Negative active material, and method of preparation and use

Abstract

The application provides a kind of negative electrode active material and preparation method, negative electrode slurry, negative electrode sheet and preparation method, secondary battery and electric device. In the negative electrode active material, the surface of the negative electrode active substrate has amino group, and there is weak interaction between amino groups. The dispersion performance between the negative electrode active materials can be improved, so that the negative electrode active materials are not easy to appear agglomeration, and the uniformity of the distribution of the negative electrode active materials in the negative electrode sheet is improved.

Description

Technical Field

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

[0002] In recent years, rechargeable batteries have been widely used in portable electronic products, electric vehicles, and aerospace due to their advantages such as low pollution, light weight, and high energy density. In the structure of a rechargeable battery, the negative electrode active material is a crucial component, significantly impacting battery performance. Regarding the factors affecting battery performance, agglomeration of the negative electrode active material can lead to uneven distribution of the material on the negative electrode sheet, thus adversely affecting battery performance. Summary of the Invention

[0003] The first aspect of this application provides a negative electrode active material, including a negative electrode active substrate and polar groups located on the surface of the negative electrode active substrate, the polar groups including amino groups.

[0004] In the negative electrode active material of this application, the surface of the negative electrode active substrate has amino groups, and there are weak interactions between the amino groups, which can improve the dispersion performance between the negative electrode active materials, making it less likely for the negative electrode active materials to agglomerate, and improving the uniformity of the distribution of the negative electrode active materials in the negative electrode sheet.

[0005] A second aspect of this application provides a method for preparing a negative electrode active material, comprising the following steps: oxidizing a negative electrode active substrate to prepare an oxidized substrate; mixing the oxidized substrate with a compound containing polar groups in a dispersion medium, wherein the compound containing polar groups includes an amino compound.

[0006] A third aspect of this application provides a negative electrode slurry, comprising the negative electrode active material of the first aspect or the negative electrode active material prepared by the preparation method of the second aspect.

[0007] A fourth aspect of this application provides a negative electrode sheet, comprising a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector, wherein the negative electrode film layer comprises a negative electrode active material of the first aspect or a negative electrode active material prepared by the preparation method of the second aspect, or the negative electrode film layer is formed by curing a material comprising a negative electrode slurry of the third aspect on at least one surface of the negative current collector.

[0008] The fifth aspect of this application provides a method for preparing a negative electrode sheet according to the fourth aspect, comprising the following steps: coating a negative electrode slurry according to the third aspect onto at least one surface of the current collector, and forming the negative electrode film layer by curing.

[0009] The sixth aspect of this application provides a secondary battery, including a negative electrode sheet prepared by the method of the fourth aspect or the method of the fifth aspect.

[0010] The seventh aspect of this application provides an electrical device including the secondary battery of the sixth aspect. Attached Figure Description

[0011] Figure 1 This is a schematic diagram illustrating the interaction between the negative electrode active material and the binder in one embodiment of this application.

[0012] Figure 2 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0013] Figure 3 yes Figure 2 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0014] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0015] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0016] Figure 6 yes Figure 5 An exploded view of a battery pack according to one embodiment of this application is shown.

[0017] Figure 7 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0018] Figure 8 This is a morphological diagram of the negative electrode slurry in Example 1 of this application.

[0019] Figure 9 This is a morphological diagram of the negative electrode slurry in Comparative Example 1 of this application.

[0020] Explanation of reference numerals in the attached figures:

[0021] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Top cover assembly. Detailed Implementation

[0022] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery assembly, battery cell, secondary battery, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0023] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0024] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0025] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0026] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0027] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0028] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true or exists, and B is false or does not exist; A is false or does not exist, and B is true or exists; or both A and B are true, or both A and B exist.

[0029] Unless otherwise specified, in this application, the terms "positive electrode sheet" and "positive electrode plate" have the same meaning and can be used interchangeably. The terms "negative electrode sheet" and "negative electrode plate" have the same meaning and can be used interchangeably. The terms "diaphragm" and "separating membrane" have the same meaning and can be used interchangeably.

[0030] This application provides a negative electrode active material. The negative electrode active material includes a negative electrode active substrate and polar groups located on the surface of the negative electrode active substrate, the polar groups including amino groups. The surface of the negative electrode active substrate has amino groups, and there are weak interactions between the amino groups, which can improve the dispersion performance between the negative electrode active materials, making it less prone to agglomeration and improving the uniformity of the distribution of the negative electrode active material in the negative electrode sheet.

[0031] Furthermore, in the preparation of the negative electrode sheet, the negative electrode active material is usually mixed with a binder to prepare a slurry. In this case, the negative electrode active material in this application can form covalent bonds with the binder through amino groups, and the bonding effect of these covalent bonds is stronger than ordinary hydrogen bonds. This enhances the adhesion performance of the binder to the negative electrode active material and reduces the interaction between the highly polar functional groups on the binder and its own functional groups, thus reducing the swelling of the binder. This, in turn, improves the fluidity and processing performance of the slurry, while also reducing the risk of pipeline blockage during slurry feeding or transfer.

[0032] Meanwhile, since amino groups are electronegative, when amino groups remain in the negative electrode active material after being combined with the binder, they can promote the migration of lithium ions to the electrode surface during the lithium intercalation process, thereby improving the battery performance.

[0033] In some embodiments, the molar ratio of the negative electrode active substrate to the amino group is 1:(0.03 to 0.05). Optionally, the molar ratio of the negative electrode active substrate to the amino group is 1:0.03, 1:0.032, 1:0.035, 1:0.036, 1:0.038, 1:0.039, 1:0.04, 1:0.042, 1:0.045, 1:0.048, 1:0.05, etc.

[0034] In some embodiments, the polar group further includes a hydroxyl group. Optionally, the molar ratio of the hydroxyl group to the amino group is 1:(0.3 to 1). Optionally, the molar ratio of the hydroxyl group to the amino group is 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.67, 1:0.7, 1:0.75, 1:0.77, 1:0.79, 1:0.8, 1:0.82, 1:0.85, 1:0.89, 1:0.9, 1:0.92, 1:0.95, 1:0.98, 1:1, etc.

[0035] In some embodiments, the polar group also includes a carboxyl group. Optionally, the molar ratio of carboxyl to amino groups is 1:(3-10). Optionally, the molar ratio of carboxyl to amino groups is 1:3, 1:35, 1:4, 1:4.5, 1:4.8, 1:5, 1:5.1, 1:5.2, 1:5.5, 1:5.8, 1:6, 1:6.3, 1:6.5, 1:6.8, 1:7, 1:7.5, 1:7.8, 1:8, 1:8.5, 1:8.8, 1:9, 1:9.5, 1:9.8, 1:10, etc. When the negative electrode active material in this embodiment is applied to a secondary battery, during the formation process, the carboxyl groups in the negative electrode active material are pre-lithiated, and the generated -COOLi can react with HF generated inside the battery, absorbing HF and reducing the corrosion of internal battery components by HF.

[0036] In some embodiments, the negative electrode active substrate includes at least one selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Optionally, the negative electrode active substrate includes at least one selected from artificial graphite and natural graphite. Currently, graphite remains the dominant material for negative electrode active substrates. Graphite can be classified into artificial graphite and natural graphite based on its crystal formation method. Natural graphite is widely used in secondary batteries because it does not require high-temperature graphitization, has low cost, and possesses high capacity. However, due to the high expansion rate of natural graphite during cycling, it is prone to electrode rebound, resulting in poor battery cycle performance and making its cost advantage less significant in power batteries.

[0037] In one embodiment of this application, natural graphite is used as the negative electrode active substrate. Amino groups are introduced onto the surface of the natural graphite. On the one hand, the amino groups can improve the dispersion performance between natural graphite particles, thereby reducing electrode rebound by reducing natural graphite agglomeration. On the other hand, the introduction of amino groups can promote the interaction between natural graphite and the binder. When the aminated natural graphite is applied to the battery, electrode rebound can be reduced, the cycle performance of the battery can be improved, and natural graphite can fully demonstrate its cost advantage in power batteries.

[0038] This application also provides a method for preparing a negative electrode active material. The method includes the following steps: oxidizing a negative electrode active substrate to prepare an oxidized substrate; mixing the oxidized substrate with a compound containing polar groups, including an amino compound, in a dispersion medium. In this preparation method, by oxidizing the negative electrode active substrate, hydroxyl and carboxyl groups can be formed on the surface of the substrate, which can serve as anchoring points for amylation. After the oxidation treatment, the oxidized substrate is mixed with a compound containing polar groups, including an amino compound, in a dispersion medium. Here, the amino compound, using hydroxyl and carboxyl groups as anchoring points, grafts onto the surface of the oxidized substrate, thereby obtaining a negative electrode active material with amino groups.

[0039] In some embodiments, the amino compound has the structure shown in formula (1):

[0040]

[0041] Wherein, X is selected from alkyl with 1 to 6 carbon atoms, aryl with 6 to 14 ring atoms, or heteroaryl with 6 to 14 ring atoms; 1≤k+s+r≤10, 0≤m+p+q+n≤4, and k, s, r, m, p, q, and n are all integers ≥0.

[0042] Optionally, k can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. s can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. r can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. m can be 0, 1, 2, 3, 4. p can be 0, 1, 2, 3, 4. q can be 0, 1, 2, 3, 4. n can be 0, 1, 2, 3, 4.

[0043] It is understood that alkyl groups having 1 to 6 carbon atoms can be, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, 2-ethylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, 1-methylpentyl, 3-methylpentyl, 2-ethylpentyl, 4-methyl-2-pentyl, n-hexyl, 1-methylhexyl, 2-ethylhexyl, 2-butylhexyl, etc. It is also understood that alkyl groups having 1 to 6 carbon atoms include straight-chain alkyl groups having 1 to 6 carbon atoms and branched-chain alkyl groups having 3 to 6 carbon atoms.

[0044] Aryl groups with 6 to 14 ring atoms can be, but are not limited to, phenyl, biphenyl, naphthyl, anthracene, etc.

[0045] A heteroaryl group is defined as an aryl group in which at least one carbon atom is replaced by a non-carbon atom, which can be a nitrogen (N), oxygen (O), sulfur (S), etc. Optionally, heteroaryl groups with 6 to 14 ring atoms include triazine, pyridinyl, pyrimidinyl, benzofuran, benzothiophene, indole, carbazole, and groups formed by the fusion of these groups. Optionally, in the amino compounds of this application, the heteroatom of the heteroaryl group includes a nitrogen (N) atom.

[0046] In some embodiments, k+s+r≥2. In this case, the amino compound has at least two terminal amino groups, which can increase the amino content in the negative electrode active material.

[0047] Examples of amino compounds include one or more of melamine, p-phenylenediamine, 2-methyldiamine-1,3-dimethyltriamine, N,N-bis(aminomethyl)-methanediamine, N,N”-methylenebiguanidine, and N,N-bis(aminomethyl)urea. The structures of melamine, p-phenylenediamine, 2-methyldiamine-1,3-dimethyltriamine, N,N-bis(aminomethyl)-methanediamine, N,N”-methylenebiguanidine, and N,N-bis(aminomethyl)urea are respectively:

[0048] In some embodiments, the molar ratio of the oxide substrate to the amino compound is 1:(0.05 to 0.1). By controlling the molar ratio of the oxide substrate to the amino compound, the amount of amino groups in the negative electrode active material can be effectively adjusted. Optionally, the molar ratio of the oxide substrate to the amino compound is 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, etc.

[0049] In some embodiments, the mass ratio of the oxide substrate to the dispersion medium is 1:(30-50). Optionally, the mass ratio of the oxide substrate to the dispersion medium is 1:30, 1:32, 1:35, 1:38, 1:40, 1:42, 1:45, 1:48, 1:50, etc.

[0050] Understandably, the oxide substrate and the compound containing polar groups are mixed in a dispersion medium under stirring conditions. Optionally, the stirring speed is 1000 rpm to 2000 rpm. Stirring can promote the reaction between the oxide substrate and the amino compound, thereby improving the reaction efficiency. For example, the stirring speed can be, but is not limited to, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, 2000 rpm, etc.

[0051] In some embodiments, the dispersion medium includes at least one of water and ethanol.

[0052] In some embodiments, when mixing the oxide substrate with the compound containing polar groups in a dispersion medium, the oxide substrate is first mixed with the dispersion medium, and then the compound containing polar groups is added. Optionally, mixing the oxide substrate with the dispersion medium includes: mixing the oxide substrate with the dispersion medium and then ultrasonicating. Optionally, the ultrasonication time is 24 hours.

[0053] In some embodiments, after mixing the oxide substrate with a compound containing polar groups in a dispersion medium, the mixture is subjected to solid-liquid separation, and the solid is washed and dried to obtain the dried negative electrode active material. Optionally, the drying can be done by freeze drying, and the drying time can be selected as 24 hours. Optionally, the washing is done with ultrapure water, and the washing can be performed in multiple steps.

[0054] In some embodiments, the oxidation treatment of the negative electrode active substrate includes: mixing the negative electrode active substrate with an oxidant solution and sealing it to carry out the oxidation reaction. Optionally, the mass ratio of the negative electrode active substrate to the oxidant in the oxidant solution is 1:(3-8). For example, the mass ratio of the negative electrode active substrate to the oxidant in the oxidant solution can be, but is not limited to, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, etc. Optionally, the oxidant in the oxidant solution includes H2O2. Optionally, the mass concentration of the oxidant in the oxidant solution is 20%-40%. For example, the mass concentration of the oxidant in the oxidant solution can be, but is not limited to, 20%, 25%, 30%, 35%, 40%, etc. Optionally, the oxidant solution is a 30% H2O2 solution.

[0055] In some embodiments, the oxidation reaction temperature is 30℃ to 40℃. Optionally, the oxidation reaction temperature is 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, etc. The oxidation reaction time is 20h to 30h. Optionally, the oxidation reaction time is 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h, etc. Optionally, the oxidation reaction is carried out under stirring conditions. The stirring speed of the oxidation reaction is 1000rpm to 2000rpm. For example, the stirring speed can be, but is not limited to, 1000rpm, 1100rpm, 1200rpm, 1300rpm, 1400rpm, 1500rpm, 1600rpm, 1700rpm, 1800rpm, 1900rpm, 2000rpm, etc.

[0056] It is understandable that by oxidizing the negative electrode active substrate, hydroxyl and carboxyl groups can be formed on the surface of the negative electrode active substrate. By selecting the oxidation conditions, the molar amount of hydroxyl and carboxyl groups can be adjusted. Then, through the reaction of amino compounds, the molar amount of amino, hydroxyl and carboxyl groups in the negative electrode active material can be adjusted.

[0057] In one embodiment, before mixing the oxidized substrate with the compound containing polar groups in the dispersion medium, the process further includes: centrifuging and washing the product after oxidizing the negative electrode active substrate, and drying the resulting solid. Optionally, the drying can be performed under vacuum at 60°C for 48 hours.

[0058] In another embodiment, the method for preparing the negative electrode active material includes the following steps:

[0059] S01: At 35°C, the negative electrode active substrate is added to a 30% H2O2 solution, sealed, and stirred for 24 hours.

[0060] S02: Centrifuge the mixture obtained from S01 and dry the solid under vacuum at 60°C for 48 hours.

[0061] SO3: Mix the solid obtained from SO2 with deionized water and sonicate for 24 hours.

[0062] S04: Under stirring conditions, a compound containing a polar group is added to a mixture of S03.

[0063] S05: Separate the product after the reaction of S04, wash it multiple times with ultrapure water, and then freeze-dry the obtained solid under vacuum for 24 hours.

[0064] This application also provides a negative electrode slurry. The negative electrode slurry comprises the aforementioned negative electrode active material or a negative electrode active material prepared by the aforementioned method for preparing the negative electrode active material.

[0065] In some embodiments, the negative electrode slurry includes the aforementioned negative electrode active material and negative electrode active substrate.

[0066] In some embodiments, the negative electrode slurry further includes a binder. Optionally, the binder includes a polyacrylic acid binder. Further, the polyacrylic acid binder comprises 50% to 90% by mass of the binder. Optionally, the polyacrylic acid binder comprises 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, etc. by mass of the binder. Even further, the binder also includes a carboxymethyl cellulose binder.

[0067] It is understood that polyacrylic acid binders include polyacrylic acid and its derivatives. Carboxymethyl cellulose binders include carboxymethyl cellulose and its derivatives. Optionally, carboxymethyl cellulose binders include sodium carboxymethyl cellulose.

[0068] In some embodiments, the negative electrode slurry further includes a conductive agent. Optionally, the conductive agent is one or more of carbon fiber, carbon nanotubes, and Super P.

[0069] like Figure 1 As shown, the carboxyl groups in the polyacrylic acid binder can undergo dehydration condensation with the amino groups in the negative electrode active material to form covalent bonds. These covalent bonds are more effective than ordinary hydrogen bonds and can enhance the adhesive properties of the binder. Furthermore, when the negative electrode active material contains hydroxyl groups, the carboxyl groups in the polyacrylic acid binder can undergo esterification with the hydroxyl groups, further improving the adhesive properties.

[0070] In some embodiments, such as Figure 1As shown, when the binder also includes carboxymethyl cellulose binder, the amino groups in the negative electrode active material can combine with the carboxymethyl cellulose binder, which can make the negative electrode active material more compatible with the polyacrylic acid binder and the carboxymethyl cellulose binder, and allow the binder to play a more complete role.

[0071] This application also provides a negative electrode sheet. The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector. The negative electrode film layer includes the aforementioned negative electrode active material or a negative electrode active material prepared by the aforementioned method for preparing the negative electrode active material, or the negative electrode film layer is formed by curing a material including the aforementioned negative electrode slurry onto the negative current collector.

[0072] In some embodiments, the negative electrode film layer also includes a negative electrode active substrate.

[0073] In some embodiments, the negative electrode film layer is divided into a first sub-film layer and a second sub-film layer, with the first sub-film layer being closer to the negative electrode current collector than the second sub-film layer; both the first and second sub-film layers contain negative electrode active materials, and the mass percentage of the negative electrode active material in the second sub-film layer is greater than the mass percentage of the negative electrode active material in the first sub-film layer, based on the mass percentage of the corresponding sub-film layer.

[0074] Optionally, the mass percentage of the negative electrode active material in the first sub-membrane layer is 5% to 45% based on its mass percentage in the first sub-membrane layer. More preferably, the mass percentage of the negative electrode active material in the first sub-membrane layer is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc.

[0075] Optionally, the mass percentage of the negative electrode active material in the second sub-membrane layer is 20% to 95% of the total mass. More preferably, the mass percentage of the negative electrode active material in the second sub-membrane layer is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0076] In some embodiments, both the first and second sub-film layers contain an adhesive. Optionally, the adhesive comprises a polyacrylic acid adhesive, and the mass percentage of the polyacrylic acid adhesive in the second sub-film layer is less than the mass percentage of the polyacrylic acid adhesive in the first sub-film layer, based on the mass percentage of the corresponding sub-film layer.

[0077] Optionally, the polyacrylic acid adhesive comprises 50% to 90% by mass of the adhesive. For example, the polyacrylic acid adhesive comprises 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90% by mass of the adhesive.

[0078] In some embodiments, the adhesive also includes a carboxymethyl cellulose adhesive.

[0079] This application also provides a method for preparing the above-mentioned negative electrode sheet. The method for preparing the negative electrode sheet includes the following steps: coating the above-mentioned negative electrode slurry onto at least one surface of a current collector, and curing it to form a negative electrode film layer.

[0080] This application also provides a secondary battery. The secondary battery includes the aforementioned negative electrode sheet or a negative electrode sheet prepared by the aforementioned method for preparing the negative electrode sheet.

[0081] This application also provides a battery module. The battery module includes the aforementioned secondary battery.

[0082] This application also provides a battery pack. The battery pack includes the aforementioned secondary battery or the aforementioned battery module.

[0083] This application also provides an electrical device. The electrical device includes at least one of the above-mentioned secondary battery, the above-mentioned battery module, and the above-mentioned battery pack.

[0084] The secondary battery will be explained below with reference to the relevant accompanying drawings.

[0085] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0086] [Positive electrode plate]

[0087] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0088] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0089] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on the polymer substrate. Optionally, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Optionally, the polymer substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0090] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and 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 of two or more. Examples of lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxide, 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. Optionally, lithium cobalt oxide includes LiCoO2. Lithium nickel oxide includes LiNiO2. Lithium manganese oxide includes at least one of LiMnO2 and LiMn2O4. Lithium nickel cobalt manganese oxide includes LiNi... 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 ) and LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 At least one of the following. Lithium nickel cobalt aluminum oxides include LiNi 0.85 Co 0.15 Al0.05 O2. Examples of lithium phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Optionally, lithium iron phosphate includes LiFePO4 (LFP). Lithium manganese phosphate includes LiMnPO4.

[0091] In some embodiments, when the secondary battery is a sodium-ion battery, the positive electrode active material can be any positive electrode active material known in the art for sodium-ion batteries. As an example, the positive electrode active material can be a single material or a combination of two or more. The positive electrode active material can be selected from sodium-iron composite oxides, sodium-cobalt composite oxides, sodium-chromium composite oxides, sodium-manganese composite oxides, sodium-nickel composite oxides, sodium-nickel-titanium composite oxides, sodium-nickel-manganese composite oxides, sodium-iron-manganese composite oxides, sodium-nickel-cobalt-manganese composite oxides, sodium-iron phosphate compounds, sodium-manganese phosphate compounds, sodium-cobalt phosphate compounds, Prussian blue-based materials, polyanionic materials, etc., but this application is not limited to these materials. Other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries can also be used. Optionally, the sodium-iron composite oxide includes NaFeO2. The sodium-cobalt composite oxide includes NaCoO2. The sodium-chromium composite oxide includes NaCrO2. The sodium-manganese composite oxide includes NaMnO2. The sodium-nickel composite oxide includes NaNiO2. The sodium-nickel-titanium composite oxide includes NaNi 1 / 2 Ti 1 / 2 O2. Sodium-nickel-manganese composite oxides include NaNi 1 / 2 Mn 1 / 2 O2. Sodium-iron-manganese composite oxides include Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2. Sodium-nickel-cobalt-manganese composite oxides include NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2. Sodium iron phosphate compounds include NaFePO4. Sodium manganese phosphate compounds include NaMnPO4. Sodium cobalt phosphate compounds include NaCoPO4. Polyanionic materials include at least one of phosphates, fluorophosphates, pyrophosphates, and sulfates.

[0092] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0093] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0094] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0095] [Negative electrode plate]

[0096] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0097] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0098] 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on the polymer material substrate. Optionally, the metal material includes at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0099] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0100] In some embodiments, the negative electrode active material includes a negative electrode active substrate and polar groups located on the surface of the negative electrode active substrate, the polar groups including amino groups. The negative electrode active substrate may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active substrates may also be used. These negative electrode active substrates may be used alone or in combination of two or more.

[0101] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyamide-imide (PAI), polyethyleneimine (PEI), polyimide (PI), and tert-butyl polyacrylate-triethoxyvinylsilane (TBATEVS).

[0102] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners. Optionally, the thickener includes sodium carboxymethyl cellulose (CMC-Na).

[0104] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes. Optionally, the solvent includes deionized water.

[0105] Electrolyte

[0106] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements.

[0107] In some embodiments, the electrolyte comprises an electrolyte salt and a solvent.

[0108] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0109] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0110] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0111] [Isolation membrane]

[0112] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0113] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can 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 can be the same or different, without particular limitation.

[0114] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0115] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0116] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0117] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 This is an example of a square-structured secondary battery 5.

[0118] In some implementations, refer to Figure 3 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0119] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0120] Figure 4 This is battery module 4, used as an example. (See reference...) Figure 4 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0121] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0122] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0123] Figure 5 and Figure 6 This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0124] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used 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 and satellites, energy storage systems, etc. For example, mobile devices include mobile phones, laptops, etc. Electric vehicles include pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0125] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0126] Figure 7 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0127] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0128] Example

[0129] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0130] Example 1

[0131] (1) Preparation of negative electrode active material.

[0132] S101: At 35℃, natural graphite is added to a 30% H2O2 solution with a molar ratio of natural graphite to H2O2 of 1:2. The solution is sealed and stirred for 24 hours.

[0133] S102: Centrifuge the mixture obtained from S101 and vacuum dry the solid at 60°C for 48 hours.

[0134] S103: Mix the solid oxide substrate obtained in S102 with deionized water at a mass ratio of 1:40 and ultrasonically treat for 24 hours.

[0135] S104: Under stirring conditions, the amino compound is added to the mixture in S103. The molar ratio of the solid oxide substrate obtained in S102 to the amino compound is 1:0.08.

[0136] S105: The product after the reaction in S104 is separated and washed multiple times with ultrapure water. The resulting solid is then freeze-dried under vacuum for 24 hours. The negative electrode active material of this embodiment is obtained.

[0137] In this embodiment, the amino compound is 2-methyldiamine-1,3-dimethyltriamine.

[0138] (2) Preparation of negative electrode slurry.

[0139] The active material, conductive agent, and binder are stirred and mixed at a speed of 400 r / s to 1000 r / s, and then wetted, kneaded, and dispersed to obtain the negative electrode slurry.

[0140] In the first negative electrode slurry, the binder is polyacrylic acid and sodium carboxymethyl cellulose, with polyacrylic acid accounting for 60% of the binder by mass. The active material includes natural graphite and the negative electrode active material in this embodiment, with a mass ratio of natural graphite to negative electrode active material of 1:(0.05-1). The mass ratio of active material, binder, and conductive agent is (95-98):(1-4):(1-4). The first negative electrode slurry is used to prepare the first sub-film layer.

[0141] In the second negative electrode slurry, the binder is polyacrylic acid and sodium carboxymethyl cellulose, with polyacrylic acid accounting for 60% of the binder by mass. The active material includes natural graphite and the negative electrode active material in this embodiment, with a mass ratio of natural graphite to negative electrode active material of (0–0.75):1. The mass ratio of active material, binder, and conductive agent is (95–98):(1–4):(1–4). The second negative electrode slurry is used to prepare the second sub-film layer.

[0142] (3) Preparation of negative electrode sheet.

[0143] The first negative electrode slurry and the second negative electrode slurry prepared in (2) are sequentially coated onto copper foil and then dried at 80℃~110℃.

[0144] Example 2

[0145] Compared with Example 1, the difference in this example is that the molar ratio of the solid oxide substrate obtained in S102 to the amino compound is 1:0.06.

[0146] Example 3

[0147] Compared with Example 1, the difference in this example is that the molar ratio of the solid oxide substrate obtained in S102 to the amino compound is 1:0.07.

[0148] Example 4

[0149] Compared with Example 1, the difference in this example is that the molar ratio of the solid oxide substrate obtained in S102 to the amino compound is 1:0.09.

[0150] Example 5

[0151] Compared with Example 1, the difference in this example is that the molar ratio of the solid oxide substrate obtained in S102 to the amino compound is 1:0.1.

[0152] Example 6

[0153] The difference between this embodiment and Example 1 is that the amino compound is N,N-bis(aminomethyl)-methanediamine.

[0154] Example 7

[0155] The difference between this embodiment and Example 1 is that the amino compound is melamine.

[0156] Comparative Example 1

[0157] Compared with Example 1, the difference in this comparative example is that the negative electrode active material is a solid oxide substrate obtained by S102.

[0158] Comparative Example 2

[0159] Compared with Example 1, the difference of this comparative example is that the molar ratio of the solid oxide substrate obtained in S102 to the amino compound is 1:0.03.

[0160] Comparative Example 3

[0161] Compared with Example 1, the difference in this comparative example is that the molar ratio of the solid oxide substrate obtained in S102 to the amino compound is 1:0.15.

[0162] Comparative Example 4

[0163] The difference between this comparative example and Example 1 is that the negative electrode active material is natural graphite in S101.

[0164] Test case

[0165] The negative electrode, positive electrode, separator, and electrolyte prepared in the examples and comparative examples were assembled into a secondary battery.

[0166] in:

[0167] (1) Preparation of positive electrode sheet.

[0168] The positive electrode active material is lithium nickel cobalt manganese oxide (NCM523, i.e., LiNi). 0.5 Co 0.2 Mn 0.3 O2), polyvinylidene fluoride (PVDF) binder, and acetylene black (SP) conductive agent were mixed in a weight ratio of 98:1:1. N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred under vacuum until homogeneous. The resulting slurry was then coated onto aluminum foil and dried.

[0169] (2) Preparation of electrolyte.

[0170] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) / ethyl methyl carbonate (EMC) organic solvents were mixed evenly at a volume ratio of 3 / 7. 12.5% ​​by weight (based on the weight of ethylene carbonate / ethyl methyl carbonate solvent) of LiPF6 was added and dissolved in the above organic solvents and stirred evenly to obtain the electrolyte.

[0171] (3) Separation membrane.

[0172] Use commercially available PP-PE copolymer microporous films with a thickness of 7μm and an average pore size of 80nm.

[0173] Test metrics

[0174] (1) The shapes of the negative electrode slurries obtained in the examples and comparative examples were observed. Specifically, the properties of the first and second negative electrode slurries in Example 1 are as follows: Figure 8 As shown, Figure 8 (a) is the second negative electrode slurry. Figure 8 (b) represents the first negative electrode slurry. The properties of the first and second negative electrode slurries in Comparative Example 1 are as follows: Figure 9 As shown, Figure 9 (a) is the second negative electrode slurry. Figure 9 (b) is the first negative electrode slurry. (From...) Figure 8 and Figure 9 It can be seen that the negative electrode slurry in Example 1 has better fluidity than the negative electrode slurry in Comparative Example 1.

[0175] (2) The peel strength of the negative electrode sheets obtained in the examples and comparative examples was tested. The test method was to test the adhesion force of the active layer of the negative electrode sheet using a tensile testing machine. The results are shown in Table 1.

[0176] (3) The full-charge rebound rate of the negative electrode sheets obtained in the examples and comparative examples was tested. The test method was as follows: the cell was disassembled after full charging, the electrode sheet thickness was measured, and the electrode sheet thickness was compared with that during cold pressing to calculate the full-charge rebound rate. The results are shown in Table 1. As can be seen from Table 1, the peel strength of Example 1 is greater and the full-charge rebound rate is smaller, indicating that the active material and binder in the negative electrode slurry of Example 1 have better compatibility.

[0177] (4) Cyclic tests were conducted on the batteries obtained in the examples and comparative examples. The test results are shown in Table 2.

[0178] (5) Storage performance tests were conducted on the batteries obtained in the examples and comparative examples. The storage conditions were 60°C for 30 days. The performance indicators before and after storage are shown in Table 3. The recovery rate was tested by dividing the capacity of the cell after storage by the capacity before storage after charging and discharging at a low rate of 0.04C. A higher value indicates that the capacity loss before and after storage is a reversible capacity loss.

[0179] As shown in Table 3, when X in the amino compound is not aryl or heteroaryl, and the molar ratio of the amino compound to the oxide substrate is less than 0.05, the aminated graphite enhances the stability of the negative electrode and significantly improves the capacity. However, the degree of amylation is low at this point, leaving many oxygen-containing groups on the graphite surface. Furthermore, the introduction of amino groups increases the interlayer spacing of the graphite, weakens the π-bond interaction, and reduces conductivity, thus increasing the DCR. When the molar ratio of the amino compound to the oxide substrate is 0.05–0.1, the degree of amylation increases, and a large number of oxygen-containing groups on the graphite surface are replaced by amino groups, resulting in a smaller DCR and further improvement in cycle and storage performance. When the molar ratio of the amino compound to the oxide substrate is greater than 0.1, the amount of amino compound used further increases, but the capacity no longer increases, indicating that the degree of amylation has reached its maximum. At this point, the interlayer spacing of the graphite increases to a critical value due to the introduction of amino groups, and the negative electrode performance begins to deteriorate. Furthermore, when X in the amino compound is aryl or heteroaryl, the storage and cycling performance is inferior to that of the examples of amino compounds where X is neither aryl nor heteroaryl. This indicates that although the conjugation effect of the six-membered ring makes its structure stable and has good resistance to Li + Migration has a certain promoting effect, but the conjugated six-membered ring also makes the amino position inflexible, and its bonding effect with binders is not as good as that of amino compounds in which X is not aryl or heteroaryl, thus affecting the electrode rebound rate, and consequently affecting cycle and storage performance.

[0180] (6) The molar amounts of the negative electrode active substrate, amino groups, hydroxyl groups, and carboxyl groups in the negative electrode active materials obtained in the examples and comparative examples were tested. The molar amount of the negative electrode active substrate was calculated from the mass of the negative electrode active substrate and the molar mass of carbon. The amino content was tested by hydrochloric acid titration, the hydroxyl content was tested by acetic anhydride-sodium acetate method, and the carboxyl group content was tested by calcium acetate method.

[0181] The steps of the hydrochloric acid titration method are as follows: ① Weigh 0.0025g of the negative electrode active material sample using a balance, accurate to 0.0001g, into a 400ml beaker. ② Add 15ml of glacial acetic acid to the beaker to completely dissolve the sample. If necessary, heat to dissolve. Add 200ml of water, 30ml of 6mol / L hydrochloric acid solution, and 1g of potassium bromide. ③ Place the magnetic stirring strip in the beaker and place it on a magnetic stirrer with an ice-water bath. Stir and cool continuously until the temperature drops to approximately 0-5℃. Add 0.1mol / L sodium nitrite standard solution dropwise until the starch-potassium iodide test paper turns blue after spotting, and the color remains unchanged for 5 minutes. The amino value % = M*c*V*1 / 1000*100% / G, where M is the molar mass of sodium nitrite, c is the concentration of sodium nitrite standard solution (mol / L), V is the volume of sodium nitrite standard solution consumed, and G is the mass of the negative electrode active material weighed.

[0182] The steps of the acetic anhydride-sodium acetate method are as follows: Under heating conditions, pentaerythritol undergoes a quantitative acetylation reaction with an acetylation reagent to produce an ester and acetic acid. The generated acid and the remaining acetylation reagent are neutralized with alkali. Then, a quantitative amount of alkali is added to react with the generated ester to undergo a saponification reaction, reducing the hydroxyl groups. Excess alkali is titrated with a standard sulfuric acid solution. Under the same conditions, pentaerythritol is replaced with the active material sample. The difference in the amount of standard sulfuric acid solution consumed in the pentaerythritol experiment and the active material sample experiment is the amount of alkali consumed in the saponification reaction of the ester. The hydroxyl content of the active material sample can then be determined.

[0183] The steps of the calcium acetate method are as follows: Immerse the negative electrode active material sample in 0.5% HCl for 40 min, then wash with deionized water until no Cl is visible, air dry, and store in a desiccator. Accurately weigh 1 g of the HCl-treated sample and immerse it in a 250 ml iodine flask with freshly prepared 0.1 mol / L calcium acetate solution. Let it stand for 12–17 h, shaking frequently, to obtain the test solution. Pipette 10 ml of the test solution into a 250 ml Erlenmeyer flask, and titrate with 0.1 mol / L NaOH standard solution using methyl red and thymol blue as mixed indicators until the solution color changes from yellow to purplish-rose. By calculating the amount of NaOH consumed, the amount of acetic acid produced by the reaction of the sample with calcium acetate can be determined, and thus the amount of carboxyl groups in the sample can be calculated.

[0184] The test results are shown in Table 1.

[0185] Table 1

[0186]

[0187] Table 2

[0188]

[0189] Table 3

[0190]

[0191]

[0192] As shown in Tables 1-3, the presence of amino groups in the negative electrode active material can improve the battery's cycle performance. Furthermore, the presence of hydroxyl and carboxyl groups in the negative electrode active material can further enhance the battery's cycle performance.

[0193] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A negative electrode active material, characterized in that, It includes a negative electrode active substrate and polar groups located on the surface of the negative electrode active substrate, wherein the polar groups include amino groups; the amino compound has the structure shown in formula (1): Equation (1), Wherein, X is selected from alkyl with 1 to 6 carbon atoms, aryl with 6 to 14 ring atoms, or heteroaryl with 6 to 14 ring atoms; 1≤k+s+r≤10, 0≤m+p+q+n≤4, and k, s, r, m, p, q, and n are all integers ≥0.

2. The negative electrode active material according to claim 1, characterized in that, The molar ratio of the negative electrode active substrate to the amino group is 1:(0.03~0.05).

3. The negative electrode active material according to claim 1, characterized in that, The polar group also includes hydroxyl groups.

4. The negative electrode active material according to claim 3, characterized in that, The molar ratio of the hydroxyl group to the amino group is 1:(0.3~1).

5. The negative electrode active material according to claim 1, characterized in that, The polar groups also include carboxyl groups.

6. The negative electrode active material according to claim 1, characterized in that, The molar ratio of the carboxyl group to the amino group is 1:(3~10).

7. The negative electrode active material according to any one of claims 1 to 6, characterized in that, The negative electrode active substrate includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

8. The negative electrode active material according to any one of claims 1 to 6, characterized in that, The negative electrode active substrate includes at least one of artificial graphite and natural graphite.

9. A method for preparing a negative electrode active material, characterized in that, Includes the following steps: An oxide substrate is prepared by oxidizing the negative electrode active substrate. The oxide substrate is mixed with a compound containing polar groups in a dispersion medium, the compound containing polar groups including an amino compound; the amino compound has the structure shown in formula (1): Equation (1), Wherein, X is selected from alkyl with 1 to 6 carbon atoms, aryl with 6 to 14 ring atoms, or heteroaryl with 6 to 14 ring atoms; 1≤k+s+r≤10, 0≤m+p+q+n≤4, and k, s, r, m, p, q, and n are all integers ≥0.

10. The method for preparing the negative electrode active material according to claim 9, characterized in that, The amino compound satisfies at least one of the following characteristics: (1) k + s + r ≥ 2; (2) The heteroatom of the heteroaryl group includes a nitrogen atom.

11. The method for preparing the negative electrode active material according to claim 9, characterized in that, The amino compound includes one or more of melamine, p-phenylenediamine, 2-methyldiamine-1,3-dimethyltriamine, N,N-bis(aminomethyl)-methanediamine, N,N''-methylenebiguanidine, and N,N-bis(aminomethyl)urea.

12. The method for preparing the negative electrode active material according to any one of claims 9 to 11, characterized in that, The oxide substrate is mixed with a compound containing polar groups in a dispersion medium to satisfy at least one of the following characteristics: (1) The molar ratio of the oxide substrate to the amino compound is 1:(0.05~0.1). (2) The mass ratio of the oxide substrate to the dispersion medium is 1:(30~50); (3) The mixing is carried out under stirring conditions; the stirring speed is 1000 rpm to 2000 rpm; (4) The dispersion medium includes at least one of water and ethanol; (5) First, the oxide substrate is mixed with the dispersion medium, and then the compound containing polar groups is added.

13. The method for preparing the negative electrode active material according to any one of claims 9 to 11, characterized in that, The oxidation treatment of the negative electrode active substrate includes: mixing the negative electrode active substrate with an oxidant solution and sealing it to carry out the oxidation reaction.

14. The method for preparing the negative electrode active material according to claim 13, characterized in that, The molar ratio of the negative electrode active substrate to the oxidant in the oxidant solution is 1:(1.2~3).

15. The method for preparing the negative electrode active material according to claim 13, characterized in that, The oxidant in the oxidant solution includes H2O2.

16. The method for preparing the negative electrode active material according to claim 13, characterized in that, The mass concentration of the oxidant in the oxidant solution is 20% to 40%.

17. The method for preparing the negative electrode active material according to claim 13, characterized in that, The oxidation reaction is carried out at a temperature of 30℃~40℃.

18. The method for preparing the negative electrode active material according to claim 13, characterized in that, The oxidation reaction takes 20-30 hours.

19. The method for preparing the negative electrode active material according to claim 13, characterized in that, The stirring speed for the oxidation reaction is 1000 rpm to 2000 rpm.

20. A negative electrode slurry, characterized in that, It includes the negative electrode active material according to any one of claims 1 to 8 or the negative electrode active material prepared by the preparation method according to any one of claims 9 to 19.

21. The negative electrode slurry according to claim 20, characterized in that, It also includes adhesives.

22. The negative electrode slurry according to claim 21, characterized in that, The adhesive satisfies at least one of the following characteristics: (1) The adhesive includes a polyacrylic acid adhesive; (2) The polyacrylic acid adhesive comprises 50% to 90% by mass percentage of the adhesive. (3) The adhesive also includes carboxymethyl cellulose adhesive.

23. A negative electrode sheet, characterized in that, It includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector. The negative electrode film layer includes the negative electrode active material according to any one of claims 1 to 8 or the negative electrode active material prepared by the preparation method according to any one of claims 9 to 19, or the negative electrode film layer is formed by curing a material including the negative electrode slurry according to any one of claims 20 to 22 on at least one surface of the negative electrode current collector.

24. The negative electrode sheet according to claim 23, characterized in that, The negative electrode film layer is divided into a first sub-film layer and a second sub-film layer. The first sub-film layer is closer to the negative electrode current collector than the second sub-film layer. Both the first sub-film layer and the second sub-film layer contain the negative electrode active material. The mass percentage of the negative electrode active material in the second sub-film layer is greater than the mass percentage of the negative electrode active material in the first sub-film layer.

25. The negative electrode sheet according to claim 24, characterized in that, The negative electrode active material in the first sub-membrane layer is 5% to 45% by mass percentage of the first sub-membrane layer.

26. The negative electrode sheet according to claim 24, characterized in that, The negative electrode active material in the second sub-membrane layer is 20% to 95% by mass percentage, accounting for 20% to 95% of the second sub-membrane layer.

27. The negative electrode sheet according to any one of claims 24 to 26, characterized in that, Both the first sub-film layer and the second sub-film layer contain an adhesive.

28. The negative electrode sheet according to claim 27, characterized in that, The adhesive satisfies at least one of the following characteristics: (1) The adhesive includes a polyacrylic acid adhesive, and the mass percentage of the polyacrylic acid adhesive in the second sub-film layer is less than the mass percentage of the polyacrylic acid adhesive in the first sub-film layer. (2) The polyacrylic acid adhesive comprises 50% to 90% by mass percentage of the adhesive. (3) The adhesive also includes carboxymethyl cellulose adhesive.

29. A method for preparing a negative electrode sheet according to any one of claims 23-28, characterized in that, Includes the following steps: The negative electrode slurry according to any one of claims 20 to 22 is coated on at least one surface of the current collector, and the negative electrode film layer is formed by curing.

30. A secondary battery, characterized in that, Includes the negative electrode sheet according to any one of claims 23 to 28 or the negative electrode sheet prepared by the preparation method according to claim 29.

31. An electrical device, characterized in that, Includes the secondary battery as described in claim 30.

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