Pole piece and pole lug, pole lug reinforcing structure, composite pole piece, lithium battery and method thereof

Abstract

The invention provides a pole piece tab, a tab reinforcing structure, a composite pole piece, a lithium battery and a method thereof, the pole piece tab comprises at least one composite current collector monomer, and the composite current collector monomer at least comprises an organic support body, a conductive layer and a protective layer; reinforcing layers are arranged on the upper surface and the lower surface of the composite current collector monomer, the reinforcing layers are formed by coating at least one part of the upper surface and the lower surface of the composite current collector monomer with reinforcing materials, and the proportion of the projection of the reinforcing layers on the surface of the composite current collector monomer is within a preset range; the reinforcing material comprises a mixture composed of reinforcing slurry and alloy particles, and the alloy particles account for 5%-80% of the mass of the reinforcing material; wherein the reinforcing slurry is prepared from a first composition and at least one second composition, the viscosity of the reinforcing slurry is 50-10000 cps, and the mass percent of the second composition in the reinforcing slurry is 1%-90%; the enhancement layer is used for welding the connection layer, and the projection of the connection layer on the surface of the composite current collector monomer is within the projection range of the enhancement layer.

Description

Technical Field

[0001] The present disclosure relates to the technical field of lithium batteries, and more specifically, to a pole piece tab, an ear reinforcement structure, a composite pole piece, a lithium battery, and a method thereof. Background Art

[0002] Lithium-ion batteries, as an efficient energy storage device, are widely used in people's daily lives. A lithium-ion battery generally uses a lithium alloy metal oxide as the positive electrode material, graphite as the negative electrode material, a positive and negative electrode separator, and a non-aqueous electrolyte.

[0003] During the production of lithium batteries, metal foils are usually selected as current collectors, where aluminum foil is selected as the positive current collector and copper foil is selected as the negative current collector. To improve the energy density and safety of the battery, in related technologies, a composite current collector obtained by compounding a polymer film and a metal coating can be used to make a lithium battery. However, the middle of the composite current collector uses a polymer film, and the formed insulating layer makes the metal coatings on both sides unable to conduct, so that the traditional welding method is no longer applicable. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a pole piece tab, an ear reinforcement structure, a composite pole piece, a lithium battery, and a method thereof, which can solve the current technical problems of ear welding.

[0005] An embodiment of the present disclosure provides a pole piece tab, including: at least one composite current collector monomer, where the composite current collector monomer includes at least an organic support, a conductive layer, and a protective layer;

[0006] Reinforcement layers are provided on the upper and lower surfaces of the composite current collector monomer, the reinforcement layer is formed by coating a reinforcement material on at least a part of the upper and lower surfaces of the composite current collector monomer, and the proportion of the projection of the reinforcement layer on the surface of the composite current collector monomer is within a preset range;

[0007] The reinforcement material includes a mixture composed of a reinforcement slurry and alloy particles, and the mass percentage of the alloy particles in the reinforcement material is 5% - 80%;

[0008] Wherein, the reinforcement slurry is generated by a first composition and at least one second composition, the viscosity of the reinforcement slurry is 50 - 10000 cps, and the mass percentage of the second composition in the reinforcement slurry is 1% - 90%;

[0009] The reinforcement layer is used for a welding connection layer, and the projection of the connection layer on the surface of the composite current collector monomer is within the projection range of the reinforcement layer.

[0010] In some embodiments, the projected area of the reinforcing layer on the composite current collector monomer is 25%-60% larger than the projected area of the connecting layer on the composite current collector monomer.

[0011] In some embodiments, the projection of the reinforcing layer on the composite current collector monomer overlaps with the surface of the composite current collector monomer.

[0012] In some embodiments, the alloy is selected from at least one of the following: copper alloy, aluminum alloy, nickel alloy.

[0013] In some embodiments, the reinforcing layer makes the internal resistance of the battery cell between 7 mΩ and 15 mΩ.

[0014] In some embodiments, under the condition of the same area of the reinforcing layer, the conductive particulate matter is a copper alloy.

[0015] In some embodiments, the reinforcing layer makes the temperature rise of the charging and discharging battery cell not exceed 40 degrees.

[0016] In some embodiments, when the discharge capacity remains 70%, the reinforcing layer makes the number of cycles of the battery cell greater than 1500 cycles.

[0017] In some embodiments, the first composition is an organic solvent. Preferably, the organic solvent is selected from one of aromatic hydrocarbon organic solvents and N-methylpyrrolidone.

[0018] In some embodiments, the aromatic hydrocarbon organic solvent is selected from at least one of the following: styrene-butadiene rubber solution, phenolic epoxy resin.

[0019] In some embodiments, the second composition is selected from at least one of the following: thermoplastic resin, sodium carboxymethyl cellulose.

[0020] In some embodiments, the thermoplastic resin is selected from at least one of the following: polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, polyamide elastomer, polyamide, polyimide, polymethyl methacrylate.

[0021] In some embodiments, the reinforcing material further includes a curing agent, and the curing agent is selected from at least one of the following: TPO photo-curing agent, AIBN thermal curing agent, and the mass percentage of the curing agent and the conductive material is 0.1% - 1%;

[0022] And / or, the reinforcing material further includes an accelerator, and the accelerator is selected from at least one of the following: polyetheramine, acrylate, and the mass percentage of the accelerator and the conductive material is 0.1% - 1%;

[0023] And / or, the reinforcing material further includes a coupling agent selected from at least one of the following: chromium complex coupling agent, silane coupling agent, titanate coupling agent, and the mass percentage of the coupling agent and the conductive material is 0.1% - 1%.

[0024] An embodiment of the present disclosure provides an ear reinforcing structure, including: n pole piece ears as described in any one of the above and a connecting layer welded to the pole piece ears, where n = 20 - 80.

[0025] An embodiment of the present disclosure provides a composite pole piece, which includes the pole piece ears described in any one of the above claims or the ear reinforcing structure described in claim 14.

[0026] An embodiment of the present disclosure provides a lithium battery, including the composite pole piece as described above.

[0027] An embodiment of the present disclosure provides a preparation method of the pole piece ear as described above, including the following steps:

[0028] Mix the reinforcing slurry and alloy particles to form a reinforcing material;

[0029] Coat the reinforcing material on the surface of the composite current collector monomer.

[0030] An embodiment of the present disclosure provides a preparation method of the ear reinforcing structure as described above, including the following steps:

[0031] Weld the connecting layer to the pole piece ear.

[0032] An embodiment of the present disclosure provides a preparation method of a composite pole piece, including the preparation method of the ear reinforcing structure as described above.

[0033] An embodiment of the present disclosure provides a preparation method of a lithium battery, including the preparation method of the composite pole piece as described above.

[0034] Compared with the prior art, the embodiments of the present disclosure have the following technical effects:

[0035] For the pole piece ear described in the present disclosure, by providing a reinforcing layer outside the composite current collector monomer, the performance of the connecting layer provided on the composite current collector monomer can be improved, such as preventing missed welding and over-welding, thereby improving the electrical conductivity and heat dissipation of the composite current collector stacked layer to form a battery cell, reducing the temperature rise of the 3C charge and discharge battery cell, enabling the lithium battery to maintain good charge and discharge performance, thereby reducing the internal resistance and improving the overall performance of the battery. Description of the Drawings

[0036] The accompanying drawings herein are incorporated into and constitute a part of this specification, showing embodiments consistent with the present disclosure, and are used together with the specification to explain the principles of the present disclosure. Obviously, the accompanying drawings in the following description are only some embodiments of the present disclosure, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts. In the drawings:

[0037] Figure 1 It is a schematic structural diagram of a composite current collector monomer of some embodiments of the present disclosure.

[0038] Figure 2 It is a schematic structural diagram of a pole tab of some embodiments of the present disclosure.

[0039] Figure 3 It is a schematic diagram of the composite layer reinforcement structure of a composite current collector of some embodiments of the present disclosure.

[0040] Figure 4 It is a schematic diagram of the composite layer reinforcement structure of a composite current collector of some other embodiments of the present disclosure.

[0041] Figure 5 It is a schematic diagram of the composite layer reinforcement structure of a composite current collector of some other embodiments of the present disclosure.

[0042] Figure 6 It is a flowchart of a preparation method for a reinforcement structure of some embodiments of the present disclosure.

[0043] Figure 7 It is a schematic diagram of a battery structure of some embodiments of the present disclosure.

[0044] Figure 8 It is a photo of the welding effect of a reinforcement structure pole tab of some embodiments of the present disclosure.

[0045] Figure 9 It is a photo of the welding effect of a pole tab of some comparative examples of the present disclosure. Detailed Description of the Embodiments

[0046] In order to make the objectives, technical solutions, and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present disclosure, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts belong to the scope of protection of the present disclosure.

[0047] The terms used in the embodiments of the present disclosure are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. The singular forms "a", "the" and "said" used in the embodiments of the present disclosure and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. "Plural" generally includes at least two.

[0048] It should be understood that the term "and / or" used herein is only a relationship describing the associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally indicates that the associated objects before and after are in an "or" relationship.

[0049] It should be understood that although terms such as first, second, and third may be used in the embodiments of the present disclosure, these should not be limited to these terms. These terms are only used to make distinctions. For example, without departing from the scope of the embodiments of the present disclosure, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0050] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such commodity or device. Without further limitation, an element defined by the statement "including one" does not exclude the existence of another identical element in the commodity or device including the said element.

[0051] In the related art, a composite current collector obtained by laminating a polymer film and a metal coating is used, and then tab is welded to the composite current collector to fabricate a lithium battery. However, since a polymer film is used in the middle of the composite current collector and the structure is very thin, it is easy to miss welding when welding the tab. Therefore, it is very difficult to obtain a good welding effect for the tab of the electrode sheet with traditional welding methods.

[0052] An embodiment of the present disclosure provides a tab of an electrode sheet, which is characterized by comprising: at least one composite current collector monomer, and the composite current collector monomer at least comprises an organic support body, a conductive layer and a protective layer; reinforcing layers are arranged on the upper and lower surfaces of the composite current collector monomer, and the reinforcing layers are formed by coating a reinforcing material on at least a part of the upper and lower surfaces of the composite current collector monomer, and the proportion of the projection of the reinforcing layer on the surface of the composite current collector monomer is within a preset range; the reinforcing material comprises a mixture composed of a reinforcing slurry and alloy particles, and the mass percentage of the alloy particles in the reinforcing material is 5% to 80%; wherein, the reinforcing slurry is generated from a first composition and at least one second composition, the viscosity of the reinforcing slurry is 50 to 10,000 cps, and the mass percentage of the second composition in the reinforcing slurry is 1% to 90%; the reinforcing layer is used for welding a connection layer, and the projection of the connection layer on the surface of the composite current collector monomer is within the projection range of the reinforcing layer.

[0053] For the tab of the electrode sheet described in the present disclosure, by arranging a reinforcing layer outside the composite current collector monomer, the performance of the connection layer arranged on the composite current collector monomer can be improved, such as preventing missed welding and over-welding from occurring, thereby improving the electrical conductivity and heat dissipation of the composite current collector stacking layer to form an electric core, reducing the temperature rise of the 3C charge and discharge electric core, enabling the lithium battery to maintain good charge and discharge performance, thereby reducing the internal resistance and improving the overall performance of the battery.

[0054] The optional embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0055] The structure of the composite current collector monomer 1 is as Figure 1 shown. A single composite current collector includes an organic support body, such as a polymer layer 10, and a conductive layer 20. The conductive layer 20 is located on at least one side of the polymer layer 10, such as both sides. Optionally, the polymer layer 10 includes a substrate 11 and an adhesive layer 12. The adhesive layer 12 is located on at least one surface of the substrate 11, such as both surfaces, and the adhesive layer 12 is located between the substrate 11 and the conductive layer 20. The adhesive layer 12 is used to enhance the adhesion between the conductive layer 20 and the substrate 11. Of course, the adhesive layer 12 may also be absent. Optionally, the conductive layer 20 includes a primer layer 21 and a conductive particulate layer 22. The primer layer 21 is located on the side of the adhesive layer 12 away from the substrate 11, and the conductive particulate layer 22 is located on the side of the primer layer 21 away from the adhesive layer 12. The primer layer 21 can enhance the adhesion of the conductive particulate layer 22 to the substrate 11. Of course, the conductive particulate layer 22 may also be absent. A protective layer and the like can be arranged outside the conductive layer 20. Referring to the conventional technology, it will not be elaborated herein.

[0056] The material of the organic support is preferably a polymer film. In some embodiments, the material of the organic support includes, but is not limited to, at least one of polyethylene (PE), polypropylene (PP), biaxially oriented polypropylene (BOPP), polyethylene terephthalate (PET), biaxially oriented polyethylene terephthalate (BOPET), polyethylene naphthalate (PEN), poly(p-phenylene terephthalamide) (PPTA), polyimide (PI), polycarbonate (PC), polyetheretherketone (PEEK), polyoxymethylene (POM), polyphenylene sulfide (PPS), polyphenylene ether (PPO), polyvinyl chloride (PVC), polyamide (PA), or polytetrafluoroethylene (PTFE). More preferably, when the composite current collector 10 is used as the positive current collector, the non-conductive substrate 11 is a PET film or a BOPET film; when the composite current collector 10 is used as the negative current collector, the non-conductive substrate 11 is a PP film or a BOPP film. The BOPET film has better tensile strength, heat resistance, transparency, and is less prone to degradation compared to the PET film, and the BOPP film has better tensile strength, heat resistance, transparency, and is less prone to degradation compared to the PP film, which is beneficial to improving the performance of the composite current collector.

[0057] As Figure 2 shown, an embodiment of the present disclosure provides a tab of an electrode sheet, including: at least one composite current collector monomer 1, the composite current collector monomer 1 at least includes an organic support, a conductive layer, and a protective layer; reinforcing layers 3 are provided on the upper and lower surfaces of the composite current collector monomer, the reinforcing layer 3 is formed by coating a reinforcing material on at least a part of the upper and lower surfaces of the composite current collector monomer 1, and the proportion of the projection of the reinforcing layer 3 on the surface of the composite current collector monomer 1 is within a preset range; the reinforcing material includes a mixture composed of a reinforcing slurry and alloy particles, and the mass percentage of the alloy particles in the reinforcing material is 5% - 80%; wherein, the reinforcing slurry is generated by a first composition and at least one second composition, the viscosity of the reinforcing slurry is 50 - 10000 cps, and the mass percentage of the second composition in the reinforcing slurry is 1% - 90%; the reinforcing layer 3 is used to weld the connection layer 4, and the connection layer 4 is, for example, a tab, and the projection area 5 of the connection layer 4 on the surface of the composite current collector monomer 1 is within the projection range of the reinforcing layer 3. As Figures 3 - 5 shown. For the tab of the electrode sheet of the present disclosure, by providing a reinforcing layer outside the composite current collector layer and controlling the coating area of the reinforcing layer, the tab welding performance of the composite current collector can be improved, preventing missed welding and over-welding, and can also improve the conductive performance and heat dissipation performance after welding of the composite layer of the composite current collector, reducing the temperature rise of the 3C charge and discharge battery cell, enabling the lithium battery to maintain good charge and discharge performance, thereby reducing the internal resistance and improving the overall performance of the battery.

[0058] In some embodiments, as Figure 4As shown, the projection of each of the reinforcing layers 3 on each layer of the composite current collector composite layer 100 is 25%-60% larger than the projected area 5 of the connection layer 4 on the surface of the composite current collector composite layer 100, for example, 30% or 50% larger.

[0059] In some embodiments, as Figure 5 shown, the projection of each of the reinforcing layers 3 on each layer of the composite current collector composite layer 100 overlaps with each layer of the composite current collector composite layer 100.

[0060] By increasing the coating area of the reinforcing layer 3 on the surface of each layer of the composite current collector composite layer 100, the performance of the battery cell can be further improved, the internal resistance of welding can be reduced, the heat dissipation performance of the battery can be improved, the battery can be ensured to have a higher number of cycle turns under the condition of reaching the same capacitance, and the service life of the battery can be extended.

[0061] The reinforcing slurry includes at least one first composition, such as an organic solvent, and at least one second composition, such as a solute. The particulate conductive particulate material includes at least one of a metal material, a metal alloy material, and a conductive polymer material. When the particulate conductive particulate material is a metal material, the diameter of the conductive particulate is 1 μm - 50 μm. For a pure metal material with a diameter less than 1 μm, there is no obvious improvement in performance such as welding internal resistance, direct tensile force, battery cell internal resistance, and number of cycle turns. However, the price of a pure metal material with a diameter less than 1 μm is relatively high. Therefore, a pure metal material with a diameter greater than 1 μm is usually selected. For a pure metal material with a diameter of 50 μm - 200 μm, the welding internal resistance and battery cell internal resistance increase significantly. Although the cost decreases slightly and is within an acceptable range, pure metal particles with a particle size less than 50 μm can be preferably selected. When the particulate conductive particulate material is a metal alloy material, the diameter of the conductive particulate is 10 μm - 100 μm. Because it has been found through experiments that the performance differences such as welding internal resistance, direct tensile force, battery cell internal resistance, and number of cycle turns of a metal alloy material with a conductive particulate diameter of 1 μm - 100 μm are not significant and are all excellent. Therefore, a metal alloy material with a diameter of 10 μm - 100 μm can be selected considering the cost. When the particulate conductive particulate material is a conductive polymer material, the diameter of the conductive particulate is 1 μm - 10 μm. It has been found through experiments that the performance parameters such as welding internal resistance, direct tensile force, battery cell internal resistance, and number of cycles of a conductive polymer material are greatly related to the particle size. As the particle size increases, each performance parameter gradually deteriorates. Since the price of the conductive polymer material is relatively low, the cost increase caused by the particle size can be ignored, and it is ideal to select a particle size of 1 μm - 10 μm with smaller particle size for application considering the performance parameters.

[0062] In some embodiments, the organic solvent for forming the reinforcing layer 3 may be selected from one of aromatic hydrocarbon organic solvents and N-methylpyrrolidone. The aromatic hydrocarbon organic solvent is selected from at least one of the following: styrene-butadiene rubber solution, phenolic epoxy resin. Optionally, using the aromatic hydrocarbon organic solvent among the organic solvents listed above, such as at least one of styrene-butadiene rubber solution and phenolic epoxy resin, is environmentally friendly and makes the conductive particulate matter disperse more uniformly in the reinforcing slurry after adding the particulate conductive particulate matter, and the viscosity of the formed reinforcing slurry is more suitable for coating, so that the coated reinforcing layer is more uniform.

[0063] In some embodiments, the solute is selected from at least one of the following: thermoplastic resin, sodium carboxymethyl cellulose. The thermoplastic resin is selected from at least one of the following: polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, polyamide elastomer, polyamide, polyimide. Optionally, using the environmentally friendly thermoplastic resin among the solutes listed above, such as at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, polyamide elastomer, polyamide, and polyimide, can reasonably control the viscosity of the reinforcing slurry, is environmentally friendly, and makes the conductive particulate matter more easily diffuse in the reinforcing slurry to form a uniform reinforcing slurry after adding the particulate conductive particulate matter, so that the coated reinforcing layer is more uniform.

[0064] In some embodiments, the metal material is selected from at least one of the following: Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn. Optionally, selecting pure metal powders of Cu, Al, Ni, Au, Ag, Ti, Gr, Mg, and Mo is easier to weld in the experiment, and the welding effect is good. Especially Cu and Al have the advantages of low price, low welding internal resistance, high direct tensile force, low internal resistance of the battery cell, and a relatively high number of cycles with a discharge capacity retention of 70%.

[0065] In some embodiments, the metal alloy material is selected from at least one of the following: copper alloy, aluminum alloy, nickel alloy, titanium alloy, cobalt alloy. In the experiment, the above several alloys are easier to weld and the welding effect is good. Especially copper alloys, such as silver-coated copper, have the advantages of low price, not easy to oxidize, low welding internal resistance, high direct tensile force, low internal resistance of the battery cell, and a relatively high number of cycles with a discharge capacity retention of 70%.

[0066] In some embodiments, the conductive polymer material is selected from at least one of the following: polypyrrole, polyaniline, polythiophene, carbon nanotubes, graphene, polyacetylene, and polyphenylacetylene. In experiments, the welding effect of the above several conductive polymer materials is relatively good, and they have the advantages of low price, not easy to oxidize, low welding internal resistance, high direct tensile strength, low internal resistance of the battery cell, etc. At the same time, they can improve the heat dissipation effect of the battery cell. Compared with the case where no reinforcement layer is provided, the temperature rise of the battery cell is significantly reduced, which is beneficial to improving the cycle life and service life of the battery cell.

[0067] In some embodiments, the reinforcing paste further includes a curing agent, and the curing agent is selected from at least one of the following: TPO (epoxy resin) photo-curing agent, AIBN (azobisisobutyronitrile) thermal-curing agent. Optionally, the mass percentage of the curing agent and the conductive material is 0.1% - 1%. By selecting the photo-curing agent, curing can be carried out under light irradiation, avoiding the influence of heating on the stability of each film layer. By selecting the thermal-curing agent, rapid curing can be achieved by heating in the case where light irradiation is not convenient.

[0068] In some embodiments, the reinforcing paste further includes a promoter, and the promoter is selected from at least one of the following: polyetheramine, acrylate. The polyetheramine promoter uses EP-184, and the acrylate promoter uses tetramethylthiourea. Optionally, the mass percentage of the promoter and the conductive material is 0.1% - 1%. By adding the above-mentioned promoter, the reaction rate of the reinforcing paste can be accelerated, the mixing efficiency of the solvent and the solute can be improved, and a stable reinforcing paste can be quickly formed.

[0069] In some embodiments, the reinforcing paste further includes a coupling agent, and the coupling agent is selected from at least one of the following: chromium complex coupling agent, silane coupling agent, titanate coupling agent. Optionally, the mass percentage of the coupling agent and the conductive material is 0.1% - 1%. The selection of the above coupling agent can enhance the binding force between the solvent and the solute, enhance the stability of the reinforcing paste and the direct tensile strength of welding, and easily form a stable reinforcing structure.

[0070] As Figures 3 - 5As shown in the figure, an embodiment of the present disclosure provides a composite current collector stack reinforcement structure, including: a multi-layered composite current collector stack 100, the composite current collector stack is formed by stacking n composite current collector monomers, where n is a natural number from 20 to 60, such as 50 or 55 layers. The n composite current collector monomers can be isolated from each other by a spacer layer 6 to form a composite current collector stack. The spacer layer 6 has the functions of insulation and bonding; on one side of the outside of the composite current collector stack, there is a connection layer setting area 5, or connection layer setting areas 5 can be provided on both sides. The connection layer setting area 5 is the position where the connection layer 4 is set on the surface of the composite current collector stack 100, such as the position for welding the connection layer 4, or the position for vapor depositing the connection layer 4, or the position for bonding the connection layer 4; a reinforcement layer 3, provided on the side of the composite current collector stack 100 having the connection layer setting area 5, and its projection on the composite current collector stack 100 at least completely covers the connection layer setting area 5. The reinforcement layer 3 is formed by coating a reinforcement material on the side of the composite current collector stack 100 having the connection layer setting area 5. The reinforcement material includes a mixture of a reinforcement slurry and alloy particles. The connection layer 4 is provided on the connection layer setting area 5 through the reinforcement layer 3. The connection layer 4 is provided on at least one side of the reinforcement layer 3 away from the composite current collector stack 100. The projection of the connection layer 4 on the composite current collector stack 100 is partially within the projection range of the reinforcement layer 3 and partially outside the projection range of the composite current collector stack 100. The connection layer 4 can be a connection layer with a metal conductive function, such as a tab, a gold finger, or a conductive joint, etc.

[0071] By providing a reinforcement layer outside the multi-layered composite current collector layer and then providing a connection layer on the reinforcement layer, the connection layer setting performance of the multi-layered composite current collector layer can be improved, such as preventing missed welding and over-welding from occurring, improving the welding success rate of the connection layer. The setting of the reinforcement layer can also improve the conductive performance and heat dissipation of the composite layer battery cell of the composite current collector stack, reduce the temperature rise of the 3C charge and discharge battery cell, keep the lithium battery in good charge and discharge performance, thereby reducing the internal resistance and improving the overall performance of the battery.

[0072] In some embodiments, such as Figure 4As shown, the projection of the reinforcing layer 3 on the composite current collector stack layer 100 is 30%-60% larger in area than the projection of the connection layer 4 on the composite current collector stack layer 100. That is to say, the reinforcing layer 3 at least partially covers the outer surface of the composite current collector stack layer 100. The projection of the connection layer 4 on the composite current collector stack layer 100 is the part where the connection layer 4 overlaps with the composite current collector stack layer 100. In some embodiments, the projection of the connection layer 4 on the composite current collector stack layer 100 is the connection layer setting area 5. A part of the connection layer 4 extends out of the side of the composite current collector stack layer 100 for connection with an external electrode or other conductive parts.

[0073] In some embodiments, as Figure 3 shown, the projection of the reinforcing layer 3 on the composite current collector stack layer 100 overlaps with the composite current collector stack layer 100.

[0074] By changing the coverage area of the reinforcing layer 3 on the surface of the composite current collector stack layer 100, the performance of the battery cell can be further improved, the welding internal resistance can be reduced, the heat dissipation performance of the battery can be improved, the battery can be ensured to have a higher number of cycle times when reaching the same capacitance, and the service life of the battery can be extended.

[0075] The multi-layer stacked composite current collector stack layer 100 is formed by stacking single-layer composite current collector monomer layers 1, 2, ……, n-1, n. Generally, n is taken as 20-60, such as 55 layers. That is, after stacking 20-60 single-layer composite current collector monomer layers to form the multi-layer stacked composite current collector stack layer 100, a battery is manufactured. An intermediate layer 6 can be added between the composite current collector monomer layers. In the related art, it is very difficult to directly weld the tab on the multi-layer stacked composite current collector stack layer 100, and it is easy to weld through the multi-layer stacked composite current collector stack layer 100. However, in this application, by coating the reinforcing layer 3 in the connection layer setting area and then welding the connection layer 4, the welding success rate is greatly improved, and the welding effect is obvious, as Figures 6 - 7 shown, and the resistance of the battery cell is also significantly reduced, having extremely high application value.

[0076] Among them, the single-layer composite current collector monomer layer 1, the composite current collector monomer layer 2, the composite current collector monomer layer n-1, and the composite current collector monomer layer n can be composite current collector monomer layers with the same or different structures. For example, each single-layer composite current collector monomer layer is as Figure 1 shown.

[0077] In the present disclosure, an enhanced layer is coated on the area of the connection layer outside the multi-layer stacked composite current collector layer. The enhanced layer is formed by an enhanced slurry and alloy conductive particles with a diameter of 0.1 micrometer to 200 micrometers. Then, the connection layer is welded on the enhanced layer, making the composite current collector stacking layer easier to weld the connection layer, improving the welding qualification rate of the battery cell, increasing the conductivity, and reducing the internal resistance of the battery.

[0078] An embodiment of the present disclosure further provides a composite electrode sheet, which includes the composite current collector tab welding structure described in any one of the above. Other structures of the composite electrode sheet are not elaborated herein and can refer to related technologies.

[0079] An embodiment of the present disclosure provides a lithium battery, which includes the composite electrode sheet described above. Other structures of the lithium battery are not elaborated herein and can refer to related technologies.

[0080] The present disclosure also provides a preparation method of the electrode tab as described above, as Figure 6 shown, including the following steps:

[0081] Step S61: Mix the enhanced slurry and alloy particles to form an enhanced material;

[0082] Step S63: Coat the enhanced material on the surface of the composite current collector.

[0083] The present disclosure also provides a preparation method of the enhanced structure of the composite current collector layer tab as described above, including the following step: Weld the metal tab to the electrode tab.

[0084] An embodiment of the present disclosure further provides a composite electrode sheet, which includes the electrode tab described in any one of the above, or the electrode tab prepared by the preparation method of the electrode tab as described above, or the enhanced structure of the composite current collector layer tab as described above, or the enhanced structure of the composite current collector layer tab prepared by the preparation method of the enhanced structure of the composite current collector layer tab as described above.

[0085] An embodiment of the present disclosure further provides a preparation method of a composite electrode sheet, including the preparation method of the electrode tab as described above.

[0086] An embodiment of the present disclosure provides a lithium battery, with a structure as Figure 7 shown, including a negative current collector 200 made of the composite electrode sheet described above, a negative active material 210 is arranged inside the negative current collector 200, and also includes a positive current collector 300 made of the composite electrode sheet described above, a positive active material 310 is arranged inside the positive current collector 300, and also includes a separator 400, which is arranged between the negative current collector 200 and the positive current collector 300. Other structures of the lithium battery are not elaborated herein and can refer to related technologies.

[0087] An embodiment of the present disclosure provides a method for preparing a lithium battery, including the method for preparing the composite electrode sheet as described above.

[0088] The following introduces the composite current collector welding structure, its preparation process and test data through specific examples:

[0089] Example 1: A composite current collector reinforcement structure includes a composite current collector layer, a reinforcement layer, and a metal tab. The composite current collector layer includes a plurality of stacked copper composite current collectors (as Figure 3 shown); the reinforcement layer is coated on each layer of the composite current collector, and the metal tab is welded to the composite current collector layer through the reinforcement layer;

[0090] The reinforcing material includes reinforcing slurry and alloy particles, and the mass percentage of the alloy particles in the reinforcing material is 5%. The conductive material is Cu alloy metal powder. The reinforcing slurry is composed of styrene-butadiene rubber solution and polyvinylidene fluoride. The viscosity of the reinforcing slurry is 500 cps, and the mass percentage of the styrene-butadiene rubber solution and polyvinylidene fluoride is 5%.

[0091] Stack 55 layers of copper composite current collectors 1 as Figure 1 shown to form a copper composite current collector layer 100;

[0092] First add the styrene-butadiene rubber solution and polyvinylidene fluoride, stir evenly, then add the Cu alloy metal powder, stir evenly, and uniformly coat the surface of the composite current collector to form a reinforcement layer;

[0093] Weld a metal tab on the reinforcement layer to obtain a composite current collector reinforcement structure, as Figure 3 shown.

[0094] The coating area is 30% larger than the projected area of the tab welding layer;

[0095] Example 2: Example 2 is the same as Example 1, except that:

[0096] The composite current collector is a 55-layer aluminum composite current collector;

[0097] The reinforcing material includes reinforcing slurry and alloy material, and the mass percentage of the alloy material in the reinforcing material is 50%. The conductive material is Cu alloy metal powder. The reinforcing slurry is composed of phenolic epoxy resin and polyvinyl alcohol. The viscosity of the reinforcing slurry is 20000 cps, and the mass percentage of the phenolic epoxy resin and polyvinyl alcohol is 90%. It is uniformly coated on the upper surface of the composite layer of the composite current collector, and the coating area of the reinforcement layer is 50% larger than the projected area of the tab welding layer;

[0098] Example 3: Example 3 is the same as Example 1, except that: the copper composite current collector 1 is 20 layers;

[0099] Example 4: Example 4 is the same as Example 1, except that: the aluminum composite current collector 1 has 80 layers;

[0100] Example 5: Example 5 is the same as Example 1, except that:

[0101] The mass percentage of the alloy material in the reinforcing material is 50%, the conductive material is a Cu alloy metal powder polymer, the reinforcing slurry is composed of N-methylpyrrolidone and polytetrafluoroethylene, and the viscosity of the reinforcing slurry is 5000 cps.

[0102] After stirring evenly, it is evenly coated on the upper surface of the composite layer of the composite current collector, and the coating area is the entire sheet coating;

[0103] Example 6: Example 6 is the same as Example 5, except that: the conductive material is an Al alloy metal powder; after stirring evenly, it is evenly coated on the entire upper surface of the composite layer of the composite current collector, and the coating area of the reinforcing layer is 30% larger than the projected area of the tab welding layer;

[0104] Example 7: Example 7 is the same as Example 5, except that: the conductive material is an Al alloy metal powder; after stirring evenly, it is evenly coated on the entire upper surface of the composite layer of the composite current collector, and the coating area of the reinforcing layer is 50% larger than the projected area of the tab welding layer;

[0105] Example 8: Example 8 is the same as Example 5, except that: the conductive material is an Al alloy metal powder; after stirring evenly, it is evenly coated on the entire upper surface of the composite layer of the composite current collector;

[0106] Example 9: Example 9 is the same as Example 5, except that: the conductive material is a Ni alloy metal powder; after stirring evenly, it is evenly coated on the entire upper surface of the composite layer of the composite current collector, and the coating area of the reinforcing layer is 30% larger than the projected area of the tab welding layer;

[0107] Example 10: Example 10 is the same as Example 5, except that: the conductive material is a Ni alloy metal powder; after stirring evenly, it is evenly coated on the entire upper surface of the composite layer of the composite current collector, and the coating area of the reinforcing layer is 50% larger than the projected area of the tab welding layer;

[0108] Example 11: Example 11 is the same as Example 5, except that: the conductive material is a Ni alloy metal powder; after stirring evenly, it is evenly coated on the entire upper surface of the composite layer of the composite current collector;

[0109] Example 12:

[0110] Example 12 is the same as Example 5, except that: the adhesive layer further adds a polyolefin (TPO) photo-curing agent, and the mass percentage of the curing agent and the conductive material is 0.1%.

[0111] Example 13:

[0112] Example 13 is the same as Example 5, except that: the adhesive layer further adds an azodiisobutyronitrile (AIBN) thermal curing agent, and the mass percentage of the curing agent and the conductive material is 1%.

[0113] The glue solution is composed of phenolic epoxy resin and sodium carboxymethyl cellulose, and the viscosity of the glue solution is 15000 cps.

[0114] Example 14:

[0115] Example 14 is the same as Example 5, except that: the adhesive layer further adds polyetheramine, and the mass percentage of the polyetheramine and the conductive material is 0.1%.

[0116] Example 15:

[0117] Example 15 is the same as Example 5, except that: the adhesive layer further adds acrylate, and the mass percentage of the acrylate and the conductive material is 1%.

[0118] Example 16:

[0119] Example 16 is the same as Example 5, except that: the adhesive layer further adds a chromium complex coupling agent, and the mass percentage of the chromium complex coupling agent and the conductive material is 0.1%.

[0120] Example 17:

[0121] Example 17 is the same as Example 5, except that: the adhesive layer further adds a silane coupling agent, and the mass percentage of the silane coupling agent and the conductive material is 1%.

[0122] Comparative example: Without coating any substance, directly weld the tab on the surface of the multi-layer composite current collector.

[0123] Table 1 Comparison of the welding performance of the connection layer of the composite current collector stack

[0124]

[0125] The above Examples 1-17 and Comparative Examples were tested, and the test performance comparison results in Table 1 could be obtained. Among them, in Examples 1-11, the components of the two compositions forming the enhanced slurry were the same, that is, the formed enhanced slurry was the same, mainly formed by an environmentally friendly aromatic hydrocarbon organic solvent and an environmentally friendly thermoplastic resin. The difference was that different types of conductive particulate matter were added respectively. Among them, in Examples 1-5, Cu alloy metal powder materials were added, but the coating areas of the enhanced layer were different, covering the tab welding layer, exceeding the projection area of the tab welding layer by 30%, exceeding the projection area of the tab welding layer by 50%, and completely covering the composite layer of the composite current collector. In Examples 6-8, Al alloy metal powder materials were added, but the coating areas of the enhanced layer were different, covering the tab welding layer, exceeding the projection area of the tab welding layer by 30%, exceeding the projection area of the tab welding layer by 50%, and completely covering the composite layer of the composite current collector. In Examples 9-11, Ni alloy metal materials were added, but the coating areas of the enhanced layer were different, exceeding the projection area of the tab welding layer by 30%, exceeding the projection area of the tab welding layer by 50%, and covering the composite layer of the composite current collector. In Examples 13-17, different proportions of curing agents or coupling agents were added. The following analysis conclusions could be drawn from the welding effect and electrical performance test results in Table 1.

[0126] For the welding internal resistance, the welding internal resistances of the Cu alloy metal materials in Examples 1-5 were roughly equivalent within the coating areas, but the larger the covering area, the smaller the welding internal resistance. It can be seen that increasing the coating area of the enhanced layer can reduce the welding internal resistance; the welding internal resistances of the Al alloy metal materials in Examples 6-8 were roughly equivalent within the coating areas, but the larger the covering area, the smaller the welding internal resistance. It can be seen that increasing the coating area of the enhanced layer can reduce the welding internal resistance; the welding internal resistances of the Ni alloy metal materials in Examples 9-11 were roughly equivalent within the coating areas, but the larger the covering area, the smaller the welding internal resistance. It can be seen that increasing the coating area of the enhanced layer can reduce the welding internal resistance. Comparing Examples 1-11, it can be shown that under the condition of the same coating area, the welding internal resistance of the Cu alloy metal powder was the smallest, and the welding internal resistance of the Ni alloy metal powder was the largest. Therefore, the Cu alloy metal powder material had a greater advantage in terms of welding internal resistance. At the same time, the welding internal resistances of Examples 1-11 were much smaller than 470 of the Comparative Example, with an obvious difference. Adding different proportions of curing agents or coupling agents in Examples 12-17 would reduce the welding internal resistance and play a certain role in improving the welding internal resistance.

[0127] For the direct tensile force, the Cu alloy metal powder materials of Examples 1-5 have roughly equivalent direct tensile forces within the coated areas. However, the larger the coverage area, the greater the direct tensile force. Evidently, increasing the coating area of the reinforcement layer can enhance the direct tensile force of the composite layer of the composite current collector and increase the tensile strength. The Al alloy metal powder materials of Examples 6-8 have roughly equivalent direct tensile forces within the coated areas. However, the larger the coverage area, the greater the direct tensile force. Evidently, increasing the coating area of the reinforcement layer can enhance the direct tensile force of the composite layer of the composite current collector and increase the tensile strength. The direct tensile force of the Al alloy metal is less than that of the Cu alloy metal within each coated area. The Ni alloy metals of Examples 9-11 have roughly equivalent direct tensile forces within the coated areas. However, the larger the coverage area, the greater the direct tensile force. Evidently, increasing the coating area of the reinforcement layer can enhance the direct tensile force of the composite layer of the composite current collector and increase the tensile strength. The direct tensile force of the Ni alloy metal is greater than that of the Cu alloy metal material and the Al alloy metal material. Meanwhile, the direct tensile forces of Examples 1-11 are much greater than that of the comparative example, which is 5.3, showing a significant difference. Adding different proportions of curing agents or coupling agents in Examples 12-17 will increase the welding direct tensile force and play a certain role in improving the direct tensile force.

[0128] For the temperature rise of 3C charge and discharge battery cells, with the increase in the coating area of the Cu alloy metal materials of Examples 1-5, the temperature rise decreases significantly. Starting from 25°C, it rises to 52°C, 45°C, and 40°C respectively, with a maximum increase of 27°C and a minimum increase of 15°C. Evidently, the area of the coated region has a significant impact on the temperature rise of the battery. In the case of full coverage, the temperature only rises by 15°C. For the Al alloy metal powder materials of Examples 6-8, with the increase in the coating area, the temperature rise also decreases significantly. Starting from 25°C, it rises to 55°C, 52°C, and 45°C respectively, with a maximum increase of 30°C and a minimum increase of 20°C, slightly higher than that of the Cu alloy metal materials of Examples 1-5. For the Ni alloy metal materials of Examples 9-11, with the increase in the coating area, the temperature rise also decreases significantly. Starting from 25°C, it rises to 62°C, 56°C, and 50°C respectively, with a maximum increase of 37°C and a minimum increase of 25°C. Evidently, the area of the coated region has a significant impact on the temperature rise of the battery. Among the three types of polymer conductive particles, the Cu alloy metal material has the most ideal control over the temperature rise. In the lowest Example 5, it only rises by 15°C and reaches 40°C. The temperature rises of Examples 1-11 for 3C charge and discharge battery cells are much less than 80°C of the comparative example, showing a significant difference. Adding different proportions of curing agents or coupling agents in Examples 12-17 will reduce the temperature rise and play a certain role in improving the temperature rise.

[0129] Regarding the cycle number / discharge capacity retention of 70%, it refers to the cycle number when the discharge capacity retention is 70%. The cycle numbers of the Cu alloy metal materials in Examples 1-5 are generally high, all greater than 1700 cycles, showing a significant difference compared to the cycle number of Comparative Example 367. The cycle numbers of the Al alloy metal materials in Examples 6-8 are also generally high, reaching more than 1600 cycles, slightly lower than those of the Cu alloy metal materials, and showing a significant difference compared to the cycle number of Comparative Example 367. The cycle numbers of the Ni alloy metal materials in Examples 9-11 decrease slightly, but are all greater than 1500 cycles, showing a significant difference compared to the cycle number of Comparative Example 367. Among Examples 1-11, the Cu alloy metal materials have the highest cycle number because they have better temperature control. Adding different proportions of curing agents or coupling agents in Examples 12-17 will increase the cycle number and play a certain role in improving the cycle number of the battery cell.

[0130] In summary, for the Cu alloy metal material with the coating area completely covering the composite layer of the composite current collector, it has better welding internal resistance and direct tensile force, a cycle number / discharge capacity retention of 70%, and outstanding performance in controlling the temperature rise of 3C charge-discharge battery cells.

[0131] Figure 8 The following are the welding effect photos of the tab welding structure of some embodiments of the present disclosure. There is no welding leakage at the welding position 600. Figure 9 The following are the tab welding effect photos of the above-mentioned comparative example. The welding leakage area 700 is very obvious. It can be seen that the welding effect using the tab welding structure of the present application is good, without welding leakage, while Figure 9 the welding has obvious welding leakage marks.

[0132] Finally, it should be noted that the embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other.

[0133] The above embodiments are only used to illustrate the technical solutions of the present disclosure, not to limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A tab of an electrode sheet, characterized in that Comprising: At least one composite current collector monomer, said composite current collector monomer comprising at least an organic support, a conductive layer and a protective layer; Reinforcing layers are provided on the upper and lower surfaces of the composite current collector monomer, the reinforcing layers are formed by coating a reinforcing material on at least a part of the upper and lower surfaces of the composite current collector monomer, and the proportion of the projection of the reinforcing layer on the surface of the composite current collector monomer is within a preset range; The reinforcing material comprises a mixture composed of a reinforcing slurry and alloy particles, and the mass percentage of the alloy particles in the reinforcing material is 5% - 80%; Wherein, the reinforcing slurry is generated from a first composition and at least one second composition, the viscosity of the reinforcing slurry is 50 - 10000 cps, and the mass percentage of the second composition in the reinforcing slurry is 1% - 90%; The reinforcing layer is used for welding a connection layer, and the projection of the connection layer on the surface of the composite current collector monomer is within the projection range of the reinforcing layer.

2. The tab of the electrode tab according to claim 1, wherein, The projection of the reinforcing layer on the composite current collector monomer is 25% - 60% larger in area than the projection of the connection layer on the composite current collector monomer.

3. The tab of the electrode sheet according to claim 1, wherein, The projection of the reinforcing layer on the composite current collector monomer overlaps with the surface of the composite current collector monomer.

4. An ear tab reinforcement structure, characterized in that, Comprising: n pole piece tabs and connection layers according to any one of claims 1 - 3, the connection layer is welded to the pole piece tabs, where n = 20 - 80.

5. A composite electrode, characterized in that, The composite pole piece comprises the pole piece tab according to any one of claims 1 - 3, or the tab reinforcing structure according to claim 4.

6. A lithium battery, characterized in that, Comprising the composite pole piece according to claim 5.

7. A method for preparing a tab of a pole piece as described in claims 1-3, characterized in that, Comprising the following steps: Mixing the reinforcing slurry and alloy particles to form a reinforcing material; Coating the reinforcing material on the surface of the composite current collector monomer.

8. A method for preparing the tab reinforcing structure according to claim 4, characterized in that, Comprising the following steps: Welding the connection layer to the pole piece tab.

9. A preparation method of a composite electrode, characterized in that, Comprising the preparation method of the tab reinforcing structure according to claim 8.

10. A method for preparing a lithium battery, characterized in that, Comprising the preparation method of the composite pole piece according to claim 9.

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