WO2014073899A1 - Method for manufacturing secondary battery - Google Patents

Abstract

The present invention is a method for manufacturing a secondary battery having an electrode assembly, impregnated in an electrolyte, built into a battery case, the method, which enhances wetting between the electrode assembly and the electrolyte, comprising the steps of: (a) injecting an electrolyte into a chamber; (b) immersing and impregnating the electronic assembly, having a separation film interposed between the positive and negative poles, in an electrolyte filling the chamber; and (c) moving, along with the electrolyte, the electrode assembly which as passed through step (b), to a battery case. The secondary battery according to the present invention can enhance the electrochemical performance by enhancing the impregnation property, ion conductivity and electronic conductivity of an electrolyte.

Description

Secondary Battery Manufacturing Method

The present invention is a method of manufacturing a secondary battery that is embedded in a battery case in the state of the electrode assembly is impregnated with the electrolyte,

(a) injecting electrolyte into the chamber;

(b) dipping and immersing an electrode assembly having a structure in which a separator is interposed between an anode and a cathode in an electrolyte solution contained in the chamber;

(c) transferring the electrode assembly passed through step (b) together with the electrolyte to the battery case;

By a process comprising a, it relates to a manufacturing method characterized in that to improve the interface (wetting) of the electrode assembly and the electrolyte solution (wetting).

As the development and demand for mobile devices increases, the demand for secondary batteries as energy sources is increasing rapidly. Among them, lithium secondary batteries with high energy density and operating potential, long cycle life, and low self discharge rate Batteries have been commercialized and widely used.

Also, as interest in environmental issues has increased recently, electric vehicles (EVs) and hybrid electric vehicles (HEVs), which can replace vehicles using fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, There is a lot of research on the back. Although nickel-metal hydride (Ni-MH) secondary batteries are mainly used as power sources of such electric vehicles (EVs) and hybrid electric vehicles (HEVs), lithium secondary batteries of high energy density, high discharge voltage and output stability are used. Research is actively underway and some are commercialized.

The lithium secondary battery has a structure in which a non-aqueous electrolyte containing lithium salt is impregnated in an electrode assembly having a porous separator interposed between a positive electrode and a negative electrode on which an active material is coated on an electrode current collector.

In general, a lithium secondary battery is assembled by alternately overlapping a positive electrode, a negative electrode, and a separator, inserting a battery case of a predetermined size and shape into a can or pouch, and finally injecting an electrolyte solution. Proceed. At this time, the electrolyte injected later is permeated between the positive electrode, the negative electrode and the separator by the capillary force (capillary force). However, due to the nature of the material, since the positive electrode, the negative electrode and the separator are all hydrophobic materials, the electrolyte is a hydrophilic material, so the wetting of the electrolyte to the electrode and the separator is time-consuming and difficult process conditions. Is required.

In addition, in recent years, as the device or apparatus is enlarged in size, the volume to which the electrolyte penetrates is reduced and the area is increased, so that the electrolyte cannot be introduced into the battery and only exists locally outside. The battery manufactured as described above partially reduces the amount of electrolyte in the battery, thereby greatly reducing the battery capacity and performance.

In order to improve the wettability of the electrode, a method of injecting an electrolyte at a high temperature or injecting an electrolyte in a pressurized or reduced pressure state is used. However, in this case, there is a problem such that the existing electrode assembly and the electrolyte are deformed by heat to cause an internal short circuit.

Therefore, there is a very high need for a technology for a method of manufacturing a secondary battery having stability at high temperature and improved wettability.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

The inventors of the present application, after repeated in-depth research and various experiments, as described later, injecting an electrolyte solution into a chamber (impregnated), impregnating an electrode assembly and then moving to a battery case to manufacture a secondary battery In this case, it was confirmed that the desired effect could be achieved, and the present invention was completed.

Accordingly, the present invention provides a method for manufacturing a secondary battery that is embedded in a battery case in the state where the electrode assembly is impregnated with the electrolyte,

(a) injecting electrolyte into the chamber;

(b) dipping and immersing an electrode assembly having a structure in which a separator is interposed between an anode and a cathode in an electrolyte solution contained in the chamber;

(c) transferring the electrode assembly passed through step (b) together with the electrolyte to the battery case;

By a process comprising a, it provides a manufacturing method characterized in that to improve the interface (wetting) of the electrode assembly and the electrolyte solution (wetting).

In the case of a method of injecting an electrode assembly into a conventional battery case and injecting an electrolyte solution, it takes a long time because the electrode assembly is impregnated by injecting a limited amount of electrolyte according to the size of the battery case and impregnating the entire electrode assembly. There was a problem that was not impregnated.

Therefore, the manufacturing method according to the present invention impregnates the electrode assembly in a chamber containing a large amount of electrolyte solution, so that the impregnation properties such as the impregnation rate of the electrode assembly is improved, and at the same time can be impregnated a plurality of electrode assemblies manufacturing processability This has the advantage of being improved.

That is, the manufacturing method according to the present invention can increase the mobility (mobility) of the electrolyte materials, including the step of impregnating the electrode assembly by injecting the electrolyte in a separate chamber, and then moving the electrode assembly and the electrolyte to the battery case. In addition, the interfacial contact (wetting) of the electrode assembly and the electrolyte may be improved.

In addition, in the present invention, the volume of the chamber may be 1.5 times or more, in detail, 2 times or more, and up to 10 times the volume of the electrode assembly, and thus, the electrode in the chamber containing a large amount of electrolyte solution. The assembly can be sufficiently impregnated in a short time.

That is, since the chamber impregnates the electrode assembly in the battery case, the impregnation property such as the impregnation rate of the electrode assembly may be improved, and the electrode assembly may be impregnated at a time, thereby improving manufacturing processability.

The viscosity of the electrolyte may be 0.1 cps to 5 cps, more specifically 1 cps to 4 cps. The manufacturing method according to the present invention has an advantage of increasing the interface contact between the electrode assembly and the electrolyte by increasing the impregnation of the electrolyte even when the viscosity of the electrolyte is high. However, when the viscosity of the electrolyte is greater than 5 cps, the mobility of the electrolyte materials cannot be maximized, which is not preferable.

The present invention provides a secondary battery manufactured using the above manufacturing method.

Specifically, the secondary battery may be a lithium secondary battery.

Hereinafter, the structure of such a lithium secondary battery is demonstrated.

The lithium secondary battery includes a cathode prepared by applying a mixture of a cathode active material, a conductive material and a binder on a cathode current collector, followed by drying and pressing, and a cathode manufactured using the same method, in which case, if necessary Further fillers may be added to the mixture.

The positive electrode current collector is generally made to a thickness of 3 to 500 ㎛. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like may 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 positive electrode active material may be, for example, 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 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, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); _{LiV 3 O 8, LiFe 3 O} 4, V 2 O 5, vanadium oxide such as Cu ₂ V ₂ O _7; 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 , LiNi _x Mn _2-x O ₄ (0.01 ≦ x ≦ 0.6) and the like can be used.

The conductive material is typically added in an amount of 1 to 50% by weight based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof 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.

The binder is a component that assists in bonding the active material and the conductive material 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 inhibiting expansion of the positive electrode, and 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.

The negative electrode current collector is generally made of a thickness of 3 ~ 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 current 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 active material is, for example, 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 Me ': Al, B, P, Si, group 1, group 2, group 3 element, halogen of the periodic table; 0 <x≤1;1≤y≤3; 1≤z≤8) Metal complex oxides such as these; 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 lithium secondary battery may have a structure in which a lithium salt-containing electrolyte is impregnated in an electrode assembly having a structure in which a separator is interposed between a positive electrode and a negative electrode.

The separator is interposed between the anode and the cathode, and 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, olefin polymers such as chemical resistance and hydrophobic polypropylene; Sheets or non-woven fabrics made of glass fibers or polyethylene are used. 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 electrolyte solution is composed of an electrolyte solution and a lithium salt, and the electrolyte solution, but non-aqueous organic solvent, organic solid electrolyte, inorganic solid electrolyte and the like are used, but are not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and gamma Butyl lactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxorone, formamide, dimethylformamide, dioxolon , Acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxorone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbo Aprotic organic solvents such as nate derivatives, tetrahydrofuran derivatives, ethers, methyl pyroionate and ethyl propionate can 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, Polymerizers 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 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 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.

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, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics, and FEC (Fluoro-Ethylene) may be further included. Carbonate), PRS (Propene sultone) may be further included.

In one preferred embodiment, lithium salts such as LiPF ₆ , LiClO ₄ , LiBF ₄ , LiN (SO ₂ CF ₃ ) _2, and the like, may be prepared by cyclic carbonate of EC or PC as a highly dielectric solvent and DEC, DMC or EMC as a low viscosity solvent. Lithium salt-containing non-aqueous electrolyte can be prepared by adding to a mixed solvent of linear carbonate.

The battery pack including the lithium secondary battery may be used as a power source for a vehicle requiring high temperature stability, long cycle characteristics, high rate characteristics, and the like.

Examples of the vehicle may be an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or the like. It is not limited to this.

1 is a graph showing the electrolyte impregnation time according to the electrode assembly area according to Experimental Example 1.

<Example 1>

An electrode assembly was prepared through a porous separator between a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material. Ethylene carbonate and ethylmethyl carbonate were mixed at a volume ratio of 3: 7, and a lithium non-aqueous electrolyte solution containing 1 M LiPF ₆ as a lithium salt was prepared. After the electrolyte was injected into the chamber and the electrode assembly prepared above was immersed in the electrolyte solution, the electrode assembly was transferred to the battery case together with the electrolyte solution and sealed to manufacture a secondary battery.

Comparative Example 1

A secondary battery was manufactured in the same manner as in Example 1, except that the electrode assembly prepared in Example 1 was placed in a battery case, followed by impregnating the electrode assembly by injecting an electrolyte solution.

Experimental Example 1

In Example 1 and Comparative Example 1, the time taken for the total area of the electrode assembly to be impregnated after pouring the electrolyte was measured and the results are shown in FIG. 1.

1, in the case of the secondary battery according to Example 1, the time taken for the entire area of the electrode assembly to be impregnated is relatively quick as compared to the secondary battery according to Comparative Example 1.

As described above, the secondary battery manufacturing method according to the present invention comprises the step of impregnating the electrode assembly in the chamber containing a large amount of electrolyte solution and then moving to the battery case, the impregnation rate of the electrode assembly is improved, excellent electrolyte impregnation At the same time, a plurality of electrode assemblies can be impregnated at a time, thereby improving the manufacturing process of the battery. In particular, the manufacturing method according to the present invention can be effectively used in an electrode assembly including a high loading electrode or a plurality of electrode units relatively poor electrolyte impregnation.

Claims (7)

As a method of manufacturing a secondary battery that is embedded in a battery case in a state where the electrode assembly is impregnated with an electrolyte solution, (a) injecting electrolyte into the chamber; (b) dipping and immersing an electrode assembly having a structure in which a separator is interposed between an anode and a cathode in an electrolyte solution contained in the chamber; (C) the method comprising the step of moving the electrode assembly after the step (b) with the electrolyte solution to the battery case, to improve the interfacial contact (wetting) of the electrode assembly and the electrolyte solution. The method of claim 1, wherein the volume of the chamber is 1.5 times or more based on the volume of the electrode assembly. The method of claim 1, wherein the volume of the chamber is at least twice the volume of the electrode assembly. The method of claim 1, wherein the electrolyte has a viscosity of 0.1 cps or more and 5 cps or less. The method of claim 1, wherein the electrolyte has a viscosity of 1 cps or more and 4 cps or less. Secondary battery, characterized in that manufactured using the manufacturing method according to claim 1 The secondary battery of claim 6, wherein the secondary battery is a lithium secondary battery.

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