Lamination, battery pole piece, preparation method of battery pole piece and lithium ion battery

Abstract

The invention provides a lamination, a battery pole piece, a preparation method of the battery pole piece and a lithium ion battery. The lamination comprises a base material layer, a metal conductive layer, a welding auxiliary layer and a protective layer, the material of the base material layer is selected from an organic polymer material; the metal conductive layers are arranged on the surfaces of the two sides of the base material layer; the welding auxiliary layer is arranged on the surface, away from the substrate layer, of the metal conductive layer; the welding auxiliary layer is made of a metal material; the protective layer is arranged on the surface of the welding auxiliary layer away from the metal conductive layer; and the material of the protective layer comprises matrix resin A. When the lamination provided by the invention is used for preparing the battery pole piece, the welding treatment effect of the battery pole piece can be effectively improved, the internal resistance of the battery pole piece is reduced, and the electrochemical performance of the lithium ion battery can be improved when the lamination is applied to the lithium ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery manufacturing, and in particular to a laminate, a battery pole piece, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] In the production process of lithium batteries, metal foil is usually used as the current collector, with aluminum foil being used as the positive electrode current collector and copper foil being used as the negative electrode current collector. To improve the energy density and safety of the battery, a composite current collector composed of a polymer film and a metal coating has gradually attracted attention. However, due to the insulating properties of the polymer film used, the metal coatings on both sides of the polymer film are not conductive, and traditional welding methods are no longer suitable for welding this type of composite current collector. Using traditional welding methods, that is, directly welding the tabs of multi-layer composite current collectors, or welding the tabs and metal tabs of multiple layers of composite current collectors stacked alternately, both fail to weld successfully.

[0003] The commonly used method currently is to place two to five layers of pure metal foil between the multi-layer metal tabs, and then weld the multi-layer tabs to the lithium battery's positive aluminum tabs or negative copper tabs. There are currently two common welding methods: cladding welding and flat welding followed by bending. As is well known, cladding welding is a complex process with a low degree of automation. Equipment with a slightly higher degree of automation generally does not use this method to produce power-type soft-pack batteries. Flat welding followed by bending is usually performed on top of flat welding, with the soft-pack battery first flat-welded and then bent. The metal tabs are easily deformed or torn by the tensile force during bending, making it difficult to achieve in highly automated equipment.

[0004] With the increasing demand for soft-package batteries, finding a stack and battery electrode that is easy to weld is crucial to improving welding results, reducing the internal resistance of the battery electrode, and being suitable for highly automated equipment to achieve efficient and high-quality tab welding. Summary of the Invention

[0005] The main purpose of the present invention is to provide a laminate, a battery pole piece and a preparation method thereof and a lithium-ion battery, so as to solve the problems in the prior art of high difficulty in welding the composite current collector and the metal pole piece, resulting in poor welding effect and high internal resistance of the battery pole piece.

[0006] In order to achieve the above-mentioned objectives, the present invention provides a laminate on one hand, which includes: a substrate layer, the material of the substrate layer is selected from organic polymer materials; a metal conductive layer, the metal conductive layer is arranged on both side surfaces of the substrate layer; a welding auxiliary layer, the welding auxiliary layer is arranged on the surface of the metal conductive layer away from the substrate layer; the material of the welding auxiliary layer includes a metal material; a protective layer, the protective layer is arranged on the surface of the welding auxiliary layer away from the metal conductive layer; the material of the protective layer includes a base resin A.

[0007] Furthermore, the metal material is selected from one or more metal elements in the group consisting of elements in Group VIII, Group IVB, Group IB, Group VIB, Group IA, Group IIA, Group IIIA, Group IVA, and Group IIB; and / or, one or more alloys in the group consisting of copper alloys, aluminum alloys, nickel alloys, titanium alloys, and cobalt alloys.

[0008] Furthermore, the metal element is selected from one or more of the group consisting of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In and Zn.

[0009] Furthermore, the alloy is selected from one or more of the group consisting of copper alloys, aluminum alloys and nickel alloys.

[0010] Furthermore, the D50 of the metal material is 1 to 10 μm.

[0011] Furthermore, the matrix resin A is selected from thermoplastic resins, preferably one or more of the group consisting of polyvinylidene fluoride, polyvinyl alcohol and polytetrafluoroethylene, more preferably one or more of the group consisting of polyvinylidene fluoride with a weight average molecular weight of 390,000 to 690,000, polyvinyl alcohol with a weight average molecular weight of 60,000 to 150,000 and polytetrafluoroethylene with a weight average molecular weight of 100,000 to 1,000,000.

[0012] Furthermore, the substrate layer is selected from polyethylene terephthalate film or biaxially oriented polypropylene film.

[0013] Furthermore, the thickness of the substrate layer is 4.5 to 8 μm, preferably 4.5 to 6 μm.

[0014] Furthermore, the thickness of the metal conductive layer is 0.5-3 μm.

[0015] Furthermore, the thickness of the welding auxiliary layer is 2-20 μm.

[0016] Furthermore, the thickness of the protective layer is 0.5 to 5 μm.

[0017] In order to achieve the above-mentioned purpose, another aspect of the present invention further provides a battery electrode, which includes a plurality of laminates connected by welding, and the laminate is the above-mentioned laminate provided in this application. The battery electrode also includes a metal tab, which is welded and arranged at the outermost end of the plurality of laminates.

[0018] In order to achieve the above-mentioned purpose, another aspect of the present invention also provides a method for preparing the above-mentioned battery electrode provided in the present application, and the preparation method of the battery electrode comprises: step S1, preparing at least one metal conductive layer on the two side surfaces of the substrate layer to obtain a laminated structure; the material of the substrate layer is selected from organic polymer materials; step S2, coating a first slurry containing a metal material on the side surface of the metal conductive layer away from the substrate layer, and obtaining a laminated structure containing a welding auxiliary layer after a first drying; step S3, coating a second slurry containing a matrix resin A on the side surface of the welding auxiliary layer away from the metal conductive layer, and obtaining a laminated structure containing a protective layer after a second drying; step S4, stacking multiple laminated structures containing protective layers to obtain a laminate, and stacking a metal pole ear at the outermost end of the laminate, and obtaining a battery electrode after welding.

[0019] Furthermore, ultrasonic welding is used for welding, with a welding frequency of 2000-38000 Hz, an amplitude of 5-95%, a welding pressure of 0.2-0.8 MPa, and a welding time of 0.1-0.4 s.

[0020] Furthermore, laser welding is used for welding, with a welding power of 500 to 1000 W, a welding rate of 30 to 60 mm / s, and a welding time of 0.1 to 5 s.

[0021] Furthermore, the welding process is performed by riveting welding, the diameter of the riveting welding head used in the welding process is 1 to 15 mm, and the welding temperature is 800 to 1400°C.

[0022] Furthermore, the welding process is performed in an inert atmosphere.

[0023] Furthermore, in step S4, the number of laminations is n, where n is any integer between 5 and 70.

[0024] Furthermore, the metal material in the first slurry is selected from one or more metal elements in the group consisting of elements in Group VIII, Group IVB, Group IB, Group VIB, Group IA, Group IIA, Group IIIA, Group IVA, and Group IIB; and / or, one or more alloys in the group consisting of copper alloys, aluminum alloys, nickel alloys, titanium alloys, and cobalt alloys.

[0025] Furthermore, the metal element is selected from one or more of the group consisting of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In and Zn.

[0026] Furthermore, the alloy is selected from one or more of the group consisting of copper alloys, aluminum alloys and nickel alloys.

[0027] Furthermore, the D50 of the metal material is 1 to 10 μm.

[0028] Furthermore, the first slurry also includes a first dispersant and a matrix resin B; preferably, by weight, the first slurry includes 5 to 10 parts of metal material, 5 to 10 parts of the first dispersant and 0.5 to 1 part of the matrix resin B; preferably, the first dispersant is selected from a phenolic epoxy resin, more preferably a phenolic epoxy resin with an epoxy value of 0.44 to 0.8; preferably, the matrix resin B is selected from a thermoplastic resin, more preferably one or more of the group consisting of polyvinylidene fluoride, polyvinyl alcohol and polytetrafluoroethylene, further preferably one or more of the group consisting of polyvinylidene fluoride with a weight average molecular weight of 390,000 to 690,000, polyvinyl alcohol with a weight average molecular weight of 60,000 to 150,000 and polytetrafluoroethylene with a weight average molecular weight of 100,000 to 1,000,000.

[0029] Furthermore, the first slurry also includes one or more of the group consisting of a first auxiliary dispersant, a curing agent, a accelerator and a coupling agent; preferably, in the first slurry, the weight ratio of the metal material to the first auxiliary dispersant is 1:(0.1~0.5); further preferably, the first auxiliary dispersant is selected from a styrene-butadiene rubber aqueous solution and / or polyacrylamide, and further preferably a styrene-butadiene rubber aqueous solution with a solid content of 35~55% and / or a polyacrylamide with a weight average molecular weight of 500,000~20,000,000.

[0030] Furthermore, in the first slurry, the weight ratio of the metal material to the curing agent is 1:(0.01-0.1); further preferably, the curing agent is selected from diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide and / or 2,2-azobisisobutyronitrile.

[0031] Furthermore, in the first slurry, the weight ratio of the metal material to the accelerator is 1:(0.01-0.5); and further preferably, the accelerator is selected from polyetheramine and / or acrylate.

[0032] Furthermore, in the first slurry, the weight ratio of the metal material to the coupling agent is 1:(0.01-0.5); further preferably, the coupling agent is one or more selected from the group consisting of chromium complex coupling agents, silane coupling agents and titanate coupling agents.

[0033] Furthermore, the second slurry also includes a second dispersant; preferably, the second slurry includes 0.5 to 1 parts of matrix resin A and 5 to 10 parts of the second dispersant by weight; preferably, the second dispersant is selected from phenolic epoxy resin, more preferably a phenolic epoxy resin with an epoxy value of 0.44 to 0.8; preferably, the matrix resin A is selected from thermoplastic resins, more preferably one or more of the group consisting of polyvinylidene fluoride, polyvinyl alcohol and polytetrafluoroethylene; further preferably, one or more of the group consisting of polyvinylidene fluoride with a weight average molecular weight of 390,000 to 690,000, polyvinyl alcohol with a weight average molecular weight of 60,000 to 150,000 and polytetrafluoroethylene with a weight average molecular weight of 100,000 to 1,000,000.

[0034] Furthermore, the second slurry also includes a second auxiliary dispersant, and the weight ratio of the second dispersant to the second auxiliary dispersant is 1:(0.01~0.05); more preferably, the second auxiliary dispersant is selected from a styrene-butadiene rubber aqueous solution and / or polyacrylamide, and further preferably a styrene-butadiene rubber aqueous solution with a solid content of 35~55% and / or a polyacrylamide with a weight average molecular weight of 500,000~20,000,000.

[0035] Furthermore, the first drying temperature is 50-100° C., and the time is 12-60 minutes.

[0036] Furthermore, the second drying temperature is 55 to 85° C., and the time is 6 to 30 minutes.

[0037] Furthermore, in step S1, the metal conductive layer is prepared by a wet method or a dry method.

[0038] Furthermore, the coating process in step S2 is performed by a coating method.

[0039] Furthermore, the coating process in step S3 is performed by a coating method.

[0040] Furthermore, the material of the metal tab is selected from one or more of the group consisting of nickel, copper, and aluminum.

[0041] Another aspect of the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode and / or the negative electrode comprises the above-mentioned battery electrode provided in the present application, or a battery electrode produced by the preparation method of the above-mentioned battery electrode provided in the present application.

[0042] Furthermore, the lithium-ion battery is selected from a laminated battery, a square battery or a cylindrical battery.

[0043] By applying the technical solution of the present invention, the above-mentioned laminate provided by this application has the above-mentioned specific structure. During the research process, the inventor creatively discovered that during the welding process, the metal material in the welding auxiliary layer vibrates violently due to the absorption of heat, and the welding auxiliary layer and the metal conductive layer are transformed into a molten state with viscoelasticity, and then cooled to form a welding area, thereby completing the connection between each laminate and the metal tab. Since free electrons can move freely in the welding area, the resulting battery electrode has good conductivity. Moreover, the provision of the protective layer can inhibit the splashing of materials during the welding process, reduce the impact and damage of the welding process on the structure itself, and the protective layer also has the functions of anti-oxidation and water vapor barrier, which can improve the storage stability of the battery electrode.

[0044] In summary, using the above-mentioned laminate provided in this application to prepare battery pole pieces can effectively improve the welding processing effect of the battery pole pieces, reduce the internal resistance of the battery pole pieces, and use it in lithium-ion batteries to improve the electrochemical performance of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0046] Figure 1 A schematic structural diagram of a laminated structure including a protective layer in a preferred embodiment of the present application is shown;

[0047] Figure 2 A schematic structural diagram of a battery electrode in a preferred embodiment of the present application is shown.

[0048] The above drawings include the following reference numerals:

[0049] 10. Lamination; 20. Base material layer; 30. Metal conductive layer; 40. Welding auxiliary layer; 50. Protective layer; 60. Metal tab. DETAILED DESCRIPTION

[0050] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0051] As described in the background art, existing composite current collectors and metal tabs have the problem of high welding difficulty, resulting in poor welding effect and high internal resistance of battery pole pieces. In order to solve the above technical problems, the first aspect of this application provides a laminate, such as Figure 1As shown, the laminate 10 includes: a substrate layer 20, a metal conductive layer 30, a welding auxiliary layer 40 and a protective layer 50; the material of the substrate layer 20 is selected from organic polymer materials; the metal conductive layer 30 is arranged on both side surfaces of the substrate layer 20; the welding auxiliary layer 40 is arranged on the surface of the metal conductive layer 30 away from the substrate layer 20; the material of the welding auxiliary layer 40 includes a metal material; the protective layer 50 is arranged on the surface of the welding auxiliary layer 40 away from the metal conductive layer 30; the material of the protective layer 50 includes a matrix resin A.

[0052] Conventional composite current collectors have a "sandwich" structure, comprising a substrate layer 20 and metal conductive layers 30 disposed on either side of the substrate layer 20. However, conventional welding methods make it difficult to weld multiple composite current collectors to each other and to the metal tabs 60, resulting in poor welding performance. This, in turn, leads to higher resistance in the battery electrode, affecting the electrochemical performance of the lithium-ion battery.

[0053] The above-mentioned laminate 10 provided in the present application has the above-mentioned specific structure. During the research process, the inventor creatively discovered that during the welding process, the metal material in the welding auxiliary layer 40 vibrates violently due to the absorption of heat, and the welding auxiliary layer 40 and the metal conductive layer 30 are transformed into a molten state with viscoelasticity, and then cooled to form a welding area, thereby completing the connection between each laminate 10 and the metal tab 60. Since free electrons can move freely in the welding area, the resulting battery electrode has good conductivity. Moreover, the provision of the protective layer 50 can inhibit the splashing of materials during the welding process, reduce the impact and damage of the welding process on the structure itself, and the protective layer 50 also has the functions of anti-oxidation and water vapor barrier, which can improve the storage stability of the battery electrode.

[0054] In summary, using the above-mentioned laminate 10 provided in this application to prepare battery pole pieces can effectively improve the welding processing effect of the battery pole pieces, reduce the internal resistance of the battery pole pieces, and use it in lithium-ion batteries to improve the electrochemical performance of lithium-ion batteries.

[0055] In a preferred embodiment, the metal material includes, but is not limited to, one or more metal elements from the group consisting of elements from Groups VIII, IVB, IB, VIB, IA, IIA, IIIA, IVA, and IIB; and / or one or more alloys from the group consisting of copper alloys, aluminum alloys, nickel alloys, titanium alloys, and cobalt alloys. Compared to other types, the use of these metal materials facilitates better utilization of the welding auxiliary layer 40, improves welding performance during battery electrode fabrication, reduces welding difficulty, and thus helps reduce the internal resistance of the battery electrode and enhance the electrochemical performance of the lithium-ion battery.

[0056] In order to further improve the welding treatment effect and further reduce the welding difficulty, preferably, the metal element includes but is not limited to one or more of the group consisting of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In and Zn; the alloy includes but is not limited to one or more of the group consisting of copper alloy, aluminum alloy and nickel alloy.

[0057] In order to further enhance the conductive properties of the metal material and improve the welding process, preferably, the D50 of the metal material is 1 to 10 μm. The D50 of the metal material refers to the particle size value of the metal material corresponding to the cumulative distribution percentage reaching 50% in the particle size distribution curve.

[0058] In a preferred embodiment, matrix resin A includes, but is not limited to, a thermoplastic resin, preferably one or more of the group consisting of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene, and more preferably one or more of the group consisting of polyvinylidene fluoride with a weight-average molecular weight of 390,000 to 690,000, polyvinyl alcohol with a weight-average molecular weight of 60,000 to 150,000, and polytetrafluoroethylene with a weight-average molecular weight of 100,000 to 1,000,000. Compared to other types, using these matrix resins facilitates melting during welding, thereby improving welding quality and, in turn, reducing the internal resistance of the battery electrode.

[0059] In a preferred embodiment, the substrate layer 20 includes, but is not limited to, polyethylene terephthalate film (PET) or biaxially oriented polypropylene film (BOPP). Compared to other types, the use of these substrate layers 20 helps reduce the weight of the battery and improves the flexibility of the battery electrode. When the lithium-ion battery is impacted by foreign objects, the substrate layer 20 can wrap around the fracture surface, thereby preventing the fracture from piercing the separator and causing a short circuit, thereby improving the safety performance of the battery.

[0060] In order to reduce the weight of the battery and improve the flexibility of the battery electrode without affecting its conductivity, preferably, the thickness of the substrate layer 20 is 4.5 to 8 μm, more preferably 4.5 to 6 μm.

[0061] In order to improve the conductivity of the battery electrode, preferably, the thickness of the metal conductive layer 30 is 0.5 to 3 μm.

[0062] In order to improve the effect of the welding process and enhance the conductivity of the battery electrode, preferably, the thickness of the welding auxiliary layer 40 is 2 to 20 μm.

[0063] In a preferred embodiment, the thickness of the protective layer 50 is 0.5 to 5 μm. The thickness of the protective layer 50 includes but is not limited to the above range. Limiting the thickness of the protective layer 50 within the above range is beneficial to exerting the anti-oxidation and moisture-proof properties of the protective layer 50 and is also beneficial to suppressing the spatter of the welding material.

[0064] A second aspect of the present application further provides a battery electrode sheet comprising a plurality of welded laminates 10, wherein the laminates 10 are the aforementioned laminates 10 provided in the present application. The battery electrode sheet further comprises a metal tab 60, which is welded to the outermost end of the plurality of laminates 10. Compared to conventional composite current collectors, the battery electrode sheet comprising the aforementioned laminates 10 provided in the present application can effectively improve the welding process during the preparation of the battery electrode sheet, thereby reducing the internal resistance of the battery electrode sheet and improving its conductivity. Application of the battery electrode sheet in a lithium-ion battery can improve the electrochemical performance and cycling stability of the lithium-ion battery.

[0065] The third aspect of the present application also provides a method for preparing a battery electrode sheet, which comprises: step S1, preparing at least one metal conductive layer 30 on both sides of the substrate layer 20 to obtain a laminated structure; the material of the substrate layer 20 is selected from an organic polymer material; step S2, applying a first slurry containing a metal material to the surface of the metal conductive layer 30 away from the substrate layer 20, and obtaining a laminated structure containing a welding auxiliary layer 40 after a first drying; step S3, applying a second slurry containing a matrix resin A to the surface of the welding auxiliary layer 40 away from the metal conductive layer 30, and obtaining a laminated structure after a second drying. Figure 1 Step S4, stacking a plurality of stacked structures containing a protective layer 50 to obtain a laminate 10, and stacking a metal tab 60 (such as Figure 2 As shown), the battery electrode is obtained after welding.

[0066] Based on a conventional composite current collector, this application first applies a first slurry containing a metal material, which is dried to form a welding auxiliary layer 40. A second slurry containing a matrix resin A is then applied, which is dried to form a protective layer 50. Finally, multiple laminated structures containing protective layers 50 are stacked to form a laminate 10. A metal tab 60 is then stacked at the outermost end of the laminate 10. After welding, the battery electrode provided by this application is obtained. During research, the inventors creatively discovered that during the welding process, the metal material in the welding auxiliary layer 40 vibrates violently due to the absorption of heat, and the welding auxiliary layer 40 and the metal conductive layer 30 transform into a molten state with viscoelasticity. Subsequently, the welding region is formed upon cooling, thereby completing the connection between the laminates 10 and the metal tab 60. Because free electrons can freely move within the welding region, the resulting battery electrode has excellent conductivity. Furthermore, the provision of the protective layer 50 can suppress material splashing during the welding process, reducing the impact and damage of the welding process on the structure itself. The protective layer 50 also has antioxidant and moisture barrier properties, which can improve the storage stability of the battery electrode.

[0067] In summary, the above-mentioned preparation method provided in this application can effectively improve the welding effect of the battery pole piece, reduce the internal resistance of the battery pole piece, and apply it in lithium-ion batteries to improve the electrochemical performance of lithium-ion batteries.

[0068] Ultrasonic welding is a welding method that uses a metal welding head to apply high-frequency and low-amplitude vibrations at the interface of the connection surface of the welding material, thereby first generating frictional heat at the welding interface, and then generating viscoelastic heat internally through frictional heat, thereby connecting the materials together. In a preferred embodiment, ultrasonic welding is used for welding, and the welding frequency is 2000-38000 Hz, the amplitude is 5-95%, the welding pressure is 0.2-0.8 MPa, and the welding time is 0.1-0.4 s. Compared with other ranges, limiting the frequency, amplitude, welding pressure and welding time in the ultrasonic welding process to the above range is conducive to improving the welding effect, thereby helping to reduce the internal resistance of the battery electrode and improve the electrochemical performance of the lithium-ion battery.

[0069] Laser welding utilizes the absorption of laser radiation by the materials being welded, causing the materials to melt and then cool and solidify, ultimately welding the materials together. In a preferred embodiment, laser welding is performed using a power of 500-1000W, a welding rate of 30-60mm / s, and a welding time of 0.1-5s. Limiting the laser welding process parameters to the aforementioned ranges improves welding performance compared to other ranges, thereby reducing the internal resistance of the battery electrode and enhancing the electrochemical performance of lithium-ion batteries.

[0070] In a preferred embodiment, the welding process is performed using a riveting method, with a riveting welding head having a diameter of 1 to 15 mm and a welding temperature of 800 to 1400°C. Limiting the laser welding process parameters within the above ranges, compared to other ranges, is beneficial for improving the welding effect, thereby reducing the internal resistance of the battery electrode and improving the electrochemical performance of the lithium-ion battery.

[0071] In order to further improve the welding effect and reduce the introduction of impurities, the welding process is preferably performed in an inert atmosphere.

[0072] In a preferred embodiment, the number of laminates 10 in step S4 is n, where n is any integer between 5 and 70. Compared to other ranges, limiting the value of n to the above range is beneficial for improving welding performance, reducing welding internal resistance, and increasing the straight pull force of the battery electrode sheet, while also providing better protection for the welding head of the welding equipment.

[0073] In a preferred embodiment, the metal material in the first slurry includes, but is not limited to, one or more metal elements from the group consisting of elements from Groups VIII, IVB, IB, VIB, IA, IIA, IIIA, IVA, and IIB; and / or one or more alloys from the group consisting of copper alloys, aluminum alloys, nickel alloys, titanium alloys, and cobalt alloys. Compared to other types, the use of these metal materials facilitates better utilization of the welding auxiliary layer 40 to improve welding processing, reduces welding difficulty, and thus helps reduce the internal resistance of the battery electrode and improve the electrochemical performance of the lithium-ion battery.

[0074] In order to further improve the welding treatment effect and further reduce the welding difficulty, preferably, the metal element includes but is not limited to one or more of the group consisting of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In and Zn; the alloy includes but is not limited to one or more of the group consisting of copper alloy, aluminum alloy and nickel alloy.

[0075] In order to further enhance the conductive properties of the metal material and further improve the welding process effect, preferably, the D50 of the metal material is 1 to 10 μm.

[0076] In a preferred embodiment, the first slurry further includes a first dispersant and a matrix resin B. The introduction of the first dispersant can improve the surface properties of the metal material, enhance its dispersibility, and improve the coating processability of the first slurry; the introduction of the matrix resin B can improve the dispersibility of the metal material and also enable the metal slurry to better adhere to the surface of the metal conductive layer 30, thereby improving the welding process effect.

[0077] In order to further enhance the role of the welding auxiliary layer 40 in promoting welding and further improve the welding effect, preferably, the first slurry includes 5 to 10 parts of metal material, 5 to 10 parts of the first dispersant and 0.5 to 1 part of the base resin B by weight.

[0078] In order to further improve the dispersibility of the metal material, preferably, the first dispersant includes but is not limited to a novolac epoxy resin, more preferably a novolac epoxy resin with an epoxy value of 0.44 to 0.8.

[0079] In a preferred embodiment, matrix resin B includes, but is not limited to, a thermoplastic resin, more preferably one or more of the group consisting of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene, and even more preferably one or more of the group consisting of polyvinylidene fluoride with a weight-average molecular weight of 390,000 to 690,000, polyvinyl alcohol with a weight-average molecular weight of 60,000 to 150,000, and polytetrafluoroethylene with a weight-average molecular weight of 100,000 to 1,000,000. Compared to other types, the use of these resins facilitates melting during welding, thereby improving welding quality and, in turn, reducing the internal resistance of the battery electrode.

[0080] In a preferred embodiment, the first slurry further includes one or more of the group consisting of a first auxiliary dispersant, a curing agent, an accelerator, and a coupling agent. The introduction of the first auxiliary dispersant can improve the dispersibility of the metal material; the introduction of the curing agent can improve the structural stability of the welding auxiliary layer 40 formed after the first slurry is applied, and improve the cross-linking and curing performance of the welding auxiliary layer 40, thereby promoting the subsequent welding process; the introduction of the accelerator can improve the curing performance of the first slurry; the introduction of the coupling agent can improve the cross-linking and curing performance of the welding auxiliary layer 40, thereby improving its structural stability and promoting the subsequent welding process.

[0081] In order to further improve the dispersibility of the metal material and further improve the coating processability of the first slurry, preferably, in the first slurry, the weight ratio of the metal material to the first auxiliary dispersant is 1:(0.1~0.5); further preferably, the first auxiliary dispersant is selected from a styrene-butadiene rubber aqueous solution and / or polyacrylamide, and further preferably a styrene-butadiene rubber aqueous solution with a solid content of 35~55% and / or a polyacrylamide with a weight average molecular weight of 5000000~20000000.

[0082] In order to further improve the structural stability of the welding auxiliary layer 40 and improve the cross-linking and curing performance of the welding auxiliary layer 40 , preferably, in the first slurry, the weight ratio of the metal material to the curing agent is 1:(0.01-0.1).

[0083] The curing agent used in this application can be a light curing agent and / or a heat curing agent commonly used in the art. In a preferred embodiment, the curing agent includes but is not limited to diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide and / or 2,2-azobisisobutyronitrile.

[0084] In order to further promote the cross-linking and curing of the welding auxiliary layer 40, preferably, in the first slurry, the weight ratio of the metal material to the accelerator is 1:(0.01-0.5); further preferably, the accelerator includes but is not limited to polyetheramine and / or acrylate.

[0085] In order to further promote the cross-linking and curing of the welding auxiliary layer 40, preferably, in the first slurry, the weight ratio of the metal material to the coupling agent is 1:(0.01~0.5); further preferably, the coupling agent includes but is not limited to one or more of the group consisting of chromium complex coupling agents, silane coupling agents and titanate coupling agents.

[0086] In order to improve the coating processability of the second slurry, in a preferred embodiment, the second slurry further includes a second dispersant.

[0087] In a preferred embodiment, the second slurry comprises, by weight, 0.5-1 parts of base resin A and 5-10 parts of a second dispersant. Compared to other amounts, the second slurry using this ratio facilitates better performance of the protective layer 50, thereby improving the protective layer's antioxidant and moisture-proof properties and suppressing material spatter during welding.

[0088] In order to further improve the compatibility of the components in the second slurry, preferably, the second dispersant includes but is not limited to a novolac epoxy resin, more preferably a novolac epoxy resin with an epoxy value of 0.44 to 0.8.

[0089] In a preferred embodiment, matrix resin A includes, but is not limited to, a thermoplastic resin, preferably one or more of the group consisting of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene, and more preferably one or more of the group consisting of polyvinylidene fluoride with a weight-average molecular weight of 390,000 to 690,000, polyvinyl alcohol with a weight-average molecular weight of 60,000 to 150,000, and polytetrafluoroethylene with a weight-average molecular weight of 100,000 to 1,000,000. Compared to other types, using the aforementioned matrix resin A further improves the anti-oxidation and moisture-proof properties of protective layer 50 and further suppresses material spatter during welding.

[0090] In order to further improve the compatibility of the components in the second slurry and further improve the coating processability of the second slurry, preferably, the second slurry also includes a second auxiliary dispersant, and the weight ratio of the second dispersant to the second auxiliary dispersant is 1:(0.01~0.05); more preferably, the second auxiliary dispersant includes but is not limited to a styrene-butadiene rubber aqueous solution and / or polyacrylamide, and further preferably a styrene-butadiene rubber aqueous solution with a solid content of 35~55% and / or a polyacrylamide with a weight average molecular weight of 500,000~20,000,000.

[0091] In a preferred embodiment, the first drying temperature is 50-100°C, preferably 55-80°C, and the drying time is 12-60 minutes. The temperature and time of the first drying include, but are not limited to, the above ranges. Limiting the first drying temperature and time within the above ranges helps to better utilize the welding auxiliary layer 40 to improve the welding effect, reduce the internal resistance of the battery electrode, and thus improve the electrochemical performance of the lithium-ion battery.

[0092] In a preferred embodiment, the second drying temperature is 55-85°C, preferably 55-75°C, and the drying time is 6-30 minutes. The second drying temperature and time include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial for improving the crosslinking and curing performance of the protective layer 50 and the bonding strength between the protective layer 50 and the welding auxiliary layer 40, thereby facilitating the antioxidant and moisture-proof properties of the protective layer 50.

[0093] In a preferred embodiment, in step S1, the metal conductive layer 30 is prepared using a wet or dry method. Using the above method to prepare the metal conductive layer 30 facilitates the subsequent coating of the second slurry and subsequent drying and soldering. For example, physical vapor deposition, evaporation deposition, sputtering deposition, and laser deposition methods are used.

[0094] In a preferred embodiment, the coating process in step S2 is performed using a coating method. The coating method allows for the first slurry containing the metal material to be quickly and conveniently applied to the surface of the metal conductive layer 30 away from the substrate layer 20, thereby forming a laminated structure including the soldering auxiliary layer 40. For example, manual coating or roller coating can be used.

[0095] In a preferred embodiment, the coating process in step S3 is performed using a coating method. The coating method allows for the convenient and rapid application of the second slurry containing the matrix resin to the surface of the welding auxiliary layer 40 away from the metal conductive layer 30, thereby forming a laminated structure including the protective layer 50. For example, manual coating or roller coating can be used.

[0096] In a preferred embodiment, the material of the metal tab 60 is selected from one or more of the group consisting of nickel, copper, and aluminum. The material of the metal tab 60 includes but is not limited to the above range, which is conducive to improving the conductivity of the battery electrode.

[0097] In a fourth aspect, the present application further provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode and / or the negative electrode comprises the battery electrode sheet provided herein, or a battery electrode sheet produced by the method for producing the battery electrode sheet provided herein. The battery electrode sheet provided herein has excellent conductivity and low internal resistance, and its application in a lithium-ion battery can effectively improve its electrochemical performance.

[0098] In a preferred embodiment, the lithium-ion battery includes but is not limited to a laminated battery, a square battery or a cylindrical battery.

[0099] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0100] Example 1

[0101] A method for preparing a battery electrode, comprising:

[0102] (1) Preparing a 6 μm thick PET substrate layer 20, and physically vapor depositing a 1 μm thick copper layer on both sides of the substrate layer 20 as a metal conductive layer 30 to obtain a laminated structure;

[0103] (2) Weighing 50 g of copper powder, 50 g of phenolic epoxy resin (epoxy value 0.5), 5 g of polyvinylidene fluoride, 0.5 g of polyacrylamide, and 5 g of styrene-butadiene rubber aqueous solution (solid content 50%), stirring at room temperature for 12 h to obtain a first slurry containing a single copper element; wherein the D50 of the copper powder is 1 to 2 μm, the weight average molecular weight of the polyvinylidene fluoride is 400,000, and the weight average molecular weight of the polyacrylamide is 520,000; coating the first slurry on the side of the copper layer away from the PET, and drying at 65° C. for 30 min to obtain a laminated structure containing a welding auxiliary layer 40; the thickness of the welding auxiliary layer 40 is 15 μm;

[0104] (3) Weigh 50 g of phenolic epoxy resin, 0.5 g of polyacrylamide, and 5 g of polyvinylidene fluoride, and stir at room temperature for 12 h to obtain a second slurry containing a matrix resin; wherein the epoxy value of the phenolic epoxy resin is 0.5, the weight average molecular weight of the polyacrylamide is 550,000, and the weight average molecular weight of the polyvinylidene fluoride is 400,000; apply the above second slurry on the side of the welding auxiliary layer 40 away from the copper layer, and dry it at 55° C. for 30 min to obtain a laminated structure containing a protective layer 50; the thickness of the protective layer 50 is 1 μm;

[0105] (4) Repeat the above steps (1) to (3) to obtain 55 laminated structures containing the protective layer 50 prepared above, stack them to obtain 55 laminated sheets 10, and stack a metal pole ear 60 at one end of the outermost layer of the laminate 10. The material of the metal pole ear 60 is copper, and the battery pole sheet is obtained after ultrasonic welding; wherein, argon and helium are used for protection during the welding process, the welding frequency is 30000 Hz, the amplitude is 75%, the welding pressure is 0.6 MPa, and the welding time is 0.4 s.

[0106] Example 2

[0107] The difference from Example 1 is that the coating amount of the first slurry in step (2) is changed so that the thickness of the prepared welding auxiliary layer 40 is 2 μm.

[0108] Example 3

[0109] The difference from Example 1 is that the coating amount of the first slurry in step (2) is changed so that the thickness of the prepared welding auxiliary layer 40 is 20 μm.

[0110] Example 4

[0111] The difference from Example 1 is that the coating amount of the first slurry in step (2) is changed so that the thickness of the prepared welding auxiliary layer 40 is 30 μm.

[0112] Example 5

[0113] The difference from Example 1 is that the metal material in the first slurry is copper-nickel alloy.

[0114] Example 6

[0115] The difference from Example 1 is that the matrix resin B is polytetrafluoroethylene, and its weight average molecular weight is 1,000,000.

[0116] Example 7

[0117] A method for preparing a battery electrode, comprising:

[0118] Steps (1) to (3) are the same as those in Example 1, and a laminated structure including a protective layer 50 is obtained;

[0119] (4) 55 of the above-mentioned laminated structures containing the protective layer 50 are stacked to obtain 55 laminated sheets 10, and a metal pole ear 60 is stacked at one end of the outermost layer of the laminate 10. The material of the metal pole ear 60 is aluminum, and the battery pole sheet is obtained after laser welding; wherein, argon and helium are used for protection during the welding process, the welding power is 700 W, the welding rate is 50 mm / s, and the welding time is 0.4 s.

[0120] Example 8

[0121] The difference from Example 7 is that the coating amount of the first slurry in step (2) is changed so that the thickness of the prepared welding auxiliary layer 40 is 2 μm.

[0122] Example 9

[0123] The difference from Example 7 is that the coating amount of the first slurry in step (2) is changed so that the thickness of the prepared welding auxiliary layer 40 is 20 μm.

[0124] Example 10

[0125] The difference from Example 7 is that the coating amount of the first slurry in step (2) is changed so that the thickness of the prepared welding auxiliary layer 40 is 30 μm.

[0126] Example 11

[0127] The difference from Example 7 is that the metal material in the first slurry is copper-nickel alloy.

[0128] Example 12

[0129] The difference from Example 7 is that the matrix resin B is polytetrafluoroethylene, and its weight average molecular weight is 900,000.

[0130] Example 13

[0131] The difference from Example 1 is that in step (4), the number of laminates 10 is 5.

[0132] Example 14

[0133] The difference from Example 1 is that in step (4), the number of laminates 10 is 70.

[0134] Example 15

[0135] The difference from Example 1 is that in step (4), the number of laminates 10 is 90.

[0136] Comparative Example 1

[0137] The difference from Example 1 is that steps (2) and (3) are omitted, and ultrasonic welding is directly performed on the laminated structure of 55 copper-containing layers stacked in step (1) and the metal tab 60 (copper tab).

[0138] Comparative Example 2

[0139] The difference from Example 7 is that steps (2) and (3) are omitted, and the laminated structure of 55 copper-containing layers prepared in step (1) and the metal tab 60 (aluminum tab) are directly laser welded.

[0140] The battery electrode prepared above in this application was used as the negative electrode, the nickel-cobalt-manganese ternary 811 system was used as the positive electrode, a ceramic diaphragm was used as the separator, and a 1 mol / L LiPF6 electrolyte (containing additives such as EC / DC / EMC) was used to assemble a laminated battery. The internal resistance and cycle stability of the laminated battery were tested. The mechanical properties of the battery electrode were tested using a tensile test machine, and the tensile force corresponding to a tensile length of 15 mm was measured. The cycle stability test conditions are as follows: the voltage range is 3 to 4.2 V. The test results are shown in Table 1.

[0141] Table 1

[0142]

[0143] From the above description, it can be seen that the above-mentioned embodiment of the present invention achieves the following technical effects: the above-mentioned laminate 10 provided in this application has the above-mentioned specific structure. During the research process, the inventor creatively discovered that during the welding process, the metal material in the welding auxiliary layer 40 vibrates violently due to the absorption of heat, and the welding auxiliary layer 40 and the metal conductive layer 30 are transformed into a molten state with viscoelasticity, and then cooled to form a welding area, thereby completing the connection between each laminate 10 and the metal tab 60. Since free electrons can move freely in the welding area, the resulting battery electrode has good conductivity. Moreover, the provision of the protective layer 50 can inhibit the splashing of materials during the welding process, reduce the impact and damage of the welding process on the structure itself, and the protective layer 50 also has the function of anti-oxidation and water vapor barrier, which can improve the storage stability of the battery electrode.

[0144] In summary, using the above-mentioned laminate 10 provided in this application to prepare battery pole pieces can effectively improve the welding processing effect of the battery pole pieces, reduce the internal resistance of the battery pole pieces, and use it in lithium-ion batteries to improve the electrochemical performance of lithium-ion batteries.

[0145] It should be noted that the terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in an order other than that described herein.

[0146] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A laminate, characterized in that: The laminate (10) comprises: a substrate layer (20), wherein the material of the substrate layer (20) is selected from organic polymer materials; A metal conductive layer (30), the metal conductive layer (30) being arranged on both side surfaces of the substrate layer (20); a welding auxiliary layer (40), the welding auxiliary layer (40) being arranged on a surface of the metal conductive layer (30) away from the base material layer (20); the material of the welding auxiliary layer (40) comprises a metal material; A protective layer (50) is provided on a surface of the welding auxiliary layer (40) away from the metal conductive layer (30); the material of the protective layer (50) includes a matrix resin A.

2. The laminate according to claim 1, wherein: The metal material is one or more metal elements selected from the group consisting of elements in Group VIII, Group IVB, Group IB, Group VIB, Group IA, Group IIA, Group IIIA, Group IVA, and Group IIB; and / or one or more alloys selected from the group consisting of copper alloys, aluminum alloys, nickel alloys, titanium alloys, and cobalt alloys; Preferably, the metal element is selected from one or more of the group consisting of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In and Zn; Preferably, the alloy is selected from one or more of the group consisting of copper alloy, aluminum alloy and nickel alloy; Preferably, the D50 of the metal material is 1-10 μm.

3. The laminate according to claim 1, wherein: The matrix resin A is selected from thermoplastic resins, preferably one or more of the group consisting of polyvinylidene fluoride, polyvinyl alcohol and polytetrafluoroethylene, more preferably one or more of the group consisting of polyvinylidene fluoride with a weight average molecular weight of 390,000 to 690,000, polyvinyl alcohol with a weight average molecular weight of 60,000 to 150,000 and polytetrafluoroethylene with a weight average molecular weight of 100,000 to 1,000,000.

4. The laminate according to any one of claims 1 to 3, characterized in that The substrate layer (20) is selected from polyethylene terephthalate film or biaxially oriented polypropylene film; and / or, The thickness of the substrate layer (20) is 4.5 to 8 μm, preferably 4.5 to 6 μm; and / or, The thickness of the metal conductive layer (30) is 0.5 to 3 μm; and / or, The thickness of the welding auxiliary layer (40) is 2 to 20 μm; and / or, The thickness of the protective layer (50) is 0.5-5 μm.

5. A battery pole piece, characterized in that: The battery electrode sheet includes a plurality of laminates (10) connected by welding, and the laminate (10) is the laminate (10) according to any one of claims 1 to 4. The battery electrode sheet also includes a metal tab (60), and the metal tab (60) is welded and arranged at the outermost end of the plurality of laminates (10).

6. A method for preparing a battery electrode according to claim 5, characterized in that: The method for preparing the battery electrode comprises: Step S1, preparing at least one metal conductive layer (30) on both sides of the substrate layer (20) to obtain a laminated structure; the material of the substrate layer (20) is selected from organic polymer materials; Step S2, coating a first slurry containing a metal material on a surface of the metal conductive layer (30) away from the substrate layer (20), and obtaining a laminated structure containing a welding auxiliary layer (40) after a first drying process; Step S3, coating a second slurry containing matrix resin A on a surface of the welding auxiliary layer (40) away from the metal conductive layer (30), and obtaining a laminated structure containing a protective layer (50) after a second drying; Step S4, stacking a plurality of the laminated structures containing the protective layer (50) to obtain a laminate (10), and stacking a metal tab (60) at the outermost end of the laminate (10), and obtaining the battery electrode after welding.

7. The method for preparing a battery electrode according to claim 6, characterized in that: The welding process is performed by ultrasonic welding, wherein the frequency of the welding process is 2000-38000 Hz, the amplitude is 5-95%, the welding pressure is 0.2-0.8 MPa, and the welding time is 0.1-0.4 s; and / or, The welding process is performed by laser welding, the power of the welding process is 500-1000W, the welding rate is 30-60mm / s, and the welding time is 0.1-5s; and / or, The welding process is performed by riveting welding, the diameter of the riveting welding head used in the welding process is 1 to 15 mm, and the welding temperature is 800 to 1400° C. Preferably, the welding process is performed in an inert atmosphere.

8. The method for preparing a battery electrode according to claim 6, characterized in that: The first drying temperature is 50-100° C., and the time is 12-60 min; and / or the second drying temperature is 55-85° C., and the time is 6-30 min.

9. The method for preparing a battery pole piece according to any one of claims 6 to 8, characterized in that: In the step S1, the metal conductive layer (30) is prepared by a wet method or a dry method; and / or, The coating process in step S2 is performed by a coating method; and / or, The coating process in step S3 is performed by a coating method; and / or, The material of the metal tab (60) is selected from one or more of the group consisting of nickel, copper, and aluminum.

10. A lithium-ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein: The positive electrode and / or the negative electrode comprises the battery electrode sheet according to claim 5, or a battery electrode sheet prepared by the method for preparing a battery electrode sheet according to any one of claims 6 to 9; Preferably, the lithium-ion battery is selected from a laminated battery, a square battery or a cylindrical battery.

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