conventional non-conductive or semiconductor particles known in the art.

Specifically, the dielectric powder is MgO, TiO _2, ZrO _2, InSnO _2, Al ₂ O _3, SiO _2, GeO _2, MoO, SnO, Cr ₂ O ₃ and Sb ₂ O ₃ -SnO ₂ selected from the group consisting of In some cases, the insulating powder may contain a certain amount of water in the insulating powder itself, and may be applied while removing moisture through a drying process, if necessary.

The insulating powder can be added in various forms. For example, adhesion by the adhesive described above, adhesion in the state of being introduced into the film member, and the like can be considered.

On the other hand, an anode may be located on the outermost surface of the electrode assembly, and a cathode may be located on the outermost surface of the electrode assembly. For example, the electrode assembly may have a structure in which an electrode assembly layer including an electrode active material is applied to the surface of the collector on the outermost surface of the electrode assembly, and the insulating material is added to the outer surface of the electrode assembly layer, Or may have a structure in which an insulating material is directly attached to the entire surface.

The amount of addition of the insulating material is not particularly limited and may be, for example, 0.001% to 10% based on the total weight of the electrode assembly, but is not limited thereto.

The electrode assembly is not particularly limited as long as it includes a positive electrode and a negative electrode. Preferably, the electrode assembly is a wound type structure, a stack type structure, and a stack / folding type structure. Details of the stacked / folded structure of the electrode assembly are disclosed in Korean Patent Application Laid-Open Nos. 2001-0082058, 2001-0082059 and 2001-0082060, the contents of which are incorporated herein by reference. As a reference.

The battery case may be, for example, a rectangular or cylindrical metal can, and the cylindrical secondary battery may be formed by winding a positive electrode sheet and a negative electrode sheet in a state in which a separation membrane is interposed therebetween, - The roll can be manufactured by inserting it into a cylindrical can, impregnating the electrolyte, and sealing the can.

The prismatic secondary battery can be manufactured in the same manner as the cylindrical secondary battery except that a jelly-roll wound in an elliptical shape is inserted into a square can.

The secondary battery according to the present invention can be suitably applied to a pouch-type secondary battery in which an electrode assembly is embedded in a laminate sheet including a metal layer and a resin layer, for example, a pouch-shaped case of an aluminum laminate sheet.

Generally, a lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt.

The positive electrode is prepared, for example, by coating a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, and then drying the mixture. Optionally, a filler may be further added to the mixture.

The conductive material is usually added in an amount of 1 to 30% by weight 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 added to the binder in an amount of 1 to 30% by weight, based on the total weight of the mixture containing the cathode active material, as a component that assists in bonding between the active material and the conductive agent and bonding to the current collector. 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 positive electrode according to the present invention can be prepared by applying a slurry prepared by mixing a positive electrode mixture containing the above-described compounds to a solvent such as NMP, coating the positive electrode collector, followed by drying and rolling.

The cathode current collector is generally made to have a thickness of 3 to 500 mu m. Such a positive electrode collector is not particularly limited as long as it has conductivity without causing chemical change to the battery, and may be formed on the surface of stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel 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 present invention also provides a lithium secondary battery comprising the positive electrode, the negative electrode, the separator, and a non-aqueous electrolyte containing a lithium salt.

The negative electrode is prepared, for example, by coating a negative electrode mixture containing a negative electrode active material on a negative electrode collector and then drying the mixture. The negative electrode mixture may contain the above-described components as required.

The negative electrode collector is generally made to have a thickness of 3 to 500 mu m. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. Examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like, 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 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 to 10 mu m, and the thickness is generally 5 to 300 mu m. 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 lithium salt-containing nonaqueous electrolyte solution is composed of an electrolyte solution and a lithium salt. As the electrolyte solution, a nonaqueous organic solvent, an organic solid electrolyte, and an inorganic solid electrolyte may be used.

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 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

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), FPC (fluoro-propylene carbonate), and the like.

The present invention can also provide a device including the secondary battery as a power source.

The device according to the present invention can be preferably used for an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device, as well as a mobile device such as a mobile phone and a portable computer, as well as excellent lifetime characteristics and safety.

As described above, according to the secondary battery of the present invention, since the insulating material is added to the outermost surface of the electrode assembly, the side reaction or the outermost layer between the current collector and the electrolyte located at the outermost periphery of the electrode assembly during the charging / The present invention provides a secondary battery capable of solving the problems such as deterioration of cell performance caused by participation of an electrode material located in a battery cell and improving the safety and life characteristics of the battery.

1 is an exploded perspective view of a general structure of a conventional pouch type secondary battery;
2 is a schematic view of the structure of an electrode assembly according to one embodiment of the present invention;
3 is a schematic view of a structure of an electrode assembly according to another embodiment of the present invention;
4 is a graph showing lifetime characteristics according to Experimental Example 1. FIG.

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

2 and 3 are schematic diagrams of an electrode assembly structure according to embodiments of the present invention.

3, the electrode assembly 100 includes positive and negative electrode active materials 111 and 112 coated on both surfaces of the positive electrode current collectors 121 and 122 and negative electrode active materials 111 and 112 on both surfaces of the negative electrode current collectors 151 and 152, 141, and 142 are coated, and a plurality of battery cells having the separating films 131 and 132 interposed therebetween are stacked.

Insulating film members 161 and 162 are bonded to the outermost surfaces of the electrode assembly 100 by an adhesive to complete an electrode assembly.

4, a cathode active material 212 is coated on both surfaces of a cathode current collector 222 and an anode active material 241 is coated on both surfaces of an anode current collector 251 In the case of the electrode located at the outermost one of the electrodes, the positive electrode current collector 221 and the positive electrode current collector 221 are formed in a structure in which a plurality of battery cells with the separators 231 and 232 interposed therebetween are stacked. And a negative electrode active material 242 is coated on one surface of the negative electrode current collector 252. [

Insulating film members 261 and 262 are bonded to the surfaces of the positive electrode current collector 221 and the negative electrode current collector 252 located on the outermost surface of the electrode assembly 200 with an adhesive agent to complete the electrode assembly.

The electrode assemblies shown in FIGS. 2 and 3 have a structure in which an insulating material is added to an outermost surface of a stacked electrode assembly in which a plurality of positive electrodes and negative electrodes cut in a predetermined size unit are sequentially stacked with a separator interposed therebetween However, the structure and shape of the electrode assembly can be applied to various electrode assemblies.

Hereinafter, the present invention will be described in further detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

≪ Example 1 >

A cathode active material having the formula LiNi _0.5 Mn _1.5 O ₄ as a lithium manganese oxide having a spinel crystal structure containing Mn as an essential transition metal was prepared and mixed with 95 wt% of the cathode active material, 2.5 wt% of Super-P (conductive agent) And 2.5 wt% of PVdF (binder) were added to NMP (N-methyl-2-pyrrolidone) as a solvent to prepare a slurry. The slurry was coated on one surface of a 20 μm thick Al foil, Respectively.

Li _4/3 Ti _5/3 O ₄ was prepared by mixing titanium isopropoxide with lithium hydroxide and calcining at a high temperature to prepare 95% by weight of the prepared negative electrode active material, 2.5% by weight of Super-P (conductive agent) 2.5 wt% of PVdF (binder) was added to NMP to prepare a negative electrode mixture slurry. This was coated on one side of an Al foil having a thickness of 20 탆, dried and compressed to prepare a negative electrode.

An electrode assembly was prepared by laminating the positive electrode and the negative electrode using a Celgard ^TM membrane as a separator, and a polyamide tape having a thickness of 65 mu m was attached to the outermost surface of the electrode assembly as an insulating material. A lithium nonaqueous electrolyte solution containing 1M LiPF ₆ was added to prepare a battery.

≪ Comparative Example 1 &

In the production of the positive electrode and the negative electrode, and the manufacturing method of the battery, except that the insulating film member was not added to the outermost surface of the electrode assembly in the manufacturing process of the battery of Example 1, Respectively.

<Experimental Example 1>

The battery manufactured in Example 1 and Comparative Example 1 was subjected to a life characteristic test by flowing a current of 0.5 C-rate in a voltage range of 4.4 V to 5 V. The life characteristic was evaluated as a maintenance ratio with respect to the initial capacity after 50 cycles, 1 and Fig.

Example 1 Comparative Example 1 Life characteristics 97% 91%

According to Table 1 and FIG. 4, since the battery of Example 1 is an insulating material added to the outermost surface of the electrode assembly in the course of manufacturing the battery, the life characteristics of the battery are similar to those of the battery using the electrode assembly of Comparative Example 1 .

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 (20)

An electrode assembly in which a separator is interposed between an anode and a cathode is embedded in a case together with an electrolyte,
Each of the electrodes has a structure in which an electrode active material layer is coated on one side or both sides of the sheet-like current collector;
Wherein an insulating material is added to an outermost surface of the electrode assembly;
The secondary battery operates at a high voltage of 4.4 to 5 V;
The positive electrode includes a lithium manganese composite oxide having a spinel structure represented by the following formula (1) as a positive electrode active material;
Wherein the insulating material is a film-like member, and the adhesive is applied only to one surface of the electrode assembly, which is coupled to the outermost surface of the electrode assembly, and is bonded to the outermost surface of the electrode assembly by an adhesive bonding method. :
Li _{1 + x} M _y Mn _2-xy O ₄ (1)
Wherein 0? X? 0.3, 0? Y? 1,
M is at least one selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Or more. delete delete The secondary battery according to claim 1, wherein the negative electrode comprises lithium titanium oxide as a negative electrode active material. The secondary battery according to claim 1, wherein the insulating material is made of an electrically insulating polymer resin. The secondary battery according to claim 5, wherein the electrically insulating polymer resin is at least one selected from the group consisting of polypropylene, polyethylene terephthalate, and polyethylene. delete delete delete delete The electrode assembly according to claim 1, wherein an electrode assembly layer containing an electrode active material is applied to the surface of the collector on the outermost surface of the electrode assembly, and the insulating material is added to the outer surface of the electrode assembly layer battery. The secondary battery according to claim 1, wherein an insulating material is directly attached to the surface of the current collector at the outermost surface of the electrode assembly. The secondary battery according to claim 1, wherein an anode is disposed on an outermost surface of the electrode assembly. The secondary battery according to claim 1, wherein a cathode is disposed on an outermost surface of the electrode assembly. The secondary battery according to claim 1, wherein the electrode assembly is a folding structure, a stacking structure, or a stacking / folding structure. The secondary battery according to claim 1, wherein the battery case is a cylindrical or rectangular metal can. The secondary battery according to claim 1, wherein the battery case is a pouch-shaped case made of a laminate sheet including a metal layer and a resin layer. 18. The secondary battery according to claim 17, wherein the laminate sheet is an aluminum laminate sheet in which the metal layer is aluminum or an aluminum alloy. A device comprising a secondary battery according to any one of claims 1, 4 to 6, and 11 to 18 as a power source. 20. The device of claim 19, wherein the device is selected from a cell phone, a tablet computer, a notebook computer, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device.

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