Method for welding pole piece composite aluminum foil and pole lug and pole lug battery cell

Abstract

The invention provides a method for welding a pole piece composite aluminum foil and a pole lug, which comprises the following steps of: pre-welding, then performing main welding, and selecting main welding pressure, time, amplitude and thickness of an aluminum sheet according to M = 6.3084 ln (a) + 2520.57 b4.6551 + 6.2613 c-1. 7338 * 10 <-4 > d2 + 0.09525 d-30.262-0.1075 L (0.65 T + 0.15 P), the number of layers and thickness of the pole piece composite aluminum foil and the thickness of a non-metal layer of the pole piece composite aluminum foil in the main welding process, so that M is more than or equal to 1 and less than or equal to 1; a is the main welding time, b is the main welding pressure, c is the main welding amplitude, d is the main welding aluminum sheet thickness, L is the number of layers of the pole piece composite aluminum foil, T is the pole piece composite aluminum foil thickness, and P is the thickness of a non-metal layer of the pole piece composite aluminum foil.

Description

Technical Field

[0001] The invention relates to the field of battery materials, and in particular to a method for welding a pole piece composite aluminum foil to a pole tab and a pole tab battery cell. Background Art

[0002] Composite aluminum foil is an aluminum-plated composite film based on PET, PP, PI and other materials. Its organic insulating layer has a lower density than aluminum and can provide infinite internal resistance when the battery is in thermal runaway. When used in lithium-ion batteries, it can improve the energy density and safety of the battery to a certain extent. Therefore, the application of composite aluminum foil replacing traditional aluminum foil in lithium-ion batteries is gradually increasing.

[0003] Composite aluminum foil often faces multiple challenges during the welding process, which not only affect the quality of welding, but also may limit its widespread promotion in practical applications. At present, the welding method commonly used in the industry is to weld two layers of aluminum foil sandwiching a layer of composite aluminum foil, and then connect multiple layers of traditional aluminum foil with external aluminum tabs. Although this welding process is the current mainstream technology, its complexity cannot be ignored.

[0004] At the same time, the welding process is often affected by many factors, such as welding pressure, welding amplitude, thickness of the main welding aluminum sheet, and different material properties in the composite aluminum foil. Each link needs to be precisely controlled to ensure the firmness of the welding. However, in actual operation, any slight deviation may lead to loose welding, which in turn affects the stability and performance of the entire structure. This potential instability has undoubtedly brought obstacles to the commercial application of composite aluminum foil and limited its promotion and application in a wider range of fields.

[0005] Therefore, how to optimize the welding process and improve the reliability of welding has become an important topic of current research. Summary of the invention

[0006] In order to solve the problems of the prior art, the present invention provides a method for welding a pole piece composite aluminum foil and a pole ear, wherein the pole piece composite aluminum foil is pre-welded first and then mainly welded, and during the welding process, the main welding pressure, time, amplitude, aluminum sheet thickness, number of pole piece composite aluminum foil layers, thickness, and thickness of the non-metallic layer of the pole piece composite aluminum foil are controlled to satisfy M=6.3084ln(a)+2520.57b 4.6551 +6.2613c-1.7338*10 -4 d 2 +0.09525d-30.262-0.1075L (0.65T+0.15P), -1≤M≤1, ensures the reliability of welding between the electrode composite aluminum foil and the pole ear, improves the firmness of the welding, and optimizes the welding process.

[0007] In a first aspect, the present invention provides a method for welding a pole piece composite aluminum foil to a pole tab, wherein the pole piece composite aluminum foil is welded as a whole by pre-welding the pole piece of the stacked core to obtain a composite aluminum foil joint, and then the composite aluminum foil joint and the pole tab to be welded are welded by main welding to obtain a pole tab battery cell. During the main welding process, the main welding pressure, main welding time, main welding amplitude, and main welding aluminum sheet thickness parameters are selected according to the number and thickness of the pole piece composite aluminum foil layers and the thickness of the non-metallic layer of the pole piece composite aluminum foil so that M=6.3084ln(a)+2520.57b 4.6551 +6.2613c-1.7338*10 -4 d 2 +0.09525d-30.262-0.1075L(0.65T+0.15P), -1≤M≤1, to ensure that the welding strength and residual area meet the process standards, where a is the main welding time, b is the main welding pressure, c is the main welding amplitude, d is the main welding aluminum sheet thickness, L is the number of electrode composite aluminum foil layers, T is the electrode composite aluminum foil thickness, and P is the thickness of the electrode composite aluminum foil non-metallic layer.

[0008] As a further solution, the number of layers of the pole piece composite aluminum foil is less than 40.

[0009] As a further solution, the thickness of the pole piece composite aluminum foil is selected from 6-15 μm.

[0010] As a further solution, the thickness of the non-metallic layer of the pole piece composite aluminum foil is selected from 4-10 μm.

[0011] As a further solution, the main welding time is selected from 70-200ms.

[0012] As a further solution, the main welding pressure is selected from 0.15-0.30 bar.

[0013] As a further solution, the main welding amplitude is selected from 10%-99%.

[0014] As a further solution, the thickness of the main welding aluminum sheet is selected from 70-230 μm.

[0015] As a further solution, the pre-welding step is: first, the positive electrode sheet, the negative electrode sheet and the separator are stacked to obtain a stacked core, and then an additional layer of composite aluminum foil is placed on the outside of the first layer of electrode sheet composite aluminum foil and the last layer of electrode sheet composite aluminum foil of the stacked core, and a layer of pre-welded aluminum sheet is placed on the outside of the additional composite aluminum foil to perform pre-welding. After the pre-welding is completed, the additional wrapped composite aluminum foil and the pre-welded aluminum sheet are peeled off to obtain a composite aluminum foil joint.

[0016] In order to more accurately obtain the process parameters that satisfy the above relationship, those skilled in the art can select target conditions within the existing general tab welding condition range, which is conducive to eliminating other interferences under non-general conditions.

[0017] As a further solution, the additional composite aluminum foil is selected from 1-3 layers.

[0018] As a further solution, the additional composite aluminum foil is preferably 1 layer.

[0019] As a further solution, the thickness of the pre-welded aluminum sheet is selected from 50-200 μm.

[0020] As a further solution, the thickness of the pre-welded aluminum sheet is selected from 100-150 μm.

[0021] As a further solution, the pre-welding time, pre-welding pressure and pre-welding amplitude are not limited in principle, and can be selected from 20-100 ms pre-welding time, 0.05-0.3 bar pre-welding pressure and 5%-80% pre-welding amplitude.

[0022] As a further solution, the main welding step is to stack the main welding aluminum sheet, the composite aluminum foil joint, and the pole ear to be welded in sequence from bottom to top, and then weld the three to obtain a pole ear battery cell.

[0023] As a further solution, the thickness of the main welding aluminum sheet is equal to that of the electrode tab to be welded.

[0024] As a further solution, the thickness of the electrode tab to be welded is selected from 30-250 μm.

[0025] As a further solution, the width of the electrode ear to be welded and the main welding aluminum sheet is greater than the composite aluminum foil joint.

[0026] As a further solution, the welding head descending speed is selected from 5 to 50 mm / s.

[0027] As a further solution, the delay time is selected from 0.05 to 0.5 s.

[0028] As a further solution, the holding time is selected from 0.05 to 1 s.

[0029] As a further solution, the holding pressure is selected from 0.05 to 0.5 bar.

[0030] In a second aspect, the present invention further provides a tab battery cell welded using the method proposed by the present invention.

[0031] As a further solution, the tab battery cell includes a positive electrode sheet, a negative electrode sheet, a separator, and a tab.

[0032] As a further solution, the positive electrode sheet includes a positive electrode active material, a positive electrode binder, and a positive electrode conductor.

[0033] As a further solution, the positive electrode active material is not limited in principle. For example, the positive electrode active material can be selected from at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0034] As a further solution, the positive electrode binder may be selected from at least one of thermoplastic resins, acrylic resins, sodium carboxymethyl cellulose and styrene butadiene rubber.

[0035] As a further embodiment, the positive electrode conductor includes a crystalline carbon material and an amorphous carbon material.

[0036] As a further solution, the negative electrode sheet includes a negative electrode active material, a negative electrode binder, and a negative electrode conductor.

[0037] As a further solution, the negative electrode active material is not limited in principle, and for example, can be selected from at least one of carbon-based materials and silicon-based materials.

[0038] As a further solution, the carbon-based material includes a crystalline carbon-based material and an amorphous carbon-based material.

[0039] As a further solution, the negative electrode adhesive is not limited in principle, and technicians can select a corresponding negative electrode adhesive according to needs.

[0040] As a further solution, the type of the diaphragm is not limited in principle. For example, a single-layer or multi-layer diaphragm of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride can be selected.

[0041] As a further solution, the tab is selected from any one of copper, aluminum, nickel, stainless steel, nickel-cobalt alloy, zinc, nickel-cadmium alloy, and copper-nickel alloy.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] (1) The present invention provides a reliable method for welding a pole piece composite aluminum foil to a pole ear, by pre-welding first, then main welding, and in the main welding process according to M = 6.3084ln (a) + 2520.57b 4.6551 +6.2613c-1.7338*10 -4 d 2+0.09525d-30.262-0.1075L(0.65T+0.15P), -1≤M≤1 selects the corresponding main welding parameters to obtain a pole tab battery cell whose welding strength and residual area meet the process standards. The method for welding the pole piece composite aluminum foil and the pole tab provided by the present invention provides a reliable and simple selection method for selecting the main welding parameters in the welding process of the pole piece composite aluminum foil and the pole tab, thereby effectively improving the welding efficiency and reliability.

[0044] (2) The additional composite aluminum foil and pre-welded aluminum sheet in the pre-welding process help to ensure the effective welding of the composite aluminum foil joint and avoid the occurrence of over-welding and welding through, thereby improving the reliability of welding. At the same time, through pre-welding, the tedious steps of using the pole ears to clamp each layer of the pole piece composite aluminum foil in turn and then weld it in the traditional welding process are avoided, saving energy consumption, time, and labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0046] In the attached picture:

[0047] Figure 1 It is a schematic diagram of the positions of the electrode ear 1 to be welded, the composite aluminum foil joint 2, and the main welding aluminum sheet 3.

[0048] Among them, 1-the ear to be welded; 2-the composite aluminum foil joint; 3-the main welding aluminum sheet. DETAILED DESCRIPTION

[0049] The following is a description of terms or words, and unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0050] In this article, the term "pole piece composite aluminum foil" used in this article refers to a pole piece prepared using a composite aluminum foil as a current collector, and the exposed portion that is not coated with active materials is called the pole piece composite aluminum foil.

[0051] In this article, the term "composite aluminum foil joint" used in this article refers to the "pole piece composite aluminum foil" part that is welded together after the pole piece using the composite aluminum foil as the current collector is pre-welded after the core is stacked.

[0052] In this article, the term "tab battery cell" used herein refers to a battery cell in which the composite aluminum foil connector 2 is welded to the tab.

[0053] For ease of understanding, the present invention will be described in more detail below and examples of the present invention are given, but the scope of the present invention is not limited thereby.

[0054] In the first aspect, the present invention provides a method for welding a pole piece composite aluminum foil to a pole tab, wherein the pole piece composite aluminum foil is welded into a whole by pre-welding the pole piece of the stacked core to obtain a composite aluminum foil joint 2, and then the composite aluminum foil joint 2 and the pole tab to be welded are welded by main welding to obtain a pole tab battery cell. During the main welding process, the main welding pressure, main welding time, main welding amplitude, and main welding aluminum sheet thickness parameters are selected according to the number and thickness of the pole piece composite aluminum foil layers and the thickness of the non-metallic layer of the pole piece composite aluminum foil so that M=6.3084ln(a)+2520.57b 4.6551 +6.2613c-1.7338*10 -4 d 2 +0.09525d-30.262-0.1075L(0.65T+0.15P), -1≤M≤1, to ensure that the welding strength and residual area meet the process standards, where a is the main welding time, b is the main welding pressure, c is the main welding amplitude, d is the main welding aluminum sheet thickness, L is the number of electrode composite aluminum foil layers, T is the electrode composite aluminum foil thickness, and P is the thickness of the electrode composite aluminum foil non-metallic layer.

[0055] In this scheme, we first pre-weld the laminated pole piece composite aluminum foil into a composite aluminum foil joint 2 to preliminarily prepare a battery cell. On this basis, we perform main welding on the composite aluminum foil joint 2 to obtain a pole ear battery cell. In the actual welding process, the main welding pressure often affects the sliding resistance between the welding objects, thereby affecting the effectiveness of welding, and the main welding time affects the input energy, thereby affecting the effective welding area, and the amplitude will affect the amplitude and speed of vibration between the welding objects, thereby affecting the heat generated by friction and the degree of plastic deformation. The thickness of the main welding aluminum sheet will affect the uniformity of the clamping force distribution, the ability to preserve heat, and the welding stability of the main welding aluminum sheet itself. The thickness of the main pole piece composite aluminum foil, the number of layers, and the thickness of the non-metallic layer will affect the welding strength, the heat conduction capacity during welding, the welding time, and the friction between the welding objects during welding, thereby affecting the welding performance. Therefore, we proposed M = 6.3084ln(a) + 2520.57b 4.6551 +6.2613c-1.7338*10 -4 d 2+0.09525d-30.262-0.1075L(0.65T+0.15P), -1≤M≤1, among which, we comprehensively considered the interactive effects of main welding pressure, main welding time, main welding amplitude, main welding aluminum sheet thickness, number of pole piece composite aluminum foil layers, thickness of pole piece composite aluminum foil and thickness of non-metallic layer of pole piece composite aluminum foil on welding, and selected main welding pressure, main welding time, main welding amplitude and main welding aluminum sheet thickness parameters according to number and thickness of pole piece composite aluminum foil layers and thickness of non-metallic layer of pole piece composite aluminum foil to make 6.3084ln(a)+2520.57b 4.6551 +6.2613c-1.7338*10 -4 d 2 The absolute value of +0.09525d-30.262-0.1075L (0.65T+0.15P) is less than 1, which effectively ensures the effective welding area and welding strength, provides a selection method for the welding parameters between the composite aluminum foil and the tab, improves the welding reliability, and optimizes the welding efficiency.

[0056] As a further solution, the number of layers of the pole piece composite aluminum foil is less than 40.

[0057] As a further solution, the thickness of the pole piece composite aluminum foil is selected from 6-15 μm.

[0058] As a further solution, the thickness of the non-metallic layer of the pole piece composite aluminum foil is selected from 4-10 μm.

[0059] As a further solution, the main welding time is selected from 70-200ms.

[0060] As a further solution, the main welding pressure is selected from 0.15-0.30 bar.

[0061] As a further solution, the main welding amplitude is selected from 10%-99%.

[0062] As a further solution, the thickness of the main welding aluminum sheet is selected from 70-230 μm.

[0063] As an example of some optional parameters, the pre-welding step is: first, the positive electrode sheet, the negative electrode sheet and the diaphragm are stacked to obtain a stacked core, and then an additional layer of composite aluminum foil is placed on the outside of the first layer of electrode sheet composite aluminum foil and the last layer of electrode sheet composite aluminum foil of the stacked core, and a layer of pre-welded aluminum sheet is placed on the outside of the additional composite aluminum foil to perform pre-welding. After the pre-welding is completed, the additional wrapped composite aluminum foil and the pre-welded aluminum sheet are peeled off to obtain a composite aluminum foil joint 2.

[0064] After the battery cell stacking is completed, the stacked core electrodes are welded together through the electrode composite aluminum foil to obtain a battery cell. Before pre-welding, we first place an extra layer of composite aluminum foil on the outside of the first layer of electrode composite aluminum foil and the last layer of electrode composite aluminum foil of the stacked core, and peel it off after welding. This is because in the traditional welding process, the first layer of electrode composite aluminum foil and the last layer of electrode composite aluminum foil of the stacked core often cause unsuccessful welding or cold welding due to factors such as thermal expansion of internal materials. This solution ensures the effective welding of the first layer of electrode composite aluminum foil and the last layer of electrode composite aluminum foil by setting an extra layer of composite aluminum foil, and solves the problem of difficulty in welding the outermost layer of composite aluminum foil; secondly, a layer of pre-welded aluminum sheet is set on the outside of the extra composite aluminum foil, which can effectively protect the electrode composite aluminum foil and prevent over-welding or welding through. Under the joint coating of the extra composite aluminum foil and the pre-welded aluminum sheet, we effectively improve the reliability of welding and ensure the effective welding of the first layer and the last layer of the electrode composite aluminum foil of the stacked core.

[0065] In order to more accurately obtain the process parameters that satisfy the above relationship, those skilled in the art can select target conditions within the existing general tab welding condition range, which is conducive to eliminating other interferences under non-general conditions.

[0066] As examples of some optional parameters, the additional composite aluminum foil is selected from 1-3 layers.

[0067] As examples of some optional parameters, the additional composite aluminum foil is preferably 1 layer.

[0068] As examples of some optional parameters, the thickness of the pre-welded aluminum sheet is selected from 50-200 μm.

[0069] As examples of some optional parameters, the thickness of the pre-welded aluminum sheet is selected from 100-150 μm.

[0070] As examples of some optional parameters, the pre-welding time, pre-welding pressure, and pre-welding amplitude are not limited in principle. For example, the pre-welding time is selected from 20 to 100 ms, the pre-welding pressure is selected from 0.05 to 0.3 bar, and the pre-welding amplitude is selected from 5% to 80%.

[0071] As an example of some optional parameters, the main welding step is to stack the main welding aluminum sheet 3, the composite aluminum foil joint 2, and the to-be-welded pole ear 1 in sequence from bottom to top, and then weld the three to obtain a pole ear battery cell.

[0072] As examples of some optional parameters, the thickness of the main welding aluminum sheet 3 is equal to that of the electrode tab 1 to be welded.

[0073] As examples of some optional parameters, the thickness of the electrode tab 1 to be welded is selected from 30-250 μm.

[0074] As examples of some optional parameters, the width of the electrode ear 1 to be welded and the main welding aluminum sheet 3 is greater than the width of the composite aluminum foil joint 2.

[0075] As examples of some optional parameters, the base material of the composite aluminum foil is selected from any one of polyester, polypropylene, polyethylene, nylon, polyurethane, polystyrene, polyphenylene sulfide, polyphenylene ether, polyetheretherketone, and polyimide.

[0076] As examples of some optional parameters, the welding head descending speed is selected from 5 to 50 mm / s.

[0077] As some examples of optional parameters, the delay time is selected from 0.05 to 0.5 s.

[0078] As examples of some optional parameters, the holding time is selected from 0.05 to 1 s.

[0079] As examples of some optional parameters, the holding pressure is selected from 0.05 to 0.5 bar.

[0080] In a second aspect, the present invention further provides a tab battery cell welded using the method proposed by the present invention.

[0081] As examples of some optional parameters, the tab battery cell includes a positive electrode sheet, a negative electrode sheet, a separator, and a tab.

[0082] As examples of some optional parameters, the positive electrode sheet includes a positive electrode active material, a positive electrode binder, and a positive electrode conductor.

[0083] As examples of some optional parameters, the positive electrode active material is not limited in principle. For example, the positive electrode active material can be selected from at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0084] As examples of some optional parameters, the positive electrode binder may be selected from at least one selected from thermoplastic resin, acrylic resin, sodium carboxymethyl cellulose and styrene butadiene rubber.

[0085] As examples of some optional parameters, the thermoplastic resin includes at least one of polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ether, copolymers of ethylene-tetrafluoroethylene, copolymers of vinylidene fluoride-tetrafluoroethylene, copolymers of vinylidene fluoride-trifluoroethylene, copolymers of vinylidene fluoride-trichloroethylene, copolymers of vinylidene fluoride-fluoroethylene, copolymers of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene and polypropylene.

[0086] As examples of some optional parameters, the acrylic resin includes at least one of vinyl acrylate resin, methyl acrylate resin, butyl acrylate resin, acrylic styrene resin, acrylate resin, acrylate copolymer resin, acrylic resin, and acrylic emulsion resin.

[0087] As examples of some optional parameters, the positive electrode conductive agent includes crystalline carbon materials and amorphous carbon materials.

[0088] As examples of some optional parameters, the crystalline carbon material includes at least one of conductive graphite, carbon nanotubes, graphene, and reduced graphene oxide.

[0089] As examples of some optional parameters, the amorphous carbon material includes at least one of conductive carbon black, conductive carbon balls, and conductive carbon fibers.

[0090] As examples of some optional parameters, the negative electrode sheet includes a negative electrode active material, a negative electrode binder, and a negative electrode conductor.

[0091] As examples of some optional parameters, the negative electrode active material is not limited in principle, and for example, can be selected from at least one of carbon-based materials and silicon-based materials.

[0092] As examples of some optional parameters, the carbon-based material includes crystalline carbon-based material and amorphous carbon-based material.

[0093] As examples of some optional parameters, the crystalline carbon-based material includes graphite and graphene.

[0094] As examples of some optional parameters, the amorphous carbon-based material is selected from any one or more of hard carbon, soft carbon, carbon nanotubes, carbon black and carbon aerogel.

[0095] As examples of some optional parameters, the silicon-based material is selected from any one or more of elemental silicon, silicon carbide, silicon oxide, silicon nitride, and silicon-based alloy.

[0096] As examples of some optional parameters, the negative electrode adhesive is not limited in principle, and technicians can select a corresponding negative electrode adhesive according to needs.

[0097] As examples of some optional parameters, the negative electrode conductive agent is selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, conductive carbon black and carbon nanofibers.

[0098] As examples of some optional parameters, the type of the diaphragm is not limited in principle. For example, a single-layer or multi-layer diaphragm of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride can be selected.

[0099] As examples of some optional parameters, the tab is selected from any one of copper, aluminum, nickel, stainless steel, nickel-cobalt alloy, zinc, nickel-cadmium alloy, and copper-nickel alloy.

[0100] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application and do not represent all possible embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0101] The chemical raw materials involved in the following examples and comparative examples are all prior art and are commercially available. The experimental devices, test devices, etc. involved in the following examples and comparative examples are all conventional devices in the art, without special requirements and limitations.

[0102] Example 1

[0103] First, the positive electrode sheet, the negative electrode sheet and the diaphragm are stacked, wherein the number of electrode sheet composite aluminum foil layers is 5, the thickness of the electrode sheet composite aluminum foil is 12 μm, and the thickness of the non-metallic layer of the electrode sheet composite aluminum foil is 10 μm. Subsequently, an additional layer of composite aluminum foil with a thickness of 12 μm and a layer of 80 μm pre-welded aluminum sheet are placed outside the first and last layers of the stacked electrode sheet composite aluminum foil, and pre-welding is performed under the conditions of a welding time of 25 ms, a welding pressure of 0.1 bar, and an amplitude of 20%. After the pre-welding is completed, the additional composite aluminum foil and the pre-welded aluminum sheet are peeled off to obtain a composite aluminum foil joint 2; in order from bottom to top, a main welding aluminum sheet 3 with a thickness of 80 μm, a composite aluminum foil joint 2, and a pole ear to be welded with a thickness of 80 μm are stacked together, and welded for 77 ms at a pressure of 0.2 bar and an amplitude of 11% to obtain a pole ear battery cell.

[0104] Embodiment 2-9

[0105] The preparation process and method are the same as those in Example 1, except that the welding time, welding pressure, amplitude, thickness of the main welding aluminum sheet, thickness of the pole piece composite aluminum foil, number of layers, and thickness of the non-metallic layer are different.

[0106] Example 10

[0107] The battery cell prepared in Example 1 was packaged, injected and formed to prepare a small soft-pack battery.

[0108] Comparative Examples 1-7

[0109] The preparation process and method are the same as those in Example 1, except that the welding time, welding pressure, amplitude, thickness of the main welding aluminum sheet, thickness of the pole piece composite aluminum foil, number of layers, and thickness of the non-metallic layer are different.

[0110] Comparative Example 8

[0111] The battery cell prepared in Comparative Example 8 was packaged, injected and formed to prepare a small soft-pack battery.

[0112] The specific parameters of Examples 1-9 and Comparative Examples 1-7 are shown in Table 1.

[0113] Test Method

[0114] Welding strength: Fix the two ends of the weld on the two end clamps of the tensile testing machine respectively, stretch the sample at a speed of 50mm / min until the weld breaks, and read the peak tensile force.

[0115] Residual area: After completing the welding strength test, the area containing residual aluminum foil on the tab accounts for the proportion of the total area of ​​the weld.

[0116] Among them, a welding strength greater than 20N / 10mm is considered to meet the welding strength standard, and a residual area ≥95% is considered to meet the residual area standard.

[0117] Yield rate = (single process output quantity / preparation quantity)*100%.

[0118] The test results of Examples 1-9 and Comparative Examples 1-7 are shown in Table 2.

[0119] The test results of Example 10 and Comparative Example 8 are shown in Table 3.

[0120] Table 1

[0121]

[0122]

[0123]

[0124] Table 2

[0125] Serial number M Welding strength (N / 10mm) Residual area (%) Example 1 0.75 22.8 100 Example 2 -0.75 22.1 100 Example 3 -0.04 23.6 100 Example 4 -0.43 23.8 100 Example 5 0.81 23 100 Example 6 -0.03 22.5 100 Example 7 -0.03 22.4 100 Example 8 0.8 21.6 100 Example 9 -0.24 21.3 100 Comparative Example 1 2.2 20.2 50 Comparative Example 2 1.48 21 66 Comparative Example 3 1.43 20.9 75 Comparative Example 4 -3.98 15.8 100 Comparative Example 5 2.04 21.1 66 Comparative Example 6 -2.46 16.7 100 Comparative Example 7 -1.76 18.4 100

[0126] As shown in Table 2, the welding strength and residual area of ​​Examples 1-9 all meet the process standards. In contrast, Comparative Examples 1-7 show unstable welding effects, which indicates that according to M=6.3084ln(a)+2520.57

[0127] b 4.6551 +6.2613c-1.7338*10 -4 d 2 +0.09525d-30.262-0.1075L(0.65T+0.15P), -1≤M≤1 The selected parameters can effectively realize the welding between the pole ear to be welded, and the welding strength and residual area can meet the requirements of the process standards.

[0128] It can be observed from Examples 1-9 and Comparative Examples 1-3 and 5 that although the welding strength of Comparative Examples 1-3 and 5 can be higher than 20N / 10mm, the residual area cannot meet the process requirements. At the same time, it can be observed from Table 2 that M in Comparative Examples 1-3 and 5 is greater than 1. This may be because when the selected main welding pressure, main welding time, main welding amplitude, main welding aluminum sheet thickness are combined with the number of electrode composite aluminum foil layers, the thickness of the electrode composite aluminum foil and the thickness of the non-metallic layer of the electrode composite aluminum foil during the main welding so that the obtained M is greater than 1, the welding conditions cannot guarantee the effectiveness of the welding area, resulting in the residual area not meeting the process requirements. In comparative examples 4, 6, and 7, the M values ​​are all less than -1, and the welding strengths are all less than 20N / 10mm. This may be because when M is less than -1 after the selected welding parameters are calculated, although the coverage of the welding area can be guaranteed, the welding strength is weak and cannot meet the process requirements. Therefore, according to embodiments 1-9 and comparative examples 1-7, it is necessary to select the corresponding main welding pressure, main welding time, main welding amplitude, main welding aluminum sheet thickness, the number of electrode composite aluminum foil layers and the electrode composite aluminum foil thickness, and the thickness of the non-metallic layer of the electrode composite aluminum foil during the main welding process so that -1≤M≤1 is satisfied.

[0129] Table 3

[0130] Pre-soldering yield Main welding yield Battery capacity yield Experimental Example 10 100％ 100％ 100％ Comparative Example 8 100％ 73％ 71％

[0131] Example 10 and Comparative Example 8 respectively show the yield rates of batteries prepared by the battery cells welded in Example 1 and the battery cells welded in Comparative Example 1 at different stages. It can be observed that when the battery is prepared by the battery cells prepared in the comparative example, the battery capacity yield rate of Comparative Example 8 is only 71%, which is much lower than that of Example 10. This indicates that the method of welding the composite aluminum foil and the pole tab proposed in this scheme can effectively ensure the welding between the pole piece composite aluminum foil and the pole tab, thereby ensuring the stability of the battery capacity and performance.

[0132] The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. Although the embodiments of the present invention have been shown and described above, it can be understood that the above-described embodiments are exemplary and cannot be understood as limitations of the present invention. Those of ordinary skill in the art can change, modify, replace and deform the above-described embodiments within the scope of the present invention. In addition, those of ordinary skill in the art can combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without contradiction.

Claims

1. A method for welding a pole piece composite aluminum foil to a pole ear, characterized in that: The electrode sheets of the stacked core are pre-welded to weld the electrode sheet composite aluminum foil into a whole to obtain a composite aluminum foil joint (2), and then the composite aluminum foil joint (2) and the electrode tab to be welded are welded by main welding to obtain a tab battery cell. During the main welding process, the main welding pressure, main welding time, main welding amplitude, and main welding aluminum sheet thickness parameters are selected according to the number and thickness of the electrode sheet composite aluminum foil layers and the thickness of the non-metallic layer of the electrode sheet composite aluminum foil so as to satisfy M=6.3084ln(a)+2520.57b. 4.6551 +6.2613c-1.7338*10 -4 d 2 +0.09525d-30.262-0.1075L(0.65T+0.15P), -1≤M≤1, to ensure that the welding strength and residual area meet the process standards, where a is the main welding time, b is the main welding pressure, c is the main welding amplitude, d is the main welding aluminum sheet thickness, L is the number of electrode composite aluminum foil layers, T is the electrode composite aluminum foil thickness, and P is the thickness of the electrode composite aluminum foil non-metallic layer.

2. The method for welding the electrode composite aluminum foil and the electrode tab according to claim 1, characterized in that: The pre-welding step is as follows: firstly, the positive electrode sheet, the negative electrode sheet and the separator are stacked to obtain a battery core, and then an additional layer of composite aluminum foil is placed outside the first layer of composite aluminum foil of the electrode sheet and the last layer of composite aluminum foil of the electrode sheet in the stack, and a layer of pre-welded aluminum sheet is placed outside the additional composite aluminum foil to perform pre-welding. After the pre-welding is completed, the additionally wrapped composite aluminum foil and the pre-welded aluminum sheet are peeled off to obtain a composite aluminum foil joint (2).

3. The method for welding the electrode composite aluminum foil and the electrode tab according to claim 2, characterized in that: The number of composite aluminum foil layers of the electrode of the battery cell is less than 40; The additional composite aluminum foil is selected from 1-3 layers; Preferably, the additional composite aluminum foil is selected from 1 layer; The thickness of the pre-welded aluminum sheet is selected from 50-200 μm; Preferably, the thickness of the pre-welded aluminum sheet is selected from 100-150 μm.

4. The method for welding the electrode composite aluminum foil and the electrode tab according to claim 1, characterized in that: The main welding step is to stack the main welding aluminum sheet (3), the composite aluminum foil joint (2), and the electrode tab (1) to be welded in sequence from bottom to top, and then weld the three to obtain the electrode tab battery cell.

5. The method for welding the electrode composite aluminum foil and the electrode tab according to claim 4, characterized in that: The thickness of the main welding aluminum sheet (3) is equal to that of the electrode tab (1) to be welded; The thickness of the electrode tab 1 to be welded is selected from 30-250 μm; The width of the electrode tab 1 to be welded and the main welding aluminum sheet 3 is greater than that of the composite aluminum foil joint (2).

6. The method for welding the electrode composite aluminum foil and the electrode tab according to claim 4, characterized in that: The main welding head descending speed is selected from 5 to 50 mm / s; The main welding delay time is selected from 0.05 to 0.5 s; The main welding pressure holding time is selected from 0.05 to 1s; The main welding holding pressure is selected from 0.05 to 0.5 bar.

7. A tab battery cell, characterized in that: The pole tab battery cell is obtained by welding the pole piece composite aluminum foil and the pole tab according to any one of claims 1 to 6.

8. The tab battery cell according to claim 7, characterized in that: The tab battery cell comprises a positive electrode sheet, a negative electrode sheet, a separator and a tab; The positive electrode sheet includes a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent; The positive electrode binder may be selected from at least one of thermoplastic resin, acrylic resin, sodium carboxymethyl cellulose and styrene butadiene rubber; The positive electrode conductor includes a crystalline carbon material and an amorphous carbon material.

9. The tab battery cell according to claim 7, characterized in that: The negative electrode sheet includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent; The tab is selected from any one of copper, aluminum, nickel, stainless steel, nickel-cobalt alloy, zinc, nickel-cadmium alloy, and copper-nickel alloy.

10. An energy storage device, characterized in that: The method for welding the electrode composite aluminum foil and the electrode tab as described in any one of claims 1 to 6 is used for welding or the electrode tab battery cell includes the electrode tab battery cell as described in any one of claims 7 to 9.

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