KR20080112653A - Case for secondary battery having improved safety and lithium secondary battery containing the same - Google Patents

Abstract

A case for a secondary battery having improved safety is provided to minimize side reaction within a battery and to improve the high temperature safety of a secondary battery by removing effectively an HF harmful to the battery capacity. A case for a secondary battery is formed with a receiving part corresponding to the shape of an electrode assembly(300) and is equipped with polymer sheets(410,420) containing an HF adsorber to be interposed between the exterior surface of the electrode assembly and inner surface of the case.

Description

Case for Secondary Battery Having Improved Safety and Lithium Secondary Battery Containing the Same}

1 is an exploded perspective view of a general structure of a conventional pouch type secondary battery; 2 is an exploded perspective view of a secondary battery according to a first embodiment of the present invention;

3 is a perspective view of a secondary battery according to FIG. 2;

4 and 5 are cross-sectional views taken along line A-A 'of FIG. 3, FIG. 4 is a structure in which a polymer sheet including an HF adsorbent is inserted into an upper surface and an inner surface of the battery case, and FIG. 5 is a battery case. The polymer sheet containing the HF adsorbent is inserted into the inner side of the structure;

6 is an exploded perspective view of a rechargeable battery according to a second exemplary embodiment of the present invention.

The present invention provides a secondary battery case having improved safety, and includes an accommodating part corresponding to a shape of an electrode assembly, and a polymer sheet including an HF adsorbent is added to be interposed between an outer surface of the electrode assembly and an inner surface of the case. It relates to a case for a secondary battery consisting of a.

Lithium secondary batteries are classified into cylindrical batteries, square batteries, and pouch-type batteries according to their appearance. Due to the recent trend toward miniaturization of mobile devices, the demand for thinner square batteries and pouch-type batteries increases. In particular, there is a high interest in a pouch-type battery which is easy to deform in shape, low in manufacturing cost, and low in weight.

In general, a pouch type secondary battery is electrically connected to positive and negative electrode tabs protruding from the electrode assembly in a state in which an electrode assembly composed of a positive electrode, a negative electrode, and a separator disposed therebetween is mounted inside the pouch type battery case. Two electrode leads are formed in a sealed structure so as to be exposed to the outside from one side of the battery case.

Specifically, FIG. 1 schematically shows a general structure of a conventional representative pouch type secondary battery as an exploded perspective view.

Referring to FIG. 1, the pouch type secondary battery 10 may include an electrode assembly 30, electrode tabs 32 and 34 extending from the electrode assembly 30, and electrodes welded to the electrode tabs 32 and 34. And a battery case 20 accommodating the leads 40 and 41 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 32, 34 extend from each pole plate of the electrode assembly 30, and the electrode leads 40, 41 are welded, for example, with a plurality of electrode tabs 32, 34 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 50 is attached to a portion of the upper and lower surfaces of the electrode leads 40 and 41 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 pouch-type battery case of such a structure is easily damaged when pressed by a physical shock or a pointed object, causing a problem of fire or explosion. Therefore, in order to solve this problem, for example, techniques that increase the thickness of the sheet or use an outer case made of a material having excellent mechanical rigidity or the like are generally used. However, such an increase in case thickness or the use of certain materials has problems such as increasing the volume of the battery and complicating the manufacturing process.

Furthermore, when the pouch type secondary battery is used as a unit cell of a medium-large battery pack as a power source for an electric vehicle or a hybrid battery vehicle, leakage of electrolyte is caused when the battery case is damaged due to a constant external shock or an unexpected situation. This may occur, and it is very important to secure safety due to the fact that a plurality of battery cells are concentrated.

Therefore, there is a high need for a technology that not only improves the mechanical stability of the pouch-type battery but also protects the battery from physical shock to secure safety.

On the other hand, in general, a small amount of moisture in the battery manufacturing process, etc. may be included in the battery, particularly in the case of the pouch-type case is very likely to penetrate through the sealing portion and the like. When water is present in the battery due to various causes, reaction products such as HF are generated by the reaction with the battery components. This HF destroys the SEI layer and causes dissolution of the anode, which occurs more prominently at high temperatures, which can cause serious problems in the safety of the cell.

In this regard, some prior arts disclose techniques for incorporating certain HF sorbents into a cell. For example, Japanese Patent Application Laid-Open No. 1999-283671 discloses Mg _x Al _y O _z (x≥0, y≥0, x + y = 1, z> in a positive electrode mixture in a secondary battery containing LiF ₆ . Disclosed is a technique for a secondary battery characterized by adding 0), and Korean Patent Application Laid-Open No. 2001-0068650 discloses a hydrogen fluoride (HF) gas in which at least one of an electrode, a separator, and an electrolyte is derived from a fluorine-containing compound. Disclosed is a technique related to a lithium secondary battery, which comprises an inorganic base capable of capturing.

However, the techniques are to include a predetermined inorganic material in the form of an additive in the electrode, the separator and the electrolyte solution, when the inorganic additives are present in a large amount in the site directly affecting the operation of the battery, greatly reduces the lithium ion mobility As a result, the conductivity may be reduced, thereby degrading the cell performance and causing various side reactions in the cell.

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.

Specifically, an object of the present invention is to minimize the amount of impact by absorbing the physical shock applied to the battery case by adding a polymer sheet containing an HF adsorbent so as to be interposed between the inner surface of the electrode assembly to be mounted on the housing and the inner surface of the case. In addition, by adsorbing HF that may be generated due to the moisture present in the battery to provide a secondary battery case with improved high temperature safety.

Accordingly, the secondary battery case according to the present invention is a secondary battery case in which an accommodating part corresponding to a shape of an electrode assembly is formed, and a polymer sheet including an HF adsorbent so as to be interposed between an outer surface of the electrode assembly and an inner surface of the case. Is configured to be added.

The polymer sheet interposed between the electrode assembly and the case during the assembly of the secondary battery is not directly located at the operating region of the battery during charging and discharging, so that the electrode assembly is effectively absorbed by the external shock without causing performance degradation of the battery. The amount of impact applied to can be minimized. As a result, the polymer sheet improves the physical and mechanical safety of the battery.

In addition, the polymer sheet contains an HF adsorbent, and effectively removes HF gas, thereby preventing many problems such as destruction of the SEI film, electrolyte decomposition, and increased internal pressure of the battery. It can greatly improve performance.

The polymer sheet, as defined above, is added between the inner surface of the battery case and the outer surface of the electrode assembly, for example, the upper surface of the inner surface, the lower surface of the inner surface, except for the outer peripheral portion (sealing portion) for sealing the battery case, or It may be added to all or part of the inner surface.

In one preferred example, the polymer sheet may be located at the top of the inner surface and / or the bottom of the inner surface of the battery case. Here, the inner top and bottom of the inner surface of the battery case means an inner surface of the battery case facing the upper and lower surfaces, respectively, the widest outer surface portion of the plate-shaped electrode assembly. Therefore, when the electrode assembly is mounted to the accommodating part of the battery case in the assembling process of the secondary battery, the polymer sheet may be easily added to the upper and lower surfaces of the electrode assembly so that the electrode assembly may be located at the corresponding site.

On the other hand, the battery case generally forms a housing in which the electrode assembly can be mounted by a deep-drawing method. At this time, since a bend is formed in the housing, a predetermined surplus space is formed between the electrode assembly and the battery case. That is, since a surplus space exists between the side of the electrode assembly and the inner surface of the battery case, when the polymer sheet is added to the inner surface of the battery case, the battery capacity is reduced compared to the same standard by utilizing the surplus space. Can be minimized.

The polymer sheet may be simply inserted into a corresponding portion between the battery case and the electrode assembly during the assembly of the secondary battery or may be attached to the corresponding portion of the battery case. In the latter case, a non-reactive adhesive that does not affect the operation of the battery can be used to adhere the polymer sheet or by thermal fusion or the like.

In the case where the polymer sheet is attached to at least a part of the inner surface of the case, the polymer sheet is attached onto the sheet for manufacturing the battery case, and then a housing portion having a shape corresponding to the electrode assembly is formed, or after the polymer sheet is formed on the inner surface of the battery case. I can attach it.

The non-reactive adhesive means an adhesive which does not cause side reactions with an electrolyte or an electrode active material, and may be, for example, a silicone polymer adhesive or a carbon fiber polymer adhesive.

The polymer sheet is made of a material having electrolyte resistance, and serves to absorb external impact due to the properties of the material itself or the shape of the sheet. For example, the polymer sheet may be polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyethylene-terephthalate (PET), polymethyacrylate (PMMA), or polyacrylonitrile (PAN). It consists of one or two or more materials selected from the group consisting of hydrophobic polymers such as, and consists of various forms such as film, woven fabric, nonwoven fabric. Preferably it is in the form of a non-woven fabric or kraft paper more excellent shock absorption, more preferably may be a non-woven fabric made of PP polymer.

The thickness of the polymer sheet may be appropriately determined in consideration of the volume of the battery compartment and the size of the electrode assembly. However, when the thickness of the polymer sheet is too thin, it is difficult to exert a desired shock absorbing effect, and on the contrary, when the thickness of the polymer sheet is too thick, there is a problem that the battery capacity is relatively decreased. And more preferably 10 μm to 0.5 mm.

In the present invention, the polymer sheet, as defined above, contains an HF adsorbent. Therefore, many problems that may occur when HF is present in the battery can be solved, which will be described in more detail below.

For example, if it contains LiPF ₆ lithium salt in the electrolyte, LiPF ₆ is Li ⁺ and PF ₆ ^- should be present in ionic form, but, and the intention is side reactions arose unstable PF ₅ is produced as a by-product unlike, It reacts with H ₂ O present in traces in the electrolyte to form HF. HF destroys the SEI layer and causes dissolution of the anode, which occurs more significantly at high temperatures. In particular, HF decomposes the organic solvent components of the electrolyte to generate a large amount of gas, thereby increasing the internal pressure of the battery, thereby causing the battery to explode. Depending on the type of lithium salt used as an electrolyte, materials such as HF, HCl, HBr, and HI may be generated in addition to HF, and thus may act as HF as an acid.

As a method for solving this problem, a method of directly adding an HF adsorbent or the like into a battery may be considered. However, when such an additive is directly added into an electrolyte solution or an electrode assembly as described above, the mobility of lithium ions may decrease, and As a result, the capacity of the battery is reduced, and various side reactions may occur due to direct contact with the electrode material.

On the other hand, in the case of including the HF adsorbent by the method such as supporting or coating on the polymer sheet as in the present invention, it is possible to effectively remove the HF while minimizing the occurrence of side reactions inside the battery, thereby exhibiting excellent battery performance have. That is, by adsorbing HF present in the battery itself, the HF adsorbent can prevent unintentional side reactions such as decomposition of the electrode active material or electrolyte, thereby preventing battery performance, life characteristics, and battery deterioration.

The HF adsorbent is a substance that does not react with the electrolyte and the electrode active material and does not deteriorate the performance of the battery. A known HF adsorbent capable of adsorbing HF first may be used. For example, it may be a material having superior chemical bonding or affinity with HF molecules compared to HF molecules and electrolyte, and preferably, potassium carbonate, lithium carbonate, sodium carbonate, activated carbon, calcium hydroxide, diatomaceous earth, perite and zeolite It may be one or two or more selected from the group consisting of (Zeolite), but is not limited thereto.

The content of the HF adsorbent is preferably contained in 0.01 to 50% by weight based on the total weight of the polymer sheet. If the content of the HF adsorbent is too small, it is difficult to expect the desired effect of HF absorption, on the contrary, if the content of the HF adsorbent is too high, the amount of the HF adsorbent added directly to the electrolyte due to an increase in the amount eluted into the electrolyte without binding to the polymer sheet. The same problem occurs, and it is not preferable in terms of battery capacity and light weight.

The method in which the HF adsorbent is included in the polymer sheet is not particularly limited. For example, the HF adsorbent is supported in the polymer sheet by immersing the polymer sheet in a solution in which the HF adsorbent is dispersed, or flow coating. It may be coated on the surface of the polymer sheet by various methods such as spin coating, dip coating, bar coating, bar coating, etc., and vaporized HF adsorbent and deposited on the surface of the polymer sheet. You can also do it.

In order to increase the binding strength of the HF adsorbent to the polymer sheet in the coating process, a predetermined binding aid may be added. The binding aid is not particularly limited unless it causes a chemical reaction in the battery. Fluorine-based polymers such as PVdF and PTFE, PVdF-based copolymer polymers, PMMA, PAN, PEO, and SBR.

In some cases, the polymer sheet may further include a moisture adsorbent, or a part of the polymer sheet or a separate polymer sheet may include a moisture adsorbent instead of the HF adsorbent. For example, the polymer sheet including the HF adsorbent and the moisture adsorbent at the same time may be included by being added to the inner surface of the battery case. Alternatively, one surface of the battery case may be added by adding a polymer sheet containing an HF adsorbent, and the other surface is added by adding a polymer sheet containing a moisture absorbent. As a result, not only the acid such as HF can be removed, but also its occurrence can be prevented fundamentally.

The moisture adsorbent does not react with the electrolyte and the electrode active material and does not deteriorate the performance of the battery. Preferably, the activated carbon, zeolite, alumina, silica gel, and molecular It may be one or two or more selected from the group consisting of Molecular Sieve, magnesia (MgO) and titanium dioxide (titania: TiO ₂ ), but is not limited thereto.

The battery case may be formed from a laminate sheet including an outer coating layer of a polymer film, a barrier layer of metal foil, and an inner sealant layer of a polyolefin series. Since the outer coating layer must have excellent resistance from the external environment, it is necessary to have a tensile strength and weather resistance of at least a predetermined level. In such aspect, a stretched nylon film or polyethylene terephthalate (PET) may be preferably used as the polymer resin of the outer resin layer. The barrier layer may preferably use aluminum to exert a function of improving the strength of the battery case in addition to a function of preventing inflow or leakage of foreign substances such as gas and moisture. The inner sealant layer has a heat sealability (heat adhesion), low hygroscopicity to suppress the penetration of the electrolyte solution, polyolefin resin that is not expanded or eroded by the electrolyte solution may be preferably used. Preferably, unstretched polypropylene (cPP) can be used.

The accommodating part may be formed in a size corresponding to the electrode assembly on one side of the battery case, or may be formed on both sides of the battery case.

The present invention also provides a secondary battery including the battery case. The secondary battery is not particularly limited. Preferably, the secondary battery may be a so-called lithium ion polymer battery in which a lithium electrolyte is impregnated into the electrode assembly in the form of a gel.

In addition, the battery according to the present invention may be a pouch-type battery in which an electrode assembly is embedded in a pouch-type case of a laminate sheet, particularly an aluminum laminate sheet, in particular, a metal layer and a resin layer.

The secondary battery has a structure in which an electrolyte solution is impregnated into an electrode assembly having a separator interposed between a positive electrode and a negative electrode.

For example, the positive electrode may be manufactured by coating and drying a positive electrode active material on a positive electrode current collector, and may further include a binder and a conductive material and, as necessary, components described above with respect to the structure of the positive electrode.

The positive electrode current collector is generally made to a thickness of 3 to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver, or the like can be used. In addition, the positive electrode current collector may increase the adhesion of the positive electrode active material by forming fine unevenness on its surface, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

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

The negative electrode is manufactured by coating, drying, and compressing a negative electrode material including a negative electrode active material and a binder on a current collector, and optionally, components such as a conductive material and a filler may be further included.

The negative electrode material may be, for example, carbon such as hardly graphitized carbon or graphite carbon; Li _x Fe ₂ O ₃ (0 ≦ _x ≦ 1), Li _x WO ₂ (0 ≦ _x ≦ 1), Sn _x Me _{1 - x} Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me' Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 <x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , and metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The current collector for the cathode is generally made of a thickness of 3 to 500 ㎛. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like, aluminum-cadmium alloy, and the like can be used. As in the current collector, the current collector may form fine irregularities on its surface to increase the adhesion of the negative electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, and the like. Do.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), cellulose, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose Rhodes, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers, polymer toughened poly Rivinyl alcohol etc. are mentioned.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. Specific examples of commercially available conductive materials include Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, Ketjenblack and EC, which are acetylene black series. Family (Armak Company), Vulcan XC-72 (manufactured by Cabot Company) and Super (manufactured by Super P, Timcal).

In some cases, a filler may optionally be added as a component that inhibits the expansion of the electrode. Such a filler is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials, such as glass fiber and carbon fiber, are used.

In addition, other components, such as viscosity modifiers, adhesion promoters, and the like may optionally be further included or in combination of two or more.

The viscosity modifier is a component for adjusting the viscosity of the electrode mixture so that the mixing process of the electrode mixture and the coating process on the current collector thereof can be easily added, up to 30% by weight based on the total weight of the electrode mixture. Examples of such viscosity modifiers include, but are not limited to, carboxymethyl cellulose, polyvinylidene fluoride, and the like. In some cases, the solvent described above can serve as a viscosity modifier.

The adhesion promoter is an auxiliary component added to improve the adhesion of the active material to the current collector, it may be added in less than 10% by weight compared to the binder, for example, oxalic acid (oxalic acid), adipic acid (adipic acid), Formic acid, acrylic acid derivatives, itaconic acid derivatives, and the like.

The binder, the conductive material and the filler added as necessary are the same as those described for the positive electrode.

The separator is interposed between the anode and the cathode, an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally from 0.01 to 10 ㎛ ㎛, thickness is generally 5 ~ 300 ㎛. As such a separator, for example, a sheet, a nonwoven fabric, or the like made of an olefin polymer such as polypropylene having chemical resistance and hydrophobicity, glass fiber or polyethylene, or the like is used.

In some cases, a gel polymer electrolyte may be coated on the separator to increase battery stability. Representative of such gel polymers are polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile and the like. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

The lithium salt-containing non-aqueous electrolyte is composed of an organic solvent electrolyte and a lithium salt.

As said electrolyte solution, N-methyl- 2-pyrrolidinone, a propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, Gamma-butylo lactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolon, 4 -Methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolon, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxolon derivatives Aprotic organic solvents such as sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrionate and ethyl propionate can be used. have.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyedgetion lysine, polyester sulfides, polyvinyl alcohols, polyvinylidene fluorides, Polymerizers containing ionic dissociating groups and the like can be used.

As the inorganic solid electrolyte, for example, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides, sulfates, and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may be used.

The lithium salt is a good material to be dissolved in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, Lithium phenyl borate, imide and the like can be used.

In addition, in the electrolyte solution, for the purpose of improving the charge and discharge characteristics, flame retardancy, etc., for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitro Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride and the like may be added. . In some cases, in order to impart nonflammability, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics.

The secondary battery according to the present invention is preferably combined with a plurality of unit cells can be used in the medium-large battery module of high output large capacity. Since high power large-capacity medium-large battery modules are frequently subjected to external forces such as vibration and external shock, excellent mechanical strength is required for external forces, and in the structure of the battery cell constituting the battery pack, the amount of loading of the electrode active material to the current collector is large. Therefore, the high temperature life characteristics may act as an important factor in order to exhibit the predetermined operating characteristics.

The present invention also includes the steps of: (i) adding a polymer sheet containing an HF adsorbent to all or a portion of the inner surface of the battery case formed with a housing corresponding to the shape of the electrode assembly; (ii) inserting an electrode assembly into the battery case to which the polymer sheet is added; And (iii) optionally adding a polymer sheet containing an HF adsorbent to the top surface of the electrode assembly.

Accordingly, by adding a separator sheet between the inner surface of the battery case and the outer surface of the electrode assembly in a simple and easy manner, even when an external impact is applied, the shock can be absorbed or mitigated. It is possible to effectively remove HF, which may be generated by moisture, to improve high temperature safety and battery performance.

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.

2 is an exploded perspective view of a rechargeable battery according to a first exemplary embodiment of the present invention, FIG. 3 is a perspective view of the rechargeable battery according to FIG. 2, and FIGS. Cross-sectional views of lines A-A 'are respectively shown.

Referring to these drawings, the pouch type secondary battery 100 accommodates the electrode assembly 300, the electrode lead 310 welded to the electrode tabs extending from the electrode assembly 300, and the electrode assembly 300. It is configured to include a battery case 200 formed with a receiving portion, and the polymer sheet (410, 420) containing the HF adsorbent.

The electrode assembly 300 is a power generator in which an anode and a cathode are sequentially stacked in a state where a separator is interposed therebetween, and has an folding type, a stacked type, or a stack / folding type structure. The electrode tabs extend from each pole plate of the electrode assembly 300, and the electrode lead 310 is electrically connected to each of the plurality of electrode tabs extending from each pole plate, for example, by welding, and is positive and negative. A part of the lead is exposed to the top and bottom of the battery case 200, respectively. In addition, an insulating film 320 is attached to a portion of the upper and lower surfaces of the electrode lead 310 in order to increase the sealing degree with the battery case 200 and to secure an electrical insulation state.

The battery case 200 is composed of an upper case 210 and a lower case 220, the receiving portion for mounting the electrode assembly 300, respectively, is formed in the upper case 210 and the lower case 220, It has a pouch shape as a whole. The polymer sheet 410 is attached to the upper end of the inner surface of the accommodating part of the upper case 210, and the polymer sheet 420 is added to the lower end of the inner surface of the accommodating part of the lower case 220.

Although the polymer sheets 410 and 420 including the HF adsorbent are shown in the same shape as the top and bottom surfaces of the electrode assembly 300, the present invention is not limited thereto. Of course, the inner surface may be added in various shapes. When the battery is subjected to an external shock, the impact is partially absorbed by the polymer sheets 410 and 420, thereby reducing the amount of impact applied to the electrode assembly 300, thereby greatly improving the safety of the battery. In addition, since the polymer sheets 410 and 420 contain an HF adsorbent by supporting or coating, the high temperature safety is excellent by adsorbing HF present in the battery and preventing destruction of the SEI film and decomposition of the electrolyte due to HF. .

In some cases, the polymer sheets 410 and 420 may include a moisture adsorbent in addition to the HF adsorbent, or the polymer sheet 410 may include an HF adsorbent and the polymer sheet 420 may include a moisture adsorbent. have. Alternatively, the moisture adsorbent may be locally included in the polymer sheets 410 and 420 including the HF adsorbent as a whole.

In the secondary battery 100, the polymer sheet 420 is added to the inner surface of the lower case 220, the electrode assembly 300 is mounted, and another polymer sheet 410 is added to the upper surface thereof. 210 and the outer peripheral surface 230 may be manufactured by thermal fusion.

The polymer sheets 410 and 420 may be attached to the inner surface of the battery case by a non-reactive adhesive or the like, or may be added in a manner that is simply inserted between the electrode assembly 300 and the inner surface of the battery case.

The additional positions of the polymer sheets 410 and 420 may be part or all of the inner surface of the battery case 200, as shown in FIG. 4, the upper and lower inner surfaces of the battery case accommodating part and the electrode assembly 300. It may be added between the top and bottom surfaces. In addition, as shown in Figure 5, it may be added to the inner surface of the battery case 200 and the side of the electrode assembly 300.

6 is an exploded perspective view of a secondary battery according to a second embodiment of the present invention.

Referring to FIG. 6, the secondary battery 101 has a structure in which an electrode assembly 301 is mounted on a battery case 201 formed of a main body 221 having a receiving portion and a cover 211 corresponding thereto. 2 to 4 except that the electrode leads 311 of the electrode assembly 301 protrude together in one direction.

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.

As described above, the secondary battery case according to the present invention has a polymer sheet containing an HF adsorbent is added to the inner surface, thereby minimizing side reactions in the battery and can effectively remove HF harmful to battery performance. High temperature safety of the battery can be greatly improved. In addition, the impact of the polymer sheet itself may be minimized by the impact of the physical impact applied from the outside, thereby improving the safety of the battery.

Claims (18)

A secondary battery case having an accommodating portion corresponding to a shape of an electrode assembly, the secondary battery case comprising a polymer sheet containing an HF adsorbent so as to be interposed between an outer surface of the electrode assembly and an inner surface of the case. The secondary battery case of claim 1, wherein the polymer sheet is added to an upper surface of the inner surface, a lower surface of the inner surface, or an inner surface of the battery sheet excluding the outer circumferential portion (sealing portion) for sealing the battery case. According to claim 1, wherein the polymer sheet is a secondary battery case, characterized in that located on the upper inner surface and / or lower inner surface of the battery case. The method of claim 1, wherein the polymer sheet is a secondary battery, characterized in that is added in the form of being simply inserted into the corresponding portion between the battery case and the electrode assembly in the assembly process of the secondary battery, or attached to the corresponding portion of the battery case. case. The case of claim 4, wherein the polymer sheet is bonded using a non-reactive adhesive that does not affect the operation of the battery or is bonded by thermal fusion. 6. The secondary battery case of claim 5, wherein the non-reactive adhesive is a silicone polymer adhesive or a carbon fiber polymer adhesive. The method of claim 1, wherein the polymer sheet is polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyethylene-terephthalate (PET), PolyMethylMethAcrylate (PMMA), and Secondary battery case, characterized in that made of one or more materials selected from the group consisting of PAN (polyacrylonitrile). According to claim 1, wherein the polymer sheet is a secondary battery case, characterized in that the form of non-woven fabric or kraft paper. The method of claim 1, wherein the polymer sheet is a secondary battery case, characterized in that the nonwoven fabric made of PP polymer. The case of claim 1, wherein the HF adsorbent is supported or coated on a polymer sheet. The case of claim 1, wherein the HF adsorbent is at least one selected from the group consisting of lithium carbonate, sodium carbonate, calcium hydroxide, activated carbon, diatomaceous earth, perite, and zeolite. According to claim 1, wherein the content of the HF adsorbent is a secondary battery case, characterized in that 0.01 to 50% by weight based on the total weight of the polymer sheet. The case for a secondary battery of claim 10, wherein a bonding aid for increasing the binding force of the HF adsorbent to the polymer sheet is additionally added in the coating process. The case of claim 1, wherein the polymer sheet further includes a moisture adsorbent, or a part or separate polymer sheet of the polymer sheet includes a moisture adsorbent instead of an HF adsorbent. The case for a secondary battery of claim 1, wherein the battery case is made of a laminate sheet including an outer coating layer of a polymer film, a barrier layer of metal foil, and a polyolefin-based inner sealant layer. A secondary battery comprising a case for a secondary battery according to any one of claims 1 to 15. The secondary battery according to claim 16, wherein the battery is a pouch type battery in which an electrode assembly is incorporated in a pouch type case of a laminate sheet including a metal layer and a resin layer. (i) adding a polymer sheet containing an HF adsorbent to all or a part of an inner surface of a battery case in which an accommodating part corresponding to a shape of an electrode assembly is formed; (ii) inserting an electrode assembly into a battery case to which a polymer sheet is added; ; And (iii) optionally adding a polymer sheet containing an HF adsorbent to the top surface of the electrode assembly.

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