Preparation method of lithium-ion battery, lithium-ion battery and lithium-ion battery module

Abstract

The present application discloses a method for preparing a lithium-ion battery, a lithium-ion battery, and a lithium-ion battery module. The preparation method may include: S1, providing an electrode plate, and connecting a first electrode tab to the electrode plate to obtain an electrode unit precursor; S2, soaking the electrode unit precursor in an electrolyte solution to form an electrolyte layer on the surface of the electrode plate; S3, providing a second electrode tab connected to the first electrode tab to form a composite electrode tab; S4, connecting a tab connector to the composite electrode tab to obtain an electrode unit; S5, forming the lithium-ion battery. The present application improves the connection strength between the tab and the electrode plate by forming a composite electrode tab, thereby improving the manufacturing qualification rate and long-term reliability of the lithium-ion battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a lithium-ion battery and a preparation method thereof, as well as a lithium-ion battery module having the lithium-ion battery. Background Art

[0002] Lithium-ion batteries, with their significant advantages such as high energy density, long cycle life, and low self-discharge, have garnered widespread attention in the new energy vehicle sector in recent years. Eutectic electrolytes, used in lithium-ion batteries, are low-temperature molten salt or liquid electrolyte systems formed by a eutectic reaction between two or more components. With a significantly lower melting point than a single component, they combine high ionic conductivity with a wide electrochemical window, making them an emerging electrolyte in the battery field. To form the eutectic electrolyte, the electrode and tab are immersed in an electrolyte solution to induce a eutectic reaction. However, after immersion, the tabs are prone to separation. As the key connecting component between the battery's internal electrodes and the external circuit, the quality and mechanical stability of the tab welds directly impact the battery's electrical conductivity, cycle life, and safety. Therefore, ensuring the quality and mechanical stability of the tab welds while allowing the eutectic reaction to form the eutectic electrolyte is a critical issue in lithium-ion battery manufacturing. Summary of the Invention

[0003] To achieve the above objectives, the present application discloses a method for preparing a lithium-ion battery, a lithium-ion battery, and a lithium-ion battery module. The lithium-ion battery includes a laminated composite tab structure, thereby preventing the risk of tab detachment causing a battery short circuit, thereby improving the manufacturing qualification rate and long-term reliability of the battery.

[0004] On the one hand, the present application provides a method for preparing a lithium-ion battery, which may include: S1, providing an electrode plate, and connecting a first electrode tab to the electrode plate to obtain an electrode unit precursor; the electrode plate includes an electrode layer and a current collector layer; S2, immersing the electrode unit precursor in an electrolyte solution to form an electrolyte layer on the surface of the electrode plate; S3, providing a second electrode tab connected to the first electrode tab to form a composite electrode tab; S4, connecting a tab connecting sheet to the composite electrode tab to obtain an electrode unit; S5, forming the lithium-ion battery.

[0005] According to some embodiments of the present application, the electrode layer includes an organic ligand, the electrolyte solution includes a lithium salt, or the electrode layer includes a lithium salt, the electrolyte solution includes an organic ligand; the organic ligand and the lithium salt can undergo a eutectic reaction to form a eutectic electrolyte layer in situ on the surface of the electrode layer.

[0006] According to some embodiments of the present application, forming the composite electrode tab may include: cleaning the first electrode tab, and laminating the second electrode tab on the first electrode tab by seam welding to form the composite electrode tab.

[0007] According to some embodiments of the present application, a welding edge between the second electrode tab and the first electrode tab may be aligned with a welding edge between the first electrode tab and the current collector layer.

[0008] According to some embodiments of the present application, the second electrode tab may have the same size as the first electrode tab.

[0009] According to some embodiments of the present application, the acquisition electrode unit may include: connecting the tab connecting piece to the composite electrode tab by ultrasonic welding; wherein the tab connecting piece is connected to both the first electrode tab and the second electrode tab.

[0010] According to some embodiments of the present application, the preparation method may further include: forming a sealing protective layer in the welding area of ​​the ultrasonic welding.

[0011] On the other hand, the present application provides a lithium ion battery, which can be prepared by the preparation method described above.

[0012] In another aspect, the present application provides a lithium-ion battery module, which may include a plurality of lithium-ion batteries as described above that are arranged in sequence and electrically connected.

[0013] The lithium-ion battery manufacturing method disclosed in this application involves soaking the electrodes in an electrolyte solution after connecting the tabs to each other, forming a eutectic electrolyte on the surface of the electrode sheet to optimize interfacial contact and improve ion transmission efficiency. After the electrolyte solution is soaked, a dry tab is welded on top of the wet tab to form a "dry-wet" composite structure, and the dry tab is then ultrasonically welded to the tab connecting tab. This prevents the risk of battery short circuits caused by tab detachment and the problem of weak welding strength of the tab connecting tab after subsequent ultrasonic welding of the tab, thereby improving the manufacturing qualification rate and long-term reliability of lithium-ion batteries.

[0014] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The disclosure of this application will be more easily understood with reference to the accompanying drawings. Those skilled in the art will readily appreciate that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this application. Furthermore, similar numbers in the figures represent similar components, where:

[0016] Figure 1 is an exemplary flow chart of a method for preparing a lithium-ion battery according to some embodiments of the present application;

[0017] Figure 2 is a schematic diagram of an exemplary structure of an electrode unit according to some embodiments of the present application;

[0018] Figure 3 is a schematic diagram of an exemplary structure of a composite electrode tab according to some embodiments of the present application;

[0019] Figure 4 Schematic diagram of another exemplary structure of an electrode unit according to some embodiments of the present application. DETAILED DESCRIPTION

[0020] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0021] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. Words such as "include" or "comprise" used in this application mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. The terms "and / or" or "and / or" used in this application include any and all combinations of one or more related listed items.

[0022] Currently, one lithium-ion battery manufacturing method involves soaking a tab-welded electrode sheet with an electrolyte solution to optimize interfacial contact and enhance ionic conductivity. However, after electrolyte soaking, the weld area between the tab and the electrode sheet may be weakened due to electrolyte penetration, causing the tab to fall off during subsequent assembly or use, and also affecting subsequent welding of the tab to the connecting sheet.

[0023] Based on this, the present application provides a method for preparing a lithium-ion battery, which avoids the risk of battery short circuit caused by tab detachment through a laminated composite tab structure, thereby improving the manufacturing qualification rate and long-term reliability of the battery.

[0024] Some preferred embodiments of the present application are described below. It should be noted that the following description is for illustrative purposes and is not intended to limit the scope of protection of the present application. The steps involved in the present application can be performed precisely in order, or various steps can be processed in reverse order or simultaneously. At the same time, other operations can be added to these processes, or one or more operations can be removed from these processes.

[0025] refer to Figure 1 1 is an exemplary flow chart of a method for preparing a lithium-ion battery. The method 100 for preparing a lithium-ion battery may include the following steps.

[0026] Step S1: providing an electrode plate, and connecting a first electrode tab to the electrode plate to obtain an electrode unit precursor.

[0027] In some embodiments, the electrode plate includes an electrode layer and a current collector layer.

[0028] In some embodiments, the electrode plates include positive electrode plates and / or negative electrode plates.

[0029] As a feasible implementation, the positive electrode sheet may include a positive electrode layer and a positive electrode current collector layer, and the negative electrode sheet may include a negative electrode layer and a negative electrode current collector layer.

[0030] In some embodiments, the first electrode tab may include but is not limited to aluminum foil, aluminum nickel-plated, titanium foil, stainless steel, etc. as the positive electrode tab, and include but is not limited to copper nickel-plated, stainless steel, titanium foil, graphene-copper composite foil, etc. as the negative electrode tab. Connecting the first electrode tab to the electrode plate may be to connect to the current collector of the electrode plate. As an example, the first electrode tab can be fixedly connected to the edge of the current collector layer of the electrode by roll welding. The connection resistance between the first electrode tab and the current collector layer is less than 1mΩ, which can ensure good conductivity between the first electrode tab and the current collector. After welding is completed, the electrode plate connected with the first electrode tab can be used as the electrode unit precursor.

[0031] Step S2: Immersing the electrode unit precursor in an electrolyte solution to form an electrolyte layer on the surface of the electrode plate.

[0032] In some embodiments, the electrode plate includes an organic ligand, the electrolyte solution includes a lithium salt, or the electrode layer includes a lithium salt, and the electrolyte solution includes an organic ligand; the organic ligand and the lithium salt can undergo a eutectic reaction to form a eutectic electrolyte layer in situ on the surface of the electrode layer.

[0033] As a feasible implementation, the positive electrode layer may include a positive electrode active material, a solid electrolyte, a first conductive agent, a first binder, and a first organic ligand. Exemplary positive electrode active materials may include, but are not limited to, layered compounds such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel cobalt manganese oxide (LiNi x Co x Mn 1-2x O2, NCM), lithium nickel cobalt aluminum oxide (LiNi0.8Co0. 15 Al0. 05 O2, NCA), etc., or compounds substituted by one or more transition metals; lithium manganese oxides such as Li 1+x Mn 2-x O4 (x is 0~0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxides such as Li2CuO2; vanadium compounds such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; 1-x M x Lithium nickel oxide represented by O2 (wherein M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, including at least one of the above elements, wherein x is 0.01~0.3); 2-x M x Lithium manganese composite oxide represented by the formula Li2Mn3MO8 (wherein M is Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x O4 is a spinel lithium manganese composite oxide; the Li part in the LiMn2O4 formula is replaced by alkaline earth metal ions; LiNi x Co y Mn (1-x-y) O2 (where x = 0.8, y = 0.1); disulfide; Fe2(MoO4)3; lithium cobalt oxide; lithium iron phosphate; elemental sulfur (S8); Li2Sn (n = 1), organic sulfur compounds or carbon-sulfur polymers (C2S x ) n (x is 2.5 to 50, n is 2); may include sulfur compounds, etc.

[0034] Solid-state electrolytes may include, but are not limited to, sulfide solid-state electrolyte materials, halide solid-state electrolyte materials, oxide solid-state electrolytes, nitride solid-state electrolytes, hydride solid-state electrolytes, borate solid-state electrolytes, polymer-based solid-state electrolytes, inorganic compound-polymer mixed solid-state electrolytes, and the like.

[0035] Some suitable but non-limiting sulfide solid electrolytes may include but are not limited to Li2S-P2S5, Li2S-P2S5–MS x (M=Si, Ge, Sn, 0≤x≤2), Li 9.6 P3S 12 、Li7P3S 11 、Li7P2S8I、Li 10 SnP2S 12 、Li 10 SiP2S 12 、Li9P3S9O3、LGPS(Li 10 GeP2S 12 )、Thio-LISICON(Li 3.25 Ge 0.25 P 0.75 S4), Li6PS5X (X=Cl, Br, I), Li3PS4-X (X=Cl, Br, I), Li4SnS4-X (X=Cl, Br), Li 3.25 Ge 0.25 P 0.75 S4, Li 3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 、Li 10.35 Ge 1.35 P 1.65 S 12 、Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P2S 12 、Li 10 (Ge 0.5 Sn 0.5 )P2S 12 、Li 10 (Si 0.5 Sn 0.5 )P2S 12 , Li6(PS5)0.7(GeS4)0.3Cl, Li7.5P2.5Sn0.5S10 .5Cl1.5, Li6PS5Cl0.5Br0.5, Li6PS5I 0.2 Cl 0.8 、Li5SnS2Cl3、Li 10 P3S 12 Cl2, Li7P2S8.5Cl0.5, etc. or any combination thereof.

[0036] Some suitable but non-limiting halide solid electrolytes may include, but are not limited to, LaF3, LiCl, LiI, etc. or a solid electrolyte with the chemical formula Li a MX b represents a lithium halide solid electrolyte, wherein M represents a metal element or a metalloid element, including one or more of B, Si, Ge, As, Sb, Te, Al, Zn, Mg, Ca, Ba, Mn, Cd, Co, Yb, Y, Cr, In, Ga, Sr, Hf, Ti, Ta, Sn, Nb, Er, Sc, etc., and X represents a halogen element such as F, Cl, Br, I, etc. For example, Li2CdCl4, Li2MgCl4, Li2CdI4, Li2ZnI4, Li2ZrCl6, Li3YCl6, Li3InCl6, etc.

[0037] Some suitable but non-limiting oxide solid electrolytes may include, but are not limited to, NASICON type solid electrolytes such as LiTi2(PO4)3, LiGeTi(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3, Li 1+x Al x Ge 2-x (PO4)3(LAGP, where 0≤x≤2), Li 1+x Al x Ti 2-x (PO4)3(LATP, where 0≤x≤2), Li 1+x Y x Zr 2-x (PO4)3(LYZP, where 0≤x≤2), Li 1.3 Al 0.3 Ti 1.7 (PO4)3, etc., perovskite-type solid electrolytes such as Li 3x La( 2 / 3-x )TiO3(LLTO, where 0 <x<0.25)、LiSr 1.65 Zr 1.3 Ta 1.7 O9, Li 2x-y Sr 1-x Ta y Zr 1-yO3 (where x = 0.75y and 0.60 < y < 0.75), etc., LISICON-type solid electrolytes such as Li 14 ZnGe4O 16 、Li4SiO4, LiGeO4, etc., garnet-type solid electrolytes such as Li7La3Zr2O 12 、Li 6.5 La3Zr 1.75 Te 0.25 O 12 、Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr2O 12 、Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 、Li 6.25 Al 0.25 La3Zr2O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O[[ID=S7]] 12 etc., etc. or any combination thereof.

[0038] Some suitable but non-limiting nitride solid electrolytes can include, but are not limited to, Li3N, Li7PN4, LiSi2N3, Li9N2Cl3, etc.

[0039] Some suitable but non-limiting hydride solid electrolytes can include, but are not limited to: LiBH4, LiBH4 - Li X (X = Cl, Br or I), LiNH2, Li2NH, LiBH4 - LiNH2, Li3AlH6, etc.

[0040] Some suitable but non-limiting borate solid electrolytes can include, but are not limited to, Li2B4O7, Li2O - B2O3 - P2O5, Li2B 10 H 10 - Li2B 12 H 12 、Li7N2I - 0.5LiOH, etc.

[0041] Some suitable but non-limiting polymer solid electrolytes may include, but are not limited to, polyethylene oxide (PEO)-based electrolytes, polyphenylene ether (PPO)-based electrolytes, polyvinylidene fluoride (PVDF)-based electrolytes, polymethyl methacrylate (PMMA)-based electrolytes, polyacrylonitrile (PAN)-based electrolytes, and the like.

[0042] Some suitable but non-limiting inorganic compound-polymer mixed solid electrolytes may include, but are not limited to, LLZO-PEO composite electrolytes, LLZO-PVDF composite electrolytes, POSS-based organic-inorganic hybrid electrolytes, and the like.

[0043] Derivatives of the above electrolytes obtained by substitution, doping, modification, and compounding can also be used as solid electrolyte materials in this application. For example, Li2ZrCl6 substituted or partially substituted with bromine (Br), such as Li2ZrCl 6-x Br x , rare earth metals such as lanthanum or yttrium doped Li6PS5Br, LLZO deposited on the surface of indium (In), etc. It should be noted that the above examples are only for illustrative purposes and are not intended to limit the present application.

[0044] In some implementations, the solid electrolyte may be an oxide solid electrolyte material, for example, lithium aluminum titanium phosphate (Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LATP), garnet-type solid electrolytes such as lithium lanthanum zirconium oxide (Li7La3Zr2O 12 , LLZO), perovskite solid electrolytes such as lithium lanthanum titanium oxide (Li 0.33 La 0.56 One of TiO3, LLTO).

[0045] The above inorganic electrolytes can be presented in the form of powders, for example, by using methods such as mechanical ball milling (for example, weighing the reactants according to the stoichiometric ratio and then high-energy ball milling in an inert atmosphere (such as Ar / He), and annealing after completion), high-temperature melt quenching method (for example, heating the reactant mixture to melt in an inert atmosphere, and then rapidly cooling the solution and annealing), solution method (for example, dissolving the reaction precursor in an organic solvent and slowly evaporating the solvent in an inert atmosphere, followed by sintering to remove the residual solvent and crystallize), chemical vapor deposition (for example, using vaporized raw materials on a heated substrate for thin film deposition and low-temperature annealing), solid-phase reaction method (for example, the powdered reaction raw materials are uniformly mixed and pressed into a sheet, which is then heated and kept warm in an inert atmosphere, and then rapidly cooled after completion). The present application does not impose specific restrictions.

[0046] Exemplary first conductive agents may include, but are not limited to, graphites such as natural graphite and artificial graphite, carbon blacks such as conductive carbon black (Super P), acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black, carbon fibers such as VGCF, conductive fibers such as metal fibers, metal powders such as carbon fluoride, aluminum powder, and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, conductive polymers such as polyaniline, polypyrrole, polythiophene, and polyphenylene derivatives, and mixtures of one or two or more thereof.

[0047] Exemplary first binder can include but is not limited to can use any known binder including but not limited to polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinyl pyrrolidone, polyether, polyether sulfone, polyhexafluoropropylene, styrene-butadiene rubber, carboxymethyl cellulose etc. or its any combination can be used for this application. Copolymer can also be used as binder, exemplary can be selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, hexadiene etc. two or more material copolymer. Or, the mixture of two or more materials in the above example can also be used as binder.

[0048] The first organic ligand may be an organic compound for providing an organic anion or an organic cation. For example, the first organic ligand may include, but is not limited to, urea, sulfone compounds, amide compounds, nitrile compounds, alcohol compounds, imidazole compounds, crown ether compounds, or derivatives thereof. In some implementations, the first organic ligand may include N-methylacetamide (MAC), acetamide (Ace), succinonitrile (SN), urea (Urea), dimethyl sulfoxide (DMSO), methanol, ethylene glycol (EG), and the like.

[0049] The mass ratio between the positive electrode active material, solid electrolyte, first conductive agent, first binder and first organic ligand constituting the positive electrode layer is (70~90):(8~20):(1~10):(1~5):(1~5). Any mass ratio within this numerical range can be applied to this application without any limitation.

[0050] In some embodiments, the positive electrode current collector may include but is not limited to one or more of aluminum foil, carbon-coated aluminum foil, stainless steel foil, titanium foil, aluminum-copper laminated foil, nickel-clad aluminum, niobium foil, molybdenum foil, etc., or any combination thereof.

[0051] Regarding the preparation of positive electrode sheets, one feasible method is to weigh the aforementioned positive electrode active material, solid electrolyte, first conductive agent, first binder, and first organic ligand according to predetermined mass and place them in a mixing machine for mixing. The mixing machine can be any suitable mixer, such as one capable of high-speed dispersion or airflow crushing. Mixing parameters such as speed and temperature can be adjusted according to actual conditions. Subsequently, the homogenized mixture can be mixed with a solvent such as deionized water or N-methyl-2-pyrrolidone (NMR) to produce a positive electrode slurry. This positive electrode slurry is evenly coated onto a positive electrode current collector such as aluminum foil, dried to remove the solvent, and then rolled and slit to produce positive electrode sheets. Another feasible method is to utilize high-speed shear during mixing to fibrillate the first binder (such as PTFE) to produce a uniform, fiberized mixture. This uniform mixture is then subjected to compression, such as molding, calendaring, or rolling, to produce a layered or film-like positive electrode layer / membrane. This positive electrode layer / membrane is then rolled and laminated with the positive electrode current collector to produce the positive electrode sheet.

[0052] In some embodiments, the negative electrode sheet may include a negative electrode layer and a negative electrode current collector. The negative electrode layer may include a negative electrode active material, a second conductive agent, a second binder, and a second organic ligand. The negative electrode active material may include carbonaceous materials such as graphite, hard carbon, soft carbon, silicon, silicon-carbon mixture, lithium titanate (Li4Ti5O 12 ), transition metals such as Sn, metal oxides or metal sulfides such as TiO2, FeS, SnO2, or other negative active materials that accept lithium such as lithium-indium (Li-In).

[0053] The second conductive agent, the second binder and the second organic ligand may be the same as or similar to the first conductive agent, the first binder and the first organic ligand, respectively. For details, please refer to the above-mentioned relevant content and will not be repeated here.

[0054] The mass ratio of the negative electrode active material, the second conductive agent, the second binder and the second organic ligand constituting the negative electrode layer is (80~95):(1~10):(1~5):(1~5). Any mass ratio within this numerical range can be applied to the present application without any limitation.

[0055] The negative electrode current collector may include, but is not limited to, one of copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, and a polymer substrate coated with a conductive metal, or any combination thereof.

[0056] Similar to the preparation of the positive electrode sheet, the negative electrode sheet can also be prepared by slurry coating or dry rolling, etc., which is not restrictive.

[0057] In some embodiments, the electrolyte solution may include a lithium salt, an organic solvent, and an additive. For example, the lithium salt may include, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI), lithium bis(fluorosulfonyl imide) (LiFSI), lithium difluorooxalatoborate (LiDFOB), lithium perchlorate (LiClO4), lithium nitrate (LiNO3), lithium bis(oxalatoborate) (LiBOB), lithium hexafluoroarsenate (LiAsF6), lithium difluorophosphate (LiPO2F2), lithium tetrafluoroborate (LiBF4), lithium chloride (LiCl), trifluoromethanesulfonate ... lithium trifluoromethanesulfonate (LiTFSI), lithium bis(fluorosulfonyl imide) (LiFSI), lithium difluorooxalatoborate (LiDFOB), lithium perchlorate (LiClO4), lithium nitrate (LiNO3), lithium bis(fluorosulfonyl borate) (LiBOB), lithium hexafluoroarsenate (LiAsF6), lithium difluorophosphate (LiPO2F2), lithium tetrafluoroborate (LiBF any combination of one or more of lithium bis(fluoromalonate)borate, lithium tetracyanoborate, dicyanotriazole lithium salt, dicyano-trifluoromethyl-imidazole lithium salt, dicyano-pentafluoroethyl)-imidazole lithium salt, and the like.

[0058] Exemplary organic solvents may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethyl acetate (EA), ethyl propionate (EP), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), butane disulfone (BDS), cyclopentane sulfone (TMS), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI), and any combination thereof.

[0059] Exemplary additives may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethyl acetate (EA), ethyl propionate (EP), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), butane disulfone (BDS), cyclopentane sulfone (TMS), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (EMIM-TFSI), and any combination thereof.

[0060] The mass ratio of the lithium salt, organic solvent, and additive can be (30-45): (50-65): (1-20). Any mass ratio within this numerical range can be applied to the present application without any limitation.

[0061] In some embodiments, when the electrode unit precursor is immersed in the electrolyte solution, the lithium salt can react with the organic ligand (e.g., the first organic ligand, the second organic ligand) to form a eutectic electrolyte layer in situ on the surface of the electrode layer. For example, the organic ligand SN and the lithium salt LiTFSI / LiFSI react via the cyano group (-CN) and the anion (TFSI - / FSI - ) form a eutectic network, thereby forming an in-situ eutectic electrolyte layer on the surface of the electrode layer. For example, DMIm + As a cation and anion of LiTFSI (TFSI - ) form a eutectic structure through electrostatic interaction. For example, the sulfur atom of DpyDS interacts with Li + Coordinated with TFSI - The formation of multi-anion coordination to obtain a coordination eutectic system, the amino group (-NH2) of urea / MU and TFSI - The fluorine atoms form strong hydrogen bonds to obtain a stable eutectic network.

[0062] During the charge / discharge process, eutectic electrolytes can provide ion transport between two interfaces. They have a wide electrochemical window and excellent chemical stability, are non-toxic, and are inexpensive. At the same time, due to the presence of complex anions and cations, eutectic electrolytes also have properties not possessed by other electrolytes, including non-flammability, ease of synthesis, structural flexibility, and multi-electron reactivity. By infiltrating the electrode unit precursor to form a eutectic electrolyte on the surface of the electrode layer, the electrical performance of lithium-ion batteries can be improved.

[0063] In some embodiments, the immersion temperature can be 25°C-45°C. For example, the immersion temperature can be 25°C, 30°C, 35°C, 40°C, 45°C, etc., or any value within the above immersion temperature range. The immersion time can be 6 hours-48 hours. For example, the immersion time can be 6 hours, 9 hours, 12 hours, 15 hours, 18 hours, 21 hours, 24 hours, 30 hours, 36 hours, 42 hours, 48 ​​hours, etc., or any value within the above immersion time range.

[0064] The infiltration of the electrode unit precursor inevitably also infiltrates the first electrode tab. The reason for the coordinated infiltration of the electrode tab is that the electrode tab, as a component connecting the electrode sheet to the external circuit, requires good contact with the electrolyte solution to maintain a stable electrochemical environment during battery charging and discharging. This also facilitates the uniform diffusion and distribution of the electrolyte solution, resulting in more uniform electrochemical reactions within the battery, reducing problems such as local overheating or overcharge and over-discharge, and improving battery safety and consistency. However, the infiltration of the electrode tab (e.g., the aforementioned first electrode tab) inevitably causes the interface between the tab and the current collector (e.g., including the positive electrode current collector and / or the negative electrode current collector) (e.g., the aforementioned roll weld interface) to be penetrated by the electrolyte solution. This can weaken the connection strength between the electrode tab and the electrode sheet (e.g., the aforementioned roll weld area) due to the penetration of the electrolyte solution, leading to the tab's detachment during subsequent assembly or use. It can also affect the subsequent connection between the tab and the electrode connector.

[0065] Based on this, the preparation method of the lithium-ion battery provided in the present application includes step S3, providing a second electrode tab connected to the first electrode tab to form a composite electrode tab, so as to avoid the risk of battery short circuit caused by the electrode tab falling off and the problem of weak connection strength of the subsequent connection electrode connecting piece, thereby improving the manufacturing qualification rate and long-term use reliability of the lithium-ion battery.

[0066] In some embodiments, the length of the first electrode tab and the second electrode tab ranges from 10 to 100 mm, and the width ranges from 3 to 60 mm. Any value within this numerical range can be applied to the present application without any limitation.

[0067] In some embodiments, the second electrode tab can be the same size as the first electrode tab and made of the same material. For example, assuming the first electrode tab, which serves as the positive electrode tab, is a 40mm×15mm aluminum foil, the second electrode tab, which is laminated and connected to the first electrode tab, is also a 40mm×15mm aluminum foil. For another example, assuming the first electrode tab, which serves as the negative electrode tab, is a 40mm×15mm copper foil, the second electrode tab, which is laminated and connected to the first electrode tab, is also a 40mm×15mm copper foil.

[0068] In some embodiments, laminating the second electrode tab and the first electrode tab to form a composite electrode tab may include cleaning the first electrode tab after infiltration and then performing roll welding. The cleaning may be achieved by purging with an inert gas. For example, nitrogen, helium, argon, etc. may be used to purge the first electrode tab for 10-30 seconds to remove free electrolyte solution on the surface. The cleaning may also be performed by using an absorbent material to absorb the electrolyte solution on the surface of the first electrode tab to dry it. Alternatively, other suitable cleaning methods may be applied to the present application. The second electrode tab may also be pretreated to enhance welding activity. For example, the surface of the second electrode tab may be plasma treated. If the second electrode tab is copper foil, a 90W Ar / O2 plasma treatment may be used for 12 seconds. If the second electrode tab is aluminum foil, a 70W pure Ar plasma treatment may be used for 6 seconds.

[0069] The stacked connection between the first and second electrode tabs can be achieved by seam welding the second electrode tab stack onto the first electrode tab. The welded edges of the second electrode tab and the first electrode tab are aligned with the welded edges of the first electrode tab and the current collector layer. That is, after one end of the first electrode tab is welded to the current collector, the second electrode tab is still welded to the same end of the first electrode tab. In some implementations, the seam welding can be performed using a seam welder. The seam welder's amplitude can be 16-20% of the thickness of the electrode tab (including the first or second electrode tab), for example, 16%, 17%, 18%, 19%, 20%, etc. Alternatively, the seam welder's amplitude can be 18% of the thickness of the electrode tab. The welding pressure can be 50-200 MPa, for example, 50 MPa, 100 MPa, 150 MPa, 200 MPa, etc. Alternatively, the welding pressure can be 100 MPa. The roll welding temperature can be set to 25-35°C, for example, 25°C, 27°C, 29°C, 31°C, 33°C, 35°C, etc. The roller speed can be set to 5-10 m / min, for example, 5 m / min, 6 m / min, 7 m / min, 8 m / min, 9 m / min, 10 m / min, etc., or the roller speed can be set to 8 m / min. The weld depth can be 0.1-0.2 mm, for example, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, etc., or the weld depth can be 0.15 mm. After the roll welding is completed, a composite electrode tab is obtained, having a dry second electrode tab superimposed on a wet first electrode tab. Roll welding is used rather than ultrasonic welding to weld the second and first electrode tabs together, joining them to the current collector layer. This is primarily because roll welding is more adaptable to residual electrolyte solutions and avoids side reactions caused by high-frequency ultrasonic vibrations (such as electrolyte decomposition or active material shedding). Roll welding achieves a stable connection through a combination of heat and pressure, is highly tolerant of material variations, and offers uniform weld strength and a higher yield rate. Furthermore, the linear pressure of roll welding maximizes the structural integrity of the electrode and minimizes porosity variations, making it more suitable for industrial mass production.

[0070] Step S4: Connecting the tab connecting piece to the composite electrode tab to obtain an electrode unit.

[0071] In some embodiments, the other end of the composite electrode tab (e.g., opposite the end welded to the current collector) can be used to connect to the tab tab tab, including but not limited to a nickel sheet, nickel-plated copper, aluminum sheet, stainless steel, titanium sheet, or a composite metal (e.g., aluminum-copper), or other materials, which may be adjusted based on actual conditions and are not specifically limited in this application. This connection can be achieved by ultrasonic welding. As an example but not limiting illustration, when ultrasonically welding the composite electrode tab on the positive electrode side to the tab tab tab, the amplitude can be 50 μm, the pressure can be 45 PSI, the energy can be 450 J, the time can be 0.93 s, and the power can be 2088 W. When ultrasonically welding the composite electrode tab on the negative electrode side to the tab tab tab, the amplitude can be 50 μm, the pressure can be 50 PSI, the energy can be 481 J, the time can be 0.5 s, and the power can be 2050 W. Ultrasonic welding is used on the other end because it utilizes high-frequency vibrations to achieve rapid, localized connections and can be completed in milliseconds without the need for additional heating. Its characteristics of concentrated energy and small heat-affected zone can ensure low-impedance contact between the connecting piece and the tab interface, while avoiding thermal damage to the tab area that has been soaked in the electrolyte solution.

[0072] In some embodiments, after the ultrasonic welding is completed, a sealing protective layer can also be formed in the corresponding welding area. Exemplarily, the welding area of ​​the ultrasonic welding can be coated with a resin having properties such as heat resistance, oxygen resistance, moisture resistance, and chemical resistance, and the sealing protective layer is formed after curing. Methods such as thermal curing, light curing, and free radical curing can be used here without limitation. After completion, the electrode unit will be obtained. In some implementations, the formation of the above sealing protective layer can be achieved using epoxy resin modified silicone, and can also be achieved using one or more of polyurethane (PU) based protective glue, acrylate adhesive, silicone resin, fluororubber (FKM) coating, and polyparaxylene (Parylene) vapor deposition coating.

[0073] refer to Figures 2 to 4 , provides an exemplary structural diagram of an electrode unit, and an exemplary structural diagram of a composite electrode tab. Figures 2 to 4 As shown, Figure 2 It shows the top view of the electrode tab and the electrode sheet after welding. Figure 3 It shows an enlarged view of the positive electrode tab and the positive electrode sheet after welding. Figure 4 Figure 2 shows a side view of the electrode tab and the electrode sheet after welding. Figures 2 to 4As shown, the positive electrode sheet P is slightly smaller than the negative electrode sheet N and is located at the center of the negative electrode sheet N. The positive electrode sheet P may include a positive current collector layer, which may be an aluminum foil, and the positive electrode tab PT that is first welded to the positive current collector layer may also be an aluminum foil. The welding may be performed by a roll welding process, and a roll welding area SW is formed after completion. The negative electrode sheet N may include a negative current collector layer, which may be a copper foil, and the negative electrode tab NT that is first welded to the negative current collector layer may also be a copper foil. The welding may be performed by a roll welding process, and a roll welding area SW is formed after completion. After the electrode sheet and the tab are soaked in the electrolyte solution, the tab welded for the first time (the first electrode tab, which may also be referred to as the wet tab) is prone to falling off, affecting the subsequent secondary welding of the electrode sheet connector. Therefore, the second electrode tab (which may also be referred to as the dry tab) is welded on the surface of the wet tab by a roll welding process. See Figure 4 For the positive electrode P, the dry tab PT2 is welded on the wet tab PT1 by the roll welding process. In this welding, the dry tab PT2 and the wet tab PT1 are made of the same material, aluminum foil. They are of the same size. The welding edges are aligned, and the Figure 4 The figure shows the roll welding area SW. For the negative electrode N, the dry tab NT2 is welded on the wet tab NT1 by the roll welding process. In this welding, the dry tab NT2 and the wet tab NT1 are made of the same material, copper foil. They are of the same size. The welding edges are aligned, and the Figure 4 It is presented as the roll welding area SW. In this way, a "dry-wet" superimposed composite electrode tab can be obtained, which can not only ensure that the battery avoids the risk of short circuit, but also ensure that the electrolyte solution is evenly distributed. Subsequently, the composite electrode tab can be welded to the tab connector. For the composite positive electrode tab, it can be connected to the positive electrode tab connector PC (for example, an aluminum sheet) by ultrasonic welding, and an ultrasonic welding area UW is formed between the two. For the composite negative electrode tab, it can be connected to the negative electrode tab connector NC (for example, a nickel sheet) by ultrasonic welding, and an ultrasonic welding area UW is formed between the two. After the ultrasonic welding is completed, the final electrode unit will be obtained.

[0074] Step S5: forming the lithium-ion battery.

[0075] In some embodiments, the lithium-ion battery is formed by sequentially stacking a positive electrode unit, a separator, and a negative electrode unit to obtain the lithium-ion battery.

[0076] In some embodiments, the separator comprises a diaphragm or a solid electrolyte membrane.

[0077] In some embodiments, the membrane may include polymer-based membranes such as polyolefin membranes, polyimide membranes, polyvinylidene fluoride membranes, polyacrylonitrile membranes, polyethersulfone membranes, etc., cellulose-based membranes such as bacterial cellulose membranes, regenerated cellulose membranes, etc., ceramic membranes such as alumina membranes, silica, boehmite, calcium titanate, etc., glass fiber membranes such as borosilicate glass fiber membranes, etc., polymer-inorganic composite membranes such as PE / PVDF-Al2O3 membranes, cellulose / ceramic coating membranes, etc., polymer-polymer composite membranes such as PVDF-HFP membranes, etc., carbon-based material membranes such as graphene coating membranes, etc.

[0078] In some embodiments, the solid electrolyte membrane material includes but is not limited to oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, etc., which are the same types of solid electrolyte materials mentioned in the positive electrode plate mentioned above and will not be repeated here.

[0079] In some embodiments, an electrolyte may be added to the prepared lithium-ion battery. A dry cell is obtained by sequentially stacking the positive electrode unit, separator, and negative electrode unit. The electrolyte is then injected into the dry cell. After the injection is complete, the cell is allowed to stand and volume is divided to obtain the lithium-ion battery. The standing time may be 12 to 36 hours. For example, the standing time may be 12 hours, 15 hours, 18 hours, 21 hours, 24 hours, 30 hours, 36 hours, or any other value within the above time ranges.

[0080] In some embodiments, the prepared lithium-ion battery can be prepared without adding an electrolyte. The positive electrode unit, separator, and negative electrode unit are stacked in sequence and encapsulated in an aluminum-plastic film. A vacuum is applied to the aluminum-plastic film, which is then sealed. The battery is then isostatically pressed at 450-500 MPa to obtain the lithium-ion battery. The isostatic pressing pressure can be 450 MPa, 460 MPa, 470 MPa, 480 MPa, 490 MPa, 500 MPa, or any other value within the above time ranges.

[0081] The lithium-ion battery manufacturing method disclosed in this application involves soaking the electrodes in an electrolyte solution after connecting the tabs to each other, forming a eutectic electrolyte on the surface of the electrode sheet to optimize interfacial contact and improve ion transmission efficiency. After the electrolyte solution is soaked, a dry tab is welded on top of the wet tab to form a "dry-wet" composite structure, and the dry tab is then ultrasonically welded to the tab connecting tab. This prevents the risk of battery short circuits caused by tab detachment and the problem of weak welding strength of the tab connecting tab after subsequent ultrasonic welding of the tab, thereby improving the manufacturing qualification rate and long-term reliability of lithium-ion batteries.

[0082] The present application also discloses a lithium ion battery, which can be prepared based on the preparation method described above.

[0083] The present application also discloses a lithium-ion battery module, which is formed by folding, stacking, or combining the above-mentioned multiple lithium-ion batteries and electrically connecting them to each other.

[0084] The present application is further described in detail below with reference to the following examples. It should be noted that the following examples are only used to illustrate the present application and are not intended to limit the scope of protection claimed in the present application.

[0085] Example 1 - Lithium-ion battery preparation

[0086] 1) Preparation of positive electrode layer: positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, solid electrolyte LATP, first conductive agent Super-P, first binder PVDF and first organic ligand SN are weighed and mixed in a mass ratio of 84:10:3:2:1, mixed with solvent NMR to obtain a positive electrode slurry, evenly coated on the current collector aluminum foil, and rolled and cut to obtain a positive electrode sheet;

[0087] 2) Preparation of negative electrode layer: The negative electrode active material graphite, the second conductive agent Super-P, the second binder CMC, SBR, and the second organic ligand SN were weighed and mixed uniformly in a mass ratio of 94:3:1:1:1, mixed with deionized water to obtain a negative electrode slurry, and evenly coated on the current collector copper foil, and rolled and slit to obtain a negative electrode sheet;

[0088] 3) Weld one end of the positive electrode tab and the negative electrode tab to the edge of the positive electrode sheet and the negative electrode sheet (welded to the positive electrode collector and the negative electrode collector respectively) by a roll welding machine, and soak them in the electrolyte solution at 35°C for 24 hours. The tab welding interface is penetrated by the electrolyte solution, that is, the tab is wet;

[0089] The positive electrode tab is aluminum foil, and the negative electrode tab is copper foil; the positive electrode current collector is aluminum foil, and the negative electrode current collector is copper foil;

[0090] The electrolyte solution consists of lithium salt LiTFSI, organic solvent BDS and additive FEC in a mass ratio of 38:57:5;

[0091] 4) Superimpose the dry tabs of the same material on the wet tabs, align the welding area (5mm from the edge of the pole piece), and roll weld the dry tabs to form a "dry-wet" composite structure;

[0092] The wet tab (after being soaked in electrolyte solution) is purged with an inert gas (such as Ar) for 20 seconds to remove the free electrolyte solution on the surface;

[0093] The dry tab (unwetted) surface is treated with plasma (the negative tab is copper foil: 90W Ar / O2 plasma treatment for 12 seconds; the positive tab aluminum foil: 70W pure Ar plasma treatment for 6 seconds) to improve welding activity;

[0094] The amplitude of the seam welder is 18% of the lug thickness;

[0095] The welding pressure is 100 MPa;

[0096] The roll welding temperature is set to 30°C;

[0097] The roller speed is set to 8m / min;

[0098] The weld depth is 0.15mm;

[0099] 5) The other end of the positive electrode tab (aluminum dry tab) is ultrasonically welded to the aluminum sheet, and the other end of the negative electrode tab (copper dry tab) is ultrasonically welded to the nickel sheet;

[0100] Positive electrode tab: ultrasonic welding (amplitude 50μm, pressure 45PSI, energy 450J, time 0.93s, power 2088W);

[0101] Negative electrode tab: ultrasonic welding (amplitude 50μm, pressure 50PSI, energy 481J, time 0.5s, power 2050W);

[0102] 6) Apply electrolyte solution resistant epoxy resin modified silicone glue on the welding area to form a sealing layer after curing;

[0103] 7) combining the composite positive electrode, separator PP, and negative electrode to obtain a lithium-ion battery to form a dry cell;

[0104] 8) Injecting electrolyte into the dry cell again; the electrolyte consists of 13% lithium salt LiPF6, 19% organic solvent EC, 20% DMC, 45% EMC and 3% additive FEC;

[0105] 9) After the injection is completed, let it stand and divide the volume to obtain a lithium-ion battery.

[0106] 30 lithium-ion batteries were prepared according to the method of Example 1, and the battery qualification rate was 96.7%.

[0107] Example 2 - Lithium-ion battery preparation

[0108] The difference from Example 1 is that a solid electrolyte membrane is used between the positive and negative electrodes, and the solid electrolyte material is Li7La3Zr2O 12The positive electrode unit, the solid electrolyte membrane, and the negative electrode unit are stacked in sequence and encapsulated in an aluminum-plastic film. A vacuum is applied to the aluminum-plastic film and then sealed. The battery is isostatically pressed at 460 MPa to obtain the lithium-ion battery.

[0109] 30 lithium-ion batteries were prepared according to the method of Example 2, and the qualified rate of the tested batteries was 96.7%.

[0110] Comparative Example 1 - Preparation of lithium-ion batteries

[0111] The difference from Example 1 is that dry tabs are not stacked and welded. After the positive and negative electrode sheets and tabs are soaked in electrolyte solution to form a eutectic electrolyte, the tab welding interface is penetrated by the electrolyte solution, and the other ends of the positive and negative tabs are directly ultrasonically welded to their respective metal connecting tabs. The welding between the tabs and the metal connecting tabs is not strong, and the tabs are prone to falling off, making the prepared battery prone to short circuits. Thirty lithium-ion batteries were prepared according to the method of Comparative Example 1, and the qualified rate of the tested batteries was 53.3%.

[0112] Test Example - Qualification Rate Test

[0113] 1. Pass the tensile test:

[0114] Take the welded pole piece-composite pole tab-connecting piece assembly and mark the welding area to avoid position deviation when applying tension.

[0115] Parallel tension (axial stretching): simulates the stress on the tab inside the battery;

[0116] Stretching speed: 10~50 mm / min;

[0117] Termination conditions: the welding point is completely separated or the tensile force drops by ≥50%;

[0118] Record the maximum tensile force (N): the peak force before the weld fails, that is, the weld interface breaks.

[0119] 2. Qualification criteria:

[0120] The peeling force between the aluminum tab and the aluminum sheet after welding is ≥25N, and the peeling force between the copper tab and the nickel sheet after welding is ≥25N.

[0121] While the basic concepts have been described herein, it will be apparent to those skilled in the art that the detailed disclosure herein is merely illustrative and does not constitute a limitation of the present application. Although not expressly provided herein, those skilled in the art may make various modifications, improvements, and amendments to the present application. Such modifications, improvements, and amendments are suggested herein and remain within the spirit and scope of the exemplary embodiments of the present application.

[0122] At the same time, this application uses specific terms to describe the embodiments of this application. For example, "one embodiment," "an embodiment," and / or "some embodiments" refer to a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "one embodiment," "an embodiment," or "an alternative embodiment" mentioned twice or multiple times in different locations in this application does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application may be appropriately combined.

[0123] Similarly, it should be noted that, in order to simplify the description of this application and thus facilitate understanding of one or more embodiments of the invention, the foregoing descriptions of the embodiments of this application sometimes combine multiple features into a single embodiment or its description. However, this disclosure method does not mean that the subject matter of this application requires more features than those recited in the claims. In fact, the features of an embodiment may be fewer than all the features of the individual embodiments disclosed above.

[0124] Finally, it should be understood that the embodiments described in this application are merely illustrative of the principles of the embodiments of this application. Other variations may also fall within the scope of this application. Therefore, by way of example and not limitation, alternative configurations of the embodiments of this application may be considered consistent with the teachings of this application. Accordingly, the embodiments of this application are not limited to the embodiments explicitly introduced and described in this application.

Claims

1. A method for preparing a lithium ion battery, characterized in that: The preparation method comprises: S1. Providing an electrode plate and connecting a first electrode tab to the electrode plate to obtain an electrode unit precursor; the electrode plate includes an electrode layer and a current collector layer; S2, soaking the electrode unit precursor in an electrolyte solution to form an electrolyte layer on the surface of the electrode plate; S3, providing a second electrode tab connected to the first electrode tab to form a composite electrode tab; S4, connecting the tab connecting piece to the composite electrode tab to obtain an electrode unit; S5. Forming the lithium-ion battery.

2. The preparation method according to claim 1, characterized in that The electrode layer includes an organic ligand, and the electrolyte solution includes a lithium salt, or the electrode layer includes a lithium salt, and the electrolyte solution includes an organic ligand; the organic ligand and the lithium salt undergo a eutectic reaction to form a eutectic electrolyte layer in situ on the surface of the electrode layer.

3. The preparation method according to claim 1, characterized in that The forming of the composite electrode tab comprises: The first electrode tab is cleaned, and the second electrode tab is laminated and connected to the first electrode tab by seam welding to form the composite electrode tab.

4. The preparation method according to claim 3, characterized in that A welding edge between the second electrode tab and the first electrode tab is aligned with a welding edge between the first electrode tab and the current collector layer.

5. The preparation method according to claim 3, characterized in that The second electrode tab has the same size as the first electrode tab.

6. The preparation method according to claim 1, characterized in that The acquisition electrode unit includes: The tab connecting piece is connected to the composite electrode tab by ultrasonic welding; wherein the tab connecting piece is connected to both the first electrode tab and the second electrode tab.

7. The preparation method according to claim 6, characterized in that The preparation method further comprises: A sealing protective layer is formed in the welding area of ​​the ultrasonic welding.

8. A lithium ion battery, characterized in that: The lithium-ion battery is prepared by the preparation method according to any one of claims 1 to 7.

9. A lithium-ion battery module, characterized in that: The lithium-ion battery module comprises a plurality of lithium-ion batteries prepared by the preparation method according to any one of claims 1 to 7 or the lithium-ion battery according to claim 8, which are arranged in sequence and electrically connected.

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