Electrode sheet and manufacturing method therefor, battery cell, battery and electrical apparatus

Abstract

An electrode sheet and a manufacturing method therefor, a battery cell, a battery and an electrical apparatus, belonging to the technical field of batteries. The electrode sheet comprises a current collector, a first insulating layer and a second insulating layer, wherein the current collector comprises a main body part and tabs, the tabs extend from the first end of the main body part, and the first end is one end of the main body part in a first direction. Each tab comprises a first portion and a second portion, the first portion being close to the main body part with respect to the second portion, the surfaces of the two sides of the first portion are respectively provided with the first insulating layer and the second insulating layer, and the thickness d2 of the second insulating layer being greater than the thickness d1 of the first insulating layer. The electrode sheet helps to improve the reliability of battery cells.

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 Chinese patent application No. 202311125047.6 filed on September 1, 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, a first insulating layer and a second 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 surfaces on both sides of the first part being respectively provided with the first insulating layer and the second insulating layer, and the thickness d2 of the second insulating layer being greater than the thickness d1 of the first insulating layer.

[0010] The present invention provides a pole piece comprising a current collector, a first insulating layer, and a second insulating layer. The current collector comprises a main body and a tab. The tab extends from a first end of the main body, the first end being an end of the main body along a first direction. The tab comprises a first portion and a second portion. The first portion is closer to the main body than the second portion. The first and second insulating layers are provided on either side of the first portion, respectively. This reduces the risk of the first portion contacting an electrode of opposite polarity. The thickness d2 of the second insulating layer is greater than the thickness d1 of the first insulating layer. Therefore, when the tab is bent, the second insulating layer is thicker than the first insulating layer, making the side of the first portion with the second insulating layer more difficult to bend than the side of the first portion with the first insulating layer. The second insulating layer provides support for the first insulating layer, and the bent tab occupies less height space. This reduces the risk of the bent tab being squeezed and other factors affecting the electrode assembly inserted into a battery cell, leading to self-discharge and short circuits, thereby improving the reliability of the battery cell.

[0011] In one possible implementation, the ratio of the thickness d2 of the second insulating layer to the thickness d1 of the first insulating layer satisfies: d2 / d1 ≥ 1.8. Thus, the thickness of the first insulating layer and the thickness of the second insulating layer differ to a certain extent, and the surface of the first portion of the tab provided with the second insulating layer is more difficult to bend than the surface of the first portion provided with the first insulating layer, which further reduces the risk of the electrode assembly being inserted into a battery cell after the tab is bent.

[0012] In one possible implementation, the ratio of the thickness d2 of the second insulating layer to the thickness d1 of the first insulating layer satisfies: 2≤d2 / d1≤20. In this way, the thickness difference between the first insulating layer and the second insulating layer is appropriate, facilitating the bending of the tab.

[0013] In a possible implementation, the thickness d1 of the first insulating layer satisfies: 1 μm≤d1≤12 μm; optionally, 4 μm≤d1≤6 μm.

[0014] When d1 is not less than 1 μm, it is beneficial to reduce the difficulty of preparing the first insulating layer; when the thickness d1 of the first insulating layer does not exceed 12 μm, the first insulating layer has a smaller thickness, which is convenient for bending the first part of the tab, and can further reduce the difficulty of bending the tab.

[0015] In one possible implementation, the thickness d2 of the second insulating layer satisfies the following conditions: 10 μm ≤ d2 ≤ 24 μm; alternatively, 16 μm ≤ d2 ≤ 18 μm. This allows the second insulating layer to be bent with suitable difficulty, so that the tab has a suitable shape after bending, reducing the risk of the bent tab being inserted into the electrode assembly of a battery cell.

[0016] 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, with the first and second insulating layers disposed on either side of the transition region. Providing the first and second insulating layers on the transition region helps reduce the risk of short circuits and other issues caused by the transition region overlapping electrodes of opposite polarity.

[0017] In one possible implementation, the electrode sheet further includes an active material layer disposed on at least one side of the coated area. This active material layer prevents the active material layer from being cut during cutting, 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.

[0018] In a possible implementation manner, the first insulating layer and the second insulating layer include thermoplastic polymers.

[0019] In the above technical solution, during the process of cutting the current collector to prepare the tabs, under the action of the heat generated by cutting, the thermoplastic polymers in the first insulating layer and the second insulating layer change from a solid state to a fluid state, and then flow 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.

[0020] In one possible implementation, the maximum particle size D of the thermoplastic polymer is 1 max Satisfied: D 1 max ≤12μm; optionally, D 1 max Satisfied: D 1 max 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.

[0021] In one possible implementation, based on the total mass of the first insulating layer, the mass content A1 of the thermoplastic polymer satisfies the following: 30 wt% ≤ A1 ≤ 40 wt%; and / or, based on the total mass of the second insulating layer, the mass content A2 of the thermoplastic polymer satisfies the following: 30 wt% ≤ A2 ≤ 40 wt%. In this way, the first insulating layer and / or the second insulating layer have an appropriate mass content of the thermoplastic polymer, so that after cutting, a uniform and dense coating can be formed on the exposed end surface.

[0022] In a possible implementation, the melting point T of the thermoplastic polymer satisfies: 100°C ≤ T ≤ 200°C.

[0023] 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 and the second 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 formation of a coating layer at the exposed end face.

[0024] In a possible implementation, the melting point of the thermoplastic polymer is 100° C. to 130° C. In this way, the coating layer can be formed on the exposed end surface at a relatively low temperature.

[0025] In one possible implementation, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide, and modified polymers thereof. Optionally, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; alternatively, the polyamide includes polyaramid; and alternatively, the polyolefin includes polyethylene wax. Using these thermoplastic polymers facilitates forming a uniform, dense coating on the exposed end faces of the trimmed current collector and on any burrs resulting from trimming.

[0026] In a possible implementation, the first insulating layer and the second insulating layer further include inorganic particles. In this way, the first insulating layer and the second insulating layer have good wear resistance, which can reduce the risk of the first insulating layer and the second insulating layer falling off.

[0027] In one possible implementation, based on the total mass of the first insulating layer, the mass content B1 of the inorganic particles satisfies the following: 30 wt% ≤ B1 ≤ 40 wt%; and / or, based on the total mass of the second insulating layer, the mass content B2 of the inorganic particles satisfies the following: 30 wt% ≤ B2 ≤ 40 wt%. By properly setting the mass content of the inorganic particles, the first and second insulating layers have good wear resistance, and the risk of the first and second insulating layers falling off the current collector during the production, transportation, and use of the battery cell is reduced.

[0028] In a possible implementation, the maximum particle size D of the inorganic particles is 2 max Satisfied: D 2 max ≤12μm; optionally, D 2 max Satisfied: D 2 max ≤6μm. 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 the second insulating layer, and is also conducive to obtaining the first insulating layer and the second insulating layer with a suitable thickness, thereby facilitating the preparation of the first insulating layer and the second insulating layer.

[0029] In one possible implementation, 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 and second insulating layers, the slurries of the first and second insulating layers have a suitable viscosity to facilitate coating of the first and second insulating layers; and the slurries of the first and second insulating layers have a relatively suitable solids content to facilitate drying of the first and second insulating layers.

[0030] In a possible implementation, the inorganic particles include insulating inorganic particles. In this way, the first insulating layer and the second insulating layer have certain insulating properties.

[0031] In one possible implementation, the insulating inorganic particles include at least one of boehmite and alumina. Boehmite and alumina have excellent heat resistance and insulation properties. By selecting boehmite or alumina as the insulating inorganic particles, the first insulating layer and the second insulating layer have excellent heat resistance and insulation properties.

[0032] In a possible implementation, the first insulating layer and the second insulating layer further include 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 the current collector.

[0033] In one possible implementation, based on the total mass of the first insulating layer, the binder content C1 satisfies the following: 20 wt% ≤ C1 ≤ 40 wt%; and / or the binder content C2 satisfies the following: 20 wt% ≤ C2 ≤ 40 wt% based on the total mass of the second insulating layer. This allows the binder to have an appropriate content, ensuring suitable adhesion between the first and second insulating layers and the current collector, and reducing the risk of the binder falling off the current collector.

[0034] 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. Alternatively, the binder includes polyacrylonitrile, which exhibits excellent leveling properties, facilitating uniform coating of the first and second insulating layers on the surface of the current collector.

[0035] In one possible implementation, the first insulating layer and the second insulating layer are different in color, which facilitates identification of the first insulating layer and the second insulating layer and facilitates subsequent preparation of the electrode assembly and battery cells.

[0036] In one possible implementation, the bonding force F1 between the first insulating layer and the current collector satisfies the following conditions: 80 N / m ≤ F1 ≤ 200 N / m; alternatively, F1 satisfies the following conditions: 80 N / m ≤ F1 ≤ 145 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.

[0037] In one possible implementation, the bonding force F2 between the second insulating layer and the current collector satisfies the following conditions: 20 N / m ≤ F2 ≤ 100 N / m; alternatively, F2 satisfies the following conditions: 20 N / m ≤ F2 ≤ 65 N / m. This provides a stronger bond between the second insulating layer and the current collector, reducing the risk of the second insulating layer falling off the current collector.

[0038] In a possible implementation, along the first direction, a size k1 of the first insulating layer is the same as a size k2 of the second insulating layer, which is helpful in reducing the complexity of preparing the first insulating layer and the second insulating layer.

[0039] 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 k3 of the first insulating layer and the second portion satisfies the following: 0.3 ≤ k1:k3 ≤ 0.5. When k1:k3 is not less than 0.3, this helps reduce the risk of short circuits caused by the first portion overlapping an electrode of opposite polarity. When k1:k3 is not more than 0.5, this facilitates the connection between the second portion of the tab and the end cap assembly of the battery cell.

[0040] In one possible implementation, the electrode further includes a coating layer disposed on a first end surface, which is the end surface of the main body at the first end. The coating layer can thus 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 coating layer can also cover burrs generated during the cutting process, reducing the risk of burrs overlapping with electrodes of opposite polarity.

[0041] In one possible implementation, the coating layer's thickness d3 satisfies the following conditions: 100 nm ≤ d3 ≤ 200 nm. This allows the coating layer to effectively cover burrs and the exposed first end surface while maintaining a relatively small thickness. Alternatively, the coating layer's thickness d3 satisfies the following conditions: 140 nm ≤ d3 ≤ 200 nm. This further improves the coating effect on burrs and the first end surface.

[0042] In one possible implementation, the resistance R of the coating layer satisfies: R ≥ 50Ω; optionally, R satisfies: 230Ω ≤ R ≤ 500Ω. Satisfying the resistance of the coating layer reduces the risk of short circuiting the battery cell due to overlap between the end surface and an electrode of opposite polarity.

[0043] In one possible implementation, the coating layer is disposed on the first and second end surfaces, where the second end surfaces are the end surfaces of the first portion along a second direction that is different from the first direction; optionally, the second direction is perpendicular to the first direction. This allows the coating layer to cover the second end surface exposed by cutting, reducing the risk of the second end surface contacting an electrode of opposite polarity.

[0044] In one possible implementation, the coating layer includes a thermoplastic polymer, and the material of the thermoplastic polymer in the coating layer is the same as the material of the thermoplastic polymer in the first insulating layer and the second insulating layer. This helps simplify the preparation steps of the electrode and speed up the production process.

[0045] In one possible implementation, the thermoplastic polymer in the coating layer is in film form. Thus, the coating layer is formed by melting and solidifying the thermoplastic polymers in the first and second insulating layers. This simplifies the electrode sheet preparation process, allowing the coating layer to be formed simultaneously with cutting.

[0046] In a possible implementation, the thickness d4 of the first portion of the tab satisfies: 10 μm≤d4≤15 μm. In this way, the tab has a suitable thickness.

[0047] 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.

[0048] 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 layered transition metal oxide, a spinel material, and an olivine structured phosphate material; optionally, the olivine structured phosphate material includes lithium iron phosphate; optionally, the layered transition metal oxide includes: LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0049] 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.

[0050] In a second aspect, a method for preparing the pole piece in the first aspect and any possible implementation thereof is provided, comprising: coating a first insulating slurry and a second insulating slurry on the surfaces of at least both sides of the first part of the pole ear of the current collector, respectively, to prepare a first insulating layer and a second insulating layer, the thickness of the second insulating layer being greater than the thickness of the first insulating layer; and cutting the current collector provided with the first insulating layer and the second insulating layer to prepare the pole piece.

[0051] In the pole piece prepared by the above technical solution, the risk of short circuit and self-discharge caused by the electrode assembly inserted into the battery cell after the pole ear is bent is low, which is conducive to improving the reliability of the battery cell.

[0052] In one possible implementation, the step of coating at least the surfaces of both sides of the first portion of the current collector tab with the first insulating slurry and the second insulating slurry to form the first and second insulating layers includes coating the surfaces of both sides of the transition region between the first portion and the main body of the current collector with the first insulating slurry and the second insulating slurry to form the first and second insulating layers. In this manner, in the prepared pole piece, both the transition region of the main body and the first portion of the tab are provided with the first and second insulating layers.

[0053] In one possible implementation, the first and second insulating slurries are coated on the surfaces of at least both sides of the first portion of the current collector tab, respectively, to form the first and second insulating layers. This includes: coating the first insulating slurry on one side of the first portion by gravure coating to form the first insulating layer; and coating the second insulating slurry on the other side of the first portion by gravure coating or extrusion coating to form the second insulating layer. Gravure coating facilitates the preparation of a thinner first insulating layer; the second insulating layer can be coated using an appropriate coating method based on actual needs or thickness.

[0054] In a possible implementation, the method further includes: coating an active material on the coating region of the main body of the current collector to prepare an active material layer.

[0055] In a possible implementation, the cutting of the current collector provided with the first insulating layer and the second insulating layer includes: controlling a laser processing tool to cut the current collector provided with the first insulating layer and the second insulating layer.

[0056] 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 and the second insulating layer becoming fluid and flowing to the end surface, thereby facilitating the formation of the coating layer.

[0057] In a possible implementation, the first insulating paste is the same as the second insulating paste, which simplifies the preparation process of the first insulating layer and the second insulating layer.

[0058] In a possible implementation, a ratio of a thickness d2 of the second insulating layer to a thickness d1 of the first insulating layer satisfies: d2 / d1≥1.8.

[0059] In a possible implementation, a ratio of a thickness d2 of the second insulating layer to a thickness d1 of the first insulating layer satisfies: 2≤d2 / d1≤20.

[0060] In a possible implementation, the thickness d1 of the first insulating layer satisfies: 1 μm≤d1≤12 μm; optionally, 4 μm≤d1≤6 μm.

[0061] In a possible implementation, the thickness d2 of the second insulating layer satisfies: 10 μm≤d2≤24 μm; optionally, 16 μm≤d2≤18 μm.

[0062] In a possible implementation, the first insulating paste and the second insulating paste include a thermoplastic polymer, a binder, and inorganic particles.

[0063] In one possible implementation, the maximum particle size D of the thermoplastic polymer is 1 max Satisfied: D 1 max ≤12μm; optionally, D 1 max Satisfied: D 1 max ≤6μm.

[0064] In one possible implementation, based on the total mass of the first insulating paste, the mass content A1 of the thermoplastic polymer satisfies: 30wt%≤A≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content A2 of the thermoplastic polymer satisfies: 30wt%≤A2≤40wt%.

[0065] In a possible implementation, the melting point T of the thermoplastic polymer satisfies: 100°C ≤ T ≤ 200°C.

[0066] In a possible implementation, the melting point of the thermoplastic polymer is 100°C to 130°C.

[0067] In one possible implementation, the thermoplastic polymer includes: at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide and their respective modified polymers; optionally, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; optionally, the polyamide includes polyaromatic amide; optionally, the polyolefin includes polyethylene wax.

[0068] In one possible implementation, based on the total mass of the first insulating paste, the mass content B1 of the inorganic particles satisfies: 30wt%≤B1≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content B2 of the inorganic particles satisfies: 30wt%≤B2≤40wt%.

[0069] In a possible implementation, the maximum particle size D of the inorganic particles is 2max Satisfied: D 2 max ≤12μm; optionally, D 2 max Satisfied: D 2 max ≤6μm.

[0070] In a possible implementation, 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.

[0071] In a possible implementation, the inorganic particles include insulating inorganic particles.

[0072] In a possible implementation, the insulating inorganic particles include at least one of boehmite and alumina.

[0073] In one possible implementation, based on the total mass of the first insulating paste, the mass content C1 of the binder satisfies: 20wt%≤C1≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content C2 of the binder satisfies: 20wt%≤C2≤40wt%.

[0074] In a 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.

[0075] 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.

[0076] In one possible implementation, the battery cell includes an electrode assembly, which includes an electrode assembly body and a pole ear portion extending from the electrode assembly body, the surface where the second insulating layer is located faces the electrode assembly body, and the surface where the first insulating layer is located faces away from the electrode assembly body.

[0077] The thickness of the second insulating layer is greater than that of the first insulating layer, and the surface of the second insulating layer faces the main body of the electrode assembly. In this way, the second insulating layer has a certain supporting effect. When the electrode assembly expands or the battery cell is shaken, collided or squeezed, the risk of the pole ear inserting into the main body of the electrode assembly is low, which is beneficial to improving the reliability of the battery cell.

[0078] In one possible implementation, the tab portion includes multiple tabs, and the total number of tab layers is greater than or equal to 50. In this way, the number of tab layers is greater, the number of pole pieces is also greater, the battery cell has a higher energy density, and the risk of the tab portion inserting into the electrode assembly body is reduced.

[0079] In a fourth aspect, a battery is provided, comprising the battery cell described in the third aspect and any possible implementation thereof.

[0080] In a fifth aspect, an electrical device is provided, comprising the battery described in the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] 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.

[0082] FIG1 is a schematic diagram of a pole piece before processing a pole lug according to an embodiment of the present application;

[0083] FIG2 is a schematic diagram of a pole piece according to an embodiment of the present application;

[0084] FIG3 is a cross-sectional view along the AA direction in FIG2 ;

[0085] FIG4 is a cross-sectional view along the BB direction in FIG2 ;

[0086] FIG5 is a schematic diagram of a method for preparing a pole piece according to an embodiment of the present application;

[0087] FIG6 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0088] FIG7 is a schematic diagram of a tab portion of a battery cell according to an embodiment of the present application;

[0089] FIG8 is a schematic diagram of a tab portion of a battery cell in the related art;

[0090] FIG9 is a schematic diagram of the electrode tab being inserted into the electrode assembly;

[0091] FIG10 is a schematic diagram of a battery according to an embodiment of the present application;

[0092] FIG11 is a schematic diagram of an electrical device according to an embodiment of the present application;

[0093] FIG12 is a CT image of a tab portion of a battery cell according to an embodiment of the present application;

[0094] FIG13 is a CT image of the tab portion of a battery cell in a comparative example of the present application;

[0095] FIG14 is a CT image of the electrode ear portion inserted into the electrode assembly body in the comparative example of the present application.

[0096] 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

[0097] 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.

[0098] " 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.

[0099] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0100] 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.

[0101] 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.

[0102] 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 separators into an electrode assembly, and then bend the pole pieces' tabs to save the space occupied by the tabs, thereby increasing the energy density of the battery cells. However, during the preparation and use of battery cells, the bent pole pieces are easily squeezed and may be inserted into the electrode assembly (for example, the non-pole tab part of the pole piece in the electrode assembly), resulting in self-discharge or even short circuit, which is not conducive to improving the reliability of battery cells.

[0103] In view of this, the present application provides a pole piece, comprising a current collector, a first insulating layer, and a second insulating layer. The current collector comprises a main body and a tab, the tab extending from a first end of the main body, the first end being an end of the main body along a first direction. The tab comprises a first portion and a second portion, the first portion being closer to the main body than the second portion, and the first and second insulating layers being provided on both sides of the first portion, respectively. The thickness d2 of the second insulating layer is greater than the thickness d1 of the first insulating layer. Thus, when the tab is bent, because the thickness of the second insulating layer is greater than the thickness of the first insulating layer, the side surface of the first portion provided with the second insulating layer is more difficult to bend than the side surface of the tab provided with the first insulating layer. Thus, the side surface of the first portion provided with the second insulating layer can provide a certain degree of support. In the event of compression, the risk of the bent tab being inserted into the electrode assembly of the battery cell is reduced, thereby reducing the risks of self-discharge, short circuit, etc., and facilitating improved reliability of the battery cell.

[0104] [Pole piece]

[0105] 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.

[0106] 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.

[0107] 1 to 4 , the electrode 1 includes a current collector 10 , a first insulating layer 121 and a second insulating layer 122 .

[0108] 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.

[0109] 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 .

[0110] 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 and a second insulating layer 122 are respectively provided on both sides of the first portion 1021 .

[0111] The first portion 1021 and the second portion 1022 are connected, and the second portion 1022 is not provided with the first insulating layer 121 and the second insulating layer 122 , that is, the second portion 1022 is exposed.

[0112] The surfaces on both sides of the first portion 1021 refer to two opposite surfaces of the first portion 1021 along the thickness direction of the current collector 10. The surfaces on both sides of the first portion 1021 are respectively provided with a first insulating layer 121 and a second insulating layer 122. That is, the surface on one side of the first portion 1021 is provided with the first insulating layer 121, and the surface on the other side of the first portion 1021 is provided with the second insulating layer 122.

[0113] The thickness d2 of the second insulating layer 122 is greater than the thickness d1 of the first insulating layer 121. In other words, the thickness of the second insulating layer 122 is different from the thickness of the first insulating layer 121.

[0114] The thickness d1 of the first insulating layer 121 may refer to the average thickness of the first insulating layer 121. 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 d2 of the second insulating layer 122 refers to the average thickness of the second insulating layer 122.

[0115] The thickness of the second insulating layer 122 is greater than that of the first insulating layer 121. Thus, when the tab 102 is bent, the side surface of the first portion 1021 provided with the second insulating layer 122 is more difficult to bend than the side surface of the first portion 1021 provided with the first insulating layer 121, because the thickness of the second insulating layer 122 is greater than that of the first insulating layer 121. In addition, the second insulating layer 122 also has a certain function of supporting the first insulating layer 121. Compared to the embodiment in which the thickness of the second insulating layer 122 is the same as that of the first insulating layer 121, in the embodiment of the present application, the bent tab 102 occupies less space in the height direction of the battery cell (the height direction of the battery cell can be the arrangement direction of the electrode assembly in the battery cell and the end cap provided with the electrode terminal in the battery cell).

[0116] During the use, transportation, or preparation of the battery cell, the electrode assembly expands, causing the bent tab 102 to be squeezed, or the battery cell is subjected to external forces such as collision and shaking, causing the bent tab 102 to be squeezed by the end cap or the electrode assembly. Through the configuration of the embodiment of the present application, after the bent tab 102 is squeezed, the bent tab 102 occupies less space and the second insulating layer 122 supports the first insulating layer 121, so the risk of the bent tab 102 being inserted into the electrode assembly after being squeezed is reduced. This can reduce the risks of self-discharge, short circuit, etc. caused by the electrode assembly in the battery cell after the bent tab is inserted, which is beneficial to improving the reliability of the battery cell.

[0117] An embodiment of the present application provides a pole piece 1, comprising a current collector 10, a first insulating layer 121, and a second insulating layer 122. 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 and the second insulating layer 122 are respectively provided on the surfaces of both sides of the first portion 101. This reduces the risk of the first portion 1021 overlapping an electrode of opposite polarity. The thickness of the second insulating layer 122 is greater than that of the first insulating layer 121. The surface of the side of the first part 1021 provided with the second insulating layer 122 is more difficult to bend than the surface of the side of the first part 1021 provided with the first insulating layer 121. The second insulating layer 122 can play a certain supporting role for the first insulating layer 121. The space occupied by the bent pole ear 102 in the height direction is smaller, thereby reducing the risk of self-discharge, short circuit, etc. caused by factors such as the bent pole ear 102 being squeezed and affecting the electrode assembly inserted into the battery cell, which is beneficial to improving the reliability of the battery cell.

[0118] In some embodiments, the ratio of the thickness d2 of the second insulating layer 122 to the thickness d1 of the first insulating layer 121 satisfies: d2 / d1≥1.8. For example, d2 / d1 is 1.8, 2, 3, 5, 8, 10, 20, or any other value within the above range.

[0119] When d2 / d1≥1.8, there is a certain difference between the thickness of the first insulating layer 121 and the thickness of the second insulating layer 122. The surface of the side of the first part 1021 of the tab 102 provided with the second insulating layer 122 is more difficult to bend than the surface of the side of the first part 1021 provided with the first insulating layer 121, which is beneficial to further reduce the risk of the electrode assembly in the battery cell after the tab 102 is bent.

[0120] In some embodiments, the ratio of the thickness d2 of the second insulating layer 122 to the thickness d1 of the first insulating layer 121 satisfies: 2≤d2 / d1≤20. In this way, the difference in thickness between the first insulating layer 121 and the second insulating layer 122 is small, facilitating the bending of the tab 102.

[0121] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: 1 μm≤d1≤12 μm. For example, d1 is 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, or any value within the above range.

[0122] When d1 is not less than 1 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 12 μm, the first insulating layer 121 has a smaller thickness, which facilitates bending the first part 1021 of the tab 102, and can further reduce the difficulty of bending the tab 102.

[0123] In some embodiments, d1 satisfies the following: 4 μm ≤ d1 ≤ 6 μm, for example, 4 μm, 5 μm, 6 μm, or any value within the aforementioned range. This helps to further balance the difficulty of preparing the first insulating layer 121 and the difficulty of bending the first portion 1021, facilitating both the preparation of the first insulating layer 121 and the bending of the tab 102.

[0124] In some embodiments, the thickness d2 of the second insulating layer 122 satisfies: 10 μm≤d2≤24 μm. For example, d1 is 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 24 μm, or any value within the above range.

[0125] When d2 is not less than 10 μm, the second insulating layer 122 is significantly more difficult to bend than the first insulating layer 121, which helps the tab 102 have a more suitable shape after bending, reducing the risk of the bent tab 102 being inserted into the electrode assembly of the battery cell. When d2 does not exceed 24 μm, the risk of the second insulating layer 122 being difficult to bend due to its greater thickness is reduced. Thus, when 10 μm ≤ d2 ≤ 24 μm, the second insulating layer 122 has an appropriate degree of bending difficulty, so that the tab 102 has a suitable shape after bending, reducing the risk of the bent tab 102 being inserted into the electrode assembly of the battery cell.

[0126] In some embodiments, d2 satisfies: 16 μm≤d2≤18 μm. Thus, the second insulating layer 122 has a suitable thickness, which not only facilitates the bending of the tab 102 but also reduces the space occupied by the second insulating layer 122, thereby facilitating both the reliability and volume energy density of the battery cell.

[0127] In some embodiments, d1 is 5 μm and d2 is 10 μm. Alternatively, d1 is 6 μm and d2 is 12 μm. d1 and d2 may also be other values ​​that meet the above ranges, and the embodiments of the present application include but are not limited to these.

[0128] In some embodiments, the main body 101 includes a coating area 1011 and a transition area 1012 . The transition area 1012 is disposed between the coating area 1011 and the tab 102 . The surfaces on both sides of the transition area 1012 are respectively provided with a first insulating layer 121 and a second insulating layer 122 .

[0129] A first insulating layer 121 is disposed on a surface on one side of the transition region 1012 and the first portion 1021 , and a second insulating layer 122 is disposed on a surface on the other side of the transition region 1012 and the first portion 1021 .

[0130] The first insulating layer 121 may include a first sub-portion 1211 and a second sub-portion 1212, wherein the first sub-portion 1211 is located on the surface of the transition region 1012 of the main body 101, and the second sub-portion 1212 is located on the surface of the first portion 1021 of the tab 102. Similarly, the second insulating layer 122 includes two sub-portions, one sub-portion being located on the surface of the transition region 1012 of the main body 101, and the other sub-portion being located on the surface of the first portion 1021 of the tab 102.

[0131] In the above embodiment, by respectively providing the first insulating layer 121 and the second insulating layer 122 on the surfaces of both sides 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.

[0132] In some embodiments, the electrode sheet 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.

[0133] In some embodiments, the active material layer 11 is disposed on surfaces of both sides of the coating region 1011 .

[0134] Optionally, in some embodiments, the active material layer 11 is disposed on a surface of one side of the coating region 1011 .

[0135] In some embodiments, the first insulating layer 121 and the second insulating layer 122 include a thermoplastic polymer.

[0136] 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.

[0137] When the thermoplastic polymer in the first insulating layer 121 and the second insulating layer 122 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 and the second insulating layer 122, 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.

[0138] In some embodiments, the maximum particle size D of the thermoplastic polymer is 1 max Satisfied: D 1 max ≤12μm; optionally, D 1 max Satisfied: D 1 max ≤6μm.

[0139] D 1 max It can be 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm or any value within the above range.

[0140] In this way, the risk of scratches during the preparation of the first insulating layer 121 and the second insulating layer 122 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 and the second insulating layer 122 with appropriate thickness, thereby facilitating the preparation of the first insulating layer 121 and the second insulating layer 122.

[0141] 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 There is 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.

[0142] In some embodiments, based on the total mass of the first insulating layer 121, the mass content A1 of the thermoplastic polymer satisfies: 30wt%≤A1≤40wt%; and / or, based on the total mass of the second insulating layer 122, the mass content A2 of the thermoplastic polymer satisfies: 30wt%≤A2≤40wt%.

[0143] A1 can be 30 wt%, 35 wt%, 40 wt% or any value within the above range, and A2 can be 30 wt%, 35 wt%, 40 wt% or any value within the above range. A1 and A2 can be the same value or different values.

[0144] As an example, A1 and A2 are the same value. The slurry of the first insulating layer 121 and the slurry of the second insulating layer 122 have the same formula, which is conducive to reducing the complexity of the preparation.

[0145] In the above embodiment, when 30wt%≤A1≤40wt%, the first insulating layer 121 has a suitable mass content of thermoplastic polymer; when 30wt%≤A2≤40wt%, the second insulating layer 122 has a suitable mass content of thermoplastic polymer; in this way, a uniform and dense coating layer can be formed on the exposed end surface of the current collector 10 after cutting.

[0146] In some embodiments, the melting point T of the thermoplastic polymer satisfies: 100°C ≤ T ≤ 200°C.

[0147] For example, the melting point T of the thermoplastic polymer is 100° C., 110° C., 130° C., 150° C., 200° C., or any value within the above range.

[0148] 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.

[0149] 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 coating layer not being formed on the exposed end surface of the current collector 10 after cutting, or the coating layer being uneven and dense. 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.

[0150] 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 and the second insulating layer 122, 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 face of the current collector 10 exposed after cutting and the burrs generated by the cutting, thereby facilitating the preparation of a coating layer covering the exposed end face.

[0151] In some embodiments, the melting point T of the thermoplastic polymer is 100° C. to 130° C. In this way, the coating layer can be formed on the exposed end surface under the action of relatively low heat.

[0152] In some embodiments, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide, and modified polymers thereof. Alternatively, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; alternatively, the polyamide includes polyaramid; and alternatively, the polyolefin includes polyethylene wax. Using these thermoplastic polymers facilitates forming a uniform, dense coating on the exposed end surfaces of the trimmed current collector 10 and on burrs resulting from trimming.

[0153] 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.

[0154] For example, the thermoplastic polymer includes at least one of a modified polymer of polystyrene, a modified polymer of polyolefin, a modified polymer of polyimide, a modified polymer of polyester, a modified polymer of polyphenylene sulfide, and a modified polymer of polyamide.

[0155] 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.

[0156] In some embodiments, the first insulating layer 121 and the second insulating layer 122 further include inorganic particles.

[0157] The first insulating layer 121 and the second insulating layer 122 include inorganic particles, which help improve the wear resistance of the first insulating layer 121 and the second insulating layer 122. For example, during the use, transportation, or preparation of the battery cell, the first insulating layer 121 may wear from contact with the end cap, adapter, etc. of the battery cell, and the second insulating layer 122 may wear from contact with the electrode assembly of the battery cell. The presence of the inorganic particles improves the wear resistance of the first insulating layer 121 and the second insulating layer 122, reducing the risk of them falling off the current collector 10.

[0158] In some embodiments, based on the total mass of the first insulating layer 121, the mass content B1 of the inorganic particles satisfies: 30wt%≤B1≤40wt%; and / or, based on the total mass of the second insulating layer 122, the mass content B2 of the inorganic particles satisfies: 30wt%≤B2≤40wt%.

[0159] B1 can be 30 wt%, 35 wt%, 40 wt% or any value within the above range, and B2 can be 30 wt%, 35 wt%, 40 wt% or any value within the above range. B1 and B2 can be the same value or different values.

[0160] By reasonably setting the mass content of the inorganic particles, the first insulating layer 121 and the second insulating layer 122 have good wear resistance. During the production, transportation, and use of the battery cell, the risk of the first insulating layer 121 and the second insulating layer 122 falling off from the current collector 10 is relatively low.

[0161] In some embodiments, the maximum particle size D of the inorganic particles 2 max Satisfied: D 2 max ≤12μm; optionally, D 2 max Satisfied: D 2 max 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 the second insulating layer 122, and is also conducive to obtaining the first insulating layer 121 and the second insulating layer 122 with a suitable thickness, thereby facilitating the preparation of the first insulating layer 121 and the second insulating layer 122.

[0162] D 2 max It can be 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm or any value within the above range.

[0163] 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.

[0164] In this way, in the process of preparing the first insulating layer 121 and the second insulating layer 122, the slurry of the first insulating layer 121 and the second insulating layer 122 has a suitable viscosity, which is convenient for coating the first insulating layer 121 and the second insulating layer 122; and the slurry of the first insulating layer 121 and the second insulating layer 122 has a relatively suitable solid content, which is convenient for drying the first insulating layer 121 and the second insulating layer 122.

[0165] 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 max There is a certain correspondence. For example, when the volume particle size distribution Dv50 of the inorganic particles is 0.5 μm, D2 max When the volume particle size distribution Dv50 of the inorganic particles is 2 μm, D 2 max When the volume particle size distribution Dv50 of the inorganic particles is 6 μm, D 2 max It is about 10μm.

[0166] 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 and the second insulating layer 122 from the inorganic particles, thereby facilitating filtering out the impurities.

[0167] In some embodiments, the inorganic particles include insulating inorganic particles. Thus, the first insulating layer 121 and the second insulating layer 122 have certain insulating properties.

[0168] 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 and the second insulating layer 122, the first insulating layer 121 and the second insulating layer 122 have excellent heat resistance and insulation properties. Furthermore, boehmite and alumina are readily available and relatively low in cost.

[0169] The inorganic particles may also be 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.

[0170] Inorganic particles have certain ion transport properties, but inorganic particles are insulating at least under the operating voltage of the battery.

[0171] 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.

[0172] 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 oxide SiO x(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), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0<m<1, 0<n<1) and Pb(Mg3Nb 2 / 3 ) at least one of O3-PbTiO3 (abbreviated as PMN-PT).

[0173] In some embodiments, the inorganic particles have the ability to transport active ions and may include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y Glass-like (0<x<4, 0<y<13), lithium lanthanum titanate (Li x La y TiO3, 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P z S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (Li x N y , 0<x<4, 0<y<2), SiS2 type glass (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4) and P2S5 type glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7).

[0174] In some embodiments, the first insulating layer 121 and the second insulating layer 122 further include a binder. In this way, during the preparation of the first insulating layer 121 and the second insulating layer 122, the thermoplastic polymer in the insulating paste of the first insulating layer 121 and the second insulating layer 122 is easily bonded to the surface of the current collector 10, thereby reducing the risk of the thermoplastic polymer falling off the current collector 10.

[0175] In some embodiments, based on the total mass of the first insulating layer 121, the mass content C1 of the binder satisfies: 20wt%≤C1≤40wt%; and / or, based on the total mass of the second insulating layer 122, the mass content C2 of the binder satisfies: 20wt%≤C2≤40wt%.

[0176] C1 can be 20 wt%, 30 wt%, 35 wt%, 40 wt%, or any value within the aforementioned range, and C2 can be 20 wt%, 30 wt%, 35 wt%, 40 wt%, or any value within the aforementioned range. C1 and C2 can be the same value or different values.

[0177] In the above embodiment, the binder has an appropriate mass content, and the first insulating layer 121 and the second insulating layer 122 have an appropriate adhesive force with the current collector 10 , and the risk of falling off from the current collector 10 is low.

[0178] 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.

[0179] The above-mentioned binder has good adhesive properties, which facilitates bonding the thermoplastic polymer to the surface of the current collector 10 .

[0180] Optionally, the binder is polyacrylonitrile, which has good leveling properties and is conducive to uniformly coating the first insulating layer 121 and the second insulating layer 122 on the surface of the current collector 10 .

[0181] In some embodiments, the adhesive force F1 between the first insulating layer 121 and the current collector 10 satisfies: 80 N / m≤F1≤200 N / m; optionally, F1 satisfies: 80 N / m≤F1≤145 N / m.

[0182] F1 can be 80 N / m, 100 N / m, 120 N / m, 150 N / m, 180 N / m, 200 N / m or any value within the above range.

[0183] When the bonding force between the first insulating layer 121 and the current collector 10 is 80 N / m to 200 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 .

[0184] In some embodiments, the adhesive force F2 between the second insulating layer 122 and the current collector 10 satisfies: 20 N / m≤F2≤100 N / m; optionally, F2 satisfies: 20 N / m≤F2≤65 N / m.

[0185] F2 can be 20 N / m, 60 N / m, 65 N / m, 80 N / m, 90 N / m, 100 N / m or any value within the above range.

[0186] When the bonding force between the second insulating layer 122 and the current collector 10 is 20 N / m to 100 N / m, the bonding between the second insulating layer 122 and the current collector 10 is relatively strong, which can reduce the risk of the second insulating layer 122 falling off the current collector 10 .

[0187] In some embodiments, along the first direction, the size k1 of the first insulating layer 121 is the same as the size k2 of the second insulating layer 122 , which helps reduce the complexity of manufacturing the first insulating layer 121 and the second insulating layer 122 .

[0188] In some embodiments, along the first direction, the ratio of the dimension k1 of the first portion 1021 to the sum of the dimensions k3 of the first insulating layer 121 and the second portion 1012 satisfies the following: 0.3≤k1:k3≤0.5. For example, k1:k3 is 0.3, 0.4, 0.5, or any value within the aforementioned range.

[0189] k3 is the sum of the size of the first insulating layer 121 and the size of the second portion 1012 along the first direction.

[0190] When k1:k3 is not less than 0.3, it is beneficial to reduce the risk of short circuit caused by the first part 1021 overlapping with the electrode of opposite polarity; when k1:k3 does not exceed 0.5, it is beneficial to the connection between the second part 1022 of the tab 102 and the end cover assembly of the battery cell.

[0191] In some embodiments, the pole piece 1 further includes a coating layer 123 . The coating layer 123 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.

[0192] 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 x-direction and the z-direction.

[0193] 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.

[0194] In the above embodiment, the covering layer 123 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 covering layer 123 can also cover the burrs generated by the cutting process, reducing the risk of the burrs overlapping with electrodes of opposite polarity.

[0195] In some embodiments, the thickness d3 of the coating layer 123 satisfies: 100 nm ≤ d3 ≤ 200 nm. For example, d3 is 100 nm, 120 nm, 160 nm, 200 nm, or any value within the above range.

[0196] Optionally, the thickness of the coating layer 123 is related to the thickness of the first insulating layer 121 and the second insulating layer 122. For example, when the first insulating layer 121 and the second insulating layer 122 include thermoplastic polymers, the greater the thickness of the first insulating layer 121 and the second insulating layer 122, the more thermoplastic polymers therein, and the greater the thickness of the coating layer 123, which is more conducive to forming a uniform and dense coating layer 123.

[0197] The thickness d3 of the coating layer 123 is the average thickness of the coating layer 123. For example, the thickness d3 is the average value of the maximum dimension and the minimum dimension of the coating layer 123 in the thickness direction.

[0198] The thickness d3 of the coating layer 123 can be measured in the following manner: photographing the first end surface 1011 a of the pole piece 1 using a scanning electron microscope (SEM), and measuring the thickness d3 of the coating layer 123 based on the obtained image.

[0199] In the above embodiment, the coating layer 123 can better coat the burrs and the first end surface 1011 a while having a relatively small thickness.

[0200] In some embodiments, the resistance R of the coating layer 123 satisfies: R≥50Ω. For example, R is 50Ω, 100Ω, or 200Ω.

[0201] When the resistance of the coating layer 123 is greater than 50Ω, 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 certain resistance of the coating layer 123, thereby reducing the risk of short circuit or even explosion caused by internal short circuit.

[0202] Optionally, the resistance R of the coating layer 123 satisfies: 230Ω≤R≤500Ω. In this way, the risk of the first end surface 1011a overlapping with an electrode of opposite polarity, which may cause a short circuit in the battery cell, can be reduced.

[0203] In some embodiments, the coating layer 123 is disposed on the first end surface 1011a and the second end surface 1222a. The second end surface 1222a is the end surface of the first portion 1021 along the second direction, which is different from the first direction.

[0204] 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.

[0205] When cutting the current collector 10 along the cutting line 124 to prepare the tab 102, the cutting tool passes through the second sub-portion 1212 of the first insulating layer 121 (also referred to as the first portion 1021 of the tab 102). After cutting, the second end surface 1222a is exposed. The coating layer 123 provided on the second end surface 1222a can reduce the risk of the second end surface 1222a contacting an electrode of opposite polarity.

[0206] Optionally, the second direction is perpendicular to the first direction.

[0207] In the above embodiment, the covering layer 123 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.

[0208] In some embodiments, the coating layer 123 includes a thermoplastic polymer, and the material of the thermoplastic polymer in the coating layer 123 is the same as the material of the thermoplastic polymer in the first insulating layer 121 and the second insulating layer 122. This helps to simplify the preparation steps of the pole piece 1 and speed up the production process.

[0209] 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 coating layer 123 at the first end surface 1011a and the second end surface 122a, and the first insulating layer 121 and the second insulating layer 122 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 coating layer 123 can be prepared simultaneously in one step.

[0210] For another example, the active material layer 11, the first insulating layer 121, and the second insulating layer 122 are first formed on the current collector 10, and the coating layer 123 is simultaneously formed during the cutting process. In this way, the tab 102 can be cut and the coating layer 123 can be formed simultaneously in a single step.

[0211] In some embodiments, the thermoplastic polymer in the coating layer 123 is in the form of a film layer. In other words, the coating layer 123 includes a thermoplastic polymer in the form of a film layer.

[0212] In the above embodiment, the coating layer 123 is formed by melting and solidifying the thermoplastic polymer in the first and second insulating layers 121, 122. After the thermoplastic polymer in the first and second insulating layers 121, 122 becomes fluid, it flows to the first and second end faces 1011a, 1222a, where it solidifies to form the coating layer 123. This simplifies the preparation steps of the electrode 1, allowing the coating layer 123 to be formed simultaneously with cutting.

[0213] At least some granular thermoplastic polymer remains in the first and second insulating layers 121 and 122. For example, at a position away from the cutting line 124, the thermoplastic polymer is in the form of particles protruding from the current collector 10. In the coating layer 123, the thermoplastic polymer is in the form of a film layer and has almost no granular shape.

[0214] 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.

[0215] In some embodiments, the thickness d4 of the first portion 1021 of the tab 102 satisfies the following: 10 μm≤d4≤15 μm. Thus, after the first insulating layer 121 and the second insulating layer 122 are provided, the tab 102 has a suitable thickness.

[0216] The thickness d4 of the first portion 1021 may be 10 μm, 12 μm, 15 μm, or any value within the above range.

[0217] 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.

[0218] 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 layered transition metal oxide, a spinel material, and an olivine structure phosphate material.

[0219] Optionally, the phosphate material with an olivine structure includes a lithium-containing phosphate with an olivine structure, such as lithium iron phosphate. In this way, the battery cell prepared from the pole piece has higher reliability.

[0220] The general formula of olivine-structured lithium phosphates can be Li a A x Mn 1-y B y P 1-z C z O 4-n D n , 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.

[0221] The olivine-structured lithium-containing phosphate may further include at least one of lithium manganese phosphate and lithium manganese iron phosphate.

[0222] The layered transition metal oxide includes a layered lithium transition metal oxide or a layered sodium transition metal oxide.

[0223] 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.

[0224] Lithium transition metal oxides can also include other ternary materials, such as LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622). The lithium-containing transition metal oxide may also include lithium-rich manganese-based materials, etc.

[0225] Spinel materials include spinel lithium manganese oxide and the like.

[0226] The positive electrode active material in this embodiment can be a sodium salt used in sodium ion batteries or sodium metal batteries, or can be a lithium salt used in lithium ion batteries or lithium metal batteries.

[0227] 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.

[0228] 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.

[0229] Optionally, the metal foil includes aluminum foil or copper foil.

[0230] 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.

[0231] 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.

[0232] [Method for preparing electrode]

[0233] 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.

[0234] In step 210 , a first insulating slurry and a second insulating slurry are respectively coated on surfaces of at least both sides of the first portion 1021 of the tab 102 of the current collector 10 to prepare a first insulating layer 121 and a second insulating layer 122 , wherein the thickness of the second insulating layer 122 is greater than that of the first insulating layer 121 .

[0235] Step 220 , cutting the current collector 10 provided with the first insulating layer 121 and the second insulating layer 122 to prepare the pole piece 1 .

[0236] Specifically, the current collector 10 provided with the first insulating layer 121 and the second insulating layer 122 is cut along the cutting line 124 .

[0237] In the electrode piece 1 prepared by the above technical solution, the risk of short circuit and self-discharge caused by the electrode assembly of the battery cell after the tab 102 is bent and inserted into the battery cell is low, which is conducive to improving the reliability of the battery cell.

[0238] In some embodiments, step 210 includes: applying a first insulating slurry and a second insulating slurry to the surfaces of both sides of the first portion 1021 and the transition region 1012 of the main body 101 of the current collector 10, respectively, to prepare a first insulating layer 121 and a second insulating layer 122. In this way, in the prepared electrode piece 1, the transition region 1012 of the main body 101 and the first portion 1021 of the electrode tab 102 are both provided with the first insulating layer 121 and the second insulating layer 122.

[0239] In some embodiments, step 210 includes: applying a first insulating slurry to the surface of one side of the first portion 1021 by gravure coating to form a first insulating layer 121; and applying a second insulating slurry to the surface of the other side of the first portion 1021 by gravure coating or extrusion coating to form a second insulating layer 122. Gravure coating facilitates the preparation of a first insulating layer 121 with a relatively small thickness; the second insulating layer 122 can be coated by a suitable coating method based on actual needs or thickness.

[0240] For example, the first insulating layer 121 and the second insulating layer 122 are both prepared by gravure coating. In this way, the first insulating layer 121 and the second insulating layer 122 can be prepared by the same process, which is conducive to reducing the complexity of the process.

[0241] After the first insulating layer 121 and the second insulating layer 122 are prepared, an active material is coated on the coating area 1011 of the current collector 10 to form an active material layer 11. The thickness of the active material layer 11 can be several tens of microns, which is greater than the thickness of the first insulating layer 121. Because the thickness of the active material layer 11 is greater than that of the first insulating layer 121, preparing the active material layer 11 after preparing the first insulating layer 121 can reduce the impact of the thicker active material layer 11 on the preparation of the first insulating layer 121, facilitating the preparation of the thinner first insulating layer 121 by gravure coating.

[0242] As an example, gravure coating can be performed using a gravure coater, which includes a gravure roller, a pressure roller, and a scraper, and the first insulating layer 121 and the second insulating layer 122 are coated by the gravure roller, the pressure roller, and the scraper.

[0243] For another example, the first insulating layer 121 is prepared by gravure coating, and the second insulating layer 122 is prepared by extrusion coating.

[0244] In some embodiments, the method 200 further includes coating an active material on the coating region 1011 of the main body 101 of the current collector 10 to prepare an active material layer 11 .

[0245] In some embodiments, step 230 includes: controlling a laser processing tool to cut the current collector 10 provided with the first insulating layer 121 and the second insulating layer 122 .

[0246] 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 and the second insulating layer 122 becoming a fluid state and flowing to the exposed end surface of the current collector 10, thereby facilitating the formation of the coating layer 123.

[0247] 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.

[0248] In some embodiments, the first insulating paste is the same as the second insulating paste, which simplifies the preparation process of the first insulating layer 121 and the second insulating layer 122 .

[0249] In some embodiments, a ratio of the thickness d2 of the second insulating layer 122 to the thickness d1 of the first insulating layer 121 satisfies: d2 / d1≥2; optionally, 2≤d2 / d1≤20.

[0250] In some embodiments, the thickness d1 of the first insulating layer 121 satisfies: 1 μm≤d1≤12 μm; optionally, 4 μm≤d1≤6 μm.

[0251] In some embodiments, the thickness d2 of the second insulating layer 122 satisfies: 10 μm≤d2≤24 μm.

[0252] In some embodiments, the insulating paste includes a thermoplastic polymer, inorganic particles, and a binder.

[0253] In some embodiments, the maximum particle size D of the thermoplastic polymer is 1 max Satisfied: D 1 max ≤12μm; optionally, D 1 max Satisfied: D 1 max ≤6μm.

[0254] In some embodiments, based on the total mass of the first insulating paste, the mass content A1 of the thermoplastic polymer satisfies: 30wt%≤A≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content A2 of the thermoplastic polymer satisfies: 30wt%≤A2≤40wt%.

[0255] In some embodiments, the melting point T of the thermoplastic polymer satisfies: 100°C ≤ T ≤ 200°C.

[0256] In some embodiments, the thermoplastic polymer has a melting point of 100°C to 130°C.

[0257] In some embodiments, the thermoplastic polymer includes at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide and their respective modified polymers; optionally, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; optionally, the polyamide includes polyaramid; optionally, the polyolefin includes polyethylene wax.

[0258] In some embodiments, based on the total mass of the first insulating paste, the mass content B1 of the inorganic particles satisfies: 30wt%≤B1≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content B2 of the inorganic particles satisfies: 30wt%≤B2≤40wt%.

[0259] In some embodiments, the maximum particle size D of the inorganic particles 2 max Satisfied: D 2 max ≤12μm; optionally, D 2 max Satisfied: D 2 max ≤6μm.

[0260] In some embodiments, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤6 μm; alternatively, the volume particle size distribution Dv50 of the inorganic particles satisfies: 0.5 μm≤Dv50≤2 μm.

[0261] In some embodiments, the inorganic particles include insulating inorganic particles.

[0262] In some embodiments, the insulating inorganic particles include at least one of boehmite and alumina.

[0263] In some embodiments, based on the total mass of the first insulating paste, the mass content C1 of the binder satisfies: 20wt%≤C1≤40wt%; and / or, based on the total mass of the second insulating paste, the mass content C2 of the binder satisfies: 20wt%≤C2≤40wt%.

[0264] 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.

[0265] As an example, a thermoplastic polymer is first mixed with water to form a thermoplastic polymer emulsion, which is then mixed with a binder and inorganic particles. Since the thermoplastic polymer emulsion and binder are liquid, they can be mixed uniformly in a short time, which helps reduce the preparation time of the insulation paste.

[0266] [Positive electrode]

[0267] 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.

[0268] 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.

[0269] 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.).

[0270] The positive electrode film layer includes a positive electrode active material. The positive electrode active material can be a positive electrode active material commonly known in the art for use in batteries. For example, the positive electrode active material is lithium iron phosphate, a ternary material, a lithium-rich manganese-based material, etc.

[0271] 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.

[0272] 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.

[0273] [Negative electrode]

[0274] 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.

[0275] 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.).

[0276] 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.

[0277] The negative 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.

[0278] [Electrolytes]

[0279] 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.

[0280] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0281] 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.

[0282] 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.

[0283] 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.

[0284] [Isolation film]

[0285] 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.

[0286] 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.

[0287] 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.

[0288] [Battery Cell]

[0289] An embodiment of the present application provides a battery cell, comprising the pole piece 1 in the above embodiment, and / or the pole piece 1 prepared by the method in the above embodiment.

[0290] 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.

[0291] Figure 6 is a schematic diagram of a battery cell according to an embodiment of the present application, and Figure 7 is a schematic diagram of a tab portion according to an embodiment of the present application. In some embodiments, as shown in Figures 6 and 7 , the battery cell includes an electrode assembly 33, which includes an electrode assembly body 331 and a tab portion 332 extending from the electrode assembly body 331. The surface of the second insulating layer 122 faces the electrode assembly body 331, and the surface of the first insulating layer 121 faces away from the electrode assembly body 331.

[0292] 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. As an example, the positive electrode sheet is the sheet 1 in the embodiment of the present application.

[0293] The battery cell 3 further includes a shell 31 and an end cover assembly 32 , and the electrode assembly 33 is disposed in the shell 31 .

[0294] The tabs 332 are formed by bending the tabs 102 of the multiple electrode sheets 1. After the tabs 102 are bent, the surface of the second insulating layer 122 faces the electrode assembly body 331, and the surface of the first insulating layer 121 faces the end cap assembly 32. The tabs 332 can be connected to the end cap assembly 32 via a current collecting member 34 (not shown in FIG7 , refer to FIG6 ).

[0295] The thickness of the second insulating layer 122 is greater than that of the first insulating layer 121, and the surface of the second insulating layer 122 faces the electrode assembly body. In this way, the second insulating layer 122 has a certain supporting effect, and the size of the pole ear 332 in the height direction z of the battery cell 3 is relatively small. When the electrode assembly expands or the battery cell is shaken, collided or squeezed, the risk of the pole ear 332 inserting into the electrode assembly body 331 is low, which is beneficial to improving the reliability of the battery cell 3.

[0296] In some embodiments, the tab portion 332 includes a plurality of tabs 102 , and the sum of the number of layers of the plurality of tabs 102 is greater than or equal to 50.

[0297] For example, as shown in FIG6 , a battery cell 3 includes four electrode assemblies, and the tabs in two electrode assemblies are stacked and bent together to form a tab portion 332. In one tab portion 332, the total number of tabs 102 layers is greater than or equal to 50.

[0298] The number of layers of the tabs 102 can be 50, 60, 80, 100 or a larger value. As the number of layers of the tabs 102 increases, the capacity and energy density of the battery cell also increase.

[0299] In this embodiment, the battery cell 1 has a higher energy density. At the same time, due to the arrangement of the first insulating layer 121 and the second insulating layer 122 in the pole piece, the risk of the pole ear 332 being inserted into the electrode assembly body 331 in the event of extrusion after being bent is reduced.

[0300] FIG8 is a schematic diagram of a tab portion of a battery cell in the related art, and FIG9 is a schematic diagram of the tab portion being inserted into an electrode assembly. Referring to FIG8 and FIG9 , in the battery cell shown in FIG8 , the first insulating layer 121 and the second insulating layer 122 of the electrode sheet 1 have the same thickness. After the tab is bent, the bent tab portion 332 is approximately C-shaped, as shown in FIG8 . When the tab portion 332 is squeezed, one tab portion 332 may bifurcate, for example, a portion of the tab portion 332 may separate from another portion of the tab in the middle, and a portion of the tab may be inserted into the electrode assembly body 331.

[0301] In some embodiments, the end cap assembly 32 includes an electrode terminal 322 . For example, as shown in FIG. 6 , 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.

[0302] 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 of the embodiment of the present application is a positive electrode sheet, one current collecting member 34 is used to connect the positive electrode tab 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.

[0303] 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.

[0304] [Battery]

[0305] The present invention provides a battery comprising the battery cells of the above-mentioned embodiment. FIG10 is a schematic diagram of a battery according to an embodiment of the present invention. As shown in FIG10 , the battery 5 may comprise a plurality of battery cells (not shown in the figure).

[0306] 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 .

[0307] [Electrical devices]

[0308] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0309] Figure 11 is a schematic diagram of an electric device according to an embodiment of the present application. As shown in Figure 11 , the present application provides an electric device 6 including the battery according to the above embodiment.

[0310] 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.

[0311] 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.

[0312] [Example]

[0313] Example 1

[0314] In Example 1, the structure of the electrode 1 is shown in Figure 2. The first insulating layer 121 and the second insulating layer 122 are made of the same slurry. The thickness d1 of the first insulating layer 121 is 5 μm, and the thickness d2 of the second insulating layer 122 is 15 μm. The first insulating layer 121 and the second insulating layer 122 are prepared by gravure coating.

[0315] In the slurry for the first insulating layer 121 and the second insulating layer 122, based on the total mass of the slurry, the mass contents of the thermoplastic polymers A1 and A2 are both 40 wt%, the mass contents of the inorganic particles B1 and B2 are both 30 wt%, and the mass contents of the binder C1 and C2 are both 30 wt%. The thermoplastic polymer is polyethylene wax with a melting point of 130°C; the inorganic particles are boehmite; and the binder is polyacrylonitrile.

[0316] Examples 2-8

[0317] The difference between Example 2-8 and Example 1 is that the thickness d1 of the first insulating layer 121 and the thickness d2 of the second insulating layer 122 are different; accordingly, d2 / d1 also changes accordingly. The specific parameters can be seen in Table 1.

[0318] Examples 9-10

[0319] The difference between Examples 9-10 and Example 1 is that the thermoplastic polymers are different.

[0320] Examples 11-13

[0321] The difference between Examples 11-13 and Example 1 is that the mass content of the thermoplastic polymer, the mass content of the inorganic particles, and the mass content of the binder in the slurry of the first insulating layer 121 and the second insulating layer 122 are different.

[0322] Examples 14-15

[0323] The difference between Example 14 and Example 6 is that the particle sizes of the thermoplastic polymer and the inorganic particles are different.

[0324] The difference between Example 15 and Example 1 is that the thicknesses of the first insulating layer 121 and the second insulating layer 122 are different, and the particle sizes of the thermoplastic polymer and the inorganic particles are different.

[0325] In Example 14 and Example 15, the thickness of the first insulating layer 121 and the second insulating layer 122 is thicker than that of Examples 6 and 1, and the particle sizes of the thermoplastic polymer and inorganic particles that can be used are also larger.

[0326] Examples 16-17

[0327] The difference between Examples 16-17 and Example 1 is that, along the first direction, the ratio k1:k3 of the size k1 of the first portion 1021 of the tab 102 to the size k3 of the tab 102 is different.

[0328] Examples 18-20

[0329] The difference between Examples 18-20 and Example 1 is that the thickness of a single layer of the tab and the number of tab layers are different.

[0330] Comparative Example 1

[0331] Comparative Example 1 differs from Example 1 in that the thickness of the insulating layer on both sides of the first portion of the tab is the same, and the insulating slurry of the insulating layer does not include a thermoplastic polymer. The insulating slurry includes boehmite and a binder in a mass ratio of 70:30, and the binder is polyvinylidene fluoride (PVDF).

[0332] Comparative Examples 2-3

[0333] The difference between Comparative Example 2-3 and Example 1 is that the thicknesses of the first insulating layer 121 and the second insulating layer 122 are the same.

[0334] In Table 1, d1 is the thickness of the first insulating layer 121, d2 is the thickness of the first insulating layer 122, T is the melting point of the thermoplastic polymer, A1 and A2 are the mass contents of the thermoplastic polymer in the slurry of the first insulating layer 121 and the second insulating layer 122, respectively, B1 and B2 are the mass contents of the inorganic particles in the slurry of the first insulating layer 121 and the second insulating layer 122, C1 and C2 are the mass contents of the binder in the slurry of the first insulating layer 121 and the second insulating layer 122, F1 is the bonding force between the first insulating layer 121 and the current collector 10, F2 is the bonding force between the second insulating layer 122 and the current collector 10, d3 is the thickness of the coating layer 123, R is the resistance of the coating layer 123, and k1:k3 are the ratios of the dimension k1 of the first insulating layer along the first direction to the sum k3 of the dimension of the first insulating layer and the dimension of the second portion 1012.

[0335] In Table 2, short circuit detection reflects the state of the thermoplastic polymer at the end face, that is, whether the end face is completely covered with the coating. The short circuit is not caused by the tab inserting into the electrode assembly. "10% Insertion" indicates that the tab inserting into the electrode assembly was detected 10% of the time during statistical analysis and random inspection of the obtained battery cell CT images. "10% Failure" indicates that the battery cell self-discharge test detected abnormal self-discharge of the battery cell 10% of the time.

[0336] Table 1 Parameters of Examples and Comparative Examples

[0337] Table 2 Experimental results of comparative examples and embodiments

[0338] [Preparation of battery cells]

[0339] (1) Prepare slurry

[0340] Mix the thermoplastic polymer, inorganic particles, and binder in a specific ratio and add a solvent to mix thoroughly. The slurry has a viscosity of approximately 50 to 500 mPa·s. The solvent is water. The specific ratios of thermoplastic polymer, inorganic particles, and binder are shown in Table 1.

[0341] (2) Coating and drying

[0342] The slurry was coated onto aluminum foil with a coating width of 10 mm, leaving a 30 μm width for the tabs. The slurry was then oven-dried at 100°C. The thicknesses of the first and second insulating layers after drying are shown in Table 1. The positive electrode slurry was then evenly coated onto 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.

[0343] (3) Laser die cutting

[0344] 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.

[0345] (4) Preparation of battery cells

[0346] 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.

[0347] It should be noted that, for Comparative Example 1 and Comparative Example 3, the first insulating layer and the second insulating layer were prepared by extrusion coating.

[0348] [Confirmation of the first and second insulating layers]

[0349] Use a scanning electron microscope to observe the surface of the electrode to check whether the first insulating layer and the second insulating layer are present 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 and the second insulating layer based on the photograph.

[0350] [Confirmation of coating layer]

[0351] A scanning electron microscope (SEM) is used to observe the end face to check whether there is a coating layer on the end face; in addition, the thickness of the coating layer can also be observed through photos taken by the scanning electron microscope.

[0352] [Overlapping full-charge anode test]

[0353] Use the laser die-cut end face to overlap the fully charged anode and observe whether there is a short circuit.

[0354] [Test of inserting the tab into the electrode assembly]

[0355] Computed tomography (CT) is used to detect whether the tabs in the battery cells are inserted into the electrode assembly.

[0356] In embodiments of the present application, multiple battery cells with identical configurations can be tested, and the risk of tab insertion into the electrode assembly can be determined based on the multiple test results. For example, a 10% insertion risk may mean that, among multiple battery cells with identical configurations, 10% of the CT images captured show tab insertion into the electrode assembly.

[0357] [Test of Adhesion]

[0358] 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 value and displacement value, and select a relatively stable section of the curve to calculate the bonding force, bonding force = tension / displacement.

[0359] [Test of the resistance of the coating layer]

[0360] The resistance of the coating can be measured using an ohmmeter.

[0361] 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.

[0362] [Particle size test]

[0363] 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 for measurement 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 sufficient to ensure 8-12% shading), add 20ml of deionized water, and supercharge it 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, D can be calculated based on DV50 or obtained based on the instrument. max .

[0364] For another example, a scanning electron microscope can be used to test the electrode to obtain images of the first insulating layer and the second insulating layer of the electrode, and the particle size of the thermoplastic polymer or inorganic particles can be measured based on the images.

[0365] [Confirmation of the melting point of thermoplastic polymer]

[0366] 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.

[0367] 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.

[0368] [Mass ratio of thermoplastic polymer, inorganic particles and binder]

[0369] 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.

[0370] In addition, the thermoplastic polymer, binder and inorganic particles in the pole piece can also be determined in the following way.

[0371] 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.

[0372] [Self-discharge test]

[0373] The battery is adjusted to 80% SOC and stored for 48 hours. The voltage before storage is V1, and the voltage after storage is V2. k = (V1-V2) / 48.

[0374] Among them, k is used to characterize the self-discharge performance of the battery. When k≤0.2mV / h, it means that the self-discharge test has passed.

[0375] In the embodiment of the present application, multiple battery cells with the same configuration may be tested, and whether the self-discharge test is qualified or not may be determined based on the multiple test results. For example, a 10% failure may mean that, among multiple battery cells with the same configuration, 10% of the battery cells fail the self-discharge test.

[0376] It should be noted that the tabs inserted into the electrode assembly in the embodiment of the present application refer to the tabs being inserted into the non-tab portion of the electrode assembly, that is, the tabs being inserted into the main body of the electrode assembly.

[0377] FIG12 is a CT image of the pole ear portion of a battery cell according to an embodiment of the present application, FIG13 is a CT image of the pole ear portion of a battery cell according to a comparative example of the present application, and FIG14 is a CT image of the pole ear portion of the comparative example of the present application inserted into the electrode assembly body.

[0378] Figures 13 and 14 are CT schematic diagrams of the tab portion and the electrode assembly of Comparative Example 3. In conjunction with Comparative Example 3 and Figures 13 and 14, when the thickness of the second insulating layer is the same as the thickness of the first insulating layer, and when the thickness of the second insulating layer and the first insulating layer are both large, the risk of the tab portion bifurcating from the middle and inserting into the main body of the electrode assembly increases. In conjunction with Figure 12 and Examples 1-20, when the number of tab layers is large, the tab will not insert into the electrode assembly or the risk of inserting into the electrode assembly is reduced. Therefore, the embodiments of the present application can reduce the risk of the tab inserting into the electrode assembly.

[0379] As shown in Examples 2-7, as the thickness of the first and second insulating layers increases, the thickness of the coating layer also gradually increases, and the bonding force between the current collector and the first and second insulating layers gradually decreases. By properly setting the thickness of the first and second insulating layers, a coating layer with a suitable thickness and a suitable resistance can be obtained.

[0380] In combination with Examples 1-7 and 8, when d2 / d1 is greater than or equal to 2, the risk of the tab being inserted into the electrode assembly is further reduced. In addition, in combination with Examples 14-15 and 1-8, by reasonably setting the particle size of the thermoplastic polymer and the inorganic particles, the preparation of the first insulating layer and the second insulating layer is facilitated. 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 reasonably setting the particle size of the inorganic particles, the preparation of the first insulating layer is facilitated.

[0381] As shown in Examples 9-10, the embodiments of the present application can be applied to different thermoplastic polymers.

[0382] As shown in Examples 11-13, as the mass content of the thermoplastic polymer increases, more of the thermoplastic polymer melts and flows to the end faces during cutting, resulting in a thicker coating 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 coating layer thickness; properly setting the mass content of the binder ensures suitable adhesion between the current collector and the first and second insulating layers.

[0383] As shown in Examples 16-17, the embodiments of the present application are applicable to pole pieces with a k1:k3 ratio of 0.3 to 0.5.

[0384] 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 a portion of the tab being inserted into the electrode assembly after the tab is bent. In the embodiments of the present application, as shown in combination with Examples 1-20, when the number of tab layers is large, the risk of the tab being inserted into the electrode assembly in the embodiments of the present application is low.

[0385] It should be noted that the above embodiments and comparative examples are described using a positive electrode sheet with an aluminum foil current collector. The embodiments of the present application are also applicable to positive and negative electrode sheets with current collectors made of other materials. Furthermore, although the data is described using the same slurry for the first and second insulating layers as an example, the present solution is still applicable even when the slurries are different.

[0386] 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, characterized in that: It includes: a current collector, a first insulating layer and a second insulating layer, in, The current collector includes a main body and a tab, the tab extending from a first end of the main body, the first end being an end of the main body along a first direction, the tab including 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 and the second insulating layer being respectively provided on surfaces on both sides of the first part, the thickness d2 of the second insulating layer being greater than the thickness d1 of the first insulating layer.

2. The pole piece according to claim 1, characterized in that: A ratio of a thickness d2 of the second insulating layer to a thickness d1 of the first insulating layer satisfies: d2 / d1≥1.

8.

3. The pole piece according to claim 1 or 2, characterized in that: A ratio of a thickness d2 of the second insulating layer to a thickness d1 of the first insulating layer satisfies: 2≤d2 / d1≤20.

4. The pole piece according to any one of claims 1 to 3, characterized in that: The thickness d1 of the first insulating layer satisfies: 1 μm≤d1≤12 μm; optionally, 4 μm≤d1≤6 μm.

5. The pole piece according to any one of claims 1 to 4, characterized in that: The thickness d2 of the second insulating layer satisfies: 10 μm≤d2≤24 μm; optionally, 16 μm≤d2≤18 μm.

6. The pole piece according to any one of claims 1 to 5, characterized in that: 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 surfaces on both sides of the transition area are respectively provided with the first insulating layer and the second insulating layer.

7. The pole piece according to claim 6, characterized in that: 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.

8. The pole piece according to any one of claims 1 to 7, characterized in that: The first insulating layer and the second insulating layer include a thermoplastic polymer.

9. The pole piece according to claim 8, characterized in that: The maximum particle size D of the thermoplastic polymer 1 max Satisfaction: D 1 max ≤12μm; Optionally, D 1 max Satisfaction: D 1 max ≤6μm.

10. The pole piece according to claim 8 or 9, characterized in that: Based on the total mass of the first insulating layer, the mass content A1 of the thermoplastic polymer satisfies: 30wt%≤A1≤40wt%; and / or, based on the total mass of the second insulating layer, the mass content A2 of the thermoplastic polymer satisfies: 30wt%≤A2≤40wt%.

11. The pole piece according to any one of claims 8 to 10, characterized in that: The melting point T of the thermoplastic polymer satisfies: 100°C≤T≤200°C; optionally, T satisfies: 100°C≤T≤130°C.

12. The pole piece according to claim 11, characterized in that: The thermoplastic polymer includes: at least one of polystyrene, polyolefin, polyimide, polyester, polyphenylene sulfide, polyamide and their respective modified polymers; optionally, the polyester includes a copolymer of butyl acrylate and ethyl methacrylate; optionally, the polyamide includes polyaromatic amide; optionally, the polyolefin includes polyethylene wax.

13. The pole piece according to any one of claims 8 to 12, characterized in that: The first insulating layer and the second insulating layer further include inorganic particles.

14. The pole piece according to claim 13, characterized in that: Based on the total mass of the first insulating layer, the mass content B1 of the inorganic particles satisfies: 30wt%≤B1≤40wt%; and / or, based on the total mass of the second insulating layer, the mass content B2 of the inorganic particles satisfies: 30wt%≤B2≤40wt%.

15. The pole piece according to claim 13 or 14, characterized in that: The maximum particle size D of the inorganic particles 2 max Satisfaction: D 2 max ≤12μm; Optionally, D 2 max Satisfaction: D 2 max ≤6μm.

16. The pole piece according to any one of claims 8 to 15, characterized in that: The first insulating layer and the second insulating layer further include an adhesive.

17. The pole piece according to claim 16, characterized in that: Based on the total mass of the first insulating layer, the mass content C1 of the binder satisfies: 20wt%≤C1≤40wt%; and / or, based on the total mass of the second insulating layer, the mass content C2 of the binder satisfies: 20wt%≤C2≤40wt%.

18. The pole piece according to claim 16 or 17, characterized in that: The binder comprises at least one of polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyacrylic acid, polyacrylonitrile, gelatin, chitosan and sodium alginate.

19. The pole piece according to any one of claims 1 to 18, characterized in that: The first insulating layer and the second insulating layer have different colors.

20. The pole piece according to any one of claims 1 to 19, characterized in that: The bonding force F1 between the first insulating layer and the current collector satisfies: 80 N / m≤F1≤200 N / m; optionally, F1 satisfies: 80 N / m≤F1≤145 N / m.

21. The pole piece according to any one of claims 1 to 20, characterized in that: The bonding force F2 between the second insulating layer and the current collector satisfies: 20 N / m≤F2≤100 N / m; optionally, F2 satisfies: 20 N / m≤F2≤65 N / m.

22. The pole piece according to any one of claims 1 to 21, characterized in that: Along the first direction, a size k1 of the first insulating layer is the same as a size k2 of the second insulating layer.

23. The pole piece according to any one of claims 1 to 22, characterized in that: Along the first direction, a ratio of a size k1 of the first insulating layer to a sum k3 of sizes of the first insulating layer and the second portion satisfies: 0.3≤k1:k3≤0.

5.

24. The pole piece according to any one of claims 1 to 23, characterized in that: The pole piece further includes a coating layer, and the coating 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.

25. The pole piece according to claim 24, characterized in that: The thickness d3 of the coating layer satisfies: 100nm≤d3≤200nm; optionally, the thickness d3 of the coating layer satisfies: 140nm≤d3≤200nm.

26. The pole piece according to claim 24 or 25, characterized in that: The resistance R of the coating layer satisfies: R≥50Ω; optionally, R satisfies: 230Ω≤R≤500Ω.

27. The pole piece according to any one of claims 24 to 26, characterized in that: The covering layer includes a thermoplastic polymer, and a material of the thermoplastic polymer in the covering layer is the same as a material of the thermoplastic polymer in the first insulating layer and the second insulating layer.

28. The pole piece according to claim 27, characterized in that: The thermoplastic polymer in the coating layer is in the form of a film layer.

29. The pole piece according to any one of claims 1 to 28, characterized in that: A thickness d4 of the first portion of the tab satisfies: 10 μm≤d4≤15 μm.

30. The pole piece according to any one of claims 1 to 29, characterized in that: The electrode sheet includes a positive electrode sheet; optionally, the current collector includes aluminum foil.

31. The pole piece according to claim 30, characterized in that: The positive electrode plate includes a positive electrode active material, and the positive electrode active material includes at least one of a layered transition metal oxide, a spinel material, and an olivine structure phosphate material.

32. A method for preparing a pole piece as claimed in any one of claims 1 to 31, characterized in that: include: Coating a first insulating slurry and a second insulating slurry respectively on surfaces of at least both sides of the first portion of the electrode tab of the current collector to prepare a first insulating layer and a second insulating layer, wherein the thickness of the second insulating layer is greater than the thickness of the first insulating layer; The current collector provided with the first insulating layer and the second insulating layer is cut to prepare the pole piece.

33. The method according to claim 32, characterized in that The method comprises: coating the first insulating slurry and the second insulating slurry on the surfaces of at least both sides of the first part of the electrode ear of the current collector to prepare the first insulating layer and the second insulating layer, comprising: The first insulating slurry and the second insulating slurry are respectively coated on surfaces of both sides of the transition region between the first portion and the main body of the current collector to prepare the first insulating layer and the second insulating layer.

34. The method according to claim 32 or 33, characterized in that The method comprises: coating the first insulating slurry and the second insulating slurry on the surfaces of at least both sides of the first part of the electrode ear of the current collector to prepare the first insulating layer and the second insulating layer, comprising: Coating the first insulating slurry on a surface of one side of the first portion by gravure coating to prepare the first insulating layer; The second insulating film is coated on the surface of the other side of the first part by gravure coating or extrusion coating. slurry to prepare the second insulating layer.

35. The method according to any one of claims 32 to 34, characterized in that The method further comprises: An active material is coated on the coating region of the main body portion of the current collector to prepare an active material layer.

36. The method according to any one of claims 32 to 35, characterized in that The step of cutting the current collector provided with the first insulating layer and the second insulating layer to prepare the pole piece comprises: The laser processing tool is controlled to cut the current collector provided with the first insulating layer and the second insulating layer.

37. The method according to any one of claims 32 to 36, characterized in that The first insulating paste is the same as the second insulating paste.

38. A battery cell, characterized in that: Comprising a pole piece as described in any one of claims 1-31, and / or a pole piece prepared by the method as described in any one of claims 32-37.

39. The battery cell according to claim 38, characterized in that The battery cell includes an electrode assembly, which includes an electrode assembly body and an electrode ear portion extending from the electrode assembly body, a surface where the second insulating layer is located faces the electrode assembly body, and a surface where the first insulating layer is located faces away from the electrode assembly body.

40. The battery cell according to claim 39, characterized in that The pole lug portion includes a plurality of pole lugs, and a sum of the number of layers of the plurality of pole lugs is greater than or equal to 50.

41. A battery, characterized in that: Comprising a battery cell as claimed in any one of claims 38 to 40.

42. An electrical device, characterized in that: Comprising a battery as claimed in claim 41.

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