Secondary battery manufacturing method and secondary battery

Abstract

The present application relates to a method for manufacturing a secondary battery, and a secondary battery, which can minimize the influence of an electrolyte.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0183553 filed with the Korean Intellectual Property Office on December 21, 2021, and all of the contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present application relates to a method for manufacturing a secondary battery and a secondary battery that can minimize the influence of an electrolyte. [Background technology]

[0003] The rapid increase in fossil fuel use has led to an increasing demand for alternative and clean energy, and one of the most actively researched fields in this area is the field of power generation and storage using electrochemical reactions.

[0004] Currently, a representative example of an electrochemical element that uses such electrochemical energy is a secondary battery, which includes various types such as nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium-ion batteries, and as mobile devices become more widespread, the range of their use is expanding.

[0005] Among these, lithium-ion secondary batteries are attracting attention as a driving power source for mobile devices due to their excellent properties such as rechargeability, light weight, long life, and high capacity, which has led to active research and development efforts in lithium-ion secondary batteries.

[0006] Lithium-ion secondary batteries have the risk of explosion due to the highly reactive nature of lithium. There are various causes of lithium-ion secondary battery explosions, but one of them is an increase in internal gas pressure. Specifically, when the electrodes are overcharged, overdischarged, or overcurrented, the electrodes heat up or ignite, generating gas inside the secondary battery. The generated gas increases the internal pressure of the secondary battery, potentially causing an explosion.

[0007] To prevent explosion due to heat generation or fire of the electrodes of the secondary battery, a battery exterior cap is generally placed on the top of the cylindrical secondary battery and sealed by a method such as welding, thereby maintaining the secondary battery in a sealed state and preventing the electrolyte and generated gas from leaking out.

[0008] When sealing the battery exterior cap, if electrolyte remains in the gaps between the assembled parts, there is a risk of it leading to poor welding of the secondary battery. Conventionally, after the battery exterior cap is attached to the battery exterior material, a low-power laser is irradiated to evaporate and remove the remaining electrolyte around it, and then the seal is welded.

[0009] In the conventional method, after the step of evaporating and removing the residual electrolyte, the electrolyte may leak out during the delay time between the main sealing and welding steps, resulting in the problem of poor welding. Therefore, there is a need for a method of manufacturing a secondary battery that can effectively remove the residual electrolyte that causes poor welding of the secondary battery and minimize its effects. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Korean Patent Publication No. 10-2005-0080516 Summary of the Invention [Problem to be solved by the invention]

[0011] The present application relates to a method for manufacturing a secondary battery and a secondary battery that can minimize the influence of an electrolyte. [Means for solving the problem]

[0012] One embodiment of the present invention provides a method for manufacturing a secondary battery, including the steps of inserting a battery assembly into a battery exterior material; injecting an electrolyte into the battery exterior material; placing a battery exterior cap having electrodes in an opening of the battery exterior material; and welding and sealing the battery exterior cap in a circular track, wherein the sealing step includes the steps of forming a spot-shaped or tail-shaped welding track start portion on the battery exterior cap; and welding along a circular track from the welding track start portion.

[0013] In yet another embodiment, there is provided a secondary battery including: a battery exterior material into which a battery assembly is inserted; a battery exterior cap provided at an opening of the battery exterior material; and a welding portion that seals the battery exterior material and the battery exterior cap, wherein the battery exterior cap is circular, the welding portion is welded along a circular orbit of the battery exterior cap, and the welding portion includes a spot-shaped or tail-shaped welding orbit starting portion. [Effects of the Invention]

[0014] In the method for manufacturing a secondary battery according to one embodiment of the present invention, a spot-shaped or tail-shaped welding track start portion is included within the circular welding track of the battery outer cap, and welding is performed along a circular track.

[0015] By starting welding from a location away from the circular orbit to be sealed, the electrolyte in the gap between the battery exterior material and the battery exterior cap assembly is evaporated and removed, allowing for simultaneous sealing and welding without time delay, which has the advantage of effectively minimizing the influence of residual electrolyte during the sealing and welding of the secondary battery. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram showing a tail-shaped welding track start portion of a welding track for welding a battery outer cap according to one embodiment of the present application. [Figure 2]1 is a diagram showing a spot-shaped welding track start portion of a welding track for welding a battery exterior cap according to one embodiment of the present application. FIG. [Figure 3] FIG. 2 is an enlarged view of a welded portion of a battery exterior cap according to one embodiment of the present application. [Figure 4] 1 is an enlarged view of a welded portion of a battery exterior cap welded by a conventional method, without including a tail-shaped or spot-shaped weld track initiation portion according to the present application. [Figure 5] 1 is an enlarged view of a state in which a battery exterior cap according to the present application is placed in an opening of a battery exterior material before being sealed. [Figure 6] FIG. 10 is a close-up view of a tail weld track start according to one embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0017] Before describing the present invention, some terms will first be defined.

[0018] In this specification, when a part is said to "comprise" a certain component, this means that it may further include other components, rather than excluding other components, unless otherwise specified to the contrary.

[0019] In this specification, "p to q" means a range of "not less than p and not more than q."

[0020] DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand the present invention. However, the present invention may be embodied in many different forms and is not limited to the following description.

[0021] A method for manufacturing a secondary battery according to one embodiment of the present invention includes the steps of inserting a battery assembly into a battery exterior material; injecting an electrolyte into the battery exterior material; placing a battery exterior cap having electrodes in an opening of the battery exterior material; and welding and sealing the battery exterior cap in a circular orbit, wherein the sealing step includes the steps of forming a spot-shaped or tail-shaped welding orbit start portion on the battery exterior cap; and welding along a circular orbit from the welding orbit start portion.

[0022] A method for manufacturing a secondary battery according to one embodiment of the present invention includes inserting a battery assembly into a battery exterior material.

[0023] In the step of inserting the battery assembly into the battery casing, the shape of the battery casing may be various shapes such as a cylindrical shape, a square shape, a pouch shape, etc., and preferably a cylindrical shape.

[0024] In the step of inserting the battery assembly into the battery exterior material, the battery assembly may be a chargeable and dischargeable power generating element, and may include a positive electrode, a negative electrode, and a separator.

[0025] The battery assembly may be formed by alternately stacking positive electrodes, separators, and negative electrodes, for example, by folding the separator in a zigzag pattern and alternately disposing the positive electrodes and negative electrodes between the folded separators.

[0026] The positive electrode may include a positive electrode current collector layer and a positive electrode active material layer, and the positive electrode active material layer may include a positive electrode active material.

[0027] The material of the positive electrode current collector layer is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used. Fine irregularities may be formed on the surface of the current collector to enhance the adhesive force of the positive electrode active material. For example, it may be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0028] The positive electrode active material may be a commonly used positive electrode active material. The positive electrode active material is a compound capable of reversible insertion and extraction of lithium. Specifically, it may include a lithium transition metal composite oxide containing at least one transition metal composed of nickel, cobalt, manganese, and aluminum and lithium. More specifically, the lithium transition metal composite oxide may contain a transition metal containing nickel, cobalt, and manganese and lithium. Specifically, examples of the lithium transition metal composite oxide include lithium-manganese-based oxides (such as LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (such as LiCoO2, etc.), lithium-nickel-based oxides (such as LiNiO2, etc.), lithium-nickel-manganese-based oxides (such as LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (such as LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (such as LiCo[[ID=十七]] 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (such as Li(Ni p Co q Mn r1)O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are, as atomic fractions of independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc.), etc. Any one or two or more of these compounds may be included. Among these, in terms of being able to enhance the capacity characteristics and safety of the battery, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel-manganese-cobalt oxide (e.g., Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), etc. may be used. When considering the remarkable improvement effect by controlling the types and content ratios of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide is Li(Ni 0.6 [[ID=​​​​​​​​​​​​0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc., and a mixture of any one or more of these may be used.

[0029] The negative electrode may include a negative electrode current collector layer and a negative electrode active material layer, and the negative electrode active material layer may include a negative electrode active material.

[0030] The material for the negative electrode current collector layer is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. Furthermore, the surface may be formed with fine irregularities to strengthen the binding force of the negative electrode active material, and the negative electrode current collector layer may be used in various forms such as a film, sheet, foil, mesh, porous material, foam, nonwoven fabric, etc.

[0031] The negative electrode active material may be a commonly used negative electrode active material or a compound capable of reversible intercalation and deintercalation. Specifically, the negative electrode active material may be a single material selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material capable of alloying with lithium, and a lithium-containing nitride, or a mixture of two or more of these materials.

[0032] The carbon-based active material may include artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, acetylene black, Ketjen black, Super P, graphene, and fibrous carbon.

[0033] The silicon-based active material may include silicon, an alloy of silicon, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, or a compound represented by SiOx (0 < x < 2).

[0034] The metal-based active material may include Al, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt, Ti, Sb, Ga, Mn, Fe, Co, Ni, Cu, Sr, or Ba, etc. These may be used in any form such as a single substance, an alloy, an oxide, a nitride, a sulfide, a boride, or an alloy with lithium.

[0035] The positive electrode active material layer and the negative electrode active material layer may further include a conductive material and a binder.

[0036] The conductive material is used to impart conductivity to the electrode and can be used without particular limitation as long as it does not induce a chemical change and has conductivity in the battery being constructed. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more thereof may be used.

[0037] The binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, propylene polymer, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0038] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitations. It is particularly preferable that the separator exhibits low resistance to electrolyte ion migration and has excellent electrolyte humidifying ability. Specifically, porous polymer films, such as those made from polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminate structures of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric material may be used, and it may be selectively used as a single-layer or multi-layer structure.

[0039] A method for manufacturing a secondary battery according to one embodiment of the present invention includes a step of injecting an electrolyte solution into the battery exterior material.

[0040] In the step of injecting an electrolytic solution into the battery exterior material, examples of the electrolytic solution that can be used in manufacturing a lithium secondary battery include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes.

[0041] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0042] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0043] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte solution. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 -, CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0044] In addition to the constituent components of the electrolyte, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0045] A method for manufacturing a secondary battery according to one embodiment of the present invention includes a step of placing a battery exterior cap provided with electrodes in an opening of a battery exterior material.

[0046] In the step of placing a battery exterior cap provided with electrodes in the opening of the battery exterior material, the battery exterior cap is placed so as to completely cover the opening of the battery exterior material.

[0047] In the step of placing a battery exterior cap with an electrode in the opening of the battery exterior material, the battery exterior cap may be circular, and the pattern of the battery exterior cap may match the pattern of the opening of the battery exterior material.

[0048] 5 is an enlarged view of the battery exterior cap placed on the opening of the battery exterior material before sealing it. In the enlarged view, a gap between the battery exterior cap and the battery exterior material can be seen.

[0049] A method for manufacturing a secondary battery according to an embodiment of the present invention includes a step of sealing the battery exterior cap by welding it in a circular orbit.

[0050] The step of welding and sealing the battery exterior cap in a circular trajectory includes the steps of forming a spot-shaped or tail-shaped welding trajectory start portion on the battery exterior cap, and welding along a circular trajectory from the welding trajectory start portion.

[0051] A method for manufacturing a secondary battery according to one embodiment of the present invention includes a step of forming a spot-shaped or tail-shaped welding track start portion on a battery exterior cap.

[0052] In the step of forming a spot-shaped or tail-shaped welding track starting portion on the battery exterior cap, the tail-shaped welding track starting portion may be formed inside the sealing circular track of the exterior cap, as shown in FIG.

[0053] In the step of forming a spot-shaped or tail-shaped welding track starting portion on the battery exterior cap, the spot-shaped welding track starting portion may be formed inside the sealing circular track of the exterior cap, as shown in FIG. 2.

[0054] As described above, in the method for manufacturing a secondary battery according to the present invention, a spot-shaped or tail-shaped welding track start portion is formed on the battery exterior cap apart from the circular sealing track, and the electrolyte in the gap between the battery exterior material and the battery exterior cap assembly can be evaporated and removed by the conductive heat generated thereby.

[0055] A method for manufacturing a secondary battery according to one embodiment of the present invention includes a step of welding along a circular trajectory from a welding trajectory start portion.

[0056] The step of welding along a circular track from the welding track start portion is a step of welding along a circular track that enables sealing of a gap between the battery exterior material and the battery exterior cap assembly.

[0057] In the step of welding along the circular trajectory from the welding trajectory start portion, a general welding method for sealing a secondary battery may be used.

[0058] 1 and 2 show a circular track that is welded from a tail or spot welding track start.

[0059] If electrolyte remains in the gaps between the assembled parts of a secondary battery, there is a risk of poor welding of the secondary battery. Conventionally, this has been achieved by joining a battery exterior cap to a battery exterior material, irradiating a low-power laser to evaporate and remove the surrounding residual electrolyte, and then sealing and welding. In the conventional method, electrolyte can leak out during the delay between the step of evaporating and removing the residual electrolyte and the actual sealing and welding step, which still results in poor welding.

[0060] However, in the present invention, a spot-shaped or tail-shaped welding track start portion is formed on the battery exterior cap, so that the electrolyte in the gap between the battery exterior material and the battery exterior cap assembly is removed, and welding can be performed along a circular track from the welding track start portion without time delay, thereby minimizing the influence of residual electrolyte.

[0061] In the method for manufacturing a secondary battery according to an embodiment of the present invention, the step of welding and sealing the battery exterior cap along a circular track may use laser welding.

[0062] In the method for manufacturing a secondary battery according to an embodiment of the present invention, after the step of forming the welding track start portion, the ambient temperature of the welding track start portion of the battery outer cap may be 50°C or more and 2000°C or less.

[0063] In another embodiment of the method for manufacturing a secondary battery, the temperature around the welding track start portion of the battery outer cap in the step of forming the welding track start portion may be 50°C or higher and 1700°C or lower.

[0064] In another embodiment of the method for manufacturing a secondary battery, the temperature around the welding track start portion of the battery outer cap in the step of forming the welding track start portion may be 50°C or higher and 1400°C or lower.

[0065] In another embodiment of the method for manufacturing a secondary battery, the temperature around the welding track start portion of the battery outer cap in the step of forming the welding track start portion may be 50°C or higher and 1100°C or lower.

[0066] In another embodiment of the method for manufacturing a secondary battery, the temperature around the welding track start portion of the battery outer cap in the step of forming the welding track start portion may be 50°C or higher and 800°C or lower.

[0067] In another embodiment of the method for manufacturing a secondary battery, the ambient temperature of the welding track start portion of the battery outer cap in the step of forming the welding track start portion may be 50°C or higher and 500°C or lower.

[0068] The vicinity of the welding track start portion of the battery exterior cap refers to a portion where heat is transferred to the vicinity of the welding track start portion when the welding track start portion is formed on the battery exterior cap by laser welding.

[0069] In the step of forming the welding track start portion, the temperature of the battery exterior cap is increased by the heat of conduction generated during welding, and the electrolyte is evaporated and removed.

[0070] In a method for manufacturing a secondary battery according to an embodiment of the present invention, the laser welding may have a laser wavelength in the range of 100 nm to 1500 nm, which can effectively remove residual electrolyte and seal the can without damaging the inside of the can, such as damaging the separator.

[0071] In the method for manufacturing a secondary battery according to an embodiment of the present invention, the laser energy for laser welding may be 0.01 J or more and 150 J or less. The laser energy may be changed depending on conditions such as the laser pulse width, and is not limited to the above energy.

[0072] In the method for manufacturing a secondary battery according to an embodiment of the present invention, the laser speed for laser welding may be 10 mm / sec or more and 10,000 mm / sec or less. The welding speed may be adjusted depending on conditions such as the laser output and wavelength, and is not limited to the above speed.

[0073] A secondary battery according to one embodiment of the present invention is a secondary battery including: a battery exterior material into which a battery assembly is inserted; a battery exterior cap provided at an opening of the battery exterior material; and a welded portion that seals the battery exterior material and the battery exterior cap; wherein the battery exterior cap is circular, the welded portion is welded along a circular orbit of the battery exterior cap, and the welded portion includes a spot-shaped or tail-shaped weld orbit starting portion.

[0074] FIG. 3 shows a welding track and an enlarged view thereof according to one embodiment of the present invention.

[0075] FIG. 4 is a diagram showing welding defects caused by existing welding methods.

[0076] In the secondary battery according to one embodiment of the present invention, the size of the spot-shaped welding track start portion may be 1 μm or more and 1000 μm or less.

[0077] In the secondary battery according to one embodiment of the present invention, the tail-shaped welding track start portion may have a size of 1 μm or more and 1000 μm or less.

[0078] The size of the spot-shaped and tail-shaped weld track start portions refers to the size of the weld bead formed by laser welding. For example, Figure 6 is an enlarged view of a tail-shaped weld track start portion according to one embodiment of the present invention, and it can be seen that the size of the weld bead, i.e., the size of the weld track start portion, is 230 μm.

[0079] In the secondary battery according to an embodiment of the present invention, the term "weld bead" refers to a deposited metal formed on a base material to be welded by welding.

[0080] As described above, the present invention relates to a method for welding along a circular track including a spot-shaped or tail-shaped welding track initiation portion within the circular welding track of a battery exterior cap, and a secondary battery formed by the same.

[0081] By starting welding from a location away from the circular orbit to be sealed, the electrolyte in the gap between the battery exterior material and the battery exterior cap assembly is evaporated and removed, allowing for simultaneous sealing and welding without time delay, which effectively minimizes the impact of residual electrolyte during the sealing and welding of the secondary battery.

[0082] Hereinafter, examples are provided to specifically explain the present specification. However, the examples according to the present specification may be modified in other ways, and the scope of the present application is not limited to the following examples. The examples of the present application are provided to more completely explain the present specification to those skilled in the art.

[0083] Example 1 1) Insert the battery assembly into the battery exterior. The positive electrode slurry was applied to an aluminum thin film (positive electrode current collector), dried, and rolled to form a positive electrode. The negative electrode slurry was applied to a copper thin film (negative electrode current collector), dried, and rolled to form a negative electrode. The positive electrode, separator, and negative electrode were sequentially stacked to form a battery assembly, which was then inserted into an exterior housing.

[0084] 2) Inject electrolyte into the battery exterior An electrolyte solution was injected into the battery exterior material into which the battery assembly was inserted.

[0085] 3) A battery exterior cap equipped with electrodes is placed over the opening of the battery exterior material. The battery exterior cap was circular, matched in shape to the opening of the battery exterior material, and was placed so as to cover the opening of the battery exterior material.

[0086] 4) The battery outer cap is welded and sealed in a circular orbit. A tail-shaped welding track start was formed inside the circular sealing welding track of the battery outer cap (laser power 60 W, processing speed 70 mm / s, wavelength 1060 nm). As can be seen in Figure 6, the size of the tail-shaped start was 230 μm.

[0087] Next, laser welding was performed from the tail-shaped welding track start point along the circular track at an output of 60 W, a processing speed of 70 mm / s, and a wavelength of 1060 nm, to seal the battery exterior cap to the battery exterior material.

[0088] FIG. 3 shows an enlarged view of the welded portion of a secondary battery, including the tail-shaped welding track start portion that has been sealed and completed.

[0089] <Comparative Example 1> A secondary battery was manufactured in the same manner as in the example, except that the residual electrolyte was removed with a low-power (15 W) laser instead of forming a welding track start portion on the battery exterior cap.

[0090] FIG. 4 is an enlarged view of a welded portion of the secondary battery.

[0091] 5 is an enlarged view of the battery exterior cap placed on the opening of the battery exterior material before sealing. In the enlarged view, a gap between the battery exterior cap and the battery exterior material can be seen. When the welding track start portion according to the present invention is not formed and the electrolyte is removed by evaporation using a conventional low-power laser (Comparative Example 1), holes are observed in the weld due to the residual electrolyte in the gap between the battery exterior material and the battery exterior cap, as shown in FIG. 4, preventing proper bead formation and resulting in poor sealing.

[0092] On the other hand, when a tail-shaped welding track start point was formed according to the present invention and the electrolyte was removed using the heat conduction generated by the start point (Example 1), as can be seen in Figure 3, the gap between the battery exterior material and the battery exterior cap could be sealed without being affected by the residual electrolyte.

Claims

1. Inserting the battery assembly into the battery housing; Injecting an electrolyte solution into the battery exterior material; Placing a battery exterior cap provided with an electrode in the opening of the battery exterior material; and the battery exterior cap is sealed by welding in a circular track. A method for manufacturing a secondary battery, comprising: the sealing step includes the steps of: forming a spot-shaped or tail-shaped welding track start portion on the battery exterior cap; and welding along a circular track from the welding track start portion; The welding orbit start portion is located inside the circular orbit. Secondary battery manufacturing method.

2. The method of manufacturing a secondary battery according to claim 1 , wherein the sealing step utilizes laser welding.

3. The method of manufacturing a secondary battery according to claim 1 , wherein the ambient temperature of the welding track start portion of the battery outer cap after the step of forming the welding track start portion is 50° C. or more and 2000° C. or less.

4. The method for manufacturing a secondary battery according to claim 2 , wherein the laser welding has a laser wavelength in the range of 100 nm to 1500 nm.

5. 3. The method for manufacturing a secondary battery according to claim 2, wherein the laser energy of the laser welding is 0.01 J or more and 150 J or less.

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