A niobium-based compound / silicon-carbon composite material, a preparation method and application thereof

Abstract

The application discloses a niobium-based compound / silicon-carbon composite material and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries.The composite material comprises a silicon-based material, a plurality of niobium-based compound particles anchored on the outer surface of the silicon-based material, and a carbon nano layer coated on the outer surfaces of the silicon-based material and the plurality of niobium-based compound particles.The composite material is realized by using a simple, convenient and industrialized production liquid phase method.The composite material obtained by the preparation method effectively alleviates the volume expansion of the silicon-based material and avoids the problem of niobium-based compound falling off, and when the composite material is applied to a lithium ion battery as a negative electrode material, excellent rate performance and cycle stability are exhibited.

Description

A niobium-based compound / silicon-carbon composite material, its preparation method and application Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode materials, specifically relating to a niobium-based compound / silicon-carbon composite material, its preparation method, and its application. Background Technology

[0002] With the increasing demand for battery energy density from electric vehicles, portable electronic devices, and large-scale energy storage systems, traditional graphite anodes (theoretically with a specific capacity of only 372 mAh·g) are becoming increasingly important. -1 The existing high-energy-density battery materials are gradually failing to meet the design requirements of future high-energy-density battery systems. Among many new anode materials, silicon (Si) is considered one of the most promising next-generation anode materials due to its extremely high theoretical specific capacity, moderate lithium intercalation potential, and abundant natural reserves. Large-scale application of silicon-based anodes could potentially drive a leap forward in the energy density of lithium-ion batteries. However, currently commercialized fourth-generation silicon-carbon anodes still face severe volume expansion during lithium intercalation, leading to electrode pulverization, separation of active material and current collector, and continuous damage to the solid electrolyte interphase (SEI) film. This results in poor cycle stability, low coulombic efficiency, and extremely poor rate performance. These inherent defects severely restrict the commercialization of silicon-carbon anodes.

[0003] Currently, some studies have been conducted on the modification of silicon-carbon anode materials. For example, niobium-based oxides are incorporated into silicon-carbon anode materials through mechanical composite methods. Alternatively, Chinese patent CN 120413631A discloses a method for preparing a modified desolvation layer silicon-carbon anode, which uses atomic layer deposition to coat the surface of the silicon-carbon anode material with an amorphous active metal oxide desolvation layer. This allows lithium ions to be rapidly desolvated on the coating surface and transported to the silicon particle surface, thereby improving the lithium ion transport capacity. However, this method has strict equipment requirements, complex process operations, and significantly increases production costs. Furthermore, it cannot achieve permanent fixation of niobium oxides, thus limiting its effect on improving the rate performance and cycle performance of the material. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention provides a niobium-based compound / silicon-carbon composite material. By anchoring the special structure of niobium-based oxide on the outer surface of silicon-based material through carbon nanolayers, the micropores on the surface of silicon-based particles are enriched. The resulting material has a low expansion rate and can effectively improve the electrical conductivity of niobium-based materials.

[0005] The second objective of this invention is to provide a method for preparing niobium-based compound / silicon-carbon composite materials. The preparation method of this invention is simple, convenient, and industrially feasible. It uses an organic carbon source to anchor niobium-based oxides onto the surface of silicon-based particles, overcoming the problem of niobium-based compound / silicon-carbon composite materials that fail during cycling obtained by traditional methods.

[0006] The third objective of this invention is to provide an application of a niobium-based compound / silicon-carbon composite material as a negative electrode material in lithium-ion batteries. The niobium-based oxide and special coating structure layer can significantly improve the overall cycle stability and coulombic efficiency of the material.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a niobium-based compound / silicon-carbon composite material, which includes a silicon-based material, a plurality of niobium-based compound particles anchored on the outer surface of the silicon-based material, and a carbon nanolayer coating the outer surface of the silicon-based material and the plurality of niobium-based compound particles.

[0008] The key to the significant improvement in rate performance and conductivity of the composite material lies in the synergistic effect between the special anchoring structure and the silicon-based material, niobium-based material, and carbon nanolayer components. Specifically, this invention achieves chemical anchoring between the niobium-based compound and the silicon-based material through a liquid-phase method, forming a strong chemical force at the interface between the two. This effectively suppresses the shedding of the niobium-based compound caused by the volume expansion and contraction of silicon during cycling, thereby maintaining a durable and stable interfacial contact between the fast ion conductor and the active material. Secondly, the niobium-based compound itself, as a fast ion conductor, provides an efficient lithium-ion migration channel; simultaneously, the multivalent state characteristics of niobium (possessing multiple redox couples Nb) further enhance its effectiveness. 5+ / Nb 4+ and Nb 4+ / Nb 3+ This significantly improves the battery's rate performance. Furthermore, the carbon nanotube coating on the outer surface of the niobium-based compound enhances its ionic conductivity. The carbon nanotube layer on the outside of the silicon-based material, on the one hand, restricts direct contact between silicon and the electrolyte, reducing side reactions; on the other hand, the organic carbon source forms numerous micropores during carbonization, enriching the microporous structure of the silicon-based material, effectively promoting electrolyte wetting and rapid lithium-ion transport, and aiding in the formation of a stable and dense SEI film in the early stages of cycling, further improving the material's rate performance. More importantly, the external carbon nanotube layer and niobium-based compound particles synergistically promote the generation of more LiF-containing solid electrolyte interfaces during cycling, forming a high-elastic-modulus SEI, thereby improving the overall cycle stability and coulombic efficiency of the material.

[0009] Furthermore, compared to the traditional flat coating structure, the coating morphology of the present invention is similar to the uneven distribution structure on the surface of a sesame ball. This structure allows the material of the present invention to have more lithium-ion diffusion paths. Lithium ions can travel from the carbon nanolayer to the silicon substrate, or from the carbon nanolayer to the niobium-based compound and then to the silicon substrate, or from the carbon nanolayer to the niobium-based compound and then to the silicon substrate, resulting in more, faster, and more stable lithium-ion transport paths, thereby significantly improving the rate performance of the material.

[0010] As a preferred embodiment, the silicon-based material includes at least one of pure silicon, silicon suboxide, and silicon-carbon anode powder; wherein the silicon-carbon anode powder is composed of porous carbon and a silicon matrix attached within the pores of the porous carbon. More preferably, the silicon-based material is silicon-carbon anode powder, thereby further reducing the expansion rate of the composite material.

[0011] As a preferred embodiment, the niobium-based compound particles are selected from at least one of niobium oxide, niobium tungstate, niobium titanate, molybdenum niobate, vanadium niobate, lithium niobate, potassium niobate, sodium niobate, heteroatom-doped niobium oxide, heteroatom-doped niobium tungstate, heteroatom-doped niobium titanate, heteroatom-doped molybdenum niobate, heteroatom-doped vanadium niobate, heteroatom-doped lithium niobate, heteroatom-doped sodium niobate, and heteroatom-doped potassium niobate.

[0012] Further, the heteroatom is at least one of Fe, Ti, V, Mo, W, Zn, Al, Cu and Mg; even further, the heteroatom doping amount is 0.01~10wt%.

[0013] As a preferred embodiment, the thickness of the carbon nanolayer is 1~30 nm. Within this range of carbon nanolayer thickness, the initial performance of the composite material can be guaranteed, while also improving the overall rate performance of the composite material.

[0014] This invention also provides a method for preparing a niobium-based compound / silicon-carbon composite material, the method comprising the following steps:

[0015] S1 involves mixing an organic carbon source with a solvent and then adding a niobium-based compound to obtain a blended slurry;

[0016] After adding silicon-based materials to the blended slurry described in S2 and mixing, the solvent is removed by heating to obtain precursor powder.

[0017] The precursor powder described in S3 is obtained by inert calcination;

[0018] The niobium-based compound has a particle size in the nanometer range, while the silicon-based material has a particle size in the micrometer range.

[0019] To achieve the aforementioned special anchoring structure in the preparation method of this invention, it is necessary to first mix the niobium-based compound with an organic carbon source solution. This utilizes the viscosity of the organic carbon source, allowing it to adhere to the surface of the niobium-based compound. Then, during the blending process with the silicon-based material, the particle size difference between the niobium-based compound and the silicon-based material causes the organic carbon source and the niobium-based compound coated with it to adhere to the surface of the silicon-based material. During the mixing process in S1, vigorous stirring at a speed of 800-1000 rpm is required to disperse the niobium-based compound particles and prevent their agglomeration.

[0020] As a preferred embodiment, the niobium-based compound has a particle size of 20-100 nm, and the silicon-based material has a particle size of 1-20 μm. Experiments have shown that smaller particle sizes of the niobium-based compound are more beneficial for improving the overall rate performance of the composite material. Further, the niobium-based compound has a particle size of 20-50 nm.

[0021] As a preferred embodiment, the organic carbon source includes at least one selected from asphalt, glucose, sucrose, citric acid, and phenolic resin; the solvent includes at least one selected from water, tetrahydrofuran, toluene, xylene, and carbon disulfide. The organic carbon sources selected in this invention can all form a liquid with a certain viscosity through a solvent, thereby achieving stable anchoring of niobium-based compounds. Further, the organic carbon source is asphalt, and the solvent is tetrahydrofuran.

[0022] As a preferred embodiment, the solid-liquid ratio of the organic carbon source to the solvent is 0.2 g: (20~30) mL. By controlling the solid-liquid ratio of the organic carbon source and the solvent, the system can have a suitable viscosity to coat the niobium-based compound.

[0023] As a preferred embodiment, the mass ratio of silicon-based material: organic carbon source: niobium-based compound is 100:(2~30):(2~30). In this invention, the organic carbon source serves as the medium connecting the silicon-based material and the niobium-based compound. Higher carbon source content results in better coating effects and facilitates the stable anchoring of niobium oxide on the surface of silicon-carbon particles. However, excessively high organic carbon source content can reduce the specific capacity of the anode material and affect the first-time efficiency of the composite material. Niobium-based compounds have high ionic conductivity; higher composite content leads to greater overall ionic conductivity of the composite material. However, due to the high potential plateau of niobium-based compounds, capacity reversibility is poor below 1V, and excessive amounts can negatively impact the first-time efficiency of the composite material.

[0024] Further, the mass ratio of silicon-based material: organic carbon source: niobium-based compound is 100:(6~15):(6~15); even further, the mass ratio of silicon-based material: organic carbon source: niobium-based compound is 100:12.5:12.5.

[0025] As a preferred embodiment, the mixing time after adding the niobium-based compound to S1 is 0.5~1h; the mixing time for S2 is 0.5~1h.

[0026] As a preferred embodiment, in S2, the heating temperature is 50~120℃ and the heating time is 5~12h.

[0027] As a preferred embodiment, the inert calcination conditions are: under an argon atmosphere, a heating rate of 5~10℃ / min. -1 The inert calcination is carried out at 500-900℃ for 1-3 hours. The purpose of this invention is mainly to carbonize the organic carbon source to form a carbon nanolayer for coating and anchoring the niobium-based compound.

[0028] Finally, this invention also provides an application of a niobium-based compound / silicon-carbon composite material as an anode material in lithium-ion batteries. The niobium-based compound / silicon-carbon composite material of this invention, as an anode material, not only utilizes the high lithium intercalation potential and excellent lithium-ion diffusion coefficient of the niobium-based compound, but also allows the niobium-based compound and the outer carbon nanolayer to synergistically regulate the microporous structure of the silicon-based particles and promote the formation of more LiF-containing solid electrolyte interfaces during cycling, thereby improving the ionic conductivity of the material and significantly enhancing the overall rate performance and cycle stability.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention coats the surface of silicon-based materials with carbon nanolayers by liquid phase method and heat treatment calcination, which not only avoids direct contact between the electrolyte and the silicon-based materials and inhibits the occurrence of side reactions between silicon and electrolyte, but also adjusts the pore structure of silicon-based materials by carbon nanolayers and niobium-based compounds, enriches the micro-mesopores on the surface of silicon-based material particles, and effectively improves the rate performance of the material.

[0031] (2) The present invention uses an organic carbon source to anchor niobium-based compounds on the surface of silicon-based material particles, avoiding contact failure caused by simple mechanical composite and improving the ionic conductivity of the material; in addition, a nanoscale carbon layer is coated on the surface of the niobium-based compound, which further improves the conductivity of the niobium-based compound.

[0032] (3) When the composite material of the present invention is used as a negative electrode material in lithium-ion batteries, it makes full use of the high lithium intercalation potential and fast lithium-ion diffusion coefficient of niobium-based compounds. When the battery system contains niobium, due to the multiple valence states of niobium, it has multiple redox pairs Nb 5+ / Nb 4+ and Nb 4+ / Nb 3+ This significantly improves the rate performance of the battery.

[0033] (4) The niobium-based compound / silicon-carbon composite material prepared by the present invention has a rich micro-mesoporous structure, which can promote the desolvation of lithium ions. The anchored niobium-based compound and carbon nanolayer work together to provide diffusion channels for the rapid conduction of lithium ions and promote the generation of more LiF-containing solid electrolyte interfaces during cycling, forming a high elastic modulus SEI, which effectively alleviates the volume expansion of silicon-based materials and thus improves the overall cycling stability and coulombic efficiency. Attached Figure Description

[0034] Figure 1 is a SEM image of the niobium-based compound / silicon-carbon composite material prepared in Example 1 of the present invention.

[0035] Figure 2 is a TEM image of the niobium-based compound / silicon-carbon composite material prepared in Example 1 of the present invention.

[0036] Figure 3 is an HRTEM image of the niobium-based compound / silicon-carbon composite material prepared in Example 1 of the present invention.

[0037] Figure 4 shows the first charge-discharge curves of Examples 1-2 and Comparative Examples 1-3 of the present invention.

[0038] Figure 5 shows the rate test results of a half-cell assembled from the niobium-based compound / silicon-carbon composite material prepared in Example 1 of this invention.

[0039] Figure 6 shows the rate test results of the half-cell assembled in Comparative Example 1 of the present invention. Detailed Implementation

[0040] To make the present invention easier to understand, specific embodiments are described below to further illustrate the invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Unless otherwise defined, the technical terms used below have the same meanings as understood by those skilled in the art; unless otherwise specified, the raw materials and reagents mentioned herein are commercially available or prepared by known methods.

[0042] In the embodiments of the present invention, unless otherwise specified, the chemical reagents used can be obtained by purchasing or by preparing them using existing methods, and the instruments and equipment used are conventional equipment in the prior art.

[0043] The following examples and comparative examples further illustrate this point.

[0044] Example 1

[0045] (1) A method for preparing a niobium-based compound / silicon-carbon composite material, comprising the following steps:

[0046] S1 dissolves 0.2g of asphalt in 20mL of tetrahydrofuran and stirs continuously until fully dissolved. Then, 0.2g of niobium oxide is added and stirred for 30min at a stirring speed of 900rpm to obtain a blended slurry.

[0047] S2 added 1.6g of commercial silicon-carbon anode powder (the silicon-carbon anode powder consists of porous carbon and a silicon matrix attached to the pores of the porous carbon, purchased from Shenghua New Materials Group Co., Ltd.) to the blended slurry, stirred for 1h to mix thoroughly, and then stirred at 50℃ until the solvent was completely evaporated. The resulting sample was then dried in a vacuum oven at 80℃ for 12h to obtain the precursor powder; wherein, the particle size of the commercial silicon-carbon anode powder of silicon-based compound is 8.5μm, and the particle size of niobium oxide is 50nm.

[0048] S3. The precursor powder is placed in a tube furnace, argon gas is introduced, and the mixture is heated at 5°C for 5 min. -1 The temperature was raised to 540℃ for carbonization treatment and held for 1 hour, then cooled to room temperature to obtain asphalt-coated niobium oxide / silicon carbon particle composite material.

[0049] (2) Electrochemical performance testing:

[0050] CR2016 half-cells were assembled in an argon-filled glove box. A slurry was prepared by dissolving 1g of asphalt-coated niobium oxide / silicon carbide particle composite material as the active material in 2ml of deionized water along with a conductive agent (SP) and binder (PAA) at a mass ratio of 90:5:5. This slurry was then uniformly coated onto copper foil to obtain the working electrode. The working electrode was dried in a vacuum oven at 80°C for 12 hours and then punched into 12mm discs. Lithium metal was used as the counter electrode, and a Celgard 2500 polypropylene membrane was used as the separator. The electrolyte was LX025 electrolyte purchased from Duoduo Reagent Network. The half-cells were tested using the Xinwei Battery Testing Platform, and their charge-discharge performance was tested within a voltage window of 0.01~2V.

[0051] Example 2

[0052] The only difference between this embodiment and Example 1 is that the amount of asphalt is replaced with 0.1g, the amount of niobium oxide is replaced with 0.1g, and the amount of commercial silicon carbide powder is replaced with 1.8g. All other steps and conditions are the same, and a niobium-based compound / silicon carbide composite material is obtained.

[0053] The electrochemical performance testing conditions and procedures are the same as in Example 1.

[0054] Example 3

[0055] The only difference between this embodiment and Example 1 is that the particle size of niobium oxide is replaced with 100 nm. All other steps and conditions are the same, resulting in a niobium-based compound / silicon-carbon composite material.

[0056] The electrochemical performance testing conditions and procedures are the same as in Example 1.

[0057] Example 4

[0058] The only difference between this embodiment and Example 1 is that the calcination temperature is replaced with 700℃, while the other steps and conditions are the same, resulting in a niobium-based compound / silicon-carbon composite material.

[0059] The electrochemical performance testing conditions and procedures are the same as in Example 1.

[0060] Comparative Example 1

[0061] The only difference between this comparative example and Example 1 is that the commercial silicon-carbon anode powder is not modified. Instead, an equal amount of commercial silicon-carbon anode powder is used as the active material, and the electrochemical performance is tested under the same conditions and steps as in Example 1.

[0062] Comparative Example 2

[0063] The only difference between this comparative example and Example 1 is that niobium oxide powder was not added, but 1.8g of commercial silicon-carbon anode powder was added. All other steps and conditions were the same, and the composite material was obtained.

[0064] The electrochemical performance testing conditions and procedures are the same as in Example 1.

[0065] Comparative Example 3

[0066] The only difference between this comparative example and Example 1 is that no asphalt is added. 0.2g of niobium oxide powder and 1.8g of commercial silicon carbide powder are added to 20mL of tetrahydrofuran and mixed thoroughly for 1h. The remaining steps and conditions are the same as in Example 1.

[0067] The electrochemical performance testing conditions and procedures are the same as in Example 1.

[0068] Comparative Example 4

[0069] The only difference between this comparative example and Example 1 is that the niobium oxide powder and the commercial silicon carbide powder are added simultaneously instead of in steps; all other steps and conditions are the same.

[0070] The results show that the silicon-carbon powder and niobium-based compound in the obtained composite material are distributed in a blended form, rather than the niobium oxide anchored on the surface of the silicon-carbon powder as in the present invention.

[0071] Table 1 shows the electrochemical performance test results of the composite materials prepared in the embodiments and comparative examples of the present invention as negative electrode active materials applied to lithium-ion batteries.

[0072]

[0073] Table 2 shows the cycle performance test results of the composite materials prepared in Example 1 and Comparative Example 1 as negative electrode active materials in lithium-ion batteries.

[0074]

[0075] Performance test results analysis:

[0076] As shown in Figure 1, in Example 1 of the present invention, the surface of the sample particles becomes smooth after being coated with asphalt, and niobium oxide is attached to the surface of silicon carbon particles with a size at the micro-nano level.

[0077] As shown in Figure 2, in the TEM test of Example 1 of this invention, an amorphous carbon layer formed by the carbonization of pitch exists between niobium oxide, silicon carbide, and pitch. Pitch-derived carbon anchors the niobium oxide particles on the surface of silicon carbide particles, while the amorphous carbon layer also coats the surface of silicon carbide. This non-mechanical connection is not easily detached during cycling. The HRTEM in Figure 3 proves that the surface of the niobium oxide particles has a nanoscale carbon layer, all of which are beneficial to improving the overall electrochemical performance. The thickness of the carbon nanolayer is 5~10 nm.

[0078] As shown in Table 1 and Figure 4, the introduction of carbon partially reduces the initial efficiency of the material. This is because the carbon coating slightly increases the specific surface area, increasing electrolyte consumption after the first cycle. Additionally, the niobium-based compound exhibits irreversible lithium insertion at discharge to 0.01V, leading to a decrease in initial efficiency. However, under 3C charge-discharge conditions, the discharge specific capacities of Examples 1-4 and Comparative Examples 1-3 were 701 mAh / g, 676 mAh / g, 605 mAh / g, 553 mAh / g, 289 mAh / g, 620 mAh / g, and 395 mAh / g, respectively. Example 1 of this invention exhibits the best rate performance, indicating that the combination of carbon coating and niobium oxide improves the rate performance of the silicon-based anode.

[0079] As shown in Figure 5, the rate performance of the niobium oxide / silicon carbon particle composite material coated with asphalt in Example 1 of the present invention is significantly improved. It still has a high discharge specific capacity of 425mAh / g under 4C charge and discharge conditions, and the capacity retention rate can reach 30.4% compared with 0.2C charge and discharge conditions.

[0080] As shown in Figure 6, the discharge specific capacity of Comparative Example 1 of the present invention is 95 mAh / g under 4C charge-discharge conditions, while the capacity retention rate is only 6.0% under 0.2C charge-discharge conditions.

[0081] As shown in Table 2, Example 1 of the present invention can stably cycle 100 times under 3C charge-discharge conditions, and the capacity retention rate after 100 cycles is 84.9%. Comparative Example 1 of the present invention has extremely poor high-rate charge-discharge performance, and has extremely low capacity under 3C charge-discharge conditions, with a capacity retention rate of only 18.3% after 100 cycles.

[0082] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A niobium-based compound / silicon-carbon composite material, characterized in that: The composite material comprises a silicon-based material, several niobium-based compound particles anchored on the outer surface of the silicon-based material, and a carbon nanolayer coating the outer surface of the silicon-based material and the several niobium-based compound particles. The preparation method of the niobium-based compound / silicon-carbon composite material includes the following steps: S1, mixing an organic carbon source with a solvent and then adding a niobium-based compound to obtain a blended slurry; S2, adding a silicon-based material to the blended slurry and mixing, then heating to remove the solvent to obtain a precursor powder; S3, subjecting the precursor powder to inert calcination to obtain the final product; the niobium-based compound has a particle size of 20~100nm, and the silicon-based material has a particle size of 1~20μm.

2. The niobium-based compound / silicon-carbon composite material according to claim 1, characterized in that: The silicon-based material includes at least one of pure silicon, silicon suboxide, and silicon-carbon anode powder; wherein the silicon-carbon anode powder is composed of porous carbon and a silicon matrix attached to the pores of the porous carbon.

3. The niobium-based compound / silicon-carbon composite material according to claim 1, characterized in that: The niobium-based compound particles are selected from at least one of niobium oxide, niobium tungstate, niobium titanate, molybdenum niobate, vanadium niobate, lithium niobate, potassium niobate, sodium niobate, heteroatom-doped niobium oxide, heteroatom-doped niobium tungstate, heteroatom-doped niobium titanate, heteroatom-doped molybdenum niobate, heteroatom-doped vanadium niobate, heteroatom-doped lithium niobate, heteroatom-doped sodium niobate, and heteroatom-doped potassium niobate.

4. A niobium-based compound / silicon-carbon composite material according to claim 2 or 3, characterized in that: The thickness of the carbon nanolayer is 1~30nm.

5. The niobium-based compound / silicon-carbon composite material according to claim 1, characterized in that: The organic carbon source includes at least one of asphalt, glucose, sucrose, citric acid, and phenolic resin; the solvent includes at least one of water, tetrahydrofuran, toluene, xylene, and carbon disulfide.

6. The niobium-based compound / silicon-carbon composite material according to claim 5, characterized in that: The mass ratio of silicon-based material: organic carbon source: niobium-based compound is 100:(2~30):(2~30); the solid-liquid ratio of organic carbon source to solvent is 0.2g:(20~30)mL.

7. The niobium-based compound / silicon-carbon composite material according to claim 6, characterized in that: The conditions for inert calcination are as follows: under an argon atmosphere, the heating rate is 5~10℃min-1, and calcination is carried out at 500~900℃ for 1~3h.

8. An application of the niobium-based compound / silicon-carbon composite material as described in any one of claims 1 to 4, characterized in that: It is used as a negative electrode material in lithium-ion batteries.

Images