KR20150038932A - Method of Secondary Battery Using Protective Case - Google Patents

Abstract

The present invention relates to a method for manufacturing a secondary battery with an electrode assembly embedded in a square shaped can. The method for manufacturing the secondary battery includes the following steps: (a) inserting the electrode assembly into the square shaped can and combining a top can with an electrolyte inlet with the upper side of the square shaped can which is opened; (b) inserting the square shaped can to a protection case with an inner shape corresponding to the outer appearance of the square shaped can; (c) injecting the electrolyte through the electrolyte inlet and performing a charging operation for a first pre-formation; (d) sealing the electrolyte inlet after the gas generated in the first pre-formation is outputted and performing a full charging operation, a full discharging operation, and an aging operation for a second pre-formation; and (e) outputting the gas generated in the second pre-formation and removing the protection case.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a secondary battery using a protective case,

The present invention relates to a method of manufacturing a secondary battery using a protective case, and more particularly, to a method of manufacturing a secondary battery in which an electrode assembly is embedded in a can, comprising the steps of inserting an electrode assembly into a square can, Inserting a square cap into the protective case having an inner surface shape corresponding to the outer shape of the square can, injecting an electrolyte through the electrolyte injection port, A process of performing charging for pre-formation, a process of discharging gas generated in the primary activation process, sealing the electrolyte injection port, performing full charge / discharge and aging for secondary activation, and Discharging gas generated during the secondary activation process, and removing the protective case.

BACKGROUND ART [0002] In recent years, rechargeable secondary batteries have been widely used as energy sources for wireless mobile devices. In addition, the secondary battery is an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (HEV), and the like, which are proposed as solutions for air pollution of existing gasoline vehicles and diesel vehicles using fossil fuels (Plug-In HEV) and the like.

An electrode assembly in which a battery reaction occurs in a secondary battery is generally composed of a positive electrode plate coated with a positive electrode active material, a negative electrode plate coated with a negative electrode active material, and an electrolyte solution impregnated in the separator. The electrode assembly of such a secondary battery is largely divided into a jelly-roll type (wound type) electrode assembly and a stacked type (laminate type) electrode assembly depending on its structure. Therefore, a prismatic battery is manufactured by housing a jelly-roll type electrode assembly or a stacked electrode assembly in a rectangular metal case.

Generally, a prismatic battery is manufactured by mounting an electrode assembly inside a square metal can, mounting an upper insulator on an open upper end thereof, welding a base plate thereon, and injecting and sealing an electrolyte solution.

At this time, a predetermined amount of the electrolyte solution is injected and the injection port is not sealed. In this case, the battery is first charged for activation, the electrolyte is injected again, and then the secondary battery is charged. So that the plurality of cells are operated.

In this process, the volume of the prismatic secondary cell increases in the thickness direction due to the pressure applied at the time of sealing the injection port and the gas generated at the time of secondary charging. Since the degree of increase of the thickness varies depending on the battery cell, . At this time, the increased thickness is about 200 占 퐉, which is a size that can not be ignored while the thickness of the prismatic cell is about 3.5 mm to 10 mm. In addition, there is a possibility that the battery may be damaged when the battery is moved on the belt conveyor.

In order to solve the thickness variation of the prismatic secondary battery, a method of pressing a battery with a die in a state in which an injection port is sealed is widely used. However, since the pressing process proceeds at a descending rate so fast that the square can can cause plastic deformation to prevent the cell thickness from being restored again, the cell is damaged due to a strong impact. For example, a phenomenon may occur in which the active material is separated from the current collector when compressed by the die, or the welded portion for electrical connection is broken. In addition, such pressing is disadvantageous in that the working time is delayed because the pressing is performed by a discontinuous process of moving the battery and lowering the mold, and noise may be generated at the moment of contact between the mold and the battery cell.

Accordingly, there is a high need for a technique that can effectively reduce the thickness deviation between the battery cells while preventing damage to the battery as much as possible, simplify the mass production process, shorten the working time, and reduce the manufacturing cost.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

It is an object of the present invention to provide a method of manufacturing a secondary battery including a process of storing the battery in a protective case for protecting the outer surface of the battery before and after the electrolyte injection and activation process, And to provide a secondary battery manufacturing method capable of effectively preventing problems such as deformation and defective appearance of a secondary battery.

It is still another object of the present invention to provide a battery pack that can effectively reduce thickness variations among battery cells while minimizing damage to the battery and can reduce work time and manufacturing cost by a continuous and simple mass production process, And it is an object of the present invention to provide a secondary battery manufacturing method capable of improving a poor working environment.

According to an aspect of the present invention, there is provided a method of manufacturing a secondary battery,

A method of manufacturing a secondary battery in which an electrode assembly is embedded in a can,

(a) inserting an electrode assembly into a rectangular can, and joining a top cap having an electrolyte injection port to an open top of a square can;

(b) inserting a square can in the inside of the protective case having an inner surface shape corresponding to the outer shape of the square can;

(c) injecting an electrolyte through the electrolyte injection port and performing charging for pre-formation;

(d) discharging gas generated in the first activation process, sealing the electrolyte injection port, performing full charge / discharge and aging for secondary activation; And

(e) discharging gas generated in the secondary activation process and removing the protective case;

As shown in FIG.

Preferably, the method may include a step of moving by a belt conveyor before or after the step of injecting the electrolyte in the step (c), and the structure may be a structure in which an electrolyte is injected into the plurality of cells simultaneously or sequentially, And the like.

The 'activation' process refers to a process of charging the prismatic secondary cell with electricity to convert it into electrochemical energy. The 'primary activation' process is a process of manufacturing a battery And the 'secondary activation' process is a charging / discharging process performed at the final stage in the process of manufacturing the battery, and proceeds by the method of full charge, full charge discharge and high temperature aging (aging).

Charging and discharging of the secondary activation step is carried out for the purpose of checking the capacity of the battery and selecting defective products together with the activation of the battery cell, and the high temperature aging is carried out in order to substantially select defective products.

As described above, the prismatic secondary battery may have a problem that the volume of the prismatic battery increases in the thickness direction due to the pressure applied at the time of sealing the injection port, the gas generated during the activation and the physical expansion of the electrode assembly, Such as being stuck to the outside of the battery.

Meanwhile, the method of manufacturing a secondary battery according to the present invention includes a process of storing the battery in a protective case for protecting the outer surface of the battery before and after the electrolyte injection and activation process during the manufacturing process of the secondary battery, and a process of removing the protective case. It is possible to effectively prevent problems such as deformation of the battery and defective appearance caused in the manufacturing process of the battery.

The protective case is not particularly limited as long as the outer surface of the square can is protected and can be easily mounted and detached. Specifically, the protective case can be a structure that surrounds the entire outer surface of the can, except for the upper surface for inserting the square can. have.

In one specific example, the prismatic can and the protective case are preferably formed by a drawing work in which the material plate on the die surface is moved in a circumferential direction while being moved between the punch and the die to form the side wall, It is not.

The prismatic and protective cases are preferably made of aluminum or an aluminum alloy in consideration of ease of processing and mechanical strength of a certain level or higher, but are not limited thereto.

The electrode assembly is not particularly limited as long as it has a structure in which a plurality of electrode tabs are connected to form an anode and a cathode. Preferably, the electrode assembly has a jelly-roll structure, a stack structure, a stack- Lamination-stacked structure. Specifically, the jelly-roll is coated with an electrode active material on a metal foil used as a current collector, dried and pressed, cut in a band shape having a desired width and length, diverged from a cathode and an anode using a separator, To form an elliptical shape on the horizontal cross section.

The secondary battery according to the present invention can be variously applied regardless of the type and the external shape of the battery cell, and can be preferably a lithium secondary battery.

For reference, a typical lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt.

The positive electrode is prepared, for example, by coating a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, and then drying the mixture. Optionally, a filler may be further added to the mixture.

The cathode 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; 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 ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide expressed by the formula LiNi _1-x M _x O ₂ (where 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} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black 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, aluminum, and nickel powder; Conductive whiskey 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 which assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, 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.

The negative electrode is manufactured by applying and drying a negative electrode active material on a negative electrode collector, and if necessary, the above-described components may be selectively included.

Examples of the negative electrode active material include carbon such as non-graphitized carbon and graphite carbon; B, P, Si, Group 1 of the periodic table, LixFe2O3 (0? X? 1), LixWO2 (0? X? 1), SnxMe1-xMe'yOz (Me: Mn, Fe, Pb, 2 < / RTI > group III element, halogen, 0 < x < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; Metal oxides such as SnO 2, 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 ₂ , GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The separation membrane 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 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The non-aqueous electrolyte solution containing a lithium salt is composed of a polar organic electrolyte and a lithium salt. As the electrolytic solution, a non-aqueous liquid electrolytic solution, an organic solid electrolyte, an inorganic solid electrolyte and the like are used.

Examples of the nonaqueous liquid electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation 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 and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble 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 carboxylic acid lithium, lithium tetraphenyl borate and imide have.

For the purpose of improving the charge-discharge characteristics and the flame retardancy, the non-aqueous liquid electrolyte may contain, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride and the like are added It is possible. 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.

Meanwhile, in the manufacturing method of the present invention, the activation process of the battery can be performed by a known method. For example, in the first activation process, the anode and the anode active material change from a low state to a high energy state, And / or by charging in a multi-step process in order to ensure that the low current is supplied for a relatively long period of time and that the battery is steadily charged without difficulty.

The 'C-rate' is a current that flows when the capacity of the battery is completely discharged in one hour. The 'low C-rate and multi-step process' means that the capacity is sequentially increased by a low- it means.

The present invention also provides a battery cell characterized by being manufactured by the above manufacturing method.

Such a secondary battery includes a plurality of battery cells used as a power source for a middle- or large-sized device requiring high temperature stability, long cycle characteristics, and high rate characteristics, And may be preferably used as a unit cell in a battery pack.

Preferred examples of the device include a notebook, a mobile phone, a PDP, a PMP, an MP3 player, a DSC (Digital Still Camera), a DVR, a smart phone, a GPS system, a camcorder, an electric vehicle, a hybrid electric vehicle, a plug- Power storage devices, and the like, but the present invention is not limited thereto.

As described above, the method for manufacturing a secondary battery according to the present invention includes a process of storing the battery in a protective case for protecting the outer surface of the battery before and after the electrolyte injection and activation process during the manufacturing process of the secondary battery, and a process of removing the protective case It is possible to effectively prevent problems such as deformation of the battery and defective appearance caused in the manufacturing process of the battery.

1 to 4 are schematic views showing a procedure of a method of manufacturing a secondary battery according to an embodiment of the present invention.

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

1 to 4 are schematic views illustrating a procedure of a method of manufacturing a secondary battery according to an embodiment of the present invention.

A method of manufacturing a secondary battery according to the present invention includes the steps of inserting an electrode assembly 110 into a rectangular can 120 and inserting an electrode assembly 110 into a top cap 130 is inserted into the open upper end of the rectangular can 120, inserting the square can 120 into the protective case 150 having an inner shape corresponding to the outer shape of the rectangular can 120, Injecting an electrolyte solution through the electrolyte injection port 160 and performing charging for pre-formation; discharging gas generated in the first activation process, sealing the electrolyte injection port 160, A process of performing full charge / full discharge and aging to activate the secondary cell, and a process of discharging gas generated in the secondary cell activation process and removing the protective case 150.

1, an electrode assembly 110 of a rechargeable battery 100 is embedded in a square can 120, and a protruding electrode terminal (for example, a negative electrode terminal: 132 are formed on the top surface of the cap body.

The negative electrode of the electrode assembly 110 is electrically connected to the lower end of the negative electrode terminal 132 on the top cap 130 via the negative electrode tab 112. The negative electrode terminal 132 is electrically connected to the top cap 130 by the insulating member 134, (130). On the other hand, another electrode (for example, an anode) of the electrode assembly 110 is electrically connected to the top cap 130 whose anode tab 114 is made of a conductive material such as aluminum, stainless steel, And forms a bipolar terminal by itself.

A sheet-like insulating member 140 (not shown) is disposed between the rectangular can 120 and the electrode assembly 110 to ensure the electrical insulation between the electrode assembly 110 and the top cap 130 except for the electrode tabs 112, The top cap 130 is mounted and welded along the contact surfaces of the top cap 130 and the square can 120.

2 to 4, a rectangular can 120 is inserted into a protective case 150 having an inner surface shape corresponding to the outer shape of the square can 120 as shown in FIG. 2, Specifically, the protective case 150 is made of an aluminum alloy, and is formed so as to surround the entire outer surface of the square can 120, except for the top surface for inserting the square can 120.

3, the rectangular can 120 inserted in the protective case 150 is placed on the belt conveyor 170, and a predetermined amount of the electrolyte solution is injected through the electrolyte injection port 160 to perform primary activation And the inner gas is discharged through the electrolyte injection port 160.

In the method shown in FIG. 3, although one secondary battery 100 is described as being located on the belt conveyor 170, the process of injecting or activating an electrolyte simultaneously or sequentially to a plurality of cells proceeds It is possible to do.

Finally, after the electrolyte is replenished again, the electrolyte injection hole 160 is sealed, secondary activation is performed, and a large amount of generated gas is discharged. Then, as shown in FIG. 4, the protection case 150 is removed, .

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (13)

A method of manufacturing a secondary battery in which an electrode assembly is embedded in a can,
(a) inserting an electrode assembly into a rectangular can, and joining a top cap having an electrolyte injection port to an open top of a square can;
(b) inserting a square can in the inside of the protective case having an inner surface shape corresponding to the outer shape of the square can;
(c) injecting an electrolyte through the electrolyte injection port and performing charging for pre-formation;
(d) discharging gas generated in the first activation process, sealing the electrolyte injection port, performing full charge / discharge and aging for secondary activation; And
(e) discharging gas generated in the secondary activation process and removing the protective case;
≪ / RTI > The method as claimed in claim 1, further comprising the step of moving the battery by a belt conveyor before or after the step of injecting the electrolyte in the step (c). The method for manufacturing a secondary battery according to claim 1, wherein the protective case is formed so as to surround the entire outer surface of the square can, except for the top surface for inserting the square can. The method for manufacturing a secondary battery according to claim 1, wherein the rectangular can and the protective case are formed by drawing work. The method for manufacturing a secondary battery according to claim 1, wherein the rectangular can and the protective case are made of aluminum or aluminum alloy, respectively. The method of claim 1, wherein the electrode assembly is one of a jelly-roll structure, a stack structure, a stack-folding structure, and a lamination-stack structure. [7] The method of claim 6, wherein the electrode assembly has an elliptical horizontal cross section with respect to the electrode terminal. The method of claim 1, wherein the secondary battery is a lithium secondary battery. 2. The method of claim 1, wherein the primary activation is performed by charging with a low C-rate and / or a multistage process. A battery cell characterized by being manufactured by the method according to any one of claims 1 to 9. A battery pack comprising at least one battery cell according to claim 10. A device comprising a battery pack according to claim 11. 13. The device of claim 12, wherein the device is at least one of a notebook computer, a mobile phone, a PDP, a PMP, an MP3 player, a digital still camera (DSC), a DVR, a smart phone, a GPS system, a camcorder, an electric vehicle, a hybrid electric vehicle, , And a power storage device.

Images