Electrode sheet and preparation method therefor, battery cell, battery, and electric device

Abstract

An electrode sheet and a preparation method therefor, a battery cell, a battery, and an electric device, relating to the technical field of batteries. The electrode sheet comprises a current collector and a first insulating layer. The current collector comprises a main body portion and a tab; the tab extends from a first end of the main body portion; the first end is the end of the main body portion in a first direction; the tab comprises a first portion and a second portion; the first portion is closer to the main body portion than the second portion; the first insulating layer is arranged on the surfaces of two sides of the first portion; and the ratio L of the thickness of the first insulating layer to the thickness of the first portion satisfies that L≤1.3.

Description

Pole piece and preparation method thereof, battery cell, battery, and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to patent application 202310906054.3, filed on July 24, 2023, entitled “Pole piece and preparation method thereof, battery cell, battery, and electrical device,” and the entire contents of that application are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a pole piece and a preparation method thereof, a battery cell, a battery, and an electrical device. Background Art

[0004] With the increasing severity of environmental pollution, the new energy industry has attracted more and more attention. In the new energy industry, battery technology is an important factor in its development.

[0005] The development of battery technology requires consideration of multiple design factors, such as energy density, cycle life, and reliability. The design of the pole piece in a battery cell is crucial to its reliability. Therefore, how to provide a pole piece to improve the reliability of the battery cell is a technical problem that needs to be solved urgently.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its purpose is to provide a pole piece to improve the reliability of a battery cell.

[0008] In order to achieve the above-mentioned objectives, the present application provides a pole piece and a preparation method thereof, a battery cell, a battery, and an electrical device.

[0009] In a first aspect, a pole piece is provided, comprising a current collector and a first insulating layer, wherein the current collector comprises a main body and a pole tab, the pole tab extending from a first end of the main body, the first end being an end of the main body along the first direction, the pole tab comprising a first part and a second part, the first part being close to the main body relative to the second part, the first insulating layer being provided on surfaces on both sides of the first part, and the ratio L of the thickness of the first insulating layer to the thickness of the first part satisfies: L≤1.3.

[0010] An embodiment of the present application provides a pole piece, which includes a current collector and a first insulating layer. The current collector includes a main body and a pole tab, the pole tab extending from a first end of the main body, and the first end is an end of the main body along a first direction. The pole tab includes a first part and a second part, the first part is closer to the main body relative to the second part, and a first insulating layer is provided on the surface of both sides of the first part, so that the risk of the first part overlapping with the electrode of opposite polarity can be reduced. The ratio L of the thickness of the first insulating layer to the thickness of the first part satisfies: L≤1.3. In this way, the first insulating layer has a smaller thickness, and the total thickness of the first insulating layer and the first part is smaller, which facilitates bending the pole tab. In this way, the risk of short circuit and the like caused by the electrode assembly inserted into the battery cell after the pole tab is bent can be reduced, which is conducive to improving the reliability of the battery cell.

[0011] In one possible implementation, the ratio L of the thickness of the first insulating layer to the thickness of the first portion satisfies: L ≤ 1. Thus, the first insulating layer has a smaller thickness, which helps further reduce the risk of short circuits and other risks caused by the electrode assembly being partially inserted into the battery cell after the tab is bent.

[0012] In one possible implementation, L satisfies the following: 1 / 30 ≤ L ≤ 1. This provides the first insulating layer with an appropriate thickness, facilitating its fabrication. Furthermore, if the first insulating layer includes a thermoplastic polymer, L is greater than or equal to 1 / 30, indicating a relatively high concentration of the thermoplastic polymer in the first insulating layer. This allows a suitable amount of the thermoplastic polymer to melt and flow to the end face, thereby forming a relatively uniform and dense second insulating layer at the end face.

[0013] In one possible implementation, L satisfies: 4 / 13≤L≤6 / 13. This facilitates the preparation of the first insulating layer and further reduces the risk of bending the tab before inserting it into the electrode assembly.

[0014] In one possible implementation, the thickness d1 of the first insulating layer satisfies: d1 ≤ 10 μm. Thus, the first insulating layer is relatively thin, facilitating bending of the first portion of the tab. In a battery cell including such a pole piece, the risk of short circuits caused by inserting the bent tab into the electrode assembly of the battery cell can be reduced, thereby improving the reliability of the battery cell.

[0015] In one possible implementation, d1 satisfies the following: 0.5 μm ≤ d1 ≤ 10 μm. When the thickness d1 of the first insulating layer is not less than 0.5 μm, this helps reduce the difficulty of preparing the first insulating layer. When the thickness d1 of the first insulating layer is not more than 10 μm, the first insulating layer has a smaller thickness, which can further reduce the difficulty of bending the tab.

[0016] In one possible implementation, d1 satisfies the following: 4μm≤d1≤6μm. When the thickness d1 of the first insulating layer is not less than 4μm, this further reduces the difficulty of manufacturing the first insulating layer. When the thickness d1 of the first insulating layer is not more than 6μm, the first insulating layer has a smaller thickness, which further reduces the difficulty of bending the tab.

[0017] In one possible implementation, the first insulating layer on both sides of the first portion has the same thickness. The two insulating layers on both sides have the same thickness, so that both sides of the first portion are subjected to a relatively uniform force and the preparation of the first insulating layer is also facilitated.

[0018] In one possible implementation, the main body includes a coating region and a transition region, the transition region being disposed between the coating region and the tab, and the first insulating layer being disposed on both sides of the transition region. Providing the first insulating layer on the surface of the transition region helps reduce the risk of short circuits and other issues caused by the transition region overlapping with electrodes of opposite polarity.

[0019] In one possible implementation, the electrode further includes an active material layer disposed on at least one side of the coated area. This active material layer is located on at least one side of the coated area, preventing the active material layer from being cut during cutting, thereby reducing the risk of the active material layer falling off. Furthermore, the provision of the active material layer allows for charge and discharge operations in the battery cell, facilitating its normal operation.

[0020] In a possible implementation manner, the first insulating layer includes a thermoplastic polymer.

[0021] In the above technical solution, during the process of cutting the current collector to prepare the tabs, the thermoplastic polymer in the first insulating layer changes from a solid state to a fluid state, and then flows to the exposed end face of the current collector produced by cutting. The fluid thermoplastic polymer solidifies after cooling, and can cover the burrs and exposed end faces produced by cutting, thereby reducing the risk of burrs or exposed end faces overlapping with electrodes of opposite polarity, which is conducive to further improving the reliability of the battery cell.

[0022] In one possible implementation, the maximum particle size D of the thermoplastic polymer is 1 Max satisfied: D 1 max≤10μm; optionally, D 1 Max satisfied: D 1 In this way, the risk of scratches during the preparation of the first insulating layer due to the large maximum particle size of the thermoplastic polymer can be reduced, and it is also beneficial to obtain a first insulating layer with a suitable thickness, thereby facilitating the preparation of the first insulating layer.

[0023] In one possible implementation, the first insulating layer further includes a binder. By providing the binder, the thermoplastic polymer can be bonded to the current collector, thereby reducing the risk of the thermoplastic polymer falling off from the current collector. Optionally, based on the total mass of the first insulating layer, the mass content A of the thermoplastic polymer satisfies: 40wt% ≤ A ≤ 80wt%, and the mass content B of the binder satisfies: 20wt% ≤ B ≤ 40wt%. In this way, the thermoplastic polymer and the binder have a suitable mass ratio. On the one hand, the binder has a suitable mass content, and the first insulating layer will not fall off from the current collector; on the other hand, the thermoplastic polymer has a suitable mass content, which facilitates the formation of a uniform and dense second insulating layer on the exposed end surface after cutting.

[0024] In one possible implementation, the first insulating layer further includes inorganic particles; optionally, the inorganic particles include insulating inorganic particles; optionally, the insulating inorganic particles include at least one of boehmite and alumina. By providing the inorganic particles, the surface tension of the insulating slurry can be reduced when the thickness of the first insulating layer is small, thereby reducing the risk of current collector exposure. The insulating inorganic particles are non-conductive, so that the first insulating layer has good insulation. Boehmite and alumina have good heat resistance and insulation. By selecting boehmite or alumina as insulating inorganic particles and adding them to the first insulating layer, the first insulating layer has good heat resistance and insulation.

[0025] In one possible implementation, based on the total mass of the first insulating layer, the mass content C of the inorganic particles satisfies the following: 0 < C ≤ 40 wt %; alternatively, C satisfies the following: 30 wt % ≤ C ≤ 40 wt %. Properly setting the mass content of the inorganic particles helps reduce the surface tension of the insulating slurry, thereby reducing the risk of current collector exposure.

[0026] In a possible implementation, the maximum particle size D of the inorganic particles is 2 Max satisfied: D 2 max≤10μm; optionally, D 2 Max satisfied: D 2 In this way, the inorganic particles have a suitable particle size, which can reduce the risk of scratches during the preparation of the first insulating layer and is also conducive to obtaining a first insulating layer with a suitable thickness, thereby facilitating the preparation of the first insulating layer.

[0027] In one possible implementation, the volume particle size distribution Dv50 of the inorganic particles satisfies the following: 0.5 μm ≤ Dv50 ≤ 6 μm; alternatively, the volume particle size distribution Dv50 of the inorganic particles satisfies the following: 0.5 μm ≤ Dv50 ≤ 2 μm. Thus, during the preparation of the first insulating layer, the slurry for the first insulating layer has a suitable viscosity, facilitating coating of the first insulating layer; and the slurry for the first insulating layer has a relatively suitable solids content, facilitating drying of the first insulating layer.

[0028] In one possible implementation, the melting point of the thermoplastic polymer is 100°C to 200°C; in the above technical solution, the thermoplastic polymer has a suitable melting point. During the process of cutting the current collector provided with the first insulating layer, under the action of the heat generated by the cutting, the thermoplastic polymer changes from a solid state to a fluid state. The fluid thermoplastic polymer can flow to the end face of the current collector exposed after cutting and the burrs generated by the cutting, thereby facilitating the preparation of the second insulating layer.

[0029] In a possible implementation, the melting point of the thermoplastic polymer is 100° C. to 130° C. In this way, the second insulating layer can be prepared at a relatively low temperature.

[0030] In one possible implementation, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate, and their modified polymers. Optionally, the polyolefin includes polyethylene wax. Using these thermoplastic polymers facilitates forming a uniform and dense coating on the exposed end faces and burrs of the cut current collector.

[0031] In one possible implementation, the binder includes at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, and sodium alginate. These binders exhibit excellent adhesive properties, facilitating bonding of the thermoplastic polymer to the surface of the current collector. Optionally, the binder includes polyacrylonitrile, which exhibits excellent leveling properties, facilitating uniform coating of the first insulating layer on the surface of the current collector.

[0032] In one possible implementation, the bonding force F between the first insulating layer and the current collector satisfies the following conditions: 20 N / m ≤ F ≤ 100 N / m; alternatively, F satisfies the following conditions: 60 N / m ≤ F ≤ 90 N / m. This ensures a stronger bond between the first insulating layer and the current collector, reducing the risk of the first insulating layer falling off the current collector.

[0033] In one possible implementation, along the first direction, the ratio of the dimension k1 of the first insulating layer to the sum of the dimensions k2 of the first insulating layer and the second portion satisfies the following: 0.3 ≤ k1:k2 ≤ 0.5. When k1:k2 is not less than 0.3, the risk of a short circuit caused by the first portion overlapping an electrode of opposite polarity is reduced. When k1:k2 is not more than 0.5, the connection between the second portion of the tab and the end cap assembly of the battery cell is facilitated.

[0034] In one possible implementation, the electrode piece further includes a second insulating layer, which is disposed on the first end surface, the first end surface being the end surface of the main body at the first end. In this way, the second insulating layer can cover the first end surface, reducing the risk of the first end surface being exposed, thereby reducing the risk of short circuits caused by the first end surface overlapping with an electrode of opposite polarity. Furthermore, the second insulating layer can also cover burrs generated during the cutting process, reducing the risk of burrs overlapping with electrodes of opposite polarity.

[0035] In one possible implementation, the thickness d2 of the second insulating layer is 10 nm to 400 nm. Thus, the second insulating layer can effectively cover the burrs and the exposed first end surface while maintaining a relatively small thickness. Optionally, the thickness d2 of the second insulating layer is 100 nm to 200 nm. This further improves the covering effect on the burrs and the first end surface.

[0036] In one possible implementation, the resistance R of the second insulating layer satisfies: R ≥ 1Ω; optionally, R satisfies: 50Ω ≤ R ≤ 500Ω. The resistance of the second insulating layer satisfies the above condition, thereby reducing the risk of short circuiting the battery cell due to the end surface overlapping with an electrode of opposite polarity.

[0037] In one possible implementation, the second insulating layer is disposed on the first end surface and the second end surface. The second end surface is the end surface of the first portion along a second direction, which is different from the first direction. Optionally, the second direction is perpendicular to the first direction. In this way, the second insulating layer can cover the second end surface exposed by cutting, reducing the risk of the second end surface contacting an electrode of opposite polarity.

[0038] In a possible implementation, the material of the second insulating layer is the same as the material of the thermoplastic polymer in the first insulating layer. This helps to simplify the preparation steps of the pole piece and speed up the production process.

[0039] In one possible implementation, the thermoplastic polymer in the second insulating layer is in film form. Thus, the first insulating layer is formed by melting and solidifying the thermoplastic polymer in the second insulating layer. This simplifies the electrode sheet preparation process, allowing the first insulating layer to be formed simultaneously with cutting.

[0040] In a possible implementation, the number of layers of the tabs is greater than or equal to 50; optionally, the thickness d3 of the first portion of each layer of the tabs satisfies: 10 μm≤d3≤15 μm.

[0041] In one possible implementation, the electrode sheet comprises a positive electrode sheet; optionally, the current collector comprises aluminum foil. This helps reduce the risk of overlapping positive and negative electrode sheets, thereby improving the reliability of the battery cell. It also helps reduce the risk of overlapping lithium dendrites formed by the positive and negative electrode sheets. The current collector comprising aluminum foil has a relatively simple structure, which simplifies the current collector preparation process.

[0042] In one possible implementation, the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes at least one of a lithium transition metal oxide and an olivine structure lithium-containing phosphate; optionally, the olivine structure lithium-containing phosphate includes lithium iron phosphate; optionally, the lithium transition metal oxide includes: LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0043] In one possible implementation, the current collector comprises a metal foil or a composite current collector; optionally, the metal foil comprises aluminum foil or copper foil; optionally, the composite current collector comprises: a polymer base layer and a metal layer located on at least one surface of the polymer base layer; optionally, the current collector comprises aluminum foil. This facilitates selection of an appropriate current collector based on actual needs.

[0044] In a second aspect, a method for preparing a pole piece is provided, comprising: coating an insulating slurry on a first region of a current collector to form a first insulating layer in the first region, wherein a ratio L of a thickness d1 of the first insulating layer to a thickness of the first portion satisfies: L≤1.3; and cutting the current collector provided with the first insulating layer along a cutting line, wherein at least part of the cutting line is provided in the first region.

[0045] In the above technical solution, the thickness of the first insulating layer is relatively small, so that the portion of the pole ear produced after cutting the current collector and provided with the first insulating layer has a relatively small thickness, thereby reducing the difficulty of bending the pole ear, and can reduce the risk of short circuit and self-discharge caused by the electrode assembly inserted into the battery cell after the pole ear is bent, which is beneficial to improving the reliability of the battery cell.

[0046] In a possible implementation, L satisfies: L≤1; optionally, L satisfies: 1 / 30≤L≤1; optionally, 4 / 13≤L≤6 / 13.

[0047] In one possible implementation, the thickness d1 of the first insulating layer satisfies: d1 ≤ 10 μm; alternatively, d1 satisfies: 0.5 μm ≤ d1 ≤ 10 μm; alternatively, d1 satisfies: 4 μm ≤ d1 ≤ 6 μm. This reduces the difficulty of preparing the first insulating layer and further reduces the difficulty of bending the tab.

[0048] In one possible implementation, the insulating paste includes a thermoplastic polymer emulsion and a binder. Optionally, based on the total mass of the insulating paste, the mass content A of the thermoplastic polymer in the thermoplastic polymer emulsion satisfies the following: 40 wt% ≤ A ≤ 80 wt%, and the mass content B of the binder satisfies the following: 20 wt% ≤ B ≤ 40 wt%. Properly setting the mass content of the thermoplastic polymer facilitates the formation of a uniform and dense second insulating layer on the exposed cross-section of the current collector produced by cutting; and properly setting the mass content of the binder facilitates the reduction of the risk of the first insulating layer detaching from the current collector.

[0049] In one possible implementation, the maximum particle size D of the thermoplastic polymer is 1 Max satisfied: D 1 max≤10μm; optionally, D 1 Max satisfied: D 1 In this way, the risk of scratches during the preparation of the first insulating layer due to the large maximum particle size of the thermoplastic polymer can be reduced, thereby facilitating the preparation of the first insulating layer.

[0050] In one possible implementation, the volume particle size distribution Dv50 of the inorganic particles satisfies the following: 0.5 μm ≤ Dv50 ≤ 6 μm; alternatively, the volume particle size distribution Dv50 of the inorganic particles satisfies the following: 0.5 μm ≤ Dv50 ≤ 2 μm. Thus, during the preparation of the first insulating layer, the slurry of the first insulating layer has a suitable viscosity to facilitate coating of the first insulating layer; and the slurry of the first insulating layer has a relatively suitable solids content to facilitate drying of the first insulating layer.

[0051] In one possible implementation, the insulating slurry further includes inorganic particles. Adding the inorganic particles to the insulating slurry can reduce the surface tension of the slurry during coating, thereby reducing the risk of cracking the slurry and exposing the current collector when the slurry is applied to a relatively thin thickness. Optionally, the inorganic particles include insulating inorganic particles; optionally, the insulating inorganic particles include at least one of boehmite and alumina.

[0052] In one possible implementation, based on the total mass of the insulating slurry, the mass content C of the insulating inorganic particles in the insulating slurry satisfies the following conditions: 0 < C ≤ 40 wt %; alternatively, C satisfies the following conditions: 30 wt % ≤ B ≤ 40 wt %. Properly setting the mass content of the insulating inorganic particles can help reduce the risk of surface exposure of the current collector.

[0053] In a possible implementation, the maximum particle size D of the inorganic particles is 2 Max satisfied: D 2 max≤10μm; optionally, D 2 Max satisfied: D 2 max≤6μm.

[0054] In a possible implementation, the solid content E of the thermoplastic polymer emulsion satisfies: 30 wt% ≤ E ≤ 50 wt%, which facilitates the preparation of the thermoplastic polymer emulsion.

[0055] In a possible implementation, the melting point T of the thermoplastic polymer in the thermoplastic polymer emulsion is 100°C to 200°C; optionally, the melting point T is 100°C to 130°C.

[0056] In one possible implementation, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate, and their respective modified polymers; optionally, the polyolefin includes polyethylene wax.

[0057] In the above technical solution, the thermoplastic polymer has a suitable melting point. During the cutting process of the current collector provided with the first insulating layer, the heat generated by the cutting causes the thermoplastic polymer to change from a solid state to a fluid state. The fluid thermoplastic polymer can flow to the exposed end surfaces of the cut current collector and to the burrs generated by the cutting, thereby facilitating the preparation of the second insulating layer. The use of this thermoplastic polymer facilitates the formation of a uniform and dense coating on the exposed end surfaces and burrs of the cut current collector.

[0058] In one possible implementation, the binder includes at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, and sodium alginate. These binders have excellent adhesive properties, facilitating bonding of the thermoplastic polymer to the surface of the current collector.

[0059] In one possible implementation, coating the insulating slurry on the first region of the current collector to form the first insulating layer in the first region includes coating the insulating slurry on the first region of the current collector by gravure coating to form the first insulating layer in the first region. Gravure coating facilitates preparation of a first insulating layer with a relatively small thickness.

[0060] In one possible implementation, the method further includes: coating the first region of the current collector with an insulating slurry to form a first insulating layer in the first region, and then coating the second region of the current collector with an active material to form an active material layer in the second region. This can reduce the impact of the thicker active material layer on the preparation of the first insulating layer, facilitating the preparation of a thinner first insulating layer by gravure coating.

[0061] In a possible implementation, cutting the current collector provided with the first insulating layer along a cutting line includes: controlling a laser processing tool to cut the current collector provided with the first insulating layer along the cutting line.

[0062] In the above technical solution, the current collector is cut by laser, which can generate more heat during the cutting process, which is conducive to the thermoplastic polymer in the first insulating layer becoming fluid and flowing to the end surface, thereby facilitating the formation of the second insulating layer.

[0063] In a third aspect, a battery cell is provided, comprising the electrode according to the first aspect and any possible implementation thereof, and / or the electrode prepared by the method according to the second aspect and any possible implementation thereof.

[0064] In a fourth aspect, a battery is provided, comprising the battery cell described in the third aspect.

[0065] In a fifth aspect, an electrical device is provided, comprising the battery described in the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0067] FIG1 is a schematic diagram of a pole piece before processing a pole lug according to an embodiment of the present application;

[0068] FIG2 is a schematic diagram of a pole piece according to an embodiment of the present application;

[0069] FIG3 is a cross-sectional view along the AA direction in FIG2 ;

[0070] FIG4 is a cross-sectional view along the BB direction in FIG2 ;

[0071] FIG5 is a schematic diagram of a method for preparing a pole piece according to an embodiment of the present application;

[0072] FIG6 is a schematic diagram of a current collector according to an embodiment of the present application;

[0073] FIG7 is a schematic diagram of a current collector coated with a first insulating layer according to an embodiment of the present application;

[0074] FIG8 is a schematic diagram of a current collector showing a cutting line according to an embodiment of the present application;

[0075] FIG9 is a schematic diagram of a current collector coated with an active material layer according to an embodiment of the present application;

[0076] FIG10 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0077] FIG11 is a schematic diagram of a battery according to an embodiment of the present application;

[0078] FIG12 is a schematic diagram of an electrical device according to an embodiment of the present application.

[0079] Figure markings: 1: pole piece; 124: cutting line; 10: current collector; 11: active material layer; 121: first insulating layer; 1211: first sub-portion; 1212: second sub-portion; 122: second insulating layer; 101: main body; 102: pole ear; 1021: first portion; 1022: second portion; 1011: coating area; 1012: transition area; 1011a: first end face; 1222a: second end face. DETAILED DESCRIPTION

[0080] The embodiments of the electrode and its preparation method, battery cell, battery, and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0081] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0082] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0083] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0084] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0085] The development of battery technology must consider many design factors at the same time, such as energy density, cycle life, discharge capacity, charge and discharge rate, reliability, etc. Energy density, as an important performance, is crucial for battery cells. High-capacity battery cells usually have higher energy density, and high-capacity battery cells require more pole pieces. In the process of preparing battery cells, it is necessary to wind or stack multiple layers of pole pieces (including positive pole pieces and negative pole pieces) and isolation films into an electrode assembly, and then weld and bend the pole pieces' tabs to save the space occupied by the tabs, thereby increasing the energy density of the battery cells. The pole piece includes a current collector and an active material layer and an insulating layer coated on different areas of the current collector. After the corresponding active material layer and insulating layer are coated on the current collector, the current collector coated with the active material layer and the insulating layer needs to be cut to cut out the pole pieces. After the cutting is completed, an insulating layer is set on part of the pole piece. However, the thickness of the insulating layer on the tab is relatively large. When there are many layers of tabs, the thickness of the insulating layer on the tab is too thick, which makes it difficult to bend the tab. As a result, part of the tab will be inserted into the electrode assembly (for example, the non-tab part of the electrode sheet in the electrode assembly) after bending, causing short circuits and other phenomena, which is not conducive to improving the reliability of the battery cell.

[0086] In view of this, the present application provides a pole piece, which includes a current collector and a first insulating layer. The first insulating layer is provided on a portion of the surface of the current collector's tab. The ratio L of the thickness of the first insulating layer to the thickness of the current collector (the portion of the tab provided with the first insulating layer) satisfies: L ≤ 1.3. This reduces the thickness of the first insulating layer, easing the difficulty of bending the tab, thereby reducing the risk of short circuits caused by the tab being inserted into the electrode assembly, and thereby improving the reliability of the battery cell.

[0087] [Pole piece]

[0088] Figure 1 is a schematic diagram of a pole piece before processing the pole lug according to an embodiment of the present application, Figure 2 is a schematic diagram of a pole piece according to an embodiment of the present application, Figure 3 is a cross-sectional view along the AA direction in Figure 2, and Figure 4 is a cross-sectional view along the BB direction in Figure 2.

[0089] As shown in Figures 1 and 2, Figure 1 is a schematic diagram of the electrode before the tab is processed, and Figure 2 is a schematic diagram of the electrode after the tab is processed. As shown in Figure 1, the black dotted line is the cutting line 124 for cutting the tab. After cutting along the cutting line 124, the electrode 1 shown in Figure 2 is obtained.

[0090] 1 to 4 , the electrode 1 includes a current collector 10 and a first insulating layer 121 .

[0091] The current collector 10 includes a main body 101 and a tab 102 . The tab 102 extends from a first end of the main body 101 . The first end is one end of the main body 101 along a first direction.

[0092] The first direction is parallel to the plane where the current collector 10 is located, and the first direction is the direction in which the tab 102 protrudes relative to the main body 101. For example, the first direction is the y direction in FIG2.

[0093] The tab 102 includes a first portion 1021 and a second portion 1022 . The first portion 1021 is closer to the main body 101 than the second portion 1022 . A first insulating layer 121 is provided on both sides of the first portion 1021 .

[0094] The first portion 1021 is connected to the second portion 1022 , and the second portion 1022 is not provided with the first insulating layer 121 , that is, the second portion 1022 is exposed.

[0095] The surfaces on both sides of the current collector 10 refer to two surfaces that are opposite to each other along the thickness direction of the current collector 10. The surfaces on both sides of the first portion 1021 are provided with the first insulating layer 121, that is, the first insulating layer 121 is provided on both opposite surfaces of the first portion 1021 of the tab 102 along the thickness direction.

[0096] A ratio L of the thickness d1 of the first insulating layer 121 to the thickness d3 of the first portion 1021 satisfies: L≤1.3.

[0097] L can be 1.3, 1.29, 1, 0.8, 0.6, 0.3, 0.1 or any value within the above range.

[0098] The thickness d3 of the first portion 1021 may also be referred to as the thickness of the current collector 10 .

[0099] The thickness d1 of the first insulating layer 121 is the thickness of the first insulating layer 121 on one side of the first portion 1021. The total thickness of the first insulating layer is the sum of the thicknesses of the first insulating layer 121 on both sides. For example, the thicknesses of the first insulating layer 121 on both sides of the first portion 1021 can be the same or different.

[0100] The thickness d1 of the first insulating layer 121 may refer to the average thickness of the first insulating layer 121 on one side of the first portion 1021. For example, the average thickness is the average of the maximum and minimum dimensions of the first insulating layer 121 in the thickness direction. Similarly, the thickness d3 of the first portion 1021 refers to the average thickness of the first portion 1021.

[0101] When L does not exceed 1.3, the first insulating layer 121 has a relatively small thickness, and the total thickness of the first insulating layer 121 and the first portion 1021 is also relatively small. In this way, when the number of layers of the tab 102 is large, the difficulty of bending the tab 102 can be reduced, thereby reducing the risk of the bent tab 102 being inserted into the electrode assembly, and further reducing the risk of a short circuit caused by the insertion of the tab into the electrode assembly.

[0102] The present embodiment provides a pole piece 1, comprising a current collector 10 and a first insulating layer 121. The current collector 10 comprises a main body 101 and a tab 102. The tab 102 extends from a first end of the main body 101, where the first end is one end of the main body 101 along a first direction. The tab 102 comprises a first portion 1021 and a second portion 1022. The first portion 1021 is closer to the main body 101 than the second portion 1022. The first insulating layer 121 is provided on both sides of the first portion 101 to reduce the risk of the first portion 1021 contacting an electrode of opposite polarity. The ratio L of the thickness d1 of the first insulating layer 121 to the thickness d3 of the first portion 1021 satisfies the following condition: L ≤ 1.3. This reduces the thickness of the first insulating layer 121, and the combined thickness of the first insulating layer 121 and the first portion 1021 is also relatively small, making it easier to bend the first portion 1021 of the tab 102. In a battery cell including the above-mentioned electrode piece 1 , the risks of self-discharge, short circuit, etc. caused by the electrode assembly of the battery cell after the tab 102 is bent and inserted into the battery cell can be reduced, which is beneficial to improving the reliability of the battery cell.

[0103] In some embodiments, the ratio L of the thickness d1 of the first insulating layer 121 to the thickness d3 of the first portion 1021 satisfies: L≤1. Thus, the first insulating layer 121 has a smaller thickness, which further reduces the risk of short circuits caused by the partial insertion of the tab into the electrode assembly of the battery cell after the tab 102 is bent.

[0104] In some embodiments, L satisfies the following relationship: 1 / 30 ≤ L ≤ 1. This provides the first insulating layer 121 with a suitable thickness, facilitating the fabrication of the first insulating layer 121. Furthermore, when the first insulating layer 121 includes a thermoplastic polymer, L is greater than or equal to 1 / 30, indicating a relatively high content of the thermoplastic polymer in the first insulating layer 121. This allows a suitable amount of the thermoplastic polymer to melt and flow to the end surface, thereby forming a relatively uniform and dense second insulating layer at the end surface.

[0105] In some embodiments, L satisfies: 4 / 13≤L≤6 / 13. This facilitates the preparation of the first insulating layer 121 and further reduces the risk of bending the tab 102 before inserting it into the electrode assembly.

[0106] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: d1≤10 μm, for example, d1 is 0.5 μm, 1 μm, 3 μm, 5 μm, 6 μm, 8 μm, 10 μm or any value within the above range.

[0107] When the thickness d1 of the first insulating layer 121 does not exceed 10 μm, the total thickness of the first insulating layer 121 is relatively small. Thus, when the number of tabs 102 layers is relatively large, the difficulty of bending the tabs 102 can be reduced, thereby reducing the risk of inserting the bent tabs 102 into the electrode assembly, and further reducing the risk of short circuits caused by the insertion of the tabs into the electrode assembly.

[0108] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: 0.5 μm≤d1≤10 μm.

[0109] When the total thickness d1 of the first insulating layer 121 is not less than 0.5 μm, the first insulating layer 121 has a certain thickness, which can reduce the difficulty of preparing the first insulating layer 121, is conducive to preparing a more uniform first insulating layer 121, and reduces the risk of partial surface exposure of the first part 1021 of the tab 102.

[0110] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: 4 μm≤d1≤6 μm. For example, d1 is 4 μm, 5 μm, 6 μm, or any value within the above range.

[0111] When the thickness d1 of the first insulating layer 121 is not less than 4 μm, it is beneficial to reduce the difficulty of preparing the first insulating layer 121; when the thickness d1 of the first insulating layer 121 does not exceed 6 μm, the first insulating layer 121 has a smaller thickness, which can further reduce the difficulty of bending the tab 102.

[0112] In some embodiments, the first insulating layer 121 has the same thickness on both sides of the first portion 1021. The two insulating layers 121 on both sides have the same thickness, so that the forces on both sides of the first portion 1021 are more uniform and the preparation of the first insulating layer 121 is also facilitated.

[0113] In some embodiments, the main body 101 includes a coating region 1011 and a transition region 1012 . The transition region 1012 is disposed between the coating region 1011 and the tab 102 . The first insulating layer 121 is disposed on surfaces on both sides of the transition region 1012 .

[0114] The first insulating layer 121 may include a first sub-portion 1211 and a second sub-portion 1212 . The first sub-portion 1211 is located on a surface of the transition region 1012 of the main body 101 , and the second sub-portion 1212 is located on a surface of the first portion 1021 of the tab 102 .

[0115] Optionally, in some embodiments, a first insulating layer 121 is provided on a surface of one side of the transition region 1012 .

[0116] In the above embodiment, by providing the first insulating layer 121 on the surface of the transition region 1012 , risks such as short circuits caused by the transition region 1012 overlapping with electrodes of opposite polarity can be reduced.

[0117] In some embodiments, the electrode 1 further includes an active material layer 11, which is disposed on at least one side of the coating region 1011. This prevents the active material layer 11 from being cut during the cutting process, reducing the risk of the active material layer 11 falling off. Furthermore, the provision of the active material layer 11 allows the battery cell to be charged and discharged, facilitating its normal operation.

[0118] In some embodiments, the active material layer 11 is disposed on surfaces of both sides of the coating area 1011 .

[0119] Optionally, in some embodiments, the active material layer 11 is disposed on a surface of one side of the coating area 1011 .

[0120] In some embodiments, the first insulating layer 121 includes a thermoplastic polymer.

[0121] A thermoplastic polymer may be a polymer that softens when heated, solidifies when cooled, and can soften again. For example, when heated to a certain temperature, a thermoplastic polymer changes from solid particles to a flowable state, and when cooled, it can change into a layer or film.

[0122] When the thermoplastic polymer in the first insulating layer 121 is heated to certain conditions, it will change from a solid state to a fluid state. In this way, during the process of cutting the current collector 10 provided with the first insulating layer 121, the fluid thermoplastic polymer can flow to the burrs generated by the cutting and the exposed end faces of the cut current collector 10. After the temperature drops, the fluid thermoplastic polymer solidifies at the burrs and the exposed end faces, thereby covering the burrs and the exposed end faces, thereby reducing the risk of the burrs and the exposed end faces overlapping with electrodes of opposite polarity, which is conducive to further improving the reliability of the battery cell.

[0123] In some embodiments, the maximum particle size D of the thermoplastic polymer is 1 Max satisfied: D 1 max≤10μm; optionally, D 1 Max satisfied: D 1 max≤6μm.

[0124] D 1max can be 3 μm, 5 μm, 7 μm, 8 μm, 9 μm, 10 μm or any value within the above range.

[0125] In this way, the risk of scratches during the preparation of the first insulating layer 121 due to the large maximum particle size of the thermoplastic polymer can be reduced, and it is also beneficial to obtain the first insulating layer 121 with a suitable thickness, thereby facilitating the preparation of the first insulating layer 121.

[0126] In some embodiments, due to factors such as the preparation process of the thermoplastic polymer, the maximum particle size D of the thermoplastic polymer may be 1 max has a certain corresponding relationship with the volume particle size distribution Dv50 of the thermoplastic polymer. For example, the two satisfy the normal distribution or slightly deviate from the normal distribution.

[0127] In some embodiments, the first insulating layer 121 further includes a binder. This facilitates bonding of the thermoplastic polymer in the insulating paste of the first insulating layer 121 to the surface of the current collector 10 during the preparation of the first insulating layer 121, thereby reducing the risk of the thermoplastic polymer falling off the current collector 10.

[0128] Optionally, based on the total mass of the first insulating layer 121 , the mass content A of the thermoplastic polymer satisfies: 40 wt % ≤ A ≤ 80 wt %, and the mass content B of the binder satisfies: 20 wt % ≤ B ≤ 40 wt %.

[0129] A can be 40wt%, 50wt%, 60wt%, 70wt%, 80wt% or any value within the above range, and B can be 20wt%, 30wt%, 35wt%, 40wt% or any value within the above range.

[0130] For example, the first insulating layer 121 includes only a thermoplastic polymer and a binder, the mass content A of the thermoplastic polymer is 60wt%, and the mass content B of the binder is 40wt%; for another example, the mass content A of the thermoplastic polymer is 80wt%, and the mass content B of the binder is 20wt%.

[0131] Alternatively, the first insulating layer 121 may further include substances other than the thermoplastic polymer and the binder. As an example, in this case, A may be 40 wt % and B may be 20 wt %.

[0132] In the above embodiment, the binder has an appropriate mass content, so that the first insulating layer 121 will not fall off the current collector 10; the thermoplastic polymer has an appropriate mass content, so that a uniform and dense second insulating layer 122 can be formed on the exposed end surface after cutting.

[0133] In some embodiments, the first insulating layer 121 further includes inorganic particles. The provision of the inorganic particles can reduce the surface tension of the insulating paste when the thickness of the first insulating layer 121 is small, thereby reducing the risk of the current collector 10 being exposed.

[0134] The inorganic particles may be insulating inorganic particles or inorganic particles that are non-conductive at the operating voltage of the battery (for example, non-conductive at a voltage of 5 V). For example, the inorganic particles may have a certain dielectric constant.

[0135] Inorganic particles have certain ion transport properties, but inorganic particles are insulating at least under the operating voltage of the battery.

[0136] Optionally, the inorganic particles include insulating inorganic particles.

[0137] Optionally, the insulating inorganic particles include at least one of boehmite (γ-AlOOH) and alumina. Boehmite and alumina have excellent heat resistance and insulation properties. By selecting boehmite or alumina as the insulating inorganic particles and adding them to the first insulating layer 121, the first insulating layer 121 has excellent heat resistance and insulation properties. Furthermore, boehmite and alumina are readily available and relatively low in cost.

[0138] For another example, the insulating inorganic particles may also be silicon oxide, etc. The embodiments of the present application include but are not limited to the above.

[0139] In some embodiments, the inorganic particles may also be inorganic particles having a dielectric constant of 3 or higher, and may include boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon oxides SiOx (0<x≤2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), hafnium dioxide (HfO2), cerium oxide (CeO2), zirconium titanate (ZrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), Pb(Zr,Ti)O3 (abbreviated as PZT), Pb1-mLamZr1-nTinO3 (abbreviated as PLZT, 0<m<1, 0<n<1) and Pb(Mg3Nb 2 / 3 ) at least one of O3-PbTiO3 (abbreviated as PMN-PT).

[0140] In some embodiments, the inorganic particles have the ability to transport active ions and may include lithium phosphate (Li3PO4), lithium titanium phosphate (LixTiy(PO4)3, 0<x<2, 0<y<3), lithium aluminum titanium phosphate (LixAlyTiz(PO4)3, 0<x<2, 0<y<1, 0<z<3), (LiAlTiP)xOy glass (0<x<4, 0<y<13), lithium lanthanum titanate (LixLayTiO3 , 0<x<2, 0<y<3), lithium germanium thiophosphate (LixGeyPzSw, 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (LixNy, 0<x<4, 0<y<2), SiS2 type glass (LixSiySz, 0<x<3, 0<y<2, 0<z<4) and P2S5 type glass (LixPySz, 0<x<3, 0<y<3, 0<z<7).

[0141] In some embodiments, the maximum particle size D of the inorganic particles 2 Max satisfied: D 2 max≤10μm; optionally, D 2 Max satisfied: D 2 In this way, the inorganic particles have a suitable particle size, which can reduce the risk of scratches during the preparation of the first insulating layer 121 and is also conducive to obtaining a first insulating layer 121 with a suitable thickness, thereby facilitating the preparation of the first insulating layer 121.

[0142] In some embodiments, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm ≤ Dv50 ≤ 6 μm. For example, Dv50 is 0.5 μm, 1 μm, 2 μm, 4 μm, 5 μm, 6 μm, or any value within the above range.

[0143] In this way, during the preparation of the first insulating layer 121 , the slurry of the first insulating layer 121 has a suitable viscosity, which facilitates the coating of the first insulating layer 121 ; and the slurry of the first insulating layer 121 has a relatively suitable solid content, which facilitates the drying of the first insulating layer 121 .

[0144] Due to the influence of factors such as preparation process, the volume particle size distribution Dv50 of inorganic particles is related to the maximum particle size D 2 For example, when the volume particle size distribution Dv50 of the inorganic particles is 0.5 μm, D 2 max is about 1 μm; when the volume particle size distribution Dv50 of the inorganic particles is 2 μm, D 2 max is about 5μm; when the volume particle size distribution Dv50 of the inorganic particles is 6μm, D 2 The maximum is about 10μm.

[0145] In some embodiments, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤2 μm. In this way, the inorganic particles have a smaller particle size, which facilitates separation of some impurities in the slurry of the first insulating layer 121 from the inorganic particles, thereby facilitating filtering out the impurities.

[0146] In some embodiments, the mass content C of the insulating inorganic particles, based on the total mass of the first insulating layer 121, satisfies the following: 0 < C ≤ 40 wt %. For example, C is 10 wt %, 30 wt %, 35 wt %, 40 wt %, or any value within the aforementioned range. Properly setting the mass content of the insulating inorganic particles can help reduce the surface tension of the insulating slurry when the thickness of the first insulating layer 121 is relatively small, thereby reducing the risk of exposure of the current collector 10.

[0147] For example, in the first insulating layer 121, the mass content A of the thermoplastic polymer is 40 wt%, the mass content B of the binder is 40 wt%, and the mass content C of the inorganic particles is 20 wt%. For another example, A is 40 wt%, B is 20 wt%, and C is 40 wt%. The values ​​of A, B, and C can be any value as long as they fall within the above ranges, and embodiments of the present application include but are not limited to these.

[0148] Optionally, C satisfies: 30wt%≤B≤40wt%.

[0149] In some embodiments, the melting point T of the thermoplastic polymer is 100° C. to 200° C. For example, the melting point of the thermoplastic polymer is 100° C., 110° C., 130° C., 150° C., 200° C., or any value within the above ranges.

[0150] The melting point of a thermoplastic polymer is the temperature at which the thermoplastic polymer changes from a solid or semi-solid state to a liquid state.

[0151] The melting point of the thermoplastic polymer is not less than 100°C, which reduces the risk of the thermoplastic polymer melting or flowing due to heating of the electrode 1 during other processing. The melting point of the thermoplastic polymer does not exceed 200°C, which reduces the risk of the thermoplastic polymer failing to transform into a fluid state during the cutting process, thereby reducing the risk of the second insulating layer 122 not being formed on the exposed end surface of the current collector 10 after cutting, or the risk of the second insulating layer 122 not being uniform and dense enough. In addition, the melting point of the thermoplastic polymer does not exceed 200°C, and the thermoplastic polymer can become fluid with relatively low heat, which helps reduce the energy consumed in cutting.

[0152] In the above embodiment, the thermoplastic polymer has a suitable melting point. During the process of cutting the current collector 10 provided with the first insulating layer 121, the thermoplastic polymer changes from a solid state to a fluid state under the action of the heat generated by the cutting. The fluid thermoplastic polymer can flow to the end surface of the current collector 10 exposed after cutting and the burrs generated by the cutting, thereby facilitating the preparation of the second insulating layer 122.

[0153] In some embodiments, the melting point T of the thermoplastic polymer is 100° C. to 130° C. In this way, the second insulating layer can be prepared with relatively low heat.

[0154] Optionally, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate, and modified polymers thereof.

[0155] Polyolefins are a general term for thermoplastic resins obtained by polymerizing or copolymerizing α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene, as well as certain cycloolefins. For example, polyolefins include polyethylene wax.

[0156] For example, the thermoplastic polymer includes at least one of modified polymers of polystyrene, modified polymers of polyolefin, modified polymers of polyimide, modified polymers of polyester, modified polymers of polyphenylene sulfide, modified polymers of polyaramid, modified polymers of polyamide, and modified polymers of copolymers of butyl acrylate and ethyl methacrylate.

[0157] The melting point of a thermoplastic polymer is related to its molecular weight. Generally speaking, the larger the molecular weight, the higher the melting point. Within the same class of thermoplastic polymers, polymers with different molecular weights have different melting points.

[0158] By using the above-mentioned thermoplastic polymer, it is advantageous to form a uniform and dense coating on the end surface and burrs of the exposed current collector 10 after cutting.

[0159] In some embodiments, the binder includes at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, and sodium alginate.

[0160] The above-mentioned binder has good adhesive properties, which facilitates bonding the thermoplastic polymer to the surface of the current collector 10 .

[0161] Optionally, the binder is polyacrylonitrile, which has good leveling properties and is conducive to uniformly coating the first insulating layer on the surface of the current collector 10 .

[0162] In some embodiments, the adhesive force F between the first insulating layer 121 and the current collector 10 satisfies: 20 N / m to 100 N / m; optionally, F satisfies: 60 N / m≤F≤90 N / m.

[0163] F can be 20 N / m, 60 N / m, 80 N / m, 100 N / m or any value within the above range.

[0164] When the bonding force between the first insulating layer 121 and the current collector 10 is 20 N / m to 100 N / m, the bonding between the first insulating layer 121 and the current collector 10 is relatively strong, which can reduce the risk of the first insulating layer 121 falling off the current collector 10 .

[0165] In some embodiments, along the first direction, the ratio of the dimension k1 of the first portion 1021 to the sum of the dimensions k2 of the first insulating layer 121 and the second portion 1012 satisfies the following: 0.3≤k1:k2≤0.5. For example, k1:k2 is 0.3, 0.4, 0.5, or any value within the aforementioned range.

[0166] k2 is the sum of the size of the first insulating layer 121 and the size of the second portion 1012 along the first direction.

[0167] When k1:k2 is not less than 0.3, it is helpful to reduce the risk of short circuit between the first part 1021 and the electrode with opposite polarity; when k1:k2 does not exceed 0.5, it is beneficial to connect the second part 1022 of the tab 102 with the end cover assembly of the battery cell.

[0168] In some embodiments, the pole piece 1 further includes a second insulating layer 122 . The second insulating layer 122 is disposed on the first end surface 1011 a . The first end surface 1011 a is the end surface of the main body 101 at the first end.

[0169] The first end surface 1011a is a surface parallel to the thickness direction of the current collector 10. For example, as shown in FIG3 , the end surface 1011a is a surface parallel to the y-direction and the z-direction.

[0170] The first end surface 1011a may be formed by the following process: Referring to FIG1 , during the cutting process of the current collector 10, the current collector 10 is cut along the cutting line 124. The first end surface 1011a is the cut end surface of the transition region 1012. After cutting, the current collector 10 is exposed at the first end surface 1011a, and burrs may be generated.

[0171] In the above embodiment, the second insulating layer 122 can cover the first end surface 1011a, reducing the risk of the first end surface 1011a being exposed, thereby reducing the risk of a short circuit caused by the first end surface 1011a overlapping with an electrode of opposite polarity; in addition, the second insulating layer 122 can also cover the burrs generated by the cutting process, reducing the risk of the burrs overlapping with electrodes of opposite polarity.

[0172] In some embodiments, the thickness d2 of the second insulating layer 122 is 10 nm to 400 nm. For example, d2 is 10 nm, 30 nm, 100 nm, 120 nm, 160 nm, 200 nm, 300 nm, 350 nm, 400 nm or any value within the above range.

[0173] Optionally, the thickness d2 of the second insulating layer 122 is related to the thickness d1 of the first insulating layer 121. For example, when the first insulating layer 121 includes a thermoplastic polymer, the greater the thickness d1 of the first insulating layer 121, the more thermoplastic polymer in the first insulating layer 121, and the greater the thickness d2 of the second insulating layer 122, which is more conducive to forming a uniform and dense second insulating layer 122.

[0174] The thickness d2 of the second insulating layer 122 is the average thickness of the second insulating layer 122. For example, the thickness d2 is the average value of the maximum dimension and the minimum dimension of the second insulating layer 122 in the thickness direction.

[0175] The thickness d2 of the second insulating layer 122 can be measured in the following manner: photograph the first end surface 1011 a of the pole piece 1 using a scanning electron microscope (SEM), and measure the thickness d2 of the second insulating layer 122 based on the obtained image.

[0176] In the above embodiment, the second insulating layer 122 can better cover the burrs and the first end surface 1011 a while having a relatively small thickness.

[0177] Optionally, the thickness d2 of the second insulating layer 122 is 100 nm to 200 nm. In this way, the second insulating layer 122 has a relatively large thickness, which is beneficial for further improving the covering effect on the burrs and the first end surface 1011 a.

[0178] In some embodiments, the resistance R of the second insulating layer 122 satisfies: R≧1Ω. For example, R is 1Ω, 5Ω, or 10Ω.

[0179] When the resistance of the second insulating layer 122 is greater than 1Ω, even in some extreme cases, when the first end face 1011a is overlapped with the electrode of opposite polarity, the battery cell will not have an internal short circuit due to the presence of the second insulating layer 122 having a certain resistance, thereby reducing the risk of short circuit or even explosion caused by the internal short circuit.

[0180] Optionally, the resistance R of the second insulating layer 122 satisfies: 50Ω≤R≤500Ω. In this way, when the second insulating layer 122 has a small thickness, the risk of the first end surface 1011a overlapping with an electrode of opposite polarity and causing a short circuit in the battery cell can be reduced.

[0181] In some embodiments, the second insulating layer 122 is disposed on the first end surface 1011 a and the second end surface 1222 a . The second end surface 1222 a is the end surface of the first portion 1021 along the second direction, which is different from the first direction.

[0182] In the case where the pole piece 1 includes a plurality of pole tabs 102, the second direction may be the arrangement direction of the plurality of pole tabs 102. For example, as shown in FIG2 , the second direction is the x direction.

[0183] When cutting the current collector 10 along the cutting line 124 to prepare the tab 102, the cutting tool passes through the region of the second sub-portion 1212 of the first insulating layer 121 (also referred to as the region of the first portion 1021 of the tab 102). After cutting, the second end surface 1222a is exposed. By providing the first insulating layer 121 on the second end surface 1222a, the risk of the second end surface 1222a contacting an electrode of opposite polarity can be reduced.

[0184] Optionally, the second direction is perpendicular to the first direction.

[0185] In the above embodiment, the second insulating layer 122 can cover the second end surface 1222a exposed due to cutting, which can reduce the risk of the second end surface 1222a overlapping with the electrode with opposite polarity.

[0186] Optionally, the resistance of the second end surface 1222 a provided with the second insulating layer 122 is the same as the resistance of the first end surface 1011 a provided with the second insulating layer 122 .

[0187] In some embodiments, the material of the second insulating layer 122 is the same as the thermoplastic polymer material in the first insulating layer 121. This helps to simplify the preparation steps of the pole piece 1 and speed up the production process.

[0188] For example, the current collector 10 coated with the active material layer 11 can be cut first, and then a hot melt tool (such as a hot melt gun, a hot melt coater, etc.) can be used to prepare the second insulating layer 122 at the first end surface 1011a and the second end surface 122a, and the first insulating layer 121 can be prepared in the transition region 1012 and the first portion 1021 of the tab 102. In this way, the first insulating layer 121 and the second insulating layer 122 can be simultaneously prepared in one step.

[0189] For another example, the active material layer 11 and the first insulating layer 121 are first formed on the current collector 10, and the second insulating layer 122 is simultaneously formed during the cutting process. In this way, the tab 102 can be cut and the second insulating layer 122 can be formed simultaneously in one step.

[0190] In some embodiments, the thermoplastic polymer in the second insulating layer 122 is in the form of a film layer. In other words, the second insulating layer 122 includes a thermoplastic polymer in the form of a film layer.

[0191] In the above embodiment, the second insulating layer 122 is formed by melting and solidifying the thermoplastic polymer in the first insulating layer 121. After the thermoplastic polymer in the first insulating layer 121 becomes fluid, it flows to the first end surface 1011a and the second end surface 1222a, where it solidifies to form the second insulating layer 122. This simplifies the preparation steps of the electrode 1, allowing the second insulating layer 122 to be formed simultaneously with cutting.

[0192] In the first insulating layer 121, at least some granular thermoplastic polymer remains. For example, at a position away from the cutting line, the thermoplastic polymer is in the form of particles protruding from the current collector. In the second insulating layer 122, the thermoplastic polymer is in the form of a film layer and has almost no granular shape.

[0193] The granular thermoplastic polymer may have various shapes, such as spheres, rods, and sheets. The granular thermoplastic polymer herein means that the thermoplastic polymer has not become a fluid state and is in a solid state.

[0194] Before cutting the first insulating layer 121, the thermoplastic polymer in the first insulating layer 121 is in a granular form. During the cutting process, some of the thermoplastic polymer in the first insulating layer 121 changes from a solid state to a fluid state (for example, the thermoplastic polymer near the cutting line 124 changes to a fluid state), while the remaining portion of the thermoplastic polymer remains in a solid granular form.

[0195] In some embodiments, the number of tabs 102 layers is greater than or equal to 50. Optionally, the thickness d3 of the first portion 1021 of each tab 102 layer satisfies the following: 10 μm ≤ d3 ≤ 15 μm. Thus, the total thickness of the tabs is no less than 500 μm. Although the total thickness of the tabs is relatively thick, the thinness of the first insulating layer 121 significantly reduces the probability of the tabs bending when inserted into the electrode assembly after the battery cell is fabricated.

[0196] The number of layers of the tabs 102 can be 50, 60, 80, 100 or a larger number. As the number of layers of the tabs 102 increases, the capacity of the battery cell also increases.

[0197] In some embodiments, electrode sheet 1 comprises a positive electrode sheet. Optionally, the current collector comprises aluminum foil. Thus, electrode sheet 1 being a positive electrode sheet reduces the risk of overlap between the positive and negative electrode sheets, thereby improving the reliability of the battery cell. Furthermore, it reduces the risk of overlap between the positive and negative electrode sheets and lithium dendrites.

[0198] In some embodiments, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes at least one of a lithium transition metal oxide and an olivine-structured lithium-containing phosphate.

[0199] Optionally, the lithium-containing phosphate with an olivine structure includes lithium iron phosphate. In this way, the battery cell prepared from the pole piece has higher reliability.

[0200] The general formula of the olivine-structured lithium-containing phosphate can be LiaAxMn1-yByP1-zCzO4-nDn, wherein, 0<a≤1.1, 0.001≤x≤0.1, 0.001≤y<0.5, 0.001≤z≤0.1, 0.001≤n≤0.1, A includes one or more of Zn, Al, Na, K, Mg, Nb, Mo and W, B includes one or more of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, C includes one or more of B, S, Si and N, and D includes one or more of S, F, Cl and Br.

[0201] The olivine-structured lithium-containing phosphate may further include at least one of lithium manganese phosphate and lithium manganese iron phosphate.

[0202] Optionally, the lithium transition metal oxide includes: LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811). In this way, the battery cell prepared from this electrode can have a higher capacity.

[0203] Lithium transition metal oxides may also include other ternary materials, such as NCM622. Lithium-containing transition metal oxides may also include lithium-rich manganese-based materials.

[0204] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process. The molar content of Li is different when the battery is discharged to different states. The above definition of a includes the molar content of Li under different charge and discharge states of the battery (usually the battery voltage is between 2-5V). In the enumeration of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after the charge and discharge cycle. In the enumeration of positive electrode materials in this application, the molar content of O is only a theoretical state value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0205] In some embodiments, the current collector 10 includes a metal foil or a composite current collector, so that the material of the current collector 10 can be easily configured according to actual needs.

[0206] Optionally, the metal foil includes aluminum foil or copper foil.

[0207] Optionally, the composite current collector includes: a polymer material base layer and a metal layer located on at least one surface of the polymer material base layer.

[0208] The above text describes the technical solution of the electrode in conjunction with Figures 1 to 4. The following text describes the method for preparing the electrode in conjunction with Figure 5. The parts corresponding to the electrode can be referred to above and will not be repeated here.

[0209] [Method for preparing electrode]

[0210] FIG5 is a schematic diagram of a method for preparing a pole piece according to an embodiment of the present application. The method 200 can be used to prepare the pole piece 1 in the above embodiment. The method 200 includes the following steps.

[0211] FIG6 is a schematic diagram of a current collector according to an embodiment of the present application. For example, as shown in FIG6 , the current collector 10 is in the shape of a sheet or a rectangle. The shape and size of the current collector 10 can be set according to actual needs, and the embodiments of the present application include but are not limited to this.

[0212] In step 210 , an insulating paste is coated on the first region of the current collector 10 to form a first insulating layer 121 in the first region. A ratio L of a thickness d1 of the first insulating layer 121 to a thickness d3 of the first portion 1021 satisfies: L≤1.3.

[0213] Specifically, the insulating paste is coated on surfaces of both sides of the first region of the current collector 10 .

[0214] FIG7 is a schematic diagram of a current collector coated with a first insulating layer according to an embodiment of the present application. As shown in FIG7 , an insulating slurry is coated on a first region of the current collector 10 to obtain a current collector 10 provided with a first insulating layer 121 .

[0215] The size of the first area can be set according to actual needs. In the embodiment of the present application, the first area corresponds to the transition area 1012 of the main body 101 of the pole piece 1 and the first portion 1021 of the pole tab 102 .

[0216] In step 220 , the current collector 10 provided with the first insulating layer 121 is cut along the cutting lines 124 , wherein at least a portion of the cutting lines 124 is provided in the first region.

[0217] Figure 8 is a schematic diagram of a current collector showing a cutting line according to an embodiment of the present application. As shown in Figure 8 , the current collector 10 is cut along the cutting line 124 to obtain the electrode 1 shown in Figures 2 to 4 .

[0218] In the above technical solution, the thickness of the first insulating layer 121 is relatively small, so that the portion of the pole tab 102 produced after cutting the current collector 10 and provided with the first insulating layer 121 has a relatively small thickness, thereby reducing the difficulty of bending the pole tab 102, and can reduce the risk of short circuit and self-discharge caused by the electrode assembly in the battery cell after the pole tab 102 is bent, which is beneficial to improving the reliability of the battery cell.

[0219] In some embodiments, L satisfies: L≤1; optionally, L satisfies: 1 / 30≤L≤1; optionally, L satisfies: 4 / 13≤L≤6 / 13.

[0220] In some embodiments, the thickness d1 of the first insulating layer satisfies: d1 ≤ 10 μm; alternatively, d1 satisfies: 0.5 μm ≤ d1 ≤ 10 μm; alternatively, d1 satisfies: 4 μm ≤ d1 ≤ 6 μm. This reduces the difficulty in preparing the first insulating layer 121 and further reduces the difficulty in bending the tab 102.

[0221] In some embodiments, the insulating paste includes a thermoplastic polymer emulsion and a binder.

[0222] The thermoplastic polymer emulsion can be a solution obtained by mixing a thermoplastic polymer with water.

[0223] The thermoplastic polymer emulsion and the binder are liquid, and the liquid thermoplastic polymer emulsion and the binder can be evenly mixed in a relatively short time, which is beneficial to reducing the preparation time of the insulating slurry.

[0224] Optionally, the insulating paste only includes a thermoplastic polymer emulsion and a binder. In this way, the insulating paste has a simpler formula, which is convenient for reducing the complexity of production.

[0225] Optionally, based on the total mass of the insulating paste, the mass content A of the thermoplastic polymer in the thermoplastic polymer emulsion in the insulating paste satisfies the following: 40 wt% ≤ A ≤ 80 wt%, and the mass content B of the binder in the insulating paste satisfies the following: 20 wt% ≤ B ≤ 40 wt%. For example, A is 40 wt%, 60 wt%, 80 wt%, or any value within the aforementioned ranges, and B is 20 wt%, 35 wt%, 40 wt%, or any value within the aforementioned ranges.

[0226] By properly setting the mass content of the thermoplastic polymer, it is beneficial to form a uniform and dense second insulating layer 122 at the exposed end surface of the current collector produced by cutting; by properly setting the mass content of the binder, it is beneficial to reduce the risk of the first insulating layer 121 falling off from the current collector 10.

[0227] In some embodiments, the maximum particle size D of the thermoplastic polymer is 1 Max satisfied: D 1 max≤10μm; optionally, D 1 Max satisfied: D 1 max≤6μm.

[0228] In some embodiments, the insulating paste further includes inorganic particles.

[0229] Adding inorganic particles to the insulating paste can reduce the surface tension of the insulating paste during the coating process, thereby reducing the risk of the current collector 10 being exposed due to rupture of the insulating paste when the coating thickness of the insulating paste is small.

[0230] Optionally, based on the total mass of the insulating paste, the mass content C of the inorganic particles in the insulating paste satisfies: 0<C≤40wt%, and C may be 20wt%, 30wt%, 40wt% or any value within the above range.

[0231] By properly setting the mass content of the insulating inorganic particles, the risk of surface exposure of the current collector 10 can be reduced.

[0232] In some embodiments, the maximum particle size D of the inorganic particles 2 Max satisfied: D 2 max≤10μm; optionally, D 2 Max satisfied: D 2 In this way, the inorganic particles have a suitable particle size, which can reduce the risk of scratches during the preparation of the first insulating layer 121 and facilitate the first insulating layer 121 to have a suitable thickness, thereby facilitating the preparation of the first insulating layer 121.

[0233] For example, when the maximum particle size of the inorganic particles is greater than 10 μm and the thickness of the first insulating layer 121 to be prepared is less than 10 μm, some inorganic particles may protrude from the first insulating layer 121 , which is not conducive to controlling the thickness of the first insulating layer 121 .

[0234] Optionally, the volume particle size distribution Dv50 of the inorganic particles satisfies the following conditions: 0.5 μm ≤ Dv50 ≤ 6 μm; alternatively, the volume particle size distribution Dv50 of the inorganic particles satisfies the following conditions: 0.5 μm ≤ Dv50 ≤ 2 μm. Thus, during the preparation of the first insulating layer 121, the insulating slurry has a suitable viscosity, facilitating its coating; and the insulating slurry has a relatively suitable solids content, facilitating drying of the first insulating layer 121.

[0235] In some embodiments, the volume particle size distribution Dv50 of the inorganic particles is 1 μm. In this way, the insulating slurry has a relatively suitable fineness, which facilitates obtaining a first insulating layer with a suitable thickness.

[0236] In some embodiments, the fineness of the insulating paste is about 10 μm, so as to facilitate obtaining a relatively uniform first insulating layer 121 with a suitable thickness.

[0237] In some embodiments, the solid content E of the thermoplastic polymer emulsion satisfies: 30 wt % ≤ E ≤ 50 wt %.

[0238] Solids content refers to the mass percentage of the remaining emulsion after drying under specified conditions. For example, solids content can be measured by drying the emulsion to constant weight at 100°C using a solids content meter. During the preparation of thermoplastic polymer emulsions, the solids content can be calculated by dividing the mass of the thermoplastic polymer by the mass of the added solvent.

[0239] Setting the solid content E of the thermoplastic polymer emulsion to meet the above conditions facilitates the preparation of the thermoplastic polymer emulsion.

[0240] In some embodiments, the melting point of the thermoplastic polymer in the thermoplastic polymer emulsion is 100°C to 200°C; optionally, the thermoplastic polymer includes at least one of: polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers.

[0241] In the above technical solution, the thermoplastic polymer has a suitable melting point. During the process of cutting the current collector 10 provided with the first insulating layer 121, the heat generated by the cutting causes the thermoplastic polymer to change from a solid state to a fluid state. The fluid thermoplastic polymer can flow to the end faces of the exposed current collector 10 after cutting and to the burrs generated by the cutting, thereby facilitating the preparation of the second insulating layer 122. By using the above thermoplastic polymer, it is advantageous to form a uniform and dense coating on the end faces and burrs of the exposed current collector 10 after cutting.

[0242] In some embodiments, the binder includes at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, and sodium alginate. These binders have good adhesive properties, facilitating bonding of the thermoplastic polymer to the surface of the current collector 10.

[0243] Optionally, the binder is polyacrylonitrile, which has good leveling properties and is conducive to uniformly coating the first insulating layer on the surface of the current collector 10 .

[0244] In some embodiments, step 210 includes coating the insulating paste on the first region of the current collector 10 by gravure coating to form the first insulating layer 121 in the first region. The gravure coating method facilitates the preparation of the first insulating layer 121 with a smaller thickness.

[0245] As an example, a gravure coater may be used for gravure coating, for example, the gravure coater includes a gravure roller, a pressure roller, and a scraper, and the first insulating layer 121 is coated by the cooperation of the gravure roller, the pressure roller, and the scraper.

[0246] In some embodiments, the method 200 further includes: after step 210 , coating an active material on the second region of the current collector 10 to form an active material layer 11 on the second region.

[0247] Specifically, active material is coated on surfaces on both sides of the second region.

[0248] Figure 9 is a schematic diagram of a current collector coated with an active material layer according to an embodiment of the present application. As shown in Figure 9 , the active material is coated in the second region of the current collector 10 to obtain a current collector 10 provided with an active material layer 11 .

[0249] The second region of the current collector 10 can be a region set according to actual needs. In the embodiment of the present application, the second region corresponds to the coating area 1011 of the main body 101 of the electrode 1.

[0250] The thickness of the active material layer 11 may be several tens of micrometers, which is greater than the thickness of the first insulating layer 121 .

[0251] In the above embodiment, since the thickness of the active material layer 11 is greater than the thickness of the first insulating layer 121, preparing the active material layer 11 after step 220 can reduce the impact of the thicker active material layer 11 on the preparation of the first insulating layer 121, making it easier to prepare the first insulating layer 121 with a smaller thickness by gravure coating.

[0252] In some embodiments, step 230 includes: controlling a laser processing tool to cut the current collector provided with the first insulating layer 121 along a cutting line 124 .

[0253] In the above embodiment, the current collector 10 is cut by laser, and a large amount of heat can be generated during the cutting process, which is conducive to the thermoplastic polymer in the first insulating layer 121 becoming fluid and flowing to the exposed end surface of the current collector 10, thereby facilitating the formation of the second insulating layer 122.

[0254] The laser processing tool's operating parameters can be set according to actual needs. For example, different power, frequency, and feed speed can be set according to the type of thermoplastic polymer.

[0255] [Positive electrode]

[0256] The electrode sheet 1 in the embodiment of the present application may be a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector.

[0257] The positive electrode current collector may be a metal foil or a composite current collector. For example, the positive electrode current collector may be an aluminum foil.

[0258] The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0259] The positive electrode film layer includes a positive electrode active material. The positive electrode active material can be any positive electrode active material known in the art for use in batteries. For example, the positive electrode active material is lithium iron phosphate, a ternary material, or a lithium-rich manganese-based material.

[0260] The positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0261] The positive electrode film layer may further optionally include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0262] [Negative electrode]

[0263] The electrode sheet 1 in the embodiment of the present application may be a negative electrode sheet, which includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector.

[0264] The negative electrode current collector can be a metal foil or a composite current collector. The negative electrode current collector can be copper foil. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0265] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be a negative electrode active material for batteries that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0266] The negative electrode film layer may optionally include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0267] [Electrolytes]

[0268] The electrolyte conducts ions between the positive and negative electrodes. The present invention does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0269] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0270] The electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0271] The solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0272] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and may also include performance additives that can improve certain battery properties, such as improving battery overcharge performance, improving battery high or low temperature performance, etc.

[0273] [Isolation film]

[0274] The separator is used to separate the positive electrode sheet from the negative electrode sheet. The present invention has no particular restrictions on the type of separator, and any known porous separator with good chemical and mechanical stability can be used.

[0275] The material of the separator can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0276] The positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly through a winding process or a lamination process.

[0277] [Battery Cell]

[0278] An embodiment of the present application provides a battery cell, comprising the pole piece 1 in the above embodiment, and / or a pole piece prepared by the method in the above embodiment.

[0279] The embodiment of the present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. The battery cell can be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, a magnesium-ion battery, or the like.

[0280] FIG10 is a schematic diagram of a battery cell according to an embodiment of the present application. For example, as shown in FIG10 , the battery cell 3 is a square battery cell. The battery cell 3 includes a housing 31 , an end cap assembly 32 , and an electrode assembly 33 disposed in the housing 31 .

[0281] The electrode assembly 33 can be made of a positive electrode sheet, a negative electrode sheet and a separator by a winding process or a lamination process. In some embodiments, the positive electrode sheet is the electrode sheet 1 in the embodiment of the present application.

[0282] The end cap assembly 32 includes an electrode terminal 322 . For example, as shown in FIG. 10 , the end cap assembly 32 includes two electrode terminals 322 , one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0283] The battery cell 3 further includes a current collecting member 34, which is used to connect the electrode tab 331 of the electrode assembly 33 and the electrode terminal 322. For example, when the electrode sheet 1 in the embodiment of the present application is a positive electrode sheet, one current collecting member 34 is used to connect the positive electrode tab (which may also be the tab 102 of the electrode sheet 1) and the positive electrode terminal, and the other current collecting member 34 is used to connect the negative electrode tab and the negative electrode terminal.

[0284] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in a battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0285] [Battery]

[0286] The present invention provides a battery comprising the battery cells of the above-mentioned embodiment. Figure 11 is a schematic diagram of a battery according to an embodiment of the present invention. As shown in Figure 11, the battery 5 may comprise a plurality of battery cells (not shown in the figure).

[0287] The battery cells 3 can be directly assembled into the battery 5 , or they can be assembled into battery modules first, and then multiple battery modules can be assembled into the battery 5 .

[0288] [Electrical devices]

[0289] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0290] Figure 12 is a schematic diagram of an electric device according to an embodiment of the present application. As shown in Figure 12, the present application provides an electric device 6, which includes the battery according to the above embodiment.

[0291] Optionally, the electrical device may also be an energy storage device, a lighting device, a spacecraft, etc., and the embodiments of the present application include but are not limited to the above.

[0292] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0293] [Example]

[0294] Example 1

[0295] In Example 1, the structure of the electrode 1 is shown in Figure 2. The first insulating layer 121 includes a thermoplastic polymer and a binder. The insulating paste of the first insulating layer 121 includes a thermoplastic polymer emulsion and a binder. Based on the total mass of the insulating paste, the mass content A of the thermoplastic polymer in the thermoplastic polymer emulsion in the insulating paste is 70wt%, and the mass content B of the binder in the insulating paste is 30wt%. The thickness d1 of the first insulating layer 121 is 4μm, and the thickness d3 of the first portion 1021 of the electrode tab 102 is 13μm. The thermoplastic polymer is made of polyethylene wax with a melting point of 130°C.

[0296] Examples 2-7

[0297] The difference between Examples 2-7 and Example 1 is that the total thickness of the first insulating layer 121 is different; accordingly, the thickness of the second insulating layer 122 is different. Specific parameters can be found in Table 1.

[0298] Examples 8-9

[0299] The difference between Examples 8-9 and Example 1 is that the mass content A of the thermoplastic polymer in the insulating paste of the first insulating layer 121 is different. Accordingly, the mass content B of the binder in the insulating paste is also different.

[0300] Examples 10-12

[0301] The difference between Examples 10-12 and Example 1 is that the thermoplastic polymer in the thermoplastic polymer emulsion is different. Specifically, the thermoplastic polymer in Example 12 is polyester, and the melting point of polyester is 220°C.

[0302] Examples 13-15

[0303] The difference between Examples 13-15 and Example 1 is that the insulating paste of the first insulating layer 121 further includes insulating inorganic particles.

[0304] Example 16

[0305] The difference between Example 16 and Example 1 is that the adhesive is different.

[0306] Examples 17-18

[0307] The difference between Examples 17-18 and Example 1 is that, along the first direction, the ratio k1:k2 of the size k1 of the first portion 1021 of the tab 102 to the size k2 of the tab 102 is different.

[0308] Example 19

[0309] The difference between Example 19 and Example 1 is that the insulating paste of the first insulating layer 121 does not include thermoplastic polymer, the first insulating layer includes a binder and insulating inorganic particles, the thickness of the first insulating layer 121 is 4 μm, and the pole piece does not include the second insulating layer 122 .

[0310] Examples 20-21

[0311] The difference between Example 20 and Example 21 and Example 14 is that the thickness of the first insulating layer is different, and the particle size of the inorganic particles is different. In Example 20 and Example 21, the thickness of the first insulating layer is increased, and the particle size of the inorganic particles that can be used is also increased.

[0312] Examples 22-23

[0313] The difference between Examples 22-23 and Example 1 is that the thickness of a single layer of the tab and the number of tab layers are different.

[0314] Example 24

[0315] The difference between Example 24 and Example 7 is that the thickness of a single layer of the tab and the number of tab layers are different.

[0316] Example 25

[0317] The difference between Example 25 and Example 1 is that the thickness of the first insulating layer and the thickness of the single layer of the tab are different.

[0318] Example 26

[0319] The difference between Example 26 and Example 2 is that the thickness of the single layer of the tab is different.

[0320] Example 27

[0321] The difference between Example 27 and Example 5 is that the particle size of the thermoplastic polymer is different.

[0322] Example 28

[0323] The difference between Example 28 and Example 6 is that the particle size of the thermoplastic polymer is different.

[0324] In Examples 1-28, the first insulating layer 121 on both side surfaces of the current collector has the same thickness.

[0325] Comparative Example 1

[0326] Comparative Example 1 differs from Example 1 in that the insulating paste of first insulating layer 121 does not include a thermoplastic polymer, the thickness of one side of first insulating layer 121 is 20 μm (total thickness 40 μm), and the pole piece does not include second insulating layer 122. The insulating paste includes boehmite and a binder in a mass ratio of 70:30, and the binder is polyvinylidene fluoride (PVDF).

[0327] Comparative Example 2

[0328] The difference between Comparative Example 2 and Example 1 is that the thickness of one side of the first insulating layer 121 is 20 μm (the total thickness is 40 μm).

[0329] Comparative Example 3

[0330] The difference between Comparative Example 3 and Comparative Example 1 is that the thickness of the single layer of the tab is different.

[0331] In Table 1, d1 is the thickness of the first insulating layer 121, T is the melting point of the thermoplastic polymer in the first insulating layer 121, A is the mass content of the thermoplastic polymer in the insulating paste of the first insulating layer 121, B is the mass content of the binder in the insulating paste of the first insulating layer 121, C is the mass content of the insulating inorganic particles in the insulating paste of the first insulating layer 121, F is the bonding force between the first insulating layer 121 and the current collector 10, d2 is the thickness of the second insulating layer 122, R is the resistance of the second insulating layer 122, and k1:k2 is the ratio of the size k1 of the first insulating layer along the first direction to the sum k2 of the size of the first insulating layer and the size of the second portion 1012.

[0332] In Table 2, whether a short circuit occurs can reflect the state of the thermoplastic polymer at the end surface, that is, whether the second insulating layer is completely provided at the end surface, and the short circuit is not caused by the tab being inserted into the electrode assembly.

[0333]

[0334]

[0335] Table 2 Experimental results of comparative examples and embodiments

[0336] [Preparation of battery cells]

[0337] (1) Prepare insulation slurry

[0338] Mix a thermoplastic polymer emulsion, insulating inorganic particles (optional), and a binder in a specific ratio. Add a solvent and stir thoroughly until the slurry has a viscosity of approximately 300 mPa·s. The solvent is water. The specific thermoplastic polymer and the ratios of thermoplastic polymer emulsion, dispersant (or insulating inorganic particles), and binder are shown in Table 1.

[0339] (2) Coating and drying

[0340] The insulating slurry was applied to aluminum foil using gravure coating to a 10 mm coating width, leaving a 30 μm width for the tabs. The slurry was then oven-dried at 100°C. The thickness of the first insulating layer after drying is shown in Table 1. The positive electrode slurry was then evenly coated on the aluminum foil and dried in an oven at 100°C to form the positive electrode active material layer. The positive electrode active material in the slurry was lithium iron phosphate.

[0341] (3) Laser die cutting

[0342] The above product is rolled and cut using a laser to obtain a positive electrode sheet, wherein the laser power is 20W, the frequency is 100kHz, and the conveying speed is 30m / min.

[0343] (4) Preparation of battery cells

[0344] The positive electrode sheet, separator, and negative electrode sheet are stacked in order so that the separator is located between the positive electrode sheet and the negative electrode sheet and can isolate the positive electrode sheet from the negative electrode sheet; the stacked components are then wound and placed in a shell, dried, and then injected with electrolyte, and packaged to obtain a lithium-ion battery cell.

[0345] It should be noted that the insulating slurry does not include a thermoplastic polymer emulsion in Example 19 and Comparative Example 1. For Comparative Examples 1, 2, and 3, the first insulating layer is not prepared by gravure coating but by extrusion coating.

[0346] [Confirmation of the first insulating layer]

[0347] Use a scanning electron microscope to observe the surface of the electrode to check whether there is a first insulating layer on the surface. Cut the electrode open and photograph the cross section of the electrode using a scanning electron microscope. Observe the thickness of the first insulating layer based on the photographed photos.

[0348] [Confirmation of the second insulating layer]

[0349] A scanning electron microscope (SEM) is used to observe the end face to check whether there is a second insulating layer at the end face; in addition, the thickness of the second insulating layer can also be observed through photos taken by the scanning electron microscope.

[0350] [Overlapping full-charge anode test]

[0351] Use the laser die-cut end face to overlap the fully charged anode and observe whether there is a short circuit.

[0352] [Test of inserting the tab into the electrode assembly]

[0353] Computed tomography (CT) is used to detect whether the tabs in the battery cells are inserted into the electrode assembly.

[0354] [Test of Adhesion]

[0355] Select a plate-like material with a smooth surface as the first substrate, stick one side of the double-sided tape on the surface of the first substrate, and stick the other side of the double-sided tape on the first insulating layer on one side of the pole piece. Select a plate with a sticky coating area as the second substrate, and stick the second substrate to the first insulating layer on the other side of the pole piece. At this time, the pole piece is located between the first substrate and the second substrate. Fix the same sides of the first substrate and the second substrate on the lower and upper ends of the universal tensile testing machine respectively for tensile testing. After the force-relative displacement curve displayed on the universal tensile testing machine runs smoothly, record the tension and displacement values, and select a relatively stable section of the curve to calculate the bonding force, bonding force = tension / displacement.

[0356] [Test of resistance of the second insulating layer]

[0357] The resistance of the second insulating layer can be measured using an ohmmeter.

[0358] For example, one end of the ohmmeter is connected to the tab of the positive electrode sheet in the embodiment (specifically, the portion of the tab not coated with the first insulating layer), and the other end is connected to the tab of the negative electrode sheet, and the end faces of the negative electrode sheet and the positive electrode sheet are overlapped.

[0359] [Particle size test]

[0360] The volume particle size distribution Dv50 can be determined by a particle size analyzer-laser diffraction method. Specifically, the standard GB / T19077-2016 can be referred to, and a laser diffraction scattering particle size analyzer can be used to measure according to the manufacturer's instructions. For example, before preparing the slurry, take an appropriate amount of inorganic particles or thermoplastic polymers, and use the Malvern 2000 (MasterSizer 2000) laser particle size analyzer to test the average volume particle size of the material. Take an appropriate amount of the sample to be tested (the sample concentration is guaranteed to be 8-12% shading), add 20ml of deionized water, and supercharge for 5min (53KHz / 120W) to ensure that the sample is completely dispersed, and then measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard. Afterwards, Dmax can be calculated based on DV50 or obtained based on the instrument.

[0361] For another example, a scanning electron microscope may be used to test the pole piece to obtain an image of the region of the first insulating layer of the pole piece, and the particle size of the thermoplastic polymer or inorganic particles may be measured based on the image.

[0362] [Confirmation of the melting point of thermoplastic polymer]

[0363] The melting point of a thermoplastic polymer can be determined using a differential scanning calorimeter (DSC). Specifically, as an example, an 8 mg sample is placed in the DSC instrument and heated at a rate of 10°C / min under an N2 atmosphere at a flow rate of 50 ml / min, with a cutoff temperature of 400°C.

[0364] For another example, the melting point of a thermoplastic polymer can be determined based on the specific type of thermoplastic polymer. For example, for a crystalline thermoplastic polymer, the melting point refers to the melting point of the crystalline thermoplastic polymer; for an amorphous thermoplastic polymer, the melting point refers to the glass transition temperature of the amorphous thermoplastic polymer.

[0365] [Mass ratio of thermoplastic polymer, inorganic particles and binder]

[0366] The above mass ratio can be obtained according to the mass of the thermoplastic polymer emulsion, the mass of the inorganic particles and the mass of the binder added during the preparation process.

[0367] In addition, the thermoplastic polymer, binder and inorganic particles in the pole piece can also be determined in the following way.

[0368] Scrape the first insulating layer with a knife to form a powder or block. Place approximately 1g of the film sample in a mold and heat to the melting point of the thermoplastic polymer. This can then be formed into a film and subjected to infrared FTIR analysis to identify the polymer type based on characteristic peaks. Alternatively, thermogravimetric coupled infrared FTIR (TG-FTIR) analysis can be used to heat the film sample from room temperature to 600°C. The film composition can be determined by observing the thermal decomposition temperature, weight loss ratio, and product composition.

[0369] As shown in Examples 1-28 and Comparative Examples 1-2, when the ratio of the thickness of the first insulating layer to the thickness of the first portion of the tab is less than or equal to 1.3, the thickness of the first insulating layer is small, and the sum of the thicknesses of the first insulating layer and the first portion is small. In the case of a large number of tab layers, the tab will not be inserted into the electrode assembly. Therefore, the embodiments of the present application can reduce the risk of the tab being inserted into the electrode assembly.

[0370] As shown in Examples 1-7, as the thickness of the first insulating layer increases, the thickness of the second insulating layer also gradually increases, and the bonding force between the current collector and the first insulating layer gradually decreases. By reasonably setting the thickness of the first insulating layer, a second insulating layer with a relatively suitable thickness can be obtained, and the second insulating layer has a suitable resistance. In addition, when the thickness of the first insulating layer is not less than 0.5 μm, the preparation of the first insulating layer is facilitated, and the risk of the current collector being exposed due to the first insulating layer being too thin can be reduced; and a relatively uniform second insulating layer can also be obtained, reducing the risk of the second insulating layer being present at some end positions. In addition, as shown in Examples 25-26 and 1-7, the preparation of the first insulating layer is facilitated by reasonably setting the particle size of the thermoplastic polymer.

[0371] As shown in Examples 8-9, as the mass content of the thermoplastic polymer increases, more of the thermoplastic polymer melts and flows to the end surface during cutting, resulting in a greater thickness of the second insulating layer. As the mass content of the thermoplastic polymer increases, the mass content of the binder that can be added decreases. When the mass content of the binder decreases, the adhesion between the current collector and the first insulating layer decreases. Properly setting the mass content of the thermoplastic polymer ensures a suitable thickness for the second insulating layer; and properly setting the mass content of the binder ensures a suitable adhesion between the current collector and the first insulating layer.

[0372] As shown in Examples 10-11, the embodiments of the present application can be applied to different thermoplastic polymers; as shown in Example 12, when the melting point of the thermoplastic polymer is relatively high, it is more difficult for the thermoplastic polymer to melt completely and requires more heat to melt; therefore, there is thermoplastic polymer at some positions of the end surface, and when it is overlapped with the negative electrode plate, a short circuit occurs at some positions.

[0373] As shown in Examples 13-15, adding inorganic particles to the insulating slurry and properly setting the mass content of the inorganic particles will prevent the current collector from being exposed due to the first insulating layer being too thin. By properly setting the particle size of the inorganic particles, the preparation of the first insulating layer is facilitated.

[0374] As shown in Example 16, the present embodiment is applicable to a variety of binders. By properly matching the binder and the thermoplastic polymer, the preparation and coating of the slurry for the first insulating layer are facilitated, thereby facilitating the preparation of the first insulating layer.

[0375] As shown in Examples 17-18, the embodiments of the present application are applicable to pole pieces with a k1:k2 ratio of 0.3 to 0.5.

[0376] As shown in Example 19, although no thermoplastic polymer is added, the tab will not be inserted into the electrode assembly due to the small thickness of the first insulating layer.

[0377] As shown in Examples 20-21, the maximum particle size of the inorganic particles does not exceed the thickness of the first insulating layer, which can reduce the risk of scratches during the preparation of the first insulating layer due to excessively large inorganic particles. By properly setting the particle size of the inorganic particles, the preparation of the first insulating layer is facilitated.

[0378] As the number of tab layers increases, the total thickness of the tab gradually increases, making it more difficult to bend the tab, and thus increasing the risk of partially inserting the tab into the electrode assembly after the tab is bent. In the embodiments of the present application, as shown in Examples 22-24 and Examples 27-28, even when there are many tab layers, the tabs of the embodiments of the present application will not be inserted into the electrode assembly.

[0379] It should be noted that the above embodiments and comparative examples are described using a positive electrode sheet with an aluminum foil as the current collector. The embodiments of the present application can also be applied to positive electrode sheets and negative electrode sheets with current collectors made of other materials. In addition, although the data is described only based on the example of the first insulating layer on both sides of the current collector having the same thickness, the solution of the present application is still applicable when the thickness is different. The table only shows the values ​​of part of L. When the thickness of the first insulating layer and the thickness of the first part of the tab (or the current collector) change, the ratio of L also changes accordingly.

[0380] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A pole piece, comprising: a current collector and a first insulating layer, in, The current collector includes a main body and a tab, the tab extends from a first end of the main body, the first end is an end of the main body along a first direction, the tab includes a first part and a second part, the first part is close to the main body relative to the second part, the first insulating layer is provided on the surfaces of both sides of the first part, and a ratio L of the thickness of the first insulating layer to the thickness of the first part satisfies: L≤1.

3.

2. The pole piece according to claim 1, wherein: A ratio L of the thickness of the first insulating layer to the thickness of the first portion satisfies: L≤1; optionally, L satisfies: 1 / 30≤L≤1; Optionally, L satisfies: 4 / 13≤L≤6 / 13.

3. The pole piece according to claim 1 or 2, wherein: The thickness d1 of the first insulating layer satisfies: d1≤10 μm; optionally, d1 satisfies: 0.5 μm≤d1≤10 μm; optionally, d1 satisfies: 4 μm≤d1≤6 μm.

4. The pole piece according to any one of claims 1 to 3, wherein: The thickness of the first insulating layer on both side surfaces of the first portion is the same.

5. The pole piece according to any one of claims 1 to 4, wherein: The main body includes a coating area and a transition area, wherein the transition area is arranged between the coating area and the tab, and the first insulating layer is arranged on surfaces of both sides of the transition area.

6. The pole piece according to claim 5, wherein: The pole piece further includes an active material layer, and the active material layer is disposed on a surface of at least one side of the coating area.

7. The pole piece according to any one of claims 1 to 6, wherein: The first insulating layer includes a thermoplastic polymer.

8. The pole piece according to claim 7, wherein: The maximum particle size D of the thermoplastic polymer 1 max Satisfaction: D 1 max ≤10μm; optionally, D 1 max Satisfaction: D 1 max ≤6μm.

9. The pole piece according to claim 7 or 8, wherein: The first insulating layer further includes a binder; optionally, based on the total mass of the first insulating layer, a mass content A of the thermoplastic polymer satisfies: 40wt%≤A≤80wt%, and a mass content B of the binder satisfies: 20wt%≤B≤40wt%.

10. The pole piece according to any one of claims 7 to 9, wherein: The first insulating layer further comprises inorganic particles; optionally, the inorganic particles comprise insulating inorganic particles; optionally, the insulating inorganic particles comprise at least one of boehmite and alumina.

11. The pole piece according to claim 10, wherein: Based on the total mass of the first insulating layer, the mass content C of the inorganic particles satisfies: 0<C≤40wt%; optionally, C satisfies: 30wt%≤B≤40wt%.

12. The pole piece according to claim 10 or 11, wherein: The maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤10μm; optionally, D 2 max Satisfaction: D 2 max ≤6μm.

13. The pole piece according to any one of claims 10 to 12, wherein: The volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤6 μm; optionally, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤2 μm.

14. The pole piece according to any one of claims 7 to 13, wherein: The melting point T of the thermoplastic polymer satisfies: 100°C≤T≤200°C; optionally, T satisfies: 100°C≤T≤130°C.

15. The pole piece according to any one of claims 7 to 14, wherein: The thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers; optionally, the polyolefin includes polyethylene wax.

16. The pole piece according to any one of claims 7 to 15, wherein: The binder comprises at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan and sodium alginate.

17. A pole piece according to any one of claims 1 to 16, wherein: The bonding force F between the first insulating layer and the current collector satisfies: 20 N / m≤F≤100 N / m; optionally, F satisfies: 60 N / m≤F≤90 N / m.

18. The pole piece according to any one of claims 1 to 17, wherein: Along the first direction, a ratio of a size k1 of the first insulating layer to a sum k2 of sizes of the first insulating layer and the second portion satisfies: 0.3≤k1:k2≤0.

5.

19. The pole piece according to any one of claims 1 to 18, wherein: The pole piece further includes a second insulating layer, and the second insulating layer is disposed on a first end surface, and the first end surface is an end surface of the main body at the first end.

20. The pole piece according to claim 19, wherein: The thickness d2 of the second insulating layer is 10 nm to 400 nm; optionally, the thickness d2 of the second insulating layer is 100 nm to 200 nm.

21. The pole piece according to claim 18 or 19, wherein: The resistance R of the second insulating layer satisfies: R≥1Ω; optionally, R satisfies: 50Ω≤R≤500Ω.

22. A pole piece according to any one of claims 19 to 21, wherein: The second insulating layer is arranged on the first end surface and the second end surface, the second end surface is the end surfaces at both ends of the first part along a second direction, and the second direction is different from the first direction; optionally, the second direction is perpendicular to the first direction.

23. A pole piece according to any one of claims 19 to 22, wherein: The material of the second insulating layer is the same as the material of the thermoplastic polymer in the first insulating layer.

24. A pole piece according to any one of claims 19 to 23, wherein: The thermoplastic polymer in the second insulating layer is in the form of a film layer.

25. A pole piece according to any one of claims 1 to 24, wherein: The number of layers of the pole tab is greater than or equal to 50; optionally, the thickness d3 of the first portion of each layer of the pole tab satisfies: 10 μm≤d3≤15 μm.

26. A pole piece according to any one of claims 1 to 25, wherein: The electrode sheet includes a positive electrode sheet; optionally, the current collector includes aluminum foil.

27. The pole piece according to claim 26, wherein: The positive electrode plate includes a positive electrode active material, and the positive electrode active material includes at least one of a lithium transition metal oxide and an olivine structured lithium-containing phosphate; optionally, the olivine structured lithium-containing phosphate includes lithium iron phosphate; optionally, the lithium transition metal oxide includes: LiNi 0.8 Co 0.1 Mn 0.1 O2.

28. A method for preparing a pole piece, comprising: Coating an insulating paste on a first region of the current collector to form a first insulating layer in the first region, wherein a ratio L of a thickness d1 of the first insulating layer to a thickness of the first portion satisfies: L≤1.3; The current collector provided with the first insulating layer is cut along cutting lines, and at least a portion of the cutting lines are provided in the first region.

29. The method according to claim 28, wherein: A ratio L of the thickness d1 of the first insulating layer to the thickness of the first portion satisfies: L≤1; optionally, L satisfies: 1 / 30≤L≤1; Optionally, L satisfies: 4 / 13≤L≤6 / 13.

30. The method according to claim 28 or 29, wherein: The thickness d1 of the first insulating layer satisfies: d1≤10 μm; optionally, 0.5 μm≤d1≤10 μm; optionally, d1 satisfies: 4 μm≤d1≤6 μm.

31. The method according to any one of claims 28 to 30, wherein: The insulating paste comprises a thermoplastic polymer emulsion and a binder; optionally, based on the total mass of the insulating paste, the mass content A of the thermoplastic polymer in the thermoplastic polymer emulsion in the insulating paste satisfies: 40wt%≤A≤80wt%, and the mass content B of the binder satisfies: 20wt%≤B≤40wt%.

32. The method according to claim 31, wherein: The maximum particle size D of the thermoplastic polymer in the thermoplastic polymer emulsion is 1 max Satisfaction: D 1 max ≤10μm; optionally, D 1 max Satisfaction: D 1 max ≤6μm.

33. The method according to claim 31 or 32, wherein: The insulating slurry further comprises inorganic particles; optionally, the inorganic particles comprise insulating inorganic particles; optionally, the insulating inorganic particles comprise at least one of boehmite and alumina.

34. The method of claim 33, wherein: The mass content C of the inorganic particles in the insulating paste satisfies: 0<C≤40wt%; optionally, C satisfies: 30wt%≤B≤40wt%.

35. The method according to claim 33 or 34, wherein: The maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤10μm; optionally, D 2 max Satisfaction: D 2 max ≤6μm.

36. The method according to any one of claims 33 to 35, wherein: The volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤6 μm; optionally, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤2 μm.

37. The method according to any one of claims 31 to 36, wherein: The melting point T of the thermoplastic polymer in the thermoplastic polymer emulsion satisfies: 100°C≤T≤200°C; optionally, T satisfies: 100°C≤T≤130°C.

38. The method according to any one of claims 31 to 37, wherein: The thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyaramid, polyamide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers; optionally, the polyolefin includes polyethylene wax.

39. The method according to any one of claims 31 to 38, wherein: The binder comprises at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan and sodium alginate.

40. The method according to any one of claims 28 to 39, wherein: The step of coating an insulating slurry on a first region of the current collector to form a first insulating layer on the first region includes: The insulating slurry is coated on the first region of the current collector by gravure coating to form the first insulating layer in the first region.

41. The method according to any one of claims 28 to 40, wherein: The method further comprises: After coating the insulating slurry on the first region of the current collector to form a first insulating layer in the first region, coating the active material on the second region of the current collector to form an active material layer in the second region.

42. The method according to any one of claims 28 to 41, wherein: The method of cutting the current collector provided with the first insulating layer along the cutting line comprises: The laser processing tool is controlled to cut the current collector provided with the first insulating layer along the cutting line.

43. A battery cell, comprising a pole piece as claimed in any one of claims 1 to 27, and / or a pole piece prepared by the method as claimed in any one of claims 28 to 42.

44. A battery comprising the battery cell according to claim 43.

45. An electrical device comprising the battery as claimed in claim 44.

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