KR101830286B1 - Battery Cell Preparation Method Pressurizing Electrode Assembly During Vitalization Process - Google Patents

Abstract

A method for manufacturing a battery cell having a structure in which an electrode assembly having a separator interposed between an anode and a cathode is sealed in a battery case, the method comprising the steps of: (a) mounting an electrode assembly inside a battery case; (b) pressing the outer surface of the battery case with a pressing member to induce linear pressure on the electrode assembly; (c) performing charging for activation of the battery cell; (d) pressing the outer surface of the battery case by a pressing member after the charging process to induce linear pressure on the electrode assembly; And (e) performing a discharge for activation of the battery cell; The method of manufacturing a battery cell according to the present invention includes the steps of:

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery cell manufacturing method for pressurizing an electrode assembly during an activation process,

The present invention relates to a method of manufacturing a battery cell that pressurizes an electrode assembly during an activation process.

As technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries capable of meeting various demands have been conducted.

Typically, in terms of the shape of a battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery which can be applied to products such as mobile phones with a small thickness, and has advantages such as high energy density, discharge voltage, There is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries.

Also, the secondary battery is classified according to how the electrode assembly having the anode / separator / cathode structure is formed. Typically, the long battery-shaped anodes and cathodes are jelly- A stacked (stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, a stacked (stacked) electrode assembly in which a predetermined unit of positive and negative electrodes are stacked, A stack / folding type electrode assembly in which a Bi-cell or a full cell stacked in a single state is wound up as a separation film can be given.

Recently, a pouch-shaped battery having a structure in which a stacked or stacked / folded electrode assembly is embedded in a pouch-shaped battery case of an aluminum laminate sheet is attracting much attention due to low manufacturing cost, small weight, Its usage is also gradually increasing.

FIG. 1 schematically shows a general structure of a typical conventional pouch-type secondary battery as an exploded perspective view.

1, the pouch type secondary battery 10 includes an electrode assembly 30, electrode taps 40 and 50 extending from the electrode assembly 30, electrodes 40 and 50 welded to the electrode taps 40 and 50, Leads 60 and 70, and a battery case 20 for accommodating the electrode assembly 30. [

The electrode assembly 30 is a power generation element in which an anode and a cathode are sequentially stacked with a separation membrane interposed therebetween. The electrode assembly 30 has a stacked or stacked / folded structure. The electrode tabs 40 and 50 extend from each electrode plate 30 of the electrode assembly 30 and the electrode leads 60 and 70 are connected to a plurality of electrode tabs 40 and 50 extending from each electrode plate, Respectively, and a part of the battery case 20 is exposed to the outside. An insulating film 80 is attached to the upper and lower surfaces of the electrode leads 60 and 70 in order to increase the degree of sealing with the battery case 20 and at the same time to ensure an electrically insulated 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. 1, a plurality of positive electrode taps 40 and a plurality of negative electrode tabs 50 may be coupled to the electrode leads 60 and 70. In the stacked electrode assembly 30, The upper end is spaced from the electrode assembly 30.

Generally, a lithium secondary battery is activated during the manufacturing process of a battery, and the activation process includes applying a current to a predetermined voltage to an electrode assembly impregnated with an electrolyte. In the initial charging / discharging process for such activation, a protective film is formed on the surface of the electrode, and a part of the electrolytic solution is decomposed to generate a large amount of gas.

In the activation process, when the battery is charged, the anode is oxidized to insert lithium ions into the cathode. During the discharge, the cathode is oxidized and lithium ions are inserted into the anode. In the course of charging lithium ions into the cathode The overall thickness of the lithium secondary battery is increased due to the expansion of the negative electrode, and the internal resistance is also increased due to the increase in thickness. Thus, the performance of the secondary battery is deteriorated.

Therefore, there is a high need for a technique capable of fundamentally solving such problems.

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

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a battery cell having a structure in which an electrode assembly is sealed inside a battery case and a method of manufacturing a battery cell in which an outer surface of a battery case is pressed before charging and discharging for activating a battery cell, It is possible to minimize the change in the thickness of the electrode assembly that can occur during the activation process, thereby reducing the resistance inside the battery cell, efficiently removing the gas remaining in the electrode assembly, and improving the electrolyte penetration ability And to provide a battery cell manufacturing method.

It is still another object of the present invention to provide a method of manufacturing a battery cell that can improve the yield and ensure a high yield.

In order to accomplish the above object, the present invention provides a method of manufacturing a battery cell having a structure in which an electrode assembly having a separator interposed between an anode and a cathode is sealed inside a battery case,

(a) a process of mounting an electrode assembly inside a battery case;

(b) pressing the outer surface of the battery case with a pressing member to induce linear pressure on the electrode assembly;

(c) performing charging for activation of the battery cell;

(d) pressing the outer surface of the battery case by a pressing member after the charging process to induce linear pressure on the electrode assembly; And

(e) performing a discharge for activation of the battery cell;

As shown in Fig.

As described above, during the activation process of the battery cell, the anode is oxidized and lithium ions are inserted into the cathode during charging. When the battery is discharged, the cathode is oxidized and lithium ions are inserted into the anode. The negative electrode expands in the process of inserting the negative electrode into the negative electrode, and the overall thickness of the lithium secondary battery is increased. As a result of this increase in the thickness, the resistance of the battery is also increased.

Meanwhile, the method of manufacturing a battery cell according to the present invention includes a step of applying a linear pressure to an electrode assembly by pressing an outer surface of a battery case before a charging and discharging process for activating the battery cell, The thickness variation of the assembly is minimized, and the resistance inside the battery cell can be reduced.

In this pre-pressure induction process, a linear pressure can be formed between the stacked or wound electrodes through the process of pressing the outer surface of the battery case using the pressure member, and the pressure of the electrode assembly The thickness increase due to the expansion of the negative electrode can be minimized, so that the resistance inside the battery cell can also be reduced.

In addition, the gas remaining in the electrode assembly can be efficiently removed through the pre-pressure induction process, and the electrolyte penetration ability can be improved.

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 stacked structure and a stacked / folded structure. Details of the stacked / folded structure of the electrode assembly are disclosed in Korean Patent Application Laid-Open Nos. 2001-0082058, 2001-0082059 and 2001-0082060, the contents of which are incorporated herein by reference. As a reference.

The secondary battery according to the present invention can be suitably applied to a pouch-type secondary battery in which an electrode assembly is embedded in a laminate sheet including a metal layer and a resin layer, and in one specific example, a pouch-shaped case of an aluminum laminate sheet .

2. Description of the Related Art Generally, a pouch-type secondary battery has a structure in which an electrode assembly is housed in a storage portion of a pouch-shaped battery case made of, for example, an aluminum laminate sheet. That is, the pouch type secondary battery includes a laminated sheet having a receiving portion for mounting the electrode assembly, a separate sheet separated from the sheet in a state where the electrode assembly is mounted on the receiving portion, or a sheet extending therefrom, And then sealing it.

For example, the pressure member may include a pair of pressure rollers, and may be formed by passing a battery cell between the pressure rollers, It is preferable that the outer surface of the case is pressed.

Specifically, the pressure rollers have a cylindrical structure, and the length of the long axis of the pressure roller is at least equal to the length of the short axis of the battery case. In the process of passing the battery cells through the pressure rollers, And a constant pressure may be applied to the pressure-sensitive adhesive layer.

In this structure, it is preferable that the pressure rollers are positioned on the same plane perpendicular to the direction in which the battery cells pass.

The pressure of the pressure member is preferably in the range of 0.1 MPa or more to 0.3 MPa or less, and if the pressure range is excessively high, the electrode assembly and the outer surface of the battery case may be damaged, which is undesirable. If it is too low, a line pressure of a desired size can not be induced in the electrode assembly, which is undesirable.

On the other hand, in the case of an electrode assembly having a stacked or stacked / folded structure composed of an anode, a cathode and a separator, a process of laminating the electrode and the separator, or a process of laminating and winding the electrode on the separator, Due to various causes, minute breakage may occur in the separator inside the battery cell, and the electrode having the same polarity is brought into contact with the interface at such an interface due to such defects, thereby causing deterioration in performance of the battery.

Generally, in order to solve such a problem, a method is employed in which a flat surface of a completed battery cell is pressed and a current is applied to induce a short circuit of an electrode exposed from the separator to select a defect or not. In the case of inducing the line pressure to the assembly, it is preferable because the failure of the electrode exposure can be effectively selected.

The present invention further includes a step of checking whether the electrode assembly is short-circuited after the step (b) or (d), as well as the defect selection for the completed battery cell, It is also possible.

On the other hand, as described above, when an activation process is performed during the manufacturing process of the battery cell, a protective film is formed on the surface of the electrode, and a part of the electrolyte may be decomposed to generate a large amount of gas.

Therefore, it is possible to further include a process of removing the gas generated in the charging / discharging process for activation after the step (e).

In addition, aging may occur between the activating processes of the process (c) and the process (e) because some metal may elute during the activation process depending on the active material used, So as to prevent the above-described problems.

Specifically, the aging process may include a normal temperature aging process and a high temperature aging process, and the room temperature aging process is preferably performed at a temperature of 18 ° C. to 27 ° C., and the high temperature aging process is performed at a temperature of 50 ° C. Deg.] C to 70 [deg.] C or less.

The present invention also provides a battery cell manufactured by the method for manufacturing a battery cell, wherein the battery cell may be selected from the group consisting of a lithium ion battery, a lithium polymer battery, and a lithium ion polymer battery.

For reference, a lithium ion battery is composed of a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte solution 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; _{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 < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{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 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, 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.

The present invention can also provide a battery pack including at least one battery cell and the battery pack as a power source. The device can be used for a mobile phone, a portable computer, a wearable electronic device, And may be one selected from the group consisting of a fleet PC, a smart pad, a netbook, a light electronic vehicle (LEV), an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device.

The structure of these devices and their fabrication methods are well known in the art, and a detailed description thereof will be omitted herein.

As described above, the method for manufacturing a battery cell according to the present invention is a method for manufacturing a battery cell having a structure in which an electrode assembly is sealed inside a battery case, And the outer surface of the electrode assembly is pressurized to induce a linear pressure on the electrode assembly, thereby minimizing the thickness variation of the electrode assembly that may occur during the activation process, thereby reducing the resistance inside the battery cell, So that it is possible to improve the electrolyte penetration ability.

1 is an exploded perspective view of a general structure of a conventional battery cell;
2 to 5 are schematic views illustrating a method of manufacturing a battery cell 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.

2 to 5 are schematic views illustrating a method of manufacturing a battery cell according to an embodiment of the present invention.

The electrode assembly 100 having the structure in which the separator 121 is interposed between the anode 111 and the cathode 131 is sealed inside the battery case 140 A method of manufacturing a battery cell having a structure in which an electrode assembly 100 is mounted in a battery case 140 is manufactured by pressing the outer surface of the battery case 140 with the pressure rollers 151 and 152, A process of charging a battery cell to activate the battery cell, a process of introducing a linear pressure to the electrode assembly 100, a process of charging the battery cell to activate the battery cell, a process of charging the battery cell by the pressure roller 151, And a discharging process for activating the battery cell.

The electrode assembly 100 includes a stacked electrode assembly 100 having a structure in which a pair of cathodes 131, a separator 121 and anodes 111 are stacked in order, As shown in Fig.

The battery cell having such a structure leads the linear pressure to the structure that presses the outer surface of the battery case 140 by passing the battery cell between the pair of pressure rollers 151 and 152. The pressure rollers 151 and 152 Is a cylindrical structure and is positioned on the same plane perpendicular to the direction in which the battery cells pass, so that a constant pressure is applied to the entire outer surface of the battery case 140 in the course of passing through the battery cells between the pressure rollers 151 and 152 .

2, the pair of pressure rollers 151 and 152 are moved from one side of the battery cell to the other side of the battery cell before the charging process for activation. The cathode 131 and the separator 121 which are stacked through the process of passing the battery cell between the pressure rollers 151 and 152 are applied.

After the first linear pressure induction is induced by using a pair of pressure rollers 151 and 152, a charging process for activation is performed. When the current is applied, the anode 111 is oxidized so that lithium ions are inserted into the cathode 131, As the lithium ions are inserted into the cathode 131 during charging, the cathode 131 expands to a certain level. As shown in FIG. 4, for the electrode assembly 100 including the expanded cathode 132, And the second linear pressure is induced by using the pressure rollers 151 and 152.

After the second linear pressure is induced by using the pressure rollers 151 and 152, the discharge for activation is performed, and the pressure rollers 151 and 152 are pressed against the electrode assembly 100 during the activation process It is possible to prevent the deterioration of the overall battery cell performance due to the excessive increase in the thickness of the negative electrode when the conventional activation process is performed.

The battery cell manufacturing method shown in FIGS. 2 to 5 is described as including a linear pressure induction process and an activation process for the stacked electrode assembly, but it is also applicable to a stack / folding type electrode assembly.

In addition, although it is described that only the activation process is performed to indicate the linear pressure induction for the electrode assembly, it may further include a process of checking whether the electrode assembly is short-circuited immediately after the process of inducing the linear pressure. It is also possible to further include a process of removing the gas generated in the charging / discharging process for activation.

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 (19)

A method of manufacturing a battery cell having a structure in which an electrode assembly having a separator interposed between an anode and a cathode is sealed inside a battery case,
(a) a process of mounting an electrode assembly inside a battery case;
(b) pressing the outer surface of the battery case with a pressing member to induce linear pressure on the electrode assembly;
(c) performing charging for activation of the battery cell;
(d) pressing the outer surface of the battery case by a pressing member after the charging process to induce linear pressure on the electrode assembly; And
(e) performing a discharge for activation of the battery cell;
And sequentially proceeds the process,
Wherein the pressing member is composed of a pair of pressure rollers and presses the outer surface of the battery case by passing the battery cell through the pressing rollers and the pressing force is within a pressure range of 0.1 MPa or more to 0.3 MPa or less. ≪ / RTI > The method of claim 1, wherein the electrode assembly is of a stacked, stacked-fold, or lamination-stacked structure. The method of claim 1, wherein the battery case comprises a laminate sheet including a resin layer and a metal layer. The method for manufacturing a battery cell according to claim 3, wherein the laminate sheet is an aluminum laminate sheet. delete The method of claim 1, wherein the pressure rollers have a cylindrical shape, and the length of the major axis of the pressure roller is at least equal to the length of the minor axis of the battery case. The method of claim 1, wherein the pressure rollers are positioned on the same plane perpendicular to the direction in which the battery cells pass. delete The method of claim 1, further comprising, after step (b) or step (d), checking whether the electrode assembly is short-circuited. The method of claim 1, further comprising removing gas generated during a charge / discharge process for activation after the step (e). The method of claim 1, further comprising aging between the activation of the process (c) and the activation of the process (e). 12. The method of claim 11, wherein the aging process comprises a room temperature aging process and a high temperature aging process. [13] The method of claim 12, wherein the room temperature aging is performed at a temperature of 18 [deg.] C to 27 [deg.] C. 13. The method of claim 12, wherein the high-temperature aging process is performed at a temperature greater than 50 degrees Celsius and less than 70 degrees Celsius. A battery cell characterized by being manufactured by the method according to any one of claims 1 to 4, 6 to 7, and 9 to 14. 16. The battery cell of claim 15, wherein the battery cell is one selected from the group consisting of a lithium ion battery, a lithium polymer battery, and a lithium ion polymer battery. A battery pack comprising at least one battery cell according to claim 16. A device according to claim 17, wherein the battery pack is used as a power source. 19. The device of claim 18, wherein the device is selected from the group consisting of a mobile phone, a portable computer, a wearable electronic device, a tablet PC, a smart pad, a netbook, a LEV (Light Electronic Vehicle), an electric vehicle, a hybrid electric vehicle, And a storage device.

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