KR100874384B1 - Laminate Sheet for Battery Case and Lithium Secondary Battery Containing the Same - Google Patents

Abstract

The present invention relates to a laminate sheet used in the manufacture of a battery case, comprising an outer coating layer based on excellent tensile strength and weather resistance polymer resin, a copper layer as a metal barrier layer, and an inner sealant layer based on a heat sealable polymer resin. It includes, and the surface of the copper layer facing the inner sealant layer provides a laminate sheet consisting of chemically and / or physically treated to form a plurality of irregularities and a lithium secondary battery using the same as a battery case .

The laminate sheet uses a copper layer as the metal barrier layer, thereby preventing corrosion caused by the connection between the metal barrier layer and the electrode terminal in an unexpected situation during assembly or use of the battery, thereby ultimately improving the life of the battery. Can extend and improve battery safety. Moreover, many fine unevenness | corrugations are formed in the surface of the copper layer facing the inner sealant layer, and it can ensure more excellent battery life by the outstanding adhesive force.

Description

Laminate Sheet for Battery Case and Lithium Secondary Battery Containing It {Laminate Sheet for Battery Case and Lithium Secondary Battery Employed with the Same}

1 is a schematic cross-sectional view of a laminate sheet for a typical battery case;

2 is a schematic cross-sectional view of a laminate sheet according to one embodiment of the present invention;

3 is a perspective view of a pouch type battery case formed of a laminate sheet according to the present invention;

4 is a schematic cross-sectional view of a laminate sheet according to another embodiment of the present invention.

<Description of Major Symbols in Drawing>

10, 100: laminate sheet

11, 110: outer coating layer

12, 120: metal barrier layer

13, 130: inner sealant layer

14, 140: adhesive layer

The present invention relates to a laminate sheet for a battery case and a lithium secondary battery comprising the same, and more particularly, an outer coating layer based on a polymer resin having excellent tensile strength and weather resistance, a metal barrier layer of a copper layer, and A laminate sheet comprising an inner sealant layer based on a heat sealable polymer resin, the surface of the copper layer facing the inner sealant layer being chemically and / or physically treated to form a plurality of irregularities; The present invention relates to a lithium secondary battery using the laminate sheet as a battery case. The laminate sheet according to the present invention includes a copper layer instead of aluminum as the metal barrier layer and fine irregularities are formed on the surface of the copper layer, thereby providing various advantages such as improving the life and safety of the battery.

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

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. A pouch type battery is a battery in which an electrode assembly having a cathode / separation membrane / cathode structure is built in a battery case in which a laminate sheet including a resin layer and a metal layer is formed in a pouch type.

1 schematically illustrates a cross-sectional structure of a laminate sheet generally used in a pouch-type battery.

Referring to FIG. 1, the laminate sheet 10 includes an outermost outer coating layer 11 forming an outermost layer, a barrier layer 12 that prevents penetration of a material, an adhesive layer 13, and an inner sealant layer 14 for sealing. Consists of.

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 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 barrier layer 12.

Various attempts have been made to further reduce thickness or increase barrier properties in the battery case sheet having the multilayer laminate structure.

For example, Japanese Patent Application Laid-Open No. 2004-0327039 forms an outer coating layer made of a biaxially stretched polyethylene terephthalate film or a biaxially stretched nylon film on a barrier layer made of aluminum. By further improving the strength and resistance, techniques have been proposed to reduce the overall thickness of the sheet.

Although not a sheet for a battery case, Japanese Patent Application Laid-Open No. 2004-0327039 is a packaging material for an electronic component case, wherein chitosans and Ti, Hf, Mo, W, Se, Ce, Fe, Cu, Zn, A technique of improving the gas barrier properties by forming a film with a background treatment agent containing a metal compound containing at least one metal selected from the group consisting of V and trivalent Cr is proposed.

As described above, all conventional laminate sheets used for battery cases or electronic component cases use aluminum layers as barrier layers. Aluminum has been preferred as a barrier layer material because of its low ductility and low ductility to enable gas barrier and thin film processing. However, the barrier layer of aluminum in the laminate sheet used for the battery case has a serious problem. The problem is described below.

Since the battery case serves to ensure stable operation by sealing the electrode assembly in an insulated state, the metal barrier layer of the laminate sheet of the battery case needs to be electrically insulated. On the other hand, in secondary batteries, nickel plates are frequently used in electrode leads as external input / output connection terminals of battery cells, electrical connection members for connecting battery cells and protection circuit modules (PCMs), and the like.

On the other hand, during the assembly or use of the battery, the metal barrier layer of the laminate sheet is unexpectedly placed in electrical connection with the electrode lead and the nickel plate as the connecting member. Since aluminum as a barrier layer has a large difference in electromotive force from nickel as an electrode lead and a connecting member, when the secondary battery is charged and discharged in the above electrical connection state, corrosion of aluminum proceeds. Therefore, damage to the barrier layer is caused, thereby rapidly shortening the life of the battery and greatly threatening the safety of the battery.

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. Therefore, even when the metal barrier layer of the battery case is electrically connected to the connection member or the like due to the unexpected development of the situation, there is a high demand for a technology capable of securing the life and stability of the battery.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After various experiments and in-depth studies, the inventors of the present application change the metal barrier layer from conventional aluminum to copper in a laminate sheet as a battery case and form fine irregularities on the surface of the copper layer. Corrosion can be fundamentally prevented and a high adhesion can be obtained, thereby ensuring that the life and stability of the battery can be improved, and the present invention has been completed.

The laminate sheet for a battery case according to the present invention includes an outer coating layer based on excellent tensile strength and weather resistance polymer resin, a copper layer as a metal barrier layer, and an inner sealant layer based on a heat sealable polymer resin, The surface of the copper layer facing the inner sealant layer is composed of chemically and / or physically treated so that a plurality of irregularities can be formed.

The laminate sheet for a battery case of the present invention includes a copper layer as a metal barrier layer, thereby fundamentally solving the corrosion problem due to electrical connection, which can greatly affect the life and safety of the battery as described above, and the inner sealant Many fine unevenness | corrugations are formed in the surface of the copper layer facing a layer, and it can ensure more excellent battery life by the outstanding adhesive force.

Specifically, copper, which is a material of the metal barrier layer, is also widely used as a material of a cathode in an electrode assembly, and a difference in electromotive force from a nickel plate used for a connection member or the like is relatively small compared to conventional aluminum. Therefore, even when the battery is electrically connected to the nickel plate due to unexpected situations, for example, through contact by a needle conductor, partial contact due to partial detachment of the outer coating layer, and the like, the difference in electromotive force at the time of charging and discharging the battery There is no corrosion problem.

In addition to preventing the inflow and leakage of foreign substances such as gas and moisture, the metal barrier layer also improves the strength of the battery case. In this respect, the copper layer exhibits properties comparable to those of conventional aluminum layers, and has excellent ductility. Therefore, it is also preferable to manufacture into a thin layer in the manufacture of a laminate sheet.

Moreover, the copper layer as a metal barrier layer has the advantage that it is favorable to high temperature performance and excellent in electrolyte resistance compared with an aluminum layer. Moreover, since copper has about 1.6 times higher electrical conductivity than aluminum, when using copper as a barrier layer, the specification of insulation resistance can be eliminated compared to when producing a laminate sheet using aluminum, thereby increasing productivity. great.

Since the outer coating 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 coating layer.

As the polymer resin of the inner sealant layer, a polyolefin-based resin having heat sealability (heat adhesion), low hygroscopicity to suppress the invasion of the electrolyte solution, and which is not expanded or eroded by the electrolyte solution is preferably used. And more preferably, an unstretched polypropylene film (CPP).

In one preferred embodiment, the laminate sheet according to the present invention, the outer coating layer has a thickness of 5 to 40 ㎛, the copper layer has a thickness of 20 to 150 ㎛, the thickness of the inner sealant layer is 10 to 50 ㎛ Can be. If the thicknesses are too thin, it is difficult to expect the blocking function and the strength improvement of the material, on the contrary, too thick is not preferable because of the poor workability and causing an increase in the thickness of the sheet.

In general, polyolefin resins such as polypropylene have low adhesion to metals. On the other hand, in the present invention, as described above, a large number of irregularities are formed on the surface of the copper layer by chemical and / or physical treatment, thereby solving the problem of low adhesion. Such irregularities can be formed, for example, by sand blasting, chemical etching, or the like on the surface of the copper layer, and can be expected to improve adhesion by securing a larger surface area. Although the size of the unevenness is not particularly limited, it is preferable that the size of the unevenness is 10 to 200 ㎛ to provide a high bonding force between the layers.

In another preferred embodiment, it may further include an adhesive layer between the copper layer and the inner sealant layer to improve the adhesion and blocking properties. Examples of the material of the adhesive layer include a urethane-based material, an acryl-based material, a composition containing a thermoplastic elastomer, and the like, but are not limited thereto.

The laminate sheet can be produced in a variety of ways. For example, films, metal foils, and the like constituting the respective layers may be sequentially laminated and then bonded to each other, and dry lamination or extrusion lamination methods may be used as such a bonding method. Can be. The dry lamination method is a method of bonding the two materials to each other by a temperature and pressure higher than room temperature using a heating roll after drying by interposing the adhesive between the one material and the other material. In addition, the extrusion lamination method is a method of interposing the two materials by a constant pressure at room temperature using a pressing roll after the adhesive is interposed between the one material and the other material.

The present invention also provides a case for a secondary battery manufactured using the laminate sheet as described above.

The battery case according to the present invention may have various forms, and preferably, may include a form in which the electrode assembly is formed in a pouch form. That is, a pouch-type battery case may be formed by forming an accommodating part in which an electrode assembly may be seated on one side of the laminate sheet by deep drawing and bending the other side in the form of a cover.

The present invention also provides a secondary battery including the battery case as described above.

Representative examples of the secondary battery include a lithium secondary battery, and among them, a lithium ion polymer secondary battery in which an electrode assembly is built in a pouch type case made of the laminate sheet and in which a lithium salt-containing electrolyte is impregnated in a gel form. desirable.

Since a more detailed structure of the lithium ion polymer battery, a method for manufacturing the same, and the like are known in the art, a detailed description thereof is omitted herein.

The lithium secondary battery according to the present invention may be preferably used as a unit cell of a medium and large battery pack, in particular due to the excellent life and safety of the battery case.

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

FIG. 2 is a schematic diagram of a cross-sectional structure of a laminate sheet according to one embodiment of the present invention, and FIG. 3 schematically illustrates one exemplary pouch case manufactured using such a laminate sheet.

Referring to these drawings, the laminate sheet 100 has a structure in which a copper layer 120 as a metal barrier layer is laminated between an outer coating layer 110 as an outermost layer and an inner sealant layer 130 that is heat sealable. . That is, the outer coating layer 110, the copper layer 120, and the inner sealant layer 130 are laminated in order from the outside.

Since the outer coating layer 110 forms an outer surface of the pouch case 200, tensile strength and weather resistance that can stably protect the electrode assembly (not shown) against the external environment are required, and polyethylene terephthalate (PET) or The outer coating layer 110 made of stretched nylon (Ony) can satisfy this requirement.

The copper layer 120 is a barrier layer for blocking gas, moisture, and the like containing air. The copper layer 120 is excellent in formability, and when the nickel plate (not shown) or the like of the electrode terminal of the battery cell is connected to the electromotive force with the nickel plate. It can prevent the corrosion caused by the car. In addition, fine concavities and convexities are formed on the surface of the copper layer 120 facing the inner sealant layer 130 to provide a high bonding force.

Since the inner sealant layer 130 forms the inside of the accommodating part 210 and the cover 220 in which the electrode assembly (not shown) may be mounted in the pouch case 200, resistance to the lithium-containing electrolyte is required. At the same time, the inner sealant layer 130 is thermally fused in contact with the inside of the lid 220 at the outer circumferential portion 230 of the housing 210. Therefore, the material of the sealant layer 130 is made of CPP (non-stretched polypropylene film) having both electrolyte resistance and heat sealability.

4 is a schematic view showing a cross-sectional structure of a laminate sheet according to another embodiment of the present invention.

Referring to FIG. 4, in the laminate sheet, a copper layer 120 as a barrier layer disposed between the outer coating layer 110 and the inner sealant layer 130 is laminated, and the copper layer 120 and the inner sealant layer 130 are laminated. The adhesive layer 140 is laminated between the layers and fine concavities and convexities are formed on the surface of the copper layer 120 facing the inner sealant layer 130. That is, the outer coating layer 110, the copper layer 120, the adhesive layer 140, and the inner sealant layer 130 are stacked in order from the outside. Due to the fine irregularities and the adhesive layer 140 formed on the surface of the copper layer 120, the copper layer 120 and the inner sealant layer 130 are stably bonded.

 Although the embodiments of the present invention have been described above with reference to the drawings, those skilled in the art 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 laminate sheet according to the present invention improves the formability of the sheet by using a copper layer as the metal barrier layer, and the metal barrier layer, the electrode terminal, and the like are unexpected in an unexpected situation during the assembly or use of the battery. Corrosion caused by the connection can be prevented, ultimately extending the life of the battery and improving the safety of the battery. Moreover, many fine unevenness | corrugations are formed in the surface of the copper layer facing the inner sealant layer, and it can ensure more excellent battery life by the outstanding adhesive force.

Claims (10)

A laminate sheet for use in the manufacture of a battery case, comprising: an outer coating layer based on polyethylene terephthalate (PET) or stretch nylon, a copper layer as a metal barrier layer, and an inner sealant layer based on a heat sealable polymer resin; And the surface of the copper layer facing the inner sealant layer is chemically or physically or chemically and physically treated so that a plurality of irregularities can be formed. 2. The laminate sheet according to claim 1, wherein the polymer resin of the outer coating layer comprises oriented nylon. The laminate sheet according to claim 1, wherein the polymer resin of the inner sealant layer comprises unstretched polypropylene. The laminate sheet according to claim 1, further comprising an adhesive layer between the copper layer and the inner sealant layer. The laminate sheet according to claim 1, wherein the outer coating layer has a thickness of 5 to 40 µm, the copper layer has a thickness of 20 to 150 µm, and the inner sealant layer has a thickness of 10 to 50 µm. A secondary battery case manufactured using the laminate sheet according to any one of claims 1 to 5. The secondary battery case according to claim 6, wherein the secondary battery case is formed in a pouch form by forming an accommodating part on which one side of the laminate sheet can be seated by deep drawing and bending the other side in the form of a cover. Lithium secondary battery comprising a battery case according to claim 6. The lithium secondary battery according to claim 8, wherein the secondary battery is a lithium ion polymer battery in which an electrode assembly is embedded in a pouch type case made of the laminate sheet, and the lithium salt-containing electrolyte is impregnated in a gel form. The lithium secondary battery of claim 8, wherein the secondary battery is used as a unit cell of a medium-large battery pack.

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