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

Abstract

The invention provides a pole piece tab, a tab welding structure, a composite pole piece, a lithium battery and a method thereof, the pole piece tab comprises at least one composite current collector, the composite current collector at least comprises a base material layer and conductive layers arranged on two sides of the base material layer, and a base layer is arranged between the base material layer and the conductive layers; at least one surface of the composite current collector is provided with a coating layer, the coating layer is formed by coating at least one part of the surface of the composite current collector with a coating material, and the proportion of the projection of the coating layer on the surface of the composite current collector is within a preset range; the coating material comprises a mixture composed of coating slurry and a conductive material, the conductive material accounts for 5%-70% of the mass of the coating material, the conductive material comprises a metal particle material, and the particle size of the metal particle material is smaller than 200 micrometers; the coating layer is used for welding a metal tab, and the projection of the metal tab on the surface of the composite current collector is within the projection range of the coating layer.

Description

Technical Field

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

[0002] As an efficient energy storage device, lithium-ion batteries 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. Among them, 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 manufacture a lithium battery. However, since the middle of the composite current collector uses a polymer film, the formed insulating layer makes the metal coatings on both sides unable to conduct, making the traditional welding method no longer applicable. Summary of the Invention

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

[0005] An embodiment of the present disclosure provides a pole piece tab, including: at least one composite current collector, the composite current collector at least includes a substrate layer and conductive layers provided on both sides of the substrate layer, and an underlayer is included between the substrate layer and the conductive layers;

[0006] At least one surface of the composite current collector is provided with a coating layer, the coating layer is formed by coating a coating material on at least a part of the surface of the composite current collector, and the proportion of the projection of the coating layer on the surface of the composite current collector is within a preset range;

[0007] The coating material includes a mixture composed of a coating slurry and a conductive material, the mass percentage of the conductive material in the coating material is 5% - 70%, the conductive material includes metal particulate materials, and the particle size of the metal particulate materials is less than 200 microns;

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

[0009] The coating layer is used for welding a metal tab, and the projection of the metal tab on the surface of the composite current collector is within the projection range of the coating layer.

[0010] In some embodiments, the projection of the coating layer on the surface of the composite current collector is 25%-60% larger in area than the projection of the metal tab on the surface of the composite current collector.

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

[0012] In some embodiments, the metal material is selected from at least one of the following: Cu, Al, Ni.

[0013] In some embodiments, under the condition that the coating layer covers the same area as the tab welding area, the conductive material is selected from the material with the lowest temperature rise of the charge-discharge battery cell.

[0014] In some embodiments, the temperature rise of the charge-discharge battery cell of the conductive material does not exceed 30 degrees.

[0015] In some embodiments, when the discharge capacity is maintained at 70%, the number of cycles of the conductive material is greater than 1300 cycles.

[0016] In some embodiments, the first type of substance is an organic solvent. Preferably, the organic solvent is selected from one of aromatic hydrocarbon organic solvents and N-methylpyrrolidone.

[0017] In some embodiments, the aromatic hydrocarbon organic solvent is selected from at least one of the following: styrene-butadiene rubber solution, phenolic epoxy resin.

[0018] In some embodiments, the second type of substance is selected from at least one of the following: thermoplastic resin, sodium carboxymethyl cellulose.

[0019] 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.

[0020] In some embodiments, the coating 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%;

[0021] And / or, the coating 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%;

[0022] And / or, the coating material 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, and the mass percentage of the coupling agent and the conductive material is 0.1%-1%.

[0023] An embodiment of the present disclosure further provides an ear welding structure, including: n tab ears of the electrode sheets as described in any one of the above and a metal tab ear, wherein the metal tab ear is welded to the tab ear of the electrode sheet, and n = 20 - 80.

[0024] An embodiment of the present disclosure further provides a composite electrode sheet, which includes the tab ear of the electrode sheet as described in any one of the above claims, or the ear welding structure as described above.

[0025] An embodiment of the present disclosure further provides a lithium battery, including the composite electrode sheet as described above.

[0026] An embodiment of the present disclosure further provides a preparation method of the tab ear of the electrode sheet as described above, including the following steps:

[0027] Mix the coating slurry and the conductive material to form a coating material;

[0028] Coat the coating material on the surface of the composite current collector.

[0029] An embodiment of the present disclosure further provides a preparation method of the ear welding structure as described above, including the following steps:

[0030] Weld the metal tab ear to the tab ear of the electrode sheet.

[0031] An embodiment of the present disclosure further provides a preparation method of the composite electrode sheet, including the preparation method of the ear welding structure as described above.

[0032] An embodiment of the present disclosure further provides a preparation method of a lithium battery, including the preparation method of the composite electrode sheet as described above.

[0033] Compared with the prior art, the embodiments of the present disclosure have the following technical effects:

[0034] For the tab ear of the electrode sheet described in the present disclosure, by providing a coating layer on the outer side of the composite current collector so that it at least covers the ear welding area, on the one hand, the ear welding performance of the composite current collector layer can be improved, and on the other hand, the temperature rise of the 3C charge and discharge battery cell can be reduced, enabling the lithium battery to maintain good charge and discharge performance, thereby improving the overall performance of the battery. Description of the Drawings

[0035] The drawings here are incorporated into the description and form a part of this description, showing the embodiments that conform to the present disclosure, and are used together with the description to explain the principles of the present disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0036] Figure 1Schematic structural diagram of a composite current collector according to some embodiments of the present disclosure.

[0037] Figure 2 Schematic structural diagram of a pole piece tab according to some embodiments of the present disclosure.

[0038] Figure 3 Schematic structural diagram of a welding structure of a composite layer of a composite current collector according to some embodiments of the present disclosure.

[0039] Figure 4 Schematic structural diagram of a welding structure of a composite layer of a composite current collector according to some other embodiments of the present disclosure.

[0040] Figure 5 Schematic structural diagram of a welding structure of a composite layer of a composite current collector according to some other embodiments of the present disclosure.

[0041] Figure 6 Flow chart of a method for preparing a welding structure according to some embodiments of the present disclosure.

[0042] Figure 7 Schematic structural diagram of a battery according to some embodiments of the present disclosure.

[0043] Figure 8 Photo of the welding effect of a tab of a welding structure according to some embodiments of the present disclosure.

[0044] Figure 9 Photo of the welding effect of a tab of some comparative examples of the present disclosure. Detailed Description of Specific Embodiments

[0045] 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. Apparently, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of them. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present disclosure.

[0046] The terms used in the embodiments of the present disclosure are only for the purpose of describing specific embodiments, 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.

[0047] It should be understood that the term " / and" used herein is only a description of the associated relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0048] 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.

[0049] 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.

[0050] In the related art, a composite current collector obtained by combining an organic thin film and a metal coating is used, and then a tab is welded to the composite current collector to manufacture a lithium battery. However, since the middle of the composite current collector uses an organic thin film and the structure is very thin, it is easy to have missed welding when welding the tab. Therefore, it is difficult to obtain a tab with good welding effect for traditional welding methods.

[0051] The embodiments of the present disclosure provide a tab for a pole piece, including: at least one composite current collector, the composite current collector at least includes a substrate layer and conductive layers provided on both sides of the substrate layer, and an underlayer is included between the substrate layer and the conductive layers; at least one surface of the composite current collector is provided with a coating layer, the coating layer is formed by coating a coating material on at least a part of the surface of the composite current collector, and the proportion of the projection of the coating layer on the surface of the composite current collector is within a preset range; the coating material includes a mixture composed of a coating slurry and a conductive material, the mass percentage of the conductive material in the coating material is 5% - 70%, the conductive material includes metal particulate materials, and the particle size of the metal particulate materials is less than 200 microns; wherein, the coating slurry is generated by a first type of substance and at least one second type of substance, the viscosity of the coating slurry is 50 - 10000 cps, and the mass percentage of the second type of substance in the coating slurry is 1% - 90%; the coating layer is used for welding a metal tab, and the projection of the metal tab on the surface of the composite current collector is within the projection range of the coating layer.

[0052] For the tab of the pole piece described in the present disclosure, by providing a coating layer on the outside of the composite current collector so that it at least covers the tab welding area, on the one hand, the tab welding performance of the composite current collector layer can be improved, and on the other hand, the temperature rise of the 3C charge and discharge battery cell can be reduced, so that the lithium battery maintains good charge and discharge performance, thereby improving the overall performance of the battery.

[0053] The optional embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0054] The structure of the composite current collector 1 is as Figure 1 shown. A single composite current collector includes a substrate layer, such as 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 sides, 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 an underlayer 21 and a conductive particulate layer 22. The underlayer 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 underlayer 21 away from the adhesive layer 12. The underlayer 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 or the like may be provided outside the conductive layer 20. Referring to conventional techniques, it will not be elaborated here.

[0055] The materials of the substrate include but are 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 a 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 a negative current collector, the substrate is a PP film or a BOPP film. Compared with the PET film, the BOPET film, and compared with the PP film, the BOPP film has better tensile strength, heat resistance, transparency, and is not easily degraded, which is beneficial to improving the performance of the composite current collector.

[0056] As Figure 2As shown in the figure, an embodiment of the present disclosure provides a pole piece tab, including: at least one composite current collector 1, the composite current collector 1 at least includes a base material layer and conductive layers provided on both sides of the base material layer, and an underlayer is included between the base material layer and the conductive layers; at least one surface of the composite current collector 1 is provided with a coating layer 3, for example, one side or both sides of the composite current collector 1 are provided with the coating layer 3, the coating layer 3 is formed by coating a coating material on at least a part of the surface of the composite current collector 1, and the proportion of the projection of the coating layer 3 on the surface of the composite current collector 1 is within a preset range, for example, 10%-100%; the coating material includes a mixture composed of a coating slurry and a conductive material, the mass percentage of the conductive material in the coating material is 5% to 70%, the conductive material includes metal particulate material, and the particle size of the metal particulate material is less than 200 microns; wherein, the coating slurry is generated by a first type of substance and at least one second type of substance, the viscosity of the coating slurry is 50 to 10,000 cps, a viscosity of 50 to 10,000 cps is conducive to forming a uniform coating layer on each composite current collector, and the particulate conductive material can also be evenly dispersed and is not likely to form accumulation, which is convenient for enhancing conductivity, and the mass percentage of the second type of substance in the coating slurry is 1% to 90%; the coating layer 3 is used for welding a metal tab 4, and the projection area 5 of the metal tab 4 on the surface of the composite current collector 1 is within the projection range of the coating layer 3. As Figures 3 - 5 As shown in the figure, for the pole piece tab of the present disclosure, by providing a coating layer on the outside of the composite current collector to make it cover at least the tab welding area, on the one hand, the tab welding performance of the composite current collector layer can be improved, and on the other hand, the temperature rise of the 3C charge and discharge battery cell can be reduced, so that the lithium battery maintains good charge and discharge performance, thereby improving the overall performance of the battery.

[0057] In some embodiments, as Figure 4 shown, the projection of each coating layer 3 on each layer of the composite layer 100 of the composite current collector is 25%-60% larger in area than the projection of the projection area 5 of the metal tab 4 on the surface of the composite layer 100 of the composite current collector, for example, 30% or 50% larger.

[0058] In some embodiments, as Figure 5 shown, the projection of each coating layer 3 on each layer of the composite layer 100 of the composite current collector overlaps with each layer of the composite layer 100 of the composite current collector.

[0059] By increasing the coating area of the coating layer 3 on the surface of each layer of the composite layer 100 of the composite current collector, 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, it is ensured that the battery has a higher number of cycle turns when reaching the same capacitance, and the service life of the battery can be improved.

[0060] The coating material 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 matter includes at least one of a metal material, a metal alloy material, and a conductive polymer material. When the particulate conductive particulate matter is a metal material, the diameter of the conductive particulate matter is 1 micron to 50 microns. For pure metal materials with a diameter less than 1 micron, there is no obvious improvement in performance such as welding internal resistance, direct tensile force, cell internal resistance, and number of cycles. However, the price of pure metal materials with a diameter less than 1 micron is relatively high. Therefore, pure metal materials with a diameter greater than 1 micron are usually selected. For pure metal materials with a diameter of 50 microns to 200 microns, the welding internal resistance and cell internal resistance increase significantly. Although the cost decreases slightly and is within an acceptable range, pure metal particles with a diameter less than 50 microns can be preferably selected. When the particulate conductive particulate matter is a metal alloy material, the diameter of the conductive particulate matter is 10 microns to 100 microns. Because it has been found through experiments that the performance differences in welding internal resistance, direct tensile force, cell internal resistance, and number of cycles of metal alloy materials with a conductive particulate matter diameter of 1 micron to 100 microns are not significant and are all excellent. Therefore, from the perspective of cost, metal alloy materials with a diameter of 10 microns to 100 microns can be selected. When the particulate conductive particulate matter is a conductive polymer material, the diameter of the conductive particulate matter is 1 micron to 10 microns. It has been found through experiments that the performance parameters such as welding internal resistance, direct tensile force, cell internal resistance, and number of cycles of conductive polymer materials have a greater relationship with the particle size. As the particle size increases, each performance parameter gradually deteriorates. Since the price of conductive polymer materials is relatively low, the cost increase caused by the particle size can be ignored, and it is more ideal to select a particle size of 1 micron to 10 microns with smaller particle size from the performance parameters.

[0061] In some embodiments, the organic solvent forming the coating layer 3 can 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 in the above-listed organic solvents, such as at least one of styrene-butadiene rubber solution and phenolic epoxy resin, is beneficial to environmental protection and makes the conductive particulate matter disperse more evenly in the coating material after adding the particulate conductive particulate matter, and the viscosity of the formed coating material is more suitable for coating, making the coated coating layer more uniform.

[0062] 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 an environmentally friendly thermoplastic resin among the solutes listed above, such as at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, polyamide elastomer, polyamide, polyimide, can reasonably control the viscosity of the coating material, is beneficial to environmental protection, and after adding particulate conductive particles, makes the conductive particles more easily dispersed in the coating material to form a uniform coating material, so that the coated coating layer is relatively uniform.

[0063] 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, Mo, in the experiment, the above several pure metal powders are more easily welded, and the welding effect is good. Especially Cu and Al, which have the advantages of low price, low welding internal resistance, high direct tensile force, low internal resistance of the battery cell, and high number of cycles with 70% discharge capacity retention.

[0064] 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 more easily welded, and the welding effect is good. Especially the copper alloy, such as silver-coated copper, has the advantages of low price, not easily oxidized, low welding internal resistance, high direct tensile force, low internal resistance of the battery cell, and high number of cycles with 70% discharge capacity retention.

[0065] In some embodiments, the conductive polymer material is selected from at least one of the following: polypyrrole, polyaniline, polythiophene, carbon nanotubes, graphene, polyacetylene, polyphenylacetylene. In the experiment, the above several conductive polymer materials have relatively good welding effects, have the advantages of low price, not easily oxidized, low welding internal resistance, high direct tensile force, low internal resistance of the battery cell, etc., and at the same time can improve the heat dissipation effect of the battery cell. Compared with not setting a coating layer, the temperature rise of the battery cell is significantly reduced, which is beneficial to improving the number of cycles and service life of the battery cell.

[0066] In some embodiments, the coating material further includes a curing agent, and the curing agent is selected from at least one of the following: TPO (epoxy resin) photocuring 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 photocuring agent, curing can be carried out under light irradiation, avoiding the influence of heating on the stability of each film layer. Selecting the thermal curing agent can achieve rapid curing by heating in cases where light irradiation is not convenient.

[0067] In some embodiments, the coating material further includes an accelerator, and the accelerator is selected from at least one of the following: polyetheramine, acrylate. The polyetheramine accelerator uses EP - 184, and the acrylate accelerator uses tetramethylthiourea. Optionally, the mass percentage of the accelerator and the conductive material is 0.1% - 1%. Adding the above accelerators can accelerate the reaction rate of the coating material, improve the mixing efficiency of the solvent and solute, and quickly form a stable coating material.

[0068] In some embodiments, the coating material 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 agents can enhance the binding force between the solvent and solute, enhance the stability of the coating material and the direct tensile force of welding, and easily form a stable welding structure.

[0069] As Figures 3 - 5 shown, an embodiment of the present disclosure provides an ear welding structure, including: a multi - layer stacked composite current collector stack 100, the composite current collector stack is formed by stacking n layers of composite current collectors, where n is a natural number from 20 to 80, such as 55; a coating layer 3, the coating material is coated on each layer of the composite current collector to form the coating layer 3, and the coating layers 3 on each composite current collector overlap in the projection on the composite current collector stack 100, the coating layer 3 includes a coating material and granular conductive material; a metal tab 4 is welded to the outside of the composite current collector stack 100 through the coating layer 3.

[0070] The multi - layer stacked composite current collector composite layer 100 is formed by stacking single - layer composite current collectors 1, 2, ……, n - 1, n. Generally, n takes 20 - 80, such as 55 layers. That is, after stacking 20 - 80 layers of composite current collectors to form the multi - layer stacked composite current collector composite layer 100 and then manufacturing a battery, in the related art, it is very difficult to directly weld tabs on the multi - layer stacked composite current collector composite layer 100, and it is easy to weld through the multi - layer stacked composite current collector composite layer 100. However, in this application, by coating the coating layer 3 in the projection area of the tab welding layer and then welding the tab welding layer 4, the welding success rate is greatly improved, and the resistance of the battery cell is also significantly reduced, having extremely high application value.

[0071] Among them, the single-layer composite current collectors 1, 2, ..., n-1, and n can be composite current collectors with the same or different structures. For example, each single-layer composite current collector is as shown in Figure 1 .

[0072] For the tab welding structure described in the present disclosure, by coating a coating layer on each layer of the multi-layer stacked composite current collector layer and controlling the area of the coating layer so that it covers at least the projection area of the tab welding layer, on the one hand, the tab welding performance of the multi-layer stacked composite current collector layer can be improved, and on the other hand, the temperature rise of the 3C charge-discharge battery cell can be reduced, enabling the lithium battery to maintain good charge-discharge performance, thereby improving the overall performance of the battery.

[0073] The embodiment of the present disclosure also provides a composite electrode, which includes the composite current collector tab welding structure described in any one of the above. Other structures of the composite electrode will not be elaborated here and can refer to related technologies.

[0074] The embodiment of the present disclosure provides a lithium battery, which includes the composite electrode described above. Other structures of the lithium battery will not be elaborated here and can refer to related technologies.

[0075] The present disclosure also provides a preparation method of the tab of the electrode as described above, as shown in Figure 6 and includes the following steps:

[0076] Step S61: Mix the coating material and the conductive material to form a coating material;

[0077] Step S63: Coat the coating material on the surface of the composite current collector.

[0078] The present disclosure also provides a preparation method of the tab welding structure of the composite current collector layer as described above, which includes the following step: welding the metal tab to the tab of the electrode.

[0079] The embodiment of the present disclosure also provides a composite electrode, which includes the tab of the electrode described in any one of the above, or the tab of the electrode prepared by the preparation method of the tab of the electrode as described above, or the tab welding structure of the composite current collector layer as described above, or the tab welding structure of the composite current collector layer prepared by the preparation method of the tab welding structure of the composite current collector layer as described above.

[0080] The embodiment of the present disclosure also provides a preparation method of the composite electrode, which includes the preparation method of the tab of the electrode as described above.

[0081] The embodiment of the present disclosure provides a lithium battery, the structure of which is as shown in Figure 7As shown in the figure, it includes a negative current collector 200 made of the composite electrode sheet as described above. A negative active material 210 is provided inside the negative current collector 200. It also includes a positive current collector 300 made of the composite electrode sheet as described above. A positive active material 310 is provided inside the positive current collector 300. It further includes a separator 400 disposed between the negative current collector 200 and the positive current collector 300. Other structures of the lithium battery will not be elaborated here and can be referred to relevant technologies.

[0082] The embodiment of the present disclosure provides a preparation method of a lithium battery, including the preparation method of the composite electrode sheet as described above.

[0083] The following introduces the composite current collector welding structure, its preparation process and test data through specific embodiments:

[0084] Example 1:

[0085] A composite current collector composite layer welding structure includes a composite current collector composite layer, a coating layer and a metal tab. The composite current collector composite layer is composed of a plurality of composite current collector monomers (as Figure 1 shown); the coating layer is formed by coating a coating material on each layer of the composite current collector monomer, and the metal tab is welded to the composite current collector composite layer through the coating layer;

[0086] The coating material includes a coating material and a conductive material. The mass percentage of the conductive material in the coating material is 5%. The conductive material is Cu metal powder. The coating material is composed of styrene-butadiene rubber solution and polyvinylidene fluoride. The viscosity of the coating material is 500 cps, and the mass percentage of the styrene-butadiene rubber solution and polyvinylidene fluoride is 5%.

[0087] First, add the styrene-butadiene rubber solution and polyvinylidene fluoride, stir evenly, then add the Cu metal powder, stir evenly, and then evenly coat the surface of the composite current collector monomer to form a coating layer;

[0088] Stack 55 layers of copper composite current collectors 1 as Figure 2 shown to form a copper composite current collector stack 100;

[0089] Weld a metal tab 4 on the coating layer to obtain a composite current collector composite layer welding structure, as Figure 3 shown.

[0090] The coating area of the coating layer is 30% larger than the projected area of the metal tab;

[0091] Example 2:

[0092] Example 2 is the same as Example 1, the difference is that:

[0093] The composite current collector is a 55-layer aluminum composite current collector monomer;

[0094] The coating layer includes a coating material and a conductive material. The mass percentage of the conductive material in the coating material is 50%. The conductive material is Cu metal powder. The coating material is composed of phenolic epoxy resin and polyvinyl alcohol. The viscosity of the coating material is 20,000 cps. 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. The coating area of the coating layer is 50% larger than the projected area of the metal tab;

[0095] Example 3: Example 3 is the same as Example 1, except that: the copper composite current collector monomer 1 is 20 layers;

[0096] Example 4: Example 4 is the same as Example 1, except that: the aluminum composite current collector monomer 1 is 80 layers;

[0097] Example 5: Example 5 is the same as Example 1, except that:

[0098] The coating layer includes a coating material and a conductive material. The mass percentage of the conductive material in the coating material is 50%. The conductive material is Cu metal powder. The coating material is composed of N-methylpyrrolidone and polytetrafluoroethylene. The viscosity of the coating material is 5,000 cps.

[0099] After being stirred evenly, it is uniformly coated on the upper surface of the composite layer of the composite current collector. The coating area is the whole sheet coating;

[0100] Example 6: Example 6 is the same as Example 5, except that: the conductive material is Al metal powder; after being stirred evenly, it is uniformly coated on the upper surface of the composite layer of the composite current collector. The coating area of the coating layer is 30% larger than the projected area of the metal tab area;

[0101] Example 7: Example 7 is the same as Example 5, except that: the conductive material is Al metal powder; after being stirred evenly, it is uniformly coated on the upper surface of the composite layer of the composite current collector. The coating area of the coating layer is 50% larger than the projected area of the metal tab area;

[0102] Example 8: Example 8 is the same as Example 5, except that: the conductive material is Al metal powder; after being stirred evenly, it is uniformly coated on the entire upper surface of the composite layer of the composite current collector;

[0103] Example 9: Example 9 is the same as Example 5, except that: the conductive material is Ni metal powder; after being stirred evenly, it is uniformly coated on the entire upper surface of the composite layer of the composite current collector. The coating area of the coating layer is 30% larger than the projected area of the metal tab area;

[0104] Example 10: Example 10 is the same as Example 5, except that: the conductive material is Ni metal powder; after being stirred 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 coating layer is 50% larger than the projected area of the metal tab;

[0105] Example 11: Example 11 is the same as Example 5, except that: the conductive material is Ni metal powder; after being stirred evenly, it is evenly coated on the entire upper surface of the composite layer of the composite current collector;

[0106] Example 12:

[0107] Example 12 is the same as Example 5, except that: the coating layer further adds a polyolefin (TPO) photo-curing agent, and the mass percentage of the curing agent and the conductive material is 0.1%.

[0108] Example 13:

[0109] Example 13 is the same as Example 5, except that: the coating layer further adds an azobisisobutyronitrile (AIBN) thermal curing agent, and the mass percentage of the curing agent and the conductive material is 1%.

[0110] The coating material is composed of phenolic epoxy resin and sodium carboxymethyl cellulose, and the viscosity of the coating material is 15000 cps.

[0111] Example 14:

[0112] Example 14 is the same as Example 5, except that: the coating layer further adds polyetheramine, and the mass percentage of the polyetheramine and the conductive material is 0.1%.

[0113] Example 15:

[0114] Example 15 is the same as Example 5, except that: the coating layer further adds acrylate, and the mass percentage of the acrylate and the conductive material is 1%.

[0115] Example 16:

[0116] Example 16 is the same as Example 5, except that: the coating 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%.

[0117] Example 17:

[0118] Example 17 is the same as Example 5, except that: the coating layer further adds a silane coupling agent, and the mass percentage of the silane coupling agent and the conductive material is 1%.

[0119] Comparative example: Without coating any substance, directly weld the tab welding layer on the surface of the multi-layer composite current collector.

[0120] Table 1 Comparison of tab welding performance of composite current collectors

[0121]

[0122] The above Examples 1-17 and the comparative example were tested, and the test performance comparison results in Table 1 could be obtained. Among them, in Examples 1-17, the components of the organic solvent and the solute were the same, that is, the formed coating slurry was the same, mainly composed of an environmentally friendly aromatic hydrocarbon organic solvent and an environmentally friendly thermoplastic resin. The difference was that different types of conductive materials were added respectively. Among them, pure metal powder Cu was added in Examples 1-5, but the current collector material, the number of current collector layers, the mass ratio of the conductive material, and the coating area of the coating layer were different. Examples 1 and 2 were coated on Cu and Al current collector materials respectively; Examples 1 and 3, and Examples 2 and 4 were comparisons of different numbers of current collector layers; Examples 1 and 5 were 5% and 50% of the conductive material respectively. Pure metal powder Al was added in Examples 6-8, but the coating areas of the coating layers were different, which were 30% beyond the projection area of the metal tab, 50% beyond the projection area of the metal tab, and completely covering the composite layer of the composite current collector respectively. Pure metal powder Ni was added in Examples 9-11, but the coating areas of the coating layers were different, which were 30% beyond the projection area of the metal tab, 50% beyond the projection area of the metal tab, and completely covering the composite layer of the composite current collector respectively. Different proportions of curing agents or coupling agents were added in Examples 13-17. The following analysis conclusions could be drawn from the welding effect and electrical performance test results in Table 1.

[0123] For the welding internal resistance, in Examples 1-5, it is the internal resistance of the pure metal powder Cu coating. From the comparison between Examples 1 and 2, it can be seen that the Cu metal powder can be applied to the welding of both copper composite current collectors and aluminum composite current collectors; Examples 1 and 3 are the welding internal resistances of Cu metal particles with different numbers of layers. The lower the number of layers, the lower the welding internal resistance, but it cannot meet the requirements of the number of layers in the battery cell production line; Examples 2 and 4 are the welding internal resistances of Al metal particles with different numbers of layers. The higher the number of layers, the higher the internal resistance, and there is a significant difference compared to the welding internal resistance of 140 mΩ in Comparative Example 1. The welding internal resistance of Example 5 is less than that of Example 1. It can be seen that the higher the mass ratio of the conductive material in the coating layer and the larger the coverage area, the smaller the welding internal resistance. The welding internal resistances of the pure metal powder Al coatings in Examples 6-8 are roughly the same within each coated area range, but the larger the coverage area, the smaller the welding internal resistance. It can be seen that increasing the coating area of the coating layer can reduce the welding internal resistance. The welding internal resistances of the pure metal powder Ni coatings in Examples 9-11 are roughly the same within each coated area range, but the larger the coverage area, the smaller the welding internal resistance. It can be seen that increasing the coating area of the coating layer can reduce the welding internal resistance. Comparing Examples 1-11 can show that under the condition of the same coating area, the welding internal resistance of Cu metal particles is the smallest, and the welding internal resistance of pure metal powder Ni is the largest. Therefore, Cu metal particles have a greater advantage in terms of welding internal resistance. At the same time, the welding internal resistances of Examples 1-11 are much smaller than 140 in the comparative example, and the difference is relatively obvious. Adding different proportions of curing agents or coupling agents in Examples 12-17 will reduce the welding internal resistance and play a certain role in improving the welding internal resistance.

[0124] For the direct tensile force, the welding direct tensile forces of Cu metal particles in Examples 1-5 are generally high. Examples 1 and 3 are the welding direct tensile forces of Cu metal particles with different numbers of layers applied to copper composite current collectors. The lower the number of layers, the higher the welding direct tensile force, but it cannot meet the requirements of the number of layers in the battery cell production line; Examples 2 and 4 are the welding direct tensile forces of Cu metal particles with different numbers of layers applied to aluminum composite current collectors. The higher the number of layers, the higher the internal resistance. Compared with the direct tensile force of 5.87 N / 15 m in Comparative Example, the difference is relatively large; in Examples 1 and 5, the direct tensile forces of Cu metal particles are roughly equivalent within the coated areas, but the larger the coverage area, the greater the direct tensile force. It can be seen that increasing the coating area of the coating layer can improve the direct tensile force of the composite layer of the composite current collector and increase the tensile resistance. The direct tensile forces of Al metal particles in Examples 6-8 are roughly equivalent within the coated areas, but the larger the coverage area, the greater the direct tensile force. It can be seen that increasing the coating area of the coating layer can improve the direct tensile force of the composite layer of the composite current collector and increase the tensile resistance. The direct tensile force of Al metal particles is less than that of Cu metal particles within each coated area; the direct tensile forces of Ni metal particles in Examples 9-11 are roughly equivalent within the coated areas, but the larger the coverage area, the greater the direct tensile force. It can be seen that increasing the coating area of the coating layer can improve the direct tensile force of the composite layer of the composite current collector and increase the tensile resistance. The direct tensile force of Ni metal particles is greater than that of Cu metal particles and Al metal particles. At the same time, the direct tensile forces of Examples 1-11 are much greater than the direct tensile force of 5.87 in the comparative example, and the difference is relatively obvious. 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.

[0125] Regarding the temperature rise of the 3C charge and discharge battery cells, in Examples 1 and 3, the temperature rise of the battery cells with different numbers of layers of Cu metal particles on the copper composite current collector battery cells is such that the lower the number of layers, the smaller the temperature rise. Starting from 30°C, the temperature rises to 50°C and 40°C respectively, but the low number of layers cannot meet the requirements of the number of layers in the battery cell production line. In Examples 2 and 4, the temperature rise of different numbers of layers of Cu metal particles on the aluminum composite current collector battery cells is such that the higher the number of layers, the greater the temperature rise. However, compared with the temperature rise of 40°C in the comparative example, the difference is relatively large. In Examples 1 and 5, the temperature rise of Cu metal particles in different coating area ranges is such that the larger the coverage area, the smaller the temperature rise. Starting from 30°C, the temperature rises to 50°C and 45°C respectively. It can be seen that increasing the coating area of the coating layer can increase the heat dissipation area, thereby reducing the temperature rise. Examples 6 - 8 are the temperature rise of the battery cells with Al metal particles. With the increase of the coating area, the temperature rise decreases significantly. Starting from 30°C, they rise to 53°C, 50°C, and 46°C respectively, with the highest increase of 23°C and the lowest increase of 16°C. It can be seen that the area of the coating area has a greater impact on the temperature rise of the battery. In the case of full coverage, the temperature only rises by 16°C. For the poly-NI metal powder in Examples 9 - 11, with the increase of the coating area, the temperature rise also decreases significantly. Starting from 30°C, they rise to 58°C, 53°C, and 49°C respectively, with the highest increase of 28°C and the lowest increase of 19°C. It can be seen that the area of the coating area has a greater impact on the temperature rise of the battery. For the three metal powders, the Cu metal powder material is the most ideal for controlling the temperature rise. In the lowest Example 5, it only rises by 15°C and reaches 45°C. For the temperature rise of the 3C charge and discharge battery cells in Examples 1 - 11, it is much lower than 70°C in the comparative example, and the difference is relatively obvious. 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.

[0126] Regarding the cycle number / discharge capacity retention of 70%, it refers to the cycle number when the discharge capacity is retained at 70%. In Examples 1 - 5, the cycle numbers of the pure metal particles with the same number of layers are generally relatively high. Especially in Examples 4 and 5, it can be seen that the cycle numbers are the highest when Au and Ag are added. However, due to the high prices of Au and Ag, in order to balance the cost, Cu and Al in Examples 1 and 2 can be selected. In Examples 1 and 3, the cycle numbers of different numbers of layers of Cu metal particles are such that the lower the number of layers, the higher the cycle number, but it cannot meet the requirements of the number of layers in the battery cell production line. In Examples 2 and 4, the cycle numbers of different numbers of layers of Al metal particles are such that the higher the number of layers, the higher the internal resistance. Compared with the cycle number of 326 in the comparative example, the difference is relatively large. The price of Cu in Example 1 is relatively low, and it also has a relatively low cycle number, which can meet the requirements of lithium batteries. Compared with the cycle number of 326 in the comparative example, the difference is relatively large.

[0127] Regarding the cycle life / discharge capacity retention of 70%, it refers to the cycle life when the discharge capacity retention is 70%. The cycle lives of the Cu metal materials in Examples 1-5 are generally high, all greater than 1000 cycles, and there is a significant difference compared to the cycle life of Comparative Example 367. Examples 1 and 3 are the cycle lives of Cu metal particles with different numbers of layers. The lower the number of layers, the higher the cycle life, but it cannot meet the requirements of the number of layers in the battery cell production line. Examples 2 and 4 are the cycle lives of Al metal particles with different numbers of layers. The higher the number of layers, the higher the internal resistance and the lower the cycle life, and there is a significant difference compared to the cycle life of Comparative Example 367. Examples 1 and 5 are the cycle lives of Cu metal particles within different coating area ranges. The larger the coating area, the better heat dissipation will improve the cycle life. The cycle lives of the Al metal particles in Examples 6-8 are also generally high, reaching more than 1100 cycles, slightly lower than the cycle life of the Cu metal material, and there is a significant difference compared to the cycle life of Comparative Example 367. The cycle lives of the NI metal materials in Examples 9-11 slightly decrease, but are all greater than 1000 cycles, and there is a significant difference compared to the cycle life of Comparative Example 367. Among Examples 1-11, at the same number of layers, the Cu metal material has the highest cycle life because it has better temperature control. Adding different proportions of curing agents or coupling agents in Examples 12-17 will increase the cycle life and play a certain role in improving the cycle life of the battery cell.

[0128] In summary, for pure metal particle Cu with the coating area completely covering the composite current collector laminate, it has better welding internal resistance and direct tensile strength, the cycle life / discharge capacity retention is 70%, and it shows outstanding performance in controlling the temperature rise of 3C charge-discharge battery cells.

[0129] Figure 8 The following are photos of the welding effects of the tab welding structures of some embodiments of the present disclosure. There is no welding leakage at the welding position 600. Figure 9 The following are photos of the tab welding effects of the above comparative examples. 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 and there is no welding leakage, while Figure 9 the welding has obvious welding leakage marks.

[0130] Finally, it should be noted that the various 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 various embodiments can be referred to each other.

[0131] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit it; 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 on 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 various embodiments of the present disclosure.

Claims

1. A pole piece tab, characterized in that, Comprising: At least one composite current collector, the composite current collector at least comprising a substrate layer and conductive layers disposed on both sides of the substrate layer, and an underlayer is included between the substrate layer and the conductive layers; At least one surface of the composite current collector is provided with a coating layer, the coating layer is formed by coating a coating material on at least a part of the surface of the composite current collector, and the proportion of the projection of the coating layer on the surface of the composite current collector is within a preset range; The coating material comprises a mixture composed of a coating slurry and a conductive material, the mass percentage of the conductive material in the coating material is 5% - 70%, the conductive material comprises metal particulate material, and the particle size of the metal particulate material is less than 200 microns; Wherein, the coating slurry is generated by a first type of substance and at least one second type of substance, the viscosity of the coating slurry is 50 - 10000 cps, and the mass percentage of the second type of substance in the coating slurry is 1% - 90%; The coating layer is used for welding a metal tab, and the projection of the metal tab on the surface of the composite current collector is within the projection range of the coating layer.

2. The tab of the electrode tab according to claim 1, wherein The area of the projection of the coating layer on the surface of the composite current collector is 25% - 60% larger than the area of the projection of the metal tab on the surface of the composite current collector.

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

4. A tab welding structure, characterized in that, Comprising: n pole piece tabs and metal tabs according to any one of claims 1 - 3, the metal tab is welded to the pole piece tab, 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 welding 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 a coating slurry and a conductive material to form a coating material; Coating the coating material on the surface of the composite current collector.

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

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

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

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