Negative active material, method for preparing the same, secondary battery, and electric device

Abstract

A negative electrode active material, a preparation method thereof, a secondary battery, and an electric device. The negative electrode active material comprises a silicon-carbon composite material, X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has a Si2p peak, the Si2p peak can form the following sub-peaks after peak separation processing: a first sub-peak with a binding energy of 99.7±0.2 eV; and a second sub-peak with a binding energy of 98.9±0.2 eV; and the peak area ratio of the first sub-peak to the second sub-peak is 1-2:1.

Description

Technical Field

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

[0002] In recent years, with the increasingly wide application of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant development of secondary batteries, higher requirements have been placed on their energy density and cycle performance.

[0003] Silicon-based anode materials are considered to be highly promising next-generation high-energy-density lithium-ion battery anode materials due to their advantages such as high theoretical specific capacity, low delithiation potential, environmental friendliness, abundant reserves, and low cost.

[0004] To further improve battery performance, existing technologies require superior negative electrode active materials. Summary of the Invention

[0005] In view of the above-mentioned issues, this application provides a novel negative electrode active material and its preparation method, a secondary battery and an electrical device, which are described below.

[0006] In a first aspect, this application provides a negative electrode active material, comprising a silicon-carbon composite material, wherein the X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has a Si2p spectrum, the Si2p spectrum having at least one characteristic peak, and the characteristic peak, after peak splitting, can form the following subpeaks, including:

[0007] The first subpeak has a binding energy of 99.5–99.9 eV; and

[0008] The second subpeak has a binding energy of 98.7–99.1 eV;

[0009] The ratio of the peak area of ​​the first subpeak to that of the second subpeak is 1 to 2:1.

[0010] The negative electrode active material described above exhibits high specific capacity and long cycle life. The peak area ratio of the first subpeak to the second subpeak (1–2:1) is crucial. If the ratio is <1, it indicates a high pure silicon content and large silicon grains in the negative electrode active material, which is detrimental to cycle life. If the ratio is >2, it indicates excessive carbon content in the negative electrode active material, resulting in low specific capacity and poor initial efficiency.

[0011] In some embodiments, the above-mentioned negative electrode active material has one or more of the following characteristics:

[0012] (1) The binding energy of the first subpeak corresponds to the binding energy of the Si-C bond;

[0013] (2) The second subpeak is the binding energy corresponding to the Si-Si bond;

[0014] (3) The binding energy of the first subpeak is 99.6–99.8 eV, for example 99.7 eV;

[0015] (4) The binding energy of the second subpeak is 98.8–99.0 eV, for example 98.9 eV;

[0016] (5) The ratio of the peak area of ​​the first subpeak to the second subpeak is 1.5 to 2:1, for example 1.6 to 1.8:1, for example 1.7:1.

[0017] (6) The silicon content in the silicon-carbon composite material is 95wt% to 99.9wt% (e.g., 95wt%, 96wt%, 97wt%, 98wt%, 99wt% or 99.5wt%), and the carbon content is 0.1wt% to 5wt% (e.g., 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%).

[0018] In some embodiments, the negative electrode active material includes a matrix and the silicon-carbon composite material, the silicon-carbon composite material being attached to the matrix.

[0019] In some embodiments, the matrix has a porous internal structure, and the silicon-carbon composite material is attached to the matrix at the following locations:

[0020] The outer surface of the substrate; and / or

[0021] The porous internal structure contains pores.

[0022] In some embodiments, the substrate is made of one or more of the following: carbon materials, silicon oxide materials, lithium titanate materials, or combinations thereof.

[0023] In some embodiments, the negative electrode active material further includes a carbon coating layer that covers the matrix and / or the silicon-carbon composite material.

[0024] In some embodiments, the carbon material includes one or more of the following: graphite material, hard carbon material, soft carbon material, or a combination thereof.

[0025] In some embodiments, the silicon-carbon composite material contains silicon grains with a grain size of less than 20 nm.

[0026] In some embodiments, the volume median particle size D of the negative electrode active material V50 represents 1–10 μm.

[0027] In some implementations, the peak intensities of both the first and second subpeaks are <2000, for example, less than 1500.

[0028] In a second aspect, this application provides a method for preparing a negative electrode active material, comprising the following steps:

[0029] S1: Provide a substrate and vapor deposition equipment, wherein the substrate is placed in a deposition furnace and preheated to 200-300°C by purging with inert gas;

[0030] S2: Gas is introduced into the vapor deposition equipment in the first mode, the first mode including the simultaneous introduction of silicon source gas and carbon source gas into the vapor deposition equipment;

[0031] S3: React silicon source gas and carbon source gas and deposit the reaction products on the matrix to form a silicon-carbon composite material on the matrix;

[0032] The silicon-carbon composite material exhibits a Si2p peak in its X-ray photoelectron spectroscopy (XPS), and this Si2p peak, after peak splitting, can form the following subpeaks:

[0033] The first subpeak has a binding energy of 99.5–99.9 eV; and

[0034] The second subpeak has a binding energy of 98.7–99.1 eV;

[0035] The ratio of the peak area of ​​the first subpeak to that of the second subpeak is 1 to 2:1.

[0036] In some implementations, the first mode in step S2 includes simultaneously introducing silicon source gas, carbon source gas, and inert gas into the vapor deposition apparatus.

[0037] In some implementations, step S2 has one or more of the following features:

[0038] (1) The inert gas is one or more of nitrogen and argon.

[0039] (2) The flow rate of inert gas introduced into the vapor deposition equipment accounts for 30-85% of the total gas flow rate.

[0040] In some embodiments, in step S2, gas is introduced into the vapor deposition apparatus according to the first mode, and the gas pressure inside the apparatus is maintained at 200-600 Pa higher than the standard atmospheric pressure.

[0041] In some implementations, step S3 has one or more of the following features:

[0042] (1) Step S3 is carried out at 400-800℃;

[0043] (2) Step S3 lasts for 1 to 12 hours.

[0044] In some implementations, step S3 is followed by step S4:

[0045] S4: Deposit carbon material on the product of step S3.

[0046] In some implementations, step S4 includes the following operations:

[0047] S4a: After forming the silicon-carbon composite material, gas is introduced into the vapor deposition equipment in the second mode. The second mode includes simultaneously introducing carbon source gas and inert gas into the vapor deposition equipment. The carbon source gas accounts for 5% to 15%, and the inert gas accounts for 85% to 95%.

[0048] S4b: Decomposes the carbon source gas into carbon materials and deposits them on the silicon-carbon composite material.

[0049] In some implementations, operation S4b has one or more of the following characteristics:

[0050] (1) Step S4b is performed at 700–850°C;

[0051] (2) Step S4b lasts for 1-6 hours.

[0052] In a third aspect, this application provides a negative electrode active material prepared by the method described in any of the above-mentioned methods.

[0053] In a fourth aspect, this application provides a secondary battery comprising the negative electrode active material described in any of the preceding claims.

[0054] In a fifth aspect, this application provides an electrical device including the aforementioned secondary battery.

[0055] Beneficial effects

[0056] One or more embodiments of this application have one or more of the following beneficial effects:

[0057] (1) The negative electrode active material has a high specific capacity;

[0058] (2) The negative electrode active material has a long cycle life;

[0059] (3) The preparation method of the negative electrode active material has a low cost;

[0060] (4) The preparation method of negative electrode active material has high efficiency. Attached Figure Description

[0061] Figure 1 These are XPS spectra of the negative electrode active materials of some embodiments and comparative examples of this application.

[0062] Figure 2 These are XRD spectra of the negative electrode active materials of some embodiments and comparative examples of this application.

[0063] Figure 3 These are the first-cycle charge-discharge curves of coin cells in some embodiments and comparative examples of this application.

[0064] Figure 4 These are capacity retention-cycle count curves for full cells in some embodiments and comparative examples of this application.

[0065] Figure 5 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0066] Figure 6 yes Figure 5 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0067] Figure 7 This is a schematic diagram of a battery module according to one embodiment of this application.

[0068] Figure 8 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0069] Figure 9 yes Figure 8 An exploded view of a battery pack according to one embodiment of this application is shown.

[0070] Figure 10 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.

[0071] Explanation of reference numerals in the attached figures:

[0072] 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly; 11 Positive current collector; 112 Surface; 12 Conductive undercoating; 13 Positive film layer; Detailed Implementation

[0073] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the negative electrode active material and its manufacturing method, positive electrode sheet, negative electrode sheet, secondary battery, battery module, battery pack, and 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 to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0074] 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.

[0075] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0076] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0077] 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.

[0078] 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.

[0079] 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).

[0080] [Rechargeable Battery]

[0081] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after being discharged to activate the active materials and continue to be used.

[0082] Typically, a secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through. The electrolyte, also positioned between the positive and negative electrodes, mainly serves to conduct active ions.

[0083] [Negative electrode plate]

[0084] 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, the negative electrode active material being any of the negative electrode active materials of this application.

[0085] 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.

[0086] 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.).

[0087] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, 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).

[0088] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, 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.

[0089] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0090] 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 (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.

[0091] [Negative Electrode Active Materials]

[0092] In some embodiments, this application provides a negative electrode active material, including a silicon-carbon composite material, wherein the X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has a Si2p spectrum, the Si2p spectrum has at least one characteristic peak, and the characteristic peak, after peak splitting, can form the following subpeaks, including:

[0093] The first subpeak has a binding energy of 99.5–99.9 eV; and

[0094] The second subpeak has a binding energy of 98.7–99.1 eV;

[0095] The ratio of the peak area of ​​the first subpeak to that of the second subpeak is 1 to 2:1.

[0096] The negative electrode active material described above exhibits high specific capacity and long cycle life. The peak area ratio of the first subpeak to the second subpeak (1–2:1) is crucial. If the ratio is <1, it indicates a high pure silicon content and large silicon grains in the negative electrode active material, which is detrimental to cycle life. If the ratio is >2, it indicates excessive carbon content in the negative electrode active material, resulting in low specific capacity and poor initial efficiency.

[0097] In some implementations, the binding energy of the first subpeak refers to the binding energy corresponding to the peak point of the first subpeak.

[0098] In some implementations, the binding energy of the second subpeak refers to the binding energy corresponding to the peak point of the second subpeak.

[0099] In some implementations, the first and second subpeaks have symmetrical peak shapes, such as peaks conforming to a Gaussian function or a Lorentz function.

[0100] In some implementations, the binding energy of the first subpeak is 99.6–99.8 eV, for example, 99.7 eV.

[0101] In some implementations, the binding energy of the second subpeak is 98.8–99.0 eV, for example, 98.9 eV.

[0102] In some implementations, the peak area ratio of the first subpeak to the second subpeak is 1.5 to 2:1, for example 1.6 to 1.8:1, for example 1.7:1.

[0103] In some embodiments, the above-mentioned negative electrode active material has one or more of the following characteristics: (1) the binding energy of the first subpeak corresponds to the binding energy of the Si-C bond; (2) the binding energy of the second subpeak corresponds to the binding energy of the Si-Si bond. Based on this, the negative electrode active material has further improved specific capacity, first-efficiency and / or cycle life. (3) The binding energy of the first subpeak is 99.6 to 99.8 eV, for example 99.7 eV; (4) The binding energy of the second subpeak is 98.8 to 99.0 eV, for example 98.9 eV; (5) The peak area ratio of the first subpeak to the second subpeak is 1.5 to 2:1; (6) The silicon content in the silicon-carbon composite material is 95 to 99.9 wt% (for example 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt% or 99.5 wt%), and the carbon content is 0.1 to 5 wt% (for example 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%).

[0104] Based on this, negative electrode active materials are used in secondary batteries, which exhibit further improved specific capacity, first-efficiency and / or cycle performance.

[0105] In some embodiments, the negative electrode active material comprises a matrix and the silicon-carbon composite material, the silicon-carbon composite material being attached to the matrix. Based on this, the negative electrode active material exhibits further improved specific capacity, first-efficiency, and / or cycle life.

[0106] In some embodiments, the matrix has a porous internal structure, and the silicon-carbon composite material is attached to the matrix at the following locations: the outer surface of the matrix; and / or the pores of the porous internal structure. Based on this, the negative electrode active material exhibits further improved specific capacity, first-efficiency, and / or cycle life.

[0107] In some embodiments, the substrate material includes one or more of the following: carbon materials, silicon-oxygen materials, lithium titanate materials, or combinations thereof. Based on this, the negative electrode active material exhibits further improved specific capacity, first-efficiency, and / or cycle life.

[0108] In some embodiments, the negative electrode active material further includes a carbon coating layer that covers the matrix and / or the silicon-carbon composite material. Based on this, the negative electrode active material exhibits further improved specific capacity, first-efficiency, and / or cycle life.

[0109] In some embodiments, the carbon material includes one or more of the following: graphite materials, hard carbon materials, soft carbon materials, or combinations thereof. Based on this, the negative electrode active material has further improved specific capacity, first-efficiency, and / or cycle life.

[0110] In some embodiments, the silicon-carbon composite material contains silicon grains with a grain size of less than 20 nm. Based on this, the negative electrode active material exhibits further improved specific capacity, first-efficiency, and / or cycle life.

[0111] In some embodiments, the volume median particle size D of the negative electrode active material V 50 is 1–10 μm (e.g., 2 μm, 4 μm, 6 μm, or 8 μm). Based on this, the negative electrode active material has further improved specific capacity, first-efficiency and / or cycle life.

[0112] In some implementations, the peak intensities of both the first and second subpeaks are <2000, for example, less than 1500.

[0113] In some embodiments, this application provides a method for preparing a negative electrode active material, comprising the following steps:

[0114] S1: Provide a substrate and vapor deposition equipment, wherein the substrate is placed in a deposition furnace and preheated to 200-300°C by purging with inert gas;

[0115] S2: Gas is introduced into the vapor deposition equipment in the first mode, the first mode including the simultaneous introduction of silicon source gas and carbon source gas into the vapor deposition equipment;

[0116] S3: React silicon source gas and carbon source gas and deposit the reaction products on the matrix to form a silicon-carbon composite material on the matrix;

[0117] The silicon-carbon composite material exhibits a Si2p peak in its X-ray photoelectron spectroscopy (XPS), and this Si2p peak, after peak splitting, can form the following subpeaks:

[0118] The first subpeak has a binding energy of 99.5–99.9 eV; and

[0119] The second subpeak has a binding energy of 98.7–99.1 eV;

[0120] The ratio of the peak area of ​​the first subpeak to that of the second subpeak is 1 to 2:1.

[0121] The negative electrode active material obtained based on this scheme has improved specific capacity, first efficiency, and / or cycle life.

[0122] In some embodiments, the first mode in step S2 includes simultaneously introducing silicon source gas, carbon source gas, and inert gas into the vapor deposition apparatus. The negative electrode active material obtained based on this approach exhibits improved specific capacity, first-efficiency, and / or cycle life.

[0123] In some implementations, step S2 has one or more of the following features:

[0124] (1) The inert gas is one or more of nitrogen and argon;

[0125] (2) The flow rate of inert gas introduced into the vapor deposition equipment accounts for 30-85% of the total gas flow rate. The negative electrode active material obtained based on this scheme has improved specific capacity, first efficiency and / or cycle life.

[0126] In some embodiments, in step S2, gas is introduced into the vapor deposition apparatus according to the first mode, and the gas pressure inside the apparatus is maintained at 200–600 Pa (e.g., 300 Pa, 400 Pa, 500 Pa) above standard atmospheric pressure. The negative electrode active material obtained based on this scheme has improved specific capacity, first-efficiency and / or cycle life.

[0127] In some implementations, step S3 has one or more of the following features:

[0128] (1) Step S3 is performed at 400-800°C (e.g., 500°C, 600°C or 700°C);

[0129] (2) Step S3 lasts for 1 to 12 hours (e.g., 2 hours, 4 hours, 6 hours, 8 hours, or 10 hours). The negative electrode active material obtained based on this scheme has improved specific capacity, first efficiency, and / or cycle life.

[0130] In some implementations, step S3 is followed by step S4:

[0131] S4: Deposit carbon material onto the product of step S3. The negative electrode active material obtained based on this scheme has improved specific capacity, first efficiency, and / or cycle life.

[0132] In some implementations, step S4 includes the following operations:

[0133] S4a: After forming the silicon-carbon composite material, gas is introduced into the vapor deposition equipment in the second mode. The second mode includes simultaneously introducing carbon source gas and inert gas into the vapor deposition equipment. The carbon source gas accounts for 5% to 15%, and the inert gas accounts for 85% to 95%.

[0134] S4b: Decomposes the carbon source gas into carbon materials and deposits them on a silicon-carbon composite material. The negative electrode active material obtained based on this scheme has improved specific capacity, first efficiency, and / or cycle life.

[0135] In some implementations, operation S4b has one or more of the following characteristics:

[0136] (1) Step S4b is performed at 700–850°C (e.g., 750–800°C);

[0137] (2) Step S4b lasts for 1-6 hours (e.g., 2 hours, 3 hours, 4 hours, or 5 hours). The negative electrode active material obtained based on this scheme has improved specific capacity, first efficiency, and / or cycle life.

[0138] In some embodiments, this application provides a negative electrode active material prepared by the method described in any of the above-mentioned embodiments.

[0139] In some embodiments, this application provides a secondary battery comprising the negative electrode active material described in any of the above claims.

[0140] In some embodiments, this application provides an electrical device including the aforementioned secondary battery.

[0141] [Positive electrode plate]

[0142] In some embodiments, the positive electrode typically 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.

[0143] 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.

[0144] 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.).

[0145] 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 / 5 n 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At 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.

[0146] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0147] 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.

[0148] 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.

[0149] [Electrolytes]

[0150] 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.

[0151] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0152] 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.

[0153] 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.

[0154] In some embodiments, the electrolyte may optionally include additives. As examples, 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.

[0155] [Isolation membrane]

[0156] 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.

[0157] 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.

[0158] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0159] 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.

[0160] 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.

[0161] 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 5 This is an example of a square-structured secondary battery 5.

[0162] In some implementations, refer to Figure 6The 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.

[0163] 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.

[0164] Figure 7 This is battery module 4, used as an example. (See reference...) Figure 7 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.

[0165] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0166] 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.

[0167] Figure 8 and Figure 9 This is battery pack 1 as an example. (See reference...) Figure 8 and Figure 9 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.

[0168] 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 (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.

[0169] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0170] Figure 10 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.

[0171] 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.

[0172] Comparative Example 1

[0173] Commercially available silicon-oxygen materials are provided as the negative electrode active material for Comparative Example 1.

[0174] The composition of the silicon-oxygen material is as follows: Li 8wt%, Si 52wt%, O 35.8wt%, C 4.2wt%.

[0175] Example 1

[0176] S1: Provide the same silicon-oxygen material as Comparative Example 1 as the substrate. Provide a chemical vapor deposition (CVD) apparatus. Place 1 kg of substrate into the reaction chamber of the CVD apparatus. Purge the reaction chamber with nitrogen gas and heat the reaction chamber to 200°C.

[0177] S2: Introduce a mixed gas into the reaction chamber in the first mode. The first mode refers to introducing a mixed gas into the reaction chamber in a volume ratio of silane: acetylene: nitrogen = 20%: 5%: 75%, with a total gas flow rate of 5L / min, and controlling the pressure inside the reaction chamber to be 200Pa higher than atmospheric pressure.

[0178] S3: Raise the temperature inside the reaction chamber to 600℃ to react silane with acetylene and deposit the resulting reaction product (carbon-silicon composite material) onto the substrate. The deposition lasts for 4 hours.

[0179] S4: Introduce a mixed gas into the reaction chamber in the second mode. The second mode refers to introducing a mixed gas into the reaction chamber at a volume ratio of acetylene:nitrogen = 5%:95%.

[0180] S5: Raise the temperature inside the reaction chamber to 850℃ to decompose acetylene into carbon material and deposit it on the surface of the product from the previous step. The deposition lasts for 2 hours.

[0181] After the product cools, it is removed from the reaction chamber and sieved through a 325-mesh sieve. The negative electrode active material of Example 1 is obtained.

[0182] The negative electrode active material of Example 1 includes a substrate, a first coating layer deposited on the surface of the substrate, and a second coating layer deposited on the surface of the first coating layer. The substrate is made of silicon-oxygen material. The first coating layer is made of silicon-carbon composite material. The second coating layer is made of carbon material.

[0183] Examples 2-3

[0184] The difference between Example 2 and Example 1 is that in step S2: silane: acetylene: nitrogen = 20%: 7%: 73%.

[0185] The difference between Example 3 and Example 1 is that: Step S2: Adjust the ratio of silane: acetylene: nitrogen to 20%: 2%: 78%.

[0186] Comparative Examples 2-3

[0187] The difference between Comparative Example 2 and Example 1 is that in step S2: silane: acetylene: nitrogen = 20%: 10%: 70%.

[0188] The difference between Comparative Example 3 and Example 1 is that in step S2: silane: acetylene: nitrogen = 20%: 0.5%: 79.5%.

[0189] Preparation of button cells

[0190] The negative electrode active materials of Comparative Example 1 and Example 1 were used to assemble coin-type lithium-ion batteries, as detailed below:

[0191] A negative electrode active material, conductive carbon black, and binder polyacrylic acid were mixed at a mass ratio of 8:1:1, and deionized water was added as a solvent. The mixture was stirred until homogeneous, yielding a negative electrode slurry with a solid content of 45 wt%. The negative electrode slurry was uniformly coated onto a copper foil current collector and dried at 85°C. After cold pressing, the electrode sheet was obtained. Using lithium metal as the counter electrode, a Celgard 2400 separator was used, and electrolyte was injected to assemble a coin cell. The electrolyte solvent was a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with a volume ratio of EC:20:60. The solute in the electrolyte was LiPF6 at a concentration of 1 mol / L. The electrolyte also contained fluoroethylene carbonate (FEC) as an additive, with an FEC content of 5 wt%.

[0192] Analysis and testing

[0193] Powder performance testing:

[0194] 1) XPS detection

[0195] The negative electrode active materials of the examples and comparative examples were tested using X-ray photoelectron spectroscopy (Thermo Scientific ESCALAB Xi+) to obtain the Si2p energy spectra. The characteristic peaks of the Si2p energy spectra were then processed using XPSpeak software for peak fitting.

[0196] The Si2p energy spectrum of the negative electrode active material in Comparative Example 1 has a characteristic peak in the range of 100–104 eV, and the binding energy of this characteristic peak is 102.3 eV, which corresponds to the binding energy of the Si-OC bond.

[0197] Figure 1 The Si2p energy spectrum of the negative electrode active material of Example 1 is shown. Figure 1 As shown, the Si2p energy spectrum of the negative electrode active material in Example 1 has an original curve 100. The original curve 100 has a characteristic peak in both the 98–101 eV and 101–105 eV ranges. After peak fitting processing of the characteristic peak in the 98–101 eV range, a fitted curve 200 can be formed. The fitted curve 200 at the 101–105 eV position exhibits the superposition of two subpeaks, which include:

[0198] The first subpeak 201 has a binding energy of 99.7 eV (corresponding to the binding energy of the Si-C bond); and

[0199] The second subpeak 202 has a binding energy of 98.9 eV (corresponding to the binding energy of the Si-Si bond);

[0200] The peak area A of the first sub-peak 201 Si-CThe peak area A of the second sub-peak 202 Si-Si Ratio A Si-C / A Si-Si The value is 1.7. The peak intensities of both the first and second subpeaks are <2000. Examples A of each embodiment and comparative example... Si-C / A Si-Si The test results are shown in Table 2.

[0201] 2) XRD testing, grain size calculation, laser diffraction grain size distribution

[0202] The XRD patterns of the aforementioned silicon-carbon materials were obtained using a Bruker D8 Discover X-ray diffractometer, according to the JIS K 0131-1996 test method, with a test angle range of 20°–80°. After data acquisition, the data were fitted using X'Pert Highscoreplus software, and the grain size of the silicon (1 1 1) crystal plane corresponding to 28.5° ± 0.1° was calculated using the Scherrer equation.

[0203] The XRD patterns of Example 1 and Comparative Example 1 are as follows: Figure 2 As shown. In the XRD pattern of the negative electrode active material of Comparative Example 1, diffraction peaks of Li2SiO3 and Si can be observed. The distribution of diffraction peaks in the XRD pattern of the negative electrode active material of Example 1 is basically consistent with that of the Comparative Example, but the intensity of the diffraction peaks is weakened. This indicates that the silicon-carbon composite material and carbon material deposited on the substrate in Example 1 basically do not have diffraction peaks and are essentially amorphous.

[0204] The silicon grain sizes calculated based on the Scherrer equation are shown in the table below. The average silicon grain size in the negative electrode active materials of Comparative Example 1 and Example 1 is in the range of 6 nm to 8 nm.

[0205] The particle size distribution data of the negative electrode active materials of the examples and comparative examples, obtained by laser diffraction, are shown in the table below. These include volumetric particle size data Dv10 (μm), Dv50 (μm), Dv90 (μm), and Dv99 (μm), as well as number particle size distribution data D... N 10 μm. The particle size was measured using laser diffraction methods commonly used in the field, such as GB / T 19077-2016 Laser Diffraction Method for Particle Size Distribution. The particle size distribution data of the negative electrode active materials of Example 1 and Comparative Example 1 are shown in Table 1.

[0206] Table 1

[0207] Comparative Example 1 Example 1 Dv10(μm) 3.8 4.3 Dv50(μm) 6.0 7.2 Dv90(μm) 9.3 12.1 Dv99(μm) 12.0 16.4 <![CDATA[D N 10(μm)]]> 2.8 3.1 Silicon grain size / Scherrer formula calculation 7.1 6.7

[0208] 3) Elemental composition analysis

[0209] The elemental composition of the negative electrode active material prepared in Example 1 was determined according to the following test methods.

[0210] Carbon content test: The carbon content of the material was tested using an HSC-140 carbon content analyzer in accordance with the GB / T 20123-2006 / ISO 15350:2000 test standard.

[0211] Lithium, silicon, and oxygen content testing: The lithium and silicon contents were measured using an inductively coupled plasma atomic emission spectrometer (ICP, iICAP 7400 equipment) according to standard EPA 6010D-2014. The oxygen content was calculated based on the carbon content / lithium content / silicon content obtained from the test: oxygen content = 100% - silicon content - carbon content - lithium content.

[0212] The composition of the negative electrode active material in Example 1 is as follows: Li 6.8wt%, Si 57wt%, O 29.7wt%, C 6.5wt%.

[0213] In the negative electrode active material of Example 1, the silicon-carbon composite material constituting the first coating layer has the following composition: silicon content 97.5% and carbon content 2.5% (calculated based on silicon / carbon content before and after deposition). The test results of each example and comparative example are shown in Table 2.

[0214] 4) Battery initial charge / discharge efficiency:

[0215] The first week's cycle efficiency test procedure is as follows:

[0216] After assembly, the button cell battery was left to stand for 60 minutes.

[0217] Lithium intercalation capacity: First, discharge to 5mV using a constant current of 0.05C, then discharge to 5mV using 50μA, and let stand for 10 minutes.

[0218] Lithium removal capacity: 1.5V when charged at 0.1C.

[0219] The specific capacity-voltage curves for lithium insertion-extraction in the first week are as follows: Figure 3 As shown.

[0220] First-week cycle efficiency (referred to as first-week efficiency) is calculated using the following formula:

[0221] First-efficiency percentage = Lithium removal capacity / Lithium insertion capacity

[0222] The test results are shown in Table 2 below.

[0223] From the above table 2 and Figure 3 As can be seen, compared with Comparative Example 1, the negative electrode active material of Example 1 has significantly improved delithiation capacity and lithium insertion capacity. The first-stage efficiency of the negative electrode active material of Example 1 is basically equivalent to that of Comparative Example 1. The test results of each example and comparative example are shown in Table 2.

[0224] 5) Battery cycle life testing:

[0225] The negative electrode active materials of the examples and comparative examples were assembled into full cells.

[0226] The positive electrode slurry formulation is as follows: The positive electrode NCM ternary material, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are mixed at a mass ratio of 97:1.5:1.5. N-methylpyrrolidone (NMP) solvent is added, and the mixture is stirred under vacuum until homogeneous, yielding a positive electrode slurry with a solid content of 77 wt%. The positive electrode slurry is uniformly coated onto the positive electrode current collector aluminum foil and dried at 85°C. Then, it undergoes cold pressing, edge trimming, slitting, and sheet cutting. Finally, it is dried under vacuum at 85°C for 4 hours to obtain the ready-to-use positive electrode sheet.

[0227] The negative electrode slurry formulation is as follows: The negative electrode active material (90% graphite, 10% silicon), conductive agent (containing CNTs), thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed in a mass ratio of 96.2:1.3:1.0:1.5. Deionized water is added as a solvent, and the mixture is stirred under vacuum until homogeneous, yielding a negative electrode slurry with a solid content of 52%. The negative electrode slurry is uniformly coated onto the first negative electrode film layer and dried at 85°C. Then, it undergoes cold pressing, edge trimming, slitting, and sheet cutting. Finally, it is dried under vacuum at 120°C for 12 hours to obtain the ready-to-use negative electrode sheet.

[0228] The electrolyte formulation is as follows: the organic solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC, and DEC is 20:20:60. In an argon-atmosphere glove box with a water content of <10 ppm, thoroughly dried lithium salt is dissolved in the above organic solvent, and then 10 wt% of the additive fluoroethylene carbonate (FEC) is added and mixed thoroughly to obtain the electrolyte. The concentration of lithium salt is 1 mol / L.

[0229] The positive electrode slurry is coated onto an aluminum foil current collector to obtain a positive electrode sheet, and the negative electrode slurry is coated onto a copper foil current collector to obtain a negative electrode sheet. The positive electrode sheet, separator, and negative electrode sheet are stacked, wound, and placed inside the battery casing. Electrolyte is injected and the casing is sealed to obtain a full battery.

[0230] The full battery was subjected to charge-discharge cycle testing at charge / discharge rates of 0.5C / 1C and a cutoff voltage of 2.5-4.25V. Capacity retention versus cycle number curves were obtained, as shown below. Figure 4 As shown in Table 2, the retention rate test results for each embodiment and comparative example after 200 cycles are as follows.

[0231] As shown in Table 2 and Figure 4It can be seen that after 200 cycles, the capacity retention rates of the full cells of Example 1 and Comparative Example 1 were 96.6% and 96.8%, respectively. The capacity retention rates of Example 1 and Comparative Example 1 are basically the same. The material of Example 1 not only significantly improves the specific capacity but also maintains a good capacity retention rate.

[0232] 6) Cell energy density test

[0233] At 25°C, the batteries prepared in the examples and comparative examples were fully discharged at 1C, then fully charged and discharged at 1C, and the actual discharge energy was recorded. At 25°C, the batteries were weighed using an electronic balance. The ratio of the actual 1C discharge energy D / Wh to the battery weight m / kg is the actual energy density E of the battery, E = D / m.

[0234] The energy densities of the full cells in Example 1 and Comparative Example 1 were 276 Wh / kg and 266 Wh / kg, respectively, representing an energy density improvement of 3.8%. The energy density test results for each example and comparative example are shown in Table 2 below.

[0235] Table 2

[0236]

[0237] The XPS Si2p spectra of the negative electrode active materials in Examples 1-3, after peak fitting, showed a peak area ratio of 1-2:1 between the first and second subpeaks. When used in secondary batteries, these negative electrode active materials exhibited improved specific capacity, improved initial efficiency, and better cycle life.

[0238] After peak fitting, the XPS Si2p spectrum of the negative electrode active material in Comparative Example 3 showed a peak area ratio of less than 1 between the first and second subpeaks, indicating a high pure silicon content and large silicon grains, which is detrimental to lifespan. In Comparative Example 2, the peak area ratio between the first and second subpeaks was greater than 2, indicating an excessively high carbon content in the negative electrode active material, resulting in a low specific capacity and poor initial efficiency.

[0239] 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, comprising a silicon-carbon composite material, wherein the silicon content in the silicon-carbon composite material is 95wt% to 99.9wt%; the X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has a Si2p spectrum, wherein the Si2p spectrum has at least one characteristic peak, and the characteristic peak, after peak splitting, can form the following subpeaks, including: The first subpeak has a binding energy of 99.5–99.9 eV; as well as The second subpeak has a binding energy of 98.7–99.1 eV; The peak area ratio of the first subpeak to the second subpeak is (1~2):

1. The binding energy of the first subpeak corresponds to the binding energy of the Si-C bond; the binding energy of the second subpeak corresponds to the binding energy of the Si-Si bond.

2. The negative electrode active material according to claim 1, having one or more of the following characteristics: (1) The binding energy of the first subpeak is 99.6–99.8 eV; (2) The binding energy of the second subpeak is 98.8–99.0 eV; (3) The ratio of the peak area of ​​the first subpeak to that of the second subpeak is (1.5~2):1; (4) The carbon content in the silicon-carbon composite material is 0.1wt% to 5wt%.

3. The negative electrode active material according to claim 1, wherein the negative electrode active material comprises a matrix and the silicon-carbon composite material, and the silicon-carbon composite material is attached to the matrix.

4. The negative electrode active material according to claim 3, wherein the matrix has a porous internal structure, and the silicon-carbon composite material is attached to the matrix at the following location: The outer surface of the substrate; and / or The porous internal structure contains pores.

5. The negative electrode active material according to claim 3 or 4, wherein, The substrate material includes one or more of the following: carbon materials, silicon oxide materials, lithium titanate materials, or combinations thereof.

6. The negative electrode active material according to claim 3 or 4, wherein the negative electrode active material further comprises a carbon coating layer, the carbon coating layer covering the matrix and / or the silicon-carbon composite material.

7. The negative electrode active material according to claim 5, wherein, The carbon material includes one or more of the following: graphite material, hard carbon material, soft carbon material, or a combination thereof.

8. The negative electrode active material according to claim 1 or 2, wherein, The silicon-carbon composite material contains silicon grains, and the grain size of the silicon grains is less than 20 nm.

9. The negative electrode active material according to claim 1 or 2, wherein, The volume median particle size (DV50) of the negative electrode active material is 1–10 μm.

10. The negative electrode active material according to claim 1 or 2, wherein, The peak intensities of both the first and second subpeaks are <2000.

11. A method for preparing a negative electrode active material, comprising the following steps: S1: Provide a substrate and vapor deposition equipment, wherein the substrate is placed in a deposition furnace and preheated to 200~300°C by purging with inert gas; S2: Gas is introduced into the vapor deposition equipment in the first mode, the first mode including the simultaneous introduction of silicon source gas and carbon source gas into the vapor deposition equipment; S3: React silicon source gas and carbon source gas and deposit the reaction products on the matrix to form a silicon-carbon composite material, wherein the silicon content in the silicon-carbon composite material is 95wt% to 99.9wt%. The silicon-carbon composite material exhibits an X-ray photoelectron spectroscopy (XPS) spectrum with a Si2p pattern. This Si2p spectrum has at least one characteristic peak, which, after peak splitting, can form the following subpeaks: The first subpeak has a binding energy of 99.5–99.9 eV; and The second subpeak has a binding energy of 98.7–99.1 eV; The peak area ratio of the first subpeak to the second subpeak is (1~2):

1. The binding energy of the first subpeak corresponds to the binding energy of the Si-C bond; the binding energy of the second subpeak corresponds to the binding energy of the Si-Si bond.

12. The method according to claim 11, wherein, Step S2 has one or more of the following characteristics: (1) The silicon source gas is one or both of silane and disilane; (2) The carbon source gas is one or more of methane, ethylene, and acetylene; (3) The volumetric flow rate ratio of silicon source gas to carbon source gas is 2 to 10:

1.

13. The method according to claim 11 or 12, wherein, In step S2, the first mode includes simultaneously introducing silicon source gas, carbon source gas, and inert gas into the vapor deposition equipment.

14. The method according to claim 13, wherein, Step S2 has one or more of the following characteristics: (1) The inert gas is one or more of nitrogen and argon; (2) The flow rate of inert gas introduced into the vapor deposition equipment accounts for 30-85% of the total gas flow rate.

15. The method according to claim 11 or 12, wherein, In step S2, gas is introduced into the vapor deposition equipment according to the first mode, and the gas pressure inside the equipment is maintained at 200-600 Pa higher than the standard atmospheric pressure.

16. The method according to claim 11 or 12, wherein, Step S3 has one or more of the following characteristics: (1) Step S3 is carried out at 400-800℃; (2) Step S3 lasts for 1 to 12 hours.

17. The method according to claim 11 or 12, wherein, Step S3 is followed by step S4: S4: Deposit carbon material on the product of step S3.

18. The method according to claim 17, wherein, Step S4 includes the following operations: S4a: After forming the silicon-carbon composite material, gas is introduced into the vapor deposition equipment according to the second mode. The second mode includes simultaneously introducing carbon source gas and inert gas into the vapor deposition equipment, with the carbon source gas accounting for 5% to 15% and the inert gas accounting for 85% to 95%. S4b: Decomposes the carbon source gas into carbon materials and deposits them on the silicon-carbon composite material.

19. The method according to claim 18, wherein, Operation S4b has one or more of the following characteristics: (1) Step S4b is performed at 700–850°C; (2) Step S4b lasts for 1 to 6 hours.

20. A negative electrode active material, prepared by the method described in any one of claims 11 to 19.

21. A secondary battery comprising a negative electrode active material according to any one of claims 1 to 10 and 20.

22. An electrical device comprising a secondary battery according to claim 21.

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