KR20100071790A - Pouch type secondary battery having enhanced stability - Google Patents

Abstract

PURPOSE: A pouch type secondary battery is provided to firmly maintain a lead film from moisture of an electrical resistance by including a thermal curing layer on one side of the lead film. CONSTITUTION: A pouch type secondary battery comprises the following: an electrode assembly(130) including a positive electrode, a negative electrode, and a separator; electrode lead tabs(140) extended to the electrode assembly; a pouch external material receiving the electrode assembly; and a lead film(180) for insulating the electrode lead tabs and the pouch external material. The lead film includes a thermal curing layer(190) on one side. The thermal curing layer is formed with a thermosetting resin selected from the group consisting of a melanin resin, a phenol resin, a urea resin, and others.

Description

Pouch type secondary battery having enhanced stability

The present invention relates to a pouch type secondary battery with improved safety, and in particular, by forming a thermosetting layer on at least one surface of a lead film for electrical insulation between the lead tab and the pouch, thereby preventing breakdown of insulation resistance and eliminating the possibility of water penetration. It relates to a pouch type secondary battery that can improve the safety of the battery.

As portable wireless devices such as video cameras, portable telephones, and portable PCs become lighter and more functional, the demand for secondary batteries is rapidly increasing as a source of energy, and research on lithium secondary batteries having high energy density and discharge voltage among such secondary batteries is possible. Is being actively made and also commercialized and widely used.

Secondary batteries are attracting attention as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs), which are proposed as solutions for air pollution of conventional gasoline and diesel vehicles that use fossil fuels.

Representatively, there is a high demand for square and pouch type secondary batteries that can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries, and high energy density, discharge voltage, and output stability in terms of materials. Demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries is high.

In addition, secondary batteries are classified according to the structure of the electrode assembly having a cathode / separation membrane / cathode structure. Representatively, a jelly having a structure in which long sheet-shaped anodes and cathodes are wound with a separator interposed therebetween -Roll (electrode) electrode assembly, a stack (stacked type) electrode assembly in which a plurality of positive and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator, and the positive and negative electrodes of a predetermined unit are interposed through a separator And a stacked / folding electrode assembly having a structure in which a bi-cell or full cells stacked in a state are wound.

Recently, a pouch-type battery having a structure in which a stack type or a stack / fold type electrode assembly is incorporated into a pouch type battery case of an aluminum laminate sheet has attracted much attention due to its low manufacturing cost, small weight, and easy shape deformation. Its usage is also gradually increasing.

FIG. 1 is a schematic exploded perspective view of a general structure of a conventional representative pouch type secondary battery. Referring to FIG. 1, a pouch type secondary battery includes an electrode assembly 30 in which a negative electrode and a positive electrode are insulated by a separator, electrode tabs 40 and 50 extending from the electrode assembly 30, and the electrode And an electrode lead 60 and 70 welded to the tabs 40 and 50, and a battery case 20 accommodating the electrode assembly 30.

The electrode assembly 30 is a power generator in which a positive electrode and a negative electrode are sequentially stacked in a state where a separator is interposed therebetween, and has a stack type or a stack / fold type structure. The electrode tabs 40, 50 extend from each electrode plate of the electrode assembly 30, and the electrode leads 60, 70 may include a plurality of electrode tabs 40, 50 extending from each electrode plate, for example. By welding

Solutions are electrically connected to each other, and part of the battery case 20 is exposed to the outside.

In addition, lead films 80 having excellent insulating properties are attached to upper and lower portions of the electrode leads 60 and 70 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 is composed of an upper 20a and a lower sheet 20b, and each upper and lower sheet is protected by a heat seal layer 21 / aluminum metal layer 22 / nylon represented by CPP. The layer 33 has a conventional three-layer structure, and the heat-sealing layers of the upper and lower sheets are bonded by heat and pressure to accommodate the electrode assembly. The lead film is usually configured using a PP film, through which the inner layer of the battery case 20 is heat-sealed and bonded through heat and pressure.

However, when heat is applied to the tab lead portion, the lead film is melted and pushed to the side, resulting in uneven adhesion. Moisture penetrates through this region to degrade battery performance and cause stability problems. .

Therefore, the present invention is to solve the problems of impairing the safety and battery life of various batteries caused by external moisture penetration due to the unstable adhesion of the lead film in a conventional pouch battery.

Accordingly, an object of the present invention is to provide a pouch type secondary battery with improved battery safety and battery life.

In the present invention, a thermal curing layer is further included on at least one surface of the lead film configured to insulate the electrode lead tab and the pouch case in a conventional pouch battery, thereby maintaining the lead film firmly from moisture or electrical resistance from the outside. We can solve problems like this.

As in the present invention, even if there is a moisture permeation including a thermosetting layer on at least one surface of the lead film, the lead film is firmly supported to maintain electrical insulation, thereby improving battery safety and battery life.

The pouch type secondary battery of the present invention for achieving the above object is an electrode assembly having a structure in which a cathode and an anode are wound with a separator interposed therebetween, an electrode lead tab extending to the electrode assembly, and a pouch packaging material for accommodating the electrode assembly. And a lead film for insulation of the electrode lead tab and the pouch sheathing material, and further comprising a thermosetting layer on at least one surface of the lead film.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. This is for easier understanding of the present invention, and the scope of the present invention is not limited thereto.

The present invention relates to a pouch type secondary battery characterized by further comprising a thermosetting layer on at least one surface of the lead film.

In detail, the pouch-type secondary battery according to the present invention includes the electrode assembly 130 and the positive and negative electrode tabs 140 and 150 extending from the electrode assembly 130 and the positive and negative electrode tabs as shown in FIG. 2. It comprises a electrode lead (160, 170) to be welded, and the battery case 120 for receiving the electrode assembly 130.

The electrode assembly 130 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 positive and negative electrode tabs extend from each of the electrode plates of the electrode assembly, and the electrode leads are electrically connected to each of the positive and negative electrode tabs extending from each of the electrode plates, for example, by welding, to the outside of the battery case. Some are exposed.

In addition, when the excess part and the cover of the case body 120 are heat-sealed by the heat sealer, the short between the heat sealer and the electrode lead 160 is prevented from occurring, and the electrode leads 160 and 170 and the battery case 120 are prevented. In order to ensure the sealing property with), the insulating film 180 is attached to the upper and lower surfaces of the electrode leads (160, 170). In the present invention, the thermosetting layer 190 is further included on at least one surface of the insulating film 180. The thermosetting layer is preferably composed of at least one thermosetting resin selected from the group consisting of melanin resin, phenol resin, urea resin, epoxy resin, and polyurethane.

The thermosetting layer is formed on one surface 190 of the lead film 180a as shown in FIG. 3 or on both sides 190 and 190 'of the lead film 180a as shown in FIG. 4. All is possible.

The thermosetting layer is preferably formed in 10 to 100㎛ in terms of preventing damage to the pouch and tab when forming the battery.

In general, the lead film is formed at a position where the upper and lower cases of the battery case are heat-sealed to accommodate the electrode assembly, and thus high heat or pressure is applied thereto. Therefore, when heat is applied to this area, the PP film used as the lead film is melted together, resulting in poor adhesiveness, and moisture penetrates into this area, thereby causing battery safety problems.

Therefore, when the thermosetting layer is included on at least one surface of the lead film as in the present invention, however, even when heat is applied to the tab lead portion, the thermosetting layer is mainly formed from a thermosetting polymer and thus is transferred to the lower lead film to lead film. This melting or the like does not occur, and the lead film is firmly supported to maintain electrical insulation, thereby improving battery safety.

The pouch-shaped case 120 is generally made of an aluminum laminate sheet, which is integrally connected to the case body and the case body including a concave shape receiving portion 120b on which the electrode assembly 130 can be seated. It consists of a cover (120a).

On the other hand, the electrode assembly according to the present invention is composed of a positive electrode including a positive electrode active material, a negative electrode containing a negative electrode active material, and a separator.

Specifically, the positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive agent, and a binder onto a positive electrode current collector, followed by drying, and optionally, a filler may be further added to the mixture.

The positive electrode active material according to the present invention 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; Lithium manganese oxides (LiMnO ₂ ) such as Li _{1 + x} Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Nickel-site 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 oxide); 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 , where M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of lithium of the formula is substituted with alkaline earth metal ions; Disulfide compounds; It can be mixed with a compound containing a lithium intercalation material as a main component, such as a composite oxide formed by Fe ₂ (MoO ₄ ) ₃ or a combination thereof, and it is preferable to use a compound containing an olivine structure. desirable.

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. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, 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 conductive agent is typically added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Such a conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive agent 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 fiber and metal fiber; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists in bonding the active material and the conductive agent to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, Polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers, and the like.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

In addition, the negative electrode is manufactured by coating and drying a negative electrode material on the negative electrode current collector, and if necessary, the components as described above may be further included.

The negative electrode current collector is generally made to 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. In addition, like the positive electrode collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode material includes amorphous carbon or crystalline carbon, and specifically, carbon such as hardly graphitized carbon and graphite carbon; Li _x Fe ₂ O ₃ (0 ≦ x ≦ 1), LixWO ₂ (0 ≦ x ≦ 1), Sn _x Me _1-x Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al Metal complex oxides such as 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 oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

As the separator that insulates the electrodes between the anode and the cathode, a conventionally known polyolefin-based separator or a composite separator in which an organic and inorganic composite layer is formed on the olefin-based substrate may be used, and is not particularly limited.

The electrolyte according to the present invention is a lithium salt-containing non-aqueous electrolyte, which consists of a non-aqueous electrolyte and lithium. As the nonaqueous electrolyte, a nonaqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used.

As said non-aqueous electrolyte, N-methyl- 2-pyrrolidinone, a propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl Low lactone, 1,2-dimethoxy ethane, tetrahydroxy franc

(franc), 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolon, formamide, dimethylformamide, dioxolon, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, Trimethoxy methane, dioxorone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrionate, ethyl propionate An aprotic organic solvent such as may be used.

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, Polymers containing ionic dissociating groups and the like can be used.

Examples of the inorganic solid electrolyte include 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 dissolve in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF 6, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic lithium carbonate, lithium 4-phenyl borate, imide and the like can be used have.

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

The pouch sheath is generally composed of a heat seal layer / alumina layer (metal layer) / outer layer, and a plurality of polymer layers are further added between the heat seal layer and the metal layer and between the metal layer and the outer layer to improve strength and heat resistance. It may also be included.

Examples of the specific configuration of the packaging material, outer layer / metal layer / heat seal layer = Ny / Al / CPP, PET / Al / CPP, PET / Al / PET / CPP, PET / Ny / Al / CPP, PET / Ny / Al / Ny / CPP, PET / Ny / Al / Ny / PE, Ny / PE / Al / LLDPE, PET / PE / Al / PET / LDPE or PET / Ny / Al / LDPE / CPP. In addition, as mentioned above, metal other than aluminum can be used as a metal layer, of course.

The metal layer constituting the pouch sheathing material plays the most important role of protecting the contents by preventing the entry of moisture, oxygen, and light, in addition to improving the strength of the pouch sheathing material, and using stainless steel or nickel-plated iron as a material. However, aluminum (Al) is most preferred in light weight, elongation, cost, and ease of processing.

1 is a perspective view of a pouch type secondary battery,

2 is a perspective view of a pouch type secondary battery according to the present invention;

3 and 4 are cross-sectional views of a lead film including a thermosetting layer according to an embodiment of the present invention.

Claims (4)

An electrode assembly having a structure in which a cathode and an anode are wound with a separator interposed therebetween, An electrode lead tab extending into the electrode assembly, Pouch packaging material for receiving the electrode assembly, And a lead film for insulating the electrode lead tab and the pouch sheathing material, wherein at least one surface of the lead film further comprises a thermosetting layer. The pouch type secondary battery of claim 1, wherein the thermosetting layer comprises at least one thermosetting resin selected from the group consisting of a melanin resin, a phenol resin, a urea resin, an epoxy resin, and a polyurethane. The pouch type secondary battery of claim 1, wherein the thermosetting layer is formed to a thickness of 10 to 100 μm. The pouch type secondary battery of claim 1, wherein the thermosetting layer is formed on one or both surfaces of the lead film.

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