Silicon-carbon anode materials, anode sheets, secondary batteries, battery modules, battery packs, and electrical devices.

Abstract

This application provides a silicon-carbon anode material, an anode sheet comprising the same, a secondary battery, a battery module, a battery pack, and an electrical device. When a battery is charged and discharged using the silicon-carbon anode material described in this application as the working electrode, lithium metal as the counter electrode, and an electrolyte containing lithium-ion conductive material, and a curve showing the relationship between the differential value dQ / dV obtained by differentiating the working electrode potential V with respect to the charge / discharge capacity Q and the working electrode potential V, when the anode material is energized in the delithiation direction, the ratio of the maximum value Y of dQ / dV between 400-480 mV to the maximum value X of dQ / dV between 200-255 mV is 3.5-15, optionally 4-9, and more preferably 4.5-6.5.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a silicon-carbon anode material and its preparation method, an anode sheet containing the same, a secondary battery, a battery module, a battery pack, and an electrical device. Background Technology

[0002] In recent years, with the increasingly widespread application of lithium-ion batteries, they have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Among the anode materials for lithium-ion batteries, silicon-carbon anode materials have attracted much attention due to the advantages of silicon, such as its extremely high theoretical specific capacity, low lithium storage reaction plateau, and wide distribution in nature. However, as the requirements for battery performance become increasingly stringent, how to further improve the specific capacity, initial coulombic efficiency, and cycle performance of silicon-carbon anode material batteries remains an urgent issue to be addressed. Summary of the Invention

[0003] This application is made in view of the above-mentioned problems, and its purpose is to provide a silicon-carbon anode material, such that a battery using the silicon-carbon anode material has a high initial coulombic efficiency, good cycle performance and fast charging performance.

[0004] To achieve the above objectives, this application provides a silicon-carbon anode material and its preparation method, an anode sheet containing the same, a secondary battery, a battery module, a battery pack, and an electrical device.

[0005] The first aspect of this application provides a silicon-carbon anode material. When a battery is charged and discharged using the anode prepared from the silicon-carbon anode material as the working electrode, lithium metal as the counter electrode, and an electrolyte containing a lithium-ion conductive material, and a curve showing the relationship between the differential value dQ / dV obtained by differentiating the working electrode potential V with respect to the charge / discharge capacity Q and the working electrode potential V is plotted, when the anode material is energized in the delithiation direction, the ratio of the maximum value Y of dQ / dV between 400-480mV to the maximum value X of dQ / dV between 200-255mV is 3.5-15, optionally 4-9, and more preferably 4.5-6.5.

[0006] Batteries using the silicon-carbon anode material of this application exhibit high specific capacity, high initial coulombic efficiency, and good cycle performance.

[0007] In any embodiment, optionally, in the X-ray diffraction (XRD) pattern of the silicon-carbon anode material of this application, the ratio of the intensity of the peak at 2θ = 28.4 to the intensity of the peak at 2θ = 54.6 is 1.1-4.5.

[0008] In any embodiment, optionally, the silicon content is 2.5%-10%, optionally 3%-7%, based on the total weight of the silicon-carbon anode material. When the silicon content is within the above range, the battery using the silicon-carbon anode material of this application has a higher specific capacity and better cycle performance.

[0009] In any embodiment, optionally, the median particle size Dv50 of the silicon-carbon anode active material is 10μm-15μm, and optionally 11μm-14μm. If the median particle size of the silicon-carbon anode material is too large, lithium plating may occur during cycling, deteriorating cycle performance. Conversely, if the median particle size is too small, it may lead to increased compaction density, resulting in insufficient electrolyte wetting of the active material, similarly deteriorating cycle performance.

[0010] In any embodiment, optionally, the silicon-carbon anode material has no pores or the number of pores with a diameter greater than 50 nm in a single silicon-carbon anode material particle is less than 10. When the number of pores in the silicon-carbon anode material is within the above range, it helps to reduce side reactions at the pore interface, thereby improving the initial coulombic efficiency and cycle performance.

[0011] In any embodiment, optionally, the specific surface area of ​​the silicon-carbon anode material is 1 m². 2 -3m 2 1.1m is optional. 2 -2m 2 When the specific surface area of ​​silicon-carbon anode materials is within the above range, they possess an appropriate number of reactive sites, which helps to reduce side reactions and improve kinetic performance.

[0012] A second aspect of this application provides a method for preparing a silicon-carbon anode material, comprising the following steps:

[0013] Provide silicon and carbon sources;

[0014] The silicon source and carbon source are added to the additive solution, mixed evenly, and then the solvent is removed to obtain a mud-like mixture.

[0015] Heating the mud-like mixture yields a silicon-carbon anode material intermediate.

[0016] The silicon-carbon anode material intermediate is heated under an inert gas atmosphere to obtain the silicon-carbon anode material, wherein...

[0017] When a battery consisting of a negative electrode made of the aforementioned silicon-carbon negative electrode material as the working electrode, lithium metal as the counter electrode, and an electrolyte containing lithium-ion conductive material is charged and discharged, and a curve showing the relationship between the differential value dQ / dV obtained by differentiating the working electrode potential V with respect to the charge / discharge capacity Q and the working electrode potential V is plotted, when the negative electrode material is energized in the delithiation direction, the ratio of the maximum value Y of dQ / dV between 400-480mV to the maximum value X of dQ / dV between 200-255mV is 3.5-15, optionally 4-9, and more preferably 4.5-6.5.

[0018] The preparation method of this application is simple, the raw materials are widely available and the cost is low, which is conducive to large-scale industrial application.

[0019] In any embodiment, optionally, the median particle size Dv50 of the silicon source is 1 μm-3 μm, and the median particle size Dv50 of the carbon source is 8 μm-14 μm. When the median particle sizes of the silicon source and the carbon source are within the above ranges, the prepared silicon-carbon anode material has a suitable particle size range, which helps to improve the cycle performance of the battery using the silicon-carbon anode material.

[0020] In any embodiment, the additive may optionally be selected from one or more of glucose, phenolic resin, sucrose, asphalt, polyacrylonitrile, sodium carboxymethyl cellulose, polyvinylidene fluoride, and polytetrafluoroethylene.

[0021] In any embodiment, optionally, the heating conditions for the mud-like mixture are: pretreatment at 100-400°C, optionally 100-300°C, for 2-6 hours. When heat treatment is performed under the above conditions, the prepared silicon-carbon anode material is more conducive to improving the cycle performance of the battery.

[0022] In any embodiment, optionally, the silicon-carbon anode material intermediate is heat-treated in an inert gas atmosphere by heating at 600-1000°C for 2-6 hours. Treatment under these conditions results in a silicon-carbon anode material that further improves the cycle performance of the battery.

[0023] In any embodiment, optionally, the carbon source is selected from graphite, coke, activated carbon, diamond, C 60 One or more of the following can be selected, and graphite with a graphitization degree of 82%-97% can be used.

[0024] In any embodiment, the silicon source may optionally be selected from one or more of elemental silicon, silicon oxide, and silicates, and may optionally be elemental silicon.

[0025] A third aspect of this application provides a negative electrode sheet, comprising a silicon-carbon negative electrode material according to the first aspect of this application or a silicon-carbon negative electrode material prepared according to the method of the second aspect of this application.

[0026] The fourth aspect of this application provides a secondary battery, including a silicon-carbon anode material according to the first aspect of this application, a silicon-carbon anode material prepared by the method according to the second aspect of this application, or an anode sheet according to the third aspect of this application.

[0027] The fifth aspect of this application provides a battery module including a secondary battery according to the fourth aspect of this application.

[0028] A sixth aspect of this application provides a battery pack comprising one or more of a secondary battery according to a fourth aspect of this application or a battery module according to a fifth aspect of this application.

[0029] The seventh aspect of this application provides an electrical device comprising one or more of a secondary battery according to the fourth aspect of this application, a battery module according to the fifth aspect of this application, or a battery pack according to the sixth aspect of this application.

[0030] The battery module, battery pack, or power device of this application includes the secondary battery of the fourth aspect of this application, and therefore has at least the same advantages as the secondary battery described in the fourth aspect of this application. Attached Figure Description

[0031] Figure 1 The graph shows the relationship between the differential value dQ / dV obtained by differentiating the working electrode potential V with respect to the charge / discharge capacity Q and the working electrode potential V.

[0032] Figure 2 These are typical scanning electron microscope (SEM) images of silicon-carbon anode materials with and without pores (left) and with pores (right).

[0033] Figure 3 This is the XRD pattern of the silicon-carbon anode material in Example 1.

[0034] Figure 4 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0035] Figure 5 yes Figure 4 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0036] Figure 6 This is a schematic diagram of a battery module according to one embodiment of this application.

[0037] Figure 7 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0038] Figure 8 yes Figure 7 An exploded view of a battery pack according to one embodiment of this application is shown.

[0039] Figure 9 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.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly Detailed Implementation

[0042] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the negative electrode active material, its manufacturing method, negative electrode sheet, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0043] 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.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0045] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0046] Unless otherwise specified, all steps of 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 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.

[0047] 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.

[0048] The terms “above,” “below,” “greater than,” or “less than” used in this application include the number itself. For example, “more than one” means one or more, and “more than one of A and B” means “A,” “B,” or “A and B.”

[0049] 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).

[0050] In this article, "median particle size" and "median particle size (Dv50)" are used synonymously. It refers to the particle size corresponding to the cumulative particle size distribution percentage of 50%. Its physical meaning is that 50% of the particles are larger than it and 50% are smaller than it. It is also called the median particle size.

[0051] To address the problems of low initial coulombic efficiency, low specific capacity, and poor cycle performance in batteries prepared using silicon-carbon anode materials in existing technologies, the inventors of this application conducted a charge-discharge experiment on a battery consisting of a silicon-carbon anode material as the working electrode, lithium metal as the counter electrode, and an electrolyte containing lithium-ion conductive materials. A curve was plotted showing the relationship between the differential value dQ / dV (derived from the working electrode potential V and the charge-discharge capacity Q) and the working electrode potential V. Through extensive research, the inventors unexpectedly discovered that in the aforementioned relationship curve, when the ratio of the maximum value Y of dQ / dV between 400-480 mV to the maximum value X of dQ / dV between 200-255 mV is 3.5-15, preferably 4-9, and more preferably 4.5-6.5, the secondary battery prepared using the corresponding silicon-carbon anode material can simultaneously possess high specific capacity, high initial coulombic efficiency, and good cycle performance.

[0052] Silicon-carbon anode materials

[0053] The first aspect of this application provides a silicon-carbon anode material, wherein a battery consisting of an anode prepared from the silicon-carbon anode material as a working electrode, lithium metal as a counter electrode, and an electrolyte containing a lithium-ion conductive material is charged and discharged. When a curve is plotted showing the relationship between the differential value dQ / dV obtained by differentiating the working electrode potential V with respect to the charge / discharge capacity Q and the working electrode potential V, when the anode material is energized in the delithiation direction, the ratio of the maximum value Y of dQ / dV between 400-480mV to the maximum value X of dQ / dV between 200-255mV is 3.5-15, optionally 4-9, and more preferably 4.5-6.5.

[0054] Although the mechanism is not yet clear, the inventors unexpectedly discovered that by screening silicon-carbon anode materials with a Y to X ratio within the above range, the specific capacity, initial coulombic efficiency, and cycle performance of batteries including the silicon-carbon anode materials can be improved.

[0055] In some embodiments, optionally, in the X-ray diffraction pattern of the silicon-carbon anode material described in this application, the ratio of the intensity of the peak at 2θ = 28.4 to the intensity of the peak at 2θ = 54.6 is 1.1-4.5.

[0056] The XRD testing of the silicon-carbon anode material of this application can be performed using methods commonly employed by those skilled in the art, such as according to JIS K0131-1996 General Rules for X-ray Diffraction Analysis. Alternatively, a Bruker D8 Discover X-ray diffractometer from BrukerAxS GmbH, Germany, can be used with CuKα rays as the radiation source, and the ray wavelength... The scanning 2θ angle range is 20° to 80°, and the scanning rate is 4° / min.

[0057] In some embodiments, the silicon content in the silicon-carbon anode material is optionally 2.5%-10%, optionally 3%-7%, based on the total weight of the silicon-carbon anode material.

[0058] Silicon is beneficial for increasing the specific capacity of silicon-carbon anode materials, thereby improving the energy density of the battery. However, excessive silicon should be avoided, as it can impair the expansion and contraction properties of the silicon-carbon anode material. This can lead to the anode material losing electrical contact with the current collector due to expansion, thus damaging the battery's cycle performance. Furthermore, excessive silicon content can also increase the gaps at the bonding points between particles, resulting in increased electrode rebound.

[0059] In some embodiments, the carbon content in the silicon-carbon anode material is optionally 80%-97.5%, or optionally 90%-96.5%, based on the total weight of the silicon-carbon anode material.

[0060] Carbon helps mitigate the deterioration of the expansion and contraction performance of the negative electrode material caused by silicon, thereby improving the cycle performance of the battery. However, excessive carbon content may lead to a decrease in the specific capacity of the negative electrode material, which in turn leads to a decrease in the specific capacity of the battery.

[0061] In some embodiments, the median particle size Dv50 of the silicon-carbon anode material is optionally 10 μm-15 μm, or optionally 11 μm-14 μm.

[0062] If the median particle size of silicon-carbon anode materials is too large, it may negatively impact the rate performance of the battery due to increased impedance. Furthermore, it may lead to lithium plating during cycling, further deteriorating the battery's cycle performance. Simultaneously, an excessively large median particle size can also cause the anode material to slightly expand and contract, resulting in loss of electrical contact with the current collector, thus reducing coulombic efficiency and cycle performance. Similarly, if the median particle size of silicon-carbon anode materials is too small, it may increase the number of electrochemical reaction sites, forming more SEI films and consuming more active lithium, leading to a decrease in initial coulombic efficiency. Additionally, a small particle size may increase the adhesion between particles, resulting in insufficient electrolyte wetting of the active material and worsening cycle performance.

[0063] It should be noted that the median particle size Dv50 of the silicon anode material in this application has a well-known meaning in the art and can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0064] In any embodiment, optionally, the silicon-carbon anode material has no pores or the number of pores with a diameter greater than 50 nm in a single silicon-carbon anode material particle is less than 10.

[0065] The more pores a silicon-carbon anode material has, the more side reactions may occur at the pore interface, consuming more active lithium and electrolyte, thus leading to a decrease in both initial coulombic efficiency and cycle performance. Simultaneously, the pores may adsorb electrolyte, resulting in insufficient electrolyte wetting of the active material and further deteriorating cycle performance.

[0066] In this application, the scanning electron microscopy (SEM) testing of the silicon-carbon anode material can be performed according to methods commonly used in the art. For example, a ZEISS Sigma 300 SEM can be used for testing, followed by testing in accordance with standard JY / T010-1996.

[0067] In any embodiment, optionally, the specific surface area of ​​the silicon-carbon anode material is 1 m². 2 -3m 2 1.1m is optional. 2 -2m 2 .

[0068] A larger specific surface area of ​​silicon-carbon anode materials generally results in more active sites, which may increase side reactions and affect the battery's cycle performance. Similarly, a smaller specific surface area of ​​silicon-carbon anode materials may lead to poorer kinetic performance and may also cause lithium plating, further deteriorating cycle performance.

[0069] The specific surface area of ​​the silicon anode material of this application has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using the nitrogen adsorption specific surface area analysis test method according to GB / T 19587-2017 standard for determining the specific surface area of ​​solid materials by gas adsorption BET method, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed using a Tri Star II 3020 specific surface area and porosity analyzer from Micromeritics, USA.

[0070] A second aspect of this application provides a method for preparing silicon-carbon anode materials, comprising the following steps:

[0071] Provide silicon and carbon sources;

[0072] The silicon source and carbon source are added to the additive solution, mixed evenly, and then the solvent is removed to obtain a mud-like mixture.

[0073] Heating the mud-like mixture yields a silicon-carbon anode material intermediate.

[0074] The silicon-carbon anode material intermediate is heated under an inert gas atmosphere to obtain the silicon-carbon anode material, wherein...

[0075] When a battery consisting of a negative electrode made of the aforementioned silicon-carbon negative electrode material as the working electrode, lithium metal as the counter electrode, and an electrolyte containing lithium-ion conductive material is charged and discharged, and a curve showing the relationship between the differential value dQ / dV obtained by differentiating the working electrode potential V with respect to the charge / discharge capacity Q and the working electrode potential V is plotted, when the negative electrode material is energized in the delithiation direction, the ratio of the maximum value Y of dQ / dV between 400-480mV to the maximum value X of dQ / dV between 200-255mV is 3.5-15, optionally 4-9, and more preferably 4.5-6.5.

[0076] In any embodiment, optionally, the median particle size Dv50 of the silicon source is 1μm-3μm, and the median particle size Dv50 of the carbon source is 8μm-14μm.

[0077] When the median particle size of the silicon source and the carbon source is within the above range, the silicon-carbon anode material prepared by the method described in this application has a high specific capacity and good cycle performance.

[0078] In any embodiment, the additive may optionally be selected from one or more of glucose, phenolic resin, sucrose, asphalt, polyacrylonitrile, sodium carboxymethyl cellulose, polyvinylidene fluoride, and polytetrafluoroethylene.

[0079] In any embodiment, optionally, in the preparation method described in this application, the silicon source and carbon source are mixed evenly in the additive solution by stirring.

[0080] In any embodiment, optionally, in the preparation method described in this application, the solvent in the mixture is removed by drying at 60-100°C.

[0081] In any embodiment, optionally, in the preparation method described in this application, the heating conditions for the mud-like mixture are: pretreatment at 100-400℃, optionally 100-300℃ for 2-6 hours.

[0082] In any embodiment, optionally, in the preparation method described in this application, the heat treatment conditions of the silicon-carbon anode material intermediate under an inert gas atmosphere are heating at 600-1000°C for 2-6 hours.

[0083] In any embodiment, optionally, in the preparation method described in this application, the carbon source is selected from graphite, coke, activated carbon, diamond, C 60 One or more of the following can be selected, and graphite with a graphitization degree of 82%-97% can be used.

[0084] In any embodiment, optionally, in the preparation method described in this application, the silicon source is selected from one or more of elemental silicon, silicon oxide, and silicate, and may be elemental silicon.

[0085] In any embodiment, optionally, the weight ratio of the added silicon source to the added carbon source is 2%-15%.

[0086] In any embodiment, optionally, the amount of the additive added is 3%-25% based on the total weight of the silicon source, carbon source and additive.

[0087] [Negative electrode plate]

[0088] A third aspect of this application provides a negative electrode sheet, comprising the silicon-carbon negative electrode material described in the first aspect of this application or the silicon-carbon negative electrode material prepared according to the method of the second aspect of this application.

[0089] 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.

[0090] 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.

[0091] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper 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.).

[0092] In some embodiments, in addition to the silicon-carbon anode material described in the first aspect of this application, the anode active material may also include anode active materials known in the art for use in batteries. As an example, the anode active material may also 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 battery anode active materials may also be used. These anode active materials may be used alone or in combination of two or more.

[0093] 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).

[0094] 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.

[0095] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0096] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as silicon-carbon 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 a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0097] [Positive electrode plate]

[0098] In this application, a secondary battery can be made using a negative electrode sheet containing the silicon-carbon negative electrode material of this application and a positive electrode sheet, or a coin cell can be made using a negative electrode sheet containing the silicon-carbon negative electrode material of this application and a counter electrode.

[0099] In some implementations, lithium metal is optionally used as the counter electrode to form a coin cell.

[0100] In some embodiments, a secondary battery may be made using a positive electrode and a negative electrode containing the silicon-carbon negative electrode material of this application.

[0101] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0102] 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.

[0103] 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.).

[0104] 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 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 0.1O2 (also known as NCM) 811 ), 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] [Electrolytes]

[0109] 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.

[0110] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] [Isolation membrane]

[0115] 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.

[0116] 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.

[0117] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0118] [Rechargeable Battery]

[0119] The fourth aspect of this application provides a secondary battery comprising the negative electrode active material described in the first aspect of this application, or the negative electrode active material prepared by the method described in the second aspect of this application, or the negative electrode sheet described in the third aspect of this application.

[0120] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0121] In some embodiments, the lithium-ion secondary battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0122] In some implementations, the outer packaging of a lithium-ion secondary battery can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of a lithium-ion 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 (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0123] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0124] 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 4 This is an example of a square-structured secondary battery 5.

[0125] In some implementations, refer to Figure 5 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0126] In some implementations, lithium-ion secondary batteries can be assembled into battery modules, and the number of lithium-ion batteries contained in a 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.

[0127] Figure 6 This is battery module 4, used as an example. (See reference...) Figure 6 In battery module 4, multiple lithium-ion 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 lithium-ion batteries 5 can be fixed in place using fasteners.

[0128] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple lithium-ion batteries 5 are housed.

[0129] 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.

[0130] Figure 7 and Figure 8 This is battery pack 1 as an example. (See reference...) Figure 7 and Figure 8 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.

[0131] 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.

[0132] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0133] Figure 9 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.

[0134] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0135] Example

[0136] 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.

[0137] The sources of raw materials involved in the embodiments of this application are as follows:

[0138]

[0139]

[0140] Example 1

[0141] 40g of glucose was dissolved in 200ml of deionized water, then 4.2g of elemental silicon with a median particle size Dv50 of 1.5μm and 155.8g of graphite with a median particle size Dv50 of 10μm and a graphitization degree of 91% (designated as graphite 1) were added. After mixing evenly at room temperature, the mixture was stirred at 80°C to remove the water solvent, resulting in a mud-like mixture. The mud-like mixture was transferred to a heat treatment furnace at 150°C and pretreated for 240 minutes to obtain a silicon-carbon anode material intermediate. The silicon-carbon anode material intermediate was heated at 900°C for 240 minutes in a nitrogen atmosphere. After cooling to room temperature, the resulting solid was pulverized to obtain the desired silicon-carbon anode material.

[0142] Counter electrode

[0143] A lithium metal sheet is used as the counter electrode.

[0144] [Preparation of Electrodes]

[0145] The silicon-carbon anode material from Example 1, conductive agent acetylene black, conductive agent CNT (carbon nanotube), binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were dissolved in deionized water at a weight ratio of 92:2:0.5:4.5:1 and stirred until homogeneous to prepare an anode slurry. The anode slurry was then subjected to a concentration of 6 mg / cm³. 2 The coating is evenly applied to the copper foil of the negative electrode current collector, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0146] Preparation of Electrolyte

[0147] In an argon-atmospheric glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) organic solvents were mixed evenly at a volume ratio of 3 / 7. 10% (based on the weight of the ethylene carbonate / ethyl methyl carbonate organic solvent) of fluoroethylene carbonate (FEC) was added, followed by 12.5% ​​(based on the weight of the ethylene carbonate / ethyl methyl carbonate organic solvent) of lithium LiPF6 dissolved in the organic solvent. The mixture was stirred evenly to obtain the electrolyte of Example 1.

[0148]

Isolation Film

[0149] Polyethylene (PE) film is used as the separator.

[0150] [Preparation of button cells]

[0151] The counter electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the counter electrode and the negative electrode to provide insulation. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer package, filled with the prepared basic electrolyte, and sealed to obtain a coin cell.

[0152] The preparation conditions for other embodiments and comparative examples of this application are shown in Tables 1 and 3. The preparation of the counter electrode, electrode sheet, electrolyte, separator, and coin cell in the above embodiments and comparative examples are the same as those in Example 1.

[0153] [Relevant Parameter Tests]

[0154] Size capacity, initial coulombic efficiency, and cycle capacity retention tests:

[0155] At 25℃ and normal pressure, the coin cell was discharged at a constant current rate of 0.1C to 0.005V, then discharged at a constant current rate of 0.04C to 0.005V, and then allowed to stand for 10 minutes. The discharge capacity at this point was recorded as the first lithium insertion capacity. The coin cell was then charged at a constant current rate of 0.1C to 1.5V, and allowed to stand for another 10 minutes. This constituted one charge-discharge cycle, and the charging capacity at this point was recorded as the first delithiation capacity, defined as the specific capacity of the material. The coin cell was subjected to 50 charge-discharge cycles using the above method, and the delithiation capacity was recorded each time.

[0156] Initial coulombic efficiency (%) of coin cell = (Lithium de-lithiation capacity in the first cycle / Lithium insertion capacity in the first cycle) × 100%;

[0157] Coin cell cycle capacity retention (%) = Lithium removal capacity at 50th cycle / Lithium removal capacity at 1st cycle × 100%.

[0158] Silicon content test:

[0159] The silicon content in the anode material of this application can be determined using instruments and methods known in the art. For example, the silicon-carbon anode material can be digested according to EPA-3052-1996, "Microwave Acid Digestion of Silicates," and then the silicon content can be determined using an ICAP-7000 inductively coupled plasma atomic emission spectrometer (ICP-OES) from Thermo Fisher Scientific, according to EPA 6010D-2014, "Inductively Coupled Plasma Atomic Emission Spectrometry." The specific testing method is as follows: 0.5g of silicon-carbon anode material sample is microwave-digested using 10mL of 65% nitric acid and 10mL of 40% hydrofluoric acid. After digestion, the sample is added to a 50mL volumetric flask and diluted to volume. The silicon content is then determined using an ICAP-7000 ICP-OES.

[0160] Methods for measuring the internal porosity of silicon particles:

[0161] 1. Prepare silicon-carbon anode material into a slurry, coat it onto the current collector, and dry it to form an electrode sheet.

[0162] 2. The negative electrode sheet was cut using plasma cutting technology to obtain a clean cross-section. The cross-section was then observed under a scanning electron microscope equipped with an energy dispersive spectroscopy (EDS) device. Five intact silicon particles with a diameter > 800 nm (the diameter of the particle is defined as the diameter of its circumscribed circle) were randomly selected for analysis.

[0163] 3. For each silicon particle, energy dispersive spectroscopy (EDS) is used to analyze its composition. The particle composition is used to determine whether it is a silicon particle. The identification criteria for silicon particles in the following examples are as follows: if the silicon content of the particle is ≥7wt%, it is determined to be a silicon particle.

[0164] 4. Measure the internal porosity of each silicon particle. The measurement method is as follows: First, pores at the edge of the SEM image are not counted; only the number of pores inside the SEM image is recorded. The diameter of the circumcircle of the pore inside the silicon particle is defined as the diameter of that pore. If the pore diameter is ≥50nm, it is counted as 1. This process continues until all pores inside the particle have been measured. The total number of pores inside the particle is then summed.

[0165] Test for graphitization degree:

[0166] The degree of graphitization of the graphite described in this application can be tested using methods known in the art. For example, the degree of graphitization can be tested using an X-ray diffractometer (Bruker D8 Discover), and the test can be performed with reference to JIS K 0131-1996 and JB / T 4220-2011. The size of d002 can be measured, and then the degree of graphitization can be calculated according to the formula G=(0.344-d002) / (0.344-0.3354), where d002 is the interlayer spacing in the artificial graphite crystal structure expressed in nanometers (nm).

[0167] Table 1: Preparation conditions of the examples

[0168]

[0169]

[0170] Table 2: Performance of secondary batteries prepared using the cathode materials from the examples

[0171]

[0172] As shown in Tables 1 and 2, the batteries prepared using the silicon-carbon anode materials of Examples 1-11 have high specific capacity, high initial coulombic efficiency, and good cycle capacity retention.

[0173] As can be seen from Examples 1-11, when the Y / X ratio of the silicon-carbon anode material is in the range of 3.5-15, the cycle capacity retention rate of the secondary battery is significantly better than that of Comparative Examples 1-3, where the Y / X ratio is not in this range.

[0174] As can be seen from Examples 1-5 and Comparative Example 2, the specific capacity of the secondary battery increases with the gradual increase of silicon content. However, when the silicon content exceeds 10% (Comparative Example 2), the cycle capacity retention rate of the secondary battery decreases significantly.

[0175] As can be seen from Examples 3 and 6-9, as the graphitization degree of the carbon source increases from 70% to 99%, the specific capacity of the battery gradually increases, while the initial coulombic efficiency and cycle capacity initially increase and then decrease. When the graphitization degree of the carbon source is 82%-97%, the overall performance of the battery is better.

[0176] As can be seen from Examples 10 and 7, Examples 3 and 11, and Examples 8 and 12, as the pretreatment temperature increases from 100°C to 400°C, the specific capacity and initial coulombic efficiency of the corresponding batteries gradually decrease, but the cycle capacity remains unchanged, initially increasing and then decreasing. As can be seen from Example 3 and Comparative Example 1, as the pretreatment temperature increases from 150°C to 500°C, all the performance characteristics of the corresponding batteries deteriorate significantly.

[0177] Table 3: Changes in relevant parameters of the obtained silicon-carbon anode material

[0178]

[0179] Table 4: Performance of secondary batteries prepared using the cathode materials from the examples

[0180]

[0181]

[0182] As shown in Tables 3 and 4, the specific capacity, initial coulombic efficiency, and cycle capacity retention of Examples 14-24 are significantly better than those of Comparative Examples 4-6.

[0183] As can be seen from Examples 14-16 and Comparative Example 4, when the number of pores with a diameter greater than 50 nm in a single silicon-carbon anode material is less than 10, the battery performance does not change significantly. However, as the number of pores continues to increase to 30, the specific capacity and initial coulombic efficiency decrease significantly, and the capacity retention rate after 50 cycles decreases even more significantly.

[0184] As can be seen from Examples 17-20 and Comparative Example 5, the battery performance of silicon-carbon anode materials with a median particle size Dv50 of 10μm-15μm is better than that of materials with a median particle size of 18μm. The improvement in battery performance is even more pronounced when the median particle size is 11μm-14μm.

[0185] As can be seen from Examples 21-24 and Comparative Example 6, the specific surface area of ​​the silicon-carbon anode material is 1 m². 2 -3m 2 The battery performance at the specified time is better than that at a specific surface area of ​​3.5. When the specific surface area is 1.1m², the battery performance is superior. 2 -2m 2 The improvement in battery performance is more pronounced at that time.

[0186] 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 silicon-carbon anode material, wherein, When a battery consisting of a working electrode made of the aforementioned silicon-carbon anode material, a counter electrode made of lithium metal, and an electrolyte containing lithium-ion conductive material is charged and discharged, and a curve showing the relationship between the differential value dQ / dV obtained by differentiating the working electrode potential V with respect to the charge / discharge capacity Q and the working electrode potential V is plotted, when the anode material is energized in the delithiation direction, the ratio of the maximum value Y of dQ / dV between 400-480mV to the maximum value X of dQ / dV between 200-255mV is 3.5-15; the number of pores with a diameter greater than 50nm in a single silicon-carbon anode material particle is less than 10; and the median particle size Dv50 of the silicon-carbon anode material is 10μm-15μm. The specific surface area of ​​the silicon-carbon anode material is 1m². 2 / g-3m 2 / g.

2. The silicon-carbon anode material according to claim 1, wherein, The ratio of Y to X is 4-9.

3. The silicon-carbon anode material according to claim 1, wherein, The ratio of Y to X is 4.5-6.

5.

4. The silicon-carbon anode material according to claim 1, wherein, In the X-ray diffraction pattern, the ratio of the intensity of the peak at 2θ = 28.4° to the intensity of the peak at 2θ = 54.6° is 1.1 to 4.

5.

5. The silicon-carbon anode material according to any one of claims 1 to 4, wherein, The silicon content is 2.5%-10%, based on the total weight of the silicon-carbon anode material.

6. The silicon-carbon anode material according to claim 5, wherein, The silicon content is 3%-7%, based on the total weight of the silicon-carbon anode material.

7. The silicon-carbon anode material according to any one of claims 1 to 4, wherein, The median particle size Dv50 of the silicon-carbon anode material is 11μm-14μm.

8. The silicon-carbon anode material according to any one of claims 1 to 4, wherein, The specific surface area of ​​the silicon-carbon anode material is 1.1 m². 2 / g-2m 2 / g.

9. A method for preparing silicon-carbon anode materials, comprising the following steps: Provide silicon and carbon sources; The silicon source and carbon source are added to the additive solution, mixed evenly, and then the solvent is removed to obtain a mud-like mixture. Heating the mud-like mixture yields a silicon-carbon anode material intermediate. The silicon-carbon anode material intermediate is heated under an inert gas atmosphere to obtain the silicon-carbon anode material, wherein... When a battery consisting of a negative electrode made of the silicon-carbon negative electrode material as the working electrode, lithium metal as the counter electrode, and an electrolyte containing lithium-ion conductive material is charged and discharged, and a curve showing the relationship between the differential value dQ / dV obtained by differentiating the working electrode potential V with respect to the charge / discharge capacity Q and the working electrode potential V is plotted, when the negative electrode material is energized in the delithiation direction, the ratio of the maximum value Y of dQ / dV between 400-480mV to the maximum value X of dQ / dV between 200-255mV is 3.5-15. The additive is selected from one or more of glucose, phenolic resin, sucrose, asphalt, polyacrylonitrile, sodium carboxymethyl cellulose, polyvinylidene fluoride, and polytetrafluoroethylene; The heating conditions for the mud-like mixture are: pretreatment at 100-400℃ for 2-6 hours; The carbon source is selected from graphite, coke, activated carbon, and C. 60 One or more of them.

10. The method according to claim 9, wherein, The ratio of Y to X is 4-9.

11. The method according to claim 9, wherein, The ratio of Y to X is 4.5-6.

5.

12. The method according to any one of claims 9 to 11, wherein, The median particle size Dv50 of the silicon source is 1μm-3μm, and the median particle size Dv50 of the carbon source is 8μm-14μm.

13. The method according to any one of claims 9 to 11, wherein The heating conditions for the mud-like mixture are: pretreatment at 100-300℃ for 2-6 hours.

14. The method according to any one of claims 9 to 11, wherein The heat treatment conditions for the silicon-carbon anode material intermediate under an inert gas atmosphere are heating at 600-1000℃ for 2-6 hours.

15. The method according to any one of claims 9 to 11, wherein The carbon source is graphite with a graphitization degree of 82%-97%.

16. The method according to any one of claims 9 to 11, wherein, The silicon source is selected from one or more of elemental silicon, silicon oxide, and silicates.

17. The method according to any one of claims 9 to 11, wherein, The silicon source is elemental silicon.

18. A negative electrode sheet comprising a silicon-carbon negative electrode material according to any one of claims 1-8 or a silicon-carbon negative electrode material prepared by any one of claims 9-17.

19. A secondary battery comprising a silicon-carbon anode material according to any one of claims 1-8, or a silicon-carbon anode material prepared by any one of claims 9-17, or an anode sheet according to claim 18.

20. A battery module comprising the secondary battery of claim 19.

21. A battery pack comprising one or more of the secondary battery of claim 19 or the battery module of claim 20.

22. An electrical device comprising one or more of the secondary battery of claim 19, the battery module of claim 20, or the battery pack of claim 21.

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