Negative active material and preparation method thereof, negative pole piece, secondary battery and device

Abstract

The invention provides a negative active material and a preparation method thereof, a negative pole piece, a secondary battery and a device. The invention provides a negative electrode active material. The negative electrode active material comprises porous graphite particles and metal single atoms arranged on the porous graphite particles. The negative electrode active material is applied to a secondary battery and has relatively good high-rate charging capability.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a negative electrode active material and a preparation method thereof, a negative electrode plate, a secondary battery and a device. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] In recent years, the application range of secondary batteries such as lithium-ion batteries has become increasingly broad. For example, they are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. However, the high-rate charging capability of secondary batteries such as lithium-ion batteries has seriously restricted the development of fields such as electric vehicles, thus placing higher demands on their high-rate charging capabilities. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and one of its purposes includes: providing a negative electrode active material and its preparation method, a negative electrode plate, a secondary battery and a device. The negative electrode active material is applied to a secondary battery and has good high-rate charging capability.

[0005] A first aspect of the present application provides a negative electrode active material comprising porous graphite particles and metal single atoms disposed on the porous graphite particles.

[0006] Thus, taking lithium-ion batteries as an example, without wishing to be limited to any theory, the negative electrode active material of the present application comprises porous graphite particles and metal single atoms disposed on the porous graphite particles, which is a porous graphite material modified with metal single atoms. Because of its porous structure, it can not only increase the Li + The embedding channel can also shorten the Li + The embedding path of Li + Moreover, the metal atoms on the porous graphite particles can improve the local charge distribution on the surface of the porous graphite particles and reduce the Li + The embedding energy barrier on the graphite surface accelerates the Li + The above-mentioned negative electrode active materials synergistically improve the Li + The transport dynamics on the surface of the negative electrode active material reduces the negative electrode polarization, improves the kinetic performance of the negative electrode, and thus improves the high-rate charging capability of the secondary battery.

[0007] In some embodiments of the present application, the surface of the crystalline material of the porous graphite particles has a basal plane and an end plane connected to the basal plane, the end plane is a porous structure, and the metal single atom is provided on the end plane.

[0008] In some embodiments of the present application, the base plane is also provided with the metal single atom.

[0009] In some embodiments of the present application, the negative electrode active material satisfies at least one of the following conditions:

[0010] (1) The specific surface area of ​​the negative electrode active material is 1.2 m 2 ·g -1 ~5.0 m 2 ·g -1 ;

[0011] (2) The Dv50 particle size of the porous graphite particles is 5 μm to 50 μm;

[0012] (3) The porous graphite particles include at least one of artificial graphite and natural graphite.

[0013] In some embodiments of the present application, the negative electrode active material satisfies at least one of the following conditions:

[0014] (1) In the negative electrode active material, the mass content of the metal single atom is 0.01wt% to 0.5wt%;

[0015] (2) The graphitization degree of the negative electrode active material is 90% to 97%.

[0016] In some embodiments of the present application, the type of the metal single atom includes at least one of a transition metal and an alkaline earth metal.

[0017] In some embodiments of the present application, the types of the metal single atoms include one or more of Fe, Co, Ni, Cu, Zn, Mn, Mg and Sc.

[0018] In some embodiments of the present application, the negative electrode active material further includes at least one of N element and amorphous carbon doped in the surface layer of the porous graphite particles.

[0019] The second aspect of the present application provides a method for preparing a negative electrode active material, comprising the following steps:

[0020] The graphite particles are mixed with an alkaline ligand solution and then dried to obtain porous graphite particles;

[0021] The porous graphite particles are mixed with a metal salt solution, dried, and then heat-treated in a reducing atmosphere to obtain the negative electrode active material, wherein the metal ions in the metal salt can form a complex with the ligand.

[0022] The second aspect of the present application provides a method for preparing a negative electrode active material, comprising the following steps:

[0023] The graphite particles are mixed with an alkaline ligand solution and a metal salt solution, dried, and then heat-treated in a reducing atmosphere to obtain the negative electrode active material; wherein the metal ions in the metal salt can form a complex with the ligand.

[0024] In some embodiments of the present application, the alkaline ligand solution includes a first organic amine compound, the functionality of the organic amine group in the first organic amine compound is greater than 1, and the first organic amine compound is a basic compound.

[0025] In some embodiments of the present application, the alkaline ligand solution further includes a second organic amine compound, and the functionality of the organic amine group in the second organic amine compound is 1.

[0026] In some embodiments of the present application, the preparation method satisfies at least one of the following characteristics:

[0027] (1) The pH value of the alkaline ligand solution is 8.0-14.0;

[0028] (2) The functionality of the organic amine group in the first organic amine compound is 2 to 5;

[0029] (3) The molar mass of the first organic amine compound is less than or equal to 1000 g / mol;

[0030] (4) The molar mass of the second organic amine compound is less than or equal to 1000 g / mol.

[0031] In some embodiments of the present application, the preparation method satisfies at least one of the following characteristics:

[0032] (1) the organic amine groups in the first organic amine compound and the second organic amine compound each independently include a primary amine group;

[0033] (2) The molar mass of the first organic amine compound is less than or equal to 500 g / mol;

[0034] (3) The molar mass of the second organic amine compound is less than or equal to 500 g / mol;

[0035] (4) The first organic amine compound and the second organic amine compound have 1 to 10 carbon atoms.

[0036] In some embodiments of the present application, the preparation method satisfies at least one of the following characteristics:

[0037] (1) The first organic amine compound includes ethylenediamine;

[0038] (2) The second organic amine compound includes at least one of methylamine and ethylamine.

[0039] In some embodiments of the present application, the metal salt solution satisfies at least one of the following characteristics:

[0040] (1) The metal element in the metal salt solution includes at least one of a transition metal and an alkaline earth metal;

[0041] (2) The metal salt in the metal salt solution includes one or more of hydrochloride, nitrate and sulfate;

[0042] (3) The concentration of the metal salt solution is 0.001 mol·L -1 ~1mol·L -1 ;

[0043] (4) The mass ratio of the metal salt in the metal salt solution to the porous graphite particles is (0.5-5):100.

[0044] In some embodiments of the present application, the graphite particles and the ligand solution are mixed under heating conditions, the heating temperature is 50° C. to 120° C., and the heating time is 2 h to 72 h.

[0045] In some embodiments of the present application, the preparation method satisfies at least one of the following characteristics:

[0046] (1) The porous graphite particles and the metal salt solution are mixed for 0.5 h to 2 h;

[0047] (2) The reducing atmosphere includes at least one of nitrogen and argon and hydrogen;

[0048] (3) The heat treatment temperature is 400°C to 1000°C, and the time is 2h to 24h;

[0049] (4) The heating rate to the heat treatment temperature is 1°C / min to 10°C / min.

[0050] In some embodiments of the present application, the preparation method satisfies at least one of the following characteristics:

[0051] (1) The volume proportion of hydrogen in the reducing atmosphere is 3.0% to 10.0%;

[0052] (2) The heat treatment temperature is 700°C to 800°C, and the time is 2h to 5h;

[0053] (3) The heating rate to the heat treatment temperature is 2.0°C / min to 5.0°C / min.

[0054] The third aspect of the present application provides a negative electrode plate, comprising at least one of the negative electrode active material provided in the first aspect of the present application and the negative electrode active material prepared by the preparation method provided in the second aspect of the present application.

[0055] The fourth aspect of the present application provides a secondary battery, comprising the negative electrode sheet provided in the third aspect of the present application.

[0056] The fifth aspect of the present application provides an electrical device, comprising at least one of the negative electrode active material provided in the first aspect of the present application, the negative electrode active material prepared by the preparation method provided in the second aspect of the present application, the negative electrode plate provided in the third aspect of the present application, and the secondary battery provided in the fourth aspect of the present application.

[0057] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0059] Figure 1 Schematic diagram of a secondary battery according to one embodiment of the present application.

[0060] Figure 2 yes Figure 1 FIG. 1 is an exploded view of a secondary battery according to an embodiment of the present application.

[0061] Figure 3 Schematic diagram of a battery module according to one embodiment of the present application.

[0062] Figure 4 Schematic diagram of a battery pack according to one embodiment of the present application.

[0063] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0064] Figure 6 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0065] Figure 7 This is a low-magnification SEM photograph of the negative electrode active material prepared in Example 1 of the present application.

[0066] Figure 8 This is a high-magnification SEM photograph of the negative electrode active material prepared in Example 1 of the present application.

[0067] Figure 9 This is a low-magnification SEM photograph of the negative electrode active material used in Comparative Example 1 of the present application.

[0068] Figure 10 These are dark field SEM and EDS mapping photos of the negative electrode active material prepared in Example 1 of the present application.

[0069] Figure 11 This is a Raman graph of the negative electrode active material prepared in Example 1 of the present application.

[0070] Figure 12 This is the XRD pattern of the negative electrode active material prepared in Example 1 of the present application.

[0071] Figure 13 1-3 and comparative examples 1-2 of the present application are tested for rate performance of button cells.

[0072] Description of reference numerals:

[0073] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Battery cell; 51. Housing; 52. Electrode assembly; 53. Cover; 6. Electrical device. DETAILED DESCRIPTION

[0074] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0075] " scope " disclosed in the present application can be 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 any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope 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 listed, and if the maximum range value 3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 merely an abbreviation for a combination of these values. 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. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0076] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0077] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0078] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0079] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. 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 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 steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0080] In this application, open technical features or technical solutions described with words such as "contain," "include," and "includes" do not exclude additional members beyond the listed members unless otherwise specified, and can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include other members unless otherwise specified. This can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" and the feature or solution of "A includes not only a1, a2, and a3, but also other members."

[0081] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0082] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0083] One embodiment of the present application provides a negative electrode active material, comprising porous graphite particles and metal single atoms disposed on the porous graphite particles.

[0084] Taking lithium-ion batteries as an example, the commonly used negative electrode active materials are graphite materials. When lithium-ion batteries are charged at high rates, the lithium insertion rate of graphite materials is lower than that of Li + The transfer rate in the electrolyte leads to the generation of Li on the negative electrode surface. + The accumulation of negative electrode leads to the polarization of the negative electrode, which makes the lithium-ion battery have the risk of lithium plating. + Embedding path, increase Li+ embedding channel and reducing Li + The embedding energy barrier helps to improve the high-rate charging capability of graphite materials.

[0085] Taking lithium-ion batteries as an example, without wishing to be bound by any theory, the negative electrode active material of the present application comprises porous graphite particles and metal single atoms disposed on the porous graphite particles, which is a porous graphite material modified with metal single atoms. + The embedding channel can also shorten the Li + The embedding path of Li + Moreover, the metal atoms on the porous graphite particles can improve the local charge distribution on the surface of the porous graphite particles and reduce the Li + The embedding energy barrier on the graphite surface accelerates the Li + The above-mentioned negative electrode active materials synergistically improve the Li + The transport dynamics on the surface of the negative electrode active material reduces the negative electrode polarization, improves the kinetic performance of the negative electrode, and thus improves the high-rate charging capability of the secondary battery.

[0086] It is understood that the secondary battery of the present application includes but is not limited to lithium ion batteries, for example, it may also include sodium ion batteries, and the corresponding active ions mentioned above are in addition to Li + , or Na + .

[0087] It should be noted that a single metal atom refers to a metal existing in the form of a single atom. A single atom is different from a single metal; in a single metal, the metal atoms are interconnected by metallic bonds, while adjacent sites of a single atom are not considered to have metallic bonds connecting them.

[0088] One embodiment of the present application provides a method for preparing the above-mentioned negative electrode active material, which may include the following steps S10 to S20:

[0089] S10, mixing the graphite particles with the alkaline ligand solution, and drying to obtain porous graphite particles.

[0090] S20, mixing the porous graphite particles with the metal salt solution, drying the mixture, and then heat-treating the mixture in a reducing atmosphere to obtain a negative electrode active material, wherein the metal ions in the metal salt solution can form a complex with the ligand.

[0091] Furthermore, the alkaline ligand solution is an aqueous solution. The alkaline ligand solution can utilize the abundant OH -The ligand reacts with defect sites on the graphite surface, etching the graphite particles and transforming them into porous graphite particles. The ligand adheres to the graphite particle surface and, in subsequent steps, forms a complex with the metal ions, thereby anchoring the metal atoms to the porous graphite particles. Furthermore, the ligand has at least multiple coordinating groups.

[0092] Furthermore, the alkaline ligand solution includes a first organic amine compound, wherein the functionality of the organic amine group in the first organic amine compound is greater than 1, and the first organic amine compound is a basic compound. It can be understood that the organic amine group is the ligand group of the first organic amine compound.

[0093] It can be understood that the first organic amine compound is hydrolyzed in aqueous solution to produce abundant OH - Therefore, it is alkaline. In other words, the organic amine aqueous solution is alkaline. This innovative use of the rich OH in the first organic amine compound aqueous solution - It reacts with defect sites on the graphite surface to etch the graphite particles, thereby forming porous graphite particles. At the same time, the first organic amine compound molecules have a strong interaction with the oxygen-containing functional groups on the surface of the graphite particles through the organic amine groups, and the functionality of the organic amine groups in the first organic amine compound is greater than 1, which can achieve the "grafting" of the organic amine groups on the graphite particles, so that the surface of the porous graphite particles is connected with free organic amine groups.

[0094] The abundant organic amine groups on the porous graphite particles have strong coordination ability. By mixing the porous graphite particles with a metal salt solution, the organic amine groups can coordinate with the empty orbitals of the metal cations to form a metal complex, thereby realizing the coordination anchoring of the metal on the porous graphite particles. Then, heat treatment is carried out in a reducing atmosphere to reduce the metal salt at the anchoring site to form a metal single atom.

[0095] As mentioned above, in the present application, the first organic amine compound has at least the following two functions: one is to etch the graphite particles to form porous graphite particles in step S10; the other is to coordinate and anchor to guide the formation of metal single atoms in step S20.

[0096] Another embodiment of the present application provides a method for preparing the above-mentioned negative electrode active material, which may include the following step S30:

[0097] The graphite particles are mixed with an alkaline ligand solution and a metal salt solution, dried, and then heat-treated in a reducing atmosphere to obtain a negative electrode active material. Furthermore, the ligand is in excess relative to the metal salt solution.

[0098] This preparation method mixes an alkaline ligand solution and a metal salt solution with graphite particles at the same time. The coordination between the metal cobalt ions and the ligands and the etching of the graphite particles by the alkaline ligand solution are carried out simultaneously, and the metal ions can also be anchored on the graphite surface, and finally graphite with single atomic sites on the surface is obtained, that is, the above-mentioned negative electrode active material is obtained. However, compared with the aforementioned step-by-step preparation method, its etching sites are limited, so the content of single atoms formed is low. Without wishing to be limited to any theory, the preparation method of the above-mentioned negative electrode active material of the present application provides a ligand etching-coordination anchoring strategy using organic amines, etc., and the prepared negative electrode active material is modified graphite, that is, a porous graphite material modified with metal single atoms. This negative electrode active material can be used in secondary batteries, which can improve Li + The transport dynamics of active ions on the surface of the negative electrode active material can reduce the polarization of the negative electrode, improve the kinetic performance of the negative electrode, and thus improve the high-rate charging capacity of the secondary battery.

[0099] In some embodiments of the present application, the surface of the crystal material of the porous graphite particles has a basal plane and an end face connected to the basal plane, the end face is a porous structure, and the end face is provided with the above-mentioned metal single atom. Since the surface of the crystal material of the graphite particles has a basal plane and an end face connected to the basal plane, and the basal plane of the graphite particles is a complete six-membered ring structure, and the end face contains more abundant oxygen-containing functional groups, the OH in the solution during the preparation process is - They can preferentially react with defect sites on the end faces of graphite particles. Therefore, after treatment with the ligand solution in step S10, graphite particles with porous end faces can be obtained. Furthermore, ligand molecules such as the first organic amine compound strongly interact with oxygen-containing functional groups on the end faces, enabling preferential "grafting" of ligand groups such as organic amine groups onto the end faces. As a result, the metal atoms are preferentially formed on the end faces of the porous graphite particles.

[0100] It is understood that in some embodiments, after being treated with the ligand solution, the basal surface of the porous graphite particles will also form a porous structure. Accordingly, the basal surface of the porous graphite particles will also be formed with the metal atoms.

[0101] In some embodiments of the present application, the specific surface area of ​​the negative electrode active material is 1.2 m 2 ·g -1 ~5.0 m 2 ·g -1 , for example, 1.2 m 2 ·g -1 , 1.5 m 2 ·g -1 , 2 m 2 ·g -1 , 2.5 m 2 ·g -1 , 3 m 2 ·g-1 , 3.5m 2 ·g -1 , 4 m 2 ·g -1 , 4.5m 2 ·g -1 , 5 m 2 ·g -1 ; further can be 1.2 m 2 ·g -1 ~2.5 m 2 ·g -1 .

[0102] The specific test steps for the specific surface area test method are as follows: 1. Pretreatment: Place an appropriate amount of sample in a dedicated sample tube, heat and vacuum degas for 2 hours, and weigh the total weight after cooling to room temperature. Subtract the mass of the sample tube to obtain the sample mass. 2. Testing: Place the sample tube in the workstation and, at a constant low temperature, measure the amount of gas adsorbed on the solid surface under adsorption pressure. Based on the BET multilayer adsorption theory and its formula, the monolayer adsorption amount of the sample is calculated, thereby calculating the specific surface area per unit mass of the solid sample. 3. Adsorbed gas: carbon dioxide, adsorption pressure points: 0.005, 0.010, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.050, test atmosphere: ice-water mixture.

[0103] In some embodiments of the present application, the porous graphite particles have a Dv50 particle size of 5 μm to 50 μm. For example, the Dv50 particle size of the porous graphite particles can be 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

[0104] Dv50 is well known in the art and can be measured using methods known in the art. For example, it can be measured using a laser particle size analyzer (e.g., Malvern Master Size 3000). Dv50 represents the particle size at which the cumulative volume percentage of particles, starting from the smallest particle size, reaches 50%, based on the particle size volume distribution.

[0105] Particle size and volume distribution can be determined by the following method: Add an appropriate amount of the sample to be tested to a clean beaker and thoroughly sonicate to ensure complete dispersion. The test instrument is a Malvern 2000 (USA). The sample is poured into the injection tower and then circulated with the solution into the test optical system. The particles are illuminated by a laser beam, and the energy distribution of the scattered light is measured to determine the particle size distribution (shading degree: 8-12%). A particle size and volume distribution graph is then plotted based on the test data.

[0106] In some embodiments of the present application, the porous graphite particles include at least one of artificial graphite and natural graphite. Accordingly, the graphite particles in the preparation method include at least one of artificial graphite and natural graphite. The morphology of the porous graphite particles includes, but is not limited to, at least one of flake graphite, granular graphite, and spherical graphite. For example, the porous graphite particles may be at least one of natural flake graphite, natural granular graphite, and artificial spherical graphite.

[0107] In some embodiments of the present application, the mass content of metal atoms in the negative electrode active material is 0.01 wt% to 0.5 wt%, further 0.1 wt% to 0.5 wt%, and 0.2 wt% to 0.5 wt%. When the mass content of metal atoms is controlled within this range, the structural stability of the graphite particle phase of the resulting negative electrode active material is substantially unaffected, and its degree of graphitization is controlled within a relatively high range. A higher degree of graphitization also helps improve rate performance and reduces the occurrence of surface side reactions, thereby effectively enhancing the kinetic performance of the negative electrode.

[0108] As an example, in the negative electrode active material, the mass content of metal single atoms can be 0.01wt%, 0.015wt%, 0.02wt%, 0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%; in some embodiments, it can also be a range consisting of any two of the above point values ​​as end values, and the same is true below.

[0109] In some embodiments of the present application, the degree of graphitization of the negative electrode active material is 90% to 97%.

[0110] In some embodiments of the present application, the type of metal single atom includes at least one of a transition metal and an alkaline earth metal. Further, the type of metal single atom includes one or more of Fe, Co, Ni, Cu, Zn, Mn, Mg and Sc. It is understood that by controlling the type of metal salt, the single atom site modification of a metal can be achieved, and the single atoms of multiple metals can be anchored on the surface of the graphite particles, such as the end faces of the graphite particles. Optionally, the type of metal single atom includes one or more of Fe, Co, Ni, Cu, Zn, Mn, Mg and Sc.

[0111] In some embodiments of the present application, the negative electrode active material further comprises at least one of nitrogen and amorphous carbon doped on the surface of the porous graphite particles. The heat treatment in a reducing atmosphere is equivalent to thermal reduction and high-temperature calcination, whereby the metal salt is reduced at the anchoring sites to form metal single atoms while the organic amine groups are thermally reduced and carbonized at high temperature, thereby forming nitrogen and amorphous carbon doped on the surface of the porous graphite particles.

[0112] In some embodiments of the present application, in the above preparation method, the organic group in the first organic amine compound includes a primary amine group. The primary amine group has strong coordination ability and less steric hindrance, and can better coordinate with the metal ion.

[0113] It is understood that the functionality of the organic amine group in the first organic amine compound is greater than 1, i.e., it may be multiple. It is understood that functionality refers to the number of organic amine groups contained in one molecule of the organic amine compound. The presence of multiple organic amine groups in the organic amine compound can enhance its coordination and anchoring capabilities. In some embodiments of the present application, the functionality of the organic amine group in the organic amine compound is ≥ 2, i.e., it is an organic polyamine compound, for example, with a functionality of 2 to 5, for example, 2, 3, 4, or 5.

[0114] In some embodiments, the alkaline ligand solution may further include a second organic amine compound, wherein the organic amine group in the second organic amine compound has a functionality of 1. Although the second organic amine compound does not coordinate and anchor the metal atoms on the porous graphite particles, it can help regulate the pH of the ligand solution.

[0115] It is understood that the second organic amine compound may also be omitted.

[0116] In some embodiments of the present application, in steps S10 and S30 of the preparation method, the pH value of the alkaline ligand solution is 8.0-14.0, further 10.0-14.0, and even further 11.0-14.0. For example, the pH value of the alkaline ligand solution can be 8, 9, 10, 11, 12, 13, or 14. The pH value of the alkaline ligand solution can be controlled by controlling the concentration of the alkaline ligand solution. By controlling the pH value of the alkaline ligand solution, the degree of etching of the graphite particles by the alkaline ligand solution can be controlled, thereby adjusting the pore size and specific surface area of ​​the porous graphite particles.

[0117] In some embodiments of the present application, the first organic amine compound and the second organic amine compound are each independently an organic amine small molecule, and the molar mass of the organic amine small molecule is less than or equal to 1000 g / mol, further less than or equal to 500 g / mol, and further less than or equal to 200 g / mol.

[0118] Furthermore, the organic primary amine compound is a small molecule organic amine having a molar mass less than or equal to 1000 g / mol. As an example, the molar mass of the organic primary amine compound is less than or equal to 500 g / mol, and may further be less than or equal to 200 g / mol.

[0119] Furthermore, the organic amine groups in the first organic amine compound and the second organic amine compound each independently include a primary amine group. Furthermore, the functionality of the primary amine group in the first organic amine compound is 2 to 5, and the functionality of the primary amine group in the second organic amine compound is 1.

[0120] Furthermore, the first organic amine compound and the second organic amine compound each independently have 1 to 10 carbon atoms.

[0121] Further, the first organic amine compound includes ethylenediamine.

[0122] Furthermore, the second organic amine compound includes at least one of methylamine and ethylamine.

[0123] In some embodiments of the present application, in step S10 and step S30 of the preparation method, the graphite particles and the ligand solution are mixed under heating conditions, and the heating temperature is 50°C to 120°C, and the heating time is 2 hours to 72 hours. As an example, the heating temperature can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C; as an example, the heating time can be 2 hours, 5 hours, 10 hours, 12 hours, 15 hours, 20 hours, 24 hours, 30 hours, 40 hours, 48 ​​hours, 50 hours, 60 hours, 65 hours, 70 hours, or 72 hours.

[0124] Optionally, the heating temperature in step S10 and step S30 is 80° C. to 100° C., and the heating time is 12 h to 24 h.

[0125] In some embodiments of the present application, in steps S10, S20, and S30 of the preparation method described above, after mixing, solid-liquid separation can be performed by filtration or other methods, and the solid phase can be dried. Furthermore, the drying temperature can be 60° C. to 100° C., and the drying time can be 2 hours to 10 hours.

[0126] In some embodiments of the present application, in step S20 and step S30 of the above preparation method, the metal elements in the metal salt solution include one or more of Fe, Co, Ni, Cu, Zn, Mn, Mg and Sc.

[0127] In some embodiments of the present application, the metal salt in the metal salt solution includes one or more of hydrochloride, nitrate and sulfate.

[0128] The metal ions in the metal salt are in excess. Even with the coordination of the ligands, it is difficult to convert all of them into single atoms and modify them on the end faces of the porous graphite particles. The number of single-atom sites on the end faces of porous graphite is mainly determined by the number of defect sites on the end faces of porous graphite.

[0129] In some embodiments of the present application, the concentration of the metal salt solution is 0.001 mol·L -1 ~1mol·L -1 , as an example, it can be 0.001 mol·L -1 , 0.01 mol·L -1 , 0.1 mol·L -1 , 0.2 mol·L -1 , 0.5 mol·L -1 , 0.8 mol·L -1 , 1 mol·L -1 , which can be further increased to 0.1 mol·L -1 ~1mol·L -1 , further to 0.2 mol·L -1 ~1mol·L -1 .

[0130] In some embodiments of the present application, the mass ratio of the metal salt to the porous graphite particles in the metal salt solution is (0.5-5):100. As an example, the mass ratio can be 0.5:100, 1:100, 1.5:100, 1.8:100, 2:100, 3:100, 4:100, or 5:100.

[0131] In some embodiments of the present application, in step S20 of the preparation method, the porous graphite particles and the metal salt solution are mixed for 0.5 h to 2 h, and the mixing temperature can be room temperature.

[0132] In some embodiments of the present application, in step S20 of the preparation method, the reducing atmosphere includes at least one of nitrogen and argon, and hydrogen. Furthermore, the volume fraction of hydrogen in the reducing atmosphere is 3.0% to 10.0%. Alternatively, the reducing atmosphere can be a mixture of hydrogen and argon.

[0133] In some embodiments of the present application, in step S20 of the preparation method, the heat treatment temperature is 400°C to 1000°C, the time is 2 hours to 24 hours, and the heating rate to the heat treatment temperature is 1°C / min to 10°C / min.

[0134] As an example, in step S20 of the preparation method, the heat treatment temperature may be 400°C, 500°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, or 1000°C; and the heat treatment time may be 2 hours, 5 hours, 10 hours, 12 hours, 15 hours, 20 hours, or 24 hours. As an example, the heating rate may be 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min.

[0135] Optionally, the heating rate is 2.0°C / min~5.0°C / min; optionally, the heat treatment temperature is 600°C~1000°C, further 700°C~800°C; optionally, the heat treatment time is 2h~10h, further 2h~5h.

[0136] Furthermore, according to the type of metal salt, the volume ratio of hydrogen in the reducing atmosphere and the temperature of the heat treatment and other parameters can be adjusted to reduce different types of metal ions to form metal single atoms, thereby achieving the modification of different types of metal single atoms.

[0137] Another embodiment of the present application provides a negative electrode plate, comprising at least one of the above-mentioned negative electrode active material and the negative electrode active material prepared by the above-mentioned preparation method.

[0138] Another embodiment of the present application provides a secondary battery comprising at least one of the above-mentioned negative electrode active material, the negative electrode active material prepared by the above-mentioned preparation method, and the above-mentioned negative electrode plate.

[0139] Another embodiment of the present application provides an electrical device comprising at least one of the above-mentioned negative electrode active material, the negative electrode active material prepared by the above-mentioned preparation method, the above-mentioned negative electrode plate, and the above-mentioned secondary battery.

[0140] The secondary battery and the electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0141] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0142] Negative electrode

[0143] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector. The negative electrode film layer includes the above-mentioned negative electrode active material, that is, the above-mentioned modified graphite, specifically a porous graphite material modified with metal single atoms.

[0144] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0145] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be obtained by forming a metal material on a polymer substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer substrate in the negative electrode current collector may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0146] In some embodiments, the negative electrode active material in the negative electrode film layer is only the modified graphite mentioned above. In some embodiments, in addition to the negative electrode active material mentioned above, the negative electrode film layer may also include other negative electrode active materials, such as negative electrode active materials for batteries known in the art. As non-limiting examples, the negative electrode active material may include one or more of the following materials: unmodified artificial graphite, unmodified natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used.

[0147] In some embodiments, the negative electrode film layer may further include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0148] In some embodiments, the negative electrode film layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0149] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose, CMC-Na).

[0150] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt%~60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000~10000mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75~220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~1.8 g / cm 3 .

[0151] Positive electrode

[0152] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0153] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0154] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. Non-limiting examples of the polymer material substrate in the positive electrode current collector may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0155] In some embodiments, the positive electrode active material may be a battery positive electrode active material known in the art. As non-limiting examples, the positive electrode active material may include one or more of the following materials: olivine-structured lithium-containing phosphates, lithium metal oxides, and their respective modified compounds. However, this application is not limited to these materials; other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination. Examples of lithium metal oxides include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of olivine-structured lithium-containing phosphates include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0156] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0157] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0158] In some embodiments, a positive electrode sheet can be prepared by dispersing the components for preparing the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one surface of a positive electrode current collector; and performing drying, cold pressing, and other processes to obtain a positive electrode sheet. The solvent can be selected from, but is not limited to, any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The positive electrode slurry can be coated on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The positive electrode slurry can be coated on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s. When coating the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15 mg / cm 2 ~35mg / cm 2 The compaction density of the positive electrode can be 3.0g / cm 3 ~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0159] electrolytes

[0160] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0161] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0162] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorobis(oxalatophosphate) (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0163] In some embodiments, the solvent may include one or more of 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, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0164] 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, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0165] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0166] Isolation film

[0167] In some embodiments, the secondary battery further includes a separator.

[0168] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0169] 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.

[0170] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0171] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may be 12 μm to 20 μm.

[0172] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0173] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0174] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0175] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 1 The secondary battery shown is a single battery cell, which is an example of a battery cell having an exemplary square structure.

[0176] In some embodiments, the secondary battery may include an outer packaging. The outer packaging may be used to encapsulate the electrode assembly and electrolyte. In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a pouch-type soft package. The material of the soft package may be plastic. Further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0177] In some of these embodiments, reference Figure 2The outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0178] In some embodiments, the secondary battery may be a battery module or a battery pack. A battery module includes at least one battery cell. A battery module may contain one or more battery cells, and those skilled in the art may select an appropriate number based on the application and capacity of the battery module.

[0179] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of battery cells 5 may further be fixed by fasteners.

[0180] 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.

[0181] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0182] Figure 4 and Figure 5 The battery pack 1 is used as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0183] In addition, one embodiment of the present application further provides an electrical device, comprising the aforementioned secondary battery provided herein. The secondary battery can serve as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, and the like. Examples of mobile devices include, but are not limited to, mobile phones and laptop computers; examples of electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks.

[0184] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0185] Figure 6 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0186] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0187] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0188] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0189] Example 1

[0190] (1) Preparation of negative electrode active materials:

[0191] 1.1 Preparation of porous graphite materials:

[0192] 500 mL of ethylenediamine was added to 5 L of deionized water (the pH value of the resulting ethylenediamine aqueous solution was 12.36 according to a pH meter) and stirred for 5 minutes. Subsequently, 1 kg of commercial graphite (artificial spherical graphite, Dv50 particle size of 14.5 μm) was added and stirred, and the system temperature was controlled at 100°C. After stirring for 24 hours, the mixture was filtered, washed once with deionized water, and the solid was dried to obtain a porous graphite material.

[0193] 1.2 End-face single-atom modified porous graphite materials:

[0194] 0.2 mol·L -1 A 500 mL aqueous solution of cobalt nitrate was added to 5 L of deionized water and stirred for 5 minutes. Then, 1 kg of the porous graphite material prepared in the above steps was added and stirred for 2 hours. The mixture was filtered, rinsed once with deionized water, and dried. Finally, the porous graphite impregnated with cobalt metal cations was placed in a high-temperature furnace and introduced with a hydrogen-argon mixture with a 5% hydrogen concentration by volume. The temperature was raised at a controlled rate of 2.0°C / min and the heat treatment temperature was set at 700°C for 2 hours for thermal reduction and high-temperature calcination. After the heat treatment was completed and the temperature was naturally cooled, a porous graphite material with end-face cobalt single atoms modified was obtained, which served as the negative electrode active material.

[0195] (2) Preparation of negative electrode sheet:

[0196] 92.0 g of the porous graphite material modified with single cobalt atoms obtained in step (1), 2.0 g of a conductive agent (0.5 g of carbon nanotubes, 1.5 g of acetylene black), and 6.0 g of a binder (PVDF) were added to a certain amount of NMP and mixed under the action of a vacuum mixer to obtain a negative electrode slurry; the negative electrode slurry was evenly coated on a single surface of a copper foil; the copper foil was dried at room temperature and then transferred to a 120°C oven for drying for 1 h, and then super-cold pressed and cut to obtain a negative electrode sheet, wherein the coating amount per unit area of ​​a single side was 0.17 g / 1540.25 mm 2 .

[0197] (3) Preparation of half-cell: The performance of the negative electrode is examined by preparing a half-cell.

[0198] The negative electrode prepared in step (2) was assembled into a button cell with the Li sheet (counter electrode), a separator (a 12 μm thick polypropylene separator) and an electrolyte (the concentration of lithium salt LiPF6 was 1 mol / L, and the solvents were EC, EMC and DEC in a volume ratio of 20:20:60).

[0199] Example 2

[0200] The method is basically the same as Example 1, except that the aqueous cobalt nitrate solution in the preparation of the negative electrode active material in (1) Example 1 is replaced by an aqueous ferric chloride solution of the same molar concentration, and other conditions remain unchanged. A porous graphite material modified with single iron atoms on the end faces is obtained, and a button battery is obtained. The battery process and test process remain unchanged.

[0201] Example 3

[0202] The method is basically the same as Example 1, except that the aqueous cobalt nitrate solution in the preparation of the negative electrode active material in (1) Example 1 is replaced by an aqueous copper chloride solution of the same molar concentration, and other conditions remain unchanged. A porous graphite material modified with single copper atoms on the end surface is obtained, and a button battery is obtained. The battery process and test process remain unchanged.

[0203] Example 4

[0204] The method is basically the same as Example 1, except that the aqueous cobalt nitrate solution in the preparation of the negative electrode active material in (1) Example 1 is replaced by an aqueous nickel chloride solution of the same molar concentration, and other conditions remain unchanged. A porous graphite material modified with single nickel atoms on the end faces is obtained, and a button battery is obtained. The battery process and test process remain unchanged.

[0205] Examples 5 to 8

[0206] The method is basically the same as Example 1, except that the aqueous cobalt nitrate solution in the preparation of the negative electrode active material in (1) Example 1 is replaced by the aqueous metal salt solution in Table 1 with the same molar concentration, and other conditions remain unchanged. The corresponding porous graphite material modified with metal single atoms on the end surface is prepared, and a button battery is obtained. The battery process and test process remain unchanged.

[0207] Example 9

[0208] The method is basically the same as Example 1, except that the amount of ethylenediamine used in the preparation of (1) the negative electrode active material is increased, so that the pH value of the ethylenediamine aqueous solution is higher, as shown in Table 1.

[0209] Example 10

[0210] The method is basically the same as Example 9, except that the molar concentration of the cobalt nitrate aqueous solution in the preparation of the negative electrode active material in (1) Example 1 is changed, as shown in Table 1. Other conditions remain unchanged, and the corresponding porous graphite material modified with single cobalt metal atoms on the end faces is obtained, and button batteries are obtained. The battery process and test process remain unchanged.

[0211] Examples 11-12

[0212] The method is basically the same as Example 1, except that the molar concentration of the cobalt nitrate aqueous solution and the amount of ethylenediamine used in the preparation of the negative electrode active material in Example 1 (1) are changed to adjust the pH value of the ethylenediamine aqueous solution, as shown in Table 1. Other conditions remain unchanged, and the corresponding porous graphite material modified with single cobalt metal atoms on the end faces is obtained, and button batteries are obtained. The battery process and test process remain unchanged.

[0213] Example 13

[0214] The method is essentially the same as Example 1, except that the heat treatment temperature in step 1.2 of (1) is changed to 800°C and the heat treatment time is changed to 5 hours. After the heat treatment is completed and the temperature is naturally cooled, a porous graphite material with end-face cobalt single atoms modified thereon is obtained, i.e., the negative electrode active material.

[0215] Example 14

[0216] The method is basically the same as Example 1, except that the heat treatment temperature in step 1.2 of (1) is changed to 900°C and the heat treatment time is changed to 2.0 h. After the heat treatment is completed and the temperature is naturally cooled, a porous graphite material with end-face cobalt single atoms modified can be obtained, i.e., the negative electrode active material.

[0217] Example 15

[0218] The method is essentially the same as Example 4, except that the temperature for heat treatment of the porous graphite material modified with single cobalt atoms at the end faces in step 1.2 of (1) is changed to 400°C and the heat treatment time is changed to 24 hours. After the heat treatment is completed and the temperature is naturally cooled, a porous graphite material modified with single cobalt atoms at the end faces is obtained, i.e., the negative electrode active material.

[0219] Example 16

[0220] The process is essentially the same as Example 1, except that the preparation process of the negative electrode active material is different. Specifically, the ethylenediamine solution and the cobalt nitrate aqueous solution are simultaneously mixed with commercial graphite (artificial spherical graphite). The specific steps are as follows:

[0221] (1) Preparation of negative electrode active materials:

[0222] 500 mL of ethylenediamine solution was added to 5 L of deionized water (pH value of ethylenediamine solution was 12.36) and stirred for 5 min; then, 0.2 mol·L -1A cobalt nitrate aqueous solution (500 mL) and 1 kg of commercial graphite (artificial spherical graphite) were stirred at 100°C for 24 hours, filtered, rinsed once with deionized water, and dried. Finally, the dried graphite was placed in a high-temperature furnace and introduced into a hydrogen-argon mixture with a 5% hydrogen concentration by volume. The temperature was raised at a controlled rate of 2.0°C / min and the heat treatment temperature was set at 700°C for 2 hours for thermal reduction and high-temperature calcination. After the heat treatment was completed and the temperature was allowed to cool naturally, the modified graphite material, the negative electrode active material, was obtained.

[0223] Comparative Example 1

[0224] The commercial graphite in Example 1 was directly prepared into button batteries, and the battery process and testing process remained unchanged.

[0225] Comparative Example 2

[0226] The process is essentially the same as Example 1, except that the step of impregnating the cobalt metal cation in the preparation of the negative electrode active material (1) is omitted. Instead, the porous graphite material obtained in step 1.1 of Example 1 is directly placed in a high-temperature furnace, and a hydrogen-argon mixture with a hydrogen volume concentration of 5% is introduced. The heating rate is controlled at 2.0°C / min, the calcination temperature is 700°C, and the calcination time is 2.0 h to obtain the final porous graphite material. The porous graphite is prepared into button-type batteries, and the battery process and testing procedures remain unchanged.

[0227] Comparative Example 3

[0228] The method is basically the same as Example 1, except that the preparation process of the negative electrode active material is different. Specifically, sodium hydroxide solution is used instead of ethylenediamine solution in step 1.1, and specifically, hydroxide solution of the same volume and the same pH value is used.

[0229] The following is a performance test.

[0230] (1) Scanning electron microscope test.

[0231] The negative electrode active material prepared in Example 1 and the negative electrode active material used in Comparative Example 1 were tested by scanning electron microscopy to obtain Figures 7 to 10 .

[0232] in, Figure 7 and Figure 8 The following are low-magnification SEM and high-magnification SEM photos of the negative electrode active material prepared in Example 1 of the present application, respectively. It can be seen that the microstructure of the end surface of the porous graphite material in Example 1 is looser, indicating that after the treatment with the organic amine solution, corresponding etching holes are generated on the end surface, forming a porous structure on the end surface.

[0233] Figure 9This is a low-magnification SEM photograph of the negative electrode active material used in Comparative Example 1 of the present application. It can be seen from the photograph that the microstructure of the graphite end face is relatively dense.

[0234] Figure 10 The following are dark-field SEM and EDS mapping images (EDS distribution diagram) of the negative electrode active material prepared in Example 1 of the present application. The EDS mapping images show that Co tends to be distributed on the end faces of graphite, with a small amount also distributed on the basal surface, but the distribution on the end faces is more dense and concentrated. This is because the end faces of graphite contain more oxygen-containing functional groups than the basal surface, resulting in stronger van der Waals interactions with organic amines, leading to preferential adsorption of organic amine groups on the end faces of graphite. These organic amine groups adsorbed on the end faces of graphite have strong coordination with metal cations, forming nitrogen-metal coordination bonds to anchor the metal ions. Subsequent heat treatment in a reducing atmosphere reduces the metal ions to metal atoms.

[0235] (2) Raman spectroscopy test and XRD test.

[0236] The negative electrode active material prepared in Example 1 of the present application was subjected to Raman spectroscopy testing, and the results were as follows: Figure 11 shown.

[0237] From this, we can see that at ~1580cm -1 The G peak at 1380 cm -1 The intensity of the D peak at 690 cm indicates that the porous graphite modified with single cobalt atoms on the end faces has a high degree of graphitization. -1 At the location around, Figure 11 There is no peak at this position, indicating that there is no Co—O bond.

[0238] The negative electrode active material prepared in Example 1 of the present application was subjected to XRD testing, and the results were as follows: Figure 12 As shown in the figure, the XRD pattern only has the characteristic peaks of graphite, and no diffraction peaks of Co element (Co-Co metal bond) are observed.

[0239] from Figure 11 and Figure 12 It can be seen that there is no Co—Co bond and Co—O bond in the negative electrode active material prepared in Example 1; Figure 10 It can be seen that the Co element on the surface of the graphite material should be a separate atomic site, and there is no metallic bond between the atomic sites.

[0240] (3) Detection of the content of metal elements in negative electrode active materials.

[0241] The metal element content is measured using inductively coupled plasma optical emission spectrometry (ICP). The specific steps involve adding the negative electrode active material to a concentrated nitric acid solution, performing microwave digestion, and then removing the solution and measuring the plasma optical emission spectrum. By comparing the spectral line intensity with a standard spectrum, the corresponding metal element content, i.e., the content of metal single-atom sites, is determined. The test results are shown in the table below.

[0242] (4) Graphitization degree test of negative electrode active materials.

[0243] Method for measuring the degree of graphitization of negative electrode active materials:

[0244] 1. Pretreatment: Add silicon powder; weigh according to the ratio of negative electrode active material: silicon powder 5:1, put it in a clean mortar and grind it for 50 minutes to ensure uniform mixing.

[0245] 2. Sample preparation: Powder, sample preparation method using a flat plate sample trough with a depth of 0.5 mm and a diameter of 25 mm.

[0246] 3. Test: Starting angle 52°, ending angle 58°, step length 0.00836°, each step duration 0.3s.

[0247] 4. Fixed core parameters: voltage: 40 kV, current: 40 mA, anti-scatter slit: 1 mm, 2Theta angle: 52-58°, scan rate: 1° / min. The degree of graphitization was quantified based on the intensity of the graphite diffraction peak around 54°. The test results are shown in the table below.

[0248] (5) Rate performance test.

[0249] The button-type batteries prepared in each embodiment and each comparative example were subjected to multiple charge and discharge rate tests in sequence using the LAND test system. The specific test steps are as follows:

[0250] The first stage: After standing for 5 minutes, discharge at a constant current of 0.05C to 0.005 V; after standing for 5 minutes, discharge at a constant current of 0.002mA to 0.005V; after standing for 5 minutes, charge at a constant current of 0.1C to 2.00 V, and repeat twice.

[0251] The second stage: let it stand for 5 minutes, then discharge it at a constant current of 0.1C to 0.005 V; after standing for 5 minutes, charge it at a constant current of 0.1C to 2.00 V, and repeat five times.

[0252] The third stage: let it stand for 5 minutes, then discharge it at a constant current of 0.33C to 0.005V; after standing for 5 minutes, charge it at a constant current of 0.33C to 2.00V, and repeat five times.

[0253] The fourth stage: let it stand for 5 minutes, then discharge it at a constant current of 0.5C to 0.005V; after standing for 5 minutes, charge it at a constant current of 0.5C to 2.00V, and repeat five times.

[0254] The fifth stage: let it stand for 5 minutes, then discharge the battery to 0.005V at a constant current of 1.0C; after standing for 5 minutes, charge the battery to 2.00V at a constant current of 1.0C, and repeat five times.

[0255] The sixth stage: let it stand for 5 minutes, then discharge the battery to 0.005V at a constant current of 2.0C; after standing for 5 minutes, charge the battery to 2.00V at a constant current of 2.0C, and repeat five times.

[0256] Stage 7: After standing for 5 minutes, discharge at a constant current of 4.0C to 0.005V; after standing for 5 minutes, charge at a constant current of 4.0C to 2.00V, and repeat five times.

[0257] The rate performance test results of the button batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 2 of the present application are shown in the figure. Figure 13 As shown. It can be seen that compared with Comparative Example 1, Comparative Example 2 obtains porous graphite by etching with an organic amine aqueous solution. Therefore, at higher discharge rates of 0.5C, 1C, and 2C, the specific capacity (i.e., gram capacity, unit mAh·g) of Comparative Example 2 is -1 ) is significantly better than the ordinary graphite in Comparative Example 1, indicating that the introduction of a porous structure can improve the fast charging performance of graphite; Examples 1 to 3 have significant advantages over Comparative Example 2 at a large discharge rate of 4C, indicating that the introduction of single atomic sites on the end face can significantly improve the high-rate charging capability of graphite.

[0258] Furthermore, after the end-face metal single atoms are introduced in Examples 1 to 3, the specific capacity of the end-face single-atom graphite is significantly improved compared with the porous graphite in Comparative Example 2 at higher discharge rates of 0.5C, 1C, and 2C, as well as at a high discharge rate of 4C, indicating that the single atoms on the end face of graphite can further enhance the fast charging capability of graphite.

[0259] Furthermore, the ratio of 1C gram capacity to 0.33C gram capacity of each embodiment and comparative example was obtained, which represents the ratio of 1C gram capacity utilization with the gram capacity utilization at 0.33C as the baseline, as shown in Table 2 as the rate performance parameter.

[0260] Some parameters and test results of the above embodiments and comparative examples are shown in Tables 1 and 2. The method for testing the specific surface area of ​​the negative electrode active material is as described above.

[0261] Table 1

[0262]

[0263] Table 2

[0264]

[0265] Comparative Example 1 uses commercial graphite; Comparative Example 2 uses porous graphite without cobalt loading; Comparative Example 3 uses sodium hydroxide etching to introduce sodium ions, and the graphite surface is alkaline. When a metal salt solution is subsequently added, metal cations easily form metal hydroxides on the surface of the graphite particles. After subsequent calcination, there may be metal oxide residues, or the hydroxides may agglomerate into metal oxide particles after calcination and decomposition. The metal ions in the metal oxide particles will dissolve during battery testing, thereby triggering side reactions, causing micro-short circuits inside the battery, and reducing battery performance. By comparing the embodiments with the comparative examples, it can be seen that the rate performance of each embodiment is better than that of the comparative example.

[0266] It should be noted that the graphitization degree of Example 2 is improved compared with that of Example 1 because the types of metal sites are different. It should be that the Fe sites catalyze graphite crystallization in the subsequent calcination process, thereby improving the overall crystallinity.

[0267] Compared with Example 1, the pH value of the ethylenediamine aqueous solution in Examples 9-10 is higher, the etching effect on graphite is higher, the specific surface area of ​​graphite is higher, there are more lithium ion channels inside the graphite, and the 1C rate performance is better.

[0268] Compared with Example 1, the pH value of the ethylenediamine aqueous solution in Examples 11~12 is smaller, the etching degree of graphite is lower, and the specific surface area after etching is lower. The metal salt is excessive in Examples 11~12, so as the specific surface area of ​​graphite decreases, the metal element content in Examples 11~12 also decreases, and thus the rate performance of 1C is reduced.

[0269] Compared with Example 1, the calcination temperature of Example 15 is lower, and the surface layer may not be completely carbonized, resulting in a lower specific surface area and the presence of a small amount of incompletely reduced metal. Therefore, it is easy to induce battery side reactions during battery operation, and the high-rate performance is reduced.

[0270] The preparation process of Example 16 is different. It uses ethylenediamine solution and cobalt nitrate aqueous solution to mix with commercial graphite at the same time. The metal cobalt ions are coordinated with ethylenediamine, but the ethylenediamine is excessive. The excess ethylenediamine can still etch graphite. Therefore, compared with Example 1, only a smaller amount of metal ions is anchored on the graphite surface, and the final graphite surface has a smaller number of single atomic sites.

[0271] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0272] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A negative electrode active material, characterized in that The invention comprises porous graphite particles and metal single atoms arranged on the porous graphite particles.

2. The negative electrode active material according to claim 1, wherein The surface of the crystal material of the porous graphite particles has a basal surface and an end surface connected to the basal surface, the end surface is a porous structure, and the metal single atom is provided on the end surface.

3. The negative electrode active material according to claim 2, wherein The base surface is also provided with the metal single atoms.

4. The negative electrode active material according to any one of claims 1 to 3, characterized in that The negative electrode active material satisfies at least one of the following conditions: (1) The specific surface area of ​​the negative electrode active material is 1.2 m 2 ·g -1 ~5.0 m 2 ·g -1 ; (2) The Dv50 particle size of the porous graphite particles is 5 μm to 50 μm; (3) The porous graphite particles include at least one of artificial graphite and natural graphite.

5. The negative electrode active material according to any one of claims 1 to 4, characterized in that The negative electrode active material satisfies at least one of the following conditions: (1) In the negative electrode active material, the mass content of the metal single atom is 0.01wt% to 0.5wt%; (2) The graphitization degree of the negative electrode active material is 90% to 97%.

6. The negative electrode active material according to any one of claims 1 to 5, characterized in that The metal single atom includes at least one of a transition metal and an alkaline earth metal.

7. The negative electrode active material according to claim 6, wherein The types of the metal single atoms include one or more of Fe, Co, Ni, Cu, Zn, Mn, Mg and Sc.

8. The negative electrode active material according to any one of claims 1 to 7, characterized in that The negative electrode active material further includes at least one of N element and amorphous carbon doped in the surface layer of the porous graphite particles.

9. A method for preparing a negative electrode active material, characterized in that: The steps include: The graphite particles are mixed with an alkaline ligand solution and then dried to obtain porous graphite particles; The porous graphite particles are mixed with a metal salt solution, dried, and then heat-treated in a reducing atmosphere to obtain the negative electrode active material; wherein the metal ions in the metal salt can form a complex with the ligand.

10. A method for preparing a negative electrode active material, characterized in that: The steps include: The graphite particles are mixed with an alkaline ligand solution and a metal salt solution, dried, and then heat-treated in a reducing atmosphere to obtain the negative electrode active material; wherein the metal ions in the metal salt can form a complex with the ligand.

11. The method for preparing a negative electrode active material according to claim 9 or 10, wherein: The alkaline ligand solution includes a first organic amine compound, the functionality of the organic amine group in the first organic amine compound is greater than 1, and the first organic amine compound is a basic compound.

12. The method for preparing the negative electrode active material according to claim 11, wherein: The alkaline ligand solution further includes a second organic amine compound, wherein the functionality of the organic amine group in the second organic amine compound is 1.

13. The method for preparing the negative electrode active material according to claim 12, wherein: The preparation method satisfies at least one of the following characteristics: (1) The pH value of the alkaline ligand solution is 8.0-14.0; (2) The functionality of the organic amine group in the first organic amine compound is 2 to 5; (3) The molar mass of the first organic amine compound is less than or equal to 1000 g / mol; (4) The molar mass of the second organic amine compound is less than or equal to 1000 g / mol.

14. The method for preparing a negative electrode active material according to claim 12 or 13, wherein: The preparation method satisfies at least one of the following characteristics: (1) the organic amine groups in the first organic amine compound and the second organic amine compound each independently include a primary amine group; (2) The molar mass of the first organic amine compound is less than or equal to 500 g / mol; (3) The molar mass of the second organic amine compound is less than or equal to 500 g / mol; (4) The first organic amine compound and the second organic amine compound have 1 to 10 carbon atoms.

15. The method for preparing a negative electrode active material according to any one of claims 12 to 14, characterized in that: The preparation method satisfies at least one of the following characteristics: (1) The first organic amine compound includes ethylenediamine; (2) The second organic amine compound includes at least one of methylamine and ethylamine.

16. The method for preparing a negative electrode active material according to any one of claims 9 to 15, wherein: The metal salt solution satisfies at least one of the following characteristics: (1) The metal element in the metal salt solution includes at least one of a transition metal and an alkaline earth metal; (2) The metal salt in the metal salt solution includes one or more of hydrochloride, nitrate and sulfate; (3) The concentration of the metal salt solution is 0.001 mol·L -1 ~1mol·L -1 ; (4) The mass ratio of the metal salt in the metal salt solution to the porous graphite particles is (0.5-5):

100.

17. The method for preparing a negative electrode active material according to any one of claims 9 to 16, wherein: The graphite particles and the ligand solution are mixed under heating conditions. The heating temperature is 50° C. to 120° C., and the heating time is 2 h to 72 h.

18. The method for preparing a negative electrode active material according to any one of claims 9 to 17, wherein: The preparation method satisfies at least one of the following characteristics: (1) The porous graphite particles and the metal salt solution are mixed for 0.5 h to 2 h; (2) The reducing atmosphere includes at least one of nitrogen and argon and hydrogen; (3) The heat treatment temperature is 400°C to 1000°C, and the time is 2h to 24h; (4) The heating rate to the heat treatment temperature is 1°C / min to 10°C / min.

19. The method for preparing the negative electrode active material according to claim 18, wherein: The preparation method satisfies at least one of the following characteristics: (1) The volume proportion of hydrogen in the reducing atmosphere is 3.0% to 10.0%; (2) The heat treatment temperature is 700°C to 800°C, and the time is 2h to 5h; (3) The heating rate to the heat treatment temperature is 2.0°C / min to 5.0°C / min.

20. A negative electrode plate, characterized in that: The invention comprises at least one of the negative electrode active material according to any one of claims 1 to 8 and the negative electrode active material prepared by the preparation method according to any one of claims 9 to 19.

21. A secondary battery, characterized in that: Including the negative electrode sheet according to claim 20.

22. An electrical device, characterized in that: The invention comprises at least one of the negative electrode active material according to any one of claims 1 to 8, the negative electrode active material prepared by the preparation method according to any one of claims 9 to 19, the negative electrode sheet according to claim 20, and the secondary battery according to claim 21.

Images