Negative active material, method of manufacturing the same, and related device

Abstract

The embodiment of the present application provides a kind of negative active material and its preparation method and related device.The negative active material includes: negative active substance and cladding layer, cladding layer is coated on the surface of negative active substance, and cladding layer includes at least one of polymethyl methacrylate, sodium maleate and oleic acid diethanolamide borate.The technical scheme of the present application can improve the cycle performance and first circle coulomb efficiency of battery.

Description

Technical Field

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

[0002] In recent years, the application fields of lithium-ion batteries have become increasingly widespread, including wind power, hydropower, thermal power generation, energy storage power sources such as solar cells, as well as electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. While lithium-ion batteries have achieved tremendous development, higher requirements have also been placed on their performance in various aspects.

[0003] Therefore, how to improve the performance of lithium-ion batteries is an urgent problem to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a negative electrode active material and its preparation method, a negative electrode sheet, a battery cell, a battery, and an electrical device, which improves the cycle performance and first-cycle coulombic efficiency of the battery.

[0005] A first aspect of this application provides a negative electrode active material, comprising: a negative electrode active substance and a coating layer, wherein the coating layer coats the surface of the negative electrode active substance, and the coating layer comprises at least one selected from polymethyl methacrylate, sodium maleate and oleic diethanolamide borate.

[0006] In this embodiment, the negative electrode active material includes a negative electrode active substance and a coating layer. The coating layer is coated on the surface of the negative electrode active substance and includes at least one of polymethyl methacrylate, sodium maleate, and oleic acid diethanolamide borate. By coating the surface of the negative electrode active substance with a coating layer comprising at least one of polymethyl methacrylate, sodium maleate, and oleic acid diethanolamide borate, such a coating layer has flexible properties. This can reduce the material structure damage caused by repeated lithium ion conduction and suppress the interfacial reaction between the electrolyte and the negative electrode surface, thereby reducing the consumption of irreversible active ions and improving the lithium ion insertion / extraction efficiency, thus improving the first-cycle coulombic efficiency and cycle performance of the battery.

[0007] In one possible implementation, the thickness of the coating layer is 5nm-50nm, and optionally, the thickness of the coating layer is 10nm-20nm.

[0008] In this embodiment, if the coating layer is too thin, the coating layer does not adequately cover the negative electrode active material, and its effect on suppressing the negative electrode interface reaction is not obvious; if the coating layer is too thick, it will affect the lithium ion transport rate. Therefore, by making the coating layer thickness 5nm-50nm, especially 10nm-20nm, it helps to further improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0009] In one possible implementation, the polymethyl methacrylate has a molecular weight of 500,000-2,000,000, or optionally, the molecular weight of the polymethyl methacrylate is 1,000,000-1,500,000.

[0010] In this embodiment, a negative electrode active material comprising a negative electrode active material and a coating layer is formed by polymerizing methyl methacrylate and a negative electrode active material. This preparation method is simple and uses abundant raw materials, which is beneficial for its widespread application in industrial production. In addition, using polymethyl methacrylate with a molecular weight of 500,000-2,000,000, especially 1,000,000-1,500,000, and a high degree of polymerization as the coating layer of the negative electrode active material is beneficial for the coating layer to fully exert its function.

[0011] In one possible implementation, the negative electrode active material includes at least one of graphite and silicon-based materials. Optionally, the silicon-based material includes at least one of elemental silicon, silicon oxide compounds, silicon-carbon compounds, silicon-nitrogen complexes, and complexes of elemental silicon, silicon oxide compounds, and silicon-carbon compounds. Optionally, the silicon oxide compound includes Si. a O b Where a = 1, 1 ≤ b ≤ 2; optionally, the silicon carbide includes Si c C d , where c = 1, d = 1.

[0012] In this embodiment, at least one of graphite and silicon-based materials is used as the negative electrode active material. Further, at least one of elemental silicon, silicon oxide compounds, silicon-carbon compounds, silicon-nitrogen composites, and composites of elemental silicon, silicon oxide compounds, and silicon-carbon compounds is used. Even further, Si is used. a O b Si c C d At least one of the following, where a = 1, 1 ≤ b ≤ 2, c = 1, and d = 1, serves as the negative electrode active material and helps to improve the energy density of the battery.

[0013] A second aspect of this application provides a method for preparing a negative electrode active material, comprising: providing a negative electrode active substance and a coating substance; mixing the negative electrode active substance and the coating substance, and processing them to obtain the negative electrode active substance and a coating layer covering the surface of the negative electrode active substance; wherein the coating substance comprises at least one of methyl methacrylate, sodium maleate and oleic acid diethanolamide borate.

[0014] In this embodiment, by mixing and processing the negative electrode active material and the coating material, a negative electrode active material comprising the negative electrode active material and a coating layer covering the surface of the negative electrode active material can be obtained; wherein, the coating material comprises at least one of methyl methacrylate, sodium maleate, and oleic diethanolamide borate. The negative electrode active material prepared by this method can enable the battery comprising the negative electrode active material to have better cycle performance and first-cycle coulombic efficiency.

[0015] In one possible implementation, the thickness of the coating layer is 5nm-50nm, and optionally, the thickness of the coating layer is 10nm-20nm.

[0016] In this embodiment of the application, by making the thickness of the coating layer 5nm-50nm, especially 10nm-20nm, it helps to further improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0017] In one possible implementation, the methyl methacrylate is polymerized to form the coating layer, the coating layer comprising polymethyl methacrylate; wherein the molecular weight of the polymethyl methacrylate is 500,000-2,000,000, or optionally, the molecular weight of the polymethyl methacrylate is 1,000,000-2,000,000.

[0018] In this embodiment, a coating layer is formed by polymerizing methyl methacrylate, resulting in a negative electrode active material comprising the negative electrode active material and the coating layer. This preparation method is simple and uses abundant raw materials, which is beneficial for its widespread application in industrial production. In addition, using polymethyl methacrylate with a molecular weight of 500,000-2,000,000 and a high degree of polymerization as the coating layer for the negative electrode active material is beneficial for the coating layer to fully exert its function.

[0019] In one possible implementation, the mass ratio of methyl methacrylate to the negative electrode active material is 1-5, and optionally, the mass ratio of methyl methacrylate to the negative electrode active material is 1.5-3.

[0020] In this embodiment, the different mass ratios of the negative electrode active material to methyl methacrylate directly affect the thickness of the coating layer. Therefore, by making the mass ratio of methyl methacrylate to the negative electrode active material 1-5, particularly 1.5-3, a more reasonable coating layer thickness can be achieved, thereby maximizing the coating layer's effectiveness.

[0021] In one possible implementation, the processing temperature of the negative electrode active material and the methyl methacrylate is not lower than 60°C, and optionally, the processing temperature is 60°C-220°C.

[0022] In this embodiment, methyl methacrylate (MMA) is polymerized to form polymethyl methacrylate (PMMA), which serves as a coating layer to encapsulate the negative electrode active material. If the processing temperature is too low, the MMA may fail to polymerize; if the processing temperature is too high, it will affect the relative molecular mass of the MMA, leading to a decrease in its performance. Therefore, by maintaining the processing temperature of the negative electrode active material and MMA at no less than 60°C, particularly between 60°C and 220°C, the resulting MMA exhibits better performance, contributing to further improvements in battery performance.

[0023] In one possible implementation, the treatment time for the negative electrode active material and the methyl methacrylate is 1h-8h, and optionally, the treatment time is 3h-5h.

[0024] In this embodiment of the application, by maintaining the treatment time of the negative electrode active material and methyl methacrylate at 1h-8h, especially at 3h-5h, the polymethyl methacrylate can have a reasonable thickness, thereby improving battery performance.

[0025] In one possible implementation, the catalyst, the negative electrode active material, and the methyl methacrylate are mixed. Optionally, the catalyst includes at least one of an organic peroxide and an azo compound.

[0026] In this embodiment, a catalyst is added to the reaction between methyl methacrylate and the negative electrode active material. The catalyst can lower the activation energy of the polymerization reaction and accelerate the polymerization process. Therefore, by adding a catalyst during the polymerization of polymethyl methacrylate, and the catalyst can be at least one of organic peroxides and azo compounds, the formation of polymethyl methacrylate can be accelerated.

[0027] In one possible implementation, the coating material includes at least one of sodium maleate and oleic acid diethanolamide borate; the processing temperature of the negative electrode active material with at least one of sodium maleate and oleic acid diethanolamide borate is not lower than 40°C, and optionally, the processing temperature is 40°C-120°C.

[0028] In this embodiment, by mixing the negative electrode active material with sodium maleate or oleic acid diethanolamide borate, a negative electrode active material including a negative electrode active material and a coating layer can be obtained. Maintaining the processing temperature of both at no less than 40°C, especially 40°C-120°C, can prevent damage to the activity of the coating layer, thereby improving the performance of the battery.

[0029] In one possible implementation, the mass ratio of at least one of sodium maleate and oleic acid diethanolamide borate to the negative electrode active material is 1-3; alternatively, the mass ratio of at least one of sodium maleate and oleic acid diethanolamide borate to the negative electrode active material is 1-2.

[0030] In the embodiments of this application, when at least one of sodium maleate and oleic acid diethanolamide borate is used as a coating layer to coat the negative electrode active material, the two can be directly mixed at a certain temperature. By making the mass ratio of at least one of sodium maleate and oleic acid diethanolamide borate to the negative electrode active material 1-3, especially 1-2, the coating layer can have a suitable thickness to improve the battery performance.

[0031] In one possible implementation, the negative electrode active material includes at least one of graphite and silicon-based materials. Optionally, the silicon-based material includes at least one of elemental silicon, silicon oxide compounds, silicon-carbon compounds, silicon-nitrogen complexes, and complexes of elemental silicon, silicon oxide compounds, and silicon-carbon compounds. Optionally, the silicon oxide compound includes Si. a O b Where a = 1, 1 ≤ b ≤ 2; optionally, the silicon carbide includes Si c C d , where c = 1, d = 1.

[0032] The third aspect of this application provides a negative electrode sheet, comprising a negative electrode active material prepared by any embodiment of the first aspect, and / or a negative electrode active material prepared by any embodiment of the second aspect.

[0033] A fourth aspect of this application provides a battery cell including the negative electrode sheet described in the third aspect.

[0034] The fifth aspect of this application provides a battery comprising the battery cell described in the fourth aspect.

[0035] A sixth aspect of this application provides an electrical device comprising the battery described in the fifth aspect. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of the negative electrode active material according to one embodiment of this application;

[0038] Figure 2 This is a TEM image of the negative electrode active material according to an embodiment of this application;

[0039] Figure 3 This is a flowchart illustrating the preparation process of the negative electrode active material according to one embodiment of this application;

[0040] Figure 4 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0041] Figure 5 This is a schematic diagram of the structure of a battery cell according to another embodiment of this application;

[0042] Figure 6 This is a schematic diagram of a battery according to one embodiment of this application;

[0043] Figure 7 This is a schematic diagram of the structure of a battery according to one embodiment of this application;

[0044] Figure 8 This is a schematic diagram of the structure of an electrical device according to one embodiment of this application. Detailed Implementation

[0045] The following detailed description, with appropriate reference to the accompanying drawings, outlines embodiments of the negative electrode active material, its preparation method, the negative electrode sheet, the battery cell, the battery, and the power supply device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of practically identical structures may be omitted. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0046] 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 specific 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 expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​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.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0048] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0049] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, optionally 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 method may also 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 it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0050] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0051] The terms “above,” “below,” “greater than,” or “less than” used in this application include the number itself, such as “at least one” meaning one or more, and “at least one of A and B” meaning “A,” “B,” or “A and B.”

[0052] 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 exist).

[0053] The cycle life of lithium-ion batteries is related to the stability of interfaces (such as the electrode-electrolyte interface). Interface formation is often accompanied by irreversible lithium-ion consumption, especially at the interface between the negative electrode and the electrolyte. This is because the solid electrolyte interphase (SEI) film formed during the first charge and discharge cycle consumes a significant amount of lithium ions, and this consumption is irreversible. Excessive lithium-ion consumption can significantly impact battery performance. Therefore, minimizing the irreversible consumption of a limited number of lithium ions is crucial for improving the cycle stability and coulombic efficiency of lithium-ion batteries.

[0054] To address these issues, one approach is to replenish active lithium, such as by adding lithium-replenishing materials or constructing lithium-replenishing structures within the battery. However, these materials typically exhibit high activity, placing stringent requirements on battery processing conditions and limiting their industrialization potential. Another approach is to reduce active lithium consumption, for example, by applying a polymeric aluminum foil film layer to the surface of the negative electrode active material. However, this method is complex and also has limited industrialization potential. Therefore, finding a more direct way to reduce active lithium-ion consumption and thus improve battery cycle performance is a pressing issue that needs to be addressed.

[0055] In view of this, this application provides a negative electrode active material and a method for preparing the same. The negative electrode active material includes: a negative electrode active substance and a coating layer, wherein the coating layer is coated on the surface of the negative electrode active substance, and the coating layer includes at least one selected from polymethyl methacrylate, sodium maleate, and oleic acid diethanolamide borate. By directly coating at least one of polymethyl methacrylate, sodium maleate, and oleic acid diethanolamide borate onto the surface of the substrate, the cycle performance and first-cycle coulombic efficiency of the battery using this negative electrode active material can be improved.

[0056] The following description, with reference to the accompanying drawings, illustrates the negative electrode active material, its preparation method, the negative electrode sheet, the battery cell, the battery, and the power device of this application.

[0057] Furthermore, the technical solution of this application is applicable to lithium-ion batteries or lithium metal batteries, and this application does not limit it; for the sake of convenience, the following description uses lithium-ion batteries as an example.

[0058] [Negative Electrode Active Materials]

[0059] Figure 1This is a schematic diagram of the structure of the negative electrode active material according to one embodiment of this application. Figure 2 This is a TEM image of the negative electrode active material according to one embodiment of this application. Figure 1 and Figure 2 As shown, the negative electrode active material 122 includes a negative electrode active substance 1221 and a coating layer 1222. The coating layer 1222 coats the surface of the negative electrode active substance 1221 and includes at least one of polymethyl methacrylate, sodium maleate and oleic diethanolamide borate.

[0060] Coating the surface of the negative electrode active material with at least one of polymethyl methacrylate, sodium maleate, and oleic diethanolamide borate can improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0061] The covering here can be as follows: Figure 1 The complete coverage shown can also be as follows: Figure 2 The portion shown is covered.

[0062] In this embodiment, the negative electrode active material includes a negative electrode active material 1221 and a coating layer 1222. Further, the coating layer 1222 coats the surface of the negative electrode active material 1221, and the coating layer 1222 includes at least one of polymethyl methacrylate, sodium maleate, and oleic acid diethanolamide borate. By coating the surface of the negative electrode active material 1221 with a coating layer 1222, and the coating layer 1222 including at least one of polymethyl methacrylate, sodium maleate, and oleic acid diethanolamide borate, such a coating layer 1222 has flexible properties. This can reduce the material structure damage caused by repeated lithium ion conduction in the coating layer 1222, and can also suppress the interfacial reaction between the electrolyte and the negative electrode surface, thereby reducing the consumption of irreversible active ions and improving the lithium ion insertion / extraction efficiency, thus improving the first-cycle coulombic efficiency and cycle performance of the battery.

[0063] It should be noted that during battery cycling, a solid electrolyte interface (SEI) film forms on the surface of the negative electrode. The coating layer 1222 is relatively close to this SEI film, so the coating layer 1222 can act as an "artificial" SEI film, forming a double SEI film with the SEI film formed by the battery, thereby inducing the formation of a more stable and thinner SEI film.

[0064] The SEI film is a passivation layer formed on the surface of the active material during the first charge and discharge process of a lithium-ion battery, resulting from the reaction between the active material and the electrolyte at the solid-liquid interface. The coating layer 1222, referred to as an "artificial" SEI film, means that it can function as an SEI film, but it is not a true SEI film.

[0065] In addition, it should be understood that the “lithium intercalation” or “intercalation” process described in this application refers to the process in which lithium ions are intercalated into the positive electrode active material or the negative electrode active material due to an electrochemical reaction, and the “deintercalation” or “deintercalation” process described in this application refers to the process in which lithium ions are deintercalated into the positive electrode active material or the negative electrode active material due to an electrochemical reaction.

[0066] In some embodiments, the thickness d1 of the coating layer 1222 is 5nm-50nm, and optionally, the thickness d1 of the coating layer is 10nm-20nm.

[0067] In the above scheme, if the thickness of the coating layer 1222 is too thin, the coating layer 1222 will not adequately cover the negative electrode active material 1221, and its effect on suppressing the negative electrode interface reaction will be insignificant; if the thickness of the coating layer 1222 is too thick, it will affect the metal ion transport rate. Therefore, by making the thickness of the coating layer 1222 5nm-50nm, especially 10nm-20nm, it is helpful to further improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0068] It should be noted that the thickness of the coating layer can be 5nm, 15nm, 20nm, 40nm, or any value within the above range.

[0069] In some embodiments, the molecular weight of polymethyl methacrylate is 500,000-2,000,000, and optionally, the molecular weight of the polymethyl methacrylate is 1,000,000-1,500,000.

[0070] In this embodiment, a negative electrode active material 122 comprising negative electrode active material 1221 and a coating layer 1222 is formed by polymerizing methyl methacrylate and negative electrode active material 1221. This preparation method is simple and uses abundant raw materials, which is beneficial for its widespread application in industrial production. In addition, using polymethyl methacrylate with a molecular weight of 500,000-2,000,000, especially 1,000,000-1,500,000, and a high degree of polymerization as the coating layer 1222 of the negative electrode active material 1221 is beneficial for the coating layer 1222 to fully exert its function.

[0071] It should be noted that the molecular weight of polymethyl methacrylate can be 500,000, 800,000, 1,000,000, 1,500,000, or any value within the above range.

[0072] In addition, the molecular weight of polymethyl methacrylate varies depending on its thickness.

[0073] In some embodiments, the negative electrode active material 1221 includes at least one of graphite and silicon-based materials. Optionally, the silicon-based material includes at least one of elemental silicon, silicon oxide compounds, silicon-carbon compounds, silicon-nitrogen complexes, and complexes of elemental silicon, silicon oxide compounds, and silicon-carbon compounds. Optionally, the silicon oxide compound includes Si... a O b Where a = 1, 1 ≤ b ≤ 2; optionally, the silicon carbide includes Si c C d , where c = 1, d = 1.

[0074] In the above scheme, at least one of graphite and silicon-based materials is used as the negative electrode active material. Further, at least one of elemental silicon, silicon oxide compounds, silicon-carbon compounds, silicon-nitrogen composites, and composites of elemental silicon, silicon oxide compounds, and silicon-carbon compounds is used. Even further, Si is used. a O b Si c C d At least one of the following, where a = 1, 1 ≤ b ≤ 2, c = 1, and d = 1, serves as the negative electrode active material and helps to improve the energy density of the battery.

[0075] Complexes of elemental silicon, silicon oxides, and silicon carbon compounds can include complexes formed by two of these three compounds, such as multilayer composite structures formed by Si, SiO2, and C, i.e., Si@SiO2@C.

[0076] [Preparation method of negative electrode active material]

[0077] The second aspect of this application provides a method for preparing a negative electrode active material. Figure 3 This is a flowchart illustrating the preparation process of the negative electrode active material according to one embodiment of this application. Figure 3 As shown, the preparation method of this negative electrode active material includes:

[0078] S101 provides negative electrode active material and coating material;

[0079] S102, the negative electrode active material and the coating material are mixed and processed to obtain the negative electrode active material and the coating layer on the surface of the negative electrode active material; wherein, the coating material includes at least one of methyl methacrylate, sodium maleate and oleic acid diethanolamide borate.

[0080] The coating material refers to the material state before the coating layer treatment. If the coating material is methyl methacrylate, the final coating layer is polymethyl methacrylate; if the coating material is sodium maleate and oleic acid diethanolamide borate, the coating layer is sodium maleate and oleic acid diethanolamide borate. Therefore, in the following text, sodium maleate and oleic acid diethanolamide borate can be referred to as coating material or coating layer, but methyl methacrylate cannot be referred to as coating layer, nor can polymethyl methacrylate be referred to as coating material.

[0081] In the above scheme, after mixing and processing the negative electrode active material 1221 and the coating material, a negative electrode active material 122 is obtained, comprising the negative electrode active material 1221 and a coating layer 1222 covering the surface of the negative electrode active material 1221; wherein, the coating material includes at least one of methyl methacrylate, sodium maleate, and oleic diethanolamide borate. The negative electrode active material 122 prepared by this method can enable the battery including the negative electrode active material 122 to have better cycle performance and first-cycle coulombic efficiency.

[0082] In some embodiments, the thickness of the coating layer 1222 is 5nm-50nm, and optionally, the thickness of the coating layer 1222 is 10nm-20nm.

[0083] In the above scheme, by making the thickness of the coating layer 1222 5nm-50nm, especially 10nm-20nm, it helps to further improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0084] In some embodiments, methyl methacrylate is polymerized to form a coating layer 1222, the coating layer 1222 comprising polymethyl methacrylate; wherein the molecular weight of the polymethyl methacrylate is 500,000-2,000,000, optionally, the molecular weight of the polymethyl methacrylate is 1,000,000-1,500,000.

[0085] The polymerization here refers to the polymerization reaction, which is the process of converting low molecular weight monomers into high molecular weight polymers.

[0086] In addition, before the process of polymerizing methyl methacrylate to form polymethyl methacrylate, methyl methacrylate can be directly mixed with the negative electrode active material 1221, so that the negative electrode active material 122 with the coating layer 1222 can be directly formed.

[0087] In the above scheme, by polymerizing methyl methacrylate to form a coating layer 1222, a negative electrode active material 122 comprising a negative electrode active substance 1221 and a coating layer 1222 is formed. This preparation method is simple and uses abundant raw materials, which is conducive to its widespread application in industrial production. In addition, using polymethyl methacrylate with a molecular weight of 500,000-2,000,000 and a high degree of polymerization as the coating layer 1222 of the negative electrode active substance 1221 is conducive to the coating layer 1222 fully exerting its function.

[0088] In some embodiments, the mass ratio of methyl methacrylate to negative electrode active material 1221 is 1-5, and optionally, the mass ratio of methyl methacrylate to negative electrode active material 1221 is 1.5-3.

[0089] In the above scheme, the different mass ratios of methyl methacrylate to the negative electrode active material 1221 directly affect the thickness of the coating layer 1222. Therefore, by making the mass ratio of methyl methacrylate to the negative electrode active material 1221 1-5, especially 1.5-3, the coating layer 1222 can have a more reasonable thickness, thereby maximizing the effect of the coating layer 1222.

[0090] It should be noted that the mass ratio of methyl methacrylate to the negative electrode active material 1221 can be 1.5, 2.8, 4.2, 5, or any value within the above range.

[0091] In some embodiments, the treatment temperature of the negative electrode active material 1221 and methyl methacrylate is not lower than 60°C, and optionally, the treatment temperature is 60°C-220°C.

[0092] In the above scheme, methyl methacrylate (MMA) polymerizes to form polymethyl methacrylate (PMMA), which then acts as a coating layer 1222 to coat the negative electrode active material 1221. If the processing temperature is too low, the MMA may fail to polymerize; if the processing temperature is too high, it will affect the relative molecular mass of the MMA and reduce its performance. Therefore, by maintaining the processing temperature of the negative electrode active material 1221 and MMA at no less than 60°C, particularly between 60°C and 220°C, the resulting MMA exhibits better performance, which helps to further improve battery performance.

[0093] It should be noted that the above processing temperature can be 60℃, 100℃, 150℃, 170℃, or any value within the above range.

[0094] In some embodiments, the treatment time for the negative electrode active material 1221 and methyl methacrylate is 1h-8h, and optionally, the treatment time is 3h-5h.

[0095] In the above scheme, by maintaining the treatment time of negative electrode active material 1221 and methyl methacrylate at 1h-8h, especially at 3h-5h, better polymethyl methacrylate can be formed.

[0096] It should be noted that the processing time can be 1.5h, 3h, 5h, 8h, or any value within the above range.

[0097] In some embodiments, the catalyst, negative electrode active material 1221, and methyl methacrylate are used; optionally, the catalyst includes at least one of organic peroxides and azo compounds.

[0098] A catalyst is generally a substance that increases the rate of a reaction without changing the overall standard Gibbs free energy change. It can also be described as a substance that can increase the rate of a chemical reaction without changing the chemical equilibrium, and whose mass and chemical properties remain unchanged before and after the chemical reaction.

[0099] Organic peroxides are organic compounds containing -OO-peroxy functional groups formed by replacing hydrogen atoms in hydrogen peroxide with organic groups such as alkyl, acyl, and aromatic groups. These include, but are not limited to, benzoic acid peroxide and methyl ethyl ketone peroxide.

[0100] Azo compounds are compounds formed by attaching an azo group (─N=N─) to two hydrocarbon groups, with the general formula R─N=N─R, such as azobisisobutyronitrile.

[0101] In the above scheme, a catalyst is added to the reaction between methyl methacrylate and the negative electrode active material 1221. The catalyst can lower the activation energy of the polymerization reaction and accelerate the polymerization process. Therefore, by adding a catalyst during the polymerization of polymethyl methacrylate, and the catalyst can be at least one of organic peroxides and azo compounds, the formation of polymethyl methacrylate can be accelerated.

[0102] In some embodiments, the coating material includes at least one of sodium maleate and oleic acid diethanolamide borate; the processing temperature of the negative electrode active material 1221 and at least one of sodium maleate and oleic acid diethanolamide borate is not lower than 40°C, and optionally, the processing temperature is 40°C-120°C.

[0103] In the above scheme, by mixing the negative electrode active material 1221 with sodium maleate or oleic acid diethanolamide borate, a negative electrode active material 122 including the negative electrode active material 1221 and the coating layer 1222 can be obtained. Keeping the processing temperature of both at no less than 40°C, especially 40°C-120°C, can prevent the activity of the coating layer 1222 from being destroyed, thereby improving the performance of the battery.

[0104] It should be noted that the above processing temperature can be 45℃, 60℃, 80℃, 100℃, or any value within the above range.

[0105] In some embodiments, the mass ratio of at least one of sodium maleate and oleic acid diethanolamide borate to the negative electrode active material 1221 is 1-3. Optionally, the mass ratio of at least one of sodium maleate and oleic acid diethanolamide borate to the negative electrode active material 1221 is 1-2.

[0106] In the above scheme, when at least one of sodium maleate and oleic acid diethanolamide borate is used as the coating layer 1222 to coat the negative electrode active material 1221, the two can simply be mixed directly at a certain temperature. By making the mass ratio of at least one of sodium maleate and oleic acid diethanolamide borate to the negative electrode active material 1221 1-3, especially 1-2, the coating layer 1222 can have a suitable thickness to improve the battery performance.

[0107] It should be noted that the mass ratio of at least one of sodium maleate and oleic acid diethanolamide borate to the negative electrode active material 1221 can be 1.2, 1.5, 2, 3, or any value within the above range.

[0108] In some embodiments, the negative electrode active material 1221 includes at least one of graphite and silicon-based materials; optionally, the silicon-based material includes Si. a O b Si c C d At least one of the following, wherein a = 1, 1 ≤ b ≤ 2, c = 1, d = 1, and optionally, the silicon-based material includes Si@SiO2@C.

[0109] It should be noted here that if graphite is used as the negative electrode active material 1221, it can be fresh graphite or waste graphite, that is, used graphite.

[0110] Typically, a battery cell includes a positive electrode, a separator, a negative electrode, and an electrolyte. 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, while the separator, positioned between them, primarily prevents short circuits while allowing ions to pass through.

[0111] It should be noted that the "positive electrode sheet" and "negative electrode sheet" mentioned in the embodiments of this application refer to the whole positive electrode sheet and negative electrode sheet including active materials, current collectors or other additives.

[0112] [Negative electrode plate]

[0113] 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 122.

[0114] 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.

[0115] 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 (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.), or a current collector that combines supporting capacity and functional elements, such as carbon cloth, carbon film, carbonaceous material, porous current collector, alloy-modified current collector, and lithium-philic modified current collector.

[0116] In some embodiments, the negative electrode sheet can be a rolled metal foil or a metal powder coated with an inert layer on the surface and applied to the current collector; it can be a negative electrode with a functional coating, such as a carbon material coating (including single-arm, multi-arm conductive carbon nanotubes, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, soft carbon and hard carbon, etc.), a lithium-philic / sodium-philic metal composite coating, etc.

[0117] In some embodiments, the negative electrode is an alkali metal negative electrode. This alkali metal negative electrode can be formed by pre-depositing an alkali metal layer on the surface of the current collector, or it can be a negative current collector on which an alkali metal layer is generated during charging and discharging. This application does not limit this specific embodiment.

[0118] In some embodiments, the negative electrode active material 1221 in the negative electrode active material 122 may also employ negative electrode active materials known in the art for use in batteries. As an example, the negative electrode active material 1221 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. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material 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 in batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0119] 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), and carboxymethyl chitosan (CMCS).

[0120] 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.

[0121] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0122] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material 122, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0123] [Positive electrode plate]

[0124] 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 a positive electrode active material.

[0125] 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.

[0126] 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 (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0127] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. 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, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] [Electrolytes]

[0132] 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. For example, the electrolyte can be liquid, gel, or entirely solid.

[0133] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0138] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0139] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0140] Figure 5 This is a schematic diagram of the structure of a battery cell according to another embodiment of this application. Figure 5 As shown, the outer packaging of the battery cell 100 includes a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 12 through a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The battery cell 100 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to specific practical needs.

[0141] In some embodiments, the battery cells 100 can also be assembled into a battery module. The number of battery cells 100 contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0142] Figure 6 This is a schematic diagram of a battery according to one embodiment of this application. Figure 7 This is a schematic diagram of the battery structure according to one embodiment of this application. (Refer to...) Figure 6 and Figure 7 The battery 400 may include a battery box and a plurality of battery cells 100 disposed within the battery box. The battery box includes an upper box 401 and a lower box 402, the upper box 401 covering the lower box 402 to form a closed space for accommodating the battery cells 100. The plurality of battery cells 100 may be arranged in any manner within the battery box.

[0143] In addition, this application also provides an electrical device, which includes at least one of the battery cell 100 or battery 400 provided in this application. The battery cell 100 or battery 400 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 (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0144] For example, Figure 8 This is a schematic diagram of the structure of an electrical device according to one embodiment of this application. Figure 8 As shown, the electrical device is vehicle 1, which can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A motor 500, a controller 600, and a battery 400 can be installed inside vehicle 1. The controller 600 controls the battery 400 to supply power to the motor 500. For example, the battery 400 can be installed at the bottom, front, or rear of vehicle 1. The battery 400 can be used to power vehicle 1; for example, it can serve as the operating power source for vehicle 1's electrical system, such as meeting the power requirements for starting, navigation, and operation. In another embodiment of this application, the battery 400 can not only serve as the operating power source for vehicle 1 but also as the driving power source, replacing or partially replacing gasoline or natural gas to provide driving power to vehicle 1.

[0145] As the electrical device, either battery cell 100 or battery 400 can be selected according to its usage requirements.

[0146] The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the battery for this electrical device, a 100-cell battery or a 400-cell battery can be used.

[0147] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell (100) as their power source.

[0148] [Example]

[0149] 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.

[0150] [Example 1]

[0151] 1) Preparation of lithium-ion batteries

[0152] 1.11) Preparation of negative electrode active material: Methyl methacrylate (MMA) and graphite, the coating material, were weighed at a mass ratio of 3:1 and dispersed in 45 mL of deionized water. Benzoic acid peroxide was added as a catalyst and ultrasonically emulsified for 10 min to obtain a mixture of negative electrode active materials. The mixture of negative electrode active materials was then poured into a three-necked flask and polymerized at 80 °C under an argon (Ar) atmosphere for 4 h to obtain the negative electrode active material, wherein the negative electrode active material is artificial graphite and the coating layer is polymethyl methacrylate (PMMA).

[0153] 1.12) Preparation of negative electrode sheet: The negative electrode active material, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in an appropriate amount of deionized water solvent system at a weight ratio of 97.5%:0.7%:1.8%:1% to obtain the negative electrode active material. The negative electrode active material is coated on Cu foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0154] 1.2) Preparation of the positive electrode sheet: The positive electrode active material lithium iron phosphate (LiFePO4), the conductive agent carbon nanotubes (CNTs), and the binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone (NMP) at a weight ratio of 96%:2%:2%. After thorough mixing, the positive electrode active material was prepared. The positive electrode active material was coated onto Al foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0155] 1.3) Preparation of the diaphragm: PE porous polymer film was used as the diaphragm.

[0156] 1.4) Electrolyte: Dissolve EC / EMC / DMC in 1M LiPF6 at a volume ratio of 1:1:1 and stir until homogeneous.

[0157] 1.5) Assembly: Stack the positive electrode, separator, and negative electrode in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Wind the electrodes to obtain the electrode assembly and add electrolyte. Then, hot-press at 100℃ and 250MPa for 2 minutes to obtain the lithium-ion battery.

[0158] In the lithium-ion battery of Example 1, the coating material is methyl methacrylate, the coating layer is polymethyl methacrylate, the coating layer thickness is 20 nm, the mass ratio of the coating material to the negative electrode active material is 3, the treatment time is 4 h, the treatment temperature is 80 °C, the molecular weight of the coating layer is 1,530,000, and the catalyst is benzoic acid peroxide.

[0159] [Example 2]

[0160] The lithium-ion battery in Example 2 is basically the same as the lithium-ion battery in Example 1. The difference is that in the lithium-ion battery of Example 2, the mass ratio of the coating material to the negative electrode active material is 1, and the coating layer thickness is 5 nm.

[0161] [Example 3]

[0162] The lithium-ion battery in Example 3 is basically the same as the lithium-ion battery in Example 1. The difference is that in the lithium-ion battery of Example 3, the mass ratio of the coating material to the negative electrode active material is 5, and the coating layer thickness is 50 nm.

[0163] [Example 4]

[0164] The lithium-ion battery in Example 4 is basically the same as the lithium-ion battery in Example 1, except that in the lithium-ion battery of Example 4, the mass ratio of the coating material to the negative electrode active material is 1.5, and the coating thickness is 10 nm.

[0165] [Example 5]

[0166] The lithium-ion battery of Example 5 is basically the same as the lithium-ion battery of Example 1, except that in the lithium-ion battery of Example 5, the mass ratio of the coating material to the negative electrode active material is 4, and the coating layer thickness is 30 nm.

[0167] [Example 6]

[0168] The lithium-ion battery in Example 6 is basically the same as the lithium-ion battery in Example 1, except that the processing time in the lithium-ion battery in Example 6 is 1 hour and the coating thickness is 2 nm.

[0169] [Example 7]

[0170] The lithium-ion battery in Example 7 is basically the same as the lithium-ion battery in Example 1, except that the processing time in the lithium-ion battery in Example 7 is 8 hours and the coating thickness is 60 nm.

[0171] [Example 8]

[0172] The lithium-ion battery of Example 8 is basically the same as the lithium-ion battery of Example 1, except that the processing time in the lithium-ion battery of Example 8 is 3 hours and the coating thickness is 12 nm.

[0173] [Example 9]

[0174] The lithium-ion battery of Example 9 is basically the same as the lithium-ion battery of Example 1, except that the processing time in the lithium-ion battery of Example 9 is 5 hours and the coating thickness is 45 nm.

[0175] [Example 10]

[0176] The lithium-ion battery of Example 10 is basically the same as the lithium-ion battery of Example 1, except that the processing temperature in the lithium-ion battery of Example 10 is 60°C and the coating thickness is 11nm.

[0177] [Example 11]

[0178] The lithium-ion battery of Example 11 is basically the same as the lithium-ion battery of Example 1, except that in the lithium-ion battery of Example 11, the coating material is sodium maleate, which is directly mixed with the negative electrode active material to obtain a negative electrode active material with sodium maleate as the coating layer; wherein, the coating layer thickness is 28nm, the mass ratio of coating material to negative electrode active material is 4.5, and the processing temperature is 60°C.

[0179] [Example 12]

[0180] The lithium-ion battery of Example 12 is basically the same as the lithium-ion battery of Example 11, except that the coating thickness of the lithium-ion battery of Example 12 is 13 nm and the mass ratio of the coating material to the negative electrode active material is 2.5.

[0181] [Example 13]

[0182] The lithium-ion battery of Example 13 is basically the same as the lithium-ion battery of Example 11, except that the coating thickness of the lithium-ion battery of Example 13 is 10 nm and the mass ratio of the coating material to the negative electrode active material is 2.

[0183] [Example 14]

[0184] The lithium-ion battery of Example 14 is basically the same as the lithium-ion battery of Example 11, except that the coating thickness of the lithium-ion battery of Example 14 is 5 nm and the mass ratio of the coating material to the negative electrode active material is 1.

[0185] [Example 15]

[0186] The lithium-ion battery of Example 15 is basically the same as the lithium-ion battery of Example 1, except that in the lithium-ion battery of Example 15, the coating material is oleic acid diethanolamide borate, which is directly mixed with the negative electrode active material to obtain a negative electrode active material with oleic acid diethanolamide borate as the coating layer; wherein, the coating layer thickness is 10 nm, the mass ratio of coating material to negative electrode active material is 1, and the processing temperature is 40 °C.

[0187] [Example 16]

[0188] The lithium-ion battery of Example 16 is basically the same as the lithium-ion battery of Example 1, except that the catalyst in the lithium-ion battery of Example 16 is peroxy ketal.

[0189] [Example 17]

[0190] The lithium-ion battery of Example 17 is basically the same as the lithium-ion battery of Example 1, except that the negative electrode active material in the lithium-ion battery of Example 17 is SiO2@Si@C.

[0191] [Comparative Example 1]

[0192] The lithium-ion battery of Comparative Example 1 is basically the same as the lithium-ion battery in Example 1, except that in the lithium-ion battery of Comparative Example 1, the negative electrode active material only includes the negative electrode active material, namely graphite.

[0193] [Comparative Example 2]

[0194] The lithium-ion battery in Comparative Example 2 is basically the same as the lithium-ion battery in Example 1, except that the negative electrode active material in the lithium-ion battery in Comparative Example 2 only includes SiO2-Si-C negative electrode active material.

[0195] [Comparative Example 3]

[0196] The lithium-ion battery of Comparative Example 3 is basically the same as the lithium-ion battery in Example 1, except that the coating layer in the lithium-ion battery of Comparative Example 3 is aluminum oxide (Al2O3).

[0197] [Comparative Example 4]

[0198] The lithium-ion battery of Comparative Example 4 is basically the same as the lithium-ion battery in Example 1, except that the coating layer in the lithium-ion battery of Comparative Example 4 is a 3(3-nitrophenyl)acrylonitrile / olefin sulfonic acid copolymer.

[0199] 2) Physical characterization of negative electrode active materials

[0200] 2.1) Coating thickness measurement: It can be directly observed and measured by scanning electron microscopy (SEM) or transmission electron microscopy (TEM).

[0201] 2.2) Molecular weight measurement: It can be measured directly using a light scattering detector.

[0202] Table 1. Specific experimental parameters for Examples 1-17 and Comparative Examples 1-4

[0203]

[0204]

[0205] 3) Performance Characterization of Lithium-ion Batteries

[0206] 3.1) Capacity retention test: The battery was charged and discharged using the Blue Electric test system.

[0207] Under 45℃ conditions, the battery charge and discharge voltage range was maintained at 2.5-3.65V, and the battery was cycled at a current density of 1C. The battery capacity retention rate was recorded after 1000 cycles. The test results are shown in Table 2.

[0208] 3.2) Measurement of first-cycle coulombic efficiency: The battery was charged and discharged using the Blue Electric test system.

[0209] Under conditions of 45℃, the battery charge / discharge voltage range was maintained at 2.5-3.65V, and the battery was cycled at a current density of 1C. The charge / discharge capacity of the battery was recorded at the third cycle, and the capacity ratio of discharge to charge was calculated. The test results are shown in Table 2. (It should be noted that the first cycle of the battery is the formation stage, and the third cycle is more stable than the second cycle. Therefore, the third cycle was selected as the first cycle in the actual sense of this application.)

[0210] Table 2 Performance parameters of Examples 1-17 and Comparative Examples 1-4

[0211] Group First lap Coulomb efficiency Capacity retention Example 1 91.3％ 92.3％ Example 2 84.0％ 88.2％ Example 3 83.5％ 87.5％ Example 4 89.8％ 91.5％ Example 5 88.1％ 91.0％ Example 6 82.4％ 88.0％ Example 7 82.1％ 85.3％ Example 8 90.1％ 90.8％ Example 9 84.0％ 87.9％ Example 10 89.7％ 91.3％ Example 11 85.6％ 86.7％ Example 12 88.7％ 88.5％ Example 13 90％ 90.3％ Example 14 83％ 84.2％ Example 15 86.1％ 86.1％ Example 16 91.3％ 92.3％ Example 17 78％ 77％ Comparative Example 1 80％ 81％ Comparative Example 2 74％ 70％ Comparative Example 3 82％ 83.20％ Comparative Example 4 83.0％ 82.60％

[0212] In this application, the capacity retention rate is used to characterize the cycle performance of the battery. The higher the capacity retention rate, the higher the capacity is retained after the battery has cycled to a specific number of times, which means that the battery has better cycle performance.

[0213] As can be seen from Examples 1-17 and Comparative Examples 1-4, coating the surface of the negative electrode active material with at least one of polymethyl methacrylate, sodium maleate, and oleic diethanolamide borate can improve the first-cycle coulombic efficiency and cycle performance of the battery.

[0214] As can be seen from Examples 1-10, by making the thickness of the coating layer 5nm-50nm, the first-cycle coulombic efficiency and cycle performance of the battery can be improved; furthermore, making the thickness of the coating layer 10nm-20nm helps to further improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0215] As can be seen from Examples 1-10, when the coating layer is polymethyl methacrylate, making the molecular weight of the coating layer 500,000-2,000,000, especially 1,000,000-1,500,000, helps to further improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0216] As can be seen from Examples 1-5, when the coating material is methyl methacrylate and the formed coating layer is polymethyl methacrylate, and the mass ratio of methyl methacrylate to the negative electrode active material is 1-5, especially 1.5-3, the coating layer can have a more suitable thickness, which helps to further improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0217] As can be seen from Examples 6-10, when the coating material is methyl methacrylate and the formed coating layer is polymethyl methacrylate, the processing time is 1h-8h, especially 3h-5h, which helps to further improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0218] As can be seen from Examples 1 and 10, when the coating material is methyl methacrylate and the formed coating layer is polymethyl methacrylate, keeping the processing temperature at no less than 60°C can further improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0219] As shown in Examples 1, 11-14 and 15, coating the surface of the negative electrode active material with polymethyl methacrylate, sodium maleate or oleic acid diethanolamide borate can improve the performance of the battery.

[0220] As can be seen from Examples 11-14, when the coating layer is sodium maleate, making the mass ratio of sodium maleate to the negative electrode active material 1-3, especially 1.5-2, can improve the cycle performance and first-cycle coulombic efficiency of the battery.

[0221] As can be seen from Examples 1 and 16, a variety of catalysts are applicable to the technical solutions of this application.

[0222] As can be seen from Examples 1 and 17, a variety of negative electrode active materials are applicable to the technical solutions of this application.

[0223] 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, include: A negative electrode active material and a coating layer, wherein the coating layer is coated on the surface of the negative electrode active material, and the coating layer comprises at least one of polymethyl methacrylate, sodium maleate and oleic acid diethanolamide borate; The thickness of the coating layer is 5nm-50nm.

2. The negative electrode active material according to claim 1, characterized in that, The thickness of the coating layer is 10nm-20nm.

3. The negative electrode active material according to claim 1 or 2, characterized in that, The molecular weight of the polymethyl methacrylate is 500,000-2,000,000.

4. The negative electrode active material according to any one of claims 1 to 3, characterized in that, The molecular weight of the polymethyl methacrylate is 1,000,000-1,500,000.

5. The negative electrode active material according to any one of claims 1 to 4, characterized in that, The negative electrode active material includes at least one of graphite and silicon-based materials.

6. The negative electrode active material according to claim 5, characterized in that, The silicon-based material includes at least one of elemental silicon, silicon oxide compounds, silicon carbide compounds, and composites of elemental silicon, silicon oxide compounds, and silicon carbide compounds.

7. The negative electrode active material according to claim 6, characterized in that, The silicon oxide compound includes Si a O b Where a=1, 1≤b≤2; The silicon-carbon compound includes Si c C d , where c=1, d=1.

8. A method for preparing a negative electrode active material, characterized in that, include: Provides negative electrode active material and coating material; The negative electrode active material and the coating material are mixed and processed to obtain the negative electrode active material and the coating layer covering the surface of the negative electrode active material. The coating material includes at least one of methyl methacrylate, sodium maleate, and oleic acid diethanolamide borate. The thickness of the coating layer is 5nm-50nm.

9. The preparation method according to claim 8, characterized in that, include: The thickness of the coating layer is 10nm-20nm.

10. The preparation method according to claim 8 or 9, characterized in that, The process of mixing the negative electrode active material and the coating material includes: The methyl methacrylate is polymerized to form the coating layer, and the coating layer includes polymethyl methacrylate; The molecular weight of the polymethyl methacrylate is 500,000-2,000,000.

11. The preparation method according to claim 10, characterized in that, The molecular weight of the polymethyl methacrylate is 1,000,000-1,500,000.

12. The preparation method according to claim 10 or 11, characterized in that, The mass ratio of methyl methacrylate to the negative electrode active material is 1-5.

13. The preparation method according to any one of claims 10 to 12, characterized in that, The mass ratio of methyl methacrylate to the negative electrode active material is 1.5-3.

14. The preparation method according to any one of claims 10 to 13, characterized in that, The processing temperature of the negative electrode active material and the methyl methacrylate is not lower than 60°C.

15. The preparation method according to claim 14, characterized in that, The processing temperature is 60℃-220℃.

16. The preparation method according to any one of claims 10 to 15, characterized in that, The treatment time for the negative electrode active material and the methyl methacrylate is 1h-8h.

17. The preparation method according to claim 16, characterized in that, The processing time is 3-5 hours.

18. The preparation method according to any one of claims 8 to 17, characterized in that, The negative electrode active material and the coating material are mixed and processed, including: The catalyst, the negative electrode active material, and the methyl methacrylate are mixed.

19. The preparation method according to claim 18, characterized in that, The catalyst includes at least one of organic peroxides and azo compounds.

20. The preparation method according to claim 8, characterized in that, The negative electrode active material and the coating material are mixed and processed, including: The coating material includes at least one of sodium maleate and oleic acid diethanolamide borate. The processing temperature of the negative electrode active material and at least one of sodium maleate and oleic acid diethanolamide borate is not lower than 40°C.

21. The preparation method according to claim 20, characterized in that, The processing temperature is 40℃-120℃.

22. The preparation method according to claim 20 or 21, characterized in that, The mass ratio of at least one of sodium maleate and oleic acid diethanolamide borate to the negative electrode active material is 1-3.

23. The preparation method according to any one of claims 20 to 22, characterized in that, The mass ratio of at least one of sodium maleate and oleic acid diethanolamide borate to the negative electrode active material is 1-2.

24. The preparation method according to any one of claims 8 to 23, characterized in that, The negative electrode active material includes at least one of graphite and silicon-based materials.

25. The preparation method according to claim 24, characterized in that, The silicon-based material includes at least one of elemental silicon, silicon oxide, silicon carbide, silicon nitride complex, and a complex of elemental silicon, silicon oxide, and silicon carbide.

26. The preparation method according to claim 25, characterized in that, The silicon oxide compound includes Si a O b Where a=1, 1≤b≤2; The silicon-carbon compound includes Si c C d , where c=1, d=1.

27. A negative electrode sheet, characterized in that, The negative electrode active material includes any one of claims 1 to 7, and / or the negative electrode active material prepared by the method of any one of claims 8 to 26.

28. A single battery cell, characterized in that, Includes the negative electrode sheet as described in claim 27.

29. A battery, characterized in that, Includes the battery cell as described in claim 28.

30. An electrical device, characterized in that, Includes the battery as described in claim 29.

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