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

Abstract

The invention provides a pole piece tab, a tab modified structure, a composite pole piece, a lithium battery and a method thereof, the pole piece tab comprises at least one composite current collector, and the composite current collector at least comprises a non-conductive substrate and conductive layers arranged on two sides of the non-conductive substrate; a modified layer is arranged on the surface of the composite current collector, the modified layer is formed by coating at least one part of the surface of the composite current collector with a modified material, and the proportion of the projection of the modified layer on the surface of the composite current collector is within a preset range; the modified material comprises a mixture composed of a modified liquid and a conductive material, the conductive material accounts for 5%-70% of the mass of the welding material, and the conductive material comprises a conductive polymer material; wherein the modification liquid is prepared from a first composition and at least one second composition, the viscosity of the modification liquid is 50-10000 cps, and the mass percent of the second composition in the modification liquid is 1%-90%; the modified 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 modified 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 modification 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 manufacture a lithium battery. However, since the polymer film is used in the middle of the composite current collector, 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 modification 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, where the composite current collector at least includes a non-conductive substrate and conductive layers provided on both sides of the non-conductive substrate;

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

[0007] The modification material includes a mixture composed of a modification liquid and a conductive material, the mass percentage of the conductive material in the welding material is 5% - 70%, and the conductive material includes a conductive polymer material;

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

[0009] The modification 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 modification layer.

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

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

[0012] In some embodiments, the conductive polymer material is selected from at least one of the following: polypyrrole polymer material, polyaniline polymer material, polythiophene polymer material.

[0013] In some embodiments, the modified layer makes the internal resistance of the battery cell between 20 mΩ and 35 mΩ.

[0014] In some embodiments, under the condition of the same area of the modified layer, the conductive particulate is a polypyrrole polymer material.

[0015] In some embodiments, the modified layer makes the temperature rise of the charge and discharge of the battery cell not exceed 35 degrees.

[0016] In some embodiments, when the discharge capacity is maintained at 70%, the modified layer makes the number of cycles of the battery cell greater than 1000 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 modified 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 modified 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 modified 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%.

[0024] An embodiment of the present disclosure provides an ear modification structure, including: n tab ears of the electrode sheet as described in any one of the above and a metal tab ear, and the metal tab ear is welded to the tab ear of the electrode sheet, where n = 20 - 80.

[0025] An embodiment of the present disclosure provides a composite electrode sheet, and the composite electrode sheet includes the tab ear of the electrode sheet as described in any one of the above, or the ear modification structure as described above.

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

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

[0028] Mix the modification liquid and the conductive material to form a modified material;

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

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

[0031] Weld the metal tab ear to the tab ear of the electrode sheet.

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

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

[0035] For the tab ear of the electrode sheet described in the present disclosure, by providing a modified layer on the outer side of the composite current collector layer and controlling the coating area of the modified layer, the tab welding performance of the composite current collector can be improved, preventing missed welding and over-welding, and the electrical conductivity and heat dissipation performance after welding of the composite layer of the composite current collector can also be improved, 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 here are incorporated into the specification and form 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 Schematic structural diagram of a composite current collector for some embodiments of the present disclosure.

[0038] Figure 2 Schematic structural diagram of a pole tab for some embodiments of the present disclosure.

[0039] Figure 3 Schematic structural diagram of the modified structure of the composite layer of a composite current collector for some embodiments of the present disclosure.

[0040] Figure 4 Schematic structural diagram of the modified structure of the composite layer of a composite current collector for some other embodiments of the present disclosure.

[0041] Figure 5 Schematic structural diagram of the modified structure of the composite layer of a composite current collector for some other embodiments of the present disclosure.

[0042] Figure 6 Flow chart of the preparation method of the modified structure for some embodiments of the present disclosure.

[0043] Figure 7 Schematic structural diagram of a battery for some embodiments of the present disclosure.

[0044] Figure 8 Photo of the welding effect of the modified structure pole tab for some embodiments of the present disclosure.

[0045] Figure 9 Photo of the welding effect of the pole tab for 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 in conjunction with 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 merely a description of the association relationship of 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.

[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 for distinction. For example, without departing from the scope of the embodiments of the present disclosure, the first can also be called the second, and similarly, the second can also be called 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 further includes elements inherent to such a commodity or device. Without more limitations, 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 tabs are 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 welds when welding the tabs. Therefore, it is difficult to obtain good welding results for the tabs of the electrode sheet with traditional welding methods.

[0052] An embodiment of the present disclosure provides a tab of a pole piece, including: at least one composite current collector, the composite current collector at least includes a non-conductive substrate and conductive layers disposed on both sides of the non-conductive substrate; at least one surface of the composite current collector is provided with a modified layer, the modified layer is formed by coating a modified material on at least a part of the surface of the composite current collector, and the proportion of the projection of the modified layer on the surface of the composite current collector is within a preset range; the modified material includes a mixture composed of a modified liquid and a conductive material, the mass percentage of the conductive material in the welding material is 5% to 70%, and the conductive material includes a conductive polymer material; wherein, the modified liquid is generated by a first composition and at least one second composition, the viscosity of the modified liquid is 50 to 10,000 cps, and the mass percentage of the second composition in the modified liquid is 1% to 90%; the modified 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 modified layer.

[0053] For the tab of the pole piece described in the present disclosure, by providing a modified layer on the outer side of the composite current collector layer and controlling the coating area of the modified layer, the tab welding performance of the composite current collector can be improved, preventing missed welding and over-welding, and also improving the electrical conductivity 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 enhancing 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 1 is as Figure 1 shown. A single composite current collector includes a non-conductive substrate, such as a polymer layer 10, and conductive layers 20. The conductive layers 20 are located on at least one side of the polymer layer 10, such as both sides. Optionally, the polymer layer 10 includes a base material 11 and an adhesive layer 12. The adhesive layer 12 is located on at least one surface of the base material 11, such as both sides, and the adhesive layer 12 is located between the base material 11 and the conductive layers 20. The adhesive layer 12 is used to enhance the adhesion between the conductive layers 20 and the base material 11. Of course, the adhesive layer 12 may also be absent. Optionally, the conductive layers 20 include 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 base material 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 base material 11. Of course, the conductive particulate layer 22 may also be absent. A protective layer or the like may be provided outside the conductive layers 20. Referring to the conventional technology, it will not be elaborated here.

[0056] The material of the non-conductive substrate 11 is preferably a polymer film. In some embodiments, the material of the non-conductive substrate 11 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 not easily degraded compared to the PET film, and the BOPP film has better properties 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 pole piece tab, including: at least one composite current collector 1, the composite current collector 1 at least includes a non-conductive substrate and conductive layers provided on both sides of the non-conductive substrate, as Figure 1 shown; a modified layer 3 is provided on the surface of the composite current collector 1, the modified layer 3 is formed by coating a modified material on at least a part of the surface of the composite current collector 1, and the proportion of the projection of the modified layer 3 on the surface of the composite current collector 1 is within a preset range; the modified material includes a mixture composed of a modified liquid and a conductive material, and the mass percentage of the conductive material in the welding material is 5% to 70%, and the conductive material includes a conductive polymer material; wherein, the modified liquid is generated from a first composition and at least one second composition, and the viscosity of the modified liquid is 50 to 10,000 cps. A viscosity of 50 to 10,000 cps is easy to form a uniform coating layer on each composite current collector, and the granular conductive material can also be evenly dispersed and is not easily piled up, which is convenient for enhancing conductivity; the mass percentage of the second composition in the modified liquid is 1% to 90%; the modified layer 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 modified layer 3, as Figures 3 - 5 shown. The pole piece tab of the present disclosure can improve the tab welding performance of the composite current collector, prevent missed welding and over-welding from occurring, and can also improve the conductivity and heat dissipation performance of the composite layer of the composite current collector after welding, 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 by providing a modified layer on the outside of the composite current collector layer and controlling the coating area of the modified layer.

[0058] In some embodiments, as Figure 4 shown, the projected area of each of the modification layers 3 on each layer of the composite current collector composite layer 100 is 25%-60% larger than the projected area of the metal tab 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 modification 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 modification 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 modification liquid 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 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 does not differ significantly 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 more ideal to select a particle size of 1 μm - 10 μm with smaller particle size from the performance parameters.

[0062] In some embodiments, the organic solvent for forming the modified 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 in the above-listed organic solvents, 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 modified liquid after adding the particulate conductive particulate matter, and the viscosity of the formed modified liquid is more suitable for coating, so that the coated modified 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 in the above-listed solutes, such as at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, polyamide elastomer, polyamide, and polyimide, can reasonably control the viscosity of the modified liquid, is environmentally friendly, and makes the conductive particulate matter more easily diffuse in the modified liquid to form a uniform modified liquid after adding the particulate conductive particulate matter, so that the coated modified 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, 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 higher number of cycles with a discharge capacity of 70% remaining.

[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 higher number of cycles with a discharge capacity of 70% remaining.

[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, with advantages such as low price, not easily oxidized, low welding internal resistance, high direct tensile force, low internal resistance of the battery cell, etc. At the same time, it can improve the heat dissipation effect of the battery cell. Compared with not setting a modified layer, 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 modifying liquid 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 a photo-curing agent, curing can be carried out under light, avoiding the influence of heating on the stability of each film layer. Selecting a thermal-curing agent can rapidly cure by heating in cases where light is not convenient.

[0068] In some embodiments, the modifying liquid 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-mentioned accelerator can accelerate the reaction rate of the modifying liquid, improve the mixing efficiency of the solvent and solute, and rapidly form a stable modifying liquid.

[0069] In some embodiments, the modifying liquid 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-mentioned coupling agent can enhance the binding force between the solvent and solute, enhance the stability of the modifying liquid and the direct tensile force of welding, and easily form a stable modified structure.

[0070] As Figures 3 - 5 shown, an embodiment of the present disclosure provides an ear modification structure, including: a multi-layered composite current collector stack 100 formed by stacking n layers of composite current collectors, where n is a natural number from 20 to 80, such as 55; a modified layer 3 formed by coating a modifying material on each layer of the composite current collector, and the modified layers 3 on each composite current collector overlap in the projection on the composite current collector stack 100. The modified layer 3 includes a modifying liquid and particulate conductive material; a metal ear 4 is welded to the outside of the composite current collector stack 100 through the modified layer 3.

[0071] The multi-layer stacked composite current collector composite layer 100 is formed by stacking single-layer composite current collectors 1, 2, ……, n-1, and n. Generally, n ranges from 20 to 80, for example, 55 layers. That is, after stacking 20 to 80 layers of composite current collectors to form the multi-layer stacked composite current collector composite layer 100, a battery is manufactured. In the related art, it is very difficult to directly weld the tab 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 modified 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, which has extremely high application value.

[0072] Among them, the single-layer composite current collectors 1, composite current collector 2, composite current collector n-1, and composite current collector n can be composite current collectors with the same or different structures. For example, each single-layer composite current collector is as Figure 1 shown.

[0073] For the tab modification structure described in this disclosure, by coating the modified layer on each layer of the multi-layer stacked composite current collector layer and controlling the area of the modified layer to at least cover 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 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.

[0074] The embodiment of this disclosure also provides a composite electrode. The composite electrode includes the composite current collector tab modification structure described in any one of the above. Other structures of the composite electrode will not be elaborated here and can refer to the related art.

[0075] The embodiment of this disclosure provides a lithium battery, including the composite electrode described above. Other structures of the lithium battery will not be elaborated here and can refer to the related art.

[0076] This disclosure also provides a preparation method for the electrode tab as described above, as Figure 6 shown, including the following steps:

[0077] Step S61: Mix the modification liquid and the conductive material to form a modification material;

[0078] Step S63: Coat the modification material on the surface of the composite current collector.

[0079] This disclosure also provides a preparation method for the tab modification structure of the composite current collector layer as described above, including the following step: Weld the metal tab to the electrode tab.

[0080] An embodiment of the present disclosure further provides a composite electrode tab, which includes the electrode tab ear described in any one of the above, or an electrode tab ear prepared by using the preparation method of the electrode tab ear described above, or the modified structure of the composite current collector layer tab ear described above, or a modified structure of the composite current collector layer tab ear prepared by using the preparation method of the modified structure of the composite current collector layer tab ear described above.

[0081] An embodiment of the present disclosure further provides a preparation method of a composite electrode tab, which includes the preparation method of the electrode tab ear described above.

[0082] An embodiment of the present disclosure provides a lithium battery, the structure of which is as Figure 7 shown, and includes a negative current collector 200 made of the composite electrode tab described above, a negative active material 210 is arranged inside the negative current collector 200, and further includes a positive current collector 300 made of the composite electrode tab described above, a positive active material 310 is arranged inside the positive current collector 300, and further 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 will not be elaborated here and can refer to related technologies.

[0083] An embodiment of the present disclosure provides a preparation method of a lithium battery, which includes the preparation method of the composite electrode tab described above.

[0084] The following introduces the modified structure of the composite current collector, its preparation process and test data through specific examples:

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

[0086] The modified material includes a modified liquid and a conductive material. The mass percentage of the conductive material in the modified material is 5%. The conductive material is granular polypyrrole polymer material powder. The modified liquid is composed of a styrene-butadiene rubber solution and polyvinylidene fluoride. The viscosity of the modified liquid 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 and then add the polypyrrole polymer material powder, stir evenly, and then evenly coat the surface of the composite current collector monomer to form a modified layer;

[0088] Stack 55 layers of copper composite current collectors 1 as shown in Figure 3 shown to form a copper composite current collector layer 100;

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

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

[0091] Example 2: Example 2 is the same as Example 1, except that:

[0092] The composite current collector is a 55-layer aluminum composite current collector monomer;

[0093] The modified layer includes a modifying liquid and a conductive material. The mass percentage of the conductive material in the modifying material is 50%. The conductive material is polypyrrole polymer material particles. The modifying liquid is composed of phenolic epoxy resin and polyvinyl alcohol. The viscosity of the modifying liquid 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. The coated area of the modified layer is 50% larger than the projected area of the metal tab;

[0094] Example 3: Example 3 is the same as Example 1, except that: The copper composite current collector monomer 1 is 20 layers;

[0095] Example 4: Example 4 is the same as Example 1, except that: The aluminum composite current collector monomer 1 is 80 layers;

[0096] Example 5: Example 5 is the same as Example 1, except that:

[0097] The modified layer includes a modifying liquid and a conductive material. The mass percentage of the conductive material in the modifying material is 50%. The conductive material is granular polypyrrole polymer. The modifying liquid is composed of N-methylpyrrolidone and polytetrafluoroethylene. The viscosity of the modifying liquid is 5000 cps.

[0098] After stirring evenly, it is uniformly coated on the upper surface of the composite layer of the composite current collector, and the coated area is the whole sheet coating;

[0099] Example 6: Example 6 is the same as Example 5, except that: The conductive material is polyaniline polymer material; After stirring evenly, it is uniformly coated on the upper surface of the composite layer of the composite current collector. The coated area of the modified layer is 30% larger than the projected area of the metal tab region;

[0100] Example 7: Example 7 is the same as Example 5, except that: The conductive material is polyaniline polymer material; After stirring evenly, it is uniformly coated on the upper surface of the composite layer of the composite current collector. The coated area of the modified layer is 50% larger than the projected area of the metal tab region;

[0101] Example 8: Example 8 is the same as Example 5, except that: the conductive material is a polyaniline polymer material; after being stirred evenly, it is evenly coated on the entire upper surface of the composite layer of the composite current collector;

[0102] Example 9: Example 9 is the same as Example 5, except that: the conductive material is poly(thiophene) polymer 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 modified layer is 30% larger than the projected area of the metal tab;

[0103] Example 10: Example 10 is the same as Example 5, except that: the conductive material is poly(thiophene) polymer 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 modified layer is 50% larger than the metal tab projection area;

[0104] Example 11: Example 11 is the same as Example 5, except that: the conductive material is poly(thiophene) polymer powder; after being stirred evenly, it is evenly coated on the entire upper surface of the composite layer of the composite current collector;

[0105] Example 12:

[0106] Example 12 is the same as Example 5, except that: the modified layer further adds a polyolefin (TPO) photo-curing agent, and the mass percentage of the curing agent and the conductive material is 0.1%.

[0107] Example 13:

[0108] Example 13 is the same as Example 5, except that: the modified layer further adds an azodiisobutyronitrile (AIBN) thermal curing agent, and the mass percentage of the curing agent and the conductive material is 1%.

[0109] The modified liquid is composed of phenolic epoxy resin and sodium carboxymethyl cellulose, and the viscosity of the modified liquid is 15000 cps.

[0110] Example 14:

[0111] Example 14 is the same as Example 5, except that: the modified layer further adds polyetheramine, and the mass percentage of the polyetheramine and the conductive material is 0.1%.

[0112] Example 15:

[0113] Example 15 is the same as Example 5, except that: the modified layer further adds acrylate, and the mass percentage of the acrylate and the conductive material is 1%.

[0114] Example 16:

[0115] Example 16 is the same as Example 5, except that: a chromium complex coupling agent is further added to the modified layer, and the mass percentage of the chromium complex coupling agent and the conductive material is 0.1%.

[0116] Example 17:

[0117] Example 17 is the same as Example 5, except that: a silane coupling agent is further added to the modified layer, and the mass percentage of the silane coupling agent and the conductive material is 1%.

[0118] Comparative example: The comparative example is the same as Example 5, except that: the projected area of the coated area of the modified layer on the surface of the composite current collector is 30% smaller than the projected area of the metal tab on the surface of the composite current collector.

[0119] Table 1 Comparison of the welding performance of the composite current collector tabs

[0120]

[0121] Testing the above Examples 1-17 and the comparative example, the test performance comparison results in Table 1 can be obtained. Among them, in Examples 1-11, the components of the two compositions forming the modified liquid are the same, that is, the formed modified liquid is the same, mainly formed by an environmentally friendly aromatic hydrocarbon organic solvent and an environmentally friendly thermoplastic resin. The difference is that different types of conductive particles are added respectively. Among them, in Examples 1-5, polypyrrole polymer materials are added, but the coating areas of the modified layer are different, covering the tab welding layer, exceeding the projected area of the metal tab by 30%, exceeding the projected area of the metal tab by 50%, and completely covering the composite layer of the composite current collector respectively. In Examples 6-8, polyaniline polymer materials are added, but the coating areas of the modified layer are different, covering the tab welding layer, exceeding the projected area of the metal tab by 30%, exceeding the projected area of the metal tab by 50%, and completely covering the composite layer of the composite current collector respectively. In Examples 9-11, polythiophene polymer materials are added, but the coating areas of the modified layer are different, exceeding the projected area of the metal tab by 30%, exceeding the projected area of the metal tab by 50%, and completely covering the composite layer of the composite current collector respectively. In Examples 13-17, curing agents or coupling agents with different proportions are added. The following analysis conclusions can be drawn from the welding effect and electrical performance test results in Table 1.

[0122] Regarding the welding internal resistance, the welding internal resistances of the polypyrrole polymer materials in Examples 1-5 are approximately the same within the coated areas. However, the larger the coverage area, the smaller the welding internal resistance. It can be seen that increasing the coating area of the modified layer can reduce the welding internal resistance. The welding internal resistances of the polyaniline polymer materials in Examples 6-8 are approximately the same within the coated areas. However, the larger the coverage area, the smaller the welding internal resistance. It can be seen that increasing the coating area of the modified layer can reduce the welding internal resistance. The welding internal resistances of the polythiophene polymer materials in Examples 9-11 are approximately the same within the coated areas. However, the larger the coverage area, the smaller the welding internal resistance. It can be seen that increasing the coating area of the modified layer can reduce the welding internal resistance. Comparing Examples 1-11 shows that under the condition of the same coating area, the polypyrrole polymer material has the smallest welding internal resistance, and the polythiophene polymer material has the largest welding internal resistance. Therefore, the polypyrrole polymer material has 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 105 of 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.

[0123] Regarding the direct tensile force, the direct tensile forces of the polypyrrole polymer materials in Examples 1-5 are approximately the same within the coated areas. However, the larger the coverage area, the greater the direct tensile force. It can be seen that increasing the coating area of the modified layer can increase the direct tensile force of the composite layer of the composite current collector and enhance the tensile resistance. The direct tensile forces of the polyaniline polymer materials in Examples 6-8 are approximately the same within the coated areas. However, the larger the coverage area, the greater the direct tensile force. It can be seen that increasing the coating area of the modified layer can increase the direct tensile force of the composite layer of the composite current collector and enhance the tensile resistance. The direct tensile force of the polyaniline polymer material is less than that of the polypyrrole polymer material within each coated area. The direct tensile forces of the polythiophene polymer materials in Examples 9-11 are approximately the same within the coated areas. However, the larger the coverage area, the greater the direct tensile force. It can be seen that increasing the coating area of the modified layer can increase the direct tensile force of the composite layer of the composite current collector and enhance the tensile resistance. The direct tensile force of the polythiophene polymer material is greater than that of the polypyrrole polymer material and the polyaniline polymer material. At the same time, the direct tensile forces of Examples 1-11 are much greater than the direct tensile force of 15.3 of 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 direct tensile force of welding and play a certain role in improving the direct tensile force.

[0124] Regarding the temperature rise of the 3C charge and discharge battery cells, for the polypyrrole polymer materials in Examples 1-5, as the coating area increases, the temperature rise decreases significantly. Starting from 30°C, it rises to 60°C, 55°C, and 45°C respectively, with the highest increase of 30°C and the lowest increase of 15°C. It can be seen that the area of the coating region has a great influence on the temperature rise of the battery. In the case of full coverage, the temperature only rises by 15°C. For the polyaniline polymer materials in Examples 6-8, as the coating area increases, the temperature rise also decreases significantly. Starting from 30°C, it rises to 65°C, 60°C, and 55°C respectively, with the highest increase of 35°C and the lowest increase of 25°C, which is slightly higher than the temperature rise of the polypyrrole polymer materials in Examples 1-3. For the polythiophene polymer materials in Examples 9-11, as the coating area increases, the temperature rise also decreases significantly. Starting from 30°C, it rises to 68°C, 65°C, and 60°C respectively, with the highest increase of 38°C and the lowest increase of 30°C. It can be seen that the area of the coating region has a great influence on the temperature rise of the battery. For the three kinds of polymer conductive particles, the polypyrrole polymer material has the most ideal control over 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 75°C of the comparative example, with an obvious 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.

[0125] Regarding the cycle number / discharge capacity retention of 70%, it refers to the cycle number when the discharge capacity is retained at 70%. The cycle numbers of the polypyrrole polymer materials in Examples 1-5 are generally high, all greater than 1200 cycles, with a large difference compared to the cycle number of Comparative Example 567. The cycle numbers of the polyaniline polymer materials in Examples 6-8 are also generally high, reaching more than 1100 cycles, slightly lower than the cycle numbers of the polypyrrole polymer materials, with a large difference compared to the cycle number of Comparative Example 567. The cycle numbers of the polythiophene polymer materials in Examples 9-11 decrease slightly, but are all greater than 1000 cycles, with a large difference compared to the cycle number of Comparative Example 567. Among Examples 1-11, the polypyrrole polymer material has the highest cycle number because it has 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 cells.

[0126] In summary, for the polypyrrole polymer material when the coating area completely covers the composite current collector composite layer, it has better welding internal resistance, direct tensile force, cycle number / discharge capacity retention of 70%, and outstanding control over the temperature rise of the 3C charge and discharge battery cells.

[0127] Figure 8 The welding effect photos of the tab welding structure of some embodiments of the present disclosure, in which there is no welding leakage at the welding position 600. Figure 9It is a photo of the tab welding effect of the above comparative example, and the non-welded area 700 is very obvious. It can be seen that the welding effect of using the tab welding structure of the present application is good, without welding leakage, while Figure 9 the welding has obvious welding leakage marks.

[0128] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0129] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than 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 described 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 and a pole ear, characterized in that: include: at least one composite current collector, the composite current collector comprising at least a non-conductive substrate and a conductive layer disposed on both sides of the non-conductive substrate; A modified layer is provided on at least one surface of the composite current collector, wherein the modified layer is formed by coating a modified material on at least a portion of the composite current collector surface, and the proportion of the projection of the modified layer on the composite current collector surface is within a preset range; The modified material comprises a mixture of a modified liquid and a conductive material, the conductive material accounts for 5% to 70% by mass of the welding material, and the conductive material comprises a conductive polymer material; Wherein, the modified liquid is generated from a first composition and at least one second composition, the viscosity of the modified liquid is 50 to 10,000 cps, and the mass percentage of the second composition in the modified liquid is 1% to 90%; The modified layer is used for welding a metal electrode tab, and the projection of the metal electrode tab on the surface of the composite current collector is within the projection range of the modified layer.

2. The pole piece and pole ear according to claim 1, characterized in that: The projection area of ​​the modified layer on the composite current collector is 25%-60% larger than the projection area of ​​the metal tab on the composite current collector.

3. The pole piece and tab according to claim 1, characterized in that: The projection of the modified layer on the composite current collector overlaps with the composite current collector.

4. A modified structure of a tab, characterized in that: include: n pole piece tabs and metal tabs as described in any one of claims 1 to 3, wherein the metal tabs are welded to the pole piece tabs, wherein n=20-80.

5. A composite pole piece, characterized in that: The composite pole piece includes the pole piece tab as described in any one of claims 1 to 3, or the pole tab modified structure as described in claim 14.

6. A lithium battery, characterized in that: Including the composite pole piece as described in claim 5.

7. A method for preparing a pole piece and a pole ear as claimed in claims 1 to 3, characterized in that: The following steps are involved: mixing a modified liquid and a conductive material to form a modified material; The modified material is coated on the surface of the composite current collector.

8. A method for preparing the modified tab structure as claimed in claim 4, characterized in that: The following steps are involved: The metal pole ear is welded to the pole piece pole ear.

9. A method for preparing a composite pole piece, characterized in that: The invention comprises a method for preparing the modified tab structure as described in claim 8.

10. A method for preparing a lithium battery, characterized in that: Including the method for preparing the composite pole piece as claimed in claim 9.

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