JP7001279B2 - Pouch-type secondary battery case with improved safety - Google Patents

Description

The present invention relates to a pouch-type secondary battery case, and more specifically, effectively removes water and HF (hydrogen fluoride) inside the secondary battery without being affected by a reaction product due to a reaction with an electrolyte, and externally. The present invention relates to a pouch-type secondary battery case that blocks the inflow of water from the battery.

As the lithium secondary battery, a pouch-type battery, which is thin, easily deformed in shape, low in manufacturing cost, and has a small weight, is widely used for mobile devices, electric vehicles, and the like. Lithium secondary batteries have a small amount of water in the active material or electrolyte, or in severe cases, water may flow in from the outside of the case. If such water is present, the potential energy of the charging process causes a gas to be generated by the reaction between the water and the electrolyte, and a swirling phenomenon occurs in which the battery cell expands. In particular, the LiPF ₆ lithium salt reacts with moisture to form HF, which is a strong acid, but the formed HF corrodes the metal foil (for example, aluminum foil) of the outer skin of the battery to form gaps. Moisture is induced to flow in, and the water that has flowed in reacts with the electrolyte to generate gas, causing the battery to swell. If the battery swells, this will reduce the life of the battery and, in severe cases, there is a risk of ignition. For this reason, it is obliged to remove the water and HF present inside the case.

In order to remove water and HF, Japanese Patent Application Laid-Open No. 2008-235256 presents an absorption sheet containing water and an HF absorbent substance. In particular, referring to FIGS. 12 and 13 of the same patent, a structure in which an absorbent sheet is inserted in the edge region of the case is adopted. However, in the same patent, the reaction product generated by the reaction of the water content of the absorbent sheet and the HF absorbent substance with the electrolyte causes a malfunction of the battery. Further, the electrolyte may permeate the side surface between the absorption sheet and the adhesive layer, and the bonded portion of the case may be separated. Furthermore, when the electrode structure inside the battery is wrapped with an absorbent sheet as in the patent, the thickness of the electrode structure is reduced by the amount corresponding to the thickness of the absorbent sheet, and the capacity of the battery is reduced. Performance will be reduced. When the absorbent sheet is further inserted into the portion where the lead tab is located, the height difference between the portion with the lead tab and the portion without the lead tab is large, so that the sealing may not be performed normally.

Japanese Unexamined Patent Publication No. 2008-235256

The problem to be solved by the present invention is that the reaction product produced by the reaction with the electrolyte keeps the case bonded without malfunction of the battery and affects the thickness of the electrode structure. It is an object of the present invention to provide a pouch-type secondary battery case having improved safety in blocking moisture existing inside the case and moisture flowing from the HF and the outside.

In the pouch-type secondary battery case with improved safety for achieving the object of the present invention, the upper and lower cases forming the case have a shape in which the layer structures are symmetrical to each other, and the layer structure is a storage area. And across the entire edge region, the layer structure consists of a first laminated layer, an absorbent layer and an outer skin laminated, and a second bonded layer between the absorbent layer and the outer skin. Alternatively, one of the adhesive layers or a layer in which they are combined is arranged, and the first bonding layer faces the electrode structure in the storage region and the bonding portion in the edge region. The absorbing layer has a layer structure containing either a water absorbing agent or a water absorbing agent / HF absorbing agent.

In the case of the present invention, the absorbing layer comprises a single layer or a laminate of a water absorbing layer containing the water absorbing agent, a lamination of the water absorbing layer and an HF absorbing layer containing the HF absorbing agent, the water absorbing agent and the HF absorbing agent. It has a layer structure selected from a single layer or a laminate of a composite absorption layer containing both, a laminate of the composite absorption layer and the water absorption layer, and a laminate of the composite absorption layer and the HF absorption layer. You may.

In a suitable case of the present invention, the water absorption layer, the composite absorption layer, or a layer in which they are combined may be laminated with layers having different water absorption rates. It is preferable that the water absorption rate on the storage area side is higher than the water absorption rate on the opposite side of the storage area. The content of the water-absorbing agent in the water-absorbing agent of the same material should be higher on the storage area side than on the opposite side of the storage area. The water absorption layer may be partitioned into regions having different water absorption rates.

In the case of the present invention, the first laminated layer may be made of any one of unstretched polypropylene (CPP), polypropylene (PP), polyethylene (PE) or a copolymer thereof. The first bonding layer includes an olefin oligomer containing a polar functional group, an ionomer resin, polyvinyl chloride (PVC), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), and polyvinyl acetate (PVAc). It may contain any one selected from the copolymers with polyvinyl alcohol (PVA) or a mixture thereof.

In a suitable case of the present invention, the adhesive layer absorbs at least one of moisture caused by the inside of the case, moisture flowing from the outside of the case, and HF caused by the inside of the case. At least one of the agent and the HF absorber may be dispersed. The metal foil constituting the outer skin may be provided with an HF corrosion prevention layer for preventing corrosion by HF.

According to the pouch-type secondary battery case with improved safety of the present invention, the reaction product produced by the reaction with the electrolyte is provided by providing a layer structure that absorbs water without directly contacting the electrolyte. Keeps the case stuck together without battery malfunction. It should be noted that the moisture existing inside the case and the moisture flowing from the HF and the outside are blocked without affecting the thickness of the electrode structure.

It is an exploded perspective view for demonstrating the pouch type secondary battery case by this invention. It is sectional drawing taken along the line II-II of FIG. It is a partial cross-sectional view which outlines the process which moisture and HF are absorbed in the case by this invention. It is sectional drawing which shows the example with respect to the absorption layer of the case of this invention. It is sectional drawing which shows the example with respect to the absorption layer of the case of this invention. It is sectional drawing which shows the example with respect to the absorption layer of the case of this invention. It is sectional drawing which shows the example with respect to the absorption layer of the case of this invention.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, the embodiments described below can be transformed into various different embodiments, and the scope of the present invention is not limited to the embodiments detailed below. Embodiments of the present invention are provided to more fully inform a person having ordinary knowledge in the art of the present invention. On the other hand, in the drawings, the thickness of the film (layer, pattern) and region may be exaggerated for clarity. When it is mentioned that the film (layer, pattern) is on one of the upper, upper, lower, and one surfaces of the other film (layer, pattern), it is directly formed on the other film (layer, pattern). Alternatively, other membranes (layers, patterns) may be interposed between them.

In the embodiment of the present invention, the case is provided with a layer structure that absorbs water without directly contacting the electrolyte, so that the reaction product produced by the reaction with the electrolyte does not cause a malfunction of the battery. Presenting a pouch-type secondary battery case that keeps the bonding and blocks the moisture existing inside the case and the moisture flowing from the HF and the outside without affecting the thickness of the electrode structure. For this purpose, a case having a layer structure capable of absorbing water and HF will be specifically described, and a process in which water and HF are absorbed by the layer structure will be described in detail. The process in which the reaction product due to the reaction with the electrolyte is not sprayed on the storage area will be described in detail. The water content of the battery reacts with the electrolyte to generate gas, which reacts with the LiPF ₆ lithium salt to produce HF. For this reason, it is preferable that the lithium secondary battery removes both water and HF.

FIG. 1 is an exploded perspective view for explaining a pouch-type secondary battery case according to an embodiment of the present invention. However, it does not represent a drawing in a strict sense, and for ease of explanation, there may be components (not shown).

According to FIG. 1, the pouch-type secondary battery 100 includes a case 10 including upper and lower cases 10a and 10b, and an electrode structure 20. The case 10 is divided into a storage area A that provides a space for storing the electrode structure 20, and an edge region B to which the upper and lower cases 10a and 10b are bonded. The detailed structure of the case 10 according to the embodiment of the present invention will be described in detail with reference to FIG. A plurality of electrode structures 20 are laminated with a positive electrode, a separator, and a negative electrode as one unit, and the electrode tabs 21 extending from the electrode structure 20 are bonded to the electrode leads 23 by welding, rivets, or the like. The electrode tab 21 is drawn out from the electrode structure 20 via the electrode lead 23 and connected to an external terminal.

The sealing portion 22 seals the electrode lead 23 so that the electrolyte and gas do not flow out through the electrode lead 23. The electrode lead 23 is generally plate-shaped or rod-shaped, and is made of a metal material having electrical conductivity. The electrode lead 23 may be formed of any one of a metal selected from aluminum (Al), nickel (Ni), copper (Cu) and an alloy thereof. The electrode lead 23 may be surface-treated with a chromium compound, a phosphorus compound, or the like in order to improve the adhesive force with the sealing portion 22 and prevent corrosion.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. Some parts have been omitted for ease of explanation.

According to FIG. 2, the upper and lower cases 10a and 10b forming the case 10 have a shape in which the layer structures are symmetrical to each other. The upper case 10a is formed by laminating a first bonding layer 30, an absorbing layer 31, a second bonding layer 32, an adhesive layer 33, an HF corrosion prevention layer 34, and an outer skin 35 in this order. The lower case 10b is formed by laminating the first bonding layer 30, the absorbing layer 31, the second bonding layer 32, the adhesive layer 33, the HF corrosion prevention layer 34, and the outer skin 35 in this order. At this time, each of the first bonding layer 30, the absorbing layer 31, the second bonding layer 32, the adhesive layer 33, the HF corrosion prevention layer 34, and the outer skin 35 of the upper case 10a is the first of the lower case 10b. It is the same as the bonding layer 30, the absorption layer 31, the second bonding layer 32, the adhesive layer 33, the HF corrosion prevention layer 34, and the outer skin 35.

The thickness of each of the first bonding layer 30, the absorbing layer 31, the second bonding layer 32, the adhesive layer 33, and the HF corrosion prevention layer 34 depends on the shape and application of the secondary battery to be manufactured. The present invention is not limited to this, but may be 0.1 to 50 μm, preferably 5 to 15 μm. At this time, since the absorbent layer 31 contains an absorbent substance, it may be relatively thicker than the other layers.

The first bonding layer 30, the absorbing layer 31, the second bonding layer 32, the adhesive layer 33, the HF corrosion prevention layer 34, and the outer skin 35 according to the embodiment of the present invention are laminated in a layer structure, and the case 10 It straddles the entire storage area A and edge area B of the above. The electrolyte filled in the storage area A comes into direct contact with the first laminating layer 30 and does not come into direct contact with the absorbing layer 31. This is because the absorption layer 31 is separated from the electrolyte by the first bonding layer 30. This prevents the reaction product produced by the reaction of the electrolyte with the water content of the absorption layer 31 and the HF absorbing substance from being sprayed on the storage region A. That is, even if the HF and moisture of the electrolyte permeate the first bonded layer 30 and react with the absorbent substance of the absorption layer 31, the reaction product is present in the absorption layer 31, so that the storage area It does not exist in A. Thereby, in the embodiment of the present invention, it is possible to block the malfunction of the battery caused by the reaction product being sprayed on the storage area A.

The outer skin 35 basically includes a protective layer and a metal foil. The protective layer plays a role of protecting the metal foil from the external environment, and is required to have excellent tensile strength and weather resistance as compared with the thickness. Polyester, stretched nylon film and the like are often used for the protective layer. The metal leaf is also called a barrier layer because it blocks the ingress and egress of moisture and air. Aluminum is mainly used as the metal foil, and aluminum has a blocking property against gas and the like and a softness that enables thin film processing, and is inexpensive. Needless to say, the materials of the protective layer and the metal leaf can be applied without limitation within the scope of the present invention. The outer skin 35 may be provided with various separate layers that exhibit functions such as insulation and peeling within the scope of the present invention.

The first bonding layer 30 of the upper and lower cases 10a and 10b faces the electrode structure 20 in the storage area A, and forms a bonding portion in the edge region B. The bonded portions are bonded to each other by a known method such as heat sealing and dry lamination. The first bonding layer 30 is not limited to this, but mainly a low melting point resin such as unstretched polypropylene (CPP), polypropylene (PP), or polyethylene (PE) is used. For example, the first bonded layer 30 may contain random polypropylene (PP), modified polyolefin (PO) and thermoplastic elastomer (elastomer). Here, the random polypropylene (PP) refers to a random copolymer or a random terpolymer, and a random terpolymer is preferably used. Random polypropylene (PP) may be a polypropylene-based resin having a melting index (g / 10 min) of 0.3 to 30 and a melting point of 145 ° C. or higher, preferably 150 ° C. or higher. Since the modified polyolefin has a polar group, it may be an acid-modified polyolefin having excellent adhesive sealing property. The acid-modified polyolefin is a polyolefin graft-modified with an acid such as maleic anhydride.

The typical molecular structure of the thermoplastic elastomer is a triblock copolymer, and in particular, the olefin-based thermoplastic elastomer is an olefin-based resin such as polyethylene or polypropylene and an olefin-based resin (for example: EDPM, ethylene propylene diene monomer). It is a substance bound with the main component. The polyolefin-based elastomer has polystyrene or polypropylene in the light phase, styrene-propylene rubber (EPR), or ethylene-propylene-diene rubber (EDPM) in the soft phase. The melting point of the olefin-based thermoplastic elastomer can be adjusted in a wide range of 50 to 120 ° C. depending on the content of the olefin-based resin.

The gel fraction of the thermoplastic elastomer is preferably 20 to 90%. If the gel fraction is less than 20%, the degree of cross-linking is insufficient and the amount of elastomer melted during heat fusion is too large. If the gel fraction exceeds 90%, the degree of cross-linking is too large and the adhesiveness deteriorates. The first laminated layer 30 of the present invention preferably contains random polypropylene and an elastomer in a ratio of 95: 5 to 50:50. If the content of the elastomer is lower than the above ratio, the elastic modulus of the first bonded layer 30 is lowered. When the content of the elastomer is higher than the above ratio, the amount of the resin flowing down during heat fusion becomes excessively large. The mixing ratio of the random polypropylene and the thermoplastic elastomer is more preferably 80:20 to 60:40.

Unlike the conventional laminating layer 30, the first laminating layer 30 does not insert an absorbent sheet, so that the process can be simplified as compared with the conventional one. Conventionally, a process of inserting an absorbent sheet has been separately required. For example, referring to FIGS. 12 and 13 of Japanese Patent Application Laid-Open No. 2008-235256, a process of arranging the absorption sheet in the case is necessary. However, in the present invention, the upper and lower cases 10a and 10b having the layer structure of the first bonding layer 30, the absorbing layer 31, the second bonding layer 32, the adhesive layer 33 and the outer skin 35 are heat-bonded to each other, etc. The process is simple because it is pasted together with. Such thermal adhesion is a general method applied even when the absorption layer 31 of the present invention is not present.

As is well known, the substance forming the first bonded layer 30 is a substance stable to the electrolyte. As a result, the first bonded layer 30 straddles the entire storage area A and the edge region B, but even if exposed to the electrolyte, the first bonded layer 30 is damaged by the electrolyte. do not have. When the first bonding layer 30 is bonded by heat bonding, dry lamination, or the like, it has sufficient bonding force to prevent the electrolyte from leaking to the outside of the case 10.

The absorption layer 31 is made of the same material as the first bonded layer 30, and is a layer for absorbing moisture inside and outside the case 10 and further absorbing HF. 3 to 7 will be described in detail. The second bonding layer 32 is made of a substance that can be bonded while protecting the absorption layer 31, and the material of the second bonding layer 32 is the same as that of the first bonding layer 30. In some cases, the second bonding layer 32 may not be provided as long as the absorption layer 31 is sufficiently protected. That is, the first bonding layer 30, the absorbing layer 31, and the second bonding layer 32 are made of the same material, except that the absorbing layer 31 absorbs moisture, HF, or both of them. The difference is that the agents are dispersed.

The adhesive layer 33 adheres the second bonding layer 32 and the outer skin 35 with an adhesive. At this time, the metal foil of the outer skin 35 may have an HF corrosion prevention layer 34 for preventing corrosion of the metal foil by HF. The adhesive is not limited in any way, but a hot melt type adhesive is preferably used. The adhesive layer 33 has an olefin oligomer (polymer) containing a polar functional group, an ionomer resin, and polyvinyl chloride in order to enhance the adhesive force of the outer skin 35 with the metal foil. (PVC), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), any one selected from a copolymer of polyvinyl acetate (PVAc) and polyvinyl alcohol (PVA), or a mixture thereof. It may be added. The olefin-based oligomer is a combination of atoms containing almost only carbon and hydrogen, and refers to a linear or branched polymer. The functional group contained in the olefin-based oligomer is covalently grafted to the olefin-based oligomer. Preferable examples of the functional group having polarity include an acid anhydride group, a hydroxyl group, a carboxyl group, an amide group, a urethane group, an imide group, a maleimide group, a thiol group and the like, and a particularly suitable example is an anhydrous maleine. Acid groups can be mentioned.

The ionomer resin is preferably an ethylene-based ionomer resin. The ethylene-based ionomer resin is a resin obtained by pseudo-crosslinking an ethylene copolymer such as an ethylene methacrylate copolymer or an ethylene acrylic acid copolymer with metal ions such as zinc ion, potassium ion, sodium ion, magnesium ion and lithium ion. Is. The ethylene-based ionomer resin also includes a resin obtained by mixing an ethylene copolymer having a carboxyl group in the molecule with a metal oxide, a metal hydroxide, or a metal salt. When an ethylene copolymer having a carboxyl group and a metal salt or the like are mixed, the carboxyl group is neutralized by the metal ion to become a carboxylic acid ion, and a salt with the metal ion is formed. By associating a plurality of carboxylic acid ions with metal ions, types such as ethylene copolymers are pseudo-crosslinked to form ionomer resins.

The adhesive layer 33 is a water-absorbing agent or a water-absorbing agent that indispensably absorbs the moisture generated inside the case 10 and the moisture flowing from the outside of the case, and selectively absorbs the HF caused by the inside of the case 10. Either one of the HF absorbers may be dispersed. The HF absorber can be used without limitation as long as it is known, and lithium carbonate, sodium carbonate, calcium hydroxide, activated charcoal, diatomaceous earth, pearlite, zeolite, hydrotalcite, calcined hydrotalcite and the like can be used. Examples include hydrotalcite oxide.

The water absorbing agent can be used without limitation as long as it is a known substance, and may be an inorganic substance, an organic substance, or a hybrid substance in which they are combined. Inorganic substances include activated carbon, zeolite, BaTIO ₃ , (HfO ₂ ) SrTiO ₃ , SiO ₂ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , and TIO ₂ . , Soda lime, lithium-silica, sulfate represented by the general formula MSO ₄ or M ₂ SO ₄ (M is any one of Na, K, Mg and Ca) and the like. Examples of the organic substance include an acrylate-based water-absorbing agent containing a copolymer grafted with acrylic acid or an acrylamide monomer, an ethylene maleic acid anhydride copolymer, carboxymethyl cellulose and polyethylene oxide. The hybrid substance is a substance in which the inorganic substance and the organic substance are hybridized by a nano-dispersion method or the like.

Since the adhesive layer 33 is for adhering to the metal foil of the outer skin 35, the adhesive layer 33 may be omitted as long as the second bonding layer 32 sufficiently exerts its function. In this case, the substance added to the adhesive layer 33 may be added to the second bonding layer 32 in order to enhance the adhesive force with the metal foil. Further, since the adhesive layer 33 is farther from the storage area A than the absorption layer 31, it may hardly contribute to the absorption of moisture (from the inside) and HF caused by the inside of the storage area A. be. As a result, the adhesive layer 33 may contain only a water absorbing agent for preventing absorption of water flowing from the outside of the case 10.

The HF corrosion protection layer 34 is a material or inert material having strong resistance to HF such as gold, silver or polyethylene, Teflon®, sodium, calcium, glass powder, nitrobenzene, aniline, acetanilide, amide, benzene chloride. The purpose is to protect the metal leaf of the outer skin 35 from HF by coating the outer skin layer with a material that can be transformed, and as long as the absorption layer 31 fully exerts its function, the HF corrosion prevention layer 34 is omitted. May be good.

FIG. 3 is a partial cross-sectional view illustrating the process by which water and HF are absorbed in the case according to the embodiment of the present invention. At this time, refer to FIGS. 1 and 2 for the case of the present invention.

According to FIG. 3, the absorption layer 31 contains the above-mentioned water absorbing agent, and may further contain the HF absorbing agent in some cases. In other words, the absorption layer 31 indispensably contains the water absorbing agent and selectively contains the HF absorbing agent. On the other hand, in case 10, a phenomenon occurs in which water or water / HF is absorbed or released due to a defect or a natural diffusion path. To give an example of a defect in the storage region A, the metal foil is deformed in the process of manufacturing the case 10, so that fine cracks occur in the metal foil. To give an example of a defect in the edge region B, a diffusion path may naturally occur in the bonded portion (region shown by the dotted line) between the first bonded layers 30. The water absorbing agent and the HF absorbing agent are collectively referred to as an absorbent substance P.

In the storage region A, the external moisture EW is diffused into the absorbing layer 31 and absorbed by the water absorbing agent of the absorbing substance P. Further, the internal moisture IW or moisture / HF [IW (F)] flowing through the first bonded layer 30 is diffused into the absorbing layer 31 and is a water absorbing agent or a water absorbing agent / HF absorbing agent of the absorbing substance P. Is absorbed by. In this case, even if the storage area A has defects (fine cracks, poor adhesion, diffusion furnace, etc.), the external moisture EW is prevented from penetrating into the electrode structure 20 of the storage area A. Although not shown, the adhesive layer 33 has a water absorbing agent that absorbs the external moisture EW, so that the permeation of the external moisture EW can be blocked more reliably. The internal moisture IW or moisture / HF [IW (F)] is absorbed by the absorption layer 31 and further by the adhesive layer 33, and the moisture IW or moisture / HF [IW (F) inside the storage region A is absorbed. )] Can be significantly reduced.

In the edge region B, the external moisture EW is diffused to the bonded portion, and when it reaches the storage region A, most of the external moisture EW is absorbed by the water absorbing agent of the absorbing layer 31. Specifically, the external moisture EW is absorbed to the maximum when it touches the bonded region, and the external moisture EW does not exist near the storage region A. The internal moisture IW or moisture / HF [IW (F)] flowing along the first bonded layer 30 is diffused into the absorbing layer 31 and absorbed by the water absorbing agent or the water absorbing agent / HF absorbing agent of the absorbing substance P. To. Thereby, the content of the water IW or the water / HF [IW (F)] inside the storage area A can be significantly reduced.

4 to 7 are cross-sectional views showing an example of the absorption layer 31 of the case 10 according to the embodiment of the present invention. Reference numerals 40, 41, 42 and 43 are attached to each case for ease of explanation. At this time, refer to FIGS. 1 and 2 for the pouch-type secondary battery 100. Here, in the first example, the layer containing only the water absorbing agent is shown as 31W, the layer containing only the HF absorbing agent is shown as 31F, and the layer containing only the water absorbing agent / HF absorbing agent is shown as 31WF.

According to FIG. 4, the first absorption layer 31a of the first case 40 spans the entire storage region A and the edge region B. In the first absorption layer 31a of the first case 40, the water absorption layer 31W containing the first water absorption agent and the water absorption layer 31W containing the second water absorption agent exist as a single layer or are laminated. be. In other words, the first absorption layer 31a of the first case 40 does not contain an HF absorber. Here, the single layer refers to either one of the water-absorbing layer 31W containing the first water-absorbing agent and the water-absorbing layer 31W containing the second water-absorbing agent. In the case of laminating, the water absorbing layer 31W containing the first water absorbing agent faces the electrode structure 20 of the storage region A and absorbs moisture from the inside of the case 10. The water absorbing layer 31W containing the second water absorbing agent absorbs water from the outside of the case 10. The first and second water-absorbing agents are the same as the above-mentioned water-absorbing agents.

The rate of absorbing water in the water absorbing layer 31W containing the first water absorbing agent is preferably higher than the rate of absorbing water in the water absorbing layer 31W containing the second water absorbing agent. Moisture may be contained in the electrode structure 20 during the manufacturing process of the secondary battery, and the moisture may flow into the electrode structure 20 during the storage process. Therefore, the water present in the storage area A should be promptly removed. There must be. As a result, the speed at which the water-absorbing layer 31W containing the first water-absorbing agent absorbs water can be increased, and the performance of the secondary battery can be maintained. On the other hand, the water flowing from the outside of the case 10 is gradually absorbed along the water absorbing layer 31W containing the second water absorbing agent, so that the rate of absorbing water may be relatively slow.

On the other hand, the water absorption rate in the water absorption layer 31W containing the first water absorption agent and the water absorption layer 31W containing the second water absorption agent is adjusted according to the content and type of the water absorption agent. For example, assuming that the water absorbing agents are made of the same material, if the content of the water absorbing agent is large, the water absorption rate is high. From the viewpoint of the content, the content of the water-absorbing agent in the water-absorbing layer 31W containing the first water-absorbing agent is larger than the content of the water-absorbing agent in the water-absorbing layer 31W containing the second water-absorbing agent.

The water absorption rate by the water-absorbing agent of the present invention is based on a technical idea considering the characteristics of the water-absorbing layer 31W containing the second water-absorbing agent. As a result, the difference in water absorption rate cannot be obtained through repeated experiments for water absorption without considering the technical idea. The difference in water absorption rate can be adjusted in consideration of the capacity of the pouch-type secondary battery according to the embodiment of the present invention, the type, size, shape of the electrolyte, the type of water absorbing agent, and the like.

According to FIG. 5, the second absorption layer 31b of the second case 41 spans the entire storage region A and the edge region B. The second absorbing layer 31b of the second case 41 is laminated with a water absorbing layer 31W containing only a water absorbing agent and an HF absorbing layer 31F containing only an HF absorbing agent. At this time, the number, thickness, and the like of the water absorption layer 31W and the HF absorption layer 31F are determined in consideration of the size of the secondary battery of the present invention and the characteristics of the electrolyte. At this time, the water absorbing agent and the HF absorbing agent are the same as those described above. The water absorption layer 31W may be designed so that the water absorption rate is different as described with reference to FIG.

According to FIG. 6, the third absorption layer 31c of the third case 42 spans the entire storage region A and the edge region B. In the third absorption layer 31c of the third case 42, the composite absorption layer 31WF that absorbs both water and HF exists as a single layer or is laminated. In other words, the third absorbing layer 31c of the third case 42 contains both a water absorbing agent and an HF absorbing agent. At this time, the water absorbing agent and the HF absorbing agent are the same as those described above. The water absorption layer 31W may be designed so that the water absorption rate is different as described with reference to FIG.

According to FIG. 7, in the fourth absorbing layer 31d of the fourth case 43, the water absorbing layer 31W containing a water absorbing agent and the HF absorbing layer 31F containing an HF absorbing agent are laminated on the edge region B, and the water absorbing layer 31W is laminated. Is partitioned into a first region a and a second region b having different water absorption rates. The first region a absorbs moisture from the outside of the case 10, and the second region b absorbs moisture from the inside of the case 10. For this reason, the first region a is located outside the case 10 with respect to the second region b. The water absorption in the first region a may be relatively slow, and the water absorption in the second region b may be relatively fast. A second region b of the edge region B extends to the storage region B to absorb moisture from the inside of the case 10.

The absorption layer 31 according to the embodiment of the present invention has a layer structure in which a water absorbing agent is essentially contained and an HF absorbing agent is selectively contained. Specifically, a single layer or laminate of the water absorption layer 31W, a laminate of the water absorption layer 31W and the HF absorption layer 31F, a single layer or laminate of the composite absorption layer 31WF, a laminate of the composite absorption layer 31WF and the water absorption layer 31W, and a composite absorption layer. It may be realized by laminating 31WF and HF absorption layer 31F. The water absorption rates of the water absorption layer 31W containing the water absorption agent and the composite absorption layer 31WF may be different from each other. Further, the area may be partitioned in the water absorption layer 31W so as to have different water absorption rates.

Although the present invention has been described in detail with reference to suitable embodiments, the present invention is not limited to the above embodiments and is within the scope of the technical idea of the present invention. It can be variously modified by a person who has ordinary knowledge.

10 Case 10a, 10b Upper and lower cases 20 Electrode structure 21 Electrode tab 22 Sealed part 23 Electrode lead 30 First bonded layer 31 Absorbing layer 31a, 31b, 31c, 31d First to fourth absorbing layer 31W Water absorbing layer 31F HF absorption layer 31WF composite absorption layer 32 second bonding layer 33 adhesive layer 34 HF corrosion prevention layer 35 outer skin a, b first and second regions

Claims (7)

The upper and lower cases forming the case have a shape in which the layer structures are symmetrical to each other, and the layer structure extends over the entire storage area and the edge area.
The layer structure is
The first laminating layer, the absorbent layer and the outer skin were laminated, and between the absorbent layer and the outer skin, either one of the second laminating layer or the adhesive layer or a combination thereof was combined. A layer is arranged, the first bonding layer faces the electrode structure in the storage region, forms a bonding portion in the edge region, and the absorbing layer is a water absorbing agent or a water absorbing agent. It has a layered structure containing a combination with an HF absorber, and the water-absorbing agent reacts with moisture.
The absorption layer includes a laminate of a water-absorbent layer containing the water-absorbent agent, a laminate of the water-absorbent layer and an HF-absorbent layer containing the HF absorber, and a laminate of a composite absorbent layer containing both the water-absorbent agent and the HF absorber. It has a layer structure selected from the laminate of the composite absorption layer and the water absorption layer and the laminate of the composite absorption layer and the HF absorption layer.
The water absorption layer, the composite absorption layer, or a layer in which they are combined contains the water absorption agent, and a plurality of layers having different water absorption rates are laminated.
The water absorption rate of the layer containing the water-absorbing agent on the side facing the electrode structure is higher than the water absorption rate of the layer containing the water-absorbing agent on the side where the outer skin is located, and is characterized by rapidly removing water. A pouch-type secondary battery case with improved safety. The pouch with improved safety according to claim 1, wherein the content of the water-absorbing agent in the water-absorbing agent of the same material is higher on the side facing the electrode structure than on the side on which the outer skin is located. Type secondary battery case. The pouch-type secondary battery case with improved safety according to claim 1, wherein the water absorption layer is partitioned into regions having different water absorption rates. The first aspect of claim 1, wherein the first laminated layer is made of any one of unstretched polypropylene (CPP), polypropylene (PP), polyethylene (PE) or a copolymer thereof. Pouch-type secondary battery case with improved safety. The adhesive layer comprises an olefin oligomer containing a polar functional group, an ionomer resin, polyvinyl chloride (PVC), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc) and polyvinyl alcohol. The pouch-type secondary battery case with improved safety according to claim 1, which comprises any one selected from a copolymer with (PVA) or a mixture thereof. The adhesive layer is a water-absorbing agent or an HF-absorbing agent that absorbs at least one of the moisture caused inside the case, the moisture flowing from the outside of the case, or the HF caused inside the case. The pouch-type secondary battery case with improved safety according to claim 1, wherein at least one of them is dispersed. The pouch-type secondary battery case with improved safety according to claim 1, wherein the metal foil constituting the outer skin is provided with an HF corrosion prevention layer for preventing corrosion due to HF.

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