Silicon carbon nanowire negative electrode material, preparation method and application of silicon carbon nanowire negative electrode material in lithium ion battery

Abstract

The invention provides a silicon-carbon nanowire negative electrode material, a preparation method and application of the silicon-carbon nanowire negative electrode material in a lithium ion battery, and belongs to the technical field of silicon-carbon materials. According to the invention, sodium deoxycholate, Zn (NO3) 2.6 H2O and 2-methylimidazole are mixed and reacted to prepare a hollow linear carbon framework material, and then the hollow linear carbon framework material is sequentially subjected to internal silicon nanowire deposition and surface carbon coating to obtain the silicon-carbon nanowire negative electrode material. The silicon nanowire disclosed by the invention shows a remarkable anti-pulverization characteristic; meanwhile, the hollow linear carbon framework material effectively isolates direct contact between electrolyte and the silicon nanowires, and lithium ion irreversible loss caused by repeated generation and damage of an SEI film is reduced, so that the attenuation rate of the battery capacity is slowed down, and the cycle performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-carbon materials, and particularly to a silicon-carbon nanowire anode material, a preparation method thereof, and an application thereof in a lithium-ion battery. Background Art

[0002] Silicon-carbon materials, as a highly potential anode material for lithium batteries, although they have emerged in the field of energy storage with significant advantages such as high specific capacity, their wide commercial application faces various challenges and limitations. Specifically, during the charge-discharge cycle process of silicon materials, due to the significant volume effect, the cycle performance gradually deteriorates, becoming a major bottleneck restricting their application. At the same time, when silicon materials are in direct contact with the electrolyte, they will face the problem of repeated formation and destruction of the SEI film. This process will cause a large number of lithium ions to undergo irreversible loss, thereby triggering a rapid attenuation of the battery capacity, seriously affecting the electrochemical performance of the silicon-carbon anode material.

[0003] To address the above problems, Patent CN114597358A attempts to compound silicon powder with MOF materials to obtain a precursor Si@CoCu-ZIF, and perform annealing treatment in a protective atmosphere to prepare a carbon-coated silicon anode material with a hollow structure. However, some problems also occur during the implementation of this method. The dispersibility of silicon powder is poor, resulting in difficulty in ensuring the consistency of the product. At the same time, the particle size of silicon powder is relatively high, making it impossible for a single MOF framework coating to effectively solve the problem of pulverization caused by its volume expansion, thus affecting the cycle stability and electrochemical performance of the material. Patent CN117342536A proposes an innovative preparation method, which prepares mesoporous carbon materials by using metal-organic frameworks (Metal-Organic Frameworks, abbreviated as MOF) materials as template sacrifices, and further prepares silicon-carbon anode materials by chemical vapor deposition. However, the deposited silicon obtained by this method is also granular, resulting in easy pulverization of silicon materials during the charge-discharge process, thus leading to a low first charge-discharge efficiency and an accelerated capacity attenuation rate. In addition, the point-to-point contact between granular MOF frameworks has a low crosslinking degree and poor electrical conductivity.

[0004] Compared with other forms of silicon materials, silicon nanowires are less likely to break and pulverize during the charge-discharge cycle; this is because during the insertion and extraction of lithium ions, the internal stress generated by the volume expansion of silicon is also significantly affected by the size effect. According to relevant scientific research results, when the size of silicon materials is reduced to less than 150 nanometers, the internal stress generated by the volume expansion of silicon caused by the insertion of lithium ions will not be sufficient to drive the further expansion of cracks. In addition, the one-dimensional structure of nanowires also enables the material to release stress well through axial expansion, without causing cracking or breakage of the nanowires, thus preventing the pulverization of the electrode.

[0005] Therefore, how to solve the above technical problems and obtain a silicon-carbon nanowire anode material, its preparation method and its application in lithium-ion batteries is the focus of current research. Summary of the Invention

[0006] The purpose of the present invention is to provide a silicon-carbon nanowire anode material, its preparation method and its application in lithium-ion batteries, so as to solve the technical problem that the silicon material obtained by the existing chemical vapor deposition method is prone to pulverization, which affects the electrochemical performance of the material.

[0007] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0008] The present invention provides a preparation method of a silicon-carbon nanowire anode material, comprising the following steps:

[0009] S1: Mix sodium deoxycholate and Zn(NO3)2·6H2O in a phosphate buffer solution to obtain a NaDC-Zn(NO3)2 solution;

[0010] S2: Add a 2-methylimidazole solution to the NaDC-Zn(NO3)2 solution, mix, filter, wash with a phosphate buffer solution and dry to obtain a hollow linear ZIF-8 material;

[0011] S3: Carbonize, acid wash, water wash and dry the hollow linear ZIF-8 material in sequence to obtain a hollow linear carbon framework material;

[0012] S4: Under the atmosphere of a protective gas, sequentially introduce silane and a carbon source gas to sequentially deposit silicon nanowires and carbon coat the hollow linear carbon framework material to obtain a silicon-carbon nanowire anode material.

[0013] Further, in the step S1, the pH of the phosphate buffer solution is 2-11, the mixing temperature is 20-50°C, and the mixing time is 0.5-4h.

[0014] Further, the molar ratio of sodium deoxycholate to Zn(NO3)2·6H2O is 1:0.5-5, and the mass concentration of the NaDC-Zn(NO3)2 solution is 5-50%.

[0015] Further, the mass concentration of the 2-methylimidazole solution is 5-50%, and the molar ratio of 2-methylimidazole to Zn(NO3)2·6H2O in the 2-methylimidazole solution is 4-12:1.

[0016] Further, in the step S2, the pH of the phosphate buffer solution is 2-11, the drying temperature is 60-120°C, and the drying time is 2-24h.

[0017] Further, in step S3, the carbonization is carried out in a protective gas atmosphere, and the protective gas includes helium, neon, argon, krypton, xenon or nitrogen; the flow rate of the protective gas is 0.5 - 5 L / min, the temperature of the carbonization is 650 - 1500 °C, the time of the carbonization is 2 - 24 h, and the heating rate is 1 - 5 °C / min.

[0018] Further, in step S3, the reagent used for pickling includes one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and hydrofluoric acid; the temperature of the drying is 60 - 120 °C, and the time of the drying is 2 - 24 h.

[0019] Further, in step S4, the protective gas includes helium, neon, argon, krypton, xenon or nitrogen; the flow rates of the protective gas, silane and carbon source gas are independently 0.2 - 10 L / min; the temperature of the silicon nanowire deposition is 400 - 1000 °C, the heating rate is 1 - 5 °C / min, and the deposition time is 2 - 24 h.

[0020] Further, the temperature of the carbon coating is 500 - 1200 °C, the heating rate is 1 - 5 °C / min, the time of the carbon coating is 0. half - 8 h, and the carbon source gas includes one or more of methane, ethane, propane, ethylene, propylene, acetylene and propyne;

[0021] The silane includes one or more of silane, disilane and chlorosilane.

[0022] The present invention also provides a silicon - carbon nanowire anode material, in which the Si content is 10 - 90%, and the carbon content is 10 - 90%.

[0023] The present invention also provides an application of the silicon - carbon nanowire anode material in a lithium - ion battery.

[0024] Advantages of the present invention:

[0025] 1) Reduce capacity fade and improve cycling performance: After the silicon nanowires expand and then contract, they are not easily pulverized. At the same time, the carbon framework provides a buffer space for the expansion of the silicon nanowires, further alleviating the problems of expansion and pulverization of silicon during charge and discharge. In addition, the carbon framework effectively isolates the direct contact between the electrolyte and the silicon nanowires, reducing the irreversible loss of lithium ions caused by the repeated formation and destruction of the SEI film, thereby slowing down the attenuation rate of the battery capacity and improving the cycling performance.

[0026] 2) Improve electrical conductivity: The cross - linked carbon framework constitutes a conductive network, effectively improving the problem of poor electrical conductivity of silicon materials and enhancing the charge - discharge efficiency and performance of the battery. Description of the Drawings

[0027] Figure 1 This is the process flow chart for preparing the silicon-carbon nanowire anode material of the present invention. Specific embodiments

[0028] The present invention provides a method for preparing a silicon-carbon nanowire anode material, comprising the following steps:

[0029] S1: Mix sodium deoxycholate and Zn(NO3)2·6H2O in a phosphate buffer solution to obtain a NaDC-Zn(NO3)2 solution;

[0030] S2: Add a 2-methylimidazole solution to the NaDC-Zn(NO3)2 solution, mix, filter, wash with a phosphate buffer solution, and dry to obtain a hollow linear ZIF-8 material;

[0031] S3: Carbonize, pickle, wash with water, and dry the hollow linear ZIF-8 material in sequence to obtain a hollow linear carbon framework material;

[0032] S4: Under the atmosphere of a protective gas, sequentially introduce silane and a carbon source gas to deposit silicon nanowires and coat with carbon on the hollow linear carbon framework material in sequence to obtain the silicon-carbon nanowire anode material.

[0033] In the present invention, in step S1, the pH of the phosphate buffer solution is 2 to 11, preferably 6 to 8; the mixing temperature is 20 to 50°C, preferably 20 to 30°C; the mixing time is 0.5 to 4 h, preferably 0.5 to 3 h.

[0034] In the present invention, the molar ratio of sodium deoxycholate (NaDC) to Zn(NO3)2·6H2O is 1:0.5 to 5; the mass concentration of the NaDC-Zn(NO3)2 solution is 5 to 50%, preferably 10 to 45%.

[0035] In the present invention, the mass concentration of the 2-methylimidazole solution is 5 to 50%, preferably 10 to 45%; the molar ratio of 2-methylimidazole to Zn(NO3)2·6H2O in the 2-methylimidazole solution is 4 to 12:1.

[0036] In the present invention, in step S2, the pH of the phosphate buffer solution is 2 to 11, preferably 6 to 8; the drying temperature is 60 to 120°C, preferably 80 to 100°C; the drying time is 2 to 24 h, preferably 8 to 12 h.

[0037] In the present invention, in step S2, the number of times of washing with the buffer solution is 3 to 6 times, preferably 3 to 4 times.

[0038] In the present invention, in the step S2, the temperature of mixing is 20 to 50 °C, preferably 30 to 40 °C; the time of mixing is 0.5 to 4 h, preferably 1 to 3 h.

[0039] In the present invention, in the step S3, the carbonization is carried out under a protective gas atmosphere. The protective gas is preferably helium, neon, argon, krypton, xenon or nitrogen; the flow rate of the protective gas is 0.5 to 5 L / min, preferably 1 to 4 L / min; the temperature of the carbonization is 650 to 1500 °C, preferably 850 to 1100 °C; the time of carbonization is 2 to 24 h, preferably 5 to 20 h; the heating rate is 1 to 5 °C / min, preferably 2 to 3 °C / min. The purpose of carbonization in the present invention is to improve the conductivity of the porous substrate and simultaneously remove Zn by evaporation.

[0040] In the present invention, in the step S3, the reagent used for pickling is preferably one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and hydrofluoric acid; the temperature of drying is 60 to 120 °C, preferably 80 to 100 °C; the time of drying is 2 to 24 h, preferably 5 to 20 h. In the present invention, the purpose of pickling is to carry out pickling treatment on the obtained powder sample to further remove residual trace metal elements and reduce the influence of self-discharge caused by them; at the same time, pores are further etched on the nanowires, which is conducive to silicon deposition. Finally, the powder is rinsed with distilled water and dried to obtain a hollow linear carbon framework.

[0041] In the present invention, in the step S4, the protective gas is preferably helium, neon, argon, krypton, xenon or nitrogen; the flow rates of the protective gas, silane and carbon source gas are independently 0.2 to 10 L / min, preferably 1 to 8 L / min; the temperature of silicon nanowire deposition is 400 to 1000 °C, preferably 550 to 750 °C; the heating rate is 1 to 5 °C / min, preferably 2 to 3 °C / min; the deposition time is 2 to 24 h, preferably 5 to 20 h.

[0042] In the present invention, the temperature of carbon coating is 500 to 1200 °C, preferably 600 to 1000 °C; the heating rate is 1 to 5 °C / min, preferably 2 to 3 °C / min; the time of carbon coating is 0.5 to 8 h, preferably 1 to 6 h; the carbon source gas is preferably one or more of methane, ethane, propane, ethylene, propylene, acetylene and propyne;

[0043] The silane contains one or more of silane, disilane and chlorosilane.

[0044] The present invention also provides a silicon-carbon nanowire anode material. In the silicon-carbon nanowire anode material, the Si content is 10 to 90%, preferably 40 to 60%; the carbon content is 10 to 90%, preferably 40 to 60%.

[0045] The present invention also provides an application of a silicon-carbon nanowire anode material in a lithium-ion battery.

[0046] The technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0047] Example 1

[0048] S1. Add a certain amount of sodium deoxycholate (NaDC) and Zn(NO3)2·6H2O into a phosphate buffer solution with a pH value of 7.0, control the solid content at 10%, control the molar ratio of NaDC to Zn(NO3)2·6H2O at 1:2, stir and dissolve at room temperature for 1 h to obtain a NaDC-Zn(NO3)2 solution.

[0049] S2. Weigh a certain amount of 2-methylimidazole (2-MeIM), add it to distilled water, control the solid content at 10%, control the molar ratio of 2-MeIM to Zn(NO3)2·6H2O at 9:1, stir at room temperature for 1 h, and prepare a 2-MeIM solution after dissolution; slowly add the prepared 2-MeIM solution to the prepared NaDC-Zn(NO3)2 solution, and stir at room temperature for 6 h. Then filter, and wash with a PBS buffer solution with a pH value of 7 three times, and dry in an oven at 100 °C for 12 h to obtain a hollow linear ZIF-8 material.

[0050] S3. Place the hollow linear ZIF-8 material in a carbonization furnace, heat it to 950 °C at a heating rate of 4 °C / min in an argon atmosphere of a protective gas to perform high-temperature carbonization for 6 h to improve the conductivity of the porous substrate and simultaneously evaporate Zn. Further, perform pickling treatment on the obtained powder sample with a 1M hydrochloric acid solution to further remove residual trace metal elements and reduce the self-discharge effect caused by them; at the same time, further etch pores on the nanowires to facilitate silicon deposition. Finally, wash the powder with distilled water and dry it in an oven at 100 °C for 12 h to obtain a hollow linear carbon framework material.

[0051] S4. Place the hollow linear carbon framework material obtained in S3 into a chemical vapor deposition furnace, introduce argon at a flow rate of 5 L / min for 3 h to drive out oxygen; further, heat the chemical vapor deposition furnace to 550 °C at a heating rate of 4 °C / min, introduce silane under argon protection, control the flow rate of argon and silane at 5 L / min, and perform silicon deposition, and control the deposition time at 3 h; further, heat it to 850 °C at a heating rate of 4 °C / min, introduce acetylene under argon protection gas, control the flow rate of argon and acetylene at 5 L / min, and maintain for 3 h; after coating, silicon-carbon nanowires are obtained, with a silicon content of 52% and a carbon content of 48%.

[0052] Example 2

[0053] The difference from Example 1 is only that: in step S1, the molar ratio of NaDC to Zn(NO3)2·6H2O is replaced by 1:5, and in step S2, the molar ratio of 2-MeIM to Zn(NO3)2·6H2O is replaced by 12:1; the remaining conditions remain unchanged. The prepared silicon-carbon nanowires have a silicon content of 42% and a carbon content of 58%.

[0054] Example 3

[0055] The difference from Example 1 is only that: in step S1, the molar ratio of NaDC to Zn(NO3)2·6H2O is replaced by 2:1, and in step S2, the molar ratio of 2-MeIM to Zn(NO3)2·6H2O is replaced by 4:1; the remaining conditions remain unchanged. The prepared silicon-carbon nanowires have a silicon content of 56% and a carbon content of 44%.

[0056] Example 4

[0057] The difference from Example 1 is only that: in step S4, the carbonization temperature is changed to 850 °C and the carbonization time is changed to 2 h; the remaining conditions remain unchanged. The prepared silicon-carbon nanowires have a silicon content of 50% and a carbon content of 50%.

[0058] Example 5

[0059] The difference from Example 1 is only that: in step S5, the chemical vapor deposition is changed to 750 °C and the deposition time is changed to 6 h; the remaining conditions remain unchanged. The prepared silicon-carbon nanowires have a silicon content of 58% and a carbon content of 42%.

[0060] Comparative Example 1

[0061] The difference from Example 1 is only that: after carbonization in step S4, no pickling treatment is carried out; the remaining conditions remain unchanged. The prepared silicon-carbon nanowires have a silicon content of 44% and a carbon content of 56%.

[0062] Comparative Example 2

[0063] The difference from Example 1 is only that: after chemical vapor deposition in step S5, no carbon coating treatment is carried out; the remaining conditions remain unchanged. The prepared silicon-carbon nanowires have a silicon content of 54% and a carbon content of 46%.

[0064] Perform performance tests on the silicon-carbon nanowire anode materials obtained from the above Examples 1 to 5 and Comparative Examples 1 to 2, and the results are shown in Table 1 below.

[0065] Table 1 Test Results

[0066]

[0067] As can be seen from the above embodiments, the present invention provides a silicon-carbon nanowire anode material, a preparation method thereof, and an application thereof in a lithium-ion battery. The present invention aims to integrate the advantages of the hollow MOF structure and the anti-pulverization characteristics of silicon nanowires to develop a silicon-carbon nanowire anode material to solve problems such as the swelling and pulverization of silicon during charge and discharge and the capacity loss and poor conductivity caused by direct contact with the electrolyte. Specifically, first, hollow linear ZIF-8 is prepared by a soft template method, followed by calcination and carbonization treatment. Further, silicon is deposited in the hollow carbon framework by chemical vapor deposition, and finally, carbon coating is carried out to obtain the silicon-carbon nanowire anode material. The silicon nanowires obtained by the present invention are not easily pulverized after swelling and shrinking. At the same time, the carbon framework provides a buffer space for the swelling of the silicon nanowires, further alleviating the swelling and pulverization problems of silicon during charge and discharge. In addition, the carbon framework effectively isolates the direct contact between the electrolyte and the silicon nanowires, reducing the irreversible loss of lithium ions caused by the repeated formation and destruction of the SEI film, thereby slowing down the attenuation rate of the battery capacity and improving the cycling performance.

[0068] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a silicon-carbon nanowire anode material, characterized in that, It includes the following steps: S1: Mix sodium deoxycholate and Zn(NO3)2·6H2O in a phosphate buffer solution to obtain a NaDC-Zn(NO3)2 solution; S2: Add a 2-methylimidazole solution to the NaDC-Zn(NO3)2 solution, mix, filter, rinse with a phosphate buffer solution, and dry to obtain a hollow linear ZIF-8 material; S3: Carbonize, acid-wash, water-wash, and dry the hollow linear ZIF-8 material in sequence to obtain a hollow linear carbon framework material; S4: Under a protective gas atmosphere, sequentially introduce silane and a carbon source gas to deposit silicon nanowires and carbon coat the hollow linear carbon framework material in sequence to obtain a silicon-carbon nanowire anode material.

2. The preparation method according to claim 1, characterized in that, In the step S1, the pH of the phosphate buffer solution is 2 to 11, the mixing temperature is 20 to 50 °C, and the mixing time is 0.5 to 4 h.

3. The preparation method according to claim 1 or 2, characterized in that The molar ratio of sodium deoxycholate to Zn(NO3)2·6H2O is 1:0.5 to 5, and the mass concentration of the NaDC-Zn(NO3)2 solution is 5 to 50%.

4. The preparation method according to claim 3, wherein The mass concentration of the 2-methylimidazole solution is 5 to 50%, and the molar ratio of 2-methylimidazole to Zn(NO3)2·6H2O in the 2-methylimidazole solution is 4 to 12:

1.

5. The preparation method according to claim 1, characterized in that, In the step S2, the pH of the phosphate buffer solution is 2 to 11, the drying temperature is 60 to 120 °C, and the drying time is 2 to 24 h.

6. The preparation method according to claim 1 or 2 or 5, characterized in that, In the step S3, carbonization is carried out under a protective gas atmosphere. The protective gas includes helium, neon, argon, krypton, xenon, or nitrogen; the flow rate of the protective gas is 0.5 to 5 L / min, the carbonization temperature is 650 to 1500 °C, the carbonization time is 2 to 24 h, and the heating rate is 1 to 5 °C / min.

7. The preparation method according to claim 6, characterized in that, In the step S3, the reagent used for acid-washing includes one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and hydrofluoric acid; the drying temperature is 60 to 120 °C, and the drying time is 2 to 24 h.

8. The preparation method according to claim 7, wherein In the step S4, the protective gas includes helium, neon, argon, krypton, xenon, or nitrogen; the flow rates of the protective gas, silane, and carbon source gas introduced independently are 0.2 to 10 L / min; the temperature for silicon nanowire deposition is 400 to 1000 °C, the heating rate is 1 to 5 °C / min, and the deposition time is 2 to 24 h; The temperature for carbon coating is 500 to 1200 °C, the heating rate is 1 to 5 °C / min, the carbon coating time is 0.5 to 8 h, and the carbon source gas includes one or more of methane, ethane, propane, ethylene, propylene, acetylene, and propyne; The silane includes one or more of silane, disilane, and chlorosilane.

9. The silicon-carbon nanowire anode material prepared by the preparation method according to any one of claims 1 to 8, characterized in that, In the silicon-carbon nanowire anode material, the Si content is 10 to 90%, and the carbon content is 10 to 90%.

10. Use of the silicon-carbon nanowire anode material according to claim 9 in a lithium-ion battery.

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