Negative electrode sheet, method for manufacturing the same, electrochemical cell, battery, and use thereof
By using highly stable conductive carbon materials, the problem of black spots caused by gas generation during the high-temperature static storage of negative electrode sheets has been solved, improving the cell life and overall performance of lithium-ion batteries, simplifying the production process and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CONTEMPORARY AMPEREX TECHNOLOGY CO LTD
- Filing Date
- 2024-12-05
- Publication Date
- 2026-06-05
Smart Images
Figure CN122158466A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, specifically to a negative electrode sheet and its preparation method, an electrical battery cell, a battery and its application. Background Technology
[0002] Lithium-ion batteries are increasingly being researched and applied due to their advantages such as high energy density, long cycle life and environmental friendliness. Among them, the performance of the negative electrode is one of the key factors affecting its overall performance.
[0003] To ensure product competitiveness, lithium-ion batteries often employ high-temperature settling during production to enhance cell cycle life and consistency. However, during this settling process, side reactions or electrolyte decomposition can cause the negative electrode to produce gases such as hydrogen (H2) and methane (CH4). Consequently, when gas is generated at the negative electrode, the bubbles may not be able to escape, forming a cavity between the negative electrode and the separator, thus preventing lithium ions (Li) from escaping. + The inability to transmit signals leads to black spots near the negative electrode, severely affecting the cell's lifespan and resulting in poor overall performance of the lithium-ion battery.
[0004] Therefore, there is an urgent need to provide a new type of negative electrode to solve the above problems. Summary of the Invention
[0005] In view of the above problems, this application provides a negative electrode sheet and its preparation method, an electric battery cell, a battery and its application, aiming to solve the problem that the traditional negative electrode sheet produces gas, which causes black spots in the battery, seriously affects the life of the battery cell, and results in poor overall performance of the lithium-ion battery.
[0006] In a first aspect, embodiments of this application provide a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The negative electrode active material layer includes conductive carbon, a negative electrode active material, and a binder. The conductive carbon and the negative electrode active material are bonded to the negative electrode current collector by the binder. The degree of graphitization of the conductive carbon is 30% to 93%.
[0007] The conductive carbon provided in this application has a high degree of graphitization, that is, a high degree of structural ordering, resulting in a low degree of surface defects and fewer surface defects. At the same time, it has a low specific surface area, low chemical activity, and few active sites. When such a highly stable conductive carbon is applied to the negative electrode sheet, it can reduce the sites for redox reactions, thereby reducing the amount of gas generated by the negative electrode sheet and effectively improving the black spot problem.
[0008] In some embodiments, the Raman spectral intensity ratio of the conductive carbon is 0.01 to 1.5; and / or, the specific surface area of the conductive carbon is 50 m².2 / g~80m 2 / g; and / or, the particle size Dv50 of the conductive carbon is 1.0μm to 5.0μm; and / or, the electronic conductivity of the conductive carbon is 0.001Ω×cm to 0.1Ω×cm.
[0009] By increasing the graphitization degree of conductive carbon, its Raman spectroscopy can be improved. D / I G With its smaller size, fewer surface defects, smaller specific surface area, lower chemical activity, and fewer active sites, conductive carbon, when used in negative electrode sheets, can reduce the sites for redox reactions, thereby reducing the amount of gas generated by the negative electrode sheet. Moreover, the smaller particle size (Dv50) of the conductive carbon allows it to be uniformly dispersed in the negative electrode active material layer, resulting in good conductivity throughout the layer. At the same time, the higher electronic conductivity of the conductive carbon ensures the conductivity of the negative electrode sheet and reduces its resistance, making it more suitable for various applications.
[0010] In some embodiments, the conductive carbon in the negative electrode active material layer has a mass percentage of 0.1 wt% to 2.5 wt%.
[0011] By adjusting the proportion of conductive carbon in the negative electrode active material layer, the amount of gas generated by the negative electrode sheet can be reduced while maintaining good conductivity and other properties.
[0012] In some embodiments, the weight ratio of the negative electrode active material, the conductive carbon, and the binder is 95–100:0.1–5:0.5–2.5.
[0013] By setting the weight ratio of each substance in the negative electrode active material layer within a certain range, the gas production and conductivity of the negative electrode sheet can be balanced, resulting in better overall performance of the negative electrode sheet.
[0014] In some embodiments, the negative electrode active material comprises graphite; the binder comprises styrene-butadiene rubber.
[0015] The negative electrode active material layer is prepared by dissolving graphite, styrene-butadiene rubber and highly stable conductive carbon in water, which can make the negative electrode sheet have high conductivity, resulting in less gas production and better conductivity.
[0016] In some embodiments, the graphite has a particle size Dv50 of 10 μm to 16 μm; and / or, the graphite has a specific surface area of 0.98 m². 2 / g~1.3m 2 / g; and / or, the tap density of the graphite is 1.2 g / cm³. 3 ~1.4g / cm 3 ; and / or, the specific capacity of the graphite is 340.5 mAh / g to 347.5 mAh / g.
[0017] The negative electrode formed by mixing graphite with other materials produces less gas and has good conductivity.
[0018] Secondly, embodiments of this application provide a method for preparing the above-mentioned negative electrode sheet, the method comprising:
[0019] The conductive carbon, the negative electrode active material, the thickener, and the binder are mixed in a solvent to obtain a negative electrode slurry.
[0020] The negative electrode slurry is coated on the surface of the negative electrode current collector, and after drying and cold pressing, the negative electrode sheet is obtained.
[0021] The method for preparing the negative electrode sheet provided in this application involves mixing highly stable conductive carbon with negative electrode active material, thickener, binder and solvent to obtain a negative electrode active material layer, which is then coated on the surface of the negative electrode current collector. After drying to remove the solvent, the negative electrode sheet is obtained. Because the highly stable conductive carbon has a high degree of graphitization, its surface defects and specific surface area are low, and its chemical activity is low, the amount of gas generated by the negative electrode sheet during the aging process is effectively reduced, and the generation of black spots is reduced. This improves the performance of the battery using the negative electrode sheet and extends the battery life. Moreover, the preparation method is simple and easy to implement, which is conducive to industrial production.
[0022] In some embodiments, the method for preparing the conductive carbon includes:
[0023] The original conductive carbon was placed in an inert gas protective atmosphere and graphitized at a temperature of 2000℃~3200℃ to obtain the precursor.
[0024] The precursor is subjected to depolymerization treatment to obtain the conductive carbon.
[0025] By subjecting the original conductive carbon to high-temperature graphitization under the protection of inert gas, and then depolymerizing and pulverizing the particles to obtain highly stable conductive carbon, the graphitization degree of the conductive carbon can be significantly improved, its surface defects and specific surface area can be reduced, and its chemical activity can be reduced. This significantly reduces the gas production of the negative electrode during the aging process, reduces the generation of black spots, and improves the performance and lifespan of the battery using this negative electrode. Moreover, the preparation method is simple and easy to implement, which is conducive to industrial production.
[0026] Thirdly, embodiments of this application provide an electrical battery cell, including the negative electrode sheet described above or a negative electrode sheet prepared by the above-described method for preparing the negative electrode sheet.
[0027] The negative electrode provided in this application embodiment produces less gas, effectively improving the black spot problem of the battery and exhibiting better performance.
[0028] Fourthly, embodiments of this application provide a battery comprising the aforementioned electrical battery cell.
[0029] The battery provided in this application embodiment has low gas production and good performance.
[0030] Fifthly, embodiments of this application provide an electrical device including the battery described above.
[0031] The electrical device provided in this application embodiment produces less gas, effectively improving the black spot problem and exhibiting better performance.
[0032] In another aspect, embodiments of this application provide an energy storage device, including the battery described above.
[0033] The energy storage device provided in this application embodiment has a low gas production, effectively improves the black spot problem, and has good performance.
[0034] The above description is merely an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description
[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the alternative embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:
[0036] Figure 1 This is a schematic diagram of the vehicle structure according to some embodiments of this application;
[0037] Figure 2 This is a schematic diagram of the exploded structure of a battery according to some embodiments of this application;
[0038] Figure 3 This is a schematic diagram of the exploded structure of a battery cell according to some embodiments of this application;
[0039] Figure 4 This is a schematic diagram of the structure of the electrode assembly in some embodiments of this application;
[0040] Figure 5 This is a process flow diagram of the preparation process of the negative electrode active material layer in some embodiments of this application;
[0041] Figure 6 This is a process flow diagram for preparing conductive carbon according to some embodiments of this application.
[0042] The reference numerals in the detailed embodiments are as follows:
[0043] 101. Negative electrode plate; 102. Positive electrode plate; 201. Negative electrode tab; 202. Positive electrode tab; 203. Separator; 20. Cell assembly;
[0044] 30. Battery cell; 301. Casing; 302. End cap; 303. Negative electrode adapter; 304. Positive electrode adapter; 305. Insulating component;
[0045] 40. Battery; 401. Box body; 4011. Box body; 4012. Box cover;
[0046] 50. Electrical equipment; 501. Controller; 502. Motor. Detailed Implementation
[0047] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.
[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.
[0049] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.
[0050] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0051] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.
[0052] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).
[0053] In the description of the embodiments of this application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.
[0054] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.
[0055] Lithium-ion batteries are widely used in various fields such as 3C electronics, electric vehicles, and energy storage power stations due to their advantages such as high energy density, long cycle life, and environmental friendliness. Among them, the performance of the negative electrode is one of the key factors affecting the overall performance of lithium-ion batteries.
[0056] During the use of lithium-ion batteries, the components undergo varying degrees of structural or performance changes over extended periods of operation; this is known as aging. Aging-related gas generation primarily occurs on the negative electrode side. Current manufacturing processes often involve placing lithium-ion batteries in a high-temperature environment (e.g., an oven) for a period to mitigate aging-related gas generation, thereby enhancing the cycle life and consistency of the battery cell assembly and ensuring overall performance. However, during this resting period, lithium-ion batteries experience side reactions and electrolyte decomposition, leading to the generation of gases such as H2 and CH4 on the negative electrode. If these gas bubbles cannot escape, they accumulate between the negative electrode and the separator, forming a cavity. Lithium ions cannot transport within this cavity, resulting in incomplete graphite filling and a black discoloration near the negative electrode, known as black spots. This severely impacts the battery cell assembly's lifespan and other performance characteristics, ultimately leading to poor overall performance of the lithium-ion battery.
[0057] To address the aforementioned issues, current measures include: using negative pressure technology during the high-temperature settling process to extract the gas generated during this process; or using clamps during the high-temperature settling process, clamping the clamps on multiple sides of the battery cell assembly to force out the gas generated during the high-temperature settling process. The aim is to reduce or even eliminate the gas generated during aging, thereby alleviating the black spot problem.
[0058] However, since high-temperature settling is usually carried out in an oven, negative pressure technology requires modifying the oven to enable negative pressure or purchasing equipment with built-in negative pressure, which increases costs and is time-consuming and labor-intensive. Similarly, fixtures are also very expensive, and using fixtures will also increase costs, which is not conducive to industrial production and application.
[0059] Based on the above, this application provides a negative electrode sheet. The negative electrode active material layer disposed on the surface of the negative electrode current collector in the negative electrode sheet includes conductive carbon, negative electrode active material and binder. The graphitization degree of the conductive carbon is 30% to 93%. As a result, the structural order of the conductive carbon (i.e., graphitization degree) is high, which makes its surface defect degree low and fewer surface defects. At the same time, the specific surface area of the conductive carbon is low, its chemical activity is low and its active sites are few, which reduces the sites for redox reactions, thereby significantly reducing the gas production of the negative electrode sheet, effectively improving the black spot problem, and thus improving the life and other performance of the battery cell assembly.
[0060] The batteries disclosed in some embodiments of this application can be used, but are not limited to, in electrical devices such as large-scale energy storage power stations, vehicles, ships, or aircraft, and can be used in power systems that incorporate the batteries disclosed in this application to form electrical devices or energy storage devices.
[0061] Some embodiments of this application provide an electrical device or energy storage device that uses a battery as a power source. The electrical device and energy storage device may include, but are not limited to, large-scale energy storage power stations, vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools. Among them, large-scale energy storage power stations may include, but are not limited to, large-scale battery energy storage power stations, stand-alone grid-type energy storage power stations, and pumped-storage power stations; vehicles may include, but are not limited to, new energy vehicles, gasoline vehicles, and natural gas vehicles; new energy vehicles may include, but are not limited to, pure electric vehicles, hybrid electric vehicles, and range-extended electric vehicles; spacecraft may include, but are not limited to, airplanes, rockets, space shuttles, and spacecraft; electric toys may include, but are not limited to, stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys; power tools may include, but are not limited to, metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.
[0062] For ease of explanation, the following embodiments will be described using a vehicle 50 as an example of an electrical device according to an embodiment of this application.
[0063] Figure 1 This is a structural schematic diagram of a vehicle 50 provided in some embodiments of this application. Please refer to... Figure 1 The vehicle 50 has a battery 40 installed inside it, which may be located at the bottom, front, or rear of the vehicle 50. The battery 40 can be used to power the vehicle 50, for example, it can serve as the operating power source for the vehicle 50. The vehicle 50 may also include a controller 501 and a motor 502. The controller 501 is used to control the battery 40 to supply power to the motor 502, for example, to meet the power needs of the vehicle 50 during starting, navigation, and driving.
[0064] In some embodiments of this application, the battery 40 can not only serve as the operating power source for the vehicle 50, but also as the driving power source for the vehicle 50, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 50.
[0065] In some embodiments of this application, battery 40 can be a secondary battery. Secondary batteries come in various forms, including but not limited to battery cells, battery modules, and battery packs. Here, a secondary battery refers to a battery that can be recharged after discharge to activate its active materials and continue to be used. Specifically, secondary batteries can include coin cells, rechargeable full cells, etc.
[0066] Figure 2 Exploded views of the battery 40 provided for some embodiments of this application. Please refer to... Figure 2The battery 40 includes a housing 401 and a battery cell 30. The battery cell 30 is housed within the housing 401. The housing 401 is a component that provides housing space for the battery cell 30. The housing 401 can adopt various structures.
[0067] In some embodiments, the housing 401 may include a housing body 4011 and a housing cover 4012, which cover each other and together define a receiving space for accommodating the battery cell 30. Optionally, the housing body 4011 may be a hollow structure with one end open, and the housing cover 4012 may be a plate-like structure that covers the open side of the housing body 4011.
[0068] In battery 40, there can be multiple battery cells 30, which can be connected in series, parallel, or mixed. Mixed connection refers to multiple battery cells 30 being connected in both series and parallel configurations. Multiple battery cells 30 can be directly connected in series, parallel, or mixed together, and then the entire assembly of the multiple battery cells 30 is housed within housing 401. Alternatively, battery 40 can also consist of multiple battery cells 30 first connected in series, parallel, or mixed to form battery modules, and then these battery modules are connected in series, parallel, or mixed to form a whole, which is also housed within housing 401. Battery 40 may also include other structures, such as a busbar component (…). Figure 2 (Not shown in the image) is used to achieve electrical connection between multiple battery cells 30.
[0069] The battery cell 30 can be cylindrical, flat, cuboid, or any other shape.
[0070] Figure 3 This is an exploded view of a battery cell 30 in some embodiments of this application. Please refer to... Figure 3 A single battery cell (30) refers to the basic unit that enables the interconversion of chemical energy and electrical energy, and is also the smallest unit that makes up a battery. For example... Figure 3 As shown, the battery cell 30 includes a housing 301, an end cap 302, a cell assembly 20, and an electrolyte ( Figure 3 (not shown in the image) and other functional components.
[0071] The housing 301 is a hollow structure with an opening at one end. The housing 301 is used to mate with the end cap 302 to form an internal environment that accommodates the battery cell assembly 20, electrolyte, and other functional components. The housing 301 can be of various shapes and sizes, such as cuboid, cylindrical, and hexagonal prism. Specifically, the shape of the housing 301 can be determined according to the specific shape and size of the battery cell assembly 20. The material of the housing 301 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, and plastic, etc., and is not limited thereto.
[0072] End cap 302 refers to a component that covers the opening of housing 301 and isolates the internal environment of battery cell 30 from the external environment. Optionally, the shape of end cap 302 can be adapted to the shape of housing 301 to fit housing 301, and end cap 302 can be made of a material with a certain hardness and strength (e.g., aluminum alloy). In this way, end cap 302 is not easily deformed when subjected to compression and impact, so that battery cell 300 can have higher structural strength and improved safety performance. The material of end cap 302 can be any of, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy and plastic, etc., and is not limited here.
[0073] In some embodiments, the battery cell 30 may further include functional components such as a negative electrode adapter 303 and a positive electrode adapter 304, wherein the negative electrode adapter 303 is used to connect to the negative electrode tab on the cell assembly 20. Figure 3 Electrically connected (not shown in the image), the positive electrode adapter 304 is used to connect with the positive electrode tab on the cell assembly 20 (not shown in the image). Figure 3 (Not shown) Electrical connection for outputting or inputting electrical energy to battery cell 30. Understandably, the negative electrode adapter 303 is made of conductive material, and the material of the negative electrode adapter 303 can be, but is not limited to, copper, iron, and aluminum; the positive electrode adapter 304 is made of conductive material, and the material of the positive electrode adapter 304 can be, but is not limited to, copper, iron, and aluminum.
[0074] In some embodiments, the battery cell 30 may further include an insulator 305 disposed inside the housing 301 to isolate the housing 301 from the cell assembly 20 and reduce the risk of short circuit. For example, the insulator 305 may be made of plastic or rubber.
[0075] In addition, the housing 301 may contain one or more battery cell assemblies 20.
[0076] Figure 4 This is a schematic diagram of the structure of the battery cell assembly 20 in some embodiments of this application. Please refer to... Figure 4 The cell assembly 20 is the component in the battery cell 30 where the electrochemical reaction occurs. The cell assembly 20 is mainly formed by winding or stacking an electrode structure that integrates the negative electrode 101 and the positive electrode 102 into one piece, and usually a separator 203 is provided between adjacent negative electrode 101 and positive electrode 102.
[0077] The negative electrode 101 may include a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer being coated on the surface of the negative electrode current collector. Taking a lithium-ion battery as an example, the negative electrode current collector refers to the component used to collect current. The material of the negative electrode current collector can be copper foil, which can be of various shapes, such as strips or squares, without limitation. The negative electrode active material layer may include substances such as negative electrode active material, conductive agent, thickener, and binder. The negative electrode active material refers to the material of the negative electrode that participates in the electrochemical oxidation / reduction reaction. Optionally, the negative electrode active material can be a powder, and the negative electrode active material can be, but is not limited to, graphite. The conductive agent refers to the material that collects microcurrents between the negative electrode active material and the negative electrode current collector, and can be, but is not limited to, conductive carbon, such as any one of carbon fiber, carbon nanotubes, graphene, and acetylene black. The binder is a material used to bond the negative electrode active material together to enhance the electron contact between the negative electrode active material and the current collector. It can be any of, but is not limited to, styrene-butadiene rubber (SBR), acrylonitrile, acrylate, polyvinylidene fluoride (PVDF), and carboxymethyl cellulose (CMC). Furthermore, the negative electrode active material layer can be disposed on part or all of the surface of the negative electrode current collector.
[0078] The positive electrode 102 may include a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer being coated on the surface of the positive electrode current collector. Taking a lithium-ion battery as an example, the positive electrode current collector also refers to a component used to collect current. The material of the positive electrode current collector can be aluminum foil, which can be in various shapes, such as strips or squares, without limitation. The positive electrode active material layer may include positive electrode active material, conductive agent, thickener, and binder, etc., wherein the positive electrode active material refers to the material of the positive electrode that participates in the electrochemical oxidation / reduction reaction. Optionally, the positive electrode active material can be a powder, and the positive electrode active material can be, but is not limited to, any one of lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium manganate (LMO), lithium iron manganese phosphate (LMFP), lithium nickel cobalt oxide (NCA), lithium nickel manganese oxide (LNMO), and lithium nickel cobalt manganese oxide (NCM). It should be noted that the conductive agents, thickeners, and binders in the positive electrode active material layer can be referenced from those in the negative electrode active material layer, and will not be elaborated here. Furthermore, the positive electrode active material layer can be disposed on part or all of the surface of the positive electrode current collector.
[0079] The separator 203 is a porous plastic film that allows lithium ions in the electrolyte to pass through freely, but isolates the negative electrode 101 from the positive electrode 102, preventing electrons inside the battery from passing through freely.
[0080] Both the negative and positive current collectors have uncoated portions, and these uncoated portions are provided with connecting tabs. Specifically, the negative current collector is connected to a negative tab 201, and the positive current collector is connected to a positive tab 202. During the charging and discharging process of the battery, the positive and negative active material layers react with the electrolyte. Tab 201 connects to the negative adapter 303, and the positive tab 202 connects to the positive adapter 304 to form a current loop. Of course, in some embodiments, the uncoated portions of the negative and positive current collectors each constitute a tab.
[0081] Some embodiments of this application provide a negative electrode sheet, which includes a negative current collector and a negative active material layer disposed on the surface of the negative current collector. The negative active material layer includes conductive carbon, a negative active material, and a binder, wherein the graphitization degree of the conductive carbon is 30% to 93%.
[0082] As one example, the negative electrode active material layer is disposed on one side surface of the negative electrode current collector; as another example, the negative electrode active material layer is disposed on opposite sides of the negative electrode current collector along the thickness direction.
[0083] Optionally, the graphitization degree of the conductive carbon can be 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 93%, etc.
[0084] As an example, negative electrode active materials include graphite, etc. Optionally, the graphite can be artificial graphite, natural graphite, etc.
[0085] When the negative electrode active material is graphite, the graphite particle size Dv50 is 10μm~16μm and the specific surface area is 0.98m². 2 / g~1.3m 2 / g, tap density is 1.2g / cm³ 3 ~1.4g / cm 3 The specific capacity ranges from 340.5 mAh / g to 347.5 mAh / g. Therefore, the negative electrode formed by mixing graphite with other materials exhibits low gas production and good conductivity.
[0086] Optionally, the graphite particle size Dv50 can be 10μm, 13μm, 14μm, 15μm, or 16μm, etc.; the specific surface area of the graphite can be 0.98m². 2 / g, 0.99m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g or 1.3m 2 / g, etc.; the tap density of graphite can be 1.2 g / cm³. 3 1.3g / cm 3 Or 1.4g / cm 3 The specific capacity of graphite can be 340.5 mAh / g, 341.5 mAh / g, 342.5 mAh / g, 343.5 mAh / g, 344.5 mAh / g, 345.5 mAh / g, 346.5 mAh / g, or 347.5 mAh / g, etc.
[0087] As an example, adhesives include styrene-butadiene rubber, etc.
[0088] The negative electrode sheet provided in this application has a high degree of graphitization and high degree of structural order in the conductive carbon, resulting in a low degree of surface defects, fewer surface defects, lower chemical activity, and fewer active sites. When such highly stable conductive carbon is used together with negative electrode active materials, thickeners, and binders to form a negative electrode sheet, the sites for redox reactions can be reduced, thereby reducing the amount of gas generated by the negative electrode sheet and effectively improving the black spot problem of the battery.
[0089] According to some embodiments of this application, the Raman spectral intensity ratio (Raman I) of conductive carbon D / I G The value ranges from 0.01 to 1.5.
[0090] Alternatively, the Raman spectroscopy of conductive carbon... D / I G It can be 0.01, 0.1, 0.5, 1.0, 1.2, or 1.5, etc.
[0091] By increasing the graphitization degree of conductive carbon, its Raman spectroscopy can be improved. D / I G Smaller size, lower chemical activity, and fewer active sites mean that when such highly stable conductive carbon is combined with negative electrode active materials, thickeners, and binders to form a negative electrode sheet, the sites for redox reactions can be reduced, thereby reducing the amount of gas produced by the negative electrode sheet and effectively improving the black spot problem.
[0092] According to some embodiments of this application, the specific surface area of the conductive carbon is 50 m². 2 / g~80m 2 / g.
[0093] Optionally, the specific surface area of the conductive carbon can be 50 m². 2 / g、55m 2 / g、60m 2 / g、65m 2 / g、70m 2 / g、75m 2 / g or 80m 2 / g etc.
[0094] By increasing the graphitization degree of conductive carbon and reducing surface defects, its specific surface area can be reduced, its chemical activity can be lower, and its active sites can be fewer. When such highly stable conductive carbon is used together with negative electrode active materials, thickeners, and binders to form a negative electrode sheet, the sites for redox reactions can be reduced, thereby reducing the amount of gas generated by the negative electrode sheet and effectively improving the black spot problem.
[0095] According to some embodiments of this application, the particle size Dv50 of the conductive carbon is 1.0 μm to 5.0 μm. It should be noted that Dv50 is the particle size value corresponding to a cumulative distribution percentage of conductive carbon reaching 50%.
[0096] Optionally, the particle size Dv50 of the conductive carbon can be 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm or 5.0 μm, etc.
[0097] It should be noted that the aforementioned conductive carbon specifically refers to the intermediate conductive carbon particles (i.e., secondary particles) obtained by processing multiple initial conductive carbon particles (i.e., primary particles), and then the conductive carbon (i.e., tertiary particles) obtained by processing the secondary particles. The particle size Dv50 of the primary particles is 0.02μm to 0.06μm, the particle size Dv50 of the secondary particles is 0.2μm to 0.7μm, and the particle size Dv50 of the tertiary particles is 1.0μm to 5.0μm.
[0098] By making the particle size Dv50 of conductive carbon smaller, it can be uniformly dispersed in the negative electrode active material layer, so that the conductivity of the negative electrode sheet is better throughout.
[0099] According to some embodiments of this application, the electronic conductivity of conductive carbon is 0.001Ω×cm to 0.1Ω×cm.
[0100] Optionally, the electronic conductivity of the conductive carbon can be 0.001Ω×cm, 0.01Ω×cm, or 0.1Ω×cm, etc.
[0101] By increasing the graphitization degree of the conductive carbon and its electronic conductivity, when such highly stable conductive carbon is combined with negative electrode active materials, thickeners, and binders to form a negative electrode sheet, the sites for redox reactions are reduced, thereby reducing the amount of gas generated by the negative electrode sheet while maintaining low resistance and better performance.
[0102] According to some embodiments of this application, the mass percentage of conductive carbon in the negative electrode active material layer is 0.1 wt% to 2.5 wt%.
[0103] Optionally, the mass percentage of conductive carbon in the negative electrode active material layer can be 0.1wt%, 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, or 2.5wt%, etc.
[0104] By mixing highly stable conductive carbon with a high degree of graphitization with negative electrode active materials, thickeners, and binders to prepare negative electrode sheets, the sites for redox reactions can be reduced, thereby reducing the amount of gas produced by the negative electrode sheets and effectively improving the black spot problem.
[0105] According to some embodiments of this application, the weight ratio of negative electrode active material, conductive carbon, and binder is 95-100:0.1-5:0.5-2.5.
[0106] By setting the weight ratio of each substance in the negative electrode active material layer within a certain range, the gas production and conductivity of the negative electrode can be balanced, resulting in better overall performance of the negative electrode.
[0107] Some embodiments of this application also provide a method for preparing the negative electrode sheet; please refer to [reference needed]. Figure 6 The preparation method of this negative electrode sheet includes the following steps:
[0108] S11. Conductive carbon, negative electrode active material, thickener and binder are added to solvent and mixed to obtain negative electrode slurry.
[0109] As an example, thickeners include sodium carboxymethyl cellulose or lithium carboxymethyl cellulose, which are used to adjust the slurry and disperse graphite.
[0110] As an example, the solvent includes water. Alternatively, the solvent can be deionized water, etc.
[0111] According to some embodiments of this application, the weight ratio of negative electrode active material, conductive carbon, thickener, and binder is 95-100:0.1-5:0.5-1.5:0.5-2.5.
[0112] Optionally, the weight ratio of the negative electrode active material, conductive carbon, thickener, and binder can be 95:0.1:0.5:0.5, 96.4:1:1.2:1.4, 100:1:0.5:1, 100:2:1:1, 100:3:1:1.5, 100:4:1.5:2, or 100:5:1.5:2.5, etc.
[0113] S12. The negative electrode slurry is coated on the surface of the negative electrode current collector, and after drying and cold pressing, the negative electrode sheet is obtained.
[0114] The negative electrode active material, conductive carbon, thickener, and binder in this application embodiment can all refer to the above embodiments, and will not be repeated here.
[0115] The method for preparing the negative electrode sheet provided in this application involves mixing highly stable conductive carbon with negative electrode active material, thickener, and binder in a solvent and then treating the mixture to obtain the negative electrode sheet. Because the highly stable conductive carbon has a high degree of graphitization, its surface defects and specific surface area are low, and its chemical activity is low, the amount of gas generated by the conductive carbon during the aging process is effectively reduced. This improves the performance of the battery cell assembly using the negative electrode sheet, effectively extends the battery cell assembly's lifespan, and reduces the generation of black spots in the battery. Moreover, this preparation method is simple and easy to implement, which is beneficial for industrial production.
[0116] According to some embodiments of this application, the preparation of conductive carbon is also included before preparing the negative electrode sheet. Please refer to [reference needed]. Figure 6 The method for preparing this conductive carbon includes the following steps:
[0117] S01. The original conductive carbon is placed in an inert gas protective atmosphere and graphitized at a temperature of 2000℃~3200℃ to obtain the precursor.
[0118] If the graphitization temperature is too low, the graphitization effect will be unsatisfactory, and conductive carbon with a high degree of graphitization cannot be obtained. If the graphitization temperature is too high, the energy consumption will be too high, the cost will be high, and it may also affect the conductivity of the conductive carbon. Therefore, in order to balance the degree of graphitization, conductivity, and practicality of conductive carbon, the graphitization temperature is set at 2000℃~3200℃.
[0119] Optionally, the graphitization temperature can be 2000℃, 2300℃, 2500℃, 2800℃, 3000℃, or 3200℃, etc. It should be noted that within the above-mentioned graphitization temperatures, generally the higher the temperature, the shorter the reaction time; in addition, at the same reaction time, the higher the temperature, the higher the degree of graphitization of the generated conductive carbon.
[0120] As an example, the raw conductive carbon can be commercially available conventional conductive carbon, such as conductive carbon black (Super P). Super P has a particle size Dv50 of 50 nm to 200 nm and a specific surface area of 40 m². 2 / g~70m 2 / g.
[0121] Optionally, the particle size Dv50 of Super P can be 50 μm, 80 μm, 100 μm, 150 μm, or 200 μm, etc.; the specific surface area of Super P can be 40 m². 2 / g、45m 2 / g, 50m 2 / g、55m 2 / g、60m 2 / g、65m 2 / g or 70m2 / g etc.
[0122] As an example, the inert gas can be any of nitrogen (N2), helium (He), neon (Ne), and argon (Ar).
[0123] As an example, the particle size Dv50 of the obtained precursor is 3 μm to 7 μm. Optionally, the particle size Dv50 of the precursor can be 3 μm, 4 μm, 5 μm, 6 μm, or 7 μm, etc. Compared with the final conductive carbon, the precursor has almost the same other properties, except that the high temperature of graphitization treatment causes the particles of the original conductive carbon to stick together, resulting in a larger particle size Dv50 of the precursor than that of the final conductive carbon.
[0124] S02. The precursor is depolymerized to obtain conductive carbon.
[0125] As an example, depolymerization can be used to break up and open the precursor particles by external force (e.g., mechanical force) to obtain highly stable conductive carbon with a small particle size Dv50.
[0126] By subjecting the original conductive carbon to high-temperature graphitization under the protection of an inert gas, and then depolymerizing and pulverizing the particles to obtain highly stable conductive carbon, the graphitization degree of the conductive carbon can be significantly improved, its surface defects and specific surface area can be reduced, and its chemical activity can be reduced. This significantly reduces the amount of gas produced by the conductive carbon during the aging process and reduces problems such as the formation of black spots. As a result, the performance of the battery using this negative electrode active material layer is improved, and the battery life is effectively extended. Moreover, the preparation method is simple and easy to implement, which is conducive to industrial production.
[0127] The following detailed description of highly stable conductive carbon and its preparation method is illustrated with specific embodiments.
[0128] Example 1
[0129] This embodiment provides a conductive carbon and its preparation method, including the following steps:
[0130] S1. Super P was graphitized at 3200℃ under N2 atmosphere to obtain the precursor.
[0131] S2. The precursor is depolymerized to obtain highly stable Super P.
[0132] Example 2
[0133] Same as Example 1, except that the graphitization temperature in step S1 is 3000℃.
[0134] Example 3
[0135] Same as Example 1, except that the graphitization temperature in step S1 is 2800℃.
[0136] Example 4
[0137] Same as Example 1, except that the graphitization temperature in step S1 is 2500℃.
[0138] Example 5
[0139] Same as Example 1, except that the graphitization temperature in step S1 is 2300℃.
[0140] Example 6
[0141] Same as Example 1, except that the graphitization temperature in step S1 is 2000℃.
[0142] Comparative Example 1
[0143] Same as Example 1, except that Super P has not undergone graphitization treatment.
[0144] Comparative Example 2
[0145] Same as Example 1, except that the graphitization temperature of Super P is 200°C.
[0146] Comparative Example 3
[0147] Same as Example 1, except that: after Super P graphitization, it was not subjected to depolymerization treatment.
[0148] The reaction conditions of Examples 1-6 and Comparative Examples 1-3 are summarized in Table 1 below.
[0149] Among them, Examples 2-5 are different from Example 1 except for the graphitization temperature.
[0150] Table 1
[0151] raw material Graphitization temperature Has it undergone depolymerization treatment? Example 1 Super P 3200℃ yes Example 2 Super P 3000℃ yes Example 3 Super P 2800℃ yes Example 4 Super P 2500℃ yes Example 5 Super P 2300℃ yes Example 6 Super P 2000℃ yes Comparative Example 1 Super P none yes Comparative Example 2 Super P 200℃ yes Comparative Example 3 Super P 3200℃ no
[0152] To verify the progressiveness of the embodiments of this application, the samples prepared in Examples 1-6 and Comparative Examples 1-3 were tested below:
[0153] The testing method is as follows:
[0154] 1. Graphitization degree test:
[0155] Testing was performed using an X-ray diffractometer (e.g., Bruker D8 Discover), with reference to JIS K0131-1996 and JB / T 4220-2011. The average interlayer spacing of the crystal planes of the highly stable Super P crystal structure 002 was determined to be d002. The degree of graphitization was calculated using the formula g = (0.344 - d002) / (0.344 - 0.3354) × 100%.
[0156] In the above formula, d002 is the average interlayer spacing of the crystal plane of the highly stable conductive carbon crystal structure 002, expressed in nanometers (nm), and g represents the degree of graphitization of the highly stable Super P.
[0157] 2. Specific surface area test:
[0158] According to GB / T 19587-2017, the N2 adsorption specific surface area analysis test method was used, and the specific surface area of the highly stable Super P was calculated by the gas adsorption method (Brunauer emmett teller, BET).
[0159] In the above method, the N2 adsorption specific surface area analysis test can be performed using the Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.
[0160] 3. Raman I D / I G test:
[0161] Using a Raman spectrometer, the testing conditions were: excitation wavelength of 532 nm, grating of 600 lines, objective lens of 50x, integration time of 10 s, and 3 integration cycles. A surface scan was performed to obtain the D and G peak intensities at 100 points. The Raman I intensity at these 100 points was then calculated. D / I G Remove the largest and smallest 30 Raman I values. D / I G The average of the remaining 40 points yields the Raman IF of the highly stable Super P. D / I G .
[0162] In the above method, the testing instrument can be a Horiba LabRAM HR800 Raman spectrometer.
[0163] 4. Particle size Dv50 test:
[0164] The particle size Dv50 of high-stability Super P was tested using a laser particle size analyzer, referring to the laser diffraction method for particle size distribution in GB / T 19077-2016.
[0165] In the above method, the testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.
[0166] The samples prepared in Examples 1-6 and Comparative Examples 1-3 were tested to obtain the degree of graphitization, specific surface area, and Raman spectroscopy results, respectively. D / I G The data for particle size Dv50 are shown in Table 2 below.
[0167] Table 2
[0168] Degree of graphitization (%) <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Raman I D / I G > Particle size Dv50 (μm) Example 1 90 56.5 0.20 3.9 Example 2 87 56.9 0.32 3.6 Example 3 85 57.3 0.40 3.0 Example 4 73 58.2 0.54 2.9 Example 5 67 59.8 0.66 2.5 Example 6 60 60.2 0.70 1.5 Comparative Example 1 40 61.9 1.10 2.8 Comparative Example 2 45 61.5 1.20 3.2 Comparative Example 3 48 62.1 1.21 5.0
[0169] As shown in Table 2, the processes or process parameters of Super P provided in Examples 1-6 of this application are different from those of Comparative Examples 1-3. Therefore, the Super P provided in Examples 1-6 of this application has a high degree of graphitization, low specific surface area, and Raman I emission level. D / I G Small particle size (Dv50) results in better performance.
[0170] The battery and its preparation method are described in detail below with reference to specific embodiments.
[0171] 1. Preparation of the positive electrode sheet of the battery:
[0172] (1) Lithium iron phosphate (LFP), high-stability Super P, and poly(vinylidene fluoride) (PVDF) are mixed in a mass ratio of 96:2:2, and then N-methylpyrrolidone solvent is added. After stirring evenly, a positive electrode slurry is obtained.
[0173] (2). The positive electrode slurry is coated on the surface of aluminum foil, and after drying and cold pressing, the positive electrode sheet is obtained.
[0174] 2. Preparation of the negative electrode sheet of the battery:
[0175] (1). Graphite, high-stability Super P, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed thoroughly in an appropriate amount of deionized water at a weight ratio of 96.4:1:1.2:1.4 to obtain a negative electrode slurry.
[0176] (2). The negative electrode slurry is coated onto the surface of copper foil by extrusion coating, and then dried and cold-pressed to obtain the negative electrode sheet.
[0177] 3. Preparation of the separating membrane:
[0178] A 12μm polyethylene film is used.
[0179] 4. Preparation of electrolyte:
[0180] (1). Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent;
[0181] (2). Lithium hexafluorophosphate (LiPF6) was dissolved in an organic solvent to obtain an electrolyte with a concentration of 1 mol / L.
[0182] 51. Assembly of button cell:
[0183] The prepared negative electrode sheet was placed in a vacuum drying oven and dried for later use.
[0184] A CR2430 coin cell was assembled in a glove box under an Ar atmosphere by using a lithium metal (Li) sheet, a negative electrode sheet, a 12μm polyethylene film, and an electrolyte with a concentration of 1mol / L.
[0185] 52. Assembly of a secondary full-cell battery:
[0186] The prepared positive and negative electrode sheets are arranged in order, with a 12μm polyethylene film placed between the positive and negative electrode sheets. These structures are then wound to obtain the battery cell assembly.
[0187] The battery cell assembly is placed in an outer packaging, dried, and then injected with an electrolyte solution of 1 mol / L. It then undergoes vacuum sealing, settling, formation, and shaping processes to obtain a secondary battery.
[0188] To verify the progressiveness of the embodiments of this application, the following tests were conducted on coin half-cells and secondary full-cells obtained by adding the samples prepared in Examples 1-6 and Comparative Examples 1-3 into the material of the negative electrode sheet:
[0189] The testing method is as follows:
[0190] 1. First Coulomb Efficiency Test of Button Half-Cell:
[0191] At 25℃, the coin cell was first discharged to 0.005V with a constant current of 0.15mA, allowed to stand for 5 minutes, and then discharged to 0.005V with a constant current of 10μA. The first discharge capacity of the coin cell was recorded. After that, it was charged to 2.0V with a constant current of 0.3mA, and the first charge capacity of the coin cell was recorded.
[0192] The initial coulombic efficiency of a coin cell is calculated by using the formula: Initial Coulombic Efficiency (%) = Initial Charge Capacity / Initial Discharge Capacity × 100%.
[0193] 2. First Coulomb Efficiency Test of Secondary Full Cell:
[0194] The secondary full cell was formed at 45℃ and charged at a constant current of 0.02C for 10 hours. The charging capacity at this time was recorded as C0. Then, at 25℃, the secondary full cell was discharged at a constant current of 0.2C to 2.0V. The discharge capacity at this time was recorded as D0. Then, it was charged at a constant current of 0.33C to 3.8V, and then charged at a constant voltage to a current of 0.05C. The charging capacity at this time was recorded as C1. Next, it was discharged at a constant current of 0.33C to 2.5V, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to 2.0V. Finally, it was discharged at a constant current of 0.1C to 2.0V. The discharge capacity at this time was recorded as D1.
[0195] The initial coulombic efficiency of the secondary full cell can be calculated using the formula: initial coulombic efficiency (%) = D1 / (C0-D0+C1).
[0196] 3. Gas production test after 48 hours of high-temperature standing:
[0197] At 45°C, coin cell half-cells and secondary full cells were formed separately and charged at a constant current of 0.02C for 10 hours; then charged at a constant current of 0.33C to 3.65V, and then charged at a constant voltage to a current of 0.05C; subsequently, the cell assembly was placed in a gas generation device and placed at a high temperature of 45°C for 48 hours to obtain the gas generation of coin cell half-cells and secondary full cells after 48 hours of high temperature placement.
[0198] Table 3
[0199] First-time coulomb efficiency (%) Gas production (ml) after 48 hours of high-temperature standing. Example 1 95.5 0.15 Example 2 95.2 0.17 Example 3 95.0 0.20 Example 4 94.9 0.22 Example 5 94.7 0.25 Example 6 94.6 0.28 Comparative Example 1 94.5 0.30 Comparative Example 2 94.0 0.34 Comparative Example 3 94.2 0.38
[0200] As shown in Table 3, the coin cells prepared by Super P provided in Examples 1-6 and Comparative Examples 1-3 of this application have higher initial coulombic efficiency and less gas production after being left to stand at high temperature for 48 hours, indicating better performance of the coin cells.
[0201] Table 4
[0202] First-time coulomb efficiency (%) Gas production (ml) after 48 hours of high-temperature standing. Example 1 95.5 0.15 Example 2 95.2 0.17 Example 3 95.0 0.20 Example 4 94.9 0.22 Example 5 94.7 0.25 Example 6 94.6 0.28 Comparative Example 1 94.5 0.30 Comparative Example 2 94.0 0.34 Comparative Example 3 94.2 0.38
[0203] As shown in Table 4, the secondary full cells prepared by Super P provided in Examples 1-6 and Comparative Examples 1-3 of this application have higher initial coulombic efficiencies and lower gas production after 48 hours of high-temperature standing, indicating better performance of the secondary full cells. Specifically, compared with Comparative Example 1, Example 1 reduced gas production by about 50% after 48 hours of high-temperature standing, which is a very significant improvement.
[0204] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.
Claims
1. A negative electrode sheet, characterized in that, The device includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The negative electrode active material layer includes conductive carbon, a negative electrode active material, and a binder. The conductive carbon and the negative electrode active material are bonded to the negative electrode current collector by the binder. The degree of graphitization of the conductive carbon is 30% to 93%.
2. The negative electrode sheet according to claim 1, characterized in that, The Raman spectral intensity ratio of the conductive carbon is 0.01–1.5; and / or, The specific surface area of the conductive carbon is 50 m². 2 / g~80m 2 / g; and / or, The conductive carbon has a particle size Dv50 of 1.0 μm to 5.0 μm; and / or, The conductive carbon has an electronic conductivity of 0.001 Ω×cm to 0.1 Ω×cm.
3. The negative electrode sheet according to claim 1 or 2, characterized in that, The conductive carbon in the negative electrode active material layer has a mass percentage of 0.1 wt% to 2.5 wt%.
4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that, The weight ratio of the negative electrode active material, the conductive carbon, and the binder is 95-100:0.1-5:0.5-2.
5.
5. The negative electrode sheet according to any one of claims 1 to 4, characterized in that, The negative electrode active material includes graphite; the binder includes styrene-butadiene rubber.
6. The negative electrode sheet according to claim 5, characterized in that, The graphite has a particle size Dv50 of 10 μm to 16 μm; and / or, The specific surface area of the graphite is 0.98 m². 2 / g~1.3m 2 / g; and / or, The tap density of the graphite is 1.2 g / cm³. 3 ~1.4g / cm 3 ; and / or, The specific capacity of the graphite is 340.5 mAh / g to 347.5 mAh / g.
7. A method for preparing a negative electrode sheet according to any one of claims 1 to 6, characterized in that, include: The conductive carbon, the negative electrode active material, the thickener, and the binder are mixed in a solvent to obtain a negative electrode slurry. The negative electrode slurry is coated on the surface of the negative electrode current collector, and after drying and cold pressing, the negative electrode sheet is obtained.
8. The method for preparing the negative electrode sheet according to claim 7, characterized in that, The method for preparing the conductive carbon includes: The original conductive carbon was placed in an inert gas protective atmosphere and graphitized at a temperature of 2000℃~3200℃ to obtain the precursor. The precursor is subjected to depolymerization treatment to obtain the conductive carbon.
9. A single battery cell, characterized in that, This includes negative electrode sheets prepared according to any one of claims 1 to 6 or according to the method for preparing negative electrode sheets according to claim 7 or 8.
10. A battery, characterized in that, Includes the battery cell as described in claim 9.
11. An electrical appliance, characterized in that, Includes the battery as described in claim 10.
12. An energy storage device, characterized in that, Includes the battery as described in claim 10.