Metal / heteroatom co-doped silicon carbon negative electrode material and preparation method and application thereof

Abstract

The invention provides a metal / heteroatom co-doped silicon carbon negative electrode material as well as a preparation method and application thereof, and belongs to the technical field of lithium ion battery materials. The metal compound and heteroatoms are uniformly distributed on the porous carbon substrate in an in-situ growth doping manner, so that the electron conductivity of the material is improved, the diffusion rate of lithium ions in the material and on an interface is also improved, and the reaction kinetics of the silicon-carbon negative electrode material is further synergistically improved. Meanwhile, the prepared silane deposited silicon-carbon negative electrode material has good conductivity, high structural stability and long cycle life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to a metal / heteroatom co-doped silicon-carbon anode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and low self-discharge rate, have become the core power source for portable electronic devices, electric vehicles, and large-scale energy storage systems. However, currently commercial lithium-ion batteries mainly use graphite-based materials as anodes, which have relatively low theoretical specific capacity, making it difficult to meet the needs of next-generation high-energy-density batteries. Although Si materials possess a theoretical specific capacity as high as 4200 mAh / g, the huge volume expansion (approximately 300%) that occurs during charging and discharging severely damages the structural stability and cycle performance of the electrode, greatly restricting its commercialization and application. To address the aforementioned shortcomings of Si-based anodes, researchers have adopted a silicon-carbon (Si / C) composite material strategy for modification. In particular, silicon-carbon anode materials with porous carbon as the framework, which uniformly load nano-silicon into the porous structure using chemical vapor deposition technology, have received extensive research attention due to their ability to significantly reduce the volume expansion rate of silicon.

[0003] Currently, deposited silicon-carbon anode materials still suffer from poor conductivity, slow reaction kinetics, and poor interfacial stability. A common approach is to modify the porous carbon substrate by doping with non-metallic heteroatoms or introducing metallic elements / metal compounds to improve the conductivity and interfacial stability of the composite material. However, single-doping strategies have significant limitations in optimizing material performance; they lack multiphase synergy and cannot simultaneously address core issues such as electron / ion transport rates and interfacial stability in silicon-carbon anodes. Furthermore, some doping processes are relatively complex, and the uneven distribution of heteroatoms or metals / metal compounds in porous carbon can easily induce preferential nucleation and localized agglomeration during silicon deposition, thereby compromising the uniformity and stability of the material structure.

[0004] Therefore, it is still necessary to explore efficient processing methods to improve the kinetic defects of silicon-carbon anodes and simultaneously improve the interfacial and structural stability of the materials, so as to achieve the excellent electrochemical performance of novel silicon-carbon anode materials. Summary of the Invention

[0005] The purpose of this invention is to provide a metal / heteroatom co-doped silicon-carbon anode material, its preparation method, and its application, which can improve the kinetic defects of silicon-carbon anodes and enhance the interfacial and structural stability of the material.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a metal / heteroatom co-doped silicon-carbon composite material, comprising the following steps: A carbon source, activator, metal salt, nitrogen source, phosphorus source and water are mixed and complexed to obtain a precursor; The precursor is carbonized to obtain multiphase doped porous carbon. Under protective gas conditions, silane gas is introduced into the multiphase doped porous carbon for vapor deposition, followed by the introduction of carbon source gas for carbon coating, to obtain a metal / heteroatom co-doped silicon-carbon composite material.

[0007] Preferably, the carbon source includes one of ethylenediaminetetraacetic acid (EDTA) or EDTA salts.

[0008] Preferably, the activator includes one of potassium hydroxide, sodium hydroxide, and potassium carbonate; the mass ratio of the activator to the carbon source is 1:1 to 3.

[0009] Preferably, the metal salt includes one or more of nickel nitrate, iron nitrate, cobalt nitrate, molybdate, tungstate, and vanadate; the mass ratio of the metal salt to the carbon source is 1:3 to 10.

[0010] Preferably, the nitrogen source includes one or more of melamine, dicyandiamide, and urea; the phosphorus source includes phosphate; the mass ratio of the carbon source to the nitrogen source is 1:0.2~2, and the mass ratio of the carbon source to the phosphorus source is 1:0.2~1.

[0011] Preferably, the carbonization temperature is 700~1000℃ and the time is 2~10h; the carbonization atmosphere is one or more of nitrogen, argon and helium.

[0012] Preferably, the protective gas includes one or more of nitrogen, argon, and helium, and the silane gas includes one or two of silane and disilane. The flow ratio of the silane gas to the protective gas is 1:1 to 10. The temperature of the vapor deposition is 500 to 1000°C, and the time is 2 to 24 hours.

[0013] Preferably, the carbon source gas includes one or more of methane, ethane, propane, acetylene, and propyne, and the flow ratio of the carbon source gas to the protective gas is 1:1 to 10; the carbon coating temperature is 500 to 1000°C, and the time is 2 to 24 hours.

[0014] The present invention provides a metal / heteroatom co-doped silicon-carbon composite material prepared by the preparation method described above, wherein the Si content is 10~80wt%, the carbon content is 10~80wt%, and the metal compound content is 1~10wt%.

[0015] This invention provides the application of the metal / heteroatom co-doped silicon-carbon composite material described above in lithium-ion battery anode materials.

[0016] This invention provides a method for preparing a metal / heteroatom co-doped silicon-carbon composite material. This method, through in-situ growth and doping, uniformly distributes metal compounds and heteroatoms onto a porous carbon substrate. This not only improves the electronic conductivity of the material but also enhances the diffusion rate of lithium ions within the material and at the interface, thereby synergistically improving the reaction kinetics of the silicon-carbon anode material. Simultaneously, the prepared silane-deposited silicon-carbon anode material exhibits excellent conductivity, high structural stability, and long cycle life.

[0017] Specifically, the present invention has the following advantages: 1) Multiple heteroatom-doped porous carbon serves as a substrate, improving the conductivity of the material and the uniformity of silicon deposition; the porous carbon framework serves as a silane deposition substrate, and its rich pore structure can effectively suppress expansion, thereby achieving structural stability; the porous carbon modified with embedded metal compounds can strongly anchor silicon nanoparticles, achieving interface stability, thus jointly improving the interface and structural stability of silicon-carbon materials.

[0018] 2) The embedding of multiple metal compounds into porous carbon to construct a continuous conductive network is beneficial to enhancing the overall conductivity of the material; at the same time, it accelerates the lithium-ion diffusion rate, promotes the uniform insertion and extraction of lithium ions, and improves the reaction kinetics of silicon-carbon anode.

[0019] 3) The carbon skeleton has a rich porous structure, in which micropores can store silicon particles and provide expansion space, while mesopores can provide transport channels for lithium-ion diffusion; in addition, carbon coating by vapor deposition can alleviate the volume expansion of silicon, thereby ensuring good cycle life of silicon-carbon anode materials. Attached Figure Description

[0020] Figure 1 This is a flowchart of the preparation method of the metal / heteroatom co-doped silicon-carbon composite material of the present invention; Figure 2 This is a schematic diagram of the structure of the metal / heteroatom co-doped silicon-carbon composite material of the present invention. Detailed Implementation

[0021] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0022] This invention provides a method for preparing a metal / heteroatom co-doped silicon-carbon composite material, comprising the following steps: A carbon source, activator, metal salt, nitrogen source, phosphorus source and water are mixed and complexed to obtain a precursor; The precursor is carbonized to obtain multiphase doped porous carbon. Under protective gas conditions, silane gas is introduced into the multiphase doped porous carbon for vapor deposition, followed by the introduction of carbon source gas for carbon coating, to obtain a metal / heteroatom co-doped silicon-carbon composite material.

[0023] In this invention, the carbon source preferably includes one of ethylenediaminetetraacetic acid (EDTA) and EDTA salts; the EDTA salt is preferably disodium EDTA. In this invention, the carbon source also functions as a chelating agent.

[0024] In this invention, the activator preferably includes one of potassium hydroxide, sodium hydroxide, and potassium carbonate; the mass ratio of the activator to the carbon source is preferably 1:1 to 3, more preferably 1:1.5 to 2.5, and even more preferably 1:2.

[0025] In this invention, the metal salt preferably includes one or more of nickel nitrate, iron nitrate, cobalt nitrate, molybdate, tungstate, and vanadate; when the metal salt is two or more of the above, there is no special limitation on the ratio of different metal salts, and any ratio is acceptable; the molybdate is preferably ammonium molybdate; the tungstate is preferably ammonium tungstate; and the vanadate is preferably ammonium vanadate; the mass ratio of the metal salt to the carbon source is preferably 1:3 to 10, more preferably 1:4 to 8. This invention utilizes the metal salt as a chelating agent ligand.

[0026] In this invention, the nitrogen source preferably includes one or more of melamine, dicyandiamide, and urea; the mass ratio of the carbon source to the nitrogen source is 1:0.2~2, more preferably 1:0.5~1.25, and even more preferably 1:1.

[0027] In this invention, the phosphorus source preferably includes phosphate, and the phosphate is preferably sodium phosphate dodecahydrate; the mass ratio of the carbon source to the phosphorus source is 1:0.2~1, more preferably 1:0.25~0.75.

[0028] In this invention, carbon source, activator, metal salt, nitrogen source, and phosphorus source are preferably added to water and stirred to form a liquid-phase mixture, which is then dried to obtain the precursor. This invention does not have a special limitation on the amount of water used, as long as the materials are mixed evenly. The drying method is preferably drying in a forced-air drying oven at 60~120℃, more preferably at 80~100℃.

[0029] In this invention, the complexation time is preferably 1 to 4 hours, more preferably 1 to 2 hours.

[0030] In this invention, the carbonization temperature is preferably 700~1000℃, more preferably 750~850℃, and the time is preferably 2~10h, more preferably 2~6h. The carbonization atmosphere is preferably one or more of nitrogen, argon, and helium. When the carbonization atmosphere is two or more of the above, there is no special limitation on the ratio of different atmospheres, and any ratio is acceptable. During the carbonization process, the pyrolysis of the complex in the precursor releases a large amount of gases such as NH3, CO, CO2, NO2, and NO. These substances can not only act as foaming agents to form carbon foam, but the reducing gases in them also promote the formation of metal compounds.

[0031] The present invention preferably involves carbonization in an atmosphere furnace, followed by cooling in the furnace, and then washing and drying the resulting carbonization product to obtain multiphase doped porous carbon (i.e., metal compound / heteroatom doped porous carbon). The washing is preferably performed sequentially with hydrochloric acid, ethanol, and pure water for washing and filtration. The mass concentration of the hydrochloric acid is preferably 4-8%, more preferably 5-7%, and even more preferably 6%. The drying is preferably performed in a forced-air drying oven at 60-120°C, more preferably 80-100°C.

[0032] In this invention, the protective gas preferably includes one or more of nitrogen, argon, and helium; the silane gas preferably includes one or two of silane and disilane; the flow rate ratio of the silane gas to the protective gas is preferably 1:1 to 10, more preferably 1:5 to 10; the flow rate of the silane gas is preferably 1 to 10 L / min, more preferably 2 to 6 L / min; the temperature of the vapor deposition is preferably 500 to 1000°C, more preferably 500 to 800°C, and the time is preferably 2 to 24 h, more preferably 5 to 20 h.

[0033] In this invention, the carbon source gas preferably includes one or more of methane, ethane, propane, acetylene, and propyne; the flow ratio of the carbon source gas to the protective gas is preferably 1:1 to 10, more preferably 1:5 to 10; the flow rate of the carbon source gas is preferably 1 to 8 L / min, more preferably 3 to 6 L / min, and even more preferably 2 to 6 L / min; the carbon coating temperature is preferably 500 to 1000℃, more preferably 500 to 800℃, and the time is preferably 2 to 24 h, more preferably 5 to 12 h.

[0034] like Figure 2 As shown, the present invention provides a metal / heteroatom co-doped silicon-carbon composite material prepared by the preparation method described above, wherein the Si content is 10~80wt%, preferably 20~60wt%, more preferably 30~50wt%, the carbon content is 10~80wt%, preferably 20~60wt%, more preferably 30~47wt%, and the metal compound content is 1~10wt%, preferably 2~8wt%, more preferably 3~5wt%.

[0035] In the metal / heteroatom co-doped silicon-carbon composite material of the present invention, the metal compound is formed by a corresponding metal salt and a nitrogen source or a phosphorus source, preferably including one or more of nickel phosphide, iron phosphide, cobalt phosphide, molybdenum carbide, tungsten nitride and vanadium carbide.

[0036] This invention provides the application of the metal / heteroatom co-doped silicon-carbon composite material described above in lithium-ion battery anode materials.

[0037] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0038] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the reagents and raw materials described below are all commercially available.

[0039] Example 1

[0040] S1. Add 4g of ethylenediaminetetraacetic acid, 2g of potassium hydroxide, 2g of melamine, 1g of sodium phosphate dodecahydrate, 0.5g of ammonium molybdate and 0.5g of nickel nitrate hexahydrate to pure water, stir for 1 hour, and then dry in an 80℃ forced-air drying oven to obtain the precursor. S2. The obtained precursor is added to a tube furnace and carbonized under a nitrogen atmosphere at a carbonization temperature of 750℃ for 2 hours. After cooling with the furnace, the carbonization product is washed and filtered with dilute hydrochloric acid (6wt%), ethanol and pure water in sequence. It is then dried in a 100℃ forced-air oven to obtain metal compound / heteroatom doped porous carbon. S3. The obtained metal compound / heteroatom-doped porous carbon is added to a rotary furnace. Silane is introduced under nitrogen protection at a flow rate of 6 L / min, where the silane flow rate to nitrogen flow rate is 1:10. The deposition temperature is 500℃, and the deposition time is 5 h. After silane deposition, methane is introduced under nitrogen protection at a flow rate of 6 L / min, where the methane flow rate to nitrogen flow rate is 1:10. The carbon coating temperature is 500℃, and the time is 5 h. After deposition, the furnace is cooled to obtain a silicon-carbon anode material with a Si content of 51 wt%, a carbon content of 47 wt%, and a metal compound content of 2 wt%.

[0041] Example 2

[0042] The only difference from Example 1 is that 5g of melamine and 3g of sodium dodecahydrate were added to S1, while all other conditions remained unchanged, to obtain a silicon-carbon anode material, wherein the Si content was 50wt%, the carbon content was 47wt%, and the metal compound content was 3wt%.

[0043] Example 3

[0044] The only difference from Example 1 is that in S1, nickel nitrate hexahydrate is replaced with cobalt nitrate hexahydrate, and ammonium molybdate is replaced with ammonium tungstate; in S2, the carbonization temperature is increased to 850°C to obtain a silicon-carbon anode material, wherein the silicon content is 51wt%, the carbon content is 47wt%, and the metal compound content is 2wt%.

[0045] Example 4

[0046] The only difference from Example 1 is that in S1, nickel nitrate hexahydrate is replaced with ferric nitrate hexahydrate, and ammonium molybdate is replaced with ammonium vanadate; in S2, the carbonization temperature is increased to 1000℃ to obtain silicon-carbon anode material, wherein the Si content is 51wt%, the carbon content is 47wt%, and the metal compound content is 2wt%.

[0047] Comparative Example 1

[0048] The only difference from Example 1 is that: in S1, ammonium molybdate and sodium phosphate dodecahydrate are not added. After carbonization, hydrochloric acid (16wt%) is used for acid washing for 1 hour to remove metallic nickel. All other conditions remain unchanged to obtain a silicon-carbon composite material with only nitrogen doping.

[0049] Comparative Example 2

[0050] The only difference from Example 1 is that: no ammonium molybdate is added in S1, and after carbonization, hydrochloric acid (16wt%) is used for acid washing for 1 hour, while other conditions remain unchanged, to obtain a nitrogen and phosphorus co-doped silicon-carbon composite material.

[0051] Performance testing

[0052] The electrical performance of the anode material was tested using a half-cell method. The battery casing was of type CR2032. The test conditions were as follows: electrolyte: JN-JW-2249; mass ratio of anode material:SP:carbon nanotubes:LA132 = 94:1:1:4; counter electrode: pure lithium sheet; charge / discharge steps: 1) rest for 10 min; 2) constant current discharge (0.1C, 0.005V); 3) rest for 10 min; 4) rate discharge (0.05C, 0.005V); 5) rest for 10 min; 6) rate discharge (0.02C, 0.005V); 7) rest for 10 min; 8) rate charge (0.1C, 1.5V). The performance of the silicon-carbon anode materials in Examples 1-4 and Comparative Examples 1-2 was tested, and the results are shown in Table 1.

[0053] Table 1 Performance data of silicon-carbon anode materials in Examples 1-4 and Comparative Examples 1-2

[0054] As shown in Table 1, compared with Comparative Examples 1 and 2, the metal / heteroatom co-doped silicon-carbon anode material provided by the present invention has superior electrochemical performance.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a metal / heteroatom co-doped silicon-carbon composite material, characterized in that, Includes the following steps: A carbon source, activator, metal salt, nitrogen source, phosphorus source and water are mixed and complexed to obtain a precursor; The precursor is carbonized to obtain multiphase doped porous carbon. Under protective gas conditions, silane gas is introduced into the multiphase doped porous carbon for vapor deposition, followed by the introduction of carbon source gas for carbon coating, to obtain a metal / heteroatom co-doped silicon-carbon composite material.

2. The preparation method according to claim 1, characterized in that, The carbon source includes one of ethylenediaminetetraacetic acid (EDTA) or EDTA salts.

3. The preparation method according to claim 1, characterized in that, The activator includes one of potassium hydroxide, sodium hydroxide, and potassium carbonate; the mass ratio of the activator to the carbon source is 1:1 to 3.

4. The preparation method according to claim 1, characterized in that, The metal salt includes one or more of nickel nitrate, iron nitrate, cobalt nitrate, molybdate, tungstate, and vanadate; the mass ratio of the metal salt to the carbon source is 1:3 to 10.

5. The preparation method according to claim 1, characterized in that, The nitrogen source includes one or more of melamine, dicyandiamide, and urea; the phosphorus source includes phosphate; the mass ratio of the carbon source to the nitrogen source is 1:0.2~2; the mass ratio of the carbon source to the phosphorus source is 1:0.2~1.

6. The preparation method according to claim 1, characterized in that, The carbonization temperature is 700~1000℃, and the time is 2~10h; the carbonization atmosphere is one or more of nitrogen, argon and helium.

7. The preparation method according to claim 1, characterized in that, The protective gas includes one or more of nitrogen, argon, and helium; the silane gas includes one or two of silane and disilane; the flow ratio of the silane gas to the protective gas is 1:1 to 10; the temperature of the vapor deposition is 500 to 1000°C, and the time is 2 to 24 hours.

8. The preparation method according to claim 1 or 7, characterized in that, The carbon source gas includes one or more of methane, ethane, propane, acetylene, and propyne, and the flow ratio of the carbon source gas to the protective gas is 1:1 to 10; the carbon coating temperature is 500 to 1000°C, and the time is 2 to 24 hours.

9. The metal / heteroatom co-doped silicon-carbon composite material prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The Si content is 10~80wt%, the carbon content is 10~80wt%, and the metal compound content is 1~10wt%.

10. The application of the metal / heteroatom co-doped silicon-carbon composite material of claim 9 in lithium-ion battery anode materials.

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