Electrode plate and battery

Abstract

The utility model discloses an electrode plate and a battery, and belongs to the technical field of batteries. The electrode sheet comprises a current collector; the carbon layer is positioned on at least one side of two opposite sides of the current collector; the active material layer is positioned on one side, deviating from the current collector, of the carbon layer; and the functional layer is positioned on one side, deviating from the current collector, of the active material layer. The liquid immersion speed and the liquid retention capacity of the electrode plate can be improved, the cycle performance of the battery is improved, and the rate capability of the battery is improved.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to an electrode sheet and a battery. Background Technology

[0002] In recent years, with the global energy transition and the rapid development of the electric vehicle industry, lithium-ion batteries have experienced rapid growth in the market due to their technological advantages such as high energy density, long cycle life and low self-discharge rate.

[0003] In lithium-ion batteries, increasing the compaction density of the electrode sheets can improve the battery's energy density. However, increasing the compaction density weakens the wettability and liquid retention of the electrolyte, thus affecting the battery's cycle performance. Moreover, increasing the compaction density also exacerbates the mirror-like surface finish of the electrode sheets, increasing interfacial resistance and consequently affecting the battery's rate performance. Utility Model Content

[0004] This application aims to address at least one of the technical problems existing in the related art. To this end, this application proposes an electrode sheet and a battery that can improve the immersion rate and liquid retention of the electrode sheet, improve the cycle performance of the battery, and improve the rate performance of the battery.

[0005] This application provides an electrode sheet, comprising:

[0006] current collector;

[0007] A carbon layer is located on at least one of the opposite sides of the current collector;

[0008] An active material layer is located on the side of the carbon layer opposite to the current collector;

[0009] The functional layer is located on the side of the active material layer opposite to the current collector.

[0010] According to one embodiment of this application, the carbon layer includes a first sub-carbon layer, which is located on one side of the current collector;

[0011] The active material layer includes a first active material sublayer, which is located on the side of the first sub-carbon layer away from the current collector.

[0012] The functional layer includes a first functional sublayer, which is located on the side of the first active substance sublayer opposite to the current collector.

[0013] According to one embodiment of this application, the carbon layer further includes a second sub-carbon layer, wherein the first sub-carbon layer and the second sub-carbon layer are respectively located on opposite sides of the current collector;

[0014] The active material layer further includes a second active material sublayer, which is located on the side of the second sub-carbon layer away from the current collector.

[0015] According to one embodiment of this application, the functional layer further includes a second functional sublayer located on the side of the second active material sublayer opposite to the current collector.

[0016] According to one embodiment of this application, the functional layer includes a binder, a functional material, and a dispersant, wherein the functional material includes one or more combinations of a conductive agent and a solid electrolyte.

[0017] According to one embodiment of this application, in the functional layer, the conductive agent includes one or more combinations of conductive carbon black, conductive graphite, conductive carbon nanotubes, and graphene, and the solid electrolyte includes one or more combinations of lithium titanium aluminum phosphate and lithium zirconium oxide.

[0018] According to one embodiment of this application, in the functional layer, the binder accounts for 0.5%-5%, the functional material accounts for 90%-99%, the dispersant accounts for 0.5%-5%, and the slurry solid content of the functional layer is 5%-30%.

[0019] According to one embodiment of this application, the thickness of the functional layer is 0.5-2 μm.

[0020] According to one embodiment of this application, the electrode sheet includes a positive electrode sheet.

[0021] This application provides a battery including the electrode sheet described in any of the above embodiments.

[0022] The above-described one or more technical solutions in the embodiments of this application have at least one of the following technical effects:

[0023] By setting a functional layer on the surface of the electrode sheet (i.e. the side of the active material layer facing away from the current collector), the surface of the electrode sheet can be wetted, the mirror-like state of the electrode sheet surface can be alleviated, the immersion speed and liquid retention of the electrode sheet can be improved, thereby improving the cycle performance of the battery. Moreover, the setting of the functional layer can improve conductivity and / or ion conduction, reduce the interfacial resistance of the electrode sheet, and thus improve the rate performance of the battery.

[0024] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0025] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0026] Figure 1 This is one of the structural schematic diagrams of the electrode sheet provided in the embodiments of this application;

[0027] Figure 2 This is a second schematic diagram of the structure of the electrode sheet provided in the embodiments of this application;

[0028] Figure 3 This is the third schematic diagram of the structure of the electrode sheet provided in the embodiments of this application. Detailed Implementation

[0029] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0030] The electrode sheet and battery provided in the embodiments of this application are described below with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the structure of an electrode sheet provided in an embodiment of this application. The electrode sheet can be used in a battery, which may include a lithium-ion battery.

[0032] like Figure 1 As shown in the embodiments of this application, the electrode sheet includes a current collector 1, a carbon layer 2, an active material layer 3, and a functional layer 4. The electrode sheet may include a positive electrode. As a key component of the battery, the positive electrode provides electrons to participate in chemical reactions to generate current. Furthermore, the positive electrode directly affects the battery's energy density, charge / discharge efficiency, and cycle life.

[0033] The current collector 1 serves as a supporting structure within the electrode sheet, simultaneously collecting and conducting current to ensure the stability and efficiency of battery charging and discharging. The current collector 1 can have various structures. For example, it can include a metal foil structure, a composite structure, a porous structure, or a three-dimensional structure. The structure of the current collector 1 can vary depending on the type of battery and its performance requirements. The material of the current collector 1 can include metals (such as aluminum, copper, nickel, or stainless steel), non-metals (such as carbon fiber cloth or carbon nanotubes), or composite materials (such as conductive resin, carbon-coated aluminum foil, or titanium-nickel shape memory alloy). The material of the current collector 1 can be selected based on the type of electrode sheet it is located on (such as the positive electrode sheet) and the required electrochemical performance. In some embodiments, the current collector 1 can be a foil.

[0034] The carbon layer 2 is located on at least one of the opposite sides of the current collector 1. The opposite sides are opposite sides in the thickness direction of the current collector 1. In other words, the carbon layer 2 can be located on either side of the thickness direction of the current collector 1, or it can be located on opposite sides in the thickness direction of the current collector 1.

[0035] The carbon layer 2 serves to prevent corrosion of the electrode material, acting as a buffer and protector. It also improves the stability of the electrode sheet while promoting electron and ion transport to enhance conductivity and optimize battery performance. The carbon layer 2 can have various structures, including single-layer, multi-layer, or gradient structures. The structure of the carbon layer 2 can differ depending on the specific application requirements and battery performance specifications. The thickness of the carbon layer 2 can range from 0.5 to 5 μm.

[0036] During the fabrication of the electrode sheet, the carbon layer 2 can be formed on at least one of the opposite sides of the current collector 1 through a thin film deposition process. The thin film deposition process can include coating processes, such as roll coating, spray coating, gravure coating, or dip coating.

[0037] In some embodiments, carbon layer 2 may include a binder, a conductive agent, and a dispersant. The conductive agent in carbon layer 2 may include one or more combinations of conductive graphite, conductive carbon black, Ketjen black, acetylene black, carbon fiber, carbon nanotubes, and graphene. The binder in carbon layer 2 may include one or more combinations of polymers such as polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyvinyl alcohol (PVA), sodium alginate (Alg), β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), and polytetrafluoroethylene (PTFE), as well as functionalized derivatives of the above polymers, and / or copolymers between monomers. The dispersant in carbon layer 2 may include one or more combinations of compounds such as quaternary ammonium salts, carboxylic acids, polyols, epoxy compounds, phosphate esters, and polymers.

[0038] In some embodiments, the proportion of the conductive agent in the carbon layer 2 can be set to 90%-99%. The proportion of the binder can be set to 0.5%-5%. The proportion of the dispersant can be 0.5%-5%.

[0039] The active material layer 3 is located on the side of the carbon layer 2 away from the current collector 1. The active material layer 3 can be located on one or both sides of the current collector 1 in the thickness direction. When the carbon layer 2 is located on either side of the current collector 1 in the thickness direction, the active material layer 3 and the carbon layer 2 are located on the same side of the current collector 1, that is, the carbon layer 2 and the active material layer 3 are stacked sequentially on either side of the current collector 1 in the thickness direction; when the carbon layer 2 is located on opposite sides of the current collector 1 in the thickness direction, the active material layer 3 is located on opposite sides of the current collector 1 in the thickness direction, that is, the carbon layer 2 and the active material layer 3 are stacked sequentially on opposite sides of the current collector 1 in the thickness direction.

[0040] The active material layer 3 can serve as the region for battery chemical reactions. A carbon layer 2 acts as a transition layer between the active material layer 3 and the current collector 1, increasing the conductivity between them. The thickness of the active material layer 3 can be 50-200 μm.

[0041] During the preparation of the electrode sheet, the active material layer 3 can be formed on the side of the carbon layer 2 away from the current collector 1 through a thin film deposition process. The thin film deposition process can include coating processes, such as blade coating, transfer coating, or extrusion coating. After the active material layer 3 is formed, the electrode sheet structure composed of the current collector 1, carbon layer 2, and active material layer 3 is rolled to increase the compaction density of the electrode sheet structure, thereby increasing the energy density of the battery.

[0042] In some embodiments, the active material layer 3 may include an active material, a conductive agent, a binder, and additives. When the electrode sheet is a positive electrode sheet, the active material in the active material layer 3 may include a positive electrode active material. The positive electrode active material may include one or a combination of several of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, and lithium manganese iron phosphate. The conductive agent in the active material layer 3 may include one or a combination of several of conductive graphite, conductive carbon black, Ketjen black, acetylene black, carbon fiber, carbon nanotubes, and graphene. The binder in the active material layer 3 may include one or a combination of polymers such as polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyvinyl alcohol (PVA), sodium alginate (Alg), β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), and polytetrafluoroethylene (PTFE), as well as functionalized derivatives of the above polymers, and / or copolymers between monomers. The additives in the active material layer 3 may include dispersants (such as one or more of the following compounds: quaternary ammonium salts, carboxylic acids, polyols, epoxides, phosphate salts, polymers, etc.), toughening agents, or lithium supplements.

[0043] In some embodiments, the proportion of active material in the active material layer 3 can be 80%-99%. The proportion of conductive agent can be 0.5%-10%. The proportion of binder can be 0.5%-5%. The proportion of additives can be 0%-5%.

[0044] The functional layer 4 is located on the side of the active material layer 3 away from the current collector 1. The functional layer 4 can be located on one or both sides of the current collector 1 in the thickness direction. When carbon layer 2 and active material layer 3 are located on one side of the thickness direction of current collector 1, functional layer 4 is located on the same side of current collector 1 as carbon layer 2 and active material layer 3, that is, carbon layer 2, active material layer 3 and functional layer 4 are sequentially stacked on either side of the thickness direction of current collector 1; when carbon layer 2 and active material layer 3 are both located on opposite sides of the thickness direction of current collector 1, active material layer 3 can be located on one side of the thickness direction of current collector 1, that is, carbon layer 2, active material layer 3 and functional layer 4 are sequentially stacked on one side of the thickness direction of current collector 1, and carbon layer 2 and active material layer 3 are sequentially stacked on the other side of the thickness direction of current collector 1; when carbon layer 2 and active material layer 3 are both located on opposite sides of the thickness direction of current collector 1, active material layer 3 can be located on opposite sides of the thickness direction of current collector 1, that is, carbon layer 2, active material layer 3 and functional layer 4 are sequentially stacked on opposite sides of the thickness direction of current collector 1 respectively. To increase the compaction density of the electrode sheet and store more energy within a limited volume, after forming a carbon layer 2 and an active material layer 3 on the current collector 1, the electrode sheet structure consisting of the current collector 1, carbon layer 2, and active material layer 3 is rolled. However, if the compaction density of the electrode sheet structure is too high, a mirror-like phenomenon occurs on the surface of the electrode sheet structure, which severely hinders the electrolyte wetting rate, affects the cycle performance of the battery, and increases the interfacial resistance, thus affecting the rate performance of the battery.

[0045] Based on this, in this embodiment, after rolling the electrode sheet structure composed of current collector 1, carbon layer 2, and active material layer 3, a functional layer 4 is formed on the side of the active material layer 3 facing away from the current collector 1 (i.e., the surface of the electrode sheet structure) through a thin film deposition process (including coating processes, such as roll coating, spray coating, or gravure coating). The slurry of the functional layer 4 can soften the mirror-like state of the electrode sheet structure surface after the rolling process, forming a transition layer (the thickness of the transition layer is less than or equal to 100 nm) to optimize the bonding effect between the functional layer 4 and the active material layer 3, thereby improving the electrolyte wetting speed. The functional layer 4 can also serve as an electrolyte storage space, which can increase the overall electrolyte retention of the battery, thereby improving the battery's cycle performance.

[0046] In some embodiments, the thickness of the functional layer 4 is 0.5-2 μm.

[0047] In the embodiments of this application, the functional layer 4 is relatively thin, which facilitates sufficient contact between the electrolyte and the electrode sheet, and can further improve the wetting speed of the electrolyte. At the same time, the thinness of the functional layer 4 can improve the electron and ion transport efficiency, further reduce the interface resistance, and improve the rate performance of the battery.

[0048] In some embodiments, the functional layer 4 includes a binder, a functional material, and a dispersant, wherein the functional material includes one or more combinations of a conductive agent and a solid electrolyte.

[0049] The binder in functional layer 4 adheres the functional materials in functional layer 4 to the electrode sheet structure, maintaining the stability of the electrode sheet structure and improving the wettability of the electrolyte, thereby improving the efficiency of battery fabrication. The dispersant is used for chemical dispersion in the electrode sheet, improving the dispersion performance of materials in the functional layer 4 slurry and protecting the structural stability of functional layer 4 during the coating process. The binder materials may include one or more combinations of polymers such as polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyvinyl alcohol (PVA), sodium alginate (Alg), β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), and polytetrafluoroethylene (PTFE), as well as functionalized derivatives of the above polymers and / or copolymers between monomers. The dispersant materials may include one or more combinations of compounds such as quaternary ammonium salts, carboxylic acids, polyols, epoxy compounds, phosphate salts, and polymers.

[0050] The functional layer 4 contains functional materials, which enable the functional layer 4 to have good conductivity and / or ion conduction effects, which can promote the transport of electrons and / or ions within the electrode sheet, improve the efficiency of electron and / or ion transport within and between the active material layer 3, carbon layer 2 and current collector 1, thereby reducing interface resistance and improving the rate performance of the battery.

[0051] In some embodiments, in functional layer 4, the conductive agent includes one or more combinations of conductive carbon black, conductive graphite, conductive carbon nanotubes and graphene, and the solid electrolyte includes one or more combinations of lithium titanium aluminum phosphate and lithium zirconium oxide.

[0052] In some embodiments, in functional layer 4, the proportion of binder is 0.5%-5%, the proportion of functional material is 90%-99%, the proportion of dispersant is 0.5%-5%, and the solid content of slurry in functional layer 4 is 5%-30%.

[0053] In functional layer 4, the proportion of functional materials is relatively large, forming a functional material coating with excellent conductivity and / or ion conduction effects on the surface of the active material layer 3 in contact with functional layer 4. This improves the efficiency of electron and / or ion transport within the electrode sheet, thereby reducing the interfacial resistance of the electrode sheet and enhancing the rate performance of the battery. The proportion of binder in functional layer 4 is relatively small, sufficient to ensure the functional materials in functional layer 4 adhere to the electrode sheet structure and maintain its stability. The proportion of dispersant in functional layer 4 is also relatively small, sufficient to improve the material dispersion performance of the electrode sheet slurry and maintain the stability of the electrode sheet structure during the coating process.

[0054] It should be noted that the different types of materials and / or the different proportions of materials in the carbon layer 2, active material layer 3 and functional layer 4 in the electrode sheet will have different effects on the battery performance (including cycle performance and rate performance, etc.), but compared with related technologies (where no functional layer is set in the electrode sheet), the battery performance is improved.

[0055] In some embodiments, such as Figure 2 As shown, carbon layer 2 includes a first sub-carbon layer 21, which is located on one side of current collector 1. The first sub-carbon layer 21 can be located on either side of the thickness direction of current collector 1, for example... Figure 2 As shown, the first sub-carbon layer 21 is located above the current collector 1.

[0056] The active material layer 3 includes a first active material sublayer 31, which is located on the side of the first sub-carbon layer 21 facing away from the current collector 1. The first active material sublayer 31 is disposed correspondingly to the first sub-carbon layer 21, for example... Figure 2 As shown, the first active material sublayer 31 is located above the first carbon sublayer 21.

[0057] Functional layer 4 includes a first functional sublayer 41, which is located on the side of the first active material sublayer 31 facing away from the current collector 1. The first functional sublayer 41 and the first active material sublayer 31 are correspondingly arranged, for example... Figure 2 As shown, the first functional sublayer 41 is located above the first active substance sublayer 31.

[0058] In this embodiment, the carbon layer 2, the active material layer 3, and the functional layer 4 are all located on one side of the current collector 1. During the preparation of the electrode sheet, after the first sub-carbon layer 21 and the first active material sub-layer 31 are sequentially formed on one side of the current collector 1, the electrode sheet structure (including the current collector 1, the first sub-carbon layer 21, and the first active material sub-layer 31) is rolled to increase the compaction density of the electrode sheet structure. A first functional sub-layer 41 is provided on the surface of the compacted electrode sheet structure (i.e., the side of the first active material sub-layer 31 facing away from the current collector 1), which can alleviate the mirror-like state of the surface of the first active material sub-layer 31 (i.e., the surface where the first active material sub-layer 31 contacts the first functional sub-layer 41), thereby improving the electrolyte wetting speed and the electrolyte retention capacity of the electrode sheet, and thus improving the cycle performance of the battery. Moreover, the provision of the first functional sub-layer 41 can improve conductivity and / or ion conduction, reduce the interfacial resistance of the electrode sheet, and thus improve the rate performance of the battery.

[0059] In some embodiments, such as Figure 3 As shown, carbon layer 2 also includes a second sub-carbon layer 22, meaning carbon layer 2 comprises a first sub-carbon layer 21 and a second sub-carbon layer 22. The first sub-carbon layer 21 and the second sub-carbon layer 22 are located on opposite sides of the current collector 1. For example... Figure 3 As shown, the first sub-carbon layer 21 is located above the current collector 1, and the second sub-carbon layer 22 is located below the current collector 1.

[0060] The active material layer 3 also includes a second active material sublayer 32, meaning the active material layer 3 includes a first active material sublayer 31 and a second active material sublayer 32. The first active material sublayer 31 is located on the side of the first sub-carbon layer 21 facing away from the current collector 1, and the second active material sublayer 32 is located on the side of the second sub-carbon layer 22 facing away from the current collector 1. For example... Figure 3 As shown, the first active material sublayer 31 is located above the first sub-carbon layer 21, and the second active material sublayer 32 is located below the second sub-carbon layer 22. The first functional sublayer 41 is located above the first active material sublayer 31, and no functional layer 4 is provided below the second active material sublayer 32.

[0061] In this embodiment, carbon layer 2 and active material layer 3 are located on opposite sides of current collector 1, and functional layer 4 is located on one side of current collector 1. During the preparation of the electrode sheet, a first sub-carbon layer 21 and a second sub-carbon layer 22 are disposed on opposite sides of current collector 1. A first active material sub-layer 31 is disposed on the side of the first sub-carbon layer 21 facing away from current collector 1, and a second active material sub-layer 32 is disposed on the side of the second sub-carbon layer 22 facing away from current collector 1, thus obtaining the electrode sheet structure. The electrode sheet structure is then rolled to increase its compaction density. For example, when the active material in active material layer 3 is lithium iron phosphate, the compaction density of both the first active material sub-layer 31 and the second active material sub-layer 32 after rolling is 2.5-2.7 g / cm³.3 A first functional sublayer 41 is provided on the surface of the compacted electrode structure (i.e., the side of the first active material sublayer 31 facing away from the current collector 1). This can alleviate the mirror-like state of the surface of the first active material sublayer 31 (i.e., the surface where the first active material sublayer 31 and the first functional sublayer 41 contact) thereby improving the electrolyte wetting speed and the electrolyte retention capacity of the electrode, thus improving the cycle performance of the battery. Moreover, the provision of the first functional sublayer 41 can improve conductivity and / or ion conduction, reduce the interfacial resistance of the electrode, thereby improving the rate performance of the battery. In addition, in this embodiment, carbon layer 2 and active material layer 3 are provided on opposite sides of the current collector 1 in the thickness direction. Compared with providing carbon layer 2 and active material layer 3 on one side of the current collector 1, this can increase the battery capacity and energy density.

[0062] For example, using a gravure coating process, a first sub-carbon layer 21 and a second sub-carbon layer 22 are coated on opposite sides of the current collector 1 in the thickness direction. The coating thickness of both the first sub-carbon layer 21 and the second sub-carbon layer 22 is 1 μm. The material ratio of binder, conductive agent, and dispersant in both the first sub-carbon layer 21 and the second sub-carbon layer 22 is 5:94.5:0.5. The conductive agent in both the first sub-carbon layer 21 and the second sub-carbon layer 22 is conductive carbon black. Using a transfer coating process, a first active material sub-layer 31 is coated on the side of the first sub-carbon layer 21 facing away from the current collector 1, and a second active material sub-layer 32 is coated on the side of the second sub-carbon layer 22 facing away from the current collector 1, resulting in an electrode sheet structure. The material ratio of active material, conductive agent, binder, and additive in the first active material sub-layer 31 and the second active material sub-layer 32 is 96:2:2:0. The active material in the first active material sub-layer 31 and the second active material sub-layer 32 is lithium iron phosphate, the conductive agent is conductive carbon black, and the binder is polyvinylidene fluoride. The above electrode sheet structure was rolled, and the compacted density of the rolled electrode sheet structure was 2.6 g / cm³. 3 The immersion rate was 209 g / s. Then, using a gravure coating process, a first functional sublayer 41 was coated on the side of the first active material sublayer 31 facing away from the current collector 1. The coating thickness of the first functional sublayer 41 was 1 μm. The material ratio of binder, functional material, and dispersant in the first functional sublayer 41 was 5:94.5:0.5. The functional material in the first functional sublayer 41 was conductive carbon black. After setting the first functional sublayer 41, the immersion rate of the electrode sheet was 106 g / s, which increased the immersion rate of the electrode sheet by 49.28% compared to the previous electrode sheet structure.

[0063] For example, all conductive agents (including the conductive agents in the first sub-carbon layer 21, the second sub-carbon layer 22, the first active material sub-layer 31, and the second active material sub-layer 32) and functional materials (i.e., the functional material in the first functional sub-layer 41) in the above electrode sheet structure are replaced with conductive carbon black and conductive graphite (material ratio of 1:1). The material ratio of active material, conductive agent, binder, and additive in the first active material sub-layer 31 and the second active material sub-layer 32 is replaced with 95.7:2:2:0.3 (additive is polyvinylpyrrolidone), and the rest remain unchanged. The compaction density of the rolled electrode sheet structure is 2.65 g / cm³. 3 The immersion rate was 183 / s. After coating the first functional sublayer 41 onto the rolled electrode structure, the immersion rate was 80 / s, an increase of 56.50%.

[0064] In some embodiments, such as Figure 1 As shown, functional layer 4 also includes a second functional sublayer 42, meaning functional layer 4 includes a first functional sublayer 41 and a second functional sublayer 42. The first functional sublayer 41 is located on the side of the first active material sublayer 31 facing away from the current collector 1, and the second functional sublayer 42 is located on the side of the second active material sublayer 32 facing away from the current collector 1. For example... Figure 1 As shown, the first functional sublayer 41 is located above the first active substance sublayer 31, and the second functional sublayer 42 is located below the second active substance sublayer 32.

[0065] In this embodiment, carbon layer 2, active material layer 3, and functional layer 4 are all located on opposite sides of current collector 1. During the preparation of the electrode sheet, a first sub-carbon layer 21 and a second sub-carbon layer 22 are disposed on opposite sides of current collector 1. A first active material sub-layer 31 is disposed on the side of the first sub-carbon layer 21 facing away from current collector 1, and a second active material sub-layer 32 is disposed on the side of the second sub-carbon layer 22 facing away from current collector 1, thus obtaining the electrode sheet structure. The electrode sheet structure is rolled to increase the compaction density of the electrode sheet structure. For example, when the active material in active material layer 3 is lithium iron phosphate, the compaction density of the first active material sub-layer 31 and the second active material sub-layer 32 after rolling is 2.5-2.7 g / cm³. 3A functional layer 4 is provided on the surface of the compacted electrode sheet structure (i.e., a first functional sublayer 41 is provided on the side of the first active material sublayer 31 facing away from the current collector 1, and a second functional sublayer 42 is provided on the side of the second active material sublayer 32 facing away from the current collector 1). This can alleviate the mirror-like state of the surface of the first active material sublayer 31 (i.e., the surface where the first active material sublayer 31 contacts the first functional sublayer 41) and the surface of the second active material sublayer 32 (i.e., the surface where the second active material sublayer 32 contacts the second functional sublayer 42), thereby improving the electrolyte wetting speed and the electrolyte retention capacity of the electrode sheet, and thus improving the cycle performance of the battery. Moreover, the provision of the first functional sublayer 41 and the second functional sublayer 42 can improve conductivity and / or ion conduction, reduce the interfacial resistance of the electrode sheet, and thus improve the rate performance of the battery.

[0066] In this embodiment, a carbon layer 2, an active material layer 3, and a functional layer 4 are provided on both sides of the current collector 1 in the thickness direction. Compared with providing the carbon layer 2, active material layer, and functional layer 4 on one side of the current collector 1, the cycle performance of the battery can be further improved, the interface resistance of the electrode sheet can be reduced, and the rate performance of the battery can be improved.

[0067] For example, using a gravure coating process, a first sub-carbon layer 21 and a second sub-carbon layer 22 are coated on opposite sides of the current collector 1 in the thickness direction. The coating thickness of both the first sub-carbon layer 21 and the second sub-carbon layer 22 is 1 μm. The material ratio of binder, conductive agent, and dispersant in the first sub-carbon layer 21 and the second sub-carbon layer 22 is 5:94.5:0.5. The conductive agent in the first sub-carbon layer 21 and the second sub-carbon layer 22 is conductive carbon black. Using a transfer coating process, a first active material sub-layer 31 is coated on the side of the first sub-carbon layer 21 facing away from the current collector 1, and a second active material sub-layer 32 is coated on the side of the second sub-carbon layer 22 facing away from the current collector 1, resulting in an electrode sheet structure. The material ratio of active material, conductive agent, binder, and additive in the first active material sub-layer 31 and the second active material sub-layer 32 is 96:2:2:0. The active material in the first active material sub-layer 31 and the second active material sub-layer 32 is lithium iron phosphate, the conductive agent is conductive carbon black, and the binder is polyvinylidene fluoride. The above electrode sheet structure was rolled, and the compacted density of the rolled electrode sheet structure was 2.6 g / cm³. 3The immersion rate was 209 g / s. Then, using a gravure coating process, a first functional sublayer 41 was coated on the side of the first active material sublayer 31 facing away from the current collector 1, and a second functional sublayer 42 was coated on the side of the second active material sublayer 32 facing away from the current collector 1. The coating thickness of both the first functional sublayer 41 and the second functional sublayer 42 was 1 μm. The material ratio of binder, functional material, and dispersant in the first functional sublayer 41 and the second functional sublayer 42 was 5:94.5:0.5. The functional material in the first functional sublayer 41 and the second functional sublayer 42 was conductive carbon black. After setting the first functional sublayer 41 and the second functional sublayer 42, the immersion rate of the electrode sheet was 106 g / s, which is 49.28% higher than the previous electrode sheet structure. Simultaneously, the electrolyte retention capacity of the battery cell increased by 1.34%, and the internal resistance of the cell decreased by 2.19%. The battery cell is the basic building block of a battery and is an electrochemical device for storing and releasing electrical energy.

[0068] For example, all conductive agents (including the conductive agents in the first sub-carbon layer 21, the second sub-carbon layer 22, the first active material sub-layer 31, and the second active material sub-layer 32) and functional materials (i.e., the functional materials in the first functional sub-layer 41 and the second functional sub-layer 42) in the above electrode sheet structure are replaced with conductive carbon black and conductive graphite (material ratio of 1:1). The material ratio of active material, conductive agent, binder, and additive in the first active material sub-layer 31 and the second active material sub-layer 32 is replaced with 95.7:2:2:0.3 (additive is polyvinylpyrrolidone), and the rest remain unchanged. The compaction density of the rolled electrode sheet structure is 2.65 g / cm³. 3 The immersion rate was 183 / s. After coating the first functional sublayer 41 and the second functional sublayer 42 on the rolled electrode structure, the immersion rate was 80 / s, an improvement of 56.50%. At the same time, the electrolyte retention of the battery cell increased by 1.07%, and the internal resistance of the cell decreased by 2.62%.

[0069] In summary, according to the electrode sheet provided in this application, by setting a functional layer on the surface of the electrode sheet (i.e., the side of the active material layer facing away from the current collector), the surface of the electrode sheet can be wetted, the mirror-like state of the electrode sheet surface can be alleviated, the wetting speed of the electrolyte and the electrolyte retention capacity of the electrode sheet can be improved, thereby improving the cycle performance of the battery. Moreover, the setting of the functional layer can improve conductivity and / or ion conduction, reduce the interfacial resistance of the electrode sheet, and thus improve the rate performance of the battery.

[0070] Accordingly, this application also provides a battery, including the electrode sheet described in the above embodiments, which will not be repeated in detail here. The battery can be a lithium-ion battery, and the electrode sheet can be a positive electrode sheet.

[0071] In some embodiments, the battery may further include a cell. The cell may contain structures such as electrode plates, electrolyte, and separator. The electrode plates may include a positive electrode plate and a negative electrode plate.

[0072] A battery cell is used to store and release electrical energy. The negative electrode, separator, and positive electrode are assembled together by winding or stacking to form the electrode core. Then, the electrode core is placed in the cell casing, and electrolyte is injected into the cell. After processes such as formation, degassing, sealing, and capacity testing, the finished battery cell is produced. The electrode plates are used in the battery to carry out electrochemical reactions, storing and releasing electrical energy through these reactions. During charging, oxidation occurs on the positive electrode, and reduction occurs on the negative electrode, converting the active materials on both electrodes into corresponding compounds, thus storing sufficient chemical energy inside the battery. During discharging, reduction occurs on the positive electrode, and oxidation occurs on the negative electrode, releasing electrical energy through the internal chemical reactions. The electrolyte is located between the positive and negative electrodes, serving as a carrier for lithium ions. The separator is located between the positive and negative electrodes, facilitating ion conduction while physically isolating the positive and negative electrodes to prevent direct contact between the active materials, which could lead to a short circuit.

[0073] In some embodiments, the battery further includes a casing, within which the battery cells are located. The casing protects the internal components of the battery from external environmental interference and damage, ensuring the safety of battery use.

[0074] It should be noted that batteries may also include other structures, which are not specifically limited here.

[0075] In summary, according to the battery provided in this application, by setting a functional layer on the surface of the electrode sheet (i.e., the side of the active material layer facing away from the current collector), the surface of the electrode sheet can be wetted, the mirror-like state of the electrode sheet surface can be alleviated, the wetting speed of the electrolyte and the electrolyte retention capacity of the electrode sheet can be improved, thereby improving the cycle performance of the battery. Moreover, the setting of the functional layer can improve conductivity and / or ion conduction, reduce the interfacial resistance of the electrode sheet, and thus improve the rate performance of the battery.

[0076] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more.

[0077] In the description of this application, "multiple" means two or more.

[0078] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0079] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An electrode sheet, characterized in that, include: current collector; Carbon layers are located on opposite sides of the current collector; An active material layer is located on the side of the carbon layer opposite to the current collector; The functional layer is located on the side of the active material layer opposite to the current collector; The carbon layer includes a first sub-carbon layer, which is located on one side of the current collector; The active material layer includes a first active material sublayer, which is located on the side of the first sub-carbon layer away from the current collector. The functional layer includes a first functional sublayer, which is located on the side of the first active substance sublayer away from the current collector. The carbon layer further includes a second sub-carbon layer, and the first sub-carbon layer and the second sub-carbon layer are respectively located on opposite sides of the current collector; The active material layer further includes a second active material sublayer, which is located on the side of the second sub-carbon layer away from the current collector.

2. The electrode sheet according to claim 1, characterized in that, The functional layer further includes a second functional sublayer, which is located on the side of the second active material sublayer opposite to the current collector.

3. The electrode sheet according to claim 1, characterized in that, The thickness of the functional layer is 0.5-2 μm.

4. The electrode sheet according to any one of claims 1-3, characterized in that, The electrode sheet includes a positive electrode sheet.

5. A battery, characterized in that, Includes the electrode sheet as described in any one of claims 1-4.

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