Negative electrode material, and preparation method and application thereof

Abstract

The invention discloses a negative electrode material and a preparation method and application of the negative electrode material, the negative electrode material comprises an inner core and a coating layer, the coating layer wraps the inner core, the coating layer comprises one or more layers, the material of the inner core comprises boron-doped porous silicon carbon, and the material of the inner core comprises boron-doped porous silicon carbon. The material of the coating layer comprises one or more of a solid electrolyte and heterostructure carbon, the negative electrode material can be applied to preparation of a negative electrode of a battery, and the rate capability and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] This application relates to the field of negative electrode material technology, specifically to a negative electrode material, a method for preparing the negative electrode material, and its application. Background Technology

[0002] With the rapid development of portable electronic devices, electric vehicles, and energy systems, batteries, as the core device for energy conversion, are also constantly being updated and iterated.

[0003] In related technologies, rechargeable lithium-ion batteries are widely used in consumer electronics, advanced robotics, grid-scale energy storage, and electric vehicles. However, the energy density of graphite-based lithium-ion batteries limits the continued development of these technologies. Silicon is currently one of the most promising anode materials, with a theoretical capacity of up to 4200 mAh / g, which can meet the needs of higher energy density rechargeable batteries. However, silicon has drawbacks such as significant volume expansion and poor conductivity, resulting in poor cycle performance and rate performance in lithium-ion batteries using silicon as the anode material. Summary of the Invention

[0004] In view of the shortcomings of the prior art, this application provides a negative electrode material, a method for preparing the negative electrode material, and its application.

[0005] In a first aspect, this application provides a negative electrode material, the negative electrode material comprising:

[0006] The core, the material of which comprises boron-doped porous silicon-carbon; and

[0007] A covering layer that encloses the core, the covering layer comprising one or more layers;

[0008] The coating material includes one or more of solid electrolytes and heterostructured carbon.

[0009] Secondly, this application provides a method for preparing a negative electrode material, the method comprising the following steps:

[0010] Provide a core, the material of which comprises boron-doped porous silicon-carbon; and

[0011] A coating layer is formed on the surface of the core to obtain the negative electrode material;

[0012] The coating layer comprises one or more layers, and the material of the coating layer includes one or more of solid electrolytes and heterostructured carbon.

[0013] Thirdly, this application provides a negative electrode, which includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The material of the negative electrode active material layer includes the negative electrode material as described in the first aspect, or the material of the negative electrode active material layer includes the negative electrode material prepared by the method described in the second aspect.

[0014] Fourthly, this application provides a battery comprising a positive electrode and a negative electrode, wherein the negative electrode is as described in the third aspect.

[0015] This application provides a negative electrode material, a method for preparing the negative electrode material, and its application, which has the following technical effects:

[0016] In the negative electrode material of this application embodiment, the core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon has hierarchical pore size and excellent conductive network, which can improve the disadvantages of volume expansion and low conductivity of silicon materials, and enhance the rate and cycle performance of batteries using negative electrode materials.

[0017] The coating material includes one or more of solid electrolytes and heterostructured carbon. When the coating material includes a solid electrolyte, the high ionic conductivity and good electrical conductivity of the solid electrolyte further improve the conductivity of the negative electrode material. Furthermore, the solid electrolyte layer can, to some extent, suppress the volume expansion of silicon materials and improve the stability of the natural SEI film, reducing side reactions and mitigating silicon electrode pulverization. Through the synergistic effect of the core and the solid electrolyte layer, the volume expansion of silicon materials is further mitigated, thereby further enhancing the cycle performance of batteries using negative electrode materials.

[0018] When the coating material includes heterostructured carbon, the heterostructured carbon possesses a three-dimensional porous conductive cross-linked network structure, thereby endowing the coating with good flexibility, mechanical stability, and conductivity. Relying on the synergistic effect of the core and the heterostructured carbon layer, the drawbacks of volume expansion and low conductivity inherent in silicon materials are further mitigated, thus further enhancing the rate performance and cycle performance of batteries using negative electrode materials. Attached Figure Description

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments.

[0020] Figure 1 This is a schematic flowchart illustrating a method for preparing a negative electrode material according to an embodiment of this application.

[0021] Figure 2This is a schematic diagram of the structure of a negative electrode material provided in Material Embodiment 1 of this application, wherein A represents the core, B represents the intermediate layer, and C represents the outer layer. Detailed Implementation

[0022] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art, and the materials or reagents used in the embodiments and comparative examples of this application are commercially available. Furthermore, any methods and materials similar to or equivalent to those described herein may be used in this application. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0024] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Each embodiment of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0025] In the description of this application, the term "comprising" means "including but not limited to".

[0026] The terms “multiple,” “multiple times,” or similar expressions refer to two or more times, such as two, three, four, five, six, etc.

[0027] The term "and / or" encompasses any one of two or more of the listed items, as well as any and all combinations of the listed items. These combinations include any two listed items, any number of listed items, or a combination of all listed items. For example, "A and / or B" includes three parallel solutions: A, B, and A+B. Similarly, the technical solution "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (i.e., all connected by "logical OR"), any and all combinations of A, B, C, and D, including combinations of any two or three of A, B, C, and D, and combinations of all four of A, B, C, and D (i.e., all connected by "logical AND").

[0028] In this application, "solid electrolyte" refers to a material that can conduct ions (such as lithium ions) in a solid state, but hardly conducts electrons. In the embodiments of this application, the solid electrolyte can be a component present in a natural solid electrolyte interface (SEI) film.

[0029] In this application, "heterogeneous carbon" refers to a functionalized material formed by combining two or more carbon materials with different structures, morphologies, or chemical properties in a specific manner. It is understood that heterogeneous carbon can be prepared from two or more carbon sources with different structures, morphologies, or chemical properties. In the embodiments of this application, heterogeneous carbon can be prepared from a biomass carbon source and a resin carbon source.

[0030] In this application, "inert gas" refers to a class of gases that have stable chemical properties and do not readily react with other substances at room temperature and pressure, including but not limited to one or more of nitrogen, helium, neon, argon, krypton, and xenon.

[0031] This application provides an anode material comprising a core and a coating layer, wherein the coating layer encapsulates the core and comprises one or more layers. The core is made of boron-doped porous silicon-carbon, and the coating layer is made of one or more materials selected from solid electrolyte and heterostructured carbon.

[0032] In the negative electrode material of this application embodiment, the core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon has hierarchical pore size and excellent conductive network, which can improve the disadvantages of volume expansion and low conductivity of silicon materials, and enhance the rate and cycle performance of batteries using negative electrode materials.

[0033] Furthermore, the coating material includes one or more of solid electrolytes and heterostructured carbon. When the coating material includes a solid electrolyte, the high ionic conductivity and good electrical conductivity of the solid electrolyte further improve the conductivity of the negative electrode material. Moreover, the solid electrolyte layer can, to a certain extent, suppress the volume expansion of silicon materials and improve the stability of the natural SEI film, reducing side reactions and mitigating silicon electrode pulverization. Through the synergistic effect of the core and the solid electrolyte layer, the volume expansion of silicon materials is further mitigated, thereby further enhancing the cycle performance of batteries using negative electrode materials.

[0034] When the coating material includes heterostructured carbon, the heterostructured carbon possesses a three-dimensional porous conductive cross-linked network structure, thereby endowing the coating with good flexibility, mechanical stability, and conductivity. Relying on the synergistic effect of the core and the heterostructured carbon layer, the drawbacks of volume expansion and low conductivity inherent in silicon materials are further mitigated, thus further enhancing the rate performance and cycle performance of batteries using negative electrode materials.

[0035] In the negative electrode material of this application embodiment, the coating layer has a coating rate of not less than 50%, not less than 60%, not less than 70%, not less than 80%, not less than 90%, not less than 95%, or a coating rate of 100%, wherein the coating rate refers to the percentage of the outer surface area of ​​the core covered by the coating layer to the total outer surface area of ​​the core.

[0036] In some embodiments of this application, the coating layer has a single-layer structure, and the material of the coating layer includes a solid electrolyte or heterostructured carbon.

[0037] In other embodiments of this application, the coating layer includes an intermediate layer and an outer layer, the intermediate layer coating the core and the outer layer coating the intermediate layer, one of the intermediate layer and the outer layer being made of a solid electrolyte and the other being made of heterostructured carbon.

[0038] It should be noted that heterostructured carbon has better conductivity than solid electrolytes, but its ion mobility is lower than that of solid electrolytes. When the coating material includes both solid electrolyte and heterostructured carbon, it can combine the advantages of both, so that the conductivity and ion mobility of the negative electrode material are within a more suitable range, thereby further improving the rate performance of batteries using negative electrode materials.

[0039] Furthermore, when the intermediate layer material includes a solid electrolyte and the outer layer material includes heterostructured carbon, the rate performance of batteries using negative electrode materials can be significantly improved, and the cycle performance of batteries using negative electrode materials can be improved to a certain extent.

[0040] When the intermediate layer material includes heterostructured carbon and the outer layer material includes solid electrolyte, the cycle performance of batteries using negative electrode materials can be significantly improved, and the rate performance of batteries using negative electrode materials can be improved to a certain extent.

[0041] In some embodiments of this application, the core is in particle form, and the D50 particle size of the core is 0.8 μm to 3 μm, for example, it can be 0.98 μm to 3 μm, or 0.98 μm to 2.62 μm, with examples being 0.8 μm, 1 μm, 2 μm, 3 μm, or any two of the aforementioned values. Boron-doped porous silicon-carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides, and the silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0042] In some embodiments of this application, porous carbon includes one or more of biomass porous carbon, resin porous carbon, petroleum-based porous carbon, and coal-based porous carbon.

[0043] In some embodiments of this application, the solid electrolyte includes one or more of inorganic and organic substances. The inorganic substances include one or more of LiOH, Li2O, Li2CO3 and lithium aluminate, and the organic substances include one or more of R0OLi and R0OCO2Li. Each time R0 appears, it is independently selected from C1 to C10 alkyl groups, such as C1 to C8 alkyl groups, C1 to C6 alkyl groups, or C1 to C4 alkyl groups.

[0044] In some embodiments of this application, the pore size of the negative electrode material is 3.8 nm to 7.0 nm, for example, it can be 4.15 nm to 6.71 nm, such as 3.8 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 6.8 nm, 7 nm or any value between the two aforementioned values.

[0045] In some embodiments of this application, the D50 particle size of the negative electrode material is 5μm to 13μm, for example, it can be 5μm to 12.5μm, 7.4μm to 13μm, or 7.4μm to 12.5μm, with examples being 5μm, 7μm, 9μm, 11μm, 12.5μm or any value between the two aforementioned values.

[0046] In some embodiments of this application, the mass percentage of silicon in the negative electrode material is 27% to 40% of the total mass of the negative electrode material, for example, 27.3% to 39.3%; the mass percentage of boron in the negative electrode material is 0.55% to 1% of the total mass of the negative electrode material, for example, 0.59% to 0.99%; and the mass percentage of aluminum in the negative electrode material is 0% to 2.3% of the total mass of the negative electrode material, for example, 0% to 2.26% or 1.61% to 1.81%. The mass percentage of lithium in the total mass of the negative electrode material is 0% to 2.5%, for example, 0% to 2.41% or 1.69% to 1.97%; the mass percentage of carbon in the total mass of the negative electrode material is 52% to 65%, for example, 52.3% to 64.7%; and the mass percentage of oxygen in the total mass of the negative electrode material is 1.6% to 4.2%, for example, 1.68% to 4.11% or 3.58% to 4.11%. Under these conditions, the rate performance and cycle performance of the battery using the negative electrode material can be further balanced.

[0047] This application also provides a method for preparing a negative electrode material, which can be used to prepare any of the negative electrode materials described above, such as... Figure 1 As shown, the preparation method of the negative electrode material includes the following steps:

[0048] S1. Provides a core, the core material of which includes boron-doped porous silicon carbon;

[0049] S2. A coating layer is formed on the surface of the core to obtain the negative electrode material.

[0050] The coating layer comprises one or more layers, and the material of the coating layer includes one or more of solid electrolytes and heterostructured carbon. Boron-doped porous silicon-carbon, solid electrolytes, and heterostructured carbon are described above.

[0051] In some embodiments of this application, the kernel preparation method includes the following steps:

[0052] S11. Provide boron-doped porous carbon, mix the boron-doped porous carbon with a first silicon source and ball-mill to obtain a first composite material;

[0053] S12. In an inert gas atmosphere, using the first composite material as the deposition matrix, a second silicon source in gaseous form is introduced. The second silicon source decomposes to form silicon atoms, which are deposited on the first composite material to obtain the second composite material.

[0054] S13. The second composite material is subjected to plasma treatment to obtain the core.

[0055] The first silicon source is selected from one or more of elemental silicon and silicon oxides, and the second silicon source has the structure shown in the following general formula (Ⅰ):

[0056]

[0057] In general formula (I), R1, R2, R3, and R4 independently include hydrogen, deuterium, a halogen group, a C1-C10 aliphatic chain hydrocarbon group, a C1-C10 aliphatic chain hydroxyl group, or a combination of the aforementioned groups; wherein the halogen group is selected from -F, -Cl, -Br, or -I. The second silicon source includes, but is not limited to, one or more of dichlorosilane, trichlorosilane, tetrachlorosilane, tetraethoxysilane, and trimethylsilane.

[0058] In the above-mentioned core preparation method, silicon is secondary coated on a carbon matrix (boron-doped porous carbon) by combining ball milling and deposition, which improves the uniformity of silicon distribution on the carbon matrix. Furthermore, the addition of a plasma treatment step in the deposition process can improve the removal rate of impurities and further enhance the uniformity of silicon distribution on the carbon matrix.

[0059] In some embodiments of this application, the method for preparing boron-doped porous carbon includes the steps of: subjecting a raw material comprising biomass material, an oxidant and a boron source to a first heat treatment under an inert gas atmosphere to obtain boron-doped porous carbon.

[0060] The step of subjecting the raw materials, including biomass materials, oxidant, and boron source, to a first heat treatment can be carried out in a tube furnace. The biomass materials include, but are not limited to, one or more of algae, water hyacinth, duckweed, and hollow lotus, with algae including, but not limited to, one or more of cyanobacteria, green algae, and macroalgae. The oxidant includes, but is not limited to, potassium permanganate. The boron source includes, but is not limited to, one or more of boric acid and boranes, with boranes including, but not limited to, methaneborane, diborane, butyrateborane, pentyrateborane, hexylborane, decaborane, and trimethylborane. In the above method for preparing boron-doped porous carbon, using environmentally and water-sensitive biomass as the source of porous carbon offers advantages such as low cost, environmental friendliness, and renewability. Furthermore, the one-step process achieves pore formation in the carbon structure of the biomass material through the combined action of the oxidant and boron source, resulting in boron-doped porous carbon with hierarchical pore sizes and an excellent conductive network, overcoming the shortcomings of conventional biomass carbon, which suffers from single pore size and low conductivity.

[0061] In some embodiments of this application, the mass ratio of biomass material, oxidant and boron source in the raw materials is (1-4):(2-8):(1-4), for example (1-4):2:1, (1-4):4:1, (1-4):8:1, (1-4):4:1, (1-4):4:3, or (1-4):4:4. In this way, the boron content in boron-doped porous silicon carbon can be in a more suitable range, which can further improve the rate performance and cycle performance of batteries using negative electrode materials.

[0062] In some embodiments of this application, the mass percentage of boron in the boron-doped porous carbon is 1.29% to 1.6% of the total mass of the boron-doped porous carbon, which can be 1.29% to 1.54%, with examples being 1.29%, 1.34%, 1.4%, 1.45%, 1.5%, 1.54%, 1.6%, or any two of the aforementioned values; the mass percentage of carbon in the boron-doped porous carbon is 98% to 99%, which can be 98.2% to 98.6%, with examples being 98%, 98.2%, 98.4%, 98.4%, 98.6%, 98.8%, 99%, or any two of the aforementioned values.

[0063] In some embodiments of this application, the specific surface area of ​​boron-doped porous carbon is 2000 m². 2 / g~2300m 2 / g, can be 2033m 2 / g~2213m 2 / g, example is 2000m 2 / g、2100m 2 / g、2200m 2 / g、2300m 2 / g or any value between any two of the aforementioned values. The average pore size of the boron-doped porous carbon is 3.5 nm to 5 nm, which can be 3.57 nm to 4.45 nm, with examples being 3.5 nm, 4 nm, 4.5 nm, 5 nm, or any value between any two of the aforementioned values. The mesopore content of the boron-doped porous carbon is 49% to 66%, which can be 49.6% to 65.3%, with examples being 49%, 52%, 54%, 56%, 60%, 66%, or any value between any two of the aforementioned values.

[0064] In some embodiments of this application, the temperature of the first heat treatment is 200°C to 650°C, for example, it can be 200°C, 300°C, 400°C, 500°C, 600°C, 650°C or any two of the aforementioned values.

[0065] To further improve the pore-forming effect, in some embodiments of this application, the first heat treatment includes the steps of: heating the raw material to a third temperature, maintaining the temperature at the third temperature for 1 to 2 hours, and then heating it to a fourth temperature and maintaining the temperature at the fourth temperature for 2 to 4 hours, wherein the third temperature is 200°C to 300°C and the fourth temperature is 500°C to 650°C.

[0066] In some embodiments of this application, step S11 includes: sequentially passing the biomass material through a first drying process, a crushing process, a hydrochloric acid washing process, a deionized water washing process, and a second drying process to obtain a biomass precursor. The biomass precursor, potassium permanganate, and boric acid are mixed in a mass ratio of 2:4:2 and placed in a tube furnace under an argon atmosphere throughout. The temperature is first raised from room temperature to 250°C at a rate of 3°C / min, held at 250°C for 1.5 hours, then raised to 550°C at a rate of 5°C / min, held at 550°C for 3 hours, and then naturally cooled to room temperature to obtain boron-doped porous silicon carbon. The physicochemical parameters of the boron-doped porous silicon carbon obtained from different biomass materials are different, as shown in Table 1 below.

[0067] Table 1

[0068]

[0069] It should be noted that in Table 1, the content of a particular element refers to the percentage of that element's mass relative to the total mass of boron-doped porous silicon-carbon. For example, the carbon content refers to the percentage of carbon's mass relative to the total mass of boron-doped porous silicon-carbon. The elemental content can be determined using X-ray fluorescence spectrometry (XRF).

[0070] In some embodiments of this application, in the step of ball milling the boron-doped porous carbon and the first silicon source, the mass ratio between the boron-doped porous carbon and the first silicon source is 75:(35-45), for example, it can be 75:35, 75:38, 75:40, 75:42, 75:45 or any two of the aforementioned values. Under this condition, the silicon content in the boron-doped porous silicon carbon can be within a more suitable range. Under this condition, the volume expansion rate of the negative electrode in the battery using the negative electrode material is reduced, and it is beneficial to further improve the battery capacity.

[0071] In some embodiments of this application, in the step of ball milling the boron-doped porous carbon and the first silicon source, the ball milling speed is 450 r / min to 650 r / min, for example, it can be 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min or any two of the aforementioned values; the ball milling time is 7 h to 10 h, for example, it can be 7 h, 8 h, 9 h, 10 h or any two of the aforementioned values.

[0072] In order to further improve the uniformity of silicon distribution on the carbon matrix and to make the silicon content in the boron-doped porous silicon carbon within a more suitable range, in some embodiments of this application, in step S12, the deposition method is atomic layer deposition, the deposition is carried out at 200°C to 350°C, and the deposition cycle is 300 to 500 times.

[0073] In order to further improve the uniformity of silicon distribution on carbon matrix and the removal rate of impurities, in some embodiments of this application, in the plasma treatment in step S13, the plasma gas source includes hydrogen, the treatment temperature is 200℃~350℃, the working pressure is 50Pa~100Pa, and the power is 100W~180W.

[0074] In some embodiments of this application, when the coating layer is a single-layer structure, step S2 includes: forming a layer on the surface of the core containing a solid electrolyte to obtain the coating layer. Alternatively, when the coating layer is a single-layer structure, step S2 includes: forming a layer on the surface of the core containing a heterostructured carbon to obtain the coating layer.

[0075] In some other embodiments of this application, step S2 includes: forming an intermediate layer on the surface of the core, and then forming an outer layer on the surface of the intermediate layer to obtain a coating layer. Wherein, one of the intermediate layer and the outer layer is a layer whose material includes a solid electrolyte, and the other is a layer whose material includes heterostructured carbon.

[0076] Furthermore, in some embodiments of this application, the method for preparing the layer of material including solid electrolyte comprises the following steps:

[0077] S101. Provide a first solution including aluminum salt, mix the first solution and a first intermediate to obtain a first mixture, control the pH of the first mixture to be 3-4, let it stand, and obtain aluminate sol.

[0078] S102. A second solution comprising lithium salt is provided, and the second solution is mixed and reacted with aluminate sol to generate a precipitate, followed by solid-liquid separation to obtain the precipitate;

[0079] S103. Perform a second heat treatment on the precipitate to obtain a layer of material including a solid electrolyte.

[0080] The above describes the preparation of a material including a solid electrolyte layer using a solvent gel-assisted solution coprecipitation method. An artificial SEI film is uniformly deposited on the surface of the first intermediate. The artificial SEI film can suppress the volume expansion of silicon materials, improve the stability of the natural SEI layer, and reduce the occurrence of side reactions.

[0081] Wherein, when the coating layer is a single-layer structure, the coating layer is a layer whose material includes a solid electrolyte, and the first intermediate is the core. Alternatively, when the coating layer includes an intermediate layer and an outer layer, the intermediate layer is a layer whose material includes a solid electrolyte, and the outer layer is a layer whose material includes heterostructured carbon, and the first intermediate is the core. Alternatively, when the coating layer includes an intermediate layer and an outer layer, the intermediate layer is a layer whose material includes heterostructured carbon, and the outer layer is a layer whose material includes a solid electrolyte, and the first intermediate is an intermediate formed by the core and the intermediate layer, that is: the first intermediate consists of a core and an intermediate layer, with the intermediate layer coating the surface of the core.

[0082] In step S101, the aluminum salt includes one or more of aluminum halide, aluminum acetate, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum phosphate, and aluminum alkoxides. The aluminum halide includes one or more of aluminum chloride, aluminum bromide, and aluminum iodide, and the aluminum alkoxide includes one or more of aluminum methoxide, aluminum ethoxide, aluminum isopropoxide, aluminum n-butoxide, aluminum isobutoxide, aluminum tert-butoxide, and aluminum n-octanol.

[0083] In step S101, the solvent of the first solution includes water and one or more of C1 to C10 aliphatic alcohols, such as methanol, ethanol, ethylene glycol, propanol, glycerol and butanol.

[0084] In some embodiments of this application, the solvent of the first solution includes water and C1-C10 aliphatic alcohol compounds, and the mass ratio of aluminum salt, C1-C10 aliphatic alcohol compounds, and water in the first solution is (6-9):(50-62):(2.5-3.5), for example, it can be 6.5:50:2.9, 6.5:55:2.9, 6.5:62:2.9, 7:55:2.9, 8:55:2.9, 9:55:2.9, 6:55:2.5, or 6:55:3.5. Under these conditions, the dissolution of aluminum salt can be further promoted, thereby further improving the stability of the sol and further enhancing the interfacial contact between aluminum salt and the first intermediate.

[0085] In some embodiments of this application, the mixing of the first solution and the first intermediate is carried out at a temperature of 75°C to 80°C. The mixing of the first solution and the first intermediate can be carried out under stirring conditions, such as magnetic stirring, and the stirring speed can be, for example, 500 r / min to 600 r / min.

[0086] In some embodiments of this application, in step S101, the settling time is 20h to 36h, for example, it can be 20h, 24h, 28h, 30h, 32h, 36h or any range between the two aforementioned values.

[0087] In step S102, the lithium salt includes one or more of lithium halides, lithium nitrate, lithium acetate, lithium sulfate, lithium carbonate, lithium phosphate, and lithium alkoxides, wherein lithium halides include one or more of lithium chloride, lithium bromide, and lithium iodide, and lithium alkoxides include one or more of lithium methoxide, lithium ethanol, lithium isopropoxide, lithium n-butoxide, lithium isobutoxide, and lithium tert-butoxide.

[0088] The solvent of the second solution includes water and one or more of C1-C10 aliphatic alcohols. In some embodiments of this application, the solvent of the second solution includes C1-C10 aliphatic alcohols and water, and the mass ratio of lithium salt, C1-C10 aliphatic alcohols and water in the second solution is (35-45):(36-56):(8-19), for example, it can be 35:55:10, 35:50:15, 35:44:19, 45:47:8, or 40:52:8.

[0089] In step S102, the second solution and the aluminate sol can be mixed by adding the second solution dropwise into the aluminate sol at a rate of 0.4 mL / min to 1.5 mL / min.

[0090] In some embodiments of this application, in the mixing reaction of step S102, the ratio between the molar amount of aluminum in the aluminate sol and the molar amount of lithium in the second solution is 1:(1 to 1.7), for example, it can be 1:1, 1:1.3, 1:1.5, 1:1.7 or any range between the two aforementioned values.

[0091] To further improve the film quality of the solid electrolyte layer, in some embodiments of this application, the mixing reaction in step S102 is carried out at 55°C to 65°C for 2 to 4 hours, and the pH of the reaction system is controlled at 8 to 9 throughout the mixing reaction. The mixing reaction can be carried out under stirring conditions, such as magnetic stirring, with a stirring speed of 500 to 600 r / min.

[0092] In step S102, solid-liquid separation includes one or more of sedimentation, filtration, and thermal evaporation. Sedimentation includes, but is not limited to, one or more of gravity sedimentation, centrifugal sedimentation, and electromagnetic sedimentation. Filtration separation includes, but is not limited to, one or more of reverse osmosis, membrane filtration, nanofiltration, ultrafiltration, and microfiltration. As an example, solid-liquid separation includes filtration.

[0093] In some embodiments of this application, prior to the second heat treatment of the precipitate, the method for preparing the layer of material comprising a solid electrolyte further includes the steps of: repeatedly washing the precipitate obtained by solid-liquid separation with deionized water until neutral (pH 6.7–7.3), and then drying the precipitate. The drying process includes one or more of freeze-drying and supercritical CO2 drying.

[0094] In some embodiments of this application, in step S103, the temperature of the second heat treatment is 200°C to 300°C, for example, it can be 200°C, 220°C, 250°C, 270°C, 300°C, or a range between any two of the aforementioned values. The second heat treatment can be carried out in a tube furnace, and the duration of the second heat treatment can be 1 hour to 2 hours.

[0095] In some embodiments of this application, a method for preparing a layer of material comprising heterostructured carbon includes the steps of: providing a second mixture comprising a second intermediate and a coating agent, and calcining the second mixture. In the second mixture, the coating agent comprises a carbon source, and the mass ratio between the second intermediate and the coating agent is 100:(6-12), for example, it can be 100:6, 100:8, 100:10, 100:12, or a range between any two of the aforementioned values. Under this condition, the thickness of the layer comprising heterostructured carbon is within a more suitable range.

[0096] When the coating layer is a single-layer structure, the coating layer is a layer whose material includes heterostructured carbon, and the second intermediate is the core. Alternatively, when the coating layer includes an intermediate layer and an outer layer, the intermediate layer is a layer whose material includes heterostructured carbon, and the outer layer is a layer whose material includes a solid electrolyte, and the second intermediate is the core. Alternatively, when the coating layer includes an intermediate layer and an outer layer, the intermediate layer is a layer whose material includes a solid electrolyte, and the outer layer is a layer whose material includes heterostructured carbon, and the second intermediate is an intermediate formed by the core and the intermediate layer combined; that is, the second intermediate consists of a core and an intermediate layer, with the intermediate layer coating the surface of the core.

[0097] In some embodiments of this application, the coating agent includes a biomass carbon source and a resin carbon source, with a mass ratio of (2-4):(6-8), for example, 2:6, 2:8, 4:6, or 4:8. The heterostructured carbon layer prepared using this coating agent combines the strong flexibility of the biomass carbon source with the three-dimensional cross-linked porous rigid framework of the resin carbon source. Therefore, the heterostructured carbon layer exhibits good flexibility and mechanical stability, and possesses an excellent three-dimensional conductive network structure, further buffering the expansion stress of the silicon material during charging and discharging. Furthermore, the three-dimensional cross-linked porous rigid framework can further improve the rate performance of the battery.

[0098] In some embodiments of this application, the biomass carbon source includes one or more of lignin, cellulose, protein, amino acids, and starch. The resin carbon source includes one or more of phenolic resin, urea-formaldehyde resin, furfural resin, epoxy resin, and cashew nut shell resin.

[0099] Furthermore, in some embodiments of this application, the resin carbon source includes phenolic resin and a first resin, wherein the mass ratio between the phenolic resin and the first resin in the resin carbon source is 5:(2-5), for example, it can be 5:2, 5:3, 5:4, or 5:5, and the first resin includes one or more of urea-formaldehyde resin, furfural resin, epoxy resin, and cashew phenol resin. Under these conditions, the rate performance of the battery using the negative electrode material can be further improved.

[0100] To further improve the coating effect of heterostructured carbon, in some embodiments of this application, the preparation method of the second mixture includes the following steps:

[0101] S201. Disperse the second intermediate in a surfactant to obtain a dispersion;

[0102] S202. The dispersion and coating agent are placed in a fusion machine for fusion to obtain a second mixture.

[0103] In step S201, the surfactant includes one or more of hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dodecyldimethylbenzylammonium bromide, hexadecyldimethylbenzylammonium bromide, octadecyldimethylbenzylammonium bromide, and bis(C12-15)alkyldimethylammonium chloride. The mass ratio of the surfactant to the second intermediate is (2.5–4.5):100.

[0104] In step S202, the purpose of fusion is to modify the surface of the second intermediate and, under the action of strong shear force, make the coating agent adhere to the surface of the second intermediate, thereby improving the uniformity of coating and the density of particles.

[0105] In some embodiments of this application, the rotation speed of the fusion machine is 25 Hz to 40 Hz, and the fusion time is 6 h to 8 h.

[0106] In some embodiments of this application, the step of calcining the second mixture includes: heating the second mixture to a first temperature in an inert gas atmosphere, maintaining the temperature at the first temperature for 3 to 5 hours, then further heating to a second temperature and maintaining the temperature at the second temperature for 8 to 12 hours, wherein the first temperature is 150°C to 250°C and the second temperature is 650°C to 800°C. The calcination treatment can be carried out in a carbonization furnace, which can be a microwave carbonization furnace (microwave frequency of 2.5 GHz, power of 700W to 900W). The calcination treatment is a two-stage carbonization, wherein the first stage carbonization is used for the carbonization of the resin carbon source, and the second stage carbonization is used for the carbonization of the biomass carbon source.

[0107] This embodiment also provides a negative electrode, which includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The material of the negative electrode active material layer includes the negative electrode material as described above, or the material of the negative electrode active material layer includes the negative electrode material prepared by the method described above.

[0108] The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. It is understood that the negative electrode current collector includes a first surface and a second surface disposed opposite each other along its thickness direction, and at least one of the first surface and the second surface is provided with a negative electrode active material layer.

[0109] The materials for the negative electrode current collector include, but are not limited to, copper foil, composite copper foil, or copper mesh.

[0110] The negative electrode active material layer also includes a negative electrode binder and a negative electrode conductive agent. The negative electrode binder and negative electrode conductive agent can be materials commonly used in the art. Specifically, the negative electrode binder includes, but is not limited to, one or more of the following: styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, sodium alginate, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0111] The negative electrode conductive agent includes, but is not limited to, one or more of carbon black, graphite, graphene, carbon nanotubes, carbon fibers, superconducting carbon, and acetylene black.

[0112] The preparation method of the negative electrode may include the following steps: mixing and dispersing the negative electrode active material, negative electrode conductive agent, and negative electrode binder in a first dispersion medium to form a negative electrode slurry; then, coating the negative electrode slurry onto a negative electrode current collector, followed by a drying process and a rolling process to obtain the negative electrode. It should be noted that the negative electrode slurry can also be cast on a separate carrier to form a film layer, then the film layer is separated from the carrier, and then the film layer is stacked on the first surface and / or the second surface of the negative electrode current collector. The first dispersion medium includes, but is not limited to, one or more of N-methylpyrrolidone, acetone, and water.

[0113] This application also provides a battery, which includes a positive electrode and a negative electrode, wherein the negative electrode is as described above.

[0114] It should be noted that, based on their geometric features, the batteries in this application embodiment can be square batteries, cylindrical batteries, button batteries, or irregularly shaped batteries. Based on their packaging form, the batteries in this application embodiment can be pouch batteries or hard-case batteries. Based on their assembly form, the batteries in this application embodiment can be battery cells, battery modules, or battery packs. Based on their operating nature and storage method, the batteries in this application embodiment can be primary batteries, secondary batteries, or activated batteries.

[0115] In some embodiments of this application, the battery is a lithium-ion battery, which has both good fast-charging performance and high-temperature storage performance.

[0116] In the battery of this application embodiment, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. It is understood that the positive electrode current collector includes a third surface and a fourth surface disposed opposite to each other along its own thickness direction, and at least one of the third surface and the fourth surface is provided with a positive electrode active material layer.

[0117] The positive current collector is made of materials including, but not limited to, metal foil or composite current collector. Metal foil includes, but is not limited to, aluminum foil, platinum foil, or palladium foil. The composite current collector includes a substrate and a metal layer. The substrate includes a third surface and a fourth surface disposed opposite each other along its thickness direction. At least one of the third surface and the fourth surface has a metal layer. The substrate material includes, but is not limited to, one or more of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene. The metal layer material includes, but is not limited to, one or more of aluminum, platinum, palladium, nickel, titanium, and silver.

[0118] The positive electrode active material layer comprises a positive electrode active substance, a positive electrode binder, and a positive electrode conductive agent. The positive electrode active substance, positive electrode binder, and positive electrode conductive agent can be conventional materials in the art.

[0119] The positive electrode active material includes, but is not limited to, one or more of lithium cobalt oxide, lithium manganese oxide, lithium permanganate, lithium iron phosphate, lithium nickel oxide, lithium manganese phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. It is understood that the compounds listed above as positive electrode active materials may have a coating layer on their surface, and the coating layer material includes, but is not limited to, carbon materials.

[0120] The positive electrode binder includes, but is not limited to, one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0121] The positive electrode conductive agent includes, but is not limited to, one or more of carbon black, graphite, graphene, carbon nanotubes, carbon fibers, superconducting carbon, and acetylene black.

[0122] The preparation method of the positive electrode may include the following steps: mixing and dispersing the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder in a second dispersion medium to form a positive electrode slurry; then, coating the positive electrode slurry onto a positive electrode current collector, followed by a drying process and a rolling process to obtain the positive electrode. It should be noted that the positive electrode slurry can also be cast on a separate carrier to form a film layer, then the film layer is separated from the carrier, and then the film layer is stacked on the third and / or fourth surfaces of the positive electrode current collector. The first dispersion medium includes, but is not limited to, one or more of N-methylpyrrolidone, acetone, and water.

[0123] It should be noted that the battery in this embodiment may also include other conventional structures. For example, the battery in this embodiment may also include a separator disposed between the positive and negative electrodes. The separator may be a single-layer thin film or a composite membrane with a multi-layer structure. When the separator is a composite membrane, the materials of each layer in the composite membrane may be the same or different. The materials of the separator include, but are not limited to, one or more of glass fiber, non-woven fabric, polyester, Teflon, polyethylene, polypropylene, and polytetrafluoroethylene.

[0124] The electrolyte can be a conventional electrolyte in the art, comprising lithium salts and organic solvents. The organic solvents include, but are not limited to, one or more of ethylene carbonate, propylene carbonate, butyl carbonate, fluoroethylene carbonate, 1,4-butyrolactone, ethylene carbonate, propylene carbonate, propylene sulfite, propyl acetate, propyl propionate, methyl butyrate, butyl acetate, ethyl propionate, ethyl butyrate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The lithium salts include, but are not limited to, LiPF6, LiClO4, LiBF4, LiSbF6, LiAsF6, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiODFB, LiTFSI, LiFSI, LiCl, LiI, and LiN(C x F 2x+1 SO2)(C y F 2y+1 One or more of SO2, wherein x and y are integers from 1 to 20, and the mass percentage of lithium salt in the total mass of electrolyte can be 10% to 15%.

[0125] It should be noted that the positive electrode, negative electrode, and separator can be formed into a battery cell through a winding or stacking process. The electrolyte wets the positive and negative electrodes, and packaging one or more battery cells yields a single battery cell. The battery cell can be packaged using a rigid shell or a pouch. The rigid shell includes, but is not limited to, a metal shell or a plastic shell with high hardness. The pouch material includes, but is not limited to, one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0126] Battery cells can be assembled to form a battery module. Each battery module includes multiple battery cells arranged sequentially along a first direction and secured with fasteners. The first direction can be the length, width, or height of the battery module. It is understood that the battery module also has a housing for accommodating the multiple battery cells.

[0127] Battery modules can be assembled to form a battery pack, and each battery pack includes multiple battery modules. The battery pack also includes a housing for accommodating the multiple battery modules, which can be arranged sequentially along the length or width of the housing. Understandably, the battery pack also includes some conventional components, including but not limited to battery management systems, buffers, and cooling devices.

[0128] This application also provides an application of the aforementioned battery in electronic devices, electric vehicles, and energy storage systems. The electronic devices, electric vehicles, and energy storage systems respectively employ the aforementioned battery as a power source and / or energy storage component. The electronic devices include, but are not limited to, mobile phones, computers, digital cameras, camcorders, video game consoles, smart wearable devices, drones, Bluetooth speakers, wireless headphones, security equipment, medical equipment, and aerospace equipment. The electric vehicles include, but are not limited to, electric cars, electric motorcycles, electric bicycles, electric scooters, and electric balance scooters. The energy storage systems include, but are not limited to, home energy storage systems, solar energy storage systems, wind energy storage systems, and grid-connected energy storage power stations.

[0129] The technical solutions and effects of this application will be described in detail below through specific embodiments, comparative examples and experimental examples. The following embodiments are only some embodiments of this application and are not intended to limit this application.

[0130] Material Example 1

[0131] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0132] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0133] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon. The structural composition of the anode material is as follows: Figure 2 As shown.

[0134] The method for preparing the negative electrode material in this embodiment includes the following steps S1.1 to S1.4.

[0135] In step S1.1, cyanobacteria are sequentially subjected to a first drying process, a crushing process, a hydrochloric acid washing process, a deionized water washing process, and a second drying process to obtain a biomass precursor. The biomass precursor, potassium permanganate, and boric acid are mixed in a mass ratio of 2:4:2 and placed in a tube furnace under an argon atmosphere throughout. The temperature is first raised from room temperature to 250°C at a rate of 3°C / min and held at 250°C for 1.5 hours. Then, the temperature is raised to 550°C at a rate of 5°C / min and held at 550°C for 3 hours. After natural cooling to room temperature, boron-doped porous silicon carbon is obtained. In the boron-doped porous silicon carbon, the mass percentage of boron is 1.45%, the mass percentage of carbon is 98.4%, and the mass percentage of oxygen is 0.15%. The specific surface area of ​​the boron-doped porous carbon is 2076 m². 2 / g, the average pore size of boron-doped porous carbon is 4.45nm, the D50 particle size of boron-doped porous carbon is 6.5μm, and the mesoporous ratio of boron-doped porous carbon is 65.30%.

[0136] In step S1.2, the boron-doped porous carbon obtained in step S1.1 is mixed with powdered silicon dioxide at a mass ratio of 75:35 and ball-milled at a speed of 500 r / min for 8 h to obtain a first composite material. Subsequently, the first composite material is placed in an atomic layer deposition furnace at 300°C and an argon atmosphere. Using the first composite material as the deposition substrate, trimethylsilane gas is introduced, and the trimethylsilane gas decomposes to form silicon atoms which are deposited on the first composite material. The atomic layer deposition cycle is 450 times to obtain a second composite material. Next, the second composite material is subjected to plasma treatment. The plasma gas source is hydrogen, the treatment temperature is 300°C, the working pressure is 70 Pa, and the power is 150 W to obtain the core.

[0137] In step S1.3, aluminum isopropoxide, anhydrous ethanol, and deionized water are uniformly mixed at a mass ratio of 6.5:58:2.9 under conditions of 80°C water bath and magnetic stirring. The magnetic stirring speed is 550 r / min, and the stirring time is 4.5 h, to obtain the first solution. Take 800 mL of the first solution, add 80 g of the kernel, and then add 65% nitric acid aqueous solution to adjust the pH of the system to 3.5. Let it stand for 30 h to obtain aluminate sol. A second solution containing lithium salt was provided and added dropwise to an aluminate sol at 60°C at a rate of 1.2 mL / min until the molar ratio of aluminum in the aluminate sol to lithium in the second solution was 1:1.4. During the addition of the second solution, the pH of the system was controlled at 8.5 using 28% ammonia solution. The reaction was continued for 3 hours at 60°C with magnetic stirring (550 r / min) to obtain the reaction product. The reaction product was filtered and the filtrate was collected. The filtrate was repeatedly washed with deionized water until the pH of the filtrate reached 7, and then freeze-dried. The freeze-dried material was then placed in a tube furnace under an argon atmosphere and heated from room temperature to 250°C at a rate of 1°C / min, held at 250°C for 1 hour, and then naturally cooled to room temperature to obtain the intermediate.

[0138] The lithium salt in the second solution is lithium acetate, which accounts for 38% of the total mass of the second solution. The solvent of the second solution is composed of ethylene glycol and water, with ethylene glycol accounting for 45% of the total mass of the second solution, and the remainder being water.

[0139] In step S1.4, hexadecyltrimethylammonium bromide and the intermediate are mechanically mixed at a mass ratio of 3.5:100 to obtain a dispersion. The dispersion and the coating agent are placed in a fusion machine for fusion. In the dispersion, the mass ratio between the intermediate and the coating agent is 100:9.5. The fusion machine rotates at 35 Hz, and the fusion time is 8 h to obtain a second mixture. The second mixture is placed in a microwave carbonization furnace (2.5 GHz, 800 W) and heated to 200 °C under an argon atmosphere. After holding at 200 °C for 3.5 h, the temperature is further increased to 650 °C at a heating rate of 45 °C / min and held at 650 °C for 10 h. Then, the mixture is sieved to obtain the negative electrode material. The coating agent consists of lignin and a resin carbon source, with a mass ratio of lignin to resin carbon source of 3:7. The resin carbon source is prepared by mixing phenolic resin and furfural resin at a mass ratio of 5:3.

[0140] Material Example 2

[0141] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0142] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0143] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0144] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that the step S1.1, "mixing the biomass precursor, potassium permanganate and boric acid in a mass ratio of 2:4:2 and then placing it in a tube furnace", is replaced with "mixing the biomass precursor, potassium permanganate and boric acid in a mass ratio of 2:4:1 and then placing it in a tube furnace".

[0145] Material Example 3

[0146] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0147] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0148] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0149] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that the step S1.1, "mixing the biomass precursor, potassium permanganate and boric acid in a mass ratio of 2:4:2 and then placing it in a tube furnace", is replaced with "mixing the biomass precursor, potassium permanganate and boric acid in a mass ratio of 2:4:4 and then placing it in a tube furnace".

[0150] Material Example 4

[0151] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0152] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0153] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0154] Compared to the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that "trimethylsilane" in S1.2 is completely replaced with "trichlorosilane".

[0155] Material Example 5

[0156] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0157] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0158] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0159] Compared to the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that "the number of atomic layer deposition cycles is 450" in S1.2 is replaced with "the number of atomic layer deposition cycles is 550".

[0160] Material Example 6

[0161] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0162] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0163] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0164] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that the "aluminum isopropoxide, anhydrous ethanol and deionized water are uniformly mixed in a mass ratio of 6.5:58:2.9" in step S1.3 is replaced with "aluminum isopropoxide, anhydrous ethanol and deionized water are uniformly mixed in a mass ratio of 6.5:50:2.9".

[0165] Material Example 7

[0166] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0167] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0168] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0169] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that the phrase "aluminum isopropoxide, anhydrous ethanol and deionized water are uniformly mixed in a mass ratio of 6.5:58:2.9" in step S1.3 is replaced with "aluminum isopropoxide, anhydrous ethanol and deionized water are uniformly mixed in a mass ratio of 6.5:62:2.9".

[0170] Material Example 8

[0171] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0172] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0173] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0174] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that the "mass ratio between intermediate and coating agent is 100:9.5" in step S1.4 is replaced with "mass ratio between intermediate and coating agent is 100:6".

[0175] Material Example 9

[0176] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0177] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0178] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0179] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that the "mass ratio between intermediate and coating agent is 100:9.5" in step S1.4 is replaced with "mass ratio between intermediate and coating agent is 100:12".

[0180] Material Example 10

[0181] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0182] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0183] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0184] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that the "mass ratio between lignin and resin carbon source is 3:7" in step S1.4 is replaced with "mass ratio between lignin and resin carbon source is 3:6".

[0185] Material Example 11

[0186] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0187] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0188] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0189] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that the step S1.2, "mixing and ball-milling the boron-doped porous carbon obtained in step S1.1 with powdered silicon dioxide at a mass ratio of 75:35", is replaced with "mixing and ball-milling the boron-doped porous carbon obtained in step S1.1 with powdered silicon dioxide at a mass ratio of 75:45".

[0190] Material Example 12

[0191] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0192] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0193] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of a solid electrolyte, and the outer layer is made of heterostructured carbon.

[0194] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that the "resin carbon source is prepared by mixing phenolic resin and furfural resin in a mass ratio of 5:3" in step S1.4 is replaced with "resin carbon source is prepared by mixing phenolic resin and furfural resin in a mass ratio of 5:5".

[0195] Material Example 13

[0196] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0197] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0198] The coating layer is a single-layer structure, and the material of the coating layer includes heterostructured carbon.

[0199] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that step S1.3 is omitted, and the phrase "mechanically mix the intermediate with hexadecyltrimethylammonium bromide at a mass ratio of 3.5:100" in step S1.4 is replaced with "mechanically mix the core with hexadecyltrimethylammonium bromide at a mass ratio of 3.5:100".

[0200] Material Example 14

[0201] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0202] The core material includes boron-doped porous silicon carbon. Boron-doped porous silicon carbon includes silicon-containing materials and boron-doped porous carbon. The silicon-containing materials include one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing materials are distributed on the surface and in the internal pores of the boron-doped porous carbon.

[0203] The coating layer has a single-layer structure, and the material of the coating layer includes solid electrolyte.

[0204] Compared with the preparation method of the negative electrode material in Material Example 1, the difference in the preparation method of the negative electrode material in this example is that step S1.4 is omitted, and the intermediate obtained in step S1.3 is the negative electrode material of this example.

[0205] Material Example 15

[0206] This embodiment provides a negative electrode material and its preparation method. The negative electrode material of this embodiment includes a core and a coating layer, wherein the coating layer encapsulates the core.

[0207] In this embodiment, the core of the negative electrode material is the same as that of the negative electrode material in Material Example 1.

[0208] The coating layer consists of an intermediate layer and an outer layer. The intermediate layer coats the core, and the outer layer coats the intermediate layer. The intermediate layer is made of heterostructured carbon, and the outer layer is made of a solid electrolyte.

[0209] The method for preparing the negative electrode material in this embodiment includes the following steps S2.1 to S2.4.

[0210] Step S2.1 is the same as step S1.1 in Example 1.

[0211] Step S2.2 is the same as step S1.2 in Example 1.

[0212] In step S2.3, the core and hexadecyltrimethylammonium bromide are mechanically mixed at a mass ratio of 3.5:100 to obtain a dispersion. The dispersion and coating agent are placed in a fusion machine for fusion, wherein the mass ratio of the core to the coating agent in the dispersion is 100:9.5, the fusion machine speed is 35 Hz, and the fusion time is 8 h to obtain a second mixture. The second mixture is placed in a microwave carbonization furnace (2.5 GHz, 800 W), and under an argon atmosphere, the mixture is heated to 200 °C and held at 200 °C for 3.5 h. Then, the temperature is increased to 650 °C at a heating rate of 45 °C / min and held at 650 °C for 10 h. Then, the mixture is sieved to obtain an intermediate. The coating agent is composed of lignin and a resin carbon source, with a mass ratio of lignin to resin carbon source of 3:7. The resin carbon source is prepared by mixing phenolic resin and furfural resin at a mass ratio of 5:3.

[0213] Compared to step S1.3, the difference in step S2.4 is that "adding 80g of the core" in step S1.3 is replaced with "adding 80g of the intermediate obtained in step S2.3". The material obtained in step S2.4 is then sieved to obtain the negative electrode material of this embodiment.

[0214] Material Comparison Example 1

[0215] This comparative example provides a negative electrode material, which is powdered elemental silicon.

[0216] Material Comparison Example 2

[0217] This comparative example provides a negative electrode material, which is boron-doped porous carbon prepared in Material Example 1.

[0218] Material Comparison Example 3

[0219] This comparative example provides a negative electrode material, which is the core material prepared in Material Example 1.

[0220] Application Example 1

[0221] This embodiment provides a lithium-ion battery and its preparation method. The lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode and the negative electrode, and the electrolyte wets the positive electrode and the negative electrode.

[0222] The lithium-ion battery in this embodiment is a coin cell, in which a lithium metal sheet is used as the positive electrode. The separator is a composite membrane, which consists of a polyethylene membrane, a polypropylene membrane, and a polyethylene membrane stacked sequentially. The electrolyte is a 1 mol / L LiPF6 solution, and the solvent of the LiPF6 solution is prepared by mixing ethylene carbonate and dimethyl bicarbonate in a 1:1 volume ratio.

[0223] The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The negative electrode current collector is a copper foil (6 μm thick). The material of the negative electrode active material layer includes a negative electrode active substance, a negative electrode binder, and a negative electrode conductive agent. The negative electrode active substance is the negative electrode material in Material Example 1. The negative electrode binder includes styrene-butadiene rubber and sodium carboxymethyl cellulose. The negative electrode conductive agent is conductive carbon black Super-P.

[0224] The preparation method of the negative electrode includes the following steps: First, weigh the aforementioned four raw materials according to the mass ratio of negative electrode active material: styrene-butadiene rubber: sodium carboxymethyl cellulose: conductive carbon black Super-P of 95:1.5:1.5:1. Mix the aforementioned four raw materials with N-methylpyrrolidone to form a slurry. Then, use a coating machine to coat the negative electrode slurry onto the surface of copper foil, with a coating thickness of 150 μm and a compaction density of 1.60 g / cm³. 3 Then, it undergoes vacuum drying and roll pressing. The thickness of the negative electrode active material layer after roll pressing is 155μm, thus obtaining the negative electrode.

[0225] Application Examples 2-15

[0226] The lithium-ion battery in application example m is basically the same as the lithium-ion battery in application example 1, except that in application example m, the negative electrode active material of the negative electrode in the lithium-ion battery includes the negative electrode material in material example m, where m is a positive integer from 2 to 15.

[0227] Taking Application Example 2 as an example, the difference between the negative electrode in Application Example 1 and the negative electrode in Application Example 2 is that the negative electrode active material in the lithium-ion battery in Application Example 2 includes the negative electrode material in Material Example 2. Similarly, the difference between the negative electrode in Application Example 15 and the negative electrode in Application Example 15 is that the negative electrode active material in the lithium-ion battery in Application Example 15 includes the negative electrode material in Material Example 15.

[0228] Application Comparative Examples 1-3

[0229] The lithium-ion battery in Comparative Example n is basically the same as the lithium-ion battery in Application Example 1, except that in Comparative Example n, the negative electrode active material of the negative electrode in the lithium-ion battery includes the negative electrode material in Comparative Example n, where n is a positive integer from 1 to 3.

[0230] Experimental Example 1

[0231] The negative electrode materials in Material Examples 1 to 15 and Material Comparative Examples 1 to 3 were tested. The test items included: element content, core D50 particle size, D50 particle size of negative electrode material, pore size, conductivity and internal resistance.

[0232] The elemental content was determined using XRF, including the following steps: mixing and grinding 2±0.05g of stearic acid and 6±0.5g of the negative electrode material sample to be tested, then pressing the mixture into a tablet, and then performing XRF analysis. TM The test was conducted in 200 devices with a test pressure greater than 2 MPa.

[0233] The particle size of the anode material and its core were measured using a Malvern Panaco Zetasizer Ultra dynamic scattering particle size analyzer, and the D50 particle size of both the anode material and the core was calculated. The pore size of the anode material was measured using a Micron 3030 instrument. The conductivity of the anode material was measured using an Orion StarT instrument. Tm The conductivity of the A212 benchtop conductivity meter was measured at room temperature (25℃). The internal resistance of the negative electrode material was determined using the electrochemical impedance spectroscopy method (compacted density 1.65 g / cm³). 3 The test equipment was the Blue Electric System.

[0234] The elemental content of each negative electrode material is shown in Table 2 below:

[0235] Table 2

[0236]

[0237]

[0238] The measured data of D50 particle size, pore size, conductivity, and internal resistance of each negative electrode material are shown in Table 3 below:

[0239] Table 3

[0240]

[0241]

[0242] As shown in Table 3, compared with the negative electrode materials in Material Comparative Examples 1 to 3, the negative electrode materials in Material Examples 1 to 15 have higher conductivity and lower internal resistance.

[0243] This demonstrates that the core material, comprising boron-doped porous silicon-carbon, and the coating material, comprising one or more of solid electrolyte and heterostructured carbon, can improve the conductivity and reduce the internal resistance of the anode material. Boron-doped porous silicon-carbon possesses hierarchical pore sizes and an excellent conductive network, thereby enhancing the conductivity of the anode material.

[0244] When the coating material includes a solid electrolyte, the high ionic conductivity and good electrical conductivity of the solid electrolyte improve the conductivity of the anode material. When the coating material includes heterostructured carbon, the three-dimensional porous conductive cross-linked network structure of the heterostructured carbon further improves the conductivity of the anode material.

[0245] Experiment Example 2

[0246] The performance of the lithium-ion batteries in Application Examples 1 to 15 and Application Comparative Examples 1 to 3 was tested respectively.

[0247] The test conditions were as follows: charge and discharge at a current density of 0.5A / g to 5A / g, with the charging voltage limited to 0.005 to 2V; then, cycle performance was tested at a current density of 0.5A / g for 200 cycles.

[0248] During the testing process, the initial discharge specific capacity (FDSC, mAh / g) of each lithium-ion battery at a current density of 0.5 A / g, the initial discharge efficiency (FDE, %) of each lithium-ion battery at a current density of 0.5 A / g, the capacity retention rate (CR, %) of each lithium-ion battery after 200 cycles at a current density of 0.5 A / g, and the expansion rate (%) of the negative electrode of each lithium-ion battery after 200 cycles at a current density of 0.5 A / g were calculated.

[0249] Where, FDE = (First discharge specific capacity of lithium-ion battery at 0.5 A / g current density / First charge specific capacity of lithium-ion battery at 0.5 A / g current density) × 100%. CR@0.5A / g = Remaining discharge specific capacity of lithium-ion battery after 200 cycles at 0.5 A / g current density / First discharge specific capacity of lithium-ion battery at 0.5 A / g current density × 100%. Expansion rate (%) = Thickness of negative electrode of lithium-ion battery after 200 cycles at 0.5 A / g current density / Thickness of negative electrode during the first cycle × 100%.

[0250] The test results are shown in Table 4 below:

[0251] Table 4

[0252]

[0253]

[0254] As shown in Table 3, the batteries in Application Examples 1 to 15 exhibit better overall performance compared to Comparative Examples 1 to 3. Specifically, the batteries in Application Examples 1 to 15 demonstrate good rate performance and cycle performance, and the negative electrode of the batteries in Application Examples 1 to 15 has a lower expansion rate.

[0255] For the batteries in Application Examples 1 to 15, the FDE was above 93%, and the expansion rate of the negative electrode was below 15.3%. Except for Application Example 14, the CR of the batteries in the other application examples was above 86.8%, and the FDSC was above 1515 mAh / g. However, for the batteries in Comparative Examples 1 to 3, the FDE was below 90%, and the expansion rate of the negative electrode was above 16%.

[0256] This demonstrates that the coating material includes one or more of solid electrolytes and heterostructured carbon. By relying on the synergistic effect of the core and the coating, the shortcomings of silicon materials, such as volume expansion and low conductivity, can be improved, thereby further enhancing the rate performance and cycle performance of batteries using negative electrode materials.

[0257] When the coating layer includes an intermediate layer and an outer layer, one of which comprises a solid electrolyte and the other comprises heterostructured carbon, the rate performance and cycle performance of batteries using negative electrode materials can be further improved. The core, intermediate layer, and outer layer form a synergistic effect, which greatly improves the volume expansion defects and low conductivity defects of silicon materials, giving the battery excellent rate performance and cycle performance.

[0258] The foregoing has provided a detailed description of a negative electrode material, a method for preparing the negative electrode material, and its application, as provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in each of the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A negative electrode material, characterized in that, include: The core material comprises boron-doped porous silicon carbon; as well as A covering layer that encloses the core, the covering layer comprising one or more layers; The coating material includes one or more of solid electrolytes and heterostructured carbon.

2. The negative electrode material according to claim 1, characterized in that, The coating layer has a single-layer structure, and the material of the coating layer includes the solid electrolyte or the heterostructured carbon. Alternatively, the coating layer may include an intermediate layer and an outer layer, the intermediate layer covering the core and the outer layer covering the intermediate layer, wherein one of the intermediate layer and the outer layer is made of the solid electrolyte and the other is made of the heterostructured carbon.

3. The negative electrode material according to claim 1 or 2, characterized in that, The core is in particle form, and the D50 particle size of the core is 0.8μm to 3μm; The boron-doped porous silicon-carbon comprises silicon-containing material and boron-doped porous carbon. The silicon-containing material includes one or more of crystalline silicon, amorphous silicon, and silicon oxides. The silicon-containing material is distributed on the surface and in the internal pores of the boron-doped porous carbon.

4. The negative electrode material according to claim 1 or 2, characterized in that, The solid electrolyte comprises one or more of inorganic and organic substances, wherein the inorganic substances include one or more of LiOH, Li2O, Li2CO3 and lithium aluminate, and the organic substances include one or more of R0OLi and R0OCO2Li, wherein each occurrence of R0 is independently selected from C1 to C10 alkyl groups.

5. The negative electrode material according to claim 1 or 2, characterized in that, The pore size of the negative electrode material is 3.8 nm to 7.0 nm; The D50 particle size of the negative electrode material is 5μm to 13μm; In the negative electrode material, silicon accounts for 27% to 40% of the total mass of the negative electrode material, boron accounts for 0.55% to 1% of the total mass of the negative electrode material, aluminum accounts for 0% to 2.3% of the total mass of the negative electrode material, lithium accounts for 0% to 2.5% of the total mass of the negative electrode material, carbon accounts for 52% to 65% of the total mass of the negative electrode material, and oxygen accounts for 1.6% to 4.2% of the total mass of the negative electrode material.

6. A method for preparing a negative electrode material, characterized in that, The steps include: Provide a core, the material of which comprises boron-doped porous silicon-carbon; and A coating layer is formed on the surface of the core to obtain the negative electrode material; The coating layer comprises one or more layers, and the material of the coating layer includes one or more of solid electrolytes and heterostructured carbon.

7. The method for preparing the negative electrode material according to claim 6, characterized in that, The method for preparing the kernel includes the following steps: Boron-doped porous carbon is provided, and the boron-doped porous carbon is mixed with a first silicon source and ball-milled to obtain a first composite material. In an inert gas atmosphere, using the first composite material as the deposition matrix, a second silicon source in gaseous form is introduced. The second silicon source decomposes to form silicon atoms, which are then deposited on the first composite material to obtain the second composite material. as well as The second composite material is subjected to plasma treatment to obtain the core; Wherein, the first silicon source is selected from one or more of elemental silicon and silicon oxides, and the second silicon source has the structure shown in the following general formula (Ⅰ): In general formula (Ⅰ), R1, R2, R3 and R4 independently include hydrogen, deuterium, halogen group, C1 to C10 aliphatic chain hydrocarbon group, C1 to C10 aliphatic chain hydroxyl group, or a combination of the aforementioned groups; wherein the halogen group is selected from -F, -Cl, -Br or -I.

8. The method for preparing the negative electrode material according to claim 7, characterized in that, The method for preparing the boron-doped porous carbon includes the following steps: under an inert gas atmosphere, a raw material comprising biomass material, an oxidant and a boron source is subjected to a first heat treatment to obtain the boron-doped porous carbon; optionally, in the raw material, the mass ratio between the biomass material, the oxidant and the boron source is (1-4):(2-8):(1-4); The biomass materials include one or more of algae, water hyacinth, duckweed, and alligator weed; The oxidant includes potassium permanganate; The boron source includes one or more of boric acid and borane; In the boron-doped porous carbon, the mass percentage of boron is 1.29% to 1.6% of the total mass, and the mass percentage of carbon is 98% to 99% of the total mass; the specific surface area of ​​the boron-doped porous carbon is 2000 m². 2 / g~2300m 2 / g, wherein the average pore size of the boron-doped porous carbon is 3.5nm to 5nm, and the mesopore ratio of the boron-doped porous carbon is 49% to 66%; The temperature of the first heat treatment is 200℃~650℃.

9. The method for preparing the negative electrode material according to claim 7, characterized in that, In the step of ball milling the boron-doped porous carbon and the first silicon source, the mass ratio of the boron-doped porous carbon to the first silicon source is 75:(35-45), the ball milling speed is 450 r / min to 650 r / min, and the ball milling time is 7 h to 10 h. The second silicon source is selected from one or more of dichlorosilane, trichlorosilane, tetrachlorosilane, tetraethoxysilane, and trimethylsilane; In the step of using the first composite material as a deposition matrix, introducing a second silicon source in gaseous form, and having the second silicon source decompose to form silicon atoms that are deposited on the first composite material, the deposition method is atomic layer deposition, the deposition is carried out at 200°C to 350°C, and the deposition cycle is 300 to 500 times. In the plasma treatment, the plasma gas source includes hydrogen, the treatment temperature is 200℃~350℃, the working pressure is 50Pa~100Pa, and the power is 100W~180W.

10. The method for preparing the negative electrode material according to claim 6, characterized in that, When the coating layer is a single-layer structure, the step of forming the coating layer on the surface of the core includes: forming a layer on the surface of the core with the material comprising the solid electrolyte, thereby obtaining the coating layer; Alternatively, when the coating layer is a single-layer structure, the step of forming the coating layer on the surface of the core includes: forming a layer on the surface of the core with the material comprising the heterostructured carbon, thereby obtaining the coating layer; Alternatively, the step of forming a coating layer on the surface of the core may include: forming an intermediate layer on the surface of the core, and then forming an outer layer on the surface of the intermediate layer to obtain the coating layer; wherein one of the intermediate layer and the outer layer is a layer whose material includes the solid electrolyte, and the other is a layer whose material includes the heterostructured carbon.

11. The method for preparing the negative electrode material according to claim 10, characterized in that, The method for preparing the layer of the solid electrolyte material includes the following steps: A first solution comprising an aluminum salt is provided, the first solution and a first intermediate are mixed to obtain a first mixture, the pH of the first mixture is controlled to be 3-4, and the mixture is allowed to stand to obtain an aluminate sol. A second solution comprising lithium salt is provided, and the second solution and the aluminate sol are mixed and reacted to generate a precipitate, followed by solid-liquid separation to obtain the precipitate; as well as The precipitate is subjected to a second heat treatment to obtain a layer of material including the solid electrolyte; Wherein, when the coating layer is a single-layer structure, the coating layer is a layer of material including the solid electrolyte, and the first intermediate is the core; Alternatively, when the coating layer includes the intermediate layer and the outer layer, the intermediate layer is a layer whose material includes the solid electrolyte, and the outer layer is a layer whose material includes the heterostructured carbon, and the first intermediate is the core; Alternatively, when the coating layer includes the intermediate layer and the outer layer, the intermediate layer is a layer whose material includes the heterostructured carbon, and the outer layer is a layer whose material includes the solid electrolyte, and the first intermediate is an intermediate formed by the core and the intermediate layer.

12. The method for preparing the negative electrode material according to claim 11, characterized in that, The aluminum salt includes one or more of aluminum halide, aluminum acetate, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum phosphate, and aluminum alkoxides. The solvent of the first solution includes water and one or more of C1-C10 aliphatic alcohols. Optionally, the solvent of the first solution includes water and C1-C10 aliphatic alcohols. In the first solution, the mass ratio of the aluminum salt, the C1-C10 aliphatic alcohols, and the water is (6-9):(50-62):(2.5-3.5). The lithium salt includes one or more of lithium halides, lithium nitrate, lithium acetate, lithium sulfate, lithium carbonate, lithium phosphate, and lithium alkoxides. The solvent of the second solution includes water and one or more of C1-C10 aliphatic alcohols. Optionally, the solvent of the second solution includes C1-C10 aliphatic alcohols and water. In the second solution, the mass ratio of the lithium salt, the C1-C10 aliphatic alcohols, and the water is (35-45):(36-56):(8-19). In the step of mixing the second solution and the aluminate sol, the ratio between the molar amount of aluminum in the aluminate sol and the molar amount of lithium in the second solution is 1:(1-1.7); the mixing reaction is carried out at 55℃-65℃ for 2h-4h; and the pH of the reaction system is controlled at 8-9 throughout the entire mixing reaction process. The temperature of the second heat treatment is 200℃~300℃.

13. The method for preparing the negative electrode material according to claim 10, characterized in that, The method for preparing the material including the heterostructured carbon layer includes the steps of: providing a second mixture including a second intermediate and a coating agent, and calcining the second mixture; In the second mixture, the mass ratio of the second intermediate to the coating agent is 100:(6-12), and the coating agent includes a carbon source; When the coating layer is a single-layer structure, the coating layer is a layer of material including the heterostructured carbon, and the second intermediate is the core; Alternatively, when the coating layer includes the intermediate layer and the outer layer, the intermediate layer is a layer whose material includes the heterostructured carbon, and the outer layer is a layer whose material includes the solid electrolyte, and the second intermediate is the core; Alternatively, when the coating layer includes the intermediate layer and the outer layer, the intermediate layer is a layer whose material includes the solid electrolyte, and the outer layer is a layer whose material includes the heterostructured carbon, and the second intermediate is an intermediate formed by the core and the intermediate layer.

14. The method for preparing the negative electrode material according to claim 13, characterized in that, The coating agent comprises a biomass carbon source and a resin carbon source, wherein the mass ratio of the biomass carbon source to the resin carbon source is (2-4):(6-8); wherein the biomass carbon source comprises one or more of lignin, cellulose, protein, amino acids, and starch, and the resin carbon source comprises one or more of phenolic resin, urea-formaldehyde resin, furfural resin, epoxy resin, and cashew nut resin; optionally, the resin carbon source comprises phenolic resin and a first resin, wherein the mass ratio of the phenolic resin to the first resin in the resin carbon source is 5:(2-5), and the first resin comprises one or more of urea-formaldehyde resin, furfural resin, epoxy resin, and cashew nut resin; The method for preparing the second mixture includes the following steps: The second intermediate is dispersed in the surfactant to obtain a dispersion; and The dispersion and the coating agent are placed in a fusion machine for fusion to obtain the second mixture; Optionally, the rotation speed of the fusion machine is 25 Hz to 40 Hz, the fusion time is 6 h to 8 h, and the surfactant includes one or more of hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dodecyldimethylbenzylammonium bromide, hexadecyldimethylbenzylammonium bromide, octadecyldimethylbenzylammonium bromide, and bis(C12-15)alkyldimethylammonium chloride. The step of calcining the second mixture includes: heating the second mixture to a first temperature in an inert gas atmosphere, maintaining the temperature at the first temperature for 3 to 5 hours, then continuing to heat it to a second temperature and maintaining the temperature at the second temperature for 8 to 12 hours, wherein the first temperature is 150°C to 250°C and the second temperature is 650°C to 800°C.

15. A negative electrode, characterized in that, The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The material of the negative electrode active material layer includes the negative electrode material as described in any one of claims 1 to 5, or the material of the negative electrode active material layer includes the negative electrode material prepared by the method for preparing the negative electrode material as described in any one of claims 6 to 14.

16. A battery, characterized in that, The battery includes a positive electrode and a negative electrode, wherein the negative electrode is as described in claim 15.

Images