Silane deposition silicon-carbon composite material as well as preparation method and application thereof

Abstract

The invention provides a silane deposition silicon-carbon composite material as well as a preparation method and application thereof, and belongs to the technical field of lithium battery materials. The preparation method comprises the following steps: performing in-situ reaction on zinc salt, dimethylimidazole and a pore-forming agent to obtain a first precursor; and after carbonization treatment, alkali activation is carried out, and then vapor deposition is adopted to obtain the silane deposition silicon-carbon composite material. The prepared silane deposition silicon-carbon composite material has good stability and mechanical strength, hierarchical pore structure distribution and high-capacity ultra-long circulation. The method can solve the problems that existing vapor deposition silicon-carbon is poor in structural stability, and pores of a carbon matrix obtained through traditional ZIF-8 carbonization are prone to collapse.

Description

Technical Field

[0001] This invention relates to the field of lithium battery materials technology, and in particular to a silane-deposited silicon-carbon composite material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries have become the mainstream electrochemical energy storage product due to their advantages such as high specific energy, long cycle life, no memory effect, and low self-discharge rate. Currently, commercially available anode materials are mainly graphite, but its relatively low theoretical specific capacity (372 mAh / g) ultimately fails to meet demand. While silicon boasts a theoretical specific capacity as high as 4200 mAh / g and a low operating potential, its poor conductivity and its tendency to degrade in Li-ion batteries further hinder its development. + The insertion / deintercalation process involves volume expansion exceeding 300%. These factors severely restrict the commercial development of silicon-based anodes. To address this, silicon particles are typically nano-sized to suppress pulverization during charging and discharging, while mitigating the volume expansion effect; and high-strength materials are used to confine the volume expansion of silicon and improve conductivity.

[0003] Silicon-carbon composite materials prepared by vapor deposition can obtain silicon particles smaller than 10 nm and achieve in-situ confined growth of silicon particles through the rich microporous structure of the porous carbon matrix. Furthermore, thanks to the excellent electrical conductivity and mechanical strength of carbon materials, vapor-deposited silicon-carbon anodes exhibit excellent specific capacity and cycle stability. However, porous carbon as a carbon matrix still suffers from insufficient structural stability and poor interfacial stability. Patent CN117352685A describes the pyrolysis of a ZIF-8 metal-organic framework to obtain a porous carbon framework, followed by vapor deposition with a silicon source to obtain a silicon-carbon composite material. However, this method requires precise control of the pyrolysis temperature to avoid partial pore collapse caused by excessively high pyrolysis temperatures.

[0004] Therefore, it is still necessary to explore better carbon matrix structures to improve the mechanical strength of vapor-deposited silicon-carbon anodes and improve the interfacial stability of materials, so as to obtain new silane-deposited silicon anode materials with excellent performance. Summary of the Invention

[0005] The purpose of this invention is to provide a silane-deposited silicon-carbon composite material, its preparation method and application, wherein the silane-deposited silicon-carbon composite material has good stability and mechanical strength, a hierarchical porous structure distribution and high capacity for ultra-long cycling.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a silane-deposited silicon-carbon composite material, comprising the following steps: Zinc salt, dimethylimidazole, pore-forming agent and solvent are mixed and reacted in situ to obtain the first precursor; The precursor is carbonized to obtain a second precursor. The second precursor is mixed with an alkaline activator and subjected to heat treatment. The resulting product is then acid-washed to obtain the third precursor. Under protective gas conditions, silane gas is introduced into the third precursor for vapor phase deposition, followed by the introduction of carbon source gas for carbon coating, resulting in a silane-deposited silicon-carbon composite material.

[0007] Preferably, the zinc salt includes one or more of zinc nitrate, zinc acetate, zinc sulfate, and zinc chloride; The pore-forming agent includes one of Pluronic F-127, polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, polyethylene glycol, and polystyrene microspheres.

[0008] Preferably, the solvent includes one or more of water, methanol, and ethanol; The mass ratio of zinc salt to dimethylimidazole is 1:1 to 10, and the mass of the pore-forming agent is 0.1 to 20% of the total mass of zinc salt and dimethylimidazole.

[0009] Preferably, the in-situ reaction is carried out at room temperature for 12 to 36 hours.

[0010] Preferably, the carbonization treatment temperature is 800~1200℃, the time is 2~5h, and the heating rate to the carbonization treatment temperature is 1~10℃ / min.

[0011] Preferably, the alkali activator includes one or more of KOH, NaOH, and K2CO3; the mass ratio of the alkali activator to the second precursor is 1 to 4:1. The heat treatment temperature is 600~900℃, the time is 1~3h, and the heating rate to the heat treatment temperature is 2~5℃ / min.

[0012] Preferably, the acid used for pickling is one or more of hydrochloric acid, nitric acid, and sulfuric acid.

[0013] Preferably, the protective gas is 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 6 to 12 hours. The carbon source gas includes one or more of methane, ethane, propane, acetylene, and propyne; 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 6 to 12 hours.

[0014] The present invention provides a silane-deposited silicon-carbon composite material prepared by the preparation method described above, wherein the Si content is 10-90 wt% and the carbon content is 10-90 wt%.

[0015] This invention provides the application of the silane-deposited silicon-carbon composite material described above in lithium-ion battery anode materials.

[0016] Compared with the prior art, the present invention has the following advantages: 1) Precise regulation and synergistic effect of multi-level pore structure; pore-forming agents can introduce mesopores or macropores into ZIF-derived carbon, making up for the limitation of ZIF itself being mainly micropores, forming a multi-level pore system, improving lithium-ion transport efficiency, and enhancing the rate performance of silicon-carbon anode materials.

[0017] 2) Enhance the specific surface area and porosity of vapor-deposited silicon-carbon anodes; direct carbonization of ZIF can easily lead to pore collapse, while the pore-forming agent generates gas or leaves space when decomposed at high temperature, which significantly increases the specific surface area and porosity of the derived carbon, helps to shorten the lithium-ion diffusion path and reduce the resistance during lithium-ion transport, thereby improving the electrochemical activity of silicon-carbon anodes.

[0018] 3) Nitrogen doping of carbon matrix in silicon-carbon materials; after carbonization of the organic ligand (dimethylimidazole) of ZIF, a nitrogen-doped carbon matrix is ​​formed, which effectively improves the conductivity of silicon-carbon anode and optimizes interface stability.

[0019] 4) ZIF-derived rigid carbon skeletons provide mechanical support, thereby improving the mechanical strength of silicon-carbon composites.

[0020] Therefore, the silane-deposited silicon-carbon composite material prepared by this invention has good stability and mechanical strength, hierarchical pore structure distribution and high capacity ultra-long cycling. This method can solve the problems of poor structural stability of existing vapor-deposited silicon-carbon and make up for the problem of easy collapse of carbon matrix channels obtained by traditional ZIF-8 carbonization. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation method of the silane-deposited silicon-carbon composite material of the present invention. Detailed Implementation

[0022] 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.

[0023] This invention provides a method for preparing a silane-deposited silicon-carbon composite material, comprising the following steps: Zinc salt, dimethylimidazole, pore-forming agent and solvent are mixed and reacted in situ to obtain the first precursor; The precursor is carbonized to obtain a second precursor. The second precursor is mixed with an alkaline activator and subjected to heat treatment. The resulting product is then acid-washed to obtain the third precursor. Under protective gas conditions, silane gas is introduced into the third precursor for vapor phase deposition, followed by the introduction of carbon source gas for carbon coating, resulting in a silane-deposited silicon-carbon composite material.

[0024] In this invention, the zinc salt preferably includes one or more of zinc nitrate, zinc acetate, zinc sulfate, and zinc chloride; when the zinc salt is two or more of the above, there is no special limitation on the ratio of different types of zinc salts, and any ratio is acceptable.

[0025] In this invention, the pore-forming agent preferably includes one of Pluronic F-127, polyvinylpyrrolidone (PVP), hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polyethylene glycol (PEG), and polystyrene microspheres (PS).

[0026] In this invention, the solvent preferably includes one or more of water, methanol, and ethanol. When the solvent is two or more of the above, there is no special limitation on the ratio of different types of solvents, and any ratio is acceptable. This invention does not have a special limitation on the amount of solvent used, as long as the materials are mixed evenly.

[0027] In this invention, the pore-forming agent is preferably added to the solvent, and zinc salt and dimethylimidazole are added in sequence, followed by stirring to carry out an in-situ reaction.

[0028] In this invention, the mass ratio of zinc salt to dimethylimidazole is preferably 1:1 to 10, more preferably 1:2 to 9, and even more preferably 1:5 to 8; the mass of the pore-forming agent is preferably 0.1 to 20% of the total mass of zinc salt and dimethylimidazole, more preferably 0.5 to 10%, and even more preferably 1 to 5%.

[0029] In this invention, the temperature of the in-situ reaction is preferably room temperature, and the time is preferably 12-36 hours, more preferably 24-30 hours.

[0030] After the in-situ reaction is completed, the product is preferably centrifuged, washed, and dried to obtain a first precursor, denoted as precursor Q1 (ZIF-derived carbon skeleton); the drying temperature is preferably 60°C.

[0031] In this invention, the carbonization treatment temperature is preferably 800~1200℃, more preferably 900~1000℃; the time is preferably 2~5h, more preferably 3~4h; the heating rate to the carbonization treatment temperature is preferably 1~10℃ / min, more preferably 5~8℃ / min; the carbonization treatment is preferably carried out in an argon atmosphere.

[0032] After carbonization, the material is cooled, and the resulting second precursor is denoted as carbon skeleton precursor Q2.

[0033] In this invention, the alkali activator preferably includes one or more of KOH, NaOH and K2CO3; when the alkali activator is two or more of the above, this invention does not have a special limitation on the ratio of different types of alkali activators, and any ratio is acceptable; the mass ratio of the alkali activator to the second precursor is preferably 1~4:1, more preferably 2~3:1.

[0034] In this invention, the second precursor and the alkali activator are ground evenly, then added to an atmosphere furnace for heat treatment. After cooling, the product is acid-washed to remove impurities, washed with pure water until neutral, and dried to obtain the third precursor, denoted as carbon skeleton precursor Q3.

[0035] In this invention, the heat treatment temperature is preferably 600-900℃, more preferably 700-800℃, the time is preferably 1-3h, more preferably 2-3h, and the heating rate to the heat treatment stage is preferably 2-5℃ / min, more preferably 3-5℃ / min. This invention increases the pore volume of the carbon framework precursor through alkaline activator heat treatment, resulting in the deposition of more silicon.

[0036] In this invention, the acid used for pickling is preferably one or more of hydrochloric acid, nitric acid, and sulfuric acid; when the acid is two or more of the above, there is no special limitation on the ratio of different types of acid, and any ratio is acceptable. This invention does not impose special limitations on the concentration of the acid or the specific pickling process; any process well known in the art can be followed.

[0037] In this invention, after acid washing and drying, a carbon framework precursor Q3 is obtained; the drying temperature is preferably 60~120℃, more preferably 80~100℃.

[0038] The present invention preferably involves adding a third precursor into a rotary kiln for vapor deposition.

[0039] In this invention, the protective gas is preferably one or more of nitrogen, argon, and helium, and the silane gas preferably includes one or two of silane and disilane; the flow rate of the silane gas is preferably 1~10 L / min, more preferably 2~6 L / min; the flow ratio of the silane gas to the protective gas is preferably 1:1~10, more preferably 1:3~5; the temperature of the vapor deposition is preferably 500~1000℃, more preferably 600~800℃, and the time is preferably 6~12h, more preferably 9~10h.

[0040] After the vapor deposition is completed, the present invention preferably continues to introduce carbon source gas under protective gas conditions to perform carbon coating.

[0041] In this invention, the carbon source gas preferably includes one or more of methane, ethane, propane, acetylene, and propyne; the flow rate of the carbon source gas is preferably 1~8 L / min, more preferably 3~6 L / min, and even more preferably 2~6 L / min; the flow ratio of the carbon source gas to the protective gas is preferably 1:1~10, more preferably 1:3~5; the carbon coating temperature is preferably 500~1000℃, more preferably 600~800℃, and the time is preferably 6~12h, more preferably 9~10h.

[0042] When the silane gas or carbon source gas is two or more of the above, there is no special limitation on the ratio of different types of silane gas or carbon source gas, and any ratio is acceptable.

[0043] The present invention provides a silane-deposited silicon-carbon composite material prepared by the preparation method described above, wherein the Si content is 10-90 wt%, more preferably 30-80 wt%, further preferably 45-60 wt%, and even more preferably 50-52 wt%; and the carbon content is 10-90 wt%, more preferably 30-60 wt%, further preferably 45-55 wt%, and even more preferably 48-50 wt%.

[0044] This invention provides the application of the silane-deposited silicon-carbon composite material described above in lithium-ion battery anode materials. This invention does not specifically limit the method of application; any method well-known in the art can be used.

[0045] 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.

[0046] 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.

[0047] Example 1

[0048] S1. Add 100g of Pluronic F-127 to 1000mL of pure water, then add zinc acetate and dimethylimidazole sequentially. Stir for 24h, centrifuge and wash, and dry in a 60℃ forced-air drying oven to obtain precursor Q1; wherein the mass ratio of zinc acetate to dimethylimidazole is 1:8, and the mass of Pluronic F127 is 0.1% of the total mass of zinc acetate and dimethylimidazole; S2. The obtained precursor Q1 is added to an atmosphere furnace and heated to 800°C at a heating rate of 5°C / min under argon atmosphere. The temperature is held for 3 hours and then cooled to obtain carbon skeleton precursor Q2. S3. Grind the obtained carbon framework precursor Q2 and KOH evenly at a mass ratio of 1:2, add them to an atmosphere furnace, heat to 800℃ at a heating rate of 5℃ / min, hold for 3h, wash the obtained product with hydrochloric acid (concentration of 37%), wash with pure water until neutral, and dry at 60℃ to obtain carbon framework precursor Q3. S4. The obtained carbon framework precursor Q3 was added to a rotary furnace, and silane was introduced under argon protection at a flow rate of 6 L / min, where the silane flow rate: argon flow rate = 1:1. The deposition temperature was 500℃, and the deposition time was 9 h. After the silane deposition was completed, propyne was introduced under argon protection at a flow rate of 6 L / min, where the propyne flow rate: argon flow rate = 1:1. The deposition temperature was 500℃, and the deposition time was 9 h. After the deposition was completed, the furnace was cooled to obtain a silane-deposited silicon-carbon composite material with a Si content of 45 wt% and a carbon content of 55 wt%.

[0049] Example 2

[0050] The only difference between this embodiment and Example 1 is that: in step S1, the mass of Pluronic F127 is 0.5% of the total mass of zinc acetate and dimethylimidazole, and the Si content in the prepared silane-deposited silicon-carbon composite material is 52wt% and the carbon content is 48wt%.

[0051] Example 3

[0052] The only difference between this embodiment and Example 1 is that: in step S1, the mass of Pluronic F127 is 1% of the total mass of zinc acetate and dimethylimidazole, and the prepared silane-deposited silicon-carbon composite material has a Si content of 48 wt% and a carbon content of 52 wt%.

[0053] Example 4

[0054] The only difference between this embodiment and Example 1 is that Pluronic F127 is replaced with PVP in step S1, and the Si content and carbon content in the prepared silane-deposited silicon-carbon composite material are 50wt%.

[0055] Comparative Example 1

[0056] S1. Add 100g of Pluronic F127 to 1000mL of pure water, then add zinc acetate and dimethylimidazole sequentially. Stir for 24h, centrifuge, wash, and dry in a 60℃ forced-air drying oven to obtain precursor Q1; wherein the mass ratio of zinc acetate to dimethylimidazole is 1:8, and the mass of Pluronic F127 is 0.5% of the total mass of zinc acetate and dimethylimidazole; S2. Add the precursor Q1 obtained in S1 to an atmosphere furnace, heat it to 800℃ at a heating rate of 5℃ / min under argon atmosphere, hold it for 3h, and then cool it to obtain carbon skeleton precursor Q2. S3. The carbon framework precursor Q2 obtained in S2 is added to a rotary furnace, and silane is introduced under argon protection at the same flow rate as in Example 1, wherein the silane flow rate: argon flow rate = 1:1, the deposition temperature is 500℃, and the deposition time is 9h. After the silane deposition is completed, propyne is introduced under argon protection at the same flow rate as in Example 1, wherein the propyne flow rate: argon flow rate = 1:1, the deposition temperature is 500℃, and the deposition time is 9h. After the deposition is completed, the furnace is cooled to obtain a silane-deposited silicon-carbon anode material with a Si content of 35wt% and a carbon content of 65wt%.

[0057] Comparative Example 2

[0058] The only difference between this comparative example and Example 1 is that Pluronic F-127 was not added in step S1.

[0059] Performance testing

[0060] The pore volume and specific surface area of ​​the silicon-carbon anode materials prepared in Examples 1-4 and Comparative Examples 1-2 were tested respectively, and the results are shown in Table 1.

[0061] Silicon-carbon anode materials obtained from different cases were used to fabricate anode sheets with a mass ratio of silicon-carbon anode:conductive carbon black:carbon nanotubes:binder:LA132 = 94:1:1:4. The anode sheets were then used to fabricate CR2032 coin cells. The test conditions were as follows: electrolyte: JN-JW-2249; counter electrode: pure lithium sheet; charge / discharge regime: 1) resting for 10 min; 2) constant current discharge (0.1C, 0.005V); 3) resting for 10 min; 4) rate discharge (0.05C, 0.005V); 5) resting for 10 min; 6) rate discharge (0.02C, 0.005V); 7) resting 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 2.

[0062] The mechanical strength of the silicon-carbon anode materials in Examples 1-4 and Comparative Examples 1-2 was characterized by single-particle strength. The pressure data of single-particle crushing are shown in Table 3.

[0063] Table 1. Physical property data of silicon-carbon anode materials in Examples 1-4 and Comparative Examples 1-2

[0064] Table 2 Performance data of silicon-carbon anode materials in Examples 1-4 and Comparative Examples 1-2

[0065] Table 3 shows the pressure data of silicon-carbon anode materials subjected to crushing in Examples 1-4 and Comparative Examples 1-2.

[0066] Based on the analysis of Tables 1, 2, and 3, the pore volume and micropore ratio in Table 1 indicate that the silicon-carbon composite material prepared in this invention has a hierarchical porous structure; the capacity retention rate in Table 2 indicates that the prepared silicon-carbon composite material has an ultra-long cycle life; the single particle strength in Table 3 indicates that the prepared silicon-carbon composite material has excellent mechanical strength and stability. Moreover, the porous carbon synthesized in Example 2 has a rich pore structure and extremely strong mechanical strength, and the negative electrode prepared from it has the best first charge capacity and first efficiency, as well as an ultra-high capacity retention rate after 50 and 200 cycles.

[0067] 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 silane-deposited silicon-carbon composite material, characterized in that, Includes the following steps: Zinc salt, dimethylimidazole, pore-forming agent and solvent are mixed and reacted in situ to obtain the first precursor; The precursor is carbonized to obtain a second precursor. The second precursor is mixed with an alkaline activator and subjected to heat treatment. The resulting product is then acid-washed to obtain the third precursor. Under protective gas conditions, silane gas is introduced into the third precursor for vapor phase deposition, followed by the introduction of carbon source gas for carbon coating, resulting in a silane-deposited silicon-carbon composite material.

2. The preparation method according to claim 1, characterized in that, The zinc salt includes one or more of zinc nitrate, zinc acetate, zinc sulfate, and zinc chloride; The pore-forming agent includes one of Pluronic F-127, polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, polyethylene glycol, and polystyrene microspheres.

3. The preparation method according to claim 1 or 2, characterized in that, The solvent includes one or more of water, methanol, and ethanol; The mass ratio of zinc salt to dimethylimidazole is 1:1 to 10, and the mass of the pore-forming agent is 0.1 to 20% of the total mass of zinc salt and dimethylimidazole.

4. The preparation method according to claim 3, characterized in that, The in-situ reaction was carried out at room temperature for 12 to 36 hours.

5. The preparation method according to claim 1, characterized in that, The carbonization treatment is carried out at a temperature of 800~1200℃ for 2~5 hours, and the heating rate to the carbonization treatment temperature is 1~10℃ / min.

6. The preparation method according to claim 1, characterized in that, The alkaline activator includes one or more of KOH, NaOH, and K2CO3; the mass ratio of the alkaline activator to the second precursor is 1~4:

1. The heat treatment temperature is 600~900℃, the time is 1~3h, and the heating rate to the heat treatment temperature is 2~5℃ / min.

7. The preparation method according to claim 1, characterized in that, The acid used for pickling is one or more of hydrochloric acid, nitric acid, and sulfuric acid.

8. The preparation method according to claim 1, characterized in that, The protective gas is one or more of nitrogen, argon, and helium; the silane gas includes one or two of methanesilane and ethylsilane; 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 6 to 12 hours. The carbon source gas includes one or more of methane, ethane, propane, acetylene, and propyne; 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 6 to 12 hours.

9. The silane-deposited 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 10~90wt%, and the carbon content is 10~90wt%.

10. The application of the silane-deposited silicon-carbon composite material of claim 9 in lithium-ion battery anode materials.

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