KR20130005886A - Battery case of high durability and secondary battery including the same - Google Patents

Abstract

PURPOSE: A battery case is provided to prevent moisture absorption from outside and dielectric breakdown, to improve durability and to provide excellent stability and structural stability. CONSTITUTION: A battery case of a laminate sheet(100) for a secondary battery comprises: an inner skin layer(130) which can be thermally fused when heating and pressurizing; a first shielding layer(120) preventing the penetration of the material spread on the upper part of the inner skin layer; a first polymer layer(110) which is spread on the first shielding layer and is not melted at the thermosetting temperature of the inner skin layer; a second shielding layer(160) which is spread on the polymer layer, prevent the penetration of materials and has the thickness of 50% or less of the first shielding layer; a second polymer layer(150) spread on the second shielding layer and is not melt at the thermosetting temperature of the inner skin layer.

Description

Battery case of excellent durability and secondary battery comprising the same {Battery Case of High Durability and Secondary Battery Including the Same}

The present invention relates to a high-strength battery case and a secondary battery including the same, and more particularly, to a laminate battery case of a laminate sheet that seals an electrode assembly and an electrolyte by thermal fusion, and an inner coating layer that is thermally fused upon heating and pressing. A first barrier layer applied on top of the inner coating layer and preventing the permeation of material, a first polymer layer applied on the first barrier layer and not molten at the heat fusion temperature of the inner coating layer, on the polymer layer A second barrier layer applied and preventing permeation of the material and having a thickness of 50% or less of the first barrier layer, and a second polymer applied on the second barrier layer and not melted at the heat fusion temperature of the inner coating layer It relates to a secondary battery case comprising a layer and a secondary battery comprising the same.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing. Many researches have been conducted on lithium secondary batteries with high energy density and discharge voltage among such secondary batteries. .

Lithium secondary batteries are largely classified into cylindrical batteries, square batteries, pouch-type batteries, and the like according to their appearance, and may be classified into lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, and the like depending on the type of electrolyte.

Due to the recent trend toward the miniaturization of mobile devices, there is an increasing demand for thinner rectangular batteries and pouch-type batteries. In particular, for pouch-type batteries that are easy to deform, low in manufacturing cost and light in weight. Interest is high.

Generally, a pouch type battery refers to a battery in which an electrode assembly and an electrolyte are sealed inside a pouch type case of a laminate sheet including a resin layer and a metal layer.

The pouch-type secondary battery forms an accommodating part for mounting an electrode assembly on a laminate sheet, and heat-seazes a separate sheet which is separated from the sheet or a sheet extending therefrom while the electrode assembly is mounted on the accommodating part. It is made by doing.

Referring to FIG. 1, the laminate sheet 10 includes an outermost outer coating layer 11 forming an outermost layer, a metal barrier layer 12 which prevents penetration of a material, an adhesive layer 13, and an inner sealant layer 14 for sealing. Consists of. In some cases, the adhesive layer 13 may not be included.

Since the outer coating layer 11 serves to protect the battery from the outside, excellent tensile strength and weather resistance to the thickness are required, and ONy (stretched nylon film) is frequently used. The metal barrier layer 12 serves to prevent air, moisture, and the like from flowing into the battery, and mainly aluminum (Al) is used.

The inner sealant layer 14 is thermally fused to each other by an applied heat and pressure in a state in which the electrode assembly is embedded, and serves to provide a sealability, and mainly consists of CPP (non-stretched polypropylene film). The adhesive layer 13 serves to complement the low adhesion of the CPP inner sealant layer 14 to the metal barrier layer 12.

Referring to FIG. 2, the battery case 20 is integrated with a main body and a main body in which an accommodating part 21 for mounting an electrode assembly (not shown) is formed, and can seal the accommodating part 21. It consists of a cover 22 of the form.

Accordingly, in the pouch type secondary battery, the electrode assembly is mounted on the accommodating portion 21 of the battery case 20, and then bent at the connection portion between the main body 23 and the lid 22 to seal the accommodating portion 21. In order to manufacture the heat-sealing the sealing part 3 and the lid 22 of the main body 23, except for the bent portion.

At this time, when the resin sealant layers corresponding to the innermost layer apply heat to the sealing portions of the main body and the cover, the main body and the cover are joined and sealed by fusion while the resin sealant layer is melted.

However, during the manufacturing process of the battery, in the deep drawing process for forming the electrode assembly accommodating portion in the battery case or the heat fusion sealing process for forming the battery case outer peripheral surface sealing portion, by applying excessive excessive strain force or excessive heat fusion locally The metal barrier layer may be exposed while the outer coating layer and / or the inner sealant layer are partially destroyed.

Specifically, free radicals may be generated in the resin sealant layer constituting the battery case by the high temperature heat applied in the heat fusion process. Accordingly, deterioration such as oxidation of the resin sealant layer or generation of fine cracks may occur.

In this case, since the sealing property of the battery is lowered, there is a problem that the electrolyte may leak to the outside or the external moisture may penetrate into the battery. If the exposed aluminum layer comes into contact with the electrolyte or the electrode tab for the same reason, the insulation resistance It is destroyed.

At this time, aluminum as the barrier layer has a large difference in electromotive force from the electrode lead and nickel as the connecting member. Therefore, when the secondary battery is charged and discharged in the electrical connection state as described above, corrosion of aluminum proceeds.

In addition, when charging and discharging is performed in the energized state, as shown in FIG. 3, aluminum is oxidized to form a lithium aluminum alloy, and the aluminum alloy is eluted with an electrolyte solution to form fine pores in the aluminum barrier layer.

As a result, moisture introduced through the outer coating layer having no moisture barrier property is introduced into the battery case through fine cracks formed in the aluminum layer, resulting in swelling of the battery, and as a result, the safety of the lithium secondary battery and penetration into the battery. Alternatively, adverse effects such as swelling of the battery, deterioration of life characteristics, deterioration of long-term storage characteristics, and reduction of insulation resistance may occur due to diffused moisture or the like.

Therefore, there is a high need for a technology capable of fundamentally preventing the above-described problem of deterioration of battery performance and securing battery stability.

In particular, a secondary battery used in a medium-large battery pack as a power source of an electric vehicle, a hybrid vehicle, etc. needs a long lifespan, and it is very important to secure safety due to the fact that many battery cells are concentrated.

In addition, when the battery case can exhibit high mechanical rigidity by itself, the battery can exhibit excellent resistance against needle penetration and the like, and can exhibit excellent structural stability when constructing a medium-large battery pack using a plurality of batteries.

One method of providing the above-mentioned mechanical rigidity to the battery case is to configure the thickness of the battery case thickly from the same material, but in this case, the weight of the battery and the assembly characteristics of the battery are deteriorated, which is not preferable.

Therefore, there is a high demand for a battery case that can satisfy both the above safety and stability.

The present invention aims to solve the problems of the prior art and the technical problem that has been requested from the past.

Applicants of the present invention include two or more blocking layers to prevent the transmission of the material and when they produce a laminate sheet of a composite blocking layer structure in a configuration that satisfies the conditions, while minimizing the exposure of the barrier layer to ensure safety In spite of the thin thickness, it was confirmed that excellent mechanical properties can be obtained and the present invention was completed.

Therefore, the secondary battery case according to the present invention is a laminate battery case of a laminate sheet for sealing the electrode assembly and the electrolyte by thermal fusion,

An inner coating layer that is thermally fused upon heating and pressing;

A first blocking layer applied on the inner coating layer and preventing permeation of materials;

A first polymer layer applied on the first barrier layer and not melted at the heat fusion temperature of the inner coating layer;

A second barrier layer applied on the polymer layer and preventing permeation of material and having a thickness of 50% or less of the first barrier layer; And

A second polymer layer applied on the second barrier layer and not melted at the heat fusion temperature of the inner coating layer; .

Since the battery case according to the present invention includes a composite blocking layer of the first blocking layer and the second blocking layer having a thickness of 50% or less of the first blocking layer, the inner coating layer may be damaged by heat fusion during the manufacturing process. Even when the first blocking layer directly reacts with the electrolyte, inhalation of moisture from the outside, breakdown of insulation resistance, and the like can be prevented, thereby exhibiting improved durability. That is, even when the first blocking layer is damaged, the second blocking layer does not lose the barriness by blocking the inflow of moisture from the outside.

Moreover, the two blocking layers are configured to satisfy different conditions, so that despite the thin thickness, excellent mechanical properties can be exerted, so that not only safety but also structural stability are excellent.

The inner coating layer is not particularly limited as long as it is a material that can be mutually heat-sealed when heated and pressurized, for example, at least one selected from the group consisting of polyethylene, unstretched polypropylene, polyurethane, and polyimide. Can be done.

In addition, the first blocking layer and the second blocking layer, preferably, may be made of aluminum or aluminum alloy independently of each other. In one preferred embodiment, the first blocking layer is made of aluminum, the second blocking layer may be made of aluminum alloy.

The aluminum alloy can be obtained by adding alloying elements such as Mg, Cu, Si, and Zu to aluminum. Since the aluminum alloy has a higher strength than pure aluminum, the second barrier layer may be made of a high strength aluminum alloy, thereby providing high mechanical rigidity despite a thickness thinner than that of the first barrier layer.

The aluminum alloy includes AlCuMg-based alloys, AlMg-based alloys, AlSi-based alloys, AlMg-based alloys, and the like, wherein at least one of the aluminum alloys selected from the group consisting of alloy number 8097, 1N30, 8021, 3003 and 3005 It is preferable.

In another preferred embodiment, the thickness of the second blocking layer may be 20 to 50% of the thickness of the first blocking layer. If the thickness of the second blocking layer is less than 20% of the thickness of the first blocking layer, the desired mechanical stiffness cannot be secured against external force, and if the thickness of the second blocking layer is greater than 50%, it is not preferable because it is contrary to the trend of miniaturization of the battery.

Specifically, the thickness of the first blocking layer may be 15 μm to 160 μm, in which case the thickness of the second blocking layer may be at least 3 μm to 32 μm and at most 7.5 μm to 80 μm.

On the other hand, the first polymer layer and the second polymer layer, for example, may be made of one or more selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate and stretched nylon independently of each other.

In one preferred embodiment, the thickness of the second polymer layer may be 50 to 150% of the thickness of the first polymer layer. When the thickness of the second polymer layer is less than 50% of the thickness of the first polymer layer, it is difficult to expect the penetration resistance and excellent mechanical rigidity of the needle member, etc. On the contrary, when the thickness of the second polymer layer is greater than 150%, the thickness is difficult due to the increase in thickness. Not.

Since the battery case of the composite blocking layer structure according to the present invention is not limited to a double blocking layer structure, the third blocking layer and the third polymer layer may be further sequentially applied on the second polymer layer. Of course, this structure can be extended to the fourth blocking layer and the fourth polymer layer. In the above structure, the additional blocking layers are preferably configured to satisfy at least the conditions of the second blocking layer.

On the other hand, as a result of using the battery case of the composite blocking layer structure according to the present invention, when bending is difficult in the manufacturing process of the pouch-type battery, the thickness of the second blocking layer of the bent portion of the battery case, the thickness of the second polymer layer The thickness of the second blocking layer of the case cover portion and the thickness of the second polymer layer may be selectively thinner.

In addition, the present invention provides a secondary battery in which an electrode assembly having a structure of a cathode / separation membrane / cathode is accommodated in an accommodating portion of the battery case and is impregnated with an electrolyte and sealed.

In this case, the electrode assembly accommodated in the battery case includes a jelly-roll type (winding type), stacked type (stacked type), or a composite type (stack / folding type) structure, the secondary battery is preferably a lithium secondary battery. .

The positive electrode may be prepared by applying a slurry prepared by mixing a positive electrode mixture including a positive electrode active material and a conductive material, a binder, a filler, and the like to a solvent such as NMP on a positive electrode current collector, followed by drying and rolling.

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

The 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 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 whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

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 inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

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 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 active material may be, for example, carbon such as hardly graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1 - x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x &lt; Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, Bi ₂ O ₅ and the like; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The negative electrode collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and examples thereof 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 electrolyte is preferably a lithium salt-containing non-aqueous electrolyte consisting of an electrolyte and a lithium salt. As the electrolyte, a non-aqueous 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.

As the inorganic solid electrolyte, for example, 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, sulfates, and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may 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), FEC (fluoro-ethylene carbonate), and the like.

The secondary battery according to the present invention can be used not only in a battery cell used as a power source for a small device but also as a unit cell in a middle or large battery module including a plurality of battery cells.

Accordingly, the present invention provides a battery pack using the battery module as a unit module, and the battery pack may be used as a power source for an electric vehicle, a hybrid electric vehicle, an electric bicycle, an electric motorcycle, but is not limited thereto.

The manufacturing method of the laminate sheet, the structure of the pouch-type secondary battery, the medium-large battery module and the battery pack and the manufacturing method are well known in the art, detailed description thereof will be omitted herein.

Since the battery case according to the present invention includes a composite blocking layer of a first blocking layer and a second blocking layer having a thickness of 50% or less of the first blocking layer, the inner coating layer may be damaged by heat fusion during the manufacturing process. Even when the first blocking layer directly reacts with the electrolyte solution, it is possible to prevent the intake of moisture from the outside and the destruction of the insulation resistance, thereby exhibiting improved durability and providing excellent safety and structural stability despite the thin thickness. .

Therefore, the secondary battery manufactured using the battery case according to the present invention has an effect of improving the battery performance, such as life characteristics, long-term storage characteristics.

1 is a schematic cross-sectional view of a laminate sheet for a typical battery case;
2 is a schematic view of a typical pouch type battery case;
3 is a schematic diagram of a process in which fine air bubbles are formed in the aluminum barrier layer when the secondary battery is charged and discharged while the aluminum of the barrier layer is exposed and energized with the battery;
4 is a schematic cross-sectional view of a battery case according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

4 is a schematic diagram of a cross-sectional structure of a battery case according to an embodiment of the present invention.

Referring to these drawings, the laminated sheet 100 constituting the battery case is the adhesive layer 140, the inner coating layer 130, the first blocking layer 120, the first polymer layer 110, the second blocking layer from the inside 160 and the second polymer layer 150 are stacked in this order.

Referring to FIG. 1, since the first polymer layer 110 forms the outer surface of the battery case, tensile strength and weather resistance that can stably protect the electrode assembly against the external environment are required, and polyethylene terephthalate (PET) is required. Or an outer covering layer 11 made of stretched nylon (Ony).

The first blocking layer 120 corresponds to a barrier layer 12 which is a layer for blocking gas, moisture, and the like including air, and the inner coating layer 130 forms the inside of the accommodating part and the cover in the pouch case. Corresponds to the internal silane layer 13 for which resistance is required.

The second blocking layer 160 is stacked on the first polymer layer 110, and the second blocking layer 160 has a thinner thickness than the first blocking layer 120. When the first blocking layer 120 is made of pure aluminum, the second blocking layer 160 may be made of an aluminum alloy having a higher strength than that of pure aluminum.

The second polymer layer 150 is stacked on the second blocking layer 160, and the second polymer layer 150 is formed thicker than the first polymer layer 110. In this case, the second blocking layer has a thickness thinner than that of the first blocking layer.

Although described with reference to the drawings according to an embodiment of the present invention, those of ordinary skill in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (14)

A secondary battery case of a laminate sheet for sealing an electrode assembly and an electrolyte by thermal fusion,
An inner coating layer that is thermally fused upon heating and pressing;
A first blocking layer applied on the inner coating layer and preventing permeation of materials;
A first polymer layer applied on the first barrier layer and not melted at the heat fusion temperature of the inner coating layer;
A second barrier layer applied on the polymer layer and preventing permeation of material and having a thickness of 50% or less of the first barrier layer; And
A second polymer layer applied on the second barrier layer and not melted at the heat fusion temperature of the inner coating layer;
Secondary battery case comprising a. According to claim 1, wherein the inner coating layer is a secondary battery case, characterized in that made of one or more selected from the group consisting of polyethylene, unstretched polypropylene, polyurethane and polyimide. The case for a secondary battery of claim 1, wherein the first blocking layer and the second blocking layer are made of aluminum or an aluminum alloy independently from each other. The case of claim 1, wherein the first blocking layer is made of aluminum, and the second blocking layer is made of aluminum alloy. The case of claim 3, wherein the aluminum alloy is at least one selected from the group consisting of alloy numbers 8097, 1N30, 8021, 3003, and 3005. The case of claim 1, wherein the thickness of the second blocking layer is 20 to 50% of the thickness of the first blocking layer. The secondary battery case of claim 1, wherein the first blocking layer has a thickness of 15 μm to 160 μm. The case of claim 1, wherein the first polymer layer and the second polymer layer are each independently formed of at least one selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate, and stretched nylon. According to claim 1, wherein the thickness of the second polymer layer is a secondary battery case, characterized in that 50 to 150% of the thickness of the first polymer layer. The case for a secondary battery of claim 1, wherein a third blocking layer and a third polymer layer are sequentially further applied on the second polymer layer. A secondary battery, wherein the electrode assembly and the electrolyte are sealed in the secondary battery case according to any one of claims 1 to 10. 12. The secondary battery according to claim 11, wherein the secondary battery is a lithium secondary battery. A battery pack comprising the secondary battery according to claim 11. The battery pack according to claim 13, wherein the battery pack is used as a power source for an electric vehicle, a hybrid electric vehicle, an electric bicycle, and an electric motorcycle.

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