Negative electrode, preparation method of negative electrode, battery monomer comprising negative electrode, battery and power utilization device

Abstract

The invention provides a negative electrode and a preparation method thereof, and a battery monomer, a battery and an electric device comprising the negative electrode, the negative electrode comprises a negative electrode current collector and a coating arranged on at least one surface of the negative electrode current collector, the coating comprises a flexible carbon material, the flexible carbon material comprises ultra-micropores with the pore diameter smaller than or equal to 0.8 nm, and the ultra-micropores are arranged on the surface of the negative electrode current collector. The pore volume of the ultramicropores with the pore diameter smaller than or equal to 0.8 nm is recorded as Vmic, the pore volume of the flexible carbon material is recorded as Vtotal, the unit is cm < 3 > / g, and the ratio of Vmic to Vtotal is larger than or equal to 65: 100.

Description

Negative electrode and preparation method thereof, as well as battery monomer, battery and electrical device containing the same Technical Field

[0001] The present application relates to a negative electrode and a preparation method thereof, as well as a battery cell, a battery and an electrical device containing the same. Background Art

[0002] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. High energy density is an irreversible trend in future battery development, and negative electrode metal-free batteries have attracted widespread attention due to their high energy density. However, negative electrode metal-free batteries often have problems such as low Coulombic efficiency and short cycle life. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art.

[0003] Summary of the Invention

[0004] The present application provides a negative electrode and a preparation method thereof, as well as a battery cell, a battery and an electrical device containing the same, which can enable the battery to have both high energy density and good cycle performance.

[0005] In a first aspect, the present application provides a negative electrode, comprising a negative electrode current collector and a coating disposed on at least one surface of the negative electrode current collector, wherein the coating comprises a flexible carbon material, the flexible carbon material comprises ultrafine pores with a pore size of less than or equal to 0.8 nm, and the pore volume of the ultrafine pores with a pore size of less than or equal to 0.8 nm is recorded as V mic The pore volume of the flexible carbon material is recorded as V total , all units are cm 3 / g, then V mic :V total ≥65:100.

[0006] The negative electrode provided in the embodiment of the present application includes a negative electrode current collector and a coating provided on at least one surface of the negative electrode current collector, wherein the coating includes a flexible carbon material. The flexible carbon material may have excellent conductivity and stability, and may construct a good conductive network at the negative electrode, thereby reducing the internal resistance of the battery. The flexible carbon material includes ultrafine pores with a pore size of less than or equal to 0.8 nm, and the pore volume V of the ultrafine pores with a pore size of less than or equal to 0.8 nm is less than or equal to 0.8 nm. mic The pore volume V of flexible carbon materials total The ratio V mic :V total≥65:100, whereby the flexible carbon material has a pore structure and the pore structure mainly includes ultramicropores with a pore size of less than or equal to 0.8nm. Ultramicropores are usually located at the edge carbon atoms of the flexible carbon material, which can reduce the overpotential of the metal (such as sodium) and can also serve as the initial nucleation site during metal deposition, thereby reducing the nucleation barrier of the metal, which is beneficial to regulating the morphology of the metal deposited at the negative electrode. Therefore, during the battery charging process, the negative electrode surface provided by the embodiment of the present application can form a uniform metal layer, and can also reduce dendrites, especially the formation and growth of sharp morphology dendrites, thereby enabling the battery to have both high energy density and good cycle performance.

[0007] In any embodiment, V mic :V total ≥70:100, optionally, 85:100≤V mic :V total ≤96:100. By further adjusting the pore volume V of ultra-micropores with a pore size of less than or equal to 0.8nm mic The pore volume V of flexible carbon materials total The ratio V mic :V total Within the above range, the morphology of metal deposition at the negative electrode can be further adjusted, and it also helps the battery to better combine high energy density and good cycle performance.

[0008] In any embodiment, the flexible carbon material includes one or more of carbon nanotubes, carbon fibers, and graphene.

[0009] In any embodiment, the carbon nanotubes include one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and single-walled / multi-walled hybrid carbon nanotubes.

[0010] In any embodiment, the graphene includes one or more of single-layer graphene, double-layer graphene, and multi-layer graphene.

[0011] In any embodiment, the carbon fiber includes one or more of polymer-based carbon fiber and pitch-based carbon fiber.

[0012] In any embodiment, the surface of the flexible carbon material has oxygen-containing functional groups, and the content of oxygen-containing functional groups in the flexible carbon material is 7-15at.%, optionally 8-13at.%. The oxygen-containing functional groups can modify the flexible carbon material, thereby expanding the interlayer spacing and increasing the metal storage space. In addition, the oxygen-containing functional groups are generally located at defect positions in the flexible carbon material, and the content of the oxygen-containing functional groups can reflect the content of defect sites in the flexible carbon material. The defect positions can form ultramicropores and can serve as initial nucleation sites during metal deposition, thereby reducing the nucleation barrier of the metal, shortening the ion diffusion distance, and constructing a sodium-philic interface, thereby facilitating the regulation of the morphology of metal deposition at the negative electrode.

[0013] In any embodiment, the oxygen-containing functional groups include one or more of carbonyl -C=O-, hydroxyl -OH, carboxylic acid -COOH, ester -COO-, and ether -O-. The binding energy of these oxygen-containing functional groups with metals is greater than the adsorption energy of the flexible carbon material itself, which helps to adjust the morphology of metal deposition at the negative electrode, making it easier for the metal to deposit at the negative electrode and helping to form a uniform metal layer, thereby enabling the battery to have both high energy density and good cycle performance.

[0014] In any embodiment, the flexible carbon material D / I G 1.40-1.90, optional 1.50-1.88, I D The Raman spectrum of the flexible carbon material is 1350±50cm -1 The integrated area of ​​the D peak at I G The Raman spectrum of the flexible carbon material is 1580±50cm -1 The integrated area of ​​the G peak at . D / I G Within the above range, the flexible carbon material has a suitable number of ultramicropores and oxygen-containing functional groups, which is beneficial to regulating the morphology of metal deposition at the negative electrode, making it easier for the metal to be deposited at the negative electrode, and helping to form a uniform metal layer, thereby enabling the battery to have both high energy density and good cycle performance.

[0015] In any embodiment, the pore volume V of the ultramicropores with a pore diameter less than or equal to 0.8 nm is mic 0.30-0.85cm 3 / g, optional 0.37-0.75cm 3 / g.

[0016] In any embodiment, the pore volume V of the flexible carbon material total 0.33-0.89cm 3 / g, optional 0.43-0.78cm 3 / g.

[0017] By further adjusting the pore volume V of ultramicropores with a pore size of less than or equal to 0.8 nm mic and / or the pore volume V of the flexible carbon material total Within the above range, the morphology of metal deposition at the negative electrode can be further adjusted, and it also helps the battery to better combine high energy density and good cycle performance.

[0018] In any embodiment, the average pore size of the flexible carbon material is 0.50-3.50 nm, optionally 0.65-1.80 nm.

[0019] In any embodiment, the specific surface area of ​​the flexible carbon material is 150-1200 m 2 / g.

[0020] In any embodiment, the interlayer spacing of the flexible carbon material 002 crystal plane is 0.35-0.40 nm. The interlayer spacing of the flexible carbon material 002 crystal plane is large, thereby increasing the metal storage space.

[0021] In any embodiment, the electrical conductivity of the flexible carbon material is 2-200 S / cm.

[0022] In any embodiment, the thickness of the coating is less than or equal to 4 μm, and can be 1-2 μm. When the thickness of the coating is within the above range, it is beneficial to adjust the morphology of the metal deposition on the negative electrode and help form a uniform metal layer, thereby enabling the battery to have good cycle performance and high energy density and high coulombic efficiency.

[0023] In any embodiment, the content of the flexible carbon material in the coating is 60 wt% or greater, based on the total weight of the coating. This helps adjust the morphology of metal deposition at the negative electrode, making it easier for the metal to deposit at the negative electrode and facilitating the formation of a uniform metal layer, thereby enabling the battery to achieve both high energy density and good cycle performance.

[0024] In any embodiment, the coating further comprises a binder, and the content of the binder is less than 40 wt %, based on the total weight of the coating.

[0025] In any embodiment, the negative electrode current collector includes one or more of a metal matrix and a composite matrix.

[0026] In any embodiment, the thickness of the negative electrode current collector is 1-20 μm.

[0027] The second aspect of the present application provides a method for preparing a negative electrode, comprising the steps of: providing an initial flexible carbon material; placing the initial flexible carbon material in a micro-oxygen atmosphere for heat treatment, and obtaining a flexible carbon material after the end, wherein the flexible carbon material includes ultrafine pores with a pore diameter of less than or equal to 0.8 nm, and the pore volume of the ultrafine pores with a pore diameter of less than or equal to 0.8 nm is recorded as V mic The pore volume of the flexible carbon material is recorded as V total , all units are cm 3 / g, then V mic :V total ≥65:100; dispersing the obtained flexible carbon material in a solvent to prepare a coating slurry; coating the coating slurry on at least one surface of the negative electrode current collector, and obtaining a negative electrode after drying.

[0028] In any embodiment, the micro-oxygen atmosphere includes oxygen, and the volume fraction of the oxygen is 15%-40%, optionally 18%-30%. Optionally, the micro-oxygen atmosphere further includes one or more of N2, He, Ar, CO, CO2, and H2O.

[0029] In any embodiment, the heat treatment temperature is 600°C-1000°C, and can be optionally 650°C-800°C.

[0030] In any embodiment, the heat treatment time is 1-3 hours.

[0031] In the step of placing the initial flexible carbon material in a micro-oxygen atmosphere for heat treatment, by adjusting the volume fraction of oxygen, the heat treatment temperature, the heat treatment time, etc. within the above range, the formed flexible carbon material can have a suitable number of ultra-micropores with a pore size of less than or equal to 0.8 nm and oxygen-containing functional groups, which is beneficial to adjust the morphology of metal deposition at the negative electrode, making the metal more easily deposited at the negative electrode, and helping to form a uniform metal layer, thereby enabling the battery to have both high energy density and good cycle performance.

[0032] In any embodiment, the coating slurry further includes a binder.

[0033] A third aspect of the present application provides a battery cell, comprising the negative electrode of the first aspect of the present application, or the negative electrode prepared by the method of the second aspect of the present application.

[0034] In any embodiment, the battery cell comprises a negative electrode-less sodium metal battery cell.

[0035] A fourth aspect of the present application provides a battery, which is the battery cell of the third aspect of the present application.

[0036] A fifth aspect of the present application provides an electrical device comprising the battery of the fourth aspect of the present application.

[0037] The battery provided in this application can have both high energy density and good cycle performance. The electrical device provided in this application includes the battery provided in this application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0039] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0040] FIG. 2 is an exploded schematic diagram of an embodiment of the battery cell of FIG. 1 .

[0041] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0042] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0043] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0044] FIG6 is a schematic diagram of an embodiment of an electric device including the battery of the present application as a power source.

[0045] In the accompanying drawings, which are not necessarily drawn to scale, reference numerals are as follows: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 battery cell, 51 housing, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0046] Below, the negative electrode and its preparation method, as well as the battery cell, battery and electrical device containing the negative electrode of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0047] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0049] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0050] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0051] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0052] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0053] In this application, the terms "plurality" and "multiple" refer to two or more.

[0054] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0055] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0056] Unless otherwise specified, all ratio parameters involved in this application are compared in the same unit. For example, the ratio of the pore volume of A to that of B is 1:1, and the units of the pore volumes of A and B are the same.

[0057] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module, or a battery pack.

[0058] A battery cell is the smallest unit of a battery, independently capable of charging and discharging. A battery cell can be cylindrical, flat, rectangular, or in other shapes, though this is not a limitation in the present invention. Figure 1 shows a battery cell 5 with a rectangular structure as an example.

[0059] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed series via a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbeam or longitudinal beam.

[0060] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0061] A battery cell generally includes an electrode assembly. The electrode assembly generally includes a positive electrode and a negative electrode. The electrode assembly can be a wound structure or a laminated structure, which is not limited in the present embodiment.

[0062] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly and electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging can also be a soft package, such as a bag-type soft package. The soft package can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0063] In some embodiments, as shown in Figure 2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, which together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening, thereby sealing the receiving cavity. The electrode assembly 52 is enclosed in the receiving cavity. The number of electrode assemblies 52 contained in a battery cell 5 can be one or more, and can be adjusted according to needs.

[0064] In some embodiments, battery cells can be assembled into a battery module. The number of battery cells contained in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 3 is a schematic diagram of a battery module 4 as an example. As shown in Figure 3, in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length of the battery module 4. Of course, they can also be arranged in any other manner. The multiple battery cells 5 can further be fixed by fasteners.

[0065] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0066] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0067] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing comprises an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the housing.

[0068] The battery cells provided in the embodiments of the present application may include negative electrode-free sodium metal battery cells, etc., which are not limited in the embodiments of the present application.

[0069] A negative electrode metal-free battery cell generally refers to a battery cell that does not actively set a negative electrode active material layer on the negative electrode side during the manufacturing process of the battery cell. For example, during the manufacturing process of the battery cell, a metal layer is not set at the negative electrode through processes such as coating or deposition, or a negative electrode active material layer is formed by a carbonaceous active material layer. During the first charge, ions gain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metal phase. During discharge, the metal can be converted into metal ions and return to the positive electrode, realizing cyclic charge and discharge. Compared with other battery cells, negative electrode metal-free batteries can achieve higher energy density because they do not have a negative electrode active material layer.

[0070] In some embodiments, to improve battery performance, the negative electrode side of a negative electrode metal-free battery may also be provided with some conventional negative electrode active materials, such as carbon materials. Although these materials have a certain capacity, their content is relatively small and they are not used as the primary negative electrode active material in the battery cell. Therefore, the battery cell thus constructed can still be considered a negative electrode metal-free battery cell.

[0071] The CB value of a negative electrode metal-free battery is generally very small. For example, in some embodiments, the CB value of a negative electrode metal-free battery may be less than or equal to 0.1.

[0072] The CB value is the unit area capacity of the negative electrode in a battery cell divided by the unit area capacity of the positive electrode. Because negative-electrode-free metal battery cells contain no or only a small amount of negative electrode active material, the unit area capacity of the negative electrode is small, and the CB value is very small, for example, usually less than or equal to 0.1.

[0073] The metal deposited on the negative electrode in a negative electrode metal-free battery has a high activity and nucleation potential, and is easily reacted with the electrolyte, resulting in uneven deposition of the metal on the surface of the negative electrode current collector, which can easily lead to instability of the solid electrolyte interface (SEI) film formed on the negative electrode surface. Therefore, negative electrode metal-free batteries often have problems such as low Coulomb efficiency and short cycle life. In addition, during the battery charging process, the metal is directly deposited on the negative electrode current collector, which will also cause the volume of the negative electrode to change, and in turn will bring great challenges to the structural design and assembly of the battery.

[0074] Another problem with negative electrode metal-free batteries is the lack of control over the morphology of the metal deposited on the negative electrode, which makes it easy for dendrites to grow on the negative electrode. The continued growth of dendrites will pierce the separator and cause a short circuit inside the battery. Providing a layer of carbon material on the surface of the negative electrode current collector helps to regulate the deposition behavior of the metal. Currently, the carbon materials used in the negative electrode are mostly prepared by hard template method, soft template method, template-free method, chemical activation method or physical activation method. The pore structure of the carbon material thus formed is mostly mesoporous structure and / or macroporous structure. The controllability of the metal morphology is still insufficient. During charging, the metal will still be unevenly deposited on the negative electrode surface, which makes it easy for dendrites to grow on the negative electrode surface, thereby hindering the capacity of the battery and reducing the energy density of the battery.

[0075] In view of this, the inventors improved the structure of the negative electrode.

[0076] The negative electrode provided in the embodiment of the present application includes a negative electrode current collector and a coating disposed on at least one surface of the negative electrode current collector. The coating includes a flexible carbon material, the flexible carbon material includes ultrafine pores with a pore size of less than or equal to 0.8 nm, and the pore volume of the ultrafine pores with a pore size of less than or equal to 0.8 nm is denoted as V. mic , the pore volume of the flexible carbon material is recorded as V total , then V mic :V total ≥65:100. The negative electrode provided in the embodiments of the present application includes a negative electrode current collector and a coating disposed on at least one surface of the negative electrode current collector, the coating comprising a flexible carbon material. Flexible carbon materials generally refer to carbon materials that can maintain good performance after being bent, folded, twisted, compressed, stretched, or even deformed into any shape.

[0077] Flexible carbon materials can have excellent conductivity and stability, and can build a good conductive network at the negative electrode, thereby reducing the internal resistance of the battery. The flexible carbon material includes ultra-micropores with a pore size of less than or equal to 0.8nm, and the pore volume V of the ultra-micropores with a pore size of less than or equal to 0.8nm is less than or equal to 0.8nm. mic The pore volume V of flexible carbon materials total The ratio V mic :V total ≥65:100, whereby the flexible carbon material has a pore structure and the pore structure mainly includes ultramicropores with a pore size of less than or equal to 0.8nm. Ultramicropores are usually located at the edge carbon atoms of the flexible carbon material, which can reduce the overpotential of the metal (such as sodium) and can also serve as the initial nucleation site during the deposition of the metal (such as sodium), thereby reducing the nucleation barrier of the metal (such as sodium), and thus facilitating the regulation of the morphology of the metal deposited at the negative electrode. Therefore, during the battery charging process, the negative electrode surface provided by the embodiment of the present application can form a uniform metal layer, and can also reduce dendrites, especially the formation and growth of sharp-shaped dendrites, thereby enabling the battery to have both high energy density and good cycle performance.

[0078] Pore ​​volume can be measured by nitrogen adsorption at 77K (i.e., liquid nitrogen temperature). Testing standards can refer to GB / T 21650-2008 and GB / T 19587-2017. The testing instrument can be a specific surface area and pore size distribution tester, such as the MFA-100 series, SSA-7000 series, SSA-4000 series, etc., but this embodiment of the present application is not limited to this.

[0079] An exemplary test method is as follows: the sample is degassed by heating and vacuuming to remove impurities physically adsorbed on the sample surface; the sample is then weighed and placed in liquid nitrogen; and the nitrogen adsorption amount of the sample is then measured at different pre-set pressure points at liquid nitrogen temperature to obtain a nitrogen adsorption isotherm of the sample.

[0080] The nitrogen adsorption isotherm of the flexible carbon material in the negative electrode provided in the embodiment of the present application conforms to the type I adsorption isotherm (IUPAC classification).

[0081] The data obtained by nitrogen adsorption test can be used to obtain the pore size distribution diagram using the BJH method. The peak area (integral area) of pores of different pore sizes on the pore size distribution diagram is fitted to obtain the pore volume V of ultramicropores with a pore size of less than or equal to 0.8 nm. mic , the pore volume V of flexible carbon materials total And the ratio of the two V mic :V total .

[0082] In some embodiments, V mic :V total It can be ≥70:100, ≥75:100, ≥80:100, ≥85:100, ≥90:100.

[0083] Optionally, 65:100≤V mic :V total ≤96:100, 70:100≤V mic :V total ≤96:100, 75:100≤V mic :V total ≤96:100, 80:100≤V mic :V total ≤96:100, 85:100≤V mic :V total ≤96:100, 90:100≤V mic :V total ≤96:100.

[0084] By further adjusting the pore volume V of ultramicropores with a pore size of less than or equal to 0.8 nm mic The pore volume V of flexible carbon materials total The ratio V mic :V total Within the above range, the morphology of metal deposition at the negative electrode can be further adjusted, and it also helps the battery to better achieve both high energy density and good cycle performance.

[0085] In some embodiments, the pore volume V of ultramicropores with a pore diameter of 0.8 nm or less is mic Can be 0.30-0.85cm 3 / g, optional 0.37-0.75cm 3 / g.

[0086] In some embodiments, the pore volume V of the flexible carbon material total Can be 0.33-0.89cm 3 / g, optional 0.43-0.78cm 3 / g.

[0087] By further adjusting the pore volume V of ultramicropores with a pore size of less than or equal to 0.8 nm mic and / or the pore volume V of the flexible carbon material total Within the above range, the morphology of metal deposition at the negative electrode can be further adjusted, and it also helps the battery to better combine high energy density and good cycle performance.

[0088] In some embodiments, the flexible carbon material may include one or more of carbon nanotubes, carbon fibers, and graphene.

[0089] Optionally, the carbon nanotubes may include one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and single-walled / multi-walled hybrid carbon nanotubes.

[0090] Optionally, the graphene may include one or more of single-layer graphene, double-layer graphene, and multi-layer graphene.

[0091] Optionally, the carbon fibers may include one or more of polymer-based carbon fibers and pitch-based carbon fibers. As an example, the polymer-based carbon fibers may include, but are not limited to, polyacrylonitrile (PAN)-based carbon fibers.

[0092] In some embodiments, the surface of the flexible carbon material has oxygen-containing functional groups, and the content of oxygen-containing functional groups in the flexible carbon material may be 7-15 at.%, optionally 8-13 at.%.

[0093] Oxygen-containing functional groups can modify flexible carbon materials, thereby expanding the interlayer spacing and increasing the metal storage space. In addition, oxygen-containing functional groups are usually located at defect positions in flexible carbon materials. The content of oxygen-containing functional groups can reflect the content of defect sites in flexible carbon materials. The defect positions can form ultramicropores and can serve as initial nucleation sites during metal (such as sodium) deposition, thereby reducing the nucleation barrier of metal (such as sodium), shortening the ion diffusion distance and constructing a sodium-philic interface, which is beneficial to regulating the morphology of metal deposition at the negative electrode.

[0094] The content of oxygen-containing functional groups can be measured by X-ray photoelectron spectroscopy (XPS). The type of functional group can be determined based on the peak position, and the content of oxygen-containing functional groups can be calculated based on the integrated area of ​​the peaks corresponding to different functional groups.

[0095] In some embodiments, the oxygen-containing functional group may include one or more of a carbonyl group -C=O-, a hydroxyl group -OH, a carboxylic acid group -COOH, an ester group -COO-, and an ether group -O-.

[0096] The binding energy of these oxygen-containing functional groups with metals (such as sodium) is greater than the adsorption energy of the flexible carbon material itself, which is beneficial for regulating the morphology of metal deposition at the negative electrode, making it easier for the metal to deposit at the negative electrode and helping to form a uniform metal layer, thereby enabling the battery to have both high energy density and good cycle performance.

[0097] Taking the deposition of sodium metal as an example, the binding energies of carbonyl -C=O-, hydroxyl -OH, carboxylic acid -COOH, ether -O-, and ester -COO- with sodium metal are -2.82ev, -0.93ev, -1.3ev, -1.18ev, and -1.79ev, respectively, which are all greater than the adsorption energy of the flexible carbon material itself (i.e., -0.78ev), indicating that sodium metal is more easily deposited on the negative electrode.

[0098] In some embodiments, the flexible carbon material D / I G It can be 1.40-1.90, optional 1.50-1.88, I D The Raman spectrum of the flexible carbon material is 1350±50cm -1 The integrated area of ​​the D peak at I G The Raman spectrum of the flexible carbon material is 1580±50cm -1 The integrated area of ​​the G peak at .

[0099] Flexible Carbon Materials I D / I GWithin the above range, the flexible carbon material has a suitable number of ultramicropores and oxygen-containing functional groups, which is beneficial to regulating the morphology of metal deposition at the negative electrode, making it easier for the metal to be deposited at the negative electrode, and helping to form a uniform metal layer, thereby enabling the battery to have both high energy density and good cycle performance.

[0100] In some embodiments, the average pore size of the flexible carbon material may be 0.50-3.50 nm, optionally 0.65-1.80 nm.

[0101] The average pore size of the flexible carbon material is well known in the art and can be measured using instruments and methods known in the art. For example, it can be tested by nitrogen adsorption method at a test temperature of 77K. The test standards can refer to GB / T21650-2008 and GB / T 19587-2017. The test instrument can be a specific surface area and pore size distribution tester, such as the MFA-100 series, SSA-7000 series, SSA-4000 series, etc., which is not limited in the embodiments of the present application.

[0102] In some embodiments, the specific surface area of ​​the flexible carbon material can be 150-1200 m 2 / g.

[0103] The specific surface area of ​​the flexible carbon material is a well-known term in the art and can be measured using instruments and methods known in the art. For example, it can be tested by nitrogen adsorption method and then calculated by BET method, with the test temperature being 77K. The test standards can refer to GB / T 21650-2008 and GB / T 19587-2017. The test instrument can be a specific surface area and pore size distribution tester, such as the MFA-100 series, SSA-7000 series, SSA-4000 series, etc., which is not limited in the embodiments of the present application.

[0104] In some embodiments, the interlayer spacing of the flexible carbon material 002 crystal plane can be 0.35-0.40 nm. The larger interlayer spacing of the flexible carbon material 002 crystal plane can increase the metal storage space.

[0105] The interlayer spacing of the 002 crystal plane of the flexible carbon material is well known in the art and can be measured using instruments and methods known in the art. For example, an X-ray diffractometer (such as Bruker D8 Discover) can be used for testing. The test can refer to JIS K 0131-1996 and JB / T 4220-2011 to obtain the average interlayer spacing d of the 002 crystal plane in the crystal structure of the flexible carbon material. 002 In the X-ray diffraction analysis test, CuKα rays can be used as the radiation source, and the ray wavelength λ can be The scanning 2θ angle range may be 20°-80°, and the scanning rate may be 4° / min.

[0106] In some embodiments, the electrical conductivity of the flexible carbon material can be 2-200 S / cm.

[0107] The electrical conductivity of flexible carbon materials can be measured by testing their resistivity. The reciprocal of the resistivity is the electrical conductivity. The test temperature is 25°C and the test standard can refer to GB / T 32993-2016.

[0108] In some embodiments, the coating thickness may be less than or equal to 4 μm, and may be 1-2 μm. When the coating thickness is within the above range, it is beneficial to adjust the morphology of the metal deposition on the negative electrode and help form a uniform metal layer, thereby enabling the battery to have good cycle performance. Furthermore, it can also enable the battery to have high energy density and high coulombic efficiency.

[0109] In some embodiments, the flexible carbon material content in the coating can be greater than 60% based on the total weight of the coating. This helps adjust the morphology of metal deposition at the negative electrode, making it easier for the metal to deposit at the negative electrode and facilitating the formation of a uniform metal layer, thereby enabling the battery to achieve both high energy density and good cycle performance.

[0110] In some embodiments, the coating further comprises a binder. Optionally, the binder content is less than 40 wt %, based on the total weight of the coating. Optionally, the binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), sodium carboxymethyl cellulose (CMC), and carboxymethyl chitosan (CMCS).

[0111] The content of flexible carbon material in the coating can be tested by thermogravimetric analysis.

[0112] In some embodiments, the thickness of the negative electrode current collector may be 1-20 μm, and may be optionally 3-12 μm, which is not limited in the embodiments of the present application.

[0113] In some embodiments, the negative electrode current collector may include one or more of a metal matrix and a composite matrix.

[0114] In some embodiments, the metal matrix may also have a porous structure.

[0115] As examples of the metal substrate, one or more of copper foil, aluminum foil, nickel foil, titanium foil, copper alloy foil, aluminum alloy foil, nickel alloy foil, titanium alloy foil, copper mesh, nickel mesh, foamed copper, and foamed nickel may be used.

[0116] The composite matrix may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0117] [Preparation method]

[0118] The present invention also provides a method for preparing the negative electrode.

[0119] The method comprises the steps of: providing an initial flexible carbon material; placing the initial flexible carbon material in a micro-oxygen atmosphere for heat treatment, and obtaining a flexible carbon material after the heat treatment, wherein the obtained flexible carbon material comprises ultramicropores with a pore size of less than or equal to 0.8 nm, and the pore volume of the ultramicropores with a pore size of less than or equal to 0.8 nm is recorded as V mic , the pore volume of the flexible carbon material is recorded as V total , then V mic :V total ≥65:100; dispersing the obtained flexible carbon material in a solvent to prepare a coating slurry; coating the coating slurry on at least one surface of the negative electrode current collector, and obtaining the negative electrode after drying.

[0120] By placing the initial flexible carbon material in a micro-oxygen atmosphere for heat treatment, oxygen-containing functional groups can be introduced into the flexible carbon material. The oxygen-containing functional groups can replace the carbon atoms at the edge of the flexible carbon material and form ultramicropores.

[0121] In some embodiments, the initial flexible carbon material may include one or more of carbon nanotubes, carbon fibers, and graphene. The initial flexible carbon material may be commercially available.

[0122] In some embodiments, the micro-oxygen atmosphere may include oxygen, and the volume fraction of oxygen may be 15%-40%, optionally 18%-30%.

[0123] In some embodiments, the micro-oxygen atmosphere may further include one or more of N2, He, Ar, CO, CO2, and H2O.

[0124] In some embodiments, the slightly oxygenated atmosphere may be air.

[0125] In some embodiments, the initial flexible carbon material is placed in a micro-oxygen atmosphere for heat treatment at a temperature of 600°C-1000°C, optionally 650°C-800°C.

[0126] In some embodiments, the initial flexible carbon material may be placed in a micro-oxygen atmosphere for heat treatment for 1-3 hours.

[0127] In the step of placing the initial flexible carbon material in a micro-oxygen atmosphere for heat treatment, by adjusting the volume fraction of oxygen, the heat treatment temperature, the heat treatment time, etc. within the above range, the formed flexible carbon material can have a suitable number of ultra-micropores with a pore size less than or equal to 0.8 nm and oxygen-containing functional groups (the oxygen-containing functional groups can include one or more of carbonyl -C=O-, hydroxyl -OH, carboxylic acid group -COOH, ester group -COO-, ether group -O-), which is beneficial to adjust the morphology of metal deposition at the negative electrode, making the metal easier to deposit at the negative electrode, and helping to form a uniform metal layer, thereby enabling the battery to have both high energy density and good cycle performance.

[0128] In some embodiments, the solvent includes one or more of water and organic solvents, which is not limited in the embodiments of the present application.

[0129] In some embodiments, the coating slurry may further include a binder. Optionally, the binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), sodium carboxymethyl cellulose (CMC), and carboxymethyl chitosan (CMCS).

[0130] The preparation method provided in the embodiment of the present application can prepare the above negative electrode. The parameters of the negative electrode can refer to the above negative electrode and will not be repeated here. In the negative electrode preparation process, unless otherwise specified, the equipment and raw materials used can be commercially available.

[0131] [positive electrode]

[0132] The battery cell includes a positive electrode.

[0133] The positive electrode includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and comprising a positive electrode active material. The positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0134] The positive electrode active material may be a material known in the art. For example, the positive electrode active material may include, but is not limited to, one or more of sodium-containing transition metal oxides, polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue-based materials.

[0135] As an example, the positive electrode active material may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2、NaNi 1 / 2 Mn 1 / 2 O2、Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2、Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2、NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2、Na 2 / 3 Cu 1 / 3 Mn 2 / 3 O2、Na 2 / 3 Li 1 / 3 Ni 2 / 3 O2、NaNi 0.5 Co 0.5 O2、Na 7 / 9 Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 O2、Na 2 / 3 Li 1 / 3 Mn 1 / 2 Ti 1 / 6 O2、NaNi 0.5 Fe 0.5 O2、NaCo 0.5 Fe 0.5 O2、NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2、NaCu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials and general formula X p M' q (PO4) r O x Y 3-x One or more materials. p M' q (PO4) r O x Y 3-x , 0<p≤4, 0<q≤2, 1≤r≤3, 0≤x≤2, X includes H + 、Li + 、Na + , K + and NH4+ M' comprises a transition metal, which may be selected from one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn; and Y comprises a halogen, which may be selected from one or more of F, Cl and Br. These positive electrode active materials may be used alone or in combination of two or more.

[0136] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. As examples, the positive electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0137] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The present application does not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylic resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) One or more.

[0138] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0139] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0140] [Electrolytes]

[0141] The battery cell includes an electrolyte. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected according to needs. For example, the electrolyte can include one or more of a solid electrolyte, a gel electrolyte, and a liquid electrolyte (i.e., an electrolyte solution).

[0142] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and a solvent.

[0143] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the electrolyte salt can include one or more of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0144] The type of solvent is not specifically limited and can be selected according to actual needs. For example, it can include one or more of ester solvents, sulfone solvents, and ether solvents. In some embodiments, as an example, the solvent can include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (M B), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), diethyl sulfone (ESE), tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, dimethoxymethane, diethoxymethane, dipropoxymethane, 1,2-dimethoxyethane, 1,2-dimethoxypropane, 1,2-diethoxyethane, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or one or more thereof.

[0145] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0146] [Isolation film]

[0147] Battery cells using electrolytes, as well as some battery cells using solid electrolytes, may also include a separator. The separator is placed between the positive and negative electrodes to prevent internal short circuits.

[0148] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0149] In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0150] The preparation method of battery cells is well known. In some embodiments, the positive electrode, separator, negative electrode and electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a lamination process. The electrode assembly is placed in an outer package, dried, and then injected with the above-mentioned electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a battery cell is obtained. Multiple battery cells can also be further connected in series, in parallel or in a mixed manner to form a battery module. Multiple battery modules can also be connected in series, in parallel or in a mixed manner to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0151] Electrical devices

[0152] The present application also provides an electrical device, which includes a battery provided in the present application. The battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0153] The electrical device can select the type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0154] Figure 6 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0155] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0156] Example

[0157] The following examples describe the present disclosure in more detail. These examples are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing. The instruments used in the examples are commercially available.

[0158] Example 1

[0159] Commercially available single-walled carbon nanotubes (non-porous structure, I D / I G The specific surface area is 300m 2 / g, the interlayer spacing of the 002 crystal plane is 0.34nm) was placed in an air atmosphere and heat treated at 600℃ for 2h, and a flexible carbon material was obtained after the treatment.

[0160] The flexible carbon material and binder CMC were dispersed in deionized water at a weight ratio of 70:30 to prepare a coating slurry. The coating slurry was then applied to the negative electrode current collector aluminum foil and dried to obtain the negative electrode. The coating thickness was 2 nm.

[0161] The positive electrode active material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, conductive agent carbon black Super P, and binder polyvinylidene fluoride (PVDF) are ground and mixed in a weight ratio of 90:5:5. An appropriate amount of solvent N-methylpyrrolidone (NMP) is added and stirred to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, followed by drying and cold pressing to obtain the positive electrode.

[0162] Equal volumes of ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed to obtain an organic solvent, and then anhydrous NaClO4 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0163] The positive electrode, separator (polypropylene film with a thickness of 12 μm) and negative electrode prepared above were cut into discs of appropriate size and stacked in order. They were assembled in the order of negative electrode shell-negative electrode-separator-positive electrode-positive electrode shell. The separator was soaked with the above electrolyte, and then compacted to obtain a button battery.

[0164] Examples 2 to 5

[0165] The preparation method of the button cell is similar to that of Example 1, except that the heat treatment temperature is different when preparing the flexible carbon material. The heat treatment temperature of Example 2 is 700°C, the heat treatment temperature of Example 3 is 800°C, the heat treatment temperature of Example 4 is 900°C, and the heat treatment temperature of Example 5 is 1000°C.

[0166] Examples 6 to 8

[0167] The preparation method of the button cell is similar to that of Example 1, except that the heat treatment atmosphere during the preparation of the flexible carbon material is different, namely a mixture of oxygen and argon. The volume fraction of oxygen in the heat treatment atmosphere of Example 6 is 15%, the volume fraction of oxygen in the heat treatment atmosphere of Example 7 is 30%, and the volume fraction of oxygen in the heat treatment atmosphere of Example 8 is 40%.

[0168] Examples 9 to 13

[0169] The preparation method of the button cell was similar to that of Example 1, except that the thickness of the coating in the negative electrode was different. The coating thickness of Example 9 was 0.5 μm, the coating thickness of Example 10 was 1 μm, the coating thickness of Example 11 was 1.5 μm, the coating thickness of Example 12 was 4 μm, and the coating thickness of Example 13 was 5 μm.

[0170] Example 14

[0171] The preparation method of the button cell is similar to that of Example 1, except that the type of initial flexible carbon material used in the preparation of the flexible carbon material is different.

[0172] Commercially available multilayer graphene (non-porous structure, I D / I G The specific surface area is 700m 2 / g, the interlayer spacing of the 002 crystal plane is 0.34nm) was placed in an air atmosphere and heat treated at 600℃ for 2h, and a flexible carbon material was obtained after the treatment.

[0173] The flexible carbon material and binder CMC were dispersed in deionized water at a weight ratio of 70:30 to prepare a coating slurry. The coating slurry was then applied to the negative electrode current collector aluminum foil and dried to obtain the negative electrode. The coating thickness was 2 nm.

[0174] Examples 15 to 17

[0175] The preparation method of the button cell is similar to that of Example 14, except that the heat treatment atmosphere and / or heat treatment temperature are different when preparing the flexible carbon material. The heat treatment temperature in Example 15 is 700°C, the heat treatment temperature in Example 16 is 1000°C, and the heat treatment temperature in Example 17 is 700°C. The heat treatment atmosphere is a mixture of oxygen and argon, with the volume fraction of oxygen being 40%.

[0176] Example 18

[0177] The preparation method of the button cell is similar to that of Example 1, except that the type of initial flexible carbon material used in the preparation of the flexible carbon material is different.

[0178] Commercially available polyacrylonitrile-based carbon fibers (non-porous structure, I D / I G is ~0.05, and the specific surface area is 1000m 2 / g, the interlayer spacing of the 002 crystal plane is 0.34nm) was placed in an air atmosphere and heat treated at 600℃ for 2h, and a flexible carbon material was obtained after the treatment.

[0179] The flexible carbon material and binder CMC were dispersed in deionized water at a weight ratio of 70:30 to prepare a coating slurry. The coating slurry was then applied to the negative electrode current collector aluminum foil and dried to obtain the negative electrode. The coating thickness was 2 nm.

[0180] Examples 19 to 21

[0181] The preparation method of the button cell is similar to that of Example 18, except that the heat treatment atmosphere and / or heat treatment temperature are different when preparing the flexible carbon material. The heat treatment temperature in Example 19 is 700°C, the heat treatment temperature in Example 20 is 1000°C, and the heat treatment temperature in Example 21 is 700°C. The heat treatment atmosphere is a mixture of oxygen and argon, with the volume fraction of oxygen being 40%.

[0182] Comparative Example 1

[0183] The preparation method of the button cell is similar to that of Example 1, except that the preparation process of the negative electrode is different.

[0184] Single-walled carbon nanotubes (non-porous structure, I D / I G The specific surface area is 300m 2 / g, 002 crystal plane interlayer spacing of 0.34nm) and binder CMC were dispersed in deionized water at a weight ratio of 70:30 to prepare a coating slurry. The coating slurry was applied to the negative electrode current collector aluminum foil and dried to obtain the negative electrode. The coating thickness was 2nm.

[0185] Comparative Example 2

[0186] The preparation method of the button cell is similar to that of Example 1, except that the preparation process of the negative electrode is different.

[0187] Single-walled carbon nanotubes (non-porous structure, I D / I G The specific surface area is 300m 2 / g, the interlayer spacing of the 002 crystal plane is 0.34nm) is mixed with KOH or K2CO3 activator in a mass ratio of 3:1, and placed in an argon atmosphere for heat treatment at 700°C for 2h; then the treated powder is placed in a 2mol / L HCl solution and treated at a constant temperature of 60°C in a water bath for 6h, and then repeatedly washed with deionized water until neutral, and then dried to obtain a flexible carbon material, and the pore structure of the flexible carbon material is mainly mesoporous and / or macroporous structure.

[0188] The flexible carbon material and binder CMC were dispersed in deionized water at a weight ratio of 70:30 to prepare a coating slurry. The coating slurry was then applied to the negative electrode current collector aluminum foil and dried to obtain the negative electrode. The coating thickness was 2 nm.

[0189] Comparative Example 3

[0190] The preparation method of the button battery is similar to that of Example 14, except that the preparation process of the negative electrode is different.

[0191] Commercially available multilayer graphene (non-porous structure, I D / I G The specific surface area is 700m 2 / g, 002 crystal plane interlayer spacing of 0.34nm) and binder CMC were dispersed in deionized water at a weight ratio of 70:30 to prepare a coating slurry. The coating slurry was applied to the negative electrode current collector aluminum foil and dried to obtain the negative electrode. The coating thickness was 2nm.

[0192] Comparative Example 4

[0193] The preparation method of the button battery is similar to that of Example 14, except that the preparation process of the negative electrode is different.

[0194] Commercially available multilayer graphene (non-porous structure, I D / I G The specific surface area is 700m 2 / g, the interlayer spacing of the 002 crystal plane is 0.34nm) is mixed with KOH or K2CO3 activator in a mass ratio of 3:1, and placed in an argon atmosphere for heat treatment at 700°C for 2h; then the treated powder is placed in a 2mol / L HCl solution and treated at a constant temperature of 60°C in a water bath for 6h, and then repeatedly washed with deionized water until neutral, and then dried to obtain a flexible carbon material, and the pore structure of the flexible carbon material is mainly mesoporous and / or macroporous structure.

[0195] The flexible carbon material and binder CMC were dispersed in deionized water at a weight ratio of 70:30 to prepare a coating slurry. The coating slurry was then applied to the negative electrode current collector aluminum foil and dried to obtain the negative electrode. The coating thickness was 2 nm.

[0196] Comparative Example 5

[0197] The preparation method of the button battery is similar to that of Example 18, except that the preparation process of the negative electrode is different.

[0198] Commercially available polyacrylonitrile-based carbon fibers (non-porous structure, I D / I G is ~0.05, and the specific surface area is 1000m 2 / g, 002 crystal plane interlayer spacing of 0.34nm) and binder CMC were dispersed in deionized water at a weight ratio of 70:30 to prepare a coating slurry. The coating slurry was applied to the negative electrode current collector aluminum foil and dried to obtain the negative electrode. The coating thickness was 2nm.

[0199] Comparative Example 6

[0200] The preparation method of the button battery is similar to that of Example 18, except that the preparation process of the negative electrode is different.

[0201] Commercially available polyacrylonitrile-based carbon fibers (non-porous structure, I D / I G is ~0.05, and the specific surface area is 1000m 2 / g, the interlayer spacing of the 002 crystal plane is 0.34nm) is mixed with KOH or K2CO3 activator in a mass ratio of 3:1, and placed in an argon atmosphere for heat treatment at 700°C for 2h; then the treated powder is placed in a 2mol / L HCl solution and treated at a constant temperature of 60°C in a water bath for 6h, and then repeatedly washed with deionized water until neutral, and then dried to obtain a flexible carbon material, and the pore structure of the flexible carbon material is mainly mesoporous and / or macroporous structure.

[0202] The flexible carbon material and binder CMC were dispersed in deionized water at a weight ratio of 70:30 to prepare a coating slurry. The coating slurry was then applied to the negative electrode current collector aluminum foil and dried to obtain the negative electrode. The coating thickness was 2 nm.

[0203] Test section

[0204] (1) Coating thickness test

[0205] Use scissors to cut the negative electrode prepared above into 6 cm × 6 cm square samples, and polish them using an ion cross-section polisher (e.g., IB-19500CP) to obtain a polished sample with a cut surface; use a transmission electron microscope to obtain a TEM image, randomly select 10 locations from the image to test the thickness of the coating, and take the average value as the test result.

[0206] (2) Battery capacity test

[0207] At 25° C., the button battery was charged at a constant current of 36 mA to 3.95 V to obtain the initial charge capacity of the button battery; and then discharged at a constant current of 36 mA to 1.5 V to obtain the initial discharge capacity of the button battery.

[0208] Initial gram capacity of the positive electrode active material (mAh / g) = first discharge capacity of the button cell / mass of the positive electrode active material.

[0209] The first coulombic efficiency of the button cell = the first discharge capacity of the button cell / the first charge capacity of the button cell.

[0210] (3) Battery cycle performance test

[0211] At 25°C, charge the button cell at a constant current of 36 mA to 3.95 V, then discharge it at a constant current of 100 mA to 1.5 V to obtain the first-cycle discharge capacity. Perform a cyclic charge-discharge test on the button cell as described above, recording the discharge capacity after each cycle until the discharge capacity after the cycle reaches 80% of the first-cycle discharge capacity. The number of cycles completed is then recorded.

[0212] The test results are shown in Tables 1 to 3.

[0213] Table 1

[0214] Table 2

[0215] Table 3

[0216] From the test results in Tables 1 to 3, it can be seen that by placing the initial flexible carbon material in a micro-oxygen atmosphere for heat treatment, oxygen-containing functional groups can be introduced into the flexible carbon material. The oxygen-containing functional groups can replace the carbon atoms at the edge of the flexible carbon material and form ultramicropores with a pore size of less than or equal to 0.8 nm.

[0217] By adjusting the pore volume V of ultramicropores with a pore size of less than or equal to 0.8 nmmic The pore volume V of flexible carbon materials total The ratio V mic :V total ≥65:100, which can reduce the overpotential of sodium and the nucleation barrier of sodium, thereby helping to regulate the morphology of sodium deposition at the negative electrode, and can also enable the battery to have high energy density, high coulombic efficiency and good cycle performance.

[0218] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode, comprising a negative electrode current collector and a coating disposed on at least one surface of the negative electrode current collector, wherein: The coating comprises a flexible carbon material, the flexible carbon material comprises ultra-micropores with a pore size of less than or equal to 0.8 nm, and the pore volume of the ultra-micropores with a pore size of less than or equal to 0.8 nm is recorded as V mic , the pore volume of the flexible carbon material is recorded as V total , all units are cm 3 / g, then V mic :V total ≥65:

100.

2. The negative electrode according to claim 1, wherein V mic :V total ≥70:100, optionally, 85:100≤V mic :V total ≤96:

100.

3. The negative electrode according to claim 1 or 2, wherein The flexible carbon material includes one or more of carbon nanotubes, carbon fibers, and graphene; Optionally, the carbon nanotubes include one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and single-walled / multi-walled mixed carbon nanotubes; and / or, Optionally, the graphene includes one or more of single-layer graphene, double-layer graphene, and multi-layer graphene; and / or, Optionally, the carbon fiber includes one or more of polymer-based carbon fiber and asphalt-based carbon fiber.

4. The negative electrode according to any one of claims 1 to 3, wherein The surface of the flexible carbon material has oxygen-containing functional groups, and the content of oxygen-containing functional groups in the flexible carbon material is 7-15 at.%, and can be optionally 8-13 at.%.

5. The negative electrode according to claim 4, wherein The oxygen-containing functional group includes one or more of a carbonyl group -C=O-, a hydroxyl group -OH, a carboxylic acid group -COOH, an ester group -COO-, and an ether group -O-.

6. The negative electrode according to any one of claims 1 to 5, wherein The flexible carbon material D / I G 1.40-1.90, optional 1.50-1.88, I D The Raman spectrum of the flexible carbon material is 1350±50cm -1 The integrated area of ​​the D peak at I G The Raman spectrum of the flexible carbon material is 1580±50cm -1 The integrated area of ​​the G peak at .

7. The negative electrode according to any one of claims 1 to 6, wherein The pore volume V of the ultra-micropores with a pore diameter of less than or equal to 0.8 nm mic 0.30-0.85cm 3 / g, optional 0.37-0.75cm 3 / g; and / or, The pore volume V of the flexible carbon material total 0.33-0.89cm 3 / g, optional 0.43-0.78cm 3 / g.

8. The negative electrode according to any one of claims 1 to 7, wherein The average pore size of the flexible carbon material is 0.50-3.50 nm, and can be 0.65-1.80 nm; and / or, The specific surface area of ​​the flexible carbon material is 150-1200m 2 / g; and / or, The interlayer spacing of the flexible carbon material 002 crystal plane is 0.35-0.40nm; and / or, The electrical conductivity of the flexible carbon material is 2-200 S / cm.

9. The negative electrode according to any one of claims 1 to 8, wherein The thickness of the coating is less than or equal to 4 μm, and can be 1-2 μm; and / or, The content of the flexible carbon material in the coating is 60 wt % or more, based on the total weight of the coating; and / or, The coating further comprises a binder, wherein the content of the binder is less than 40 wt % based on the total weight of the coating.

10. The negative electrode according to any one of claims 1 to 9, wherein: The negative electrode current collector includes one or more of a metal matrix and a composite matrix; and / or, The thickness of the negative electrode current collector is 1-20 μm.

11. A method for preparing a negative electrode, comprising the steps of: providing an initial flexible carbon material; The initial flexible carbon material is placed in a micro-oxygen atmosphere for heat treatment, and a flexible carbon material is obtained after the heat treatment, wherein: The flexible carbon material includes ultra-micropores with a pore size of less than or equal to 0.8 nm, and the pore volume of the ultra-micropores with a pore size of less than or equal to 0.8 nm is recorded as V mic , the pore volume of the flexible carbon material is recorded as V total , all units are cm 3 / g, then V mic :V total ≥65:100; Dispersing the obtained flexible carbon material in a solvent to prepare a coating slurry; The coating slurry is coated on at least one surface of a negative electrode current collector and dried to obtain a negative electrode.

12. The method according to claim 11, wherein: The micro-oxygen atmosphere includes oxygen, and the volume fraction of the oxygen is 15%-40%, and can be optionally 18%-30%; Optionally, the micro-oxygen atmosphere further includes one or more of N2, He, Ar, CO, CO2, and H2O.

13. The method according to claim 11 or 12, wherein: The heat treatment temperature is 600°C-1000°C, and can be 650°C-800°C; and / or, The heat treatment time is 1-3h.

14. The method according to any one of claims 11 to 13, wherein: The coating slurry also includes a binder.

15. A battery cell, comprising the negative electrode according to any one of claims 1 to 10, or the negative electrode prepared by the method according to any one of claims 11 to 14.

16. The battery cell according to claim 15, wherein: The battery cells include negative electrode-free sodium metal battery cells.

17. A battery comprising the battery cell according to claim 15 or 16.

18. An electrical device comprising the battery according to claim 17.

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