A porous silicon-carbon composite anode material and its preparation method

Abstract

This invention belongs to the field of battery materials, specifically relating to a porous silicon-carbon composite anode material and its preparation method. The invention involves adding SiOx particles to an aqueous solution of graphene oxide to form solution A. A highly protonated chitosan solution is prepared, and carbon nanotubes are added, followed by ultrasonic treatment to form solution B. Solution A is added to solution B, a coupling agent is added, and the mixture is subjected to heat treatment. The resulting gel is freeze-dried to obtain a self-supporting three-dimensional porous composite aerogel. The aerogel is then heat-treated in an argon atmosphere to obtain the porous silicon-carbon composite anode material. This invention, through the design of a multi-layered nested composite structure of SiOx carbon nanotubes, graphene anchoring structure, and porous carbon aerogel, can improve the material's conductivity, lithium storage capacity, and cycle stability, demonstrating high application value.

Description

Technical Field

[0001] This invention belongs to the field of battery materials, specifically relating to a porous silicon-carbon composite anode material and its preparation method. Background Technology

[0002] With the increasing demand for electric vehicles and energy storage systems, lithium-ion batteries, as high-energy-density, long-life, and environmentally friendly energy storage devices, have been widely used. Among these, the anode material, as a crucial component of the battery, directly affects its energy storage performance and cycle stability. Currently, the anode materials for lithium-ion power batteries are mainly composed of carbon materials, but their lithium storage capacity is relatively low and cannot meet the growing energy storage demands. Silicon materials have high lithium storage capacity, but volume expansion occurs during lithium-ion insertion and extraction, leading to a decrease in battery lithium storage capacity and a decline in cycle performance. Therefore, developing an anode material that can balance lithium storage capacity and cycle stability is of great significance.

[0003] CN 111769256A discloses a sandwich-like silicon-carbon anode material and its preparation method. The silicon-carbon anode material is shaped like a sandwich rod and consists of a carbon nanotube layer, a silicon layer, a polydopamine carbon layer, and a graphene layer from the inside out. This sandwich-like silicon-carbon anode material can effectively suppress the excessive growth of the SEI film, improve the coulombic efficiency, significantly improve the conductivity of the material, reduce the volume expansion of the silicon anode material, and prevent the silicon layer from being exposed to the electrolyte and being pulverized, thereby improving the cycle performance and energy density of lithium-ion batteries.

[0004] CN 108598413 A discloses a method for preparing silicon-based anode active materials, as well as silicon-based anode active materials, lithium-ion battery anode materials, and lithium-ion batteries. The preparation method includes adding a polymeric protective agent during the process of coating a silicon dioxide layer onto nano-silicon, coating a graphene oxide layer onto the silicon dioxide layer, and finally etching with hydrofluoric acid to obtain a Si / void / SiO2 / void / Graphene composite material with nano-silicon as the core and silicon dioxide and graphene layers sequentially coated from the inside out. This method alleviates the technical problem that it is difficult to achieve significant performance improvements in silicon-based anode active materials through existing methods such as single silicon nano-sizing or carbon coating and the preparation of porous structures.

[0005] CN 108933259A discloses a preparation process for a lithium-ion battery anode material. The process involves preparing graphene oxide, ZnS / C composite material, fine powder, and a precursor matrix; taking out the precursor matrix, graphite conductive agent, and PVDF and mixing them evenly, then heating and stirring; then adding N-methylpyrrolidone and stirring evenly to make the mixture a viscous slurry; then coating the slurry onto copper foil, with the copper foil and slurry spaced apart to obtain an intermediate matrix; placing the intermediate matrix in a molding machine and molding it under pressure; and finally cutting and drying to obtain the finished product.

[0006] Existing Solutions: To improve the energy storage performance and cycle stability of lithium-ion batteries, many researchers have explored various solutions. Some existing solutions include: ① silicon nanoparticle encapsulation; ② silicon oxide composite materials; ③ silicon-carbon composite materials. Among these, silicon-carbon composite materials are a relatively common approach, combining carbon and silicon materials to simultaneously achieve both lithium storage capacity and cycle stability. Problems with Existing Technologies: However, existing silicon-carbon composite materials still face several challenges. First, due to the volume expansion of silicon, silicon particles are prone to structural loosening and peeling during charge and discharge, leading to decreased cycle performance. Second, the poor conductivity of silicon limits the battery's discharge performance. Furthermore, the preparation process of existing silicon-carbon composite materials is complex and costly, hindering large-scale production. Therefore, there is a need to research a novel silicon-carbon composite anode material that can overcome these problems and improve the energy storage performance and cycle stability of lithium-ion batteries. Summary of the Invention

[0007] The existing technical problems are: 1. The volume expansion of silicon materials during lithium ion insertion and extraction causes a decrease in cycle performance; 2. The poor conductivity of silicon materials limits the battery discharge performance; 3. The existing silicon-carbon composite material preparation process is complex and costly.

[0008] To address the aforementioned technical problems, this application provides the following technical solution:

[0009] This invention provides a method for preparing a porous silicon-carbon composite anode material, comprising the following steps:

[0010] S11: Mix solution A, solution B and coupling agent, heat at 50-80℃ to react, and obtain a viscous mixed solution;

[0011] Solution A is obtained by mixing SiOx particles with an aqueous solution of graphene oxide; wherein, x = 0.8-1.3;

[0012] Solution B is obtained by adding carbon nanotubes to a highly protonated solution and mixing them; the highly protonated solution is obtained by adjusting the zeta potential to +15 to +80 mV using an acid-containing chitosan aqueous solution.

[0013] S12: After storing the viscous mixed solution in an environment of 0-5℃ for 12-48h, soak it in water for 12h, repeat the soaking three times to obtain a gel;

[0014] S13: The gel is pre-cooled at -15℃ for 12-24h, then placed in a liquid nitrogen environment for quick freezing treatment, and then placed in a freeze dryer for freeze drying treatment for 24-72h to obtain a self-supporting three-dimensional porous composite aerogel.

[0015] S14: Under an inert atmosphere, the self-supporting three-dimensional porous composite aerogel is heat-treated at 800-1000℃ for 1-3 hours to obtain a porous silicon-carbon composite anode material.

[0016] Preferably, in step S11, the SiOx particles are obtained by ball milling a mixture of silicon and SiO2 particles, and the particle size is 0.1-2 μm.

[0017] Preferably, in step S11, the mixing method is to stir solution B and add solution A until the pH of the mixture is 6-8, and add a coupling agent while stirring to obtain a viscous mixed solution.

[0018] Preferably, in solution A, the mass fraction of SiOx is 0.01-2%, and the mass ratio of SiOx particles to graphene oxide is 1:0.01-5.

[0019] Preferably, in the acid-containing chitosan aqueous solution, the degree of deacetylation of chitosan is 75-99%, the viscosity is 100-500 mPa·s, and the mass fraction is 2-10%.

[0020] Preferably, in solution B, the mass ratio of carbon nanotubes to chitosan is 1:0.02-5.

[0021] Preferably, the coupling agent is selected from one or more of polyethylene glycol, formaldehyde, propylene oxide, and epichlorohydrin; the mass ratio of the coupling agent to chitosan in solution B is 1:1-5.

[0022] Preferably, in step S11, the reaction is followed by ultrasonic treatment for 0-120 minutes.

[0023] Preferably, in step S11, the acid in the chitosan aqueous solution containing acid is hydrochloric acid, formic acid, acetic acid, citric acid, or acetic acid.

[0024] Preferably, in step S14, the inert atmosphere is argon.

[0025] The present invention also provides a porous silicon-carbon composite anode material prepared by the above preparation method.

[0026] The present invention also provides a porous silicon-carbon composite anode material prepared by the above preparation method.

[0027] This invention improves the conductivity, lithium storage capacity, and cycle stability of materials by designing a multi-layered nested composite structure of SiOx carbon nanotubes, graphene anchoring structure, and porous carbon aerogel, and has high application value.

[0028] The technical solution of the present invention has the following advantages compared with the prior art:

[0029] 1. Improved lithium storage capacity and cycle stability of lithium-ion battery anode materials: By designing an anchoring structure of SiOx carbon nanotubes and graphene and a multi-nested composite structure of porous carbon aerogel through electrostatic adsorption effect, a silicon-carbon anode material was formed, which has high lithium storage capacity and cycle stability, and can meet the growing energy storage demand.

[0030] 2. Improved electrical conductivity: The porous carbon aerogel framework throughout the entire structure improves the electrical conductivity of the material, thereby enhancing the battery's discharge performance.

[0031] 3. Reduced preparation cost: Chitosan is used to form carbon aerogel through electrostatic adsorption, and silicon-carbon anode materials are obtained through supercritical drying and high-temperature pyrolysis. The preparation process is simple and the cost is low, which is conducive to large-scale production.

[0032] Compared to existing technologies, the advantages of this invention lie in its multi-layered nested composite structure of carbon aerogel and the anchoring structure formed by SiOx carbon nanotubes and graphene, which balances the high lithium storage capacity of silicon materials with the cycle stability of carbon materials, while also improving the conductivity of the materials and reducing the preparation cost. Therefore, the silicon-carbon composite anode material of this invention has better application prospects. Attached Figure Description

[0033] Figure 1 This is a picture of the actual product.

[0034] Figure 2 This is a picture of the actual battery.

[0035] Figure 3 This is a diagram of the battery's appearance. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0037] Example 1

[0038] (1) Stir in solution B and add solution A until the pH of the mixture is 7. Add polyethylene glycol coupling agent while stirring, heat to 65°C and sonicate for 60 min to obtain a viscous mixed solution.

[0039] Solution A is obtained by mixing SiOx particles with a particle size of 0.5-2 μm with an aqueous solution of graphene oxide; wherein the value of x is in the range of 0.8-1.3; the mass fraction of SiOx in solution A is 1%, and the mass ratio of SiOx particles to graphene oxide is 1:3.

[0040] Solution B was obtained by adding carbon nanotubes to a highly protonated solution and mixing them. This highly protonated solution was obtained by adjusting the zeta potential to +15 to +80 mV using an aqueous solution of chitosan containing acetic acid. The chitosan had a degree of deacetylation of 85%, a viscosity of 300 mPa·s, and a mass fraction of 6%. The mass ratio of polyethylene glycol coupling agent, carbon nanotubes, and chitosan was 1:1:3.

[0041] (2) After storing the viscous mixed solution at 2°C for 30 hours, it was soaked in water for 12 hours. This process was repeated three times to obtain a gel.

[0042] (3) The gel was pre-cooled at -15℃ for 18h, then placed in a liquid nitrogen environment for quick freezing treatment, and then placed in a freeze dryer for freeze drying treatment for 48h to obtain a self-supporting three-dimensional porous composite aerogel.

[0043] (4) Under an argon atmosphere, the self-supporting three-dimensional porous composite aerogel was heat-treated at 900℃ for 2h to obtain a porous silicon-carbon composite anode material.

[0044] Example 2

[0045] (1) Stir in solution B and add solution A until the pH of the mixture is 6. Add coupling agent while stirring and heat at 50°C to react and obtain a viscous mixed solution.

[0046] Solution A was obtained by mixing SiOx particles with a particle size of 0.1 μm with an aqueous solution of graphene oxide; wherein the value of x is in the range of 0.8-1.3; the mass fraction of SiOx is 0.01%; and the mass ratio of SiOx particles to graphene oxide is 1:0.01.

[0047] Solution B was obtained by mixing carbon nanotubes with a highly protonated solution. This highly protonated solution was prepared by adjusting the zeta potential to +15 mV using an aqueous solution of chitosan containing hydrochloric acid, formic acid, acetic acid, citric acid, or acetic acid. The degree of deacetylation of chitosan was 75%, the viscosity was 100 mPa·s, and the mass fraction was 2%. The mass ratio of carbon nanotubes to chitosan was 1:0.02.

[0048] The coupling agent is selected from one or more of polyethylene glycol, formaldehyde, propylene oxide and epichlorohydrin; the mass ratio of the coupling agent to chitosan in solution B is 1:1.

[0049] (2) After storing the viscous mixed solution in a 0℃ environment for 12h, it was soaked in water for 12h. This process was repeated three times to obtain a gel.

[0050] (3) The gel was pre-cooled at -15℃ for 12h, then placed in a liquid nitrogen environment for quick freezing treatment, and then placed in a freeze dryer for freeze drying treatment for 24h to obtain a self-supporting three-dimensional porous composite aerogel.

[0051] (4) Under an argon atmosphere, the self-supporting three-dimensional porous composite aerogel was heat-treated at 800℃ for 1h to obtain a porous silicon-carbon composite anode material.

[0052] Example 3

[0053] (1) Stir in solution B and add solution A until the pH of the mixture is 8. Add coupling agent while stirring, heat to 80°C and sonicate for 120 min to obtain a viscous mixed solution.

[0054] Solution A was obtained by mixing SiOx particles with a particle size of 2 μm with an aqueous solution of graphene oxide; wherein, x = 0.8-1.3; the mass fraction of SiOx was 2% and the mass ratio of SiOx particles to graphene oxide was 1:5.

[0055] Solution B was obtained by mixing carbon nanotubes with a highly protonated solution. This highly protonated solution was prepared by adjusting the zeta potential to +80 mV using an aqueous solution of chitosan containing hydrochloric acid, formic acid, acetic acid, citric acid, or acetic acid. The degree of deacetylation of chitosan was 99%, the viscosity was 500 mPa·s, and the mass fraction was 10%. The mass ratio of carbon nanotubes to chitosan was 1:5.

[0056] The coupling agent is selected from one or more of polyethylene glycol, formaldehyde, propylene oxide and epichlorohydrin; the mass ratio of the coupling agent to chitosan in solution B is 1:5.

[0057] (2) After storing the viscous mixed solution at 5°C for 48 hours, it was soaked in water for 12 hours. This process was repeated three times to obtain a gel.

[0058] (3) The gel was pre-cooled at -15℃ for 24h, then placed in a liquid nitrogen environment for quick freezing treatment, and then placed in a freeze dryer for freeze drying treatment for 72h to obtain a self-supporting three-dimensional porous composite aerogel.

[0059] (4) Under an argon atmosphere, the self-supporting three-dimensional porous composite aerogel was heat-treated at 1000℃ for 3h to obtain a porous silicon-carbon composite anode material.

[0060] Effect Evaluation 1

[0061] Example 1: Porous carbon aerogel was mixed with an anchoring structure formed by SiOx carbon nanotubes and graphene in a certain proportion, and silicon raw material was added to prepare a silicon-carbon composite material. During the preparation process, the silicon mass fraction in the silicon-carbon composite material was 50%, the carbon mass fraction was 45%, and the specific surface area of ​​the porous carbon aerogel was 800 m². 2 / g, with a lithium storage capacity of 1200mAh / g, and a cycle stability of over 80% after 500 cycles.

[0062] By combining the above technologies, the conductivity, lithium storage capacity, and cycle stability of silicon-carbon anode materials can be improved, thus balancing lithium storage capacity and cycle stability, and thus having high application value.

[0063] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a porous silicon-carbon composite anode material, characterized in that, Includes the following steps: S11: Mix solution A, solution B and coupling agent, heat at 50-80℃ to react, and obtain a mixed solution; Solution A is obtained by mixing SiOx particles with an aqueous solution of graphene oxide; wherein x = 0.8-1.3; the mass fraction of SiOx in solution A is 0.01-2%, and the mass ratio of SiOx particles to graphene oxide is 1:0.01-5; Solution B is obtained by mixing carbon nanotubes with a highly protonated solution; the highly protonated solution is obtained by adjusting the zeta potential to +15~+80mV in an aqueous solution of chitosan containing acid; in step S11, the SiOx particles are obtained by ball milling a mixture of silicon and SiO2 particles, with a particle size of 0.1-2 μm; the mass ratio of carbon nanotubes to chitosan in solution B is 1:0.02-5; S12: After storing the mixed solution in an environment of 0-5℃ for 12-48 h, soak it in water for 12 h, repeat the soaking three times to obtain a gel; S13: After pre-cooling the gel for 12-24 h, it is placed in a liquid nitrogen environment for quick freezing treatment, and then placed in a freeze dryer for freeze drying treatment for 24-72 h to obtain a self-supporting three-dimensional porous composite aerogel. S14: Under an inert atmosphere, the self-supporting three-dimensional porous composite aerogel is heat-treated at 800-1000℃ for 1-3 hours to obtain a porous silicon-carbon composite anode material.

2. The preparation method according to claim 1, characterized in that, In step S11, the mixing method is to continuously stir solution B and add solution A to it until the pH of the mixture is 6-8. A coupling agent is added while stirring to obtain a mixed solution.

3. The preparation method according to claim 1, characterized in that, The acid-containing chitosan aqueous solution has a degree of deacetylation of 75-99%, a viscosity of 100-500 mpa.s, and a mass fraction of 2-10%.

4. The preparation method according to claim 1, characterized in that, The coupling agent is selected from one or more of polyethylene glycol, formaldehyde, propylene oxide and epichlorohydrin; the mass ratio of the coupling agent to chitosan in solution B is 1:1-5.

5. The preparation method according to claim 1, characterized in that, In step S11, the acid in the chitosan aqueous solution containing acid is hydrochloric acid, formic acid, citric acid, or acetic acid.

6. The preparation method according to claim 1, characterized in that, In step S13, the drying temperature is 80-150℃.

7. A porous silicon-carbon composite anode material prepared by the preparation method according to any one of claims 1-6.

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