Cathode tab structure preparation method and cathode tab structure

Abstract

This application provides a method for preparing a positive electrode structure and the positive electrode structure itself. The method for preparing the positive electrode structure includes: coating a first active material onto one side of a current collector to obtain a first active material layer; coating a second active material onto the side of the current collector opposite to the first active material layer to obtain a second active material layer; coating a third active material onto the side of the second active material layer opposite to the current collector to obtain a third active material layer; coating a fourth active material onto the side of the first active material layer opposite to the current collector to obtain a fourth active material layer, thereby obtaining a multilayer coated structure; wherein an insulating region is left on the side of the current collector adjacent to the fourth active material layer; performing a cold pressing operation on the multilayer coated structure; coating or attaching an insulating layer to the fourth active material layer and the insulating region, so that the insulating layer covers the edge of the fourth active material layer adjacent to the insulating region, avoiding the problem of overvoltage of the positive electrode caused by the insulating layer, and improving the performance of the lithium battery.

Description

Technical Field

[0001] This invention relates to the technical field of lithium batteries, and in particular to a method for preparing a positive electrode structure and the positive electrode structure itself. Background Technology

[0002] Currently, the conventional positive electrode for lithium-ion batteries is an active material coated on aluminum foil. However, as the capacity of lithium-ion batteries increases, their safety performance becomes increasingly difficult to guarantee. To improve battery safety, an insulating layer is typically coated on the aluminum foil. However, due to the gap between the active material layer and the insulating layer, puncturing this gap poses a risk of short circuit in the lithium battery. To avoid this gap, traditional technology places one end of the insulating layer between two adjacent active material layers and the other end on the aluminum foil. However, the overlap between the active material layer and the insulating layer increases the thickness of the electrode at the overlap, which in turn increases the risk of overvoltage during cold pressing, thus affecting the performance of the battery cell. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a positive electrode structure and a positive electrode structure that can avoid both needle puncture short circuits and overvoltage of the positive electrode, thereby improving installation performance and performance.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A method for preparing a positive electrode structure, comprising:

[0006] The first active material is coated onto one side of the current collector to obtain the first active material layer;

[0007] A second active material is coated onto the side of the current collector opposite to the first active material layer to obtain a second active material layer.

[0008] A third active material is coated onto the side of the second active material layer that is away from the current collector to obtain a third active material layer;

[0009] A fourth active material is coated onto the side of the first active material layer away from the current collector to obtain a fourth active material layer, thereby obtaining a multilayer coating structure; wherein, the side of the current collector adjacent to the fourth active material layer has an insulating area.

[0010] The multi-layer coated structure is subjected to cold pressing to obtain a multi-layer compacted structure;

[0011] An insulating layer is coated or attached to the fourth active material layer and the insulating region, such that the insulating layer covers the edge of the fourth active material layer adjacent to the insulating region, thereby obtaining a positive electrode structure.

[0012] In one embodiment, the first active material, the second active material, the third active material, and the fourth active material are all at least one of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxide phosphate, sodium vanadium oxide phosphate, lithium vanadium oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, and lithium titanate.

[0013] In one embodiment, the first active substance, the second active substance, the third active substance, and the fourth active substance all further include an adhesive.

[0014] In one embodiment, the adhesive is at least one selected from polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber.

[0015] In one embodiment, the first active substance, the second active substance, the third active substance, and the fourth active substance all further include a conductive agent.

[0016] In one embodiment, the conductive agent is at least one of carbon nanotubes, conductive carbon black, acetylene black, graphene, Ketjen black, and carbon fiber.

[0017] In one embodiment, the insulating layer comprises at least one of inorganic particles and polymers.

[0018] In one embodiment, the inorganic particles are at least one selected from aluminum oxide, silicon dioxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium dioxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.

[0019] In one embodiment, the polymer is at least one selected from the following: a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride, a copolymer of hexafluoropropylene, polystyrene, polyphenylene acetylene, sodium polyvinyl acetate, potassium polyvinyl acetate, polymethyl methacrylate, polyethylene, polypropylene, and polytetrafluoroethylene.

[0020] A positive electrode structure is prepared using the positive electrode structure preparation method described in any of the above embodiments.

[0021] Compared with the prior art, the present invention has at least the following advantages:

[0022] 1. Since the insulating layer covers the boundary between the fourth active material layer and the insulating area, that is, the edge of the fourth active material layer adjacent to the insulating area is covered by the insulating layer, there is no exposed gap between the edge of the fourth active material layer and the insulating layer, which avoids the problem of short circuit caused by needle puncture and improves the safety performance of lithium battery.

[0023] 2. Since the insulating layer is coated or bonded to the fourth active material layer and the insulating area after the cold pressing operation, the problem of overvoltage of the positive electrode caused by the insulating layer is avoided, thus improving the performance of the lithium battery.

[0024] 3. Since the insulating layer can be coated or bonded after the electrode is cold-pressed, the connection quality of the insulating layer is not affected by the cold-pressing operation, thereby improving the connection quality of the insulating layer, which helps to improve the short-circuit protection effect of the insulating layer, and thus makes the lithium battery perform better. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating the steps of a method for preparing a positive electrode structure according to an embodiment;

[0027] Figure 2 for Figure 1 The positive electrode structure prepared by the method shown is a positive electrode structure.

[0028] Figure 3 for Figure 2 A partial structural schematic diagram of the positive electrode plate structure is shown;

[0029] Figure 4 for Figure 3 An enlarged schematic diagram of point A in the positive electrode structure shown;

[0030] Figure 5 for Figure 4 An enlarged schematic diagram of point B in the described positive electrode structure. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0032] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] This application provides a method for preparing a positive electrode structure, comprising: coating a first active material onto one side of a current collector to obtain a first active material layer; coating a second active material onto the side of the current collector opposite to the first active material layer to obtain a second active material layer; coating a third active material onto the side of the second active material layer opposite to the current collector to obtain a third active material layer; coating a fourth active material onto the side of the first active material layer opposite to the current collector to obtain a fourth active material layer, thereby obtaining a multilayer coated structure; wherein an insulating region is left on the side of the current collector adjacent to the fourth active material layer; performing a cold pressing operation on the multilayer coated structure to obtain a multilayer compacted structure; coating or attaching an insulating layer to the fourth active material layer and the insulating region, so that the insulating layer covers the edge of the fourth active material layer adjacent to the insulating region, thereby obtaining a positive electrode structure.

[0035] The aforementioned positive electrode structure preparation method, because the insulating layer covers the boundary between the fourth active material layer and the insulating region—that is, the edge of the fourth active material layer adjacent to the insulating region is covered by the insulating layer—means there is no exposed gap between the edge of the fourth active material layer and the insulating layer. This avoids the problem of short circuits caused by needle punctures, thus improving the safety performance of the lithium battery. Since the insulating layer is coated or bonded to the fourth active material layer and the insulating region after the cold pressing operation, the problem of overvoltage of the positive electrode due to the insulating layer is avoided, improving the performance of the lithium battery. Because the insulating layer can be coated or bonded after the electrode is cold pressed, the connection quality of the insulating layer is not affected by the cold pressing operation, thereby improving the connection quality of the insulating layer and helping to improve the short-circuit protection effect of the insulating layer, ultimately resulting in better performance of the lithium battery.

[0036] To better understand the technical solution and beneficial effects of this application, the following detailed description is provided in conjunction with specific embodiments:

[0037] like Figure 1 As shown, a method for preparing a positive electrode structure according to an embodiment includes:

[0038] S101: The first active material is coated on one side of the current collector to obtain the first active material layer.

[0039] In this embodiment, the current collector is an aluminum foil sheet. The main function of the current collector is to collect the current generated by the active material layer to form a larger current output. The first active material is prepared into a positive electrode slurry, and then the positive electrode slurry is coated on one side of the current collector to form a first active material layer on one side of the current collector. Further, the positive electrode slurry is coated on a portion of the surface of one side of the current collector to form an insulating region on one side of the current collector.

[0040] S103: The second active material is coated on the side of the current collector opposite to the first active material layer to obtain the second active material layer.

[0041] In this embodiment, the current collector is an aluminum foil sheet. Its main function is to collect the current generated by the active material layer to form a larger current output. The second active material is prepared as a positive electrode slurry, and then this slurry is coated onto the side of the current collector facing away from the first active material layer, thus forming the second active material layer on that side. Further, the first and second active material layers are disposed opposite to each other on the two sides of the current collector.

[0042] S105: Coat the third active material onto the side of the second active material layer away from the current collector to obtain the third active material layer.

[0043] In this embodiment, the third active material is prepared into a positive electrode slurry, and then the positive electrode slurry is coated on the side of the second active material layer away from the current collector to form the third active material layer on the second active material layer.

[0044] S107: The fourth active material is coated on the side of the first active material layer away from the current collector to obtain the fourth active material layer, thereby obtaining a multilayer coating structure; wherein, the side of the current collector adjacent to the fourth active material layer has an insulating area.

[0045] In this embodiment, the fourth active material is prepared into a positive electrode slurry, and then the positive electrode slurry is coated onto the first active material layer to form the fourth active material layer. This results in the current collector, the first active material layer, the second active material layer, the third active material layer, and the fourth active material layer together forming a multilayer coating structure. An insulating region is provided on the side of the current collector adjacent to the fourth active material layer, and this insulating region is used to attach an insulating layer.

[0046] S109: Perform cold pressing on the multi-layer coated structure to obtain a multi-layer compacted structure.

[0047] In this embodiment, the multi-layer coating structure is compacted by rollers to increase the density of the first active material layer, the second active material layer, the third active material layer, and the fourth active material layer, thereby improving the performance of the cell structure.

[0048] S111: The insulating layer is coated or attached to the fourth active material layer and the insulating region so that the insulating layer covers the edge of the fourth active material layer adjacent to the insulating region, thus obtaining the positive electrode structure.

[0049] In this embodiment, the insulating layer is attached to the fourth active material layer and the insulating area by coating or bonding, so that the insulating layer covers the edge of the fourth active material layer adjacent to the insulating area, thereby avoiding the exposure of the gap between the edge of the fourth active material layer and the insulating layer.

[0050] The aforementioned positive electrode structure preparation method, because the insulating layer covers the boundary between the fourth active material layer and the insulating region—that is, the edge of the fourth active material layer adjacent to the insulating region is covered by the insulating layer—means there is no exposed gap between the edge of the fourth active material layer and the insulating layer. This avoids the problem of short circuits caused by needle punctures, thus improving the safety performance of the lithium battery. Since the insulating layer is coated or bonded to the fourth active material layer and the insulating region after the cold pressing operation, the problem of overvoltage of the positive electrode due to the insulating layer is avoided, improving the performance of the lithium battery. Because the insulating layer can be coated or bonded after the electrode is cold pressed, the connection quality of the insulating layer is not affected by the cold pressing operation, thereby improving the connection quality of the insulating layer and helping to improve the short-circuit protection effect of the insulating layer, ultimately resulting in better performance of the lithium battery.

[0051] In one embodiment, the first, second, third, and fourth active materials are all at least one of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxide phosphate, sodium vanadium oxide phosphate, lithium vanadium oxide, lithium vanadium oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, and lithium titanate. In this embodiment, applying lithium cobalt oxide to the positive electrode structure has the following advantages: 1. Suppressing battery polarization, reducing thermal effects, and improving rate performance; 2. Reducing battery internal resistance and significantly reducing the dynamic internal resistance increase during cycling; 3. Improving consistency and increasing battery cycle life; 4. Improving the adhesion between the active material and the current collector, reducing electrode manufacturing costs; 5. Protecting the current collector from electrolyte corrosion; 6. Improving the processing performance of lithium iron phosphate and lithium titanate materials. In another embodiment, the negative electrode active material is at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon, silicon oxide, silicon-carbon composite, tin, tin alloy, niobium titanate, and lithium titanate.

[0052] In one embodiment, the first, second, third, and fourth active materials all further include a binder. In this embodiment, the binder is a polymer compound used to adhere the active materials to the current collector during electrode fabrication. Its main functions include bonding and retaining the active materials, enhancing the contact between the active materials and the conductive agent, and between the active materials and the current collector, while also stabilizing the electrode structure. Furthermore, since the commonly used water-soluble binder SBR contains unsaturated double bonds, it can theoretically be oxidized by voltages above 4V, resulting in relatively greater rebound during electrode processing. Secondly, water damages almost all cathode materials; lithium iron phosphate is relatively less affected, but high-nickel materials experience significant lithium leaching, leading to increased slurry pH and decreased capacity. Thirdly, aqueous systems are difficult to dry, and residual moisture affects capacity and cycle life. Fourth, current cathode materials such as lithium cobalt oxide and ternary materials have relatively high densities and large masses per unit volume. When using an SBR+CMC bonding system, water is required as a solvent. However, in the process of preparing such high-density cathode materials, sedimentation in the slurry is very likely to occur, making it impossible to fully disperse the slurry. Once stirring stops, the slurry will settle rapidly. Using PVDF oil-soluble materials as binders, dissolved in an organic solvent (N-methylpyrrolidone, NMP), effectively solves the above problems, stabilizes the electrode structure, and improves the protection of the electrode.

[0053] Furthermore, the adhesive can also be selected from at least one of the following: copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber. In this embodiment, using polyacrylonitrile as the adhesive has the following advantages: 1. It hardly swells in the carbonate solvent of the electrolyte, and the electrode structure is stable during charging and discharging; 2. Its carboxyl group content is higher than that of sodium carboxymethyl cellulose, which can form a stronger hydrogen bond with active materials containing hydroxyl groups on the surface, promoting a more uniform coating on the electrode surface than sodium carboxymethyl cellulose; 3. It can form a denser film in the electrode sheet, increasing the electrical contact between the active material and the current collector; 4. Excellent tensile mechanical strength, which is beneficial for machining. Polytetrafluoroethylene also has excellent chemical stability, electrical insulation, self-lubrication, non-flammability, atmospheric aging resistance, and high and low temperature adaptability, and has high mechanical strength, which is beneficial for improving the stability of the electrode structure.

[0054] In one embodiment, the first, second, third, and fourth active materials all further include a conductive agent. It is understood that the normal charging and discharging process of a lithium battery requires the joint participation of lithium ions and electrons. This necessitates that the electrodes of a lithium-ion battery be mixed conductors of ions and electrons, and that electrode reactions can only occur at the junction of the electrolyte, conductive agent, and active material. Furthermore, the positive electrode active material is often a transition metal oxide or transition metal phosphate, which are semiconductors or insulators with poor conductivity, necessitating the addition of a conductive agent to improve conductivity. In this embodiment, by adding a conductive agent to the first, second, third, and fourth active materials, the conductive contact between the active materials can be increased, improving electronic conductivity. This allows for the collection of microcurrents between the active materials and between the active materials and the current collector, thereby reducing electrode contact resistance and accelerating electron movement.

[0055] Furthermore, the conductive agent is at least one selected from carbon nanotubes, conductive carbon black, acetylene black, graphene, Ketjen black, and carbon fiber. In this embodiment, the conductive agent can form an electronic conduction network that works synergistically with the positive electrode active material, enabling good electronic connection of the electrode active particles. Compared with other conductive agents, carbon nanotube conductive agents can be more easily and fully mixed in the above-mentioned adhesive solution, reducing stirring time and increasing the specific capacity of the battery positive electrode, indirectly increasing the internal space of the cell and improving the energy density of the cell. Conductive graphite also has good conductivity. Its particle size is close to that of the active material particles, and the particles are in point contact with each other, which can form a conductive network structure of a certain scale, improving the conductivity rate and further increasing the capacity of the negative electrode when used. Conductive carbon fiber has a linear structure and easily forms a good conductive network in the electrode, exhibiting good conductivity, thus reducing electrode polarization, lowering battery internal resistance, and improving battery performance. Inside batteries using carbon fiber as a conductive agent, the contact between the active material and the conductive agent is a point-to-line contact. Compared to the point-to-point contact between conductive carbon black and conductive graphite, this not only improves electrode conductivity but also reduces the amount of conductive agent used, thereby increasing battery capacity. Graphene, as a novel conductive agent, due to its unique sheet-like structure (two-dimensional structure), has a point-to-surface contact with the active material rather than the conventional point-to-point contact. This maximizes the effectiveness of the conductive agent, reduces its usage, and allows for the use of more active material, thus increasing lithium battery capacity.

[0056] In one embodiment, the insulating layer comprises at least one of inorganic particles and polymers. It is understood that by coating the blank areas with an insulating layer, and ensuring that the insulating layer is flush with the boundaries of the fourth active material layer and the first active material layer, the first active material layer, the fourth active material layer, and the insulating layer do not overlap or have gaps. This not only improves the safety performance of the battery but also prevents the positive electrode from overvoltage, thus ensuring the battery's electrical performance. To further improve the insulation effect of the insulating layer and the stability of the electrode structure, in this embodiment, the insulating layer comprises at least one of inorganic particles and polymers. Inorganic insulating particles have good insulation properties, and the inorganic insulating particles combine with each other to form an inorganic insulating layer, thereby improving the flatness of the insulating layer and consequently improving the flatness and stability of the electrode structure.

[0057] Furthermore, the inorganic particles are at least one selected from aluminum oxide, silicon dioxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium dioxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. In this embodiment, silicon dioxide has good insulation properties; the resistivity of the thermally oxidized silicon dioxide film is approximately 10¹⁵-10¹⁶ ohm·meters, and silicon dioxide has high dielectric strength and a high breakdown voltage. Aluminum hydroxide, as an inorganic particle in the insulating layer, not only has good insulation properties but also good flame retardancy. In addition, aluminum hydroxide also provides corrosion resistance, thereby effectively improving the safety and stability of the electrode structure.

[0058] In one embodiment, the polymer is at least one selected from the following: a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride, a copolymer of hexafluoropropylene, polystyrene, polyphenylene acetylene, sodium polyvinyl acetate, potassium polyvinyl acetate, polymethyl methacrylate, polyethylene, polypropylene, and polytetrafluoroethylene. It is understood that the polymer insulating layer has advantages such as good insulation, light weight, and good roll forming flatness, thus effectively improving the structural stability and flatness of the electrode structure. To further improve the stability of the polymer insulating layer, in this embodiment, the polymer is at least one selected from the following: a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride, a copolymer of hexafluoropropylene, polystyrene, polyphenylene acetylene, sodium polyvinyl acetate, potassium polyvinyl acetate, polymethyl methacrylate, polyethylene, polypropylene, and polytetrafluoroethylene. The homopolymer of vinylidene fluoride not only has good insulation but also good chemical corrosion resistance, thus effectively improving the stability of the electrode structure.

[0059] In one embodiment, the insulating layer is attached to the fourth active material layer and the insulating region, such that the insulating layer covers the edge of the fourth active material layer adjacent to the insulating region. This ensures that there is no exposed gap between the edge of the fourth active material layer and the insulating layer, avoiding the problem of short circuit caused by needle puncture and improving the safety performance of the lithium battery.

[0060] It is understandable that in subsequent operations of the positive electrode cell structure, the insulating layer is prone to warping due to heat or friction, reducing its firmness and creating a risk of detachment, thus lowering the safety performance of the lithium battery. In one embodiment, after the step of coating or attaching the insulating layer to the fourth active material layer and the insulating region to cover the edge of the fourth active material layer adjacent to the insulating region to obtain the positive electrode structure, the positive electrode structure preparation method further includes: performing a grooving operation on the edge of the insulating layer to form multiple spaced anti-detachment grooves and multiple spaced anti-detachment portions on the edge of the insulating layer.

[0061] In this embodiment, the insulating layer includes an insulating body and multiple anti-detachment portions. The multiple anti-detachment portions are spaced apart and connected to the edge of the insulating body, and an anti-detachment groove is formed between two adjacent anti-detachment portions. Because there is an anti-detachment groove between two adjacent anti-detachment portions, when one anti-detachment portion curls up, it will not directly cause other anti-detachment portions to curl up, thus avoiding the situation where the entire insulating layer curls up, improving the firmness of the insulating layer, and making the short-circuit protection effect of the insulating layer better.

[0062] However, when the scraping force is large, the anti-detachment parts will warp to the edge between two adjacent anti-detachment parts. This will cause the anti-detachment parts to still cause the insulation layer to warp as a whole, thus still posing a risk of the insulation layer falling off and potentially causing the insulation layer's short-circuit protection function to fail. In one embodiment, after the steps of grooving the edge of the insulation layer to form multiple spaced anti-detachment grooves and forming multiple spaced anti-detachment parts on the edge of the insulation layer, the positive electrode structure preparation method further includes: grooving each anti-detachment part to form multiple spaced fracture grooves on each anti-detachment part. In this embodiment, the insulation layer includes an insulation body and multiple anti-detachment parts. The multiple anti-detachment parts are spacedly connected to the edge of the insulation body, and an anti-detachment groove is formed between two adjacent anti-detachment parts. Each anti-detachment part has multiple spaced fracture grooves, which reduces the connection strength between each anti-detachment part and the insulation body. When the scraping force is large, each anti-detachment part will bend to the fracture groove and break, so as to prevent each anti-detachment part from causing other anti-detachment parts to bend. This avoids the problem of overall edge bending when the scraping force is large, which helps to improve the firmness of the insulation layer and thus improves the short circuit protection effect of the insulation layer.

[0063] It is understandable that after each anti-detachment part breaks, the corresponding fracture point will still cause the insulation layer to lift up as a whole after being scraped, which may reduce the strength of the insulation layer and thus cause the insulation layer to fail in preventing short circuits. In one embodiment, in the step of trimming each anti-detachment part to form multiple spaced fracture grooves, after the trimming operation is completed, the insulation layer forms an embedded part in the fracture groove. In this embodiment, the insulation layer includes an insulation body, anti-detachment parts, and embedded parts. There are multiple anti-detachment parts, which are spaced apart and connected to the edge of the insulation body. An anti-detachment groove is formed between two adjacent anti-detachment parts. Each anti-detachment part has multiple spaced fracture grooves. There are multiple embedded parts, which are arranged one-to-one with the multiple fracture grooves. Each embedded part is located in the corresponding fracture groove and connected to the anti-detachment part.

[0064] Furthermore, after performing edge-cutting operations on each anti-detachment part to form multiple spaced fracture grooves, the positive electrode sheet structure preparation method further includes: performing a pressing operation on each embedded part to embed each embedded part into the fourth active material layer, which improves the positional stability of the embedded part, helps to suppress the situation where the fracture point lifts up and pulls the insulation layer up as a whole, improves the positional stability of the insulation layer, and thus improves the short-circuit protection effect of the insulation layer.

[0065] It is understandable that, because the pressing of the embedded parts requires a certain space in the fourth active material layer during pressing, gaps exist between the adhesive backing of each embedded part and the fourth active material layer. This results in lower connection strength between each embedded part and the fourth active material layer, and the insulation layer is at risk of overall lifting. In one embodiment, after the step of pressing each embedded part to embed it into the fourth active material layer, the positive electrode structure preparation method further includes: filling the gaps between each embedded part and the fourth active material layer to improve the connection strength between each embedded part and the fourth active material layer.

[0066] The adhesive backing of each embedded part cannot bond to the fourth active material layer, resulting in low connection strength between the embedded part and the fourth active material layer. To improve the connection strength, in the step of filling the gap between each embedded part and the fourth active material layer, adhesive is used to fill the gap, ensuring that both opposite sides of each embedded part are bonded to the fourth active material layer. This effectively prevents the insulation layer from lifting as a whole, thus ensuring the short-circuit protection effect of the insulation layer.

[0067] In one embodiment, after cold pressing the multilayer coated structure to obtain a multilayer compacted structure, and before coating or bonding the insulating layer to the fourth active material layer and the insulating region so that the insulating layer covers the edge of the fourth active material layer adjacent to the insulating region to obtain the positive electrode structure, the method for preparing the positive electrode structure further includes the following steps: spraying inorganic particles onto the side of the fourth active material layer away from the current collector, the edge of the first active material layer adjacent to the insulating region, the edge of the fourth active material layer adjacent to the insulating region, and the surface of the insulating region. It is understood that because the fourth active material layer and the first active material layer have already been preliminarily cured, the insulating layer has good fluidity, and the insulating region has poor adsorption, making the coating or bonding operation of the insulating layer difficult to control and easily causing problems with poor flatness. To improve the flatness of the insulating layer, in this embodiment, inorganic particles are sprayed onto the side of the fourth active material layer away from the current collector, the edge of the first active material layer adjacent to the insulating region, the edge of the fourth active material layer adjacent to the insulating region, and the surface of the insulating region. This allows the inorganic particles to adhere to these surfaces, thereby enhancing the adsorption force and making the insulating layer material easier to coat and shape, thus improving its flatness. Furthermore, the inorganic particles are the main component of the insulating layer coating, possessing good insulation properties and good compatibility with the insulating layer. Therefore, they enable a tighter contact between the insulating layer and the multilayer structure, thereby improving the stability of the positive electrode structure.

[0068] This application also provides a positive electrode structure, which is prepared by the positive electrode structure preparation method described in any of the above embodiments.

[0069] like Figure 2As shown, the positive electrode structure 20 further includes a current collector 210, a first active material layer 220, a second active material layer 230, a third active material layer 240, a fourth active material layer 250, and an insulating layer 260. One side of the current collector 210 has an adjacent first coating area 211 and an insulating area 212. The side of the current collector 210 away from the first coating area 211 has a second coating area 213. The first active material layer 220 is connected to the first coating area 211, and the second active material layer 230 is connected to the second coating area 250. On region 213, a third active material layer 240 is connected to the side of the second active material layer 230 facing away from the current collector 210, and a fourth active material layer 250 is connected to the side of the first active material layer 220 facing away from the current collector 210. An insulating layer 260 is connected to the insulating region 212 and the side of the fourth active material layer 250 facing away from the current collector 210, so that the insulating layer 120 covers the boundary line between the fourth active material layer 250 and the insulating region 212, that is, the edge of the fourth active material layer 250 adjacent to the insulating region 212 is covered by the insulating layer 260. In this embodiment, the current collector 210 is an aluminum sheet, and the first active material layer 220, the second active material layer 230, the third active material layer 240, and the fourth active material layer 250 are all used to embed lithium ions. The insulating layer 260 can isolate the current collector 210 from the outside to prevent the current collector 210 from short-circuiting.

[0070] In the aforementioned positive electrode structure 20, because the insulating layer 120 covers the boundary between the fourth active material layer 250 and the insulating region 212, that is, the edge of the fourth active material layer 250 adjacent to the insulating region 212 is covered by the insulating layer 260, the boundary between the insulating region 212 and the fourth active material layer 250 is covered by the insulating layer 260, avoiding the problem of short circuit caused by needle puncture and improving the safety performance of the lithium battery. Furthermore, the overlapping portion of the insulating layer 260 and the fourth active material layer 250 is located on the outer side of the fourth active material layer 250 away from the current collector 210, allowing the insulating layer 260 to be connected after the positive electrode is cold-pressed, thereby avoiding the problem of overvoltage of the positive electrode caused by the insulating layer 260 and improving the performance of the lithium battery. Since the insulating layer 260 can be connected after the electrode is cold-pressed, the connection quality of the insulating layer 260 is not affected by the cold-pressing operation, thus improving the connection quality of the insulating layer 260 and contributing to the improvement of the short-circuit protection effect of the insulating layer 260.

[0071] like Figure 2As shown, in one embodiment, the insulating layer 260 is also connected to the edge of the first active material layer 220 adjacent to the insulating region 212, resulting in a larger bonding area for the insulating layer 260, thereby improving the strength of the insulating layer 260 and enhancing its short-circuit protection effect. Furthermore, the insulating layer 260 is also connected to the edge of the fourth active material layer 250 adjacent to the insulating region 212, resulting in an even larger bonding area for the insulating layer 260, further enhancing its strength and further improving its short-circuit protection effect.

[0072] like Figure 2 As shown, furthermore, the edges of the first active material layer 220 adjacent to the insulating region 212 are flush with the edges of the fourth active material layer 250 adjacent to the insulating region 212, resulting in a higher flatness of the connection surface of the insulating layer 260. This reduces the number of bends in the insulating layer 260, thereby improving its connection efficiency. Moreover, because the insulating layer 260 bends less, its resilience is reduced, thus preventing the insulating layer 260 from detaching from the corresponding connection point. This improves the firmness of the insulating layer 260 and helps to enhance its short-circuit protection effect.

[0073] like Figure 2 As shown, in one embodiment, the thickness of the portion of the insulating layer 260 located on the insulating region 212 is greater than the thickness of the first active material layer 220, so that the boundary between the first active material layer 220 and the fourth active material layer 250 is blocked by the insulating layer 260. This prevents the boundary between the first active material layer 220 and the fourth active material layer 250 from being scraped when the insulating layer 260 is connected, thereby preventing the first active material layer 220 and the fourth active material layer 250 from being scraped away from the current collector 210 when the insulating layer 260 is connected, which helps to ensure the performance of the positive electrode structure 20.

[0074] like Figure 2 As shown, in one embodiment, the periphery of the first active material layer 220 coincides with the periphery of the fourth active material layer 250, that is, the first active material layer 220 and the fourth active material layer 250 completely overlap, making the edge formed by the first active material layer 220 and the fourth active material layer 250 smooth. This helps to prevent the first active material layer 220 and the fourth active material layer 250 from being rubbed off by external forces, thereby improving the positional stability of the first active material layer 220 and the fourth active material layer 250 and improving the performance of the lithium battery.

[0075] like Figure 2As shown, in one embodiment, the periphery of the second active material layer 230 coincides with the periphery of the third active material layer 240, that is, the second active material layer 230 and the third active material layer 240 completely overlap, making the edge formed by the second active material layer 230 and the third active material layer 240 smooth. This helps to prevent the second active material layer 230 and the third active material layer 240 from being rubbed off by external forces, thereby improving the positional stability of the second active material layer 230 and the third active material layer 240 and improving the performance of the lithium battery.

[0076] like Figure 2 As shown, in one embodiment, the thickness of the first active material layer 220 is the same as the thickness of the second active material layer 230. In this embodiment, during the rolling process, because the thickness of the first active material layer 220 is equal to the thickness of the second active material layer 230, the pressure on both sides of the current collector 210 is consistent, and the positive electrode structure 20 has better symmetry, thereby improving the consistency and stability of the positive electrode structure 20.

[0077] like Figure 2 As shown, in one embodiment, the thickness of the fourth active material layer 250 is the same as the thickness of the third active material layer 240. In this embodiment, during the rolling process, because the thickness of the fourth active material layer 250 is equal to the thickness of the third active material layer 240, the pressure on both sides of the current collector 210 is consistent, and the positive electrode structure 20 has better symmetry, thereby improving the consistency and stability of the positive electrode structure 20.

[0078] like Figure 3 As shown, in one embodiment, the insulating layer 260 includes an insulating body 261 and anti-detachment portions 262. The number of anti-detachment portions 262 is multiple, and the multiple anti-detachment portions 262 are spaced apart and connected to the edge of the insulating body 261 so that an anti-detachment groove 2601 is formed between two adjacent anti-detachment portions 262. The insulating body 261 is attached to the side of the fourth active material layer 250 away from the current collector 210. The insulating body 261 is attached to the edge of the fourth active material layer 250 adjacent to the insulating region 212. The insulating body 261 is also attached to the edge of the first active material layer 220 adjacent to the insulating region 212. The insulating body 261 is also attached to the insulating region 212. Each anti-detachment portion 262 is attached to the side of the fourth active material layer 250 away from the current collector 210. In this embodiment, since there is an anti-detachment groove 2601 between two adjacent anti-detachment parts 262, each anti-detachment part 262 will not directly drive other anti-detachment parts 262 to detach when it detaches, thus avoiding the overall detachment of the insulation layer 260, improving the firmness of the insulation layer 260, and making the short-circuit protection effect of the insulation layer 260 better.

[0079] like Figure 3 and Figure 4As shown, each anti-detachment part 262 is further provided with multiple spaced fracture grooves 2621 to reduce the connection strength between each anti-detachment part 261 and the insulating body 261. In this embodiment, when the scraping force is large, due to the low connection strength between each anti-detachment part 262 and the insulating body 261, each anti-detachment part 262 will bend to the fracture groove 2621 and break, so as to avoid each anti-detachment part 262 causing other anti-detachment parts 262 to bend, thereby avoiding the problem of overall edge warping when the scraping force is large. This helps to improve the firmness of the insulating layer 260, thereby improving the short circuit protection effect of the insulating layer 260.

[0080] like Figure 4 and Figure 5 As shown, the insulating layer 260 further includes an embedded portion 263, and there are multiple embedded portions 263. Each embedded portion 263 is provided in a one-to-one correspondence with a multiple fracture groove 2621. Each embedded portion 263 is located in the corresponding fracture groove 2621 and connected to the anti-detachment portion 262. Each embedded portion 263 is embedded in the fourth active material layer 250, which improves the positional stability of each embedded portion 263. This helps to suppress the situation where the fracture point lifts up and causes the insulating layer 260 to lift up as a whole, thereby improving the positional stability of the insulating layer 260 and thus improving the short-circuit protection effect of the insulating layer 260.

[0081] Furthermore, the fourth active material layer 250 has multiple embedding slots, and the multiple embedding slots are respectively arranged in correspondence with multiple embedding parts 263. Each embedding part 263 is located in the corresponding embedding slot and connected to the fourth active material layer 250, so that each embedding part 263 is embedded in the fourth active material layer 250.

[0082] like Figure 2 and Figure 3 As shown, in one embodiment, the insulating body 261 includes a first connecting portion 2611, a second connecting portion 2612, and a third connecting portion 2613. The first connecting portion 2611 is connected to the insulating region 212, the second connecting portion 2612 is connected to the edge of the first active material layer 220 adjacent to the insulating region 212, the second connecting portion 2613 is also connected to the edge of the fourth active material layer 250 adjacent to the insulating region 212, and the third connecting portion 2613 is connected to the side of the fourth active material layer 250 opposite to the current collector 210. In this embodiment, the third connecting portion 2613 is connected to a portion of the side of the fourth active material layer 250 opposite to the current collector 210. The second connecting portion 2612 is perpendicular to the first connecting portion 2611, and the third connecting portion 2613 is perpendicular to the second connecting portion 2612, so that the insulating body 261 is tightly attached to the side of the fourth active material layer 260 away from the current collector 210, the edge of the fourth active material layer 260 adjacent to the insulating region 212, the edge of the first active material layer 220 adjacent to the insulating region 212, and the insulating region 212.

[0083] Compared with the prior art, the present invention has at least the following advantages:

[0084] 1. Since the insulating layer covers the boundary between the fourth active material layer and the insulating area, that is, the edge of the fourth active material layer adjacent to the insulating area is covered by the insulating layer, there is no exposed gap between the edge of the fourth active material layer and the insulating layer, which avoids the problem of short circuit caused by needle puncture and improves the safety performance of lithium battery.

[0085] 2. Since the insulating layer is coated or bonded to the fourth active material layer and the insulating area after the cold pressing operation, the problem of overvoltage of the positive electrode caused by the insulating layer is avoided, thus improving the performance of the lithium battery.

[0086] 3. Since the insulating layer can be coated or bonded after the electrode is cold-pressed, the connection quality of the insulating layer is not affected by the cold-pressing operation, thereby improving the connection quality of the insulating layer, which helps to improve the short-circuit protection effect of the insulating layer, and thus makes the lithium battery perform better.

[0087] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a positive electrode structure, characterized in that, The method comprises the following steps: coating a first active material on one side of a current collector to obtain a first active material layer; coating a second active material on the side of the current collector away from the first active material layer to obtain a second active material layer; coating a third active material on the side of the second active material layer away from the current collector to obtain a third active material layer; coating a fourth active material on the side of the first active material layer away from the current collector to obtain a fourth active material layer, thereby obtaining a multilayer coating structure; wherein one side of the current collector adjacent to the fourth active material layer is left with an insulating area; performing a cold pressing operation on the multilayer coating structure to obtain a multilayer compacted structure; performing an inorganic particle spraying operation on the side of the fourth active material layer away from the current collector, the edge of the first active material layer adjacent to the insulating area, the edge of the fourth active material layer adjacent to the insulating area, and the surface of the insulating area; coating or attaching an insulating layer on the fourth active material layer and the insulating area, so that the insulating layer covers the edge of the fourth active material layer adjacent to the insulating area, to obtain a positive electrode tab structure; performing a slotting operation on the edge of the insulating layer of the positive electrode tab structure, so that the edge of the insulating layer forms a plurality of spaced apart anti-dropping slots, and a plurality of spaced apart anti-dropping portions are formed on the edge of the insulating layer; performing an edge cutting operation on each anti-dropping portion, so that each anti-dropping portion forms a plurality of spaced apart fracture slots, and the insulating layer forms an embedded portion in the fracture slots; performing a pressing operation on each embedded portion to embed each embedded portion into the fourth active material layer; performing a filling operation on the gap between each embedded portion and the fourth active material layer.

2. The method of claim 1, wherein the method further comprises: The first active material, the second active material, the third active material, and the fourth active material are at least one of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxyphosphate, sodium vanadium oxyphosphate, lithium vanadate, lithium manganate, lithium nickelate, lithium nickel cobalt manganese oxide, lithium-rich manganese-based material, lithium nickel cobalt aluminum oxide, and lithium titanate.

3. The method of claim 2, wherein the method further comprises: The first active material, the second active material, the third active material, and the fourth active material each further comprise a bonding agent.

4. The method of claim 3, wherein the method further comprises: The bonding agent is at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and butadiene styrene rubber.

5. The method of claim 2, wherein the method further comprises: The first active material, the second active material, the third active material, and the fourth active material each further comprise a conductive agent.

6. The method of claim 5, wherein the method further comprises: The conductive agent is at least one of carbon nanotubes, conductive carbon black, acetylene black, graphene, ketchen black, and carbon fiber.

7. The method of claim 1, wherein the method further comprises: The insulating layer comprises at least one of inorganic particles and a polymer.

8. The method of claim 7, wherein the method further comprises: The inorganic particles are at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.

9. The method of claim 7, wherein the method further comprises: The polymer is at least one of a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride, a copolymer of hexafluoropropylene, polystyrene, polyphenylacetylene, polyvinyl sodium acetate, polyvinyl potassium acetate, polymethyl methacrylate, polyethylene, polypropylene, and polytetrafluoroethylene.

10. A positive electrode sheet structure characterized by comprising: The positive electrode tab structure is prepared by the method of any one of claims 1 to 9.

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