KR101128664B1 - Secondary Battery of Improved Safety - Google Patents

Abstract

The present invention includes an upper case and a lower case made of a laminate sheet including a metal layer and a resin layer, wherein the upper case and / or the lower case is provided with an accommodating part for mounting an electrode assembly, and the upper case and the lower case. A plate-shaped secondary battery that is sealed by thermally sealing an outer circumferential surface thereof, and an exhaust induction sealing part capable of discharging the high pressure gas to the outside while the sealing is first released when a high pressure gas is generated inside the battery cell is formed on one side of the case. It is continuously formed to the end of the outer peripheral surface with a length corresponding to the width of the exhaust induction sealing provides a secondary battery, characterized in that less than the width of the outer peripheral sealing surface.

According to the present invention, when the battery is inflated due to the generation of high pressure gas in an abnormal operating state of the battery, the exhaust oil having a relatively short width of the sealing portion may also be effectively discharged through this while the sealing portion is opened earlier than other portions. It is possible to lower the battery internal pressure and prevent the battery from igniting and exploding.

Description

Secondary Battery of Improved Safety

The present invention relates to a secondary battery having improved safety, and more particularly, a plate-shaped secondary battery in which an accommodating part for mounting an electrode assembly is formed in an upper case and / or a lower case of a laminate sheet, and a sealing part is formed by thermal fusion. In the high pressure gas in the battery cell is released, while the seal is released preferentially, the exhaust induction sealing for discharging the high pressure gas to the outside is formed continuously to the end of the outer peripheral surface in a length corresponding to one side of the case, the exhaust induction The width of the sealing portion relates to a secondary battery, characterized in that smaller than the width of the outer peripheral sealing portion.

As the development and demand for mobile devices increases, the demand for secondary batteries as energy sources is increasing rapidly. Among them, many researches on lithium secondary batteries with high energy density and discharge voltage have been conducted and commercialized. It is widely used.

In general, a secondary battery is formed by injecting or impregnating an electrolyte solution after embedding an electrode assembly composed of a positive electrode, a negative electrode, and an insulating film interposed between the positive electrode and the negative electrode in a battery case of a metal can or laminate sheet in a stacked or wound state. It is.

One of the major research tasks in such secondary batteries is to improve safety. For example, secondary batteries may be subjected to high temperatures within the battery, which may be caused by abnormal operating conditions of the battery, such as internal short circuits, overcharge conditions exceeding the allowed currents and voltages, exposure to high temperatures, deformation due to drops or external shocks, and High pressure can cause the battery to explode. In particular, in the pouch type secondary battery, the sealing force of the battery case is lowered, which causes a problem of leakage of the electrolyte.

FIG. 1 is a schematic exploded perspective view of a general structure of a conventional representative pouch type secondary battery.

Referring to FIG. 1, the pouch type secondary battery 10 may include an electrode assembly 30, electrode tabs 40 and 50 extending from the electrode assembly 30, and electrodes welded to the electrode tabs 40 and 50. And a battery case 20 accommodating the leads 60 and 70 and the electrode assembly 30.

The electrode assembly 30 is a power generator in which a positive electrode and a negative electrode are sequentially stacked in a state where a separator is interposed therebetween, and has a stack type or a stack / fold type structure. The electrode tabs 40, 50 extend from each pole plate of the electrode assembly 30, and the electrode leads 60, 70 are welded, for example, with a plurality of electrode tabs 40, 50 extending from each pole plate. Each is electrically connected to each other, and part of the battery case 20 is exposed to the outside. In addition, an insulating film 80 is attached to a portion of the upper and lower surfaces of the electrode leads 60 and 70 in order to increase the sealing degree with the battery case 20 and to secure an electrical insulating 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.

The secondary battery 10 is manufactured by thermally fusion bonding the contact portions of the outer circumferential surface of the battery case 20 with the electrode assembly 30 mounted on the accommodating portion of the battery case 20.

When the secondary battery reaches an abnormal operating state such as internal short circuit, overcharge, high temperature exposure, the internal electrolyte is decomposed to generate high pressure gas. The generated high pressure gas may cause deformation of the battery case and shorten the life of the battery, and seriously may cause fire or explosion of the battery.

Therefore, various attempts have been made to prevent the ignition or explosion of the battery and to discharge the gas efficiently when such a high pressure gas is generated. For example, Japanese Patent Application Laid-Open No. 2005-116235 discloses a technique for forming a predetermined gas releasing mechanism in a battery that heat seals and seals the outer peripheral portion of a laminate film incorporating an electrode assembly.

2 is a perspective cross-sectional view of a battery case in which a gas discharge mechanism that is an unfused portion is formed in FIG. 2, and another example according to the above technique is illustrated in FIGS. 3 to 5. Side cross-sectional views of a battery case sealing portion in which a gas release mechanism is formed in a modified form of a seal layer are shown.

Referring to these drawings, as shown in FIG. 2, the technique forms a non-fused portion 11 in a part of the sealing portion during thermal fusion so that the stress of the internal gas is concentrated on the unfused portion 11. 3 to 5, in the laminate film composed of the outermost layer 41 / metal layer 42 / seal layer 43, the seal layer located at the innermost layer is deformed and pressed. The method (ii) which comprises the adhesive strength by heat welding lower than a site | part is disclosed. Examples of the method (ii) include a method of removing a portion of the seal layer 30 as shown in FIG. 3 or inserting a polymer resin 31 having a relatively low bonding force into the removed seal layer as shown in FIG. 4, and FIG. As in 5, a method of bonding the polymer resin 32 having a low bonding strength to a part of the seal layer or the like is proposed.

However, according to the experiments performed by the inventors of the present application, the technique has a weak adhesive strength of the sealing portion in which the gas discharge mechanism is formed, and thus, moisture penetration into the battery cell and leakage of the electrolyte solution continuously continue through the portion even under normal operating conditions. It was confirmed that there is a serious problem in the safety of the battery. Furthermore, in the case of the method (i), since the precision control for the formation of the unfused portion in the battery manufacturing process is not easy, and the stress caused by the internal gas is concentrated, the method (i) is not suitable for the internal gas pressure generated during the normal operation of the battery. As a result, as the unfused portion gradually expands, there is a problem in that the operation reliability is greatly decreased and the sealing property of the battery is lowered. In addition, in the case of the method (ii), the process of removing only a part of the laminate seal layer or inserting a separate resin itself requires a high level of precision, and therefore, there is a problem that it is difficult to be applied to the actual mass production process.

On the other hand, Japanese Patent No. 3,638,765 is a battery having a plate-shaped electrode assembly to the outer member and the outer peripheral portion of the outer member sealed by heat-sealing or adhesive layer, a material that is more thermally safe than the outer member on one side of the outer peripheral portion By sealing in the state which inserted the polymer resin sheet of the, the technique which comprises so that one side of the sealed part may have the withstand pressure performance compared with the other part is disclosed. In addition, Japanese Patent Application Laid-Open No. 2001-093489 discloses a battery in which an electrode assembly is embedded in a pouch type battery case of a laminate sheet, and at the same time, the positive and negative lead connected to the positive electrode plate and the negative electrode plate are drawn out from the sealing portion of the outer case. A technique of performing heat fusion in a state in which a heat-sealing resin sheet having a lower melting point than that of a laminate sheet is inserted in a part of a sealing portion of an exterior case is disclosed.

However, all of the above techniques have serious problems since the resin fragments to be inserted are exposed to the electrolyte solution inside the battery cell at the inner end of the sealing portion. The problem is described below.

As the electrolyte of the secondary battery, a non-aqueous liquid electrolyte, an organic solid electrolyte, an inorganic solid electrolyte, and the like are used. Such electrolytes are mostly strong in order to cause an electrochemical reaction with the active material applied to the positive electrode plate. The difference in the material between the case material of the battery cell itself and the polymer resin sheet to be inserted causes a difference in reactivity between the electrolyte with a strong polarity, which directly leads to a weakening of the sealing portion.

In addition, when the polymer resin of another material is inserted in the sealing portion to be heat-sealed, even if the heat-sealing process, a minute crack occurs in the junction between the different polymer resin, and the charge and discharge process repeatedly Due to such fine cracks in the process, the life of the battery may be shortened, and the problem may occur that the electrolyte may leak to the outside through the generated cracks.

In particular, the secondary battery used in the medium-large battery pack as a power source for electric vehicles, hybrid vehicles, etc. is required to ensure safety because of the long-term life required and a large number of battery cells are concentrated.

Therefore, by preventing the discharge of gas in the normal operating state of the battery, and by effectively discharging the high-pressure gas that can occur due to unexpected development of the situation, to prevent the ignition or explosion of the battery cell in advance, the life of the battery and There is a high need for a technology capable of securing stability.

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, an object of the present invention is to form an exhaust induction sealing portion having a width smaller than the width of the outer circumferential surface sealing portion to the end of the outer circumferential surface in a length corresponding to one side of the case, so that the sealing is preferred when generating high pressure gas inside the battery cell. By releasing the high pressure gas to the outside while being released, it is to provide a secondary battery that can secure the improved safety by preventing the risk of ignition or explosion of the battery in advance.

A secondary battery according to the present invention for achieving the above object includes an upper case and a lower case made of a laminate sheet including a metal layer and a resin layer, and the upper case and / or the lower case is accommodated for mounting an electrode assembly. It is formed as a plate-shaped secondary battery of the structure is sealed by forming a sealing portion by heat-sealing the outer peripheral surface of the upper case and the lower case,

When the high pressure gas is generated inside the battery cell, the seal is first released, and an exhaust induction sealing part capable of discharging the high pressure gas to the outside is continuously formed at an end portion of the outer circumferential surface with a length corresponding to one side of the case. The width is configured to be smaller than the width of the outer peripheral sealing portion.

According to the present invention, when the battery is inflated due to the generation of high pressure gas in an abnormal operating state of the battery, the exhaust oil having a relatively short width of the sealing portion may also be effectively discharged through this while the sealing portion is opened earlier than other portions. It is possible to lower the battery internal pressure and prevent the battery from igniting and exploding in advance.

In addition, as described above, in the prior art, the process of forming the gas discharge mechanism was very difficult and difficult to precisely control, but the exhaust induction sealing part according to the present invention may be formed in the manufacturing process of the battery case without an additional process. The process is very simple and the production efficiency of the battery is high. In addition, since the sealability of the sealing portion of the battery case is ensured, it is possible to prevent moisture infiltration and leakage of electrolyte due to external sealing or a small amount of gas generated in a normal state, such that the sealing portion is gradually released. So that the operation reliability is high.

In the present invention, the exhaust induction sealing portion is formed continuously to the end of the outer peripheral surface in a length corresponding to one side of the case as defined above.

Here, being continuously formed to the outer peripheral surface end of the case means that it is continuously formed from one end of the case to the other end. For example, when the length of the exhaust induction sealing part is equal to the length of the long side or the short side of the case, it may be continuously formed up to both ends of the case, except that the case is partially formed only in part of the battery case.

The outer circumferential surface sealing portion is formed at the upper end, the lower end, and both side end portions of the battery, and is formed on the x-axis and the y-axis on the horizontal cross-section of the battery, whereas the exhaust induction sealing portion is formed on the case so that the z-axis on the vertical cross-section of the battery. It is formed in. That is, the exhaust induction sealing portion is located on the gas movement path that moves upward to inflate the upper and lower surfaces of the battery case. Therefore, the high pressure gas inside the battery can be discharged more quickly and directly.

The method of forming the exhaust induction sealing part is not particularly limited, and may be made through various methods such as adhesive, crosslinking, and heat fusion. In addition, the exhaust induction sealing portion may be formed in the upper case, the lower case, or both.

In one preferred embodiment, the upper case or the lower case is composed of two units (first member, second member), the exhaust induction sealing portion is formed by heat-sealing the overlapping portion of the first member and the second member Can be. The formation of the exhaust induction sealing part may be performed at the time of manufacturing the upper case or the lower case.

In a specific example, the upper case is composed of a first member and a second member in a form in which the lower case of the unit member is cut in the short side direction, and the first and second members overlap each other, and the overlapping sides are The desired exhaust oil also extends to a length corresponding to the width of the sealing portion, and the exhaust oil induction sealing portion can be formed by thermally bonding the extended portions to each other.

The heat fusion process may be performed in a state in which the internal resin layers face each other at the extended portions of the first member and the second member. Since the exhaust induction sealing portion formed as described above is protruded to the upper portion of the lower case, it can be bent to contact the upper surface of the case in order to prevent the volume density of the battery increases, the case with an adhesive or the like to maintain the bent state It can also be attached to the top surface.

As defined above, the exhaust induction sealing part according to the present invention has a width smaller than the width of the outer circumferential surface sealing part.

Generally, in a plate-shaped secondary battery sealed by heat fusion, the gas generated in the battery pressurizes the heat fusion portion of the sealing portion, and when the gas pressure exceeds the bonding force of the sealing portion, the sealing portion is opened and discharged to the outside. do. Therefore, the site where the high pressure gas is discharged depends on the width length of the sealing portion.

Therefore, the shorter the width of the sealing portion is, the easier the gas is discharged. However, if the width of the sealing portion becomes too short, the sealing of the battery can be easily released even by external impact or low gas pressure that may be generated in a normal state, and thus the operation reliability of the safety device is lowered and the safety of the battery is reduced. There is a problem. On the other hand, if the width of the exhaust-induced sealing portion is too large, the degree of reduction of the gas discharge path is insignificant, and thus the desired opening effect can not be exerted when the high-pressure gas is generated inside the battery cell. In consideration of these points, it is preferable that the width of the exhaust induction sealing part is 30 to 80% of the width of the outer circumferential surface sealing part.

The position at which the exhaust induction sealing portion is formed is not particularly limited, and can be appropriately determined in consideration of, for example, a portion where the high pressure gas is concentrated inside the battery. In addition, in order to prevent harmful internal gas from being discharged indiscriminately, a predetermined exhaust member may be mounted on the battery cell itself or the pack case, and the exhaust oil induction sealing portion may be determined to communicate with the exhaust member.

However, since the electrode lead protrudes in the long side direction of the battery case, the sealing part may not be easily formed. Preferably, the exhaust induction sealing part may be formed in the short side direction of the battery case.

In addition, since the internal gas pressure generally acts to induce the largest deformation force in the center of the battery, the small gas pressure generated in the normal operation state of the battery is also concentrated in the center of the battery, and if the exhaust induction seal is formed in the center of the battery case, The sealing property may be released even by a small amount of internal gas. Therefore, the exhaust induction sealing portion is preferably formed at a portion adjacent to both ends of the battery case.

The battery case may be preferably applied to a laminate sheet including a resin layer and a metal layer, in particular, a secondary battery in which an electrode assembly is embedded in a pouch type case of an aluminum laminate sheet.

In one preferred embodiment, the battery case is composed of a laminate sheet comprising a resin outer layer of excellent durability, a barrier metal layer, and a heat-melting resin sealant layer, the resin sealant layer may be mutually heat-sealed.

Since the resin outer layer should have excellent resistance from the external environment, it is necessary to have a predetermined tensile strength and weather resistance. In such aspect, polyethylene terephthalate (PET) and a stretched nylon film may be preferably used as the polymer resin of the outer resin layer.

The barrier metal layer is preferably aluminum may be used to exhibit a function of improving the strength of the battery case in addition to the function of preventing the inflow or leakage of foreign substances such as gas, moisture.

The resin sealant layer has a heat sealability (heat adhesiveness), a low hygroscopicity to suppress the penetration of the electrolyte solution, a polyolefin resin that is not expanded or eroded by the electrolyte solution may be preferably used. Preferably unstretched polypropylene (CPP) can be used.

In one preferred example, the laminate sheet may have a thickness of the outer resin layer of 5 to 40 ㎛, a metal layer of 20 to 150 ㎛, the thickness of the inner resin layer of 10 to 100 ㎛. If the thicknesses are too thin, it is difficult to expect durability and blocking function and strength improvement of the material, and on the contrary, if the thicknesses are too thick, the workability is reduced and the thickness of the sheet is increased, which is not preferable.

In the present invention, the battery case made of the laminate sheet is composed of an upper case and a lower case, the upper case and / or lower case is provided with a receiving portion for mounting the electrode assembly. For example, the battery case may include a lower case in which an accommodating part is formed, and an upper case of a cover type for sealing an open top surface of the accommodating part.

When the battery case is heat-sealed to a portion corresponding to the outer circumferential surface of the housing while the upper member is positioned on the lower member, the resin sealant layers forming the innermost layers of the upper case and the lower case are melted while facing each other. Combine the upper case and the lower case.

The upper case and the lower case may be configured as an integrated type ('integral battery case') that shares one side with each other, or may be configured as a separate type ('removable battery case') each consisting of independent members.

The integrated battery case may be bent to form a sealing part by bending only one side shared by the upper case and the lower case, and sealing only the remaining three surfaces except for the bent portion. In addition, the removable battery case is composed of two independent members that will each constitute an upper surface and a lower surface, since the outer peripheral surfaces of each of the upper case and the lower case are both discontinuous, sealing is performed on all four surfaces by thermal fusion. To perform.

In the battery case according to the present invention, the sealing part may be formed on the three surfaces, or the sealing part may be formed on the four surfaces, and is not particularly limited. The electrode assembly is not particularly limited as long as it is a structure consisting of a cathode and an anode, and a separator interposed therebetween, and examples thereof include a folding type, a stack type, or a stack / folding type structure. Details of the electrode assembly of the stack / foldable structure are disclosed in Korean Patent Application Publication Nos. 2001-0082058, 2001-0082059, and 2001-0082060, which are described in the context of the present invention. Incorporated by reference.

The secondary battery according to the present invention may preferably be a lithium secondary battery, and in particular, may be preferably applied to a so-called lithium ion polymer battery in which a lithium-containing electrolyte is impregnated into the electrode assembly in the form of a gel.

The present invention also provides a medium-large battery module including the secondary battery as a unit cell.

In particular, the secondary battery according to the present invention may be preferably used in a high output large capacity battery requiring long life and excellent durability, or a medium and large battery module including a plurality of such batteries as a unit cell. The medium-large battery module may be used as a power source of, for example, an electric vehicle, a hybrid electric vehicle, an electric motorcycle, and an electric bicycle.

Since the structure and manufacturing method of such a medium-large battery module are well known in the art, a detailed description thereof will be omitted herein.

Hereinafter, although described with reference to the drawings according to an embodiment of the present invention, this is for easier understanding of the present invention, the scope of the present invention is not limited thereto.

6 is a perspective view schematically illustrating a secondary battery having a structure in which an exhaust induction sealing part is formed according to one embodiment of the present invention.

Referring to FIG. 6, the secondary battery 100 includes an electrode assembly (not shown), a lower case 300 accommodating the same, an upper case 200 covering an open top surface of the lower case 300, and an electrode assembly. It comprises two electrode leads (500, 501) electrically connected to the electrode tabs of the.

The two electrode leads 500 and 501 are electrically connected to electrode tabs (not shown) extending from each electrode plate of the electrode assembly by welding or the like, and part of the electrode leads 500 and 501 are exposed to the outside. In addition, an insulating film (not shown) is attached to upper and lower portions of the electrode leads 500 and 501 in order to increase the sealing force with the battery cases 200 and 300 and to secure an electrical insulation state. The two electrode leads 500 and 501 of the positive and negative electrodes may be formed at positions facing each other, as shown in this figure, or may be positioned side by side in the same direction.

The battery cases 200 and 300 are made of an aluminum laminate sheet, and the outer peripheral surface of the housing part of the lower case 300 and the outer peripheral surface of the upper case 200 are coupled by heat fusion to form an accommodating part for accommodating the electrode assembly. As a result, the outer circumferential surface sealing portion 400 having a predetermined width D is formed while being sealed, and has a pouch shape as a whole. The outer circumferential surface sealing portion is formed on the horizontal cross sections (x, y) of the case 300. The upper case 200 is composed of two unit members, the first member 210 and the second member 220. The lower end of the first member 210 and the upper end of the second member 220 are thermally fused to each other at a predetermined width d to form the exhaust induction sealing part 410. As a result, the exhaust induction sealing part 410 is formed parallel to the short side of the upper case 200 and is continuously formed from the left edge part to the right edge part, and is located adjacent to the outer peripheral surface side of the upper end part.

A more specific form of the exhaust induction sealing part 410 is shown in FIG. 7, which is an enlarged schematic diagram of the portion A of FIG.

Referring to FIG. 7 together with FIG. 6, the upper case 200 and the lower case 300 are made of a laminate including a resin outer layer 100a, a barrier metal layer 100b, and a heat-melt resin sealant layer 100c. have. At the ends of each of the first member 210 and the second member 220 of the upper case 200, the resin sealant layer 100c is heat-sealed and bonded in a state facing the predetermined length d, and the exhaust induction sealing part is combined. 410 is formed. The outer circumferential surface sealing part 400 is formed by heat-sealing the outer circumferential surface of the lower case 300 and the outer circumferential surface of the upper case 200 in a state where the first member 210 and the second member 220 are coupled to each other.

The exhaust induction sealing part 410 is formed in the horizontal cross-sectional direction z of the case 300, so that the high pressure gas moving in the up and down directions can be quickly discharged. However, since the gas pressure is mainly concentrated in the center part of the upper case 200, when the exhaust induction sealing part 410 is formed in the center part, the sealing property of the sealing part 410 may be released even by the low internal pressure in the normal state of the battery. In some embodiments, the drawing may be located at a portion of the upper case 200 that is slightly biased, but the present invention is not limited thereto. Meanwhile, since the exhaust induction sealing part 410 protrudes to the upper part of the upper case 200, the exhaust induction sealing part 410 is bent so as to contact the upper surface of the upper case 200 (see the blue arrow in FIG. 7) to increase the volume density of the battery. It can prevent the increase.

In addition, the exhaust induction sealing part 410 has a width d shorter than the width D of the outer circumferential surface sealing part 400, and preferably 30 to 80 with respect to the width D of the outer circumferential surface sealing part 400. About%. Therefore, the gas discharge path is shortened so that the internal gas of the battery is first released from the exhaust induction sealing part 200 and the sealing is released (separated), thereby discharging the gas.

Although the present invention has been described above based on the drawings according to the embodiment of the present invention, the exhaust-induced sealing part will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, the secondary battery according to the present invention has an exhaust induction sealing portion in addition to the outer circumferential surface sealing portion, so that when the high-pressure gas is generated in the abnormal operating state of the battery and the battery swells, a relatively short exhaust gas of the sealing portion is exhausted. Since the induction sealing part is opened earlier than other parts, gas can be effectively discharged through this, thereby lowering the battery internal pressure and preventing ignition and explosion of the battery in advance.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

1 is an exploded perspective view of a general structure of a conventional pouch type secondary battery; 2 is a perspective sectional view of a battery case in which a gas release mechanism that is an unfused portion is formed, in one example according to the conventional method;

3 to 5 are side cross-sectional views of another case according to the related art, in the case of a battery case sealing portion in which a gas release mechanism is modified in a seal layer;

6 is a perspective view of a secondary battery in which an exhaust induction sealing part is formed according to one embodiment of the present invention;

FIG. 7 is an enlarged view of a portion A in FIG. 6.

Claims (12)

An upper case and a lower case made of a laminate sheet including a metal layer and a resin layer, the upper case and / or lower case is provided with a receiving portion for mounting the electrode assembly, the outer peripheral surface of the upper case and the lower case A plate-shaped secondary battery having a structure of sealing by heat-sealing to form a sealing portion, When the high pressure gas is generated inside the battery cell is first released, the exhaust induction sealing portion for discharging the high pressure gas to the outside is formed continuously to the end of the outer peripheral surface in a length corresponding to one side of the upper case or the lower case, A width of the exhaust induction sealing portion is smaller than the width of the outer peripheral surface sealing portion. The method of claim 1, wherein the upper case or the lower case is composed of two units (the first member, the second member), the exhaust induction sealing portion by heat-sealing the overlapping portion of the first member and the second member Secondary battery, characterized in that formed when manufacturing the case or the lower case. The secondary battery of claim 1, wherein the exhaust induction sealing part is bent to contact an outer surface of the battery case. The secondary battery of claim 1, wherein a width of the exhaust induction sealing part is 30 to 80% of a width of the outer peripheral sealing part. The secondary battery of claim 1, wherein the exhaust induction sealing part is formed in a short side direction of the battery case. The secondary battery of claim 5, wherein the exhaust induction sealing part is formed at a portion adjacent to an outer circumferential surface of the battery case. The secondary battery according to claim 1, wherein the battery case is formed of a laminate sheet including a durable resin outer layer, a barrier metal layer, and a heat-melt resin sealant layer, and the resin sealant layers are thermally fused to each other. . The secondary battery of claim 7, wherein the resin outer layer is made of stretched nylon or polyethylene terephthalate, the barrier metal layer is made of aluminum, and the resin sealant layer is made of unstretched polypropylene. The secondary battery according to claim 1, wherein the battery case has sealing portions formed on three or four surfaces by heat fusion of four outer peripheral surfaces thereof. The secondary battery of claim 1, wherein the electrode assembly is a folding type, a stacking type, or a stacking / folding type structure. The secondary battery of claim 1, wherein the battery is a lithium ion polymer battery. A medium-large battery module comprising the secondary battery according to any one of claims 1 to 11 as a unit cell.

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