Pole piece and pole piece coating method

Abstract

The invention relates to the technical field of pole pieces, and provides a pole piece and a pole piece coating method, the pole piece comprises a foil material, a first conductive layer arranged on the foil material, a first insulating layer arranged on the foil material, a second insulating layer arranged on the foil material, and a second conductive layer arranged on the first conductive layer; the first conductive layer is located between the first insulating layer and the second insulating layer; the first conductive layer is in contact with the first insulating layer, and the first conductive layer is in contact with the second insulating layer; the first insulating layer and the second insulating layer are water-based insulating slurry layers; the second conductive layer is an oily conductive slurry layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of pole pieces, and more specifically, relates to a pole piece and a pole piece coating method. Background Art

[0002] New energy vehicles have shown explosive growth in recent years. As the most critical power source for power vehicles, the performance of batteries is crucial. Lithium iron phosphate has become the main material for power batteries due to its high safety and high cost performance. In order to solve the problem of battery safety, all battery manufacturers have invested heavily in research and development. It has become an industry consensus to coat insulating materials on both sides of the positive electrode coating area. The conventional method of coating insulating materials is to coat the slurry and insulating materials through the die head gasket at the same time. In order to ensure the thinning of the electrode coating area, the slurry and ceramic outlets need to be chamfered. Under this design, the wet slurry and wet ceramic are sprayed out from the gasket opening at the same time, which will produce impact and obvious virtual edges. The current level of virtual edges is generally around 0.8mm. The generation of virtual edges has a significant impact on the winding misalignment alignment. To improve the virtual edge of coating, the mainstream improvement direction is to develop new material systems, but it is extremely difficult and progress is slow. Another research and development direction is split coating, such as external dispensing solution, which supplies insulating glue through a single precision pump. The cost of this device is extremely high, and it can only be coated on low-speed production lines. The accuracy and thickness control of high-speed coating are poor, and ceramics are prone to wavy edges and cannot be promoted for mass production. In addition to safety performance, slurry batteries have many special requirements for pole pieces, such as primer coating before coating the pole piece with slurry to improve the conductivity of the pole piece. The common practice is to purchase a gravure machine for primer coating, which requires a lot of manpower and materials, pushing up the production cost of the battery cell. Under today's fierce market competition, it is urgent to find new process routes and equipment to save energy and reduce consumption. Summary of the invention

[0003] The object of the present invention is to provide a pole piece to solve the technical problem in the prior art that insulating materials and conductive materials are easily mixed to form virtual edges.

[0004] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: to provide a pole piece, including: a foil material, a first conductive layer arranged on the foil material, a first insulating layer arranged on the foil material, a second insulating layer arranged on the foil material, and a second conductive layer arranged on the first conductive layer; the first conductive layer is located between the first insulating layer and the second insulating layer; the first conductive layer is in contact with the first insulating layer, and the first conductive layer is in contact with the second insulating layer; the first insulating layer and the second insulating layer are both aqueous insulating slurry layers; the second conductive layer is an oily conductive slurry layer.

[0005] Furthermore, the second conductive layer and the first insulating layer are spaced apart; the second conductive layer and the second insulating layer are spaced apart.

[0006] Furthermore, the thickness of the first conductive layer is 1 μm to 5 μm.

[0007] Furthermore, the thickness of the first insulating layer is 1 μm to 5 μm; the thickness of the second insulating layer is 1 μm to 5 μm.

[0008] Furthermore, the insulating paste comprises: a filler and a binder, and the ratio of the filler to the binder is 0.8 to 1.2.

[0009] Furthermore, the binder includes at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and non-fluorine polymers.

[0010] Furthermore, the non-fluorine polymer is composed of any one or more of polyacrylic acid (PAA), polyurethane (PU), polyethylene (PE), polypropylene (PP), polyacrylonitrile, polyacrylate, epoxy resins, phenolic resins, phenolic resins modified by comonomers, polymethacrylic acid, ethylene ethyl acrylate copolymers, ethylene acrylate copolymers, polyamides and polyvinyl chloride, styrene-butadiene, polystyrene, and nitrile rubber.

[0011] Furthermore, the filler includes: one or more combinations of boehmite, aluminum oxide, aluminum oxide, calcium oxide, magnesium oxide, zirconium oxide, titanium dioxide, silicon dioxide, nitride, boride and carbide.

[0012] Furthermore, the particle size Dv50 of the filler is A, the specific surface area of ​​the filler is B; the molecular weight of the third binder is X ten thousand;

[0013] Among them, 0.04≤(A×B) / X≤0.32;

[0014] 0.5≤A≤1.2, 4≤B≤8, 10≤X≤100.

[0015] The present invention also provides a pole piece coating method, comprising:

[0016] S1: prepare foil;

[0017] S2: coating a first conductive layer on the foil, coating a first insulating layer on the foil, and coating a second insulating layer on the foil; the first conductive layer is located between the first insulating layer and the second insulating layer; the first conductive layer is in contact with the first insulating layer; the first insulating layer and the second insulating layer are both formed by coating insulating slurry, and the insulating slurry is water-based insulating slurry; the second conductive layer is formed by coating conductive slurry, and the conductive slurry is oil-based conductive slurry;

[0018] S3: coating a second conductive layer on the first conductive layer.

[0019] Furthermore, the solid content of the insulating slurry is 25% to 45%, and the viscosity of the insulating slurry is 100 cps to 1500 cps.

[0020] The electrode provided by the present invention has the beneficial effect that: compared with the prior art, the electrode provided by the present invention has a first conductive layer arranged on the foil, and a first insulating layer and a second insulating layer arranged on the foil; the first conductive layer is located between the first insulating layer and the second insulating layer; the second conductive layer is arranged on the first conductive layer. The first insulating layer and the second insulating layer are both aqueous insulating slurry layers, and the second conductive layer is an oily conductive slurry layer. The aqueous insulating slurry layer and the oily conductive slurry layer have poor blending properties during edge contact, thereby avoiding the phenomenon of mixing, and the boundary line of contact between the two is clear, thereby improving the problem of virtual edges; and the aqueous insulating slurry layer has low cost and good insulation effect. Furthermore, the first conductive layer can protect the surface of the foil, and improve the adhesion and conductivity of the second conductive layer, thereby preventing subsequent electrode pieces from losing powder. Since the first insulating layer and the second insulating layer are respectively located on both sides of the first conductive layer, the first insulating layer and the second insulating layer can be insulated from both sides of the first conductive layer respectively; the first conductive layer is in direct contact with the first insulating layer and the second insulating layer, that is, there is no gap between the first conductive layer and the first insulating layer and the second insulating layer. Such a design makes it more convenient to produce without special debugging and control, and is particularly suitable for continuous and large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of processing the first conductive layer, the first insulating layer, the second insulating layer and the second conductive layer provided in an embodiment of the present invention;

[0022] Figure 2 A three-dimensional schematic diagram of a pole piece coating device provided in an embodiment of the present invention;

[0023] Figure 3 for Figure 2 The enlarged schematic diagram at A in the middle;

[0024] Figure 4 An exploded schematic diagram of a pole piece coating device provided in an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of a coating cavity on a coating disc provided in an embodiment of the present invention;

[0026] Figure 6 A schematic diagram of a pole piece coating device provided in an embodiment of the present invention.

[0027] Among them, the reference numerals in the figure are:

[0028] 11-first conductive layer; 121-first insulating layer; 122-second insulating layer; 13-second conductive layer; 2-foil; 3-frame; 31-conveying channel; 4-first coating mechanism; 41-anilox coating roller; 411-first coating surface; 412-anilox holes; 42-first feeder; 43-first rotating shaft; 5-second coating mechanism; 51-coating disk; 511-second coating surface; 512-coating cavity; 5131-first concave groove; 5132-second concave groove; 52-second feeder; 53-second rotating shaft; 6-third coating mechanism; 71-first roller; 72-second roller; 73-third roller. DETAILED DESCRIPTION

[0029] It should be noted that the specific embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0030] It should be noted that, in the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B; "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Among them, A and B can be singular or plural respectively.

[0031] It should be noted that when an element is referred to as being "fixed on" or "set on" another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" or "connected to" another element, it may be directly connected to the other element or indirectly connected to the other element. When an element is referred to as being "fixed on" or "set on" another element, it may be directly on the other element or indirectly on the other element.

[0032] It should be noted that the directions or positional relationships indicated by terms such as “length”, “width”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0033] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0034] It should be noted that the term "plurality" means two or more than two, unless otherwise clearly and specifically defined.

[0035] Please also read Figure 1 , the pole piece provided by the present invention is now described. The pole piece includes: a foil 2, a first conductive layer 11 arranged on the foil 2, a first insulating layer 121 arranged on the foil 2, a second insulating layer 122 arranged on the foil 2, and a second conductive layer 13 arranged on the first conductive layer 11; the first conductive layer 11 is located between the first insulating layer 121 and the second insulating layer 122; the first conductive layer 11 is in contact with the first insulating layer 121, and the first conductive layer 11 is in contact with the second insulating layer 122. The first insulating layer 121 and the second insulating layer 122 are both aqueous insulating slurry layers; the second conductive layer 13 is an oily conductive slurry layer; it can be understood that the first insulating layer 121 and the second insulating layer 122 can be formed by coating insulating slurry, and the insulating slurry is aqueous insulating slurry; the second conductive layer 13 can be formed by coating conductive slurry, and the conductive slurry is oily conductive slurry.

[0036] In this way, the first conductive layer 11 is arranged on the foil 2, and the first insulating layer 121 and the second insulating layer 122 are arranged on the foil 2; the first conductive layer 11 is located between the first insulating layer 121 and the second insulating layer 122; the second conductive layer 13 is arranged on the first conductive layer 11. The first insulating layer 121 and the second insulating layer 122 are both aqueous insulating slurry layers, and the second conductive layer 13 is an oily conductive slurry layer. The aqueous insulating slurry layer and the oily conductive slurry layer have poor blending properties during edge contact, which avoids the phenomenon of mixing. The boundary line of contact between the two is clear, thereby improving the problem of virtual edges. In addition, the aqueous insulating slurry layer has low cost and good insulation effect. It can be understood that the second conductive layer 13 is located on the outside, and most of the virtual edges on the pole piece are caused by the mixing of the conductive layer and the insulating layer located on the outside. Therefore, it is only necessary to ensure that the conductive slurry used in the second conductive layer 13 is an oily conductive slurry, which can greatly improve the problem of virtual edges; of course, it is more preferred that the first conductive layer 11 is also an oily conductive slurry layer.

[0037] Furthermore, the first conductive layer 11 can protect the surface of the foil 2 and improve the adhesion and conductivity of the second conductive layer 13, thereby preventing the subsequent pole piece from powdering. Since the first insulating layer 121 and the second insulating layer 122 are respectively located on both sides of the first conductive layer 11, the first insulating layer 121 and the second insulating layer 122 can be insulated from both sides of the first conductive layer 11; the first conductive layer 11 is in direct contact with the first insulating layer 121 and the second insulating layer 122, that is, there is no gap between the first conductive layer 11 and the first insulating layer 121 and the second insulating layer 122. With this design, the first conductive layer 11 can completely cover the surface of the foil, improve the adhesion and conductivity of the second conductive layer 13, and prevent the subsequent pole piece from powdering; in addition, it is more convenient to produce without special debugging and control, and is particularly suitable for continuous and large-scale industrial production.

[0038] About "aqueous slurry": Aqueous slurry is a liquid prepared with water as the main solvent or dispersion medium, and is widely used in various coating and adhesive fields, including the manufacture of lithium batteries. About "oily slurry": Oily slurry is a liquid prepared with organic solvents as the main solvent or dispersion medium, and is widely used in various coating and adhesive fields, including the manufacture of lithium batteries.

[0039] In one embodiment, the thickness of the second conductive layer 13 is greater than the thickness of the first conductive layer 11. It can be understood that the first conductive layer 11 mainly plays a role in protecting the foil and improving the adhesion and conductivity of the second conductive layer 13, while the second conductive layer 13 mainly plays a conductive role.

[0040] For further information, see Figure 1 As a specific embodiment of the electrode provided by the present invention, the second conductive layer 13 is spaced apart from the first insulating layer 121; the second conductive layer 13 is spaced apart from the second insulating layer 122. In this way, it can be ensured that the second conductive layer 13 does not contact the first insulating layer 121 and the second insulating layer 122, thereby forming a virtual edge.

[0041] First, as mentioned above, the thickness of the second conductive layer 13 is greater than that of the first conductive layer 11, so the second conductive layer 13 is more likely to mix with the insulating layers on both sides and form virtual edges. Therefore, by spacing the second conductive layer 13 from the first insulating layer 121 and the second insulating layer 122, the generation of virtual edges can be better prevented; in addition, regarding the problem that controlling the gap size mentioned above will increase production difficulty and cost, it should be noted that the coating of the second conductive layer 13 is different from that of the first conductive layer 11. First, the gap between the second conductive layer 13 and the first insulating layer 121 and the second insulating layer 122 does not need to be small. Second, the bonding force between the second conductive layer 13 and the first conductive layer 11 is higher than the bonding force between the first conductive layer 11 and the foil. Therefore, the second conductive layer 13 can be formed faster when coated, and there is no need for complicated debugging. Of course, in other embodiments, in order to facilitate production, the second conductive layer 13 may be in contact with the first insulating layer 121 and the second insulating layer 122, that is, there is no gap between the second conductive layer 13 and the first insulating layer 121 and the second insulating layer 122. In other embodiments, the second conductive layer 13 only needs to be coated after the first insulating layer 121 and the second insulating layer 122 are coated, that is, the coating is performed in separate steps, so that the second conductive layer 13 does not directly impact the first insulating layer 121 and the second insulating layer 122, and the formation of virtual edges can be well avoided.

[0042] In addition, it should be noted that the inventors have found that by spacing the conductive layer (including the first conductive layer 11 and the second conductive layer 13) and the insulating layer (including the first insulating layer 121 and the second insulating layer 122), that is, there is a gap between the conductive layer (including the first conductive layer 11 and the second conductive layer 13) and the insulating layer (including the first insulating layer 121 and the second insulating layer 122), the virtual edge can be avoided to a certain extent. However, such a solution, firstly, controls the gap between the first conductive layer 11 and the first insulating layer 121 and the second insulating layer 122, which requires complex debugging and control, and secondly, the foil located at the gap is exposed, which affects the safety of the battery.

[0043] For further information, see Figure 1 As a specific embodiment of the pole piece provided by the present invention, the width of the first conductive layer 11 is: 300mm~1000mm. In this way, it is convenient for current to pass. Such a width helps to evenly distribute the current, reduce the risk of local overheating, and extend the service life of the battery. In addition, such a width can effectively reduce the internal resistance of the battery, thereby improving the overall energy density and output power of the battery. Through these optimizations, the performance of lithium batteries has been significantly improved, which can better meet the needs of modern electronic devices for energy-intensive and high-efficiency power supplies.

[0044] For further information, see Figure 1As a specific embodiment of the electrode provided by the present invention, the thickness of the first conductive layer 11 is: 1μm to 5μm. First, the thickness of the first conductive layer 11 is above 1μm, so as to ensure the adhesion and conductivity of the second conductive layer 13. It can be understood that if the thickness of the first conductive layer 11 is less than 1μm, the thickness is too small, the adhesion and conductivity of the second conductive layer 13 are poor, and the prepared electrode is prone to powdering; secondly, the thickness of the first conductive layer 11 is below 5μm, and the thickness is small, which can save costs on the basis of realizing its function of protecting the foil and improving the adhesion and conductivity of the second conductive layer 13; in addition, the thinner first conductive layer 11 can be better flattened, thereby forming a flat surface for the second conductive layer 13 to be coated.

[0045] For further information, see Figure 1 As a specific embodiment of the pole piece provided by the present invention, the thickness of the first insulating layer 121 is 1μm to 5μm; the thickness of the second insulating layer 122 is 1μm to 5μm. Firstly, the thickness of the first insulating layer 121 and the second insulating layer 122 is above 1μm, so as to ensure that they realize the insulation function. It can be understood that if the thickness of the first insulating layer 121 and the second insulating layer 122 is less than 1μm, the thickness is too small and cannot be effectively insulated, and the battery cell using the pole piece is prone to short circuit; secondly, the thickness of the first insulating layer 121 and the second insulating layer 122 is below 5μm, and the thickness is small, which can save costs on the basis of realizing its insulation function; in addition, the thinner first insulating layer 121 and the second insulating layer 122 can better ensure that there is no mixing, that is, avoid the generation of virtual edges.

[0046] It should be noted that when the thicknesses of the first conductive layer 11 , the first insulating layer 121 , and the second insulating layer 122 are all relatively small, the phenomenon of mixing between the first conductive layer 11 and the first insulating layer 121 , and the second insulating layer 122 can be better avoided.

[0047] In order to well illustrate the beneficial effects of controlling the thickness of the first conductive layer 11, the first insulating layer 121 and the second insulating layer 122, some experimental data are provided as follows for illustration, wherein the thickness of the first conductive layer 11 is h1, and the thickness of the first insulating layer 121 and the second insulating layer 122 are both h2, see the following table:

[0048]

[0049]

[0050] It can be clearly seen from Examples 1-3 that when the thickness of the first conductive layer 11, the first insulating layer 121 and the second insulating layer 122 are all 1μm to 5μm, no virtual edges are formed and the effect is better; it can be seen from Examples 4-7 that when the thickness of the first conductive layer 11, the first insulating layer 121 and the second insulating layer 122 exceeds 5μm, although virtual edges exist, they can still be controlled below 0.2mm.

[0051] Further, as a specific embodiment of the pole piece provided by the present invention, the insulating slurry includes: a filler and a binder, the ratio of the filler to the binder is 0.8 to 1.2, the solid content of the insulating slurry is 25% to 45%, and the viscosity of the insulating slurry is 100cps to 1500cps. In this way, the insulating slurry has a good curing effect, and can better ensure that the first insulating layer 121 and the second insulating layer 122 will not be mixed with the first conductive layer 11 and / or the second conductive layer, thereby avoiding the generation of virtual edges. The ratio between the filler and the third binder is controlled between 0.8 and 1.2. This precise ratio ensures the consistency of the material and the performance stability of the final product. The solid content of the insulating slurry is 25% to 45%, which means that the coating will retain a large amount of solid components after drying, providing a solid protective layer for the battery. A higher solid content helps to improve the mechanical strength and durability of the coating, ensuring that it can effectively resist external physical damage and chemical corrosion during battery operation. The viscosity of the insulation slurry ranges from 100cps to 1500cps. This viscosity range allows the slurry to have good fluidity during the coating process, facilitating uniform coating, while being viscous enough to prevent the coating from being too thin and ensure sufficient coverage thickness. Appropriate viscosity can also prevent the coating from sagging or dripping during the drying or curing process, thereby ensuring the uniformity and quality control of the coating.

[0052] Further, as a specific embodiment of the pole piece provided by the present invention, the binder includes: at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and a third non-fluorine polymer. In this way, the bonding performance is good. The binder provides excellent adhesion to the first insulating layer 121 and the second insulating layer 122. The selection of these binders ensures that the conductive material can be evenly and firmly attached to the surface of the foil 2, thereby optimizing the current transmission efficiency and the overall performance of the battery. Polytetrafluoroethylene and polyvinylidene fluoride can maintain their performance unchanged in various environments where the battery is running due to their excellent chemical stability and high temperature resistance, ensuring the safety and reliability of the battery. The application of non-fluorine polymers further increases the environmental protection characteristics of the product and reduces the potential impact on the environment. The comprehensive application of this binder not only improves the adhesion strength of the conductive layer, but also helps to prevent the peeling of the conductive layer during long-term use, maintaining the stability and long-term effectiveness of the battery performance.

[0053] Further, as a specific embodiment of the pole piece provided by the present invention, the non-fluorine polymer is composed of any one or more of polyacrylic acid (PAA), polyurethane (PU), polyethylene (PE), polypropylene (PP), polyacrylonitrile, polyacrylate, epoxy resin, phenolic resin, comonomer-modified phenolic resin, polymethacrylic acid, ethylene ethyl acrylate copolymer, ethylene acrylate copolymer, polyamide and polyvinyl chloride, styrene-butadiene, polystyrene, and nitrile rubber. In this way, polyacrylic acid (PAA): provides excellent adhesion and water solubility, is suitable for water-based coatings, is environmentally friendly and easy to use. Polyurethane (PU): has excellent elasticity and wear resistance, and is suitable for bearing mechanical stress and dynamic loads. Polyethylene (PE): has strong chemical stability and good electrical insulation properties, and is suitable for preventing current leakage. Polypropylene (PP): has good chemical corrosion resistance and thermal stability, and is used in applications that require resistance to high temperatures and chemical environments. Polyacrylonitrile: has high strength and chemical stability, and is often used in environments that require durability and stability. Polyacrylate: provides good transparency and adhesion, and is often used in interface materials that require clear vision. Epoxy resin: high thermal stability and mechanical strength, suitable for high temperature and high pressure environments. Phenolic resin: excellent high temperature resistance and chemical stability, suitable for high thermal stress environment. Comonomer modified phenolic resin: improves the performance of traditional phenolic resin, improves environmental resistance and mechanical strength. Polymethacrylic acid: excellent heat resistance and transparency, suitable for applications requiring optical properties. Ethylene ethyl acrylate copolymer: combines chemical resistance and elasticity, suitable for occasions requiring flexibility. Ethylene acrylate copolymer: provides high elasticity and adhesion, suitable for applications in dynamic environments. Polyamide: high strength and wear resistance, suitable for applications requiring wear resistance and load-bearing. Polyvinyl chloride (PVC): good electrical insulation, waterproof and moisture-proof, suitable for protective covering materials. Butadiene styrene: high elasticity and aging resistance, often used for external protective layers. Polystyrene: low cost, easy to shape, suitable for mass-produced consumer products. Nitrile rubber: strong oil resistance, suitable for sealing and protection in oil-proof environments.

[0054] Further, as a specific embodiment of the pole piece provided by the present invention, the filler includes: one or more combinations of boehmite, aluminum oxide, aluminum oxide, calcium oxide, magnesium oxide, zirconium oxide, titanium dioxide, silicon dioxide, nitride, boride and carbide. Thus, boehmite: a natural silicate mineral with good heat resistance and insulation, often used to enhance the thermal stability of materials. Aluminum oxide: has excellent electrical insulation and chemical stability, high temperature resistance, suitable for use as a high-performance insulating material. Aluminum oxide: high hardness, good thermal conductivity, often used to enhance wear resistance and thermal conductivity. Calcium oxide: has stable chemical properties, often used to adjust the pH value of the material and provide a certain mechanical strength. Magnesium oxide: high temperature resistance, often used to improve the heat resistance and insulation of composite materials. Zirconia: has a high melting point and good chemical stability, suitable for insulating materials in high temperature environments. Titanium dioxide: a white inorganic pigment with excellent hiding power and whitening effect, also used to improve UV resistance. Silicon dioxide: provides excellent mechanical strength and wear resistance, widely used to enhance the structural strength of composite materials. Nitrides: such as silicon nitride, have extremely high hardness and high temperature resistance, and are often used in applications requiring high wear resistance and high thermal stability. Borides: such as aluminum boride, have extremely high hardness and good thermal stability, suitable for high temperature applications and enhanced wear resistance of materials. Carbides: such as silicon carbide, have excellent thermal conductivity and wear resistance, and are often used as structural materials in harsh environments.

[0055] Further, as a specific embodiment of the pole piece provided by the present invention, the particle size Dv50 of the filler is A, and the specific surface area of ​​the filler is B; the molecular weight of the third binder is X ten thousand; wherein, 0.04≤(A×B) / X≤0.32; 0.5≤A≤1.2, 4≤B≤8, 10≤X≤100. In this way, the insulating slurry has good adhesion and insulation. In this way, first, the particle size (A) of the filler is in the range of 0.5 to 1.2 microns, and this particle size helps the filler to be evenly dispersed in the slurry, while ensuring sufficient surface contact area and enhancing the interfacial force between the binder and the filler. Smaller particle size is also conducive to the filler forming a dense network structure in the coating, thereby improving the overall mechanical strength and durability of the insulating layer. The specific surface area (B) is in the range of 4 to 8 square meters / gram, and a larger specific surface area means that the filler has more surface active sites, which can effectively promote chemical or physical bonding with the binder, thereby improving the adhesion of the slurry. In addition, the high specific surface area also helps to improve the anti-penetration ability of the insulating layer and prevent the intrusion of the electrolyte, thereby enhancing the safety of the battery. The molecular weight (X) of the binder is in the range of 100,000 to 1 million, which indicates that the binder has sufficient molecular weight to form a stable polymer network, which maintains the fluidity of the slurry while ensuring the structural integrity of the coating after curing. The appropriate molecular weight helps the binder to form a network structure with a high cross-linking density during the curing process, which not only enhances the mechanical properties of the insulating layer, but also improves its long-term stability and chemical corrosion resistance. Combined with the proportional relationship between the above parameters 0.04≤(A×B) / X≤0.32, this ratio range ensures that the filler and the binder achieve an optimized interaction balance, so that the insulating slurry has excellent insulation properties while maintaining good adhesion. This design approach makes full use of the physical and chemical properties of the material to meet the stringent requirements of high-performance lithium batteries.

[0056] In order to well illustrate the beneficial effects brought about when A, B, and X satisfy the above relationship, some experimental data are provided as follows, please refer to the following table:

[0057] (A×B) / X Is there a virtual edge? Example 8 0.02 Virtual edge 0.1mm Example 9 0.04 No virtual edges Example 10 0.12 No virtual edges Embodiment 11 0.18 No virtual edges Example 12 0.24 No virtual edges Embodiment 13 0.32 No virtual edges Embodiment 14 0.45 Virtual edge 0.1mm Embodiment 15 1 Virtual edge 0.2mm

[0058] It can be clearly seen from Examples 9-13 that when 0.04≤(A×B) / X≤0.32 is satisfied, no virtual edges are formed and the effect is better; it can be seen from Examples 8, 14, and 15 that when 0.04≤(A×B) / X≤0.32 is not satisfied, although virtual edges exist, they can still be controlled below 0.2 mm.

[0059] The present invention also provides a pole piece coating method, comprising:

[0060] S1: prepare foil 2;

[0061] S2: coating a first conductive layer 11 on the foil material 2, coating a first insulating layer 121 on the foil material 2, and coating a second insulating layer 122 on the foil material 2; the first conductive layer 11 is located between the first insulating layer 121 and the second insulating layer 122; the first conductive layer 11 is in contact with the first insulating layer 121; the first conductive layer 11 is in contact with the second insulating layer 122; the first insulating layer 121 and the second insulating layer 122 are both formed by coating insulating slurry, and the insulating slurry is water-based insulating slurry; the second conductive layer 13 is formed by coating conductive slurry, and the conductive slurry is oil-based conductive slurry;

[0062] S3 : coating the second conductive layer 13 on the first conductive layer 11 .

[0063] It can be understood that the electrode coating method can obtain the electrode described above, the first conductive layer 11 is coated on the foil 2, the first insulating layer 121 and the second insulating layer 122 are coated on the foil 2; the first conductive layer 11 is located between the first insulating layer 121 and the second insulating layer 122; the second conductive layer 13 is coated on the first conductive layer 11. The insulating slurry adopts water-based insulating slurry, and the conductive slurry adopts oil-based conductive slurry. The water-based insulating slurry and the oil-based conductive slurry have poor blending during the edge contact process, avoiding the phenomenon of mixing. The boundary line of the contact between the two is clear, thereby improving the problem of virtual edges. In addition, the water-based insulating slurry has low cost and good insulation effect. It can be understood that the second conductive layer 13 is located on the outside, and most of the virtual edges on the electrode are caused by the mixing of the conductive layer and the insulating layer located on the outside. Therefore, it is only necessary to ensure that the conductive paste used for the second conductive layer 13 is an oily conductive paste to greatly improve the problem of virtual edges; of course, it is more preferred that the conductive paste used to coat the first conductive layer 11 is also an oily conductive paste.

[0064] Furthermore, the first conductive layer 11 can protect the surface of the foil 2 and improve the adhesion and conductivity of the second conductive layer 13, thereby preventing the subsequent pole piece from powdering. Since the first insulating layer 121 and the second insulating layer 122 are respectively located on both sides of the first conductive layer 11, the first insulating layer 121 and the second insulating layer 122 can be insulated from both sides of the first conductive layer 11; the first conductive layer 11 is in direct contact with the first insulating layer 121 and the second insulating layer 122, that is, there is no gap between the first conductive layer 11 and the first insulating layer 121 and the second insulating layer 122. With this design, the first conductive layer 11 can completely cover the surface of the foil, improve the adhesion and conductivity of the second conductive layer 13, and prevent the subsequent pole piece from powdering; in addition, it is more convenient to produce without special debugging and control, and is particularly suitable for continuous and large-scale industrial production.

[0065] In one embodiment, the first conductive layer 11, the first insulating layer 121, and the second insulating layer 122 may be coated simultaneously, thereby improving the coating efficiency of the first conductive layer 11, the first insulating layer 121, and the second insulating layer 122.

[0066] In one embodiment, the first conductive layer 11, the first insulating layer 121, and the second insulating layer 122 are coated sequentially, so as to improve the independence of the first conductive layer 11, the first insulating layer 121, and the second insulating layer 122 from each other.

[0067] In some preferred embodiments, the first conductive layer 11 is coated first, and then the first insulating layer 121 and the second insulating layer are coated simultaneously, which ensures the independence of the first conductive layer 11, the first insulating layer 121, and the second insulating layer 122 with high coating efficiency.

[0068] See also Figures 2 to 6 In one embodiment, a pole piece coating device is provided, which is suitable for producing the pole piece mentioned above. The pole piece coating device includes: a conveying channel 31, a first coating mechanism 4, a second coating mechanism 5, and a third coating mechanism 6; the conveying channel 31 is used to convey the foil 2; the first coating mechanism 4 is used to coat the first conductive paste on the foil 2 to form the first conductive layer 11; the second coating mechanism 5 is used to coat the insulating paste on the foil 2 to form the first insulating layer 121 and the second insulating layer 122 respectively; the first conductive layer 11 is located between the first insulating layer 121 and the second insulating layer 122; the third coating mechanism 6 is used to coat the second conductive paste on the first conductive layer 11 to form the second conductive layer 13; wherein the first coating mechanism 4, the second coating mechanism 5, and the third coating mechanism 6 are arranged in sequence along the conveying channel 31. In this way, the foil 2 can be transported along the conveying channel 31; the first coating mechanism 4 can coat the first conductive paste on the foil 2 in the conveying channel 31, and the foil 2 coated with the first conductive paste can form a first conductive layer 11; the second coating mechanism 5 can coat the insulating paste on the foil 2 in the conveying channel 31, and the second coating mechanism 5 can form a first insulating layer 121 and a second insulating layer 122 respectively after coating the insulating paste on the foil 2; the third coating mechanism 6 can coat the second conductive paste on the first conductive layer 11 in the conveying channel 31 to form a second conductive layer 13.

[0069] In one embodiment, the delivery channel 31 can be any one of a space, a pipe, and a groove.

[0070] In one embodiment, the power for the foil 2 to move along the conveying channel 31 may come from a user or a motor.

[0071] In one embodiment, the electrode coating device further includes: a frame 3 ; a first coating mechanism 4 , a second coating mechanism 5 , and a third coating mechanism 6 all disposed on the frame 3 .

[0072] In one embodiment, the first coating mechanism 4 includes: a first rotating shaft 43, an anilox coating roller 41, and a first feeder 42 for supplying a first conductive paste; the first rotating shaft 43 is disposed in the anilox coating roller 41, and both ends extend out of the anilox coating roller 41 and are connected to the frame 3; the surface of the anilox coating roller 41 has a first coating surface 411 for contacting the foil 2; a plurality of anilox holes 412 are arranged on the surface of the first coating surface 411, and the first feeder 42 is respectively connected to the plurality of anilox holes 412. In this way, when the anilox coating roller 41 rotates, the first coating surface 411 of the anilox coating roller 41 contacts the foil 2 and the first conductive paste is coated on the surface of the foil 2.

[0073] In one embodiment, a plurality of mesh holes 412 are respectively formed into a plurality of mesh hole groups, and the mesh holes 412 in each mesh hole group are evenly distributed, so that a flat first conductive layer 11 can be obtained.

[0074] In one embodiment, the distance between adjacent mesh hole groups is greater than the distance between adjacent mesh holes 412 in each mesh hole group. In this way, the first conductive layer 11 can be coated on multiple pole pieces at the same time, thereby improving production efficiency.

[0075] In one embodiment, the second coating mechanism 5 includes: a second rotating shaft 53, a plurality of coating discs 51 and a second feeder 52 for supplying a second conductive paste; both ends of the second rotating shaft 53 are connected to the frame 3; the coating disc 51 is sleeved outside the second rotating shaft 53, and the plurality of coating discs 51 are arranged at intervals; the outer surface of the coating disc 51 has a second coating surface 511 for contacting the foil 2; a plurality of coating cavities 512 are arranged on the second coating surface 511, and the second feeder 52 is connected to each coating cavity 512. In this way, when the second coating surface 511 of the coating disc 51 contacts the electrode to be coated on the foil 2, the insulating paste in the coating cavity 512 can be coated to form an insulating layer (including a first insulating layer 121 and a second insulating layer 122). Through a plurality of insulating discs 51 arranged at intervals, the first insulating layer 121 and the second insulating layer 122 can be coated on both sides of the first conductive layer 11 at the same time. It can be understood that the insulating layer formed by coating with the same coating disc 51 is cut into two in the subsequent cutting process, namely, the first insulating layer 121 of one pole piece and the second insulating layer 122 of another pole piece.

[0076] In one embodiment, the plurality of coating discs 51 are all ceramic coating discs, which are more suitable for coating water-based insulating slurry.

[0077] In one embodiment, each coating disc 51 is detachably connected to the second rotating shaft 53. In this way, it is very convenient to install the coating disc 51 and to adjust the distance between the coating discs 51.

[0078] In one embodiment, for any coating disc 51: the coating disc 51 has a first blank area 5131 and a second blank area 5132, and the first blank area 5131 and the second blank area 5132 are arranged at intervals, and the second coating surface 512 is between the first blank area 5131 and the second blank area 5132; the first blank area 5131 and the second blank area 5132 extend along the circumferential direction of the edge of the coating disc 51. In this way, the first blank area 5131 and the second blank area 5132 can block the slurry.

[0079] In one embodiment, grooves are provided in both the first blank area 5131 and the second blank area 5132, so as to better block the slurry.

[0080] In one embodiment, the width of each coating disc 51 is 2 mm to 8 mm. The width of the insulating layer is controlled by determining the width of the coating disc 51 .

[0081] In one embodiment, the depth of each coating cavity 512 is 150 μm to 200 μm. The thickness of the insulating layer is controlled by determining the depth of the coating cavity 512 .

[0082] In one embodiment, the opening shape of each coating cavity 512 is a honeycomb shape, which is well suited for water-based insulating slurry and ensures the consistency of the thickness of the insulating layer.

[0083] In one embodiment, the third coating mechanism 6 includes: a coating die head disposed on the frame 3 .

[0084] In one embodiment, it also includes: a first roller 71, a second roller 72, and a third roller 73; the first roller 71, the second roller 72, and the third roller 73 are respectively arranged on the frame 3; a first gap for the foil 2 to pass through is formed between the first roller 71 and the first coating mechanism 4, a second gap for the foil 2 to pass through is formed between the second roller 72 and the second coating mechanism 5, and a third gap for the foil 2 to pass through is formed between the third roller 73 and the third coating mechanism 6.

[0085] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A pole piece, characterized in that: include: A foil material (2), a first conductive layer (11) arranged on the foil material (2), a first insulating layer (121) arranged on the foil material (2), a second insulating layer (122) arranged on the foil material (2), and a second conductive layer (13) arranged on the first conductive layer (11); the first conductive layer (11) is located between the first insulating layer (121) and the second insulating layer (122); the first conductive layer (11) is in contact with the first insulating layer (121), and the first conductive layer (11) is in contact with the second insulating layer (122); the first insulating layer (121) and the second insulating layer (122) are both aqueous insulating slurry layers; and the second conductive layer (13) is an oily conductive slurry layer.

2. The pole piece according to claim 1, characterized in that: The second conductive layer (13) and the first insulating layer (121) are arranged at intervals; and the second conductive layer (13) and the second insulating layer (122) are arranged at intervals.

3. The pole piece according to claim 1, characterized in that: The thickness of the first conductive layer (11) is 1 μm to 5 μm.

4. The pole piece according to claim 1, characterized in that: The thickness of the first insulating layer (121) is 1 μm to 5 μm; the thickness of the second insulating layer (122) is 1 μm to 5 μm.

5. The pole piece according to any one of claims 1 to 4, characterized in that: The aqueous insulating slurry layer comprises: a filler and a binder, and the ratio of the filler to the binder is 0.8 to 1.

2.

6. The pole piece according to claim 5, characterized in that: The binder includes at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and non-fluorine polymers.

7. The pole piece according to claim 6, characterized in that: The non-fluorine polymer is composed of any one or more of polyacrylic acid (PAA), polyurethane (PU), polyethylene (PE), polypropylene (PP), polyacrylonitrile, polyacrylate, epoxy resins, phenolic resins, phenolic resins modified by comonomers, polymethacrylic acid, ethylene ethyl acrylate copolymers, ethylene acrylate copolymers, polyamides and polyvinyl chloride, styrene-butadiene, polystyrene, and nitrile rubber.

8. The pole piece according to claim 7, characterized in that: The filler includes: one or more combinations of boehmite, aluminum oxide, aluminum oxide, calcium oxide, magnesium oxide, zirconium oxide, titanium dioxide, silicon dioxide, nitride, boride and carbide.

9. The pole piece according to claim 5, characterized in that: The particle size Dv50 of the filler is A, the specific surface area of ​​the filler is B; the molecular weight of the third binder is X ten thousand; Among them, 0.04≤(A×B) / X≤0.32; 0.5≤A≤1.2, 4≤B≤8, 10≤X≤100.

10. A pole piece coating method, characterized in that: include: S1: preparing foil (2); S2: coating a first conductive layer (11) on the foil (2), coating a first insulating layer (121) on the foil (2), and coating a second insulating layer (122) on the foil (2); the first conductive layer (11) is located between the first insulating layer (121) and the second insulating layer (122); the first conductive layer (11) is in contact with the first insulating layer (121); the first conductive layer (11) is in contact with the second insulating layer (122); the first insulating layer (121) and the second insulating layer (122) are both formed by coating insulating slurry, and the insulating slurry is water-based insulating slurry; the second conductive layer (13) is formed by coating conductive slurry, and the conductive slurry is oil-based conductive slurry; S3: coating a second conductive layer (13) on the first conductive layer (11).

11. The coating method according to claim 10, characterized in that The solid content of the insulating slurry is 25% to 45%, and the viscosity of the insulating slurry is 100 cps to 1500 cps.

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