Electrode sheets and their preparation methods, battery cells, batteries, and electrical devices.

Abstract

This application provides an electrode sheet and its preparation method, a battery cell, a battery, and an electrical device, belonging to the field of battery technology. The electrode sheet includes a current collector, an active material layer, and a first insulating layer. The current collector includes a main body and a tab, with the tab extending from a first end of the main body along a first direction. The main body includes a coating area and a transition area, with the transition area disposed between the coating area and the tab. The active material layer is disposed on the surface of the coating area. The first insulating layer includes a first portion and a second portion. The first portion is disposed on the surface of the transition area, and the second portion extends from the first portion along the first direction and is disposed in an area outside the tab. Along the first direction, the minimum distance L of the second portion extending beyond the main body is 10 μm to 80 μm. The technical solution of this application is beneficial for improving the reliability of the battery cell.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrode sheet and its preparation method, a battery cell, a battery, and an electrical device. Background Technology

[0002] With increasing environmental pollution, the new energy industry is attracting more and more attention. Within the new energy industry, battery technology is a crucial factor in its development.

[0003] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, and reliability. The design of the electrodes in a battery cell is crucial to its reliability; therefore, how to provide an electrode that improves the reliability of a battery cell is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide an electrode to improve the reliability of a single battery cell.

[0005] To achieve the above objectives, this application provides an electrode sheet and its preparation method, a battery cell, a battery, and an electrical device.

[0006] In a first aspect, an electrode is provided, comprising a current collector, an active material layer, and a first insulating layer. 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 one end of the main body along a first direction. The main body includes a coating area and a transition area, the transition area being disposed between the coating area and the tab. The active material layer is disposed on the surface of the coating area. The first insulating layer includes a first portion and a second portion, the first portion being disposed on the surface of the transition area, and the second portion extending from the first portion along the first direction and disposed in a region other than the tab. Along the first direction, the minimum distance L of the second portion extending beyond the main body is 10 μm to 80 μm.

[0007] This application provides an electrode sheet, which includes a current collector, an active material layer, and a first insulating layer. The current collector includes a main body and a tab, with the tab extending from a first end of the main body, which is one end of the main body along a first direction. The main body includes a coating area and a transition area, with the transition area disposed between the coating area and the tab. The coating area is provided with the active material layer. Thus, by providing the transition area, during the tab cutting process, the cutting tool can maintain a certain distance from the active material layer, reducing the shedding of the active material layer. The first insulating layer includes a first portion and a second portion. The first portion is disposed on the surface of the transition area, and the second portion extends from the first portion along the first direction and is suspended. Along the first direction, the second portion extends beyond the main body by a minimum distance L of 10μm to 80μm. Thus, the second portion can prevent the exposed current collector or burrs on the end face from contacting the electrode with the opposite polarity, thereby reducing the risk of short circuit in the battery cell and improving the reliability of the battery cell.

[0008] In one possible implementation, the second portion extends beyond the main body by a minimum distance L of 50 μm to 60 μm along the first direction. This prevents the end face and its burrs from overlapping with electrodes of opposite polarity.

[0009] In one possible implementation, the first insulating layer comprises a thermally expanding material.

[0010] In the above technical solution, a significant amount of heat is generated during the cutting of the current collector with the first insulating layer. The first insulating layer includes a thermally expanding material, which expands under the heat generated during cutting, extending beyond the main body of the current collector along a first direction. This facilitates the preparation of the second portion of the first insulating layer.

[0011] In one possible implementation, the thermally expandable material comprises thermally expandable microspheres having a core-shell structure, wherein the outer shell of the core-shell structure is made of a thermoplastic polymer, and the inner core of the core-shell structure is made of a foaming agent.

[0012] In the above technical solution, under the heat generated during cutting, the foaming agent, which serves as the core, expands, while the thermoplastic polymer, which serves as the outer shell, softens. After the foaming agent expands, the softened outer shell expands; when the temperature decreases, the expanded outer shell solidifies. Thus, the second portion of the first insulating layer protrudes from the main body along the first direction.

[0013] In one possible implementation, the glass transition temperature T1 of the thermoplastic polymer is 100°C to 200°C; alternatively, the glass transition temperature T1 of the thermoplastic polymer is 100°C to 120°C.

[0014] In the above technical solution, when the glass transition temperature T1 of the thermoplastic polymer is not greater than 200℃, the heat conducted to the first insulating layer during the cutting process can soften the outer shell of the thermally expanding microspheres. When the glass transition temperature T1 of the thermoplastic polymer is not less than 100℃, the risk of expansion or displacement of the first insulating layer due to softening of the outer shell of the thermally expanding microspheres in other processes can be reduced. Selecting a thermoplastic polymer with a glass transition temperature T1 of 100℃ to 120℃ is beneficial for ensuring more thorough softening of the thermoplastic polymer during the cutting process.

[0015] In one possible implementation, the thermoplastic polymer comprises at least one of the following: polystyrene, polycarbonate, polyvinyl acetate, polymethyl methacrylate, and copolymers of two or more of polystyrene, polycarbonate, polyvinyl acetate, and polymethyl methacrylate. The aforementioned thermoplastic polymer has a suitable softening temperature, facilitating softening upon exposure to heat generated during cutting.

[0016] In one possible implementation, the foaming agent comprises an organic solvent having a boiling point T2 of 100°C to 200°C; alternatively, the boiling point T2 of the organic solvent is 100°C to 120°C.

[0017] In the above technical solution, when the boiling point T2 of the organic solvent is not higher than 200℃, the heat conducted to the first insulating layer during the cutting process can vaporize the organic solvent, thus causing volume expansion. When the boiling point T2 of the organic solvent is not lower than 100℃, the risk of thermal expansion of the microspheres caused by the expansion of the foaming agent in other processes, leading to displacement or expansion of the first insulating layer, can be reduced. Selecting an organic solvent with a boiling point T2 of 100℃ to 120℃ is beneficial for more complete vaporization of the organic solvent during the cutting process.

[0018] In one possible implementation, the organic solvent includes at least one selected from: n-butanol, ethylenediamine, nitromethane, nitrobenzene, cycloheptane, and benzyl alcohol. The aforementioned organic solvent has a suitable boiling point to facilitate expansion upon exposure to the heat generated during cutting.

[0019] In one possible implementation, the volumetric particle size distribution Dv50 of the thermally expandable microspheres in the portion of the first insulating layer near the coating area is 1 μm to 3 μm. Since this portion of the first insulating layer is farther from the cutting tool and less affected by the heat generated during cutting, the thermally expandable microspheres do not expand, or at least some of them do not expand, in this portion. By setting the volumetric particle size distribution Dv50 of the thermally expandable microspheres in the portion of the first insulating layer near the coating area to 1 μm to 3 μm, a suitable distance L is easily obtained.

[0020] In one possible implementation, the first insulating layer further includes an adhesive; optionally, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyimide.

[0021] In the above technical solution, the use of an adhesive facilitates the bonding of the first insulating layer to the surface of the current collector, reducing the risk of the first insulating layer detaching. Furthermore, the adhesive possesses good bonding properties, which helps to improve the adhesion between the first insulating layer and the current collector.

[0022] In one possible implementation, the thickness d1 of the first insulating layer is 15 μm to 45 μm; alternatively, the thickness d1 of the first insulating layer is 20 μm to 30 μm.

[0023] In the above technical solutions, when the thickness d1 of the first insulating layer does not exceed 45 μm, the electrode has a smaller thickness and weight, which is beneficial for reducing the production cost of the electrode and improving the volumetric energy density and gravimetric energy density of the battery cell. When the thickness d1 of the first insulating layer is not less than 15 μm, the first insulating layer includes an appropriate amount of thermally expandable microspheres, which allows the second part of the first insulating layer to protrude by a suitable distance. When the thickness d1 of the first insulating layer is 20 μm to 30 μm, it is beneficial to further balance the protrusion distance of the second part, the production cost of the battery cell, and the energy density.

[0024] In one possible implementation, the first insulating layer further includes a second portion disposed on a portion of the surface of the tab and extending from the first portion along the first direction. This reduces the risk of the tab colliding with an electrode of opposite polarity.

[0025] 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 material base layer and a metal layer located on at least one surface of the polymer material base layer; optionally, the current collector comprises aluminum foil. This facilitates the selection of a suitable current collector according to actual needs. When the current collector comprises aluminum foil, the electrode is a positive electrode, which helps reduce the risk of overlap between the positive and negative electrodes and improves the reliability of the battery cell.

[0026] In a second aspect, a method for preparing an electrode is provided, comprising: providing a current collector; coating an active material in a first region of the current collector to form an active material layer; coating an insulating slurry in a second region of the current collector to form a first insulating layer, the insulating slurry comprising thermally expandable microspheres, a binder, and a solvent, wherein, based on the total mass of the insulating slurry, the mass percentage A of the thermally expandable microspheres is ≥15wt%, the mass percentage B of the binder is ≥15wt%, the expansion temperature of the thermally expandable microspheres is ≥100℃, and the thickness d1 of the first insulating layer is ≥10μm; and cutting the current collector having the first insulating layer disposed along a cutting line, at least a portion of the cutting line being disposed in the second region.

[0027] In the above technical solution, during the process of cutting the current collector with the first insulating layer along the cutting line, the thermally expanding microspheres in the first insulating layer expand under the heat generated by the cutting. The area of ​​the first insulating layer near the cutting line protrudes relative to the current collector. After the temperature drops, the protruding part solidifies, thereby forming the electrode sheet in the embodiment of this application. In addition, by reasonably setting the mass ratio of the adhesive in the insulating slurry, the risk of the first insulating layer falling off can be reduced, so that the first insulating layer is coated on the surface of the current collector and expands during the cutting process; by reasonably setting the mass ratio of the thermally expanding microspheres in the insulating slurry, the thermally expanding microspheres have an appropriate content, which facilitates the first insulating layer to expand beyond the current collector by an appropriate distance; by reasonably setting the expansion temperature of the thermally expanding microspheres, the risk of the thermally expanding microspheres expanding before cutting can be reduced, thereby reducing the risk of cutting the expanded first insulating layer during the cutting process due to premature expansion of the first insulating layer.

[0028] In one possible implementation, the thermally expandable microspheres have a core-shell structure, wherein the outer shell of the core-shell structure is made of a thermoplastic polymer, and the inner core of the core-shell structure is made of a foaming agent.

[0029] In one possible implementation, the glass transition temperature T1 of the thermoplastic polymer is 100°C to 200°C; alternatively, the glass transition temperature T1 of the thermoplastic polymer is 100°C to 120°C.

[0030] In one possible implementation, the volumetric particle size distribution Dv50 of the thermally expanded microspheres is 1 μm to 3 μm.

[0031] In the above technical solution, by reasonably setting the particle size of the thermally expandable microspheres, it is easy for the microspheres to expand into a spherical shape when heated, thereby facilitating the protrusion of the first insulating layer from the main body. Furthermore, when the volumetric particle size distribution Dv50 of the thermally expandable microspheres is not less than 1 μm, the agglomeration of the microspheres in the insulating slurry during the preparation process can be reduced, which is beneficial for obtaining a uniform first insulating layer. This facilitates the uniform expansion of the first insulating layer, and the distance between different positions of the first insulating layer and the current collector is relatively uniform. When the volumetric particle size distribution Dv50 of the thermally expandable microspheres does not exceed 3 μm, it is easier for the microspheres to expand when subjected to the heat generated by cutting, which is beneficial for the expansion of the first insulating layer.

[0032] In one possible implementation, the thermoplastic polymer includes at least one of the following: polystyrene, polycarbonate, polyvinyl acetate, polymethyl methacrylate, and copolymers of two or more of polystyrene, polycarbonate, polyvinyl acetate, and polymethyl methacrylate.

[0033] In one possible implementation, the foaming agent comprises an organic solvent having a boiling point T2 of 100°C to 200°C; alternatively, the boiling point T2 of the organic solvent is 100°C to 120°C.

[0034] In one possible implementation, the organic solvent includes at least one selected from: n-butanol, ethylenediamine, nitromethane, nitrobenzene, cycloheptane, and benzyl alcohol. The aforementioned organic solvent has a suitable boiling point to facilitate expansion upon exposure to the heat generated during cutting.

[0035] In one possible implementation, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyimide.

[0036] In one possible implementation, based on the total mass of the insulating slurry, the mass ratio A:B:C of the thermally expanded microspheres, the binder, and the solvent satisfies: 5wt%~10wt%: 5wt%~10wt%: 80wt%~90wt%.

[0037] By rationally setting the mass ratio of thermally expandable microspheres, binder, and solvent in the insulating slurry, a slurry with suitable viscosity and fluidity can be obtained, and after coating, the first insulating layer has suitable expansion and adhesion properties.

[0038] In one possible implementation, the coating width k1 of the first insulating layer is 3mm to 6mm along a first direction, where the first direction is the arrangement direction of the first region and the second region.

[0039] In the above technical solution, when the coating width k1 of the first insulating layer does not exceed 6mm, the electrode has a smaller thickness and weight, which is beneficial to reduce the production cost of the electrode and improve the volumetric energy density and gravimetric energy density of the battery cell; when the coating width k1 of the first insulating layer is not less than 3mm, it is convenient to make the first insulating layer protrude a suitable distance relative to the current collector.

[0040] In one possible implementation, the thickness d1 of the first insulating layer is 15 μm to 45 μm; alternatively, the thickness d1 of the first insulating layer is 20 μm to 30 μm.

[0041] Thirdly, a battery cell is provided, comprising an electrode as described in the first aspect and any possible implementation thereof, and / or an electrode prepared by a method as described in the second aspect and any possible implementation thereof.

[0042] Fourthly, a battery is provided, comprising the battery cell described in the third aspect.

[0043] Fifthly, an electrical device is provided, comprising the battery described in the fourth aspect. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the electrode sheet before the processing of the electrode tab according to an embodiment of this application;

[0046] Figure 2 This is a schematic diagram of an electrode sheet according to an embodiment of this application;

[0047] Figure 3 for Figure 2 A cross-sectional view along the AA direction;

[0048] Figure 4 for Figure 2 A cross-sectional view along the BB direction;

[0049] Figure 5 This is a schematic diagram of the thermally expandable microspheres before expansion according to an embodiment of this application;

[0050] Figure 6 This is a schematic diagram of the thermally expandable microspheres according to an embodiment of this application after expansion;

[0051] Figure 7This is a flowchart of a method for preparing an electrode sheet according to an embodiment of this application;

[0052] Figure 8 This is a schematic diagram of a current collector according to an embodiment of this application;

[0053] Figure 9 A schematic diagram of a current collector coated with an active material layer according to an embodiment of this application;

[0054] Figure 10 This is a schematic diagram of a current collector coated with a second insulating layer according to an embodiment of this application;

[0055] Figure 11 This is a schematic diagram illustrating the current collector of the cutting line according to an embodiment of this application;

[0056] Figure 12 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0057] Figure 13 This is a schematic diagram of a battery according to an embodiment of this application;

[0058] Figure 14 This is a schematic diagram of an electrical device according to an embodiment of this application.

[0059] Figure label:

[0060] 1: Electrode; 124: Cutting line; 10: Current collector; 11: Active material layer; 121: First insulating layer; 122: Second insulating layer; 101: Main body; 102: Tab; 1011: Coating area; 1012: Transition area; 1011a: End face; 1221: First part; 1222: Second part; 2: Thermally expandable microsphere; 21: Outer shell; 22: Core. Detailed Implementation

[0061] The embodiments of the electrode sheet and its preparation method, battery cell, battery, and power-consuming device of this application are disclosed in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0062] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0063] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0064] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0065] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0066] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may include or include other components not listed.

[0067] Unless otherwise specified, the term "and / or" is inclusive in this application. For example, the phrase "A and / or B" means "A, B, or both A and B". More specifically, the condition "A and / or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0068] The development of battery technology must consider multiple design factors simultaneously, such as energy density, cycle life, discharge capacity, charge / discharge rate, and reliability. The design of the electrodes within a single battery cell is crucial to its reliability. Electrodes typically consist of a current collector and active material layers and insulating layers coated on different areas of the current collector. After coating the current collector with the appropriate active material and insulating layers, it needs to be cut to create the tabs. During this cutting process, dust and burrs are easily generated. These burrs may cause the electrode to overlap with an electrode of opposite polarity, leading to a short circuit.

[0069] In some processing methods, the insulating layer coated on the current collector is a ceramic coating to reduce burrs generated during the cutting process. However, this method only reduces the number of burrs; burrs will still exist after cutting. These burrs may cause the electrode to overlap with the electrode of opposite polarity, resulting in adverse effects. Furthermore, the end face of the current collector is exposed after cutting, posing a risk of overlap with the electrode of opposite polarity, which could lead to a short circuit in the battery cell and negatively impact battery reliability.

[0070] In view of this, this application provides an electrode. In this electrode, an active material layer and a first insulating layer are disposed on the current collector, the first insulating layer including a portion extending beyond the current collector at a certain distance. In this way, the end face of the current collector exposed after cutting can be prevented from overlapping with the electrode of opposite polarity, reducing the risk of short circuit and improving the reliability of the battery cell.

[0071] [Extreme Film]

[0072] Figure 1 This is a schematic diagram of the electrode sheet before the electrode tab is processed according to an embodiment of this application. Figure 2 This is a schematic diagram of an electrode sheet according to an embodiment of this application. Figure 3 for Figure 2 A cross-sectional view along the AA direction. Figure 4 for Figure 2 A cross-sectional view along the BB direction.

[0073] Combination Figure 1 and Figure 2 As shown, Figure 1 This is a schematic diagram of the electrode sheet before the tab is processed. Figure 2This is a schematic diagram showing the electrode after the tabs have been processed. (Example:) Figure 1 As shown, the black dashed line 124 is the cutting line for cutting the tabs. After cutting along the cutting line 124, the result is as follows: Figure 2 Electrode 1 is shown.

[0074] Combination Figures 1 to 4 As shown, the electrode 1 includes a current collector 10, an active material layer 11, and a first insulating layer 121.

[0075] The current collector 10 includes a main body 101 and a tab 102, wherein the tab 102 extends from a first end of the main body 101, and the first end of the main body 101 is one end of the main body 101 along a first direction.

[0076] 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... Figure 2 y direction in .

[0077] The main body 101 includes a coating area 1011 and a transition area 1012, with the transition area 1012 disposed between the coating area 1011 and the tab 102.

[0078] An active material layer 11 is disposed on the surface of the coating area 1011. For example, such as... Figure 3 and Figure 4 As shown, the active material layer 11 is disposed on two surfaces of the current collector 10 along its thickness direction. The thickness direction of the current collector 10 can be... Figure 3 and Figure 4 The z-direction is shown.

[0079] In some embodiments, the active material layer 11 may be disposed on one of the two surfaces of the current collector 10 in the thickness direction.

[0080] The first insulating layer 121 includes a first portion 1211 and a second portion 1212. The first portion 1211 is disposed on the surface of the transition region 1012, and the second portion 1212 extends from the first portion 1211 along a first direction and is disposed in the area outside the tab 102.

[0081] The second part 1212 extends from the first part 1211 along the first direction and is disposed in the area outside the tab 102. This can mean that the second part 1212 is not disposed on the surface of the current collector 10, that is, the second part 1212 is not disposed on the surface of the transition region 1012 and the surface of the tab 102.

[0082] Along the first direction, the second portion 1212 extends beyond the main body 101 by a minimum distance L of 10μm to 80μm, for example, L is 10μm, 20μm, 40μm, 45μm, 50μm, 55μm, 60μm, 70μm, 80μm or any value within the above range. The second portion 1212 of the first insulating layer 121 protrudes relative to the main body 101 along the first direction. In this way, after the current collector 10 is cut along the cutting line 124, the second portion 1212 can prevent the exposed end face 1011a of the current collector 10 after cutting and the burrs generated by cutting from overlapping with the electrode of opposite polarity. This can reduce the risk of short circuits caused by the overlap of the end face 1011a and the burrs with the electrode of opposite polarity, which is beneficial to improving the reliability of the battery cell.

[0083] When the minimum distance L is not less than 10 μm, the second part 1212 can block the burrs generated by cutting and the contact between the end face 1011a and the electrode with opposite polarity; when the minimum distance L does not exceed 80 μm, it is beneficial to reduce the space occupied by the second part 1212 and improve the volumetric energy density of the battery cell.

[0084] This application provides an electrode 1, which includes a current collector 10, an active material layer 11, and a first insulating layer 121. The current collector 10 includes a main body 101 and a tab 102, with the tab 102 extending from a first end of the main body 101, which is one end of the main body 101 along a first direction. The main body 101 includes a coating area 1011 and a transition area 1012, with the transition area 1012 disposed between the coating area 1011 and the tab 102. The coating area 1011 is provided with the active material layer 11. Thus, by providing the transition area 1012, during the cutting of the tab 102, the cutting tool can maintain a certain distance from the active material layer 11, which can reduce the shedding of the active material layer 11. The first insulating layer 121 includes a first portion 1211 and a second portion 1212. The first portion 1211 is disposed on the surface of the transition region 1012, and the second portion 1212 extends from the first portion 1211 along a first direction and is suspended. Along the first direction, the second portion 1212 extends beyond the main body 101 by a minimum distance L of 10μm to 80μm. The second portion 1212 prevents contact between the end face 1011a and the burrs generated during cutting with electrodes of opposite polarity, thus reducing the risk of short circuits in the battery cell and further improving the reliability of the battery cell.

[0085] In some embodiments, the minimum distance L by which the second portion 1212 extends beyond the main body 101 along the first direction is 50 μm to 60 μm. For example, L can be 50 μm, 53 μm, 55 μm, 60 μm, or any value within the aforementioned range. This is beneficial for further improving the blocking effect of the second portion 1212.

[0086] After cutting, the distance by which the second part 1212 extends beyond the main body 101 is not exactly the same and may vary. For example, in some positions, the second part 1212 extends beyond the main body 101 by 50 μm, in others by 55 μm, and in still others by 60 μm.

[0087] In some embodiments, the first insulating layer 121 comprises a thermally expanding material.

[0088] Thermally expanding materials refer to materials that can expand when subjected to a certain level of heat.

[0089] In this embodiment, a significant amount of heat is generated during the cutting of the current collector 10, which is provided with the first insulating layer 121. Before cutting the current collector 10, the first insulating layer 121 does not include any portion protruding from the current collector 10. During the cutting process, since the first insulating layer 121 includes a thermally expanding material, the material expands under the heat generated during cutting, allowing the first insulating layer 121 to extend beyond the main body 101 of the current collector 10 along a first direction, thereby forming a second portion 1212. The inclusion of the thermally expanding material facilitates the preparation of the second portion 1212 of the first insulating layer 121.

[0090] Figure 5 This is a schematic diagram of the thermally expandable microspheres before expansion according to an embodiment of this application. Figure 6 This is a schematic diagram of the expanded thermally expandable microspheres according to an embodiment of this application. In some embodiments, combined with Figure 5 and Figure 6 As shown, the thermal expansion material includes thermal expansion microspheres 2, which have a core-shell structure. The outer shell 21 of the core-shell structure is made of a thermoplastic polymer, and the core 22 of the core-shell structure is made of a foaming agent.

[0091] Thermally expandable microspheres can refer to particles with a core-shell structure, consisting of a thermoplastic outer shell and a foaming agent as the core.

[0092] Thermoplastic polymers can refer to polymers that soften when heated, solidify when cooled, and can be softened again.

[0093] A foaming agent can be defined as a substance that expands in volume or decomposes to produce gas when heated. For example, foaming agents include organic solvents, which vaporize and expand in volume upon reaching their boiling point.

[0094] The thermally expanding material can be thermally expanding microspheres 2, or other materials with thermal expansion properties. For example, the thermally expanding material can be a shape memory polymer material.

[0095] Optionally, the first insulating layer 121 includes thermally expandable microspheres 2.

[0096] In this embodiment, under the heat generated during cutting, the foaming agent, which is the core 22, expands, and the thermoplastic polymer, which is the outer shell 21, softens. After the foaming agent expands, the softened outer shell 21 expands; when the temperature decreases, the expanded outer shell 21 solidifies. Thus, the second portion 122 of the first insulating layer 121 extends beyond the main body 101 along the first direction.

[0097] In some embodiments, the glass transition temperature T1 of the thermoplastic polymer is 100°C to 200°C, for example, T1 is 100°C, 110°C, 120°C, 200°C or any value within the above range.

[0098] When the glass transition temperature T1 of the thermoplastic polymer is not greater than 200°C, the heat conducted to the first insulating layer 121 during the cutting process can soften the outer shell 21 of the thermally expanding microspheres 2. When the glass transition temperature T1 of the thermoplastic polymer is not less than 100°C, the risk of displacement of the first insulating layer 121 due to softening of the outer shell 21 of the thermally expanding microspheres 2 in other processes can be reduced. For example, when hot-pressing the electrode assembly formed by the electrode sheet 1, since the glass transition temperature T1 of the thermoplastic polymer is not less than 100°C, the outer shell 21 of the thermally expanding microspheres 2 will not soften during the hot-pressing process, which can reduce the risk of the first insulating layer 121 shifting on the current collector 10 due to softening of the outer shell 21. As another example, during the process of coating the first insulating layer 121 and drying the first insulating layer 121 in an oven, the outer shell 21 will not soften, which can reduce the risk of cutting the expanded first insulating layer 121 during the cutting process due to premature expansion of the first insulating layer 121.

[0099] Optionally, the glass transition temperature T1 of the thermoplastic polymer is 100℃~120℃. Selecting a thermoplastic polymer with a glass transition temperature T1 of 100℃~120℃ is beneficial for the thermoplastic polymer to soften more fully during the cutting process.

[0100] In some embodiments, the thermoplastic polymer includes at least one of the following: polystyrene, polycarbonate, polyvinyl acetate, polymethyl methacrylate, and copolymers of two or more of polystyrene, polycarbonate, polyvinyl acetate, and polymethyl methacrylate. The above-mentioned thermoplastic polymers have suitable softening temperatures to facilitate softening upon exposure to heat generated during cutting.

[0101] For example, thermoplastic polymers include at least one of polystyrene, polycarbonate, polyvinyl acetate, and polymethyl methacrylate. As another example, thermoplastic polymers include polystyrene-polycarbonate copolymers.

[0102] The thermoplastic polymers used in the embodiments of this application include, but are not limited to, those whose glass transition temperature meets the above range.

[0103] In some embodiments, the foaming agent includes an organic solvent with a boiling point T2 of 100°C to 200°C, for example, T2 is 100°C, 110°C, 120°C, 200°C or any value within the above range.

[0104] In the above technical solution, when the boiling point T2 of the organic solvent is not higher than 200°C, the heat conducted to the first insulating layer 121 during the die-cutting process can vaporize the organic solvent and thus expand its volume; when the boiling point T2 of the organic solvent is not lower than 100°C, the risk of thermal expansion of the microspheres 2 caused by the expansion of the foaming agent in other processes, which in turn causes the first insulating layer 121 to shift or expand, can be reduced.

[0105] Optionally, the boiling point T2 of the organic solvent is 100℃~120℃. This allows the organic solvent to vaporize more completely during the cutting process.

[0106] In some embodiments, the organic solvent includes at least one selected from n-butanol, ethylenediamine, nitromethane, nitrobenzene, cycloheptane, and benzyl alcohol. The aforementioned organic solvents have suitable boiling points to facilitate expansion upon exposure to the heat generated during cutting.

[0107] In some embodiments, the volumetric particle size distribution Dv50 of the thermally expanded microspheres 2 in the portion of the first insulating layer 121 near the coating area 1011 is 1 μm to 3 μm, for example, 1 μm, 2 μm, 3 μm or any value within the above range.

[0108] The portion of the first insulating layer 121 near the coating area 1011 is farther from the cutting tool and is less affected by the heat generated during cutting. In this portion of the first insulating layer 121 near the coating area 1011, the thermally expandable microspheres 2 do not expand, or at least some of them do not expand. By setting the volumetric particle size distribution Dv50 of the thermally expandable microspheres 2 in the portion of the first insulating layer 121 near the coating area 1011 to be 1μm to 3μm, a suitable distance L can be easily obtained.

[0109] In some embodiments, the first insulating layer 121 further includes an adhesive. The adhesive facilitates the adhesion of the first insulating layer 121 to the surface of the current collector 10, reducing the risk of the first insulating layer 121 falling off.

[0110] Optionally, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyimide. The aforementioned adhesives have good bonding properties, facilitating improved adhesion between the first insulating layer 121 and the current collector 10.

[0111] In some embodiments, the thickness d1 of the first insulating layer 121 is 15 to 45 μm, for example, d1 is 15 μm, 20 μm, 30 μm, 40 μm, 45 μm or any value within the above range.

[0112] When the thickness d1 of the first insulating layer does not exceed 45 μm, the electrode 1 has a smaller thickness and weight, which is beneficial to reduce the production cost of the electrode 1 and improve the volumetric energy density and gravimetric energy density of the battery cell; when the thickness d1 of the first insulating layer 121 is not less than 15 μm, the first insulating layer 121 includes an appropriate amount of thermally expandable microspheres, which can make the second part of the first insulating layer 121 extend beyond the main body 101 by a suitable distance.

[0113] The thickness d1 of the first insulating layer 122 can be measured by taking an image of the electrode 1 along the thickness direction of the electrode 1 using a scanning electron microscope (SEM), and measuring the thickness d1 of the first insulating layer 121 based on the obtained image.

[0114] The thickness d1 of the first insulating layer 121 can be the average thickness of the first insulating layer 121. For example, the thickness d1 is the average of the maximum and minimum dimensions.

[0115] Optionally, the thickness d1 of the first insulating layer is 20–30 μm. This helps to further balance the distance of the second part beyond the main body 101, the production cost of the battery cell, and the energy density.

[0116] In some embodiments, the first insulating layer 121 further includes a third portion 1213, which is disposed on a portion of the surface of the tab 102 and extends from the first portion 121 along a first direction. This reduces the risk of the tab 102 colliding with an electrode of opposite polarity.

[0117] The third part 1213 is different from the second part 1212. The third part 1213 is located on part of the surface of the tab 102, while the second part 1212 is not located on the surface of the tab 102.

[0118] Optionally, the first insulating layer 121 further includes a fourth portion (not shown in the figure). The fourth portion is suspended and extends from the third portion 1213 along a second direction. The second direction is perpendicular to the first direction and parallel to the plane containing the current collector 10.

[0119] When the electrode 1 includes multiple tabs 102, the second direction can be the arrangement direction of the multiple tabs 102. For example, as Figure 2 As shown, the second direction is the x-direction.

[0120] In some embodiments, the current collector 10 includes a metal foil or a composite current collector; optionally, the metal foil includes aluminum foil or copper foil; 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; optionally, the current collector includes aluminum foil. This facilitates the selection of a suitable current collector 10 according to actual needs. When the current collector 10 includes aluminum foil, the electrode 1 is a positive electrode, which helps reduce the risk of overlap between the positive and negative electrodes and improves the reliability of the battery cell.

[0121] The above text combined Figures 1 to 6 The technical solution for the electrode sheet has been explained. The following section will combine... Figure 7 The preparation method of the electrode is described. The parts corresponding to the electrode can be referred to above, and will not be repeated here.

[0122] [Preparation methods for electrode sheets]

[0123] Figure 7 This is a flowchart illustrating a method for preparing an electrode according to an embodiment of this application. Method 200 can be used to prepare the electrode 1 in the above embodiment. Method 200 includes the following steps.

[0124] Step 210, provide current collector 10.

[0125] Figure 8 This is a schematic diagram of a current collector according to an embodiment of this application. For example, such as... Figure 8 As shown, the current collector 10 is in the shape of a sheet or a rectangle. The shape and size of the current collector 10 can be set according to actual needs, and the embodiments of this application include, but are not limited to, these.

[0126] Step 220: Coat the first region of the current collector 10 with an active material to form an active material layer 11.

[0127] Figure 9 This is a schematic diagram of a current collector coated with an active material layer according to an embodiment of this application. Figure 9 As shown, an active material is coated in the first region of the current collector 10 to obtain a current collector 10 with an active material layer 11.

[0128] The first region of the current collector 10 can be a region set according to actual needs. In the embodiment of this application, the first region corresponds to the coating area 1011 of the main body portion 101 of the electrode 1.

[0129] Step 230: Apply insulating paste to the second region of the current collector 10 to form a first insulating layer 121.

[0130] The insulating slurry includes thermally expandable microspheres 2, a binder, and a solvent. The thermally expandable microspheres can expand when exposed to a certain amount of heat; the binder can bond the thermally expandable microspheres to the surface of the second region of the current collector 10; the solvent can give the insulating slurry suitable viscosity and flowability, facilitating the coating of the insulating slurry.

[0131] Based on the total mass of the insulating slurry, the mass percentage of thermally expanding microspheres A is ≥ 15wt%, the mass percentage of binder B is ≥ 15wt%, and the expansion temperature of thermally expanding microspheres 2 is greater than or equal to 100℃.

[0132] By reasonably setting the mass ratio of the adhesive in the insulating slurry, the risk of the first insulating layer 121 falling off can be reduced, so that the first insulating layer 121 is coated on the surface of the current collector 10 and expands during the cutting process; by reasonably setting the mass ratio of the thermally expandable microspheres 2 in the insulating slurry, the thermally expandable microspheres 2 have a suitable content, so that the first insulating layer 121 expands beyond the current collector 10 by a suitable distance.

[0133] The thickness d1 of the first insulating layer 121 is greater than 10 μm, which makes it easier for the first insulating layer 121 to expand beyond the current collector 10 by a suitable distance.

[0134] The expansion temperature of the thermally expandable microsphere 2 can refer to the glass transition temperature of the outer shell 21 of the thermally expandable microsphere 2, and / or the boiling point of the core 22 of the thermally expandable microsphere 2.

[0135] By reasonably setting the expansion temperature of the thermal expansion microspheres 2, the risk of the thermal expansion microspheres 2 expanding before cutting can be reduced, thereby reducing the risk of the expanded first insulating layer 121 being cut during the cutting process due to the premature expansion of the first insulating layer 121.

[0136] Figure 10 This is a schematic diagram of a current collector coated with a first insulating layer according to an embodiment of this application. Figure 10 As shown, an insulating paste is coated on the second region of the current collector 10 to obtain a current collector 10 with a first insulating layer 121.

[0137] The size of the second region can be set according to actual needs. In the embodiments of this application, the second region corresponds to the transition region 1012 of the main body portion 101 of the electrode 1 and the region of the tab 102 where the first insulating layer 121 is provided.

[0138] Step 240: Cut the current collector 10 with the first insulating layer 121 along the cutting line 124, with at least a portion of the cutting line 124 located in the second region.

[0139] Figure 11 This is a schematic diagram illustrating the current collector for the cutting line according to an embodiment of this application. Figure 11As shown, the current collector 10 is cut along the cutting line 124, thereby obtaining... Figures 2 to 4 Electrode 1 is shown.

[0140] During the cutting process of the current collector 10 along the cutting line 124, the area of ​​the first insulating layer 121 near the cutting line 124 receives more heat, causing the thermally expanding microspheres 2 in the first insulating layer 121 to expand, resulting in at least a portion of the first insulating layer 121 extending beyond the current collector 10. After the temperature decreases, the portion of the first insulating layer 121 extending beyond the current collector 10 solidifies, thus preventing the exposed end face of the current collector from colliding with an electrode of opposite polarity. The electrode 1 in this embodiment can be prepared by method 200, reducing the risk of short circuits caused by the electrode 1 colliding with an electrode of opposite polarity or other electrode contacts, thereby improving the reliability of the battery cell.

[0141] In some embodiments, the thermally expandable microspheres have a core-shell structure, wherein the outer shell of the core-shell structure is made of a thermoplastic polymer, and the inner core of the core-shell structure is made of a foaming agent.

[0142] In some embodiments, the glass transition temperature T1 of the thermoplastic polymer is 100°C to 200°C; optionally, the glass transition temperature T1 of the thermoplastic polymer is 100°C to 120°C.

[0143] In some embodiments, the volumetric particle size distribution Dv50 of the thermally expanded microspheres 2 is 1 μm to 3 μm, for example, 1 μm, 2 μm, 3 μm.

[0144] Volumetric particle size distribution Dv50 refers to the particle size corresponding to a sample when the cumulative volumetric distribution percentage reaches 50%.

[0145] The volumetric particle size distribution (Dv50) can be determined using a particle size analyzer-laser diffraction method. Specifically, refer to standard GB / T19077-2016, using a laser diffraction scattering particle size analyzer, and measure according to the manufacturer's instructions. For example, before preparing the slurry for the second insulating layer, take an appropriate amount of thermoplastic polymer and test the average volumetric particle size of the material using a Malvern 2000 (MasterSizer 2000) laser particle size analyzer. Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20 ml of deionized water, and simultaneously incubate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009.

[0146] By rationally setting the particle size of the thermally expandable microspheres 2, it is easier for them to expand into a spherical shape when heated, thereby facilitating the formation of the second part 1212 of the first insulating layer 121. Furthermore, when the volumetric particle size distribution Dv50 of the thermally expandable microspheres 2 is not less than 1 μm, the agglomeration of the thermally expandable microspheres 2 in the insulating slurry during the preparation process can be reduced, which is beneficial for obtaining a uniform first insulating layer 121. This facilitates the uniform expansion of the first insulating layer 121, and the distance L of the first insulating layer 121 extending beyond the current collector 10 at different positions is relatively uniform. When the volumetric particle size distribution Dv50 of the thermally expandable microspheres 2 does not exceed 3 μm, it is easier for the thermally expandable microspheres 2 to expand when subjected to the heat generated during cutting, which is beneficial for the expansion of the first insulating layer 121.

[0147] The volumetric particle size distribution Dv50 of thermally expandable microspheres 2 can refer to the volumetric particle size distribution Dv50 before thermally expandable microspheres 2 expand.

[0148] In some embodiments, the thermoplastic polymer includes at least one of the following: polystyrene, polycarbonate, polyvinyl acetate, polymethyl methacrylate, and copolymers of two or more of polystyrene, polycarbonate, polyvinyl acetate, and polymethyl methacrylate.

[0149] In some embodiments, the foaming agent includes an organic solvent with a boiling point T2 of 100°C to 200°C; optionally, the boiling point T2 of the organic solvent is 100°C to 120°C.

[0150] In some embodiments, the organic solvent includes at least one of n-butanol, ethylenediamine, nitromethane, nitrobenzene, cycloheptane, and benzyl alcohol.

[0151] The embodiments of this application include, but are not limited to, the above-mentioned organic solvents, as long as their boiling points meet the above-mentioned range.

[0152] In some embodiments, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyimide.

[0153] The above adhesives are examples, and the embodiments of this application include, but are not limited to, those.

[0154] In some embodiments, based on the total mass of the insulating slurry, the mass ratio A:B:C of the thermally expanded microspheres 2, binder and solvent satisfies: 5wt%~10wt%: 5wt%~10wt%: 80wt%~90wt%.

[0155] For example, A:B:C is 5wt%:5wt%:90wt%. Another example is A:B:C is 10wt%:10wt%:80wt%, or any value within the above range.

[0156] By rationally setting the mass ratio of thermally expanding microspheres, binder and solvent in the insulating slurry, a slurry with suitable viscosity and fluidity can be obtained, and after coating, the first insulating layer 121 has suitable expansion and adhesion properties.

[0157] In some embodiments, the coating width k1 of the first insulating layer 121 is 3mm to 6mm along the first direction, and the first direction is the arrangement direction of the first region and the second region. For example, k1 is 3mm, 4mm, 5mm, 5.5mm, 6mm or any value within the above range.

[0158] The coating width k1 of the first insulating layer 121 can also be the dimension of the second region in the first direction. As an example, such as... Figure 10 and Figure 11 As shown, the current collector 10 is rectangular in shape, and the first direction can be the width direction of the current collector 10, that is, the y direction in the figure.

[0159] When the coating width k1 of the first insulating layer 121 does not exceed 6 mm, the electrode 1 has a smaller thickness and weight, which is beneficial to reduce the production cost of the electrode 1 and improve the volumetric energy density and gravimetric energy density of the battery cell; when the coating width k1 of the first insulating layer 121 is not less than 3 mm, it is convenient to make the first insulating layer 121 protrude a suitable distance relative to the current collector 10.

[0160] Optionally, the coating width k1 of the first insulating layer 121 can be determined according to the size of the current collector 10.

[0161] In some embodiments, the thickness d1 of the first insulating layer 121 is 15 μm to 45 μm; optionally, the thickness d1 of the first insulating layer 121 is 20 to 30 μm.

[0162] The thickness d1 of the first insulating layer 121 can be the thickness of the insulating slurry after coating and drying. Here, the thickness d1 can refer to the thickness on one side of the current collector 10. In some embodiments, both surfaces of the current collector 10 along the thickness direction are coated with insulating slurry, and the total thickness of the first insulating layer 121 is 2d1, which is 30μm to 90μm.

[0163] Optionally, in step 240, the laser processing tool is controlled to cut the current collector 10 with the first insulating layer 121 along the cutting line 124.

[0164] [Positive electrode plate]

[0165] In this embodiment, the electrode 1 can be a positive electrode. The positive electrode includes a positive current collector and a positive electrode film layer disposed on the positive current collector.

[0166] The positive electrode current collector can be a metal foil or a composite current collector. For example, the positive electrode current collector can be an aluminum foil.

[0167] Composite current collectors may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0168] The positive electrode film includes a positive electrode active material. This positive electrode active material can be any known battery-grade positive electrode active material. For example, it could be lithium iron phosphate, ternary materials, or lithium-rich manganese-based materials.

[0169] The positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0170] The positive electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0171] [Negative electrode plate]

[0172] In this embodiment, the electrode 1 can be a negative electrode. The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0173] The negative electrode current collector can be a metal foil or a composite current collector. The negative electrode current collector can be copper foil. Composite current collectors can be formed by depositing metallic materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) onto a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0174] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be any negative electrode active material known in the art for use in batteries. 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, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional 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.

[0175] The negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0176] [Electrolytes]

[0177] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0178] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0179] The electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0180] Solvents may include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0181] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and performance additives that can improve certain battery performance, such as performance additives that improve battery overcharge performance, battery high temperature or low temperature performance, etc.

[0182] [Isolation membrane]

[0183] The separator is used to separate the positive electrode and the negative electrode. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0184] The material of the separator can be selected from 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; there are no particular restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different; there are no particular restrictions.

[0185] Positive electrode, negative electrode and separator can be made into electrode assembly by winding process or stacking process.

[0186] [Battery cell]

[0187] This application provides a battery cell, including the electrode 1 in the above embodiments, and / or the electrode prepared by the method in the above embodiments.

[0188] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. The battery cell can be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, a magnesium-ion battery, etc.

[0189] Figure 10 This is a schematic diagram of a battery cell according to an embodiment of this application. For example, such as... Figure 10 As shown, the battery cell 3 is a square battery cell. The battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33 disposed in the housing 31.

[0190] The electrode assembly 33 can be manufactured by a winding process or a stacking process from a positive electrode sheet, a negative electrode sheet, and a separator. In some embodiments, the positive electrode sheet is electrode sheet 1 in the embodiments of this application.

[0191] End cap assembly 32 includes electrode terminals 322, such as... Figure 10 As shown, 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.

[0192] The battery cell 3 also includes a current collector 34, which is used to connect the tab 331 of the electrode assembly 33 and the electrode terminal 322. For example, in the case that the electrode 1 in this embodiment is a positive electrode, one current collector 34 is used to connect the positive electrode tab (which may also be the tab 102 of the electrode 1) and the positive electrode terminal, and another current collector 34 is used to connect the negative electrode tab and the negative electrode terminal.

[0193] In some embodiments, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0194] [Battery]

[0195] This application provides a battery, including the battery cell described in the above embodiments. Figure 11 This is a schematic diagram of a battery according to an embodiment of this application. Figure 11 As shown, battery 5 may include multiple battery cells (not shown in the figure).

[0196] Battery cells 3 can be directly assembled into battery 5, or they can be first assembled into battery modules, and then multiple battery modules can be assembled into battery 5.

[0197] [Electrical appliances]

[0198] This application provides an electrical device, including the battery described in the above embodiments.

[0199] Figure 12 This is a schematic diagram of an electrical device according to an embodiment of this application. Figure 12 As shown, this application provides an electrical device 6, which includes the battery in the above embodiment.

[0200] Alternatively, the electrical device may also be an energy storage device, a lighting device, a spacecraft, etc., as is the case in the embodiments of this application.

[0201] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0202] [Example]

[0203] Example 1

[0204] The electrode in Example 1 has the following characteristics: Figure 2-4 The structure shown. In Embodiment 1, the minimum distance L from the second portion 1212 of the first insulating layer 121 beyond the main body portion 1011 is 50 μm.

[0205] The insulating slurry used to prepare the first insulating layer 121 includes thermally expandable microspheres 2, a binder, and a solvent. Based on the total mass of the insulating slurry, the mass ratio of the three components A:B:C satisfies 5wt%:5wt%:90wt%. The thermally expandable microspheres 2 have a polystyrene outer shell with a glass transition temperature T1 of 100℃ and a cycloheptane core with a boiling point T2 of 118.5℃. The binder is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone.

[0206] The coating width k1 of the first insulating layer 121 is 3 mm, and the thickness d1 of the first insulating layer 121 is 20 μm.

[0207] Example 2

[0208] The difference between Example 2 and Example 1 is that, based on the total mass of the insulating slurry, the mass ratio A:B:C of the thermally expanded microspheres 2, binder, and solvent satisfies 10wt%:10wt%:80wt%. Correspondingly, the minimum distance L of the second portion 1212 of the first insulating layer 121 extending beyond the main body 1011 is 60μm.

[0209] Example 3

[0210] The difference between Example 3 and Example 1 lies in the material of the thermally expandable microspheres. In Example 3, polymethyl methacrylate is used as the outer shell, with a glass transition temperature T1 of 120°C; nitromethane is used as the core, with a boiling point T2 of 101°C. Correspondingly, the minimum distance L from the second portion 1212 of the first insulating layer 121 beyond the main body 1011 is 60 μm.

[0211] Example 4

[0212] The difference between Example 4 and Example 1 is that the coating width k1 of the first insulating layer 121 is different. In Example 4, k1 is 6 mm. Correspondingly, the distance L from the second portion 1212 of the first insulating layer 121 beyond the main body portion 1011 is 50 μm.

[0213] Example 5

[0214] The difference between Example 5 and Example 1 is that the thickness d1 of the first insulating layer 121 is different.

[0215] Example 6

[0216] The difference between Example 6 and Example 5 lies in the material of the thermally expandable microspheres. In Example 6, polystyrene is used as the outer shell, with a glass transition temperature T1 of 200°C (polystyrene with different molecular weights has different glass transition temperatures); benzyl alcohol is used as the core, with a boiling point T2 of 200°C.

[0217] Examples 7-8

[0218] The difference between Examples 7-8 and Example 1 is that the volumetric particle size distribution Dv50 of the thermally expanded microspheres is different.

[0219] Example 9

[0220] The difference between Example 9 and Example 7 is that the thickness d1 of the first insulating layer 121 is different, and the material of the core of the thermally expanding microspheres is different.

[0221] Examples 10-11

[0222] The difference between Examples 10-11 and Example 1 is that the thickness d1 of the first insulating layer 121 is different.

[0223] Comparative Example 1

[0224] The difference between Comparative Example 1 and Example 1 is that the insulating slurry does not contain thermally expandable microspheres, and the thermally expandable microspheres in the insulating slurry are replaced with boehmite.

[0225] Comparative Example 2

[0226] The difference between Comparative Example 2 and Example 1 is that, based on the total mass of the insulating slurry, the mass ratio A:B:C of the thermally expanded microspheres 2, binder and solvent satisfies: 2wt%: 5wt%: 93wt%.

[0227] Comparative Example 3

[0228] The difference between Comparative Example 3 and Example 1 is that, based on the total mass of the insulating slurry, the mass ratio A:B:C of the thermally expanded microspheres 2, binder and solvent satisfies: 10wt%: 2wt%: 88wt%.

[0229] Comparative Example 4

[0230] The difference between Comparative Example 4 and Example 1 is that the outer shell of the thermally expandable microspheres is polystyrene, and the glass transition temperature T1 of polystyrene is 90°C; the core of the thermally expandable microspheres is n-hexane, and the boiling point T2 of n-hexane is 70°C.

[0231] Comparative Example 5

[0232] The difference between Comparative Example 5 and Example 1 is that the thickness d1 of the first insulating layer 121 is 10 μm.

[0233] In the above comparative examples and embodiments, changes in the material and volumetric particle size distribution Dv50 of the thermally expandable microspheres 2, changes in the thickness d1 of the first insulating layer 121, and changes in the mass ratio A:B:C of the thermally expandable microspheres 2, binder, and solvent can all lead to changes in the distance L.

[0234] In Table 1, d1 represents the thickness of the first insulating layer 121, k1 represents the coating width of the first insulating layer 121, A:B:C represents the mass ratio of thermally expanded microspheres 2, binder, and solvent, PS represents polystyrene, PMMA represents polymethyl methacrylate, and L represents the minimum distance by which the second portion 1212 of the first insulating layer 121 extends beyond the main body 1011. Here, d1 is the thickness of the first insulating layer coated on one side of the current collector, and the total thickness of the first insulating layer in the electrode can be 2d1.

[0235] Table 1. Parameters of the Examples and Comparative Examples

[0236]

[0237] Table 2. Experimental results for comparative and example cases.

[0238] Does the first insulating layer extend beyond the current collector? Did the joint catch fire? Example 1 yes No smoke, no fire Example 2 yes No smoke, no fire Example 3 yes No smoke, no fire Example 4 yes No smoke, no fire Example 5 yes No smoke, no fire Example 6 yes No smoke, no fire Example 7 yes No smoke, no fire Example 8 yes No smoke, no fire Example 9 yes No smoke, no fire Example 10 yes No smoke, no fire Example 11 yes No smoke, no fire Comparative Example 1 no fire Comparative Example 2 no fire Comparative Example 3 no fire Comparative Example 4 no fire Comparative Example 5 yes fire

[0239] [Preparation of battery cells]

[0240] (1) Prepare the paste for the first insulating layer

[0241] The thermally expandable microspheres, binder, and solvent were mixed in a certain proportion, and the solvent was added and stirred until homogeneous. The viscosity of the slurry was approximately 3000 mPa·s. The binder was polyvinylidene fluoride (PVDF), and the solvent was N-methylpyrrolidone.

[0242] (2) Coating and drying

[0243] The positive electrode active slurry is coated onto aluminum foil to prepare the active material layer; simultaneously, a first insulating layer of corresponding width and thickness is coated onto the aluminum foil. The mixture is then dried in an oven at 100°C.

[0244] (3) Laser cutting

[0245] The above product is cut using a laser to obtain the positive electrode sheet.

[0246] (4) Manufacturing battery cells

[0247] The above-mentioned positive electrode sheet is assembled together with other battery components: negative electrode sheet, separator, and electrolyte to form a lithium-ion battery cell.

[0248] [Confirmation of the first insulating layer]

[0249] Using a scanning electron microscope, the cross-section of the electrode was observed (e.g., along...). Figure 2 (The electrode is cut open along the AA direction shown). Observe whether the first insulating layer has a portion that extends beyond the main body of the current collector, and observe the distance by which the first insulating layer extends beyond the main body.

[0250] [Test of connecting the negative terminal to the fully charged terminal]

[0251] Connect the positive electrode to the fully charged negative electrode and observe whether there is smoke or fire. If there is no smoke or fire, it proves that the first insulating layer has a protruding part, which prevents the exposed end face (aluminum foil) of the current collector from contacting the fully charged negative electrode.

[0252] As shown in Examples 1-11 and Comparative Examples 1-4, the first insulating layer has a portion that extends beyond the current collector. This portion can prevent the exposed end face of the current collector from contacting the negative electrode plate. When the positive electrode plate overlaps with the fully charged negative electrode plate, no smoke or fire will occur.

[0253] As shown in Examples 1-11 and Comparative Example 5, when the minimum distance L of the portion of the first insulating layer extending beyond the current collector is 10μm to 80μm, it can effectively prevent the exposed end face of the current collector from contacting the negative electrode plate, so that no smoke or fire will occur when the positive electrode plate overlaps with the fully charged negative electrode plate.

[0254] As shown in Examples 1-11 and Comparative Example 1, compared to boehmite, the use of thermally expandable microspheres allows the first insulating layer to expand during the cutting process, preventing the exposed end face of the current collector from contacting the negative electrode sheet.

[0255] As shown in Examples 1-11 and Comparative Example 2, when the content of thermally expandable microspheres in the insulating slurry is too low, the expansion effect of the first insulating layer during the cutting process is limited, and the first insulating layer is difficult to extend beyond the current collector. By reasonably setting the content of thermally expandable microspheres in the insulating slurry, it is beneficial to the expansion of the first insulating layer.

[0256] As shown in Examples 1-11 and Comparative Example 3, when the binder content in the insulating slurry is too low, the first insulating layer detaches from the current collector, making it difficult for the first insulating layer to expand beyond the current collector.

[0257] As shown in Examples 1-9 and Comparative Example 4, when the glass transition temperature of the outer shell and the boiling point of the core in the thermally expandable microspheres are relatively low, the microspheres expand during the drying process in the oven after being coated with the insulating slurry. During the cutting process along the cutting line, the portion of the first insulating layer that extends beyond the current collector is cut off. By reasonably setting the material of the thermally expandable microspheres, it is beneficial to obtain a first insulating layer that extends a certain distance beyond the current collector.

[0258] As shown in Comparative Example 5, the coating thickness of the first insulating layer is relatively small, the content of thermally expanding microspheres in the first insulating layer is relatively small, and the distance of the first insulating layer beyond the current collector is relatively small during the cutting process.

[0259] As shown in Examples 1-2, increasing the mass ratio of thermally expandable microspheres in the insulating slurry of the first insulating layer is beneficial to improving the expansion effect of the first insulating layer, resulting in a larger distance between the first insulating layer and the current collector. In addition, setting a reasonable mass ratio of thermally expandable microspheres, binder, and solvent in the insulating slurry of the first insulating layer facilitates the coating of the insulating slurry and is beneficial to obtaining a first insulating layer with better adhesion and expansion properties.

[0260] In conjunction with Examples 1 and 3, and as shown in 5-6, the embodiments of this application can be applied to a variety of different thermally expandable microspheres, which can cause the first insulating layer to have different expansion effects. The lower the glass transition temperature of the outer shell of the thermally expandable microsphere, the larger the volume that the thermally expandable microsphere can expand to, and the larger L is; the lower the boiling point of the core, the easier it is to vaporize, and the larger the expansion volume of the thermally expandable microsphere, and the larger L is.

[0261] As shown in Examples 1 and 4, the coating width k1 of the first insulating layer has little effect on L. The coating width k1 of the first insulating layer is mainly related to the size of the exposed aluminum foil on the tab. Generally speaking, the larger k1 is, the smaller the size of the exposed aluminum foil on the tab.

[0262] As shown in Examples 1, 5, 10, and 11, different thicknesses L can be obtained by setting the thickness d1 of the first insulating layer. The larger d1 is, the more advantageous it is to obtain a larger L. By setting d1 to 20μm to 40μm, and further, to 20μm to 30μm, it is beneficial to obtain a more suitable L, which is convenient for balancing the volumetric energy density and reliability of the battery cell.

[0263] Referring to Examples 1 and 7-8, the embodiments of this application are applicable to thermally expandable microspheres with a volumetric particle size distribution Dv50 of 1 μm to 3 μm. The smaller the particle size of the thermally expandable microspheres, the easier they expand under the heat generated by cutting, and the larger L is. By setting the volumetric particle size distribution Dv50 of the thermally expandable microspheres to 1 μm to 3 μm, it is easier to obtain a suitable L.

[0264] As shown in Example 9, by increasing the thickness d1 of the first insulating layer and selecting thermally expanding microspheres with lower expansion temperature and smaller particle size, it is beneficial to obtain a larger L.

[0265] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrode sheet, characterized in that, include: Current collector, active material layer and first insulating layer, The current collector includes a main body and an electrode tab. The electrode tab extends from a first end of the main body, which is one end of the main body along a first direction. The main body includes a coating area and a transition area, and the transition area is disposed between the coating area and the electrode tab. The active material layer is disposed on the surface of the coating area; The first insulating layer includes a first part and a second part. The first part is disposed on the surface of the transition region, and the second part extends from the first part along the first direction and is disposed in the region outside the tab. Along the first direction, the minimum distance L of the second part extending beyond the main body is 10μm to 80μm.

2. The electrode sheet according to claim 1, characterized in that, Along the first direction, the minimum distance L that the second part extends beyond the main body is 50 μm to 60 μm.

3. The electrode sheet according to claim 1 or 2, characterized in that, The first insulating layer comprises a thermally expanding material.

4. The electrode sheet according to claim 3, characterized in that, The thermally expandable material includes thermally expandable microspheres having a core-shell structure. The outer shell of the core-shell structure is made of a thermoplastic polymer, and the inner core of the core-shell structure is made of a foaming agent.

5. The electrode sheet according to claim 4, characterized in that, The glass transition temperature T1 of the thermoplastic polymer is 100℃~200℃.

6. The electrode sheet according to claim 5, characterized in that, The glass transition temperature T1 of the thermoplastic polymer is 100℃~120℃.

7. The electrode sheet according to any one of claims 4-6, characterized in that, The thermoplastic polymer includes at least one of the following: polystyrene, polycarbonate, polyvinyl acetate, polymethyl methacrylate, and copolymers of two or more of polystyrene, polycarbonate, polyvinyl acetate, and polymethyl methacrylate.

8. The electrode sheet according to any one of claims 4-6, characterized in that, The foaming agent includes an organic solvent, and the boiling point T2 of the organic solvent is 100℃~200℃.

9. The electrode sheet according to claim 8, characterized in that, The boiling point T2 of the organic solvent is 100℃~120℃.

10. The electrode according to claim 8, characterized in that, The organic solvent includes at least one of the following: n-butanol, ethylenediamine, nitromethane, nitromethane, cycloheptane, and benzyl alcohol.

11. The electrode sheet according to any one of claims 4-6, characterized in that, The volumetric particle size distribution Dv50 of the thermally expanded microspheres in the portion of the first insulating layer near the coating area is 1 μm to 3 μm.

12. The electrode sheet according to claim 1 or 2, characterized in that, The first insulating layer also includes an adhesive.

13. The electrode sheet according to claim 12, characterized in that, The adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyimide.

14. The electrode sheet according to claim 1 or 2, characterized in that, The thickness d1 of the first insulating layer is 15μm~45μm.

15. The electrode sheet according to claim 14, characterized in that, The thickness d1 of the first insulating layer is 20μm~30μm.

16. The electrode sheet according to claim 1 or 2, characterized in that, The first insulating layer further includes a third portion, which is disposed on a portion of the surface of the tab and extends from the first portion along the first direction.

17. The electrode sheet according to claim 1 or 2, characterized in that, The current collector includes a metal foil or a composite current collector.

18. The electrode sheet according to claim 17, characterized in that, The metal foil includes aluminum foil or copper foil.

19. The electrode sheet according to claim 17, characterized in that, 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.

20. The electrode sheet according to claim 17, characterized in that, The current collector includes aluminum foil.

21. A method for preparing an electrode sheet according to any one of claims 1-20, characterized in that, include: Provide current collectors; An active material is coated onto the first region of the current collector to form an active material layer; An insulating slurry is coated on the second region of the current collector to form a first insulating layer. The insulating slurry includes thermally expandable microspheres, a binder, and a solvent. Based on the total mass of the insulating slurry, the mass percentage A of the thermally expandable microspheres is ≥15wt%, the mass percentage B of the binder is ≥15wt%, the expansion temperature of the thermally expandable microspheres is ≥100℃, and the thickness d1 of the first insulating layer is ≥10μm. A current collector having the first insulating layer cut along a cutting line, at least a portion of which is located in the second region.

22. The method according to claim 21, characterized in that, The thermally expandable microspheres have a core-shell structure, wherein the outer shell of the core-shell structure is made of a thermoplastic polymer, and the inner core of the core-shell structure is made of a foaming agent.

23. The method according to claim 22, characterized in that, The glass transition temperature T1 of the thermoplastic polymer is 100℃~200℃.

24. The method according to claim 23, characterized in that, The glass transition temperature T1 of the thermoplastic polymer is 100℃~120℃.

25. The method according to any one of claims 21-24, characterized in that, The volumetric particle size distribution Dv50 of the thermally expandable microspheres is 1μm~3μm.

26. The method according to any one of claims 22-24, characterized in that, The thermoplastic polymer includes at least one of the following: polystyrene, polycarbonate, polyvinyl acetate, polymethyl methacrylate, and copolymers of two or more of polystyrene, polycarbonate, polyvinyl acetate, and polymethyl methacrylate.

27. The method according to any one of claims 22-24, characterized in that, The foaming agent includes an organic solvent, and the boiling point T2 of the organic solvent is 100℃~200℃.

28. The method according to claim 27, characterized in that, The boiling point T2 of the organic solvent is 100℃~120℃.

29. The method according to claim 27, characterized in that, The organic solvent includes at least one of the following: n-butanol, ethylenediamine, nitromethane, nitromethane, cycloheptane, and benzyl alcohol.

30. The method according to any one of claims 21-24, characterized in that, The adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyimide.

31. The method according to any one of claims 21-24, characterized in that, Based on the total mass of the insulating slurry, the mass ratio A:B:C of the thermally expanding microspheres, the binder, and the solvent satisfies: 5wt%~10wt%: 5wt%~10wt%: 80wt%~90wt%.

32. The method according to any one of claims 21-24, characterized in that, Along the first direction, the coating width k1 of the first insulating layer is 3mm to 6mm, and the first direction is the arrangement direction of the first region and the second region.

33. The method according to any one of claims 21-24, characterized in that, Along the first direction, the thickness d1 of the first insulating layer is 15μm~45μm.

34. The method according to claim 33, characterized in that, The thickness d1 of the first insulating layer is 20μm~30μm.

35. A single battery cell, characterized in that, The electrode includes the electrode as described in any one of claims 1-20, and / or the electrode prepared by the method described in any one of claims 21-34.

36. A battery, characterized in that, Includes the battery cell as described in claim 35.

37. An electrical device, characterized in that, Includes the battery as described in claim 36.

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