Preparation method of self-assembled graphene silicon battery negative electrode material

Abstract

This invention provides a method for preparing a self-assembled graphene-silicon battery anode material: Silica is reacted with an organic carboxylic acid / carboxylic acid polymer under hydrothermal conditions to form a silica-acid hybrid; then, it is self-assembled with graphene oxide to obtain a graphene oxide-silica composite; a reducing agent is further added and the mixture is filtered to form a filter cake; finally, it is calcined in an oxygen-free environment, cooled, and compressed to obtain the final product. This method is simple, low-cost, and not limited by the size of the raw materials, meeting various industrial production requirements; the obtained product effectively enhances the specific capacity and cycle stability of lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of materials chemistry, specifically relating to a method for preparing a super self-assembled graphene silicon battery anode material. Background Technology

[0002] Graphene is a single-layer, two-dimensional material composed of carbon atoms, possessing excellent electrical and thermal conductivity, mechanical strength, and chemical stability. These superior properties have led to its widespread application in various fields, including electronics, optoelectronics, catalysts, and energy storage.

[0003] Silicon materials possess high theoretical capacity in the field of lithium-ion battery anodes, but issues such as capacity decay, volume change, and mechanical stability have consistently hampered their performance in practical applications. In recent years, combining graphene with silicon materials as anode materials for lithium-ion batteries has attracted considerable attention.

[0004] Graphene, as a coating layer for silicon materials, can alleviate the capacity decay and volume change problems of silicon materials, while improving their electrical conductivity and mechanical strength. The high specific surface area and tunable surface properties of graphene can also promote the diffusion and intercalation / deintercalation reactions of lithium ions within the anode material, thereby improving the energy density and cycle life of lithium-ion batteries. Graphene-silicon composite materials have attracted much attention as a high-performance lithium-ion battery anode material, possessing advantages such as high specific energy, high electrical conductivity, high mechanical strength, and low volume expansion, which can effectively improve the energy density and cycle life of lithium-ion batteries.

[0005] Currently, the development of graphene-silicon composite materials mainly focuses on the following aspects: optimizing the microstructure and chemical composition of silicon anode materials to improve their stability and cycle life; studying the processing technology and surface modification methods of graphene to improve its compatibility and dispersibility with silicon materials; exploring the feasibility of preparing large-scale graphene-silicon composite materials and studying their application performance in lithium-ion batteries.

[0006] Overcoming the aforementioned difficulties, the following industrial production challenges must also be considered to achieve mass production and application of graphene-silicon anode materials. These challenges include: high manufacturing costs: both graphene and silicon are high-cost materials, and the cost of manufacturing graphene-silicon composites is also high; reducing manufacturing costs is a significant challenge; insufficient material stability: graphene-silicon composites are prone to loosening, peeling, and breakage during long-term cycling, leading to decreased battery performance; and high difficulty in battery manufacturing: lithium-ion batteries are complex systems involving multiple processes and materials; achieving an efficient, stable, and reliable production process requires further exploration. Summary of the Invention

[0007] To address the problems of poor conductivity, poor stability, and difficulties in industrialization of existing silicon solar cells, this invention provides a method for preparing a super self-assembled graphene silicon solar cell anode. This method is simple, low-cost, and suitable for industrial applications.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] A method for preparing a self-assembled graphene-silicon battery anode material includes the following steps:

[0010] (1) Reaction of silica with organic carboxylic acids or carboxylic acid polymers under hydrothermal conditions in the absence of oxygen to obtain silica hybrids;

[0011] (2) The graphene oxide dispersion was added dropwise to the silica hybrid dispersion, and then the process was heated-cooled to obtain a graphene oxide-silica composite solution.

[0012] (3) Add a reducing agent to the graphene oxide-silica composite solution and filter to obtain a filter cake;

[0013] (4) After calcining the filter cake in an oxygen-free environment, cool and compress it to obtain a self-assembled graphene silicon battery anode material.

[0014] In step (1), the concentration of organic carboxylic acid or carboxylic acid polymer is 4 g / L-180 g / L; the mass ratio of organic carboxylic acid or carboxylic acid polymer to silicon dioxide is 1:30-6:1.

[0015] In step (1), preferably, the organic carboxylic acid can be a dicarboxylic acid or a polycarboxylic acid, such as glutamic acid, citric acid, tartaric acid or phthalic acid; the carboxylic acid polymer can be a polymer of carboxylic acids containing hydroxyl or phenolic hydroxyl groups, such as polylactic acid, tannin, etc., which can be degraded or partially degraded into monomeric carboxylic acids under hydrothermal conditions.

[0016] In step (1), the hydrothermal reaction temperature is between 80℃ and 360℃; preferably, the hydrothermal reaction time is 1-6h; preferably, oxygen is isolated by argon or nitrogen.

[0017] In step (2), the mass ratio of graphene oxide to silica hybrid is 1:100-2:1; the concentration of graphene oxide is 0.1g / L-18g / L.

[0018] In step (2), graphene oxide is slowly added to the continuously ultrasonically dispersed silica hybrid solution; the dropping rate is 1 mL / min-10 mL / min.

[0019] In step (2), the heating temperature is 50℃-99℃; the cooling temperature is 0℃-10℃. Repeated heating and cooling can promote a complete reaction, reduce agglomeration, and enhance the structural strength and stability of the product.

[0020] In step (3), the mass ratio of graphene oxide-silica composite to reducing agent is 60-4:1; the reducing agent is selected from one or more of charcoal, carbon black, graphite and activated carbon.

[0021] In step (4), the calcination temperature is 800℃-1900℃; preferably, the heating rate during calcination is 5℃ / min-25℃ / min. Calcination must be carried out in the absence of oxygen, and the inert atmosphere is argon or nitrogen.

[0022] A self-assembled graphene silicon battery anode material obtained by the above preparation method and the lithium-ion battery prepared therefrom.

[0023] The present invention also provides

[0024] The product prepared by this method can effectively enhance the specific capacity and cycle stability of silicon solar cells. The organic acid acidification process effectively disperses silica particles, functionalizing them and facilitating subsequent capture of graphene oxide for self-assembly. This also effectively increases the silicon loading and specific capacity. The ultrasonic and peristaltic crushing processes during self-assembly prevent silicon-based particle agglomeration, improving the structural stability of the product during charge and discharge. This method is simple, low-cost, and not limited by the size of the raw materials, meeting various industrial production requirements.

[0025] The present invention has the following advantages:

[0026] The present invention discloses a method for preparing a self-assembled graphene-silicon battery anode material. This method utilizes an organically acidified silica hybrid to rapidly self-assemble with graphene oxide. After effective coating of silica with graphene oxide, a reducing agent is added, and under high temperature conditions, silica is reduced to elemental silicon, and graphene oxide is reduced back to graphene, yielding a graphene-silicon composite material for use as a battery anode. The anode material prepared by this method exhibits excellent dispersibility and compatibility between graphene and silicon, and its structure is stable and resistant to breakage, effectively improving the stability and cycle life of the anode. Furthermore, the use of low-cost chemical methods to prepare graphene oxide and silica significantly reduces costs. Additionally, this method is simple, efficient, and stable, unaffected by the size of the raw materials, meeting the requirements of large-scale industrial production and achieving finished product sizes of up to 10m × 10m. The graphene silicon battery has a reversible specific capacity of more than 2500 mAh / g for the first time as the negative electrode, and can reach up to about 3100 mAh / g. After 300 cycles, it can still maintain more than 82% of the capacity, and can reach more than 91% in some cases. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the preparation process of self-assembled graphene silicon battery anode material;

[0028] Figure 2It is a reactor for self-assembling graphene silicon battery anode materials. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the present invention is not limited to the following embodiments.

[0030] Example 1: Preparation of self-assembled graphene silicon battery anode material

[0031] (1) 60g of nano silica was added to 500mL of gallic tannin (15g / L) solution and ultrasonically dispersed for 30 minutes. Then it was transferred to a hydrothermal reactor and heated to 360℃ for 6 hours under normal pressure and nitrogen to obtain silica hybrid.

[0032] (2) Connection as follows Figure 2 The cold-hot cycle reactor shown has two round-bottom flasks connected at their bottoms by a "U"-shaped pipe, with a pump connected to the pipe. The mouths of the two round-bottom flasks are connected by an H-shaped pipe, and one of the flasks has a feeding port. The flask with the feeding port is placed in an ultrasonic water bath as a heating flask, and the other flask is placed in an ice bath as a cooling flask.

[0033] After drying the above-mentioned silica hybrid, add Figure 2 In the reactor shown, 50g of graphene oxide was weighed and placed in a heating flask containing 500mL of distilled water. Ultrasonic treatment was initiated and the mixture was continuously sown to ensure thorough dispersion, maintaining the water bath temperature outside the container at 99℃. 100mL of 18g / L graphene oxide was slowly added dropwise (at a rate of 10mL / min), allowing it to rapidly self-assemble with the silica hybrid to form a graphene oxide-silica composite under ultrasonic conditions. After the graphene oxide addition was complete, a peristaltic pump was quickly activated, transferring 200mL of water from the cooling flask (4℃) from the bottom to the heating flask via a peristaltic pump (at a rate of 2mL / min). Meanwhile, the graphene oxide-silica composite solution in the heating flask flowed through the upper conduit to the top of the cooling flask, creating a circulation. This alternating hot and cold environment promoted a complete reaction of the composite. After 4 hours of circulation, the peristaltic pump was stopped, and the mixture was filtered and dried to obtain graphene oxide-silica composite particles.

[0034] (3) Weigh 40g of the above graphene oxide-silica composite particles into 200mL of distilled water, add 10g of charcoal as a reducing agent, ultrasonically disperse for 30 minutes, transfer the mixed solution to a filter (under shaking conditions) to form a filter cake;

[0035] (4) The filter cake is calcined in an oxygen-free environment. Argon gas is used to isolate the air. The calcination temperature is 1900℃ and the heating rate is 25℃ / min. After reaching the set temperature, it is calcined for 3 hours and then cooled. The graphene-silicon composite material after charcoal reduction is taken out and compressed by 97% to form a self-assembled graphene-silicon battery anode material.

[0036] Example 2: Preparation of self-assembled graphene silicon battery anode material

[0037] (1) 60g of nano silica was added to 500mL of glutamic acid (180g / L) solution and ultrasonically dispersed for 30 minutes. Then it was transferred to a hydrothermal reactor and heated to 80℃ for 6 hours under normal pressure and nitrogen to obtain silica hybrid.

[0038] (2) After drying the above-mentioned silica hybrid, weigh 50g and put it into Figure 2 In a heating flask containing 500 mL of distilled water on the left, ultrasound was turned on and continuously applied to ensure thorough dispersion, maintaining the water bath temperature outside the container at 50°C. 100 mL of 5 g / L graphene oxide was slowly added dropwise (at a rate of 1 mL / min), allowing it to rapidly self-assemble with the silica hybrid to form a graphene oxide-silica composite under ultrasound. After the graphene oxide addition was complete, a peristaltic pump was quickly turned on, transferring 200 mL of water from a cooling flask (4°C) from the bottom to the heating flask via a peristaltic pump (at a rate of 10 mL / min). Meanwhile, the graphene oxide-silica composite solution in the heating flask flowed through the upper conduit into the top of the cooling flask, creating a circulation. This alternating hot and cold environment promoted a complete reaction of the composite. After 10 hours of circulation, the peristalsis was stopped, and the mixture was filtered and dried to obtain graphene oxide-silica composite particles.

[0039] (3) Weigh 40g of the above graphene oxide-silica composite particles into 200mL of distilled water, add 1g of carbon black as a reducing agent, ultrasonically disperse for 30 minutes, transfer the mixed solution to a filter (under shaking conditions) to form a filter cake;

[0040] (4) The filter cake is calcined in the absence of oxygen. Nitrogen is used to isolate the air. The calcination temperature is 800℃ and the heating rate is 15℃ / min. After reaching the set temperature, it is calcined for 2 hours and then cooled. The graphene-silicon composite material after carbon black reduction is taken out and compressed by 97% to form a self-assembled graphene-silicon battery anode material.

[0041] Example 3: Preparation of self-assembled graphene silicon battery anode material

[0042] (1) 60g of nano-silica was added to 500mL of phthalic acid (4g / L) solution and ultrasonically dispersed for 30 minutes. Then it was transferred to a hydrothermal reactor and heated to 230℃ for 2 hours under normal pressure and nitrogen to obtain silica hybrid.

[0043] (2) After drying the above-mentioned silica hybrid, weigh 50g and put it into Figure 2In a heating flask containing 500 mL of distilled water on the left, ultrasound was turned on and continuously applied to ensure thorough dispersion, maintaining the water bath temperature outside the container at 80°C. 100 mL of 12 g / L graphene oxide was slowly added dropwise (at a rate of 5 mL / min), allowing it to rapidly self-assemble with the silica hybrid to form a graphene oxide-silica composite under ultrasound. After the graphene oxide addition was complete, a peristaltic pump was quickly turned on, transferring 200 mL of water from a cooling flask (4°C) from the bottom to the heating flask via a peristaltic pump (at a rate of 12 mL / min). Meanwhile, the graphene oxide-silica composite solution in the heating flask flowed through the upper conduit to the top of the cooling flask, creating a circulation. This alternating hot and cold environment promoted a complete reaction of the composite. After 6 hours of circulation, the peristalsis was stopped, and the mixture was filtered and dried to obtain graphene oxide-silica composite particles.

[0044] (3) Weigh 40g of the above graphene oxide-silica composite particles into 200mL of distilled water, add 6g of graphite as a reducing agent, ultrasonically disperse for 50 minutes, transfer the mixed solution to a filter (under shaking conditions) to form a filter cake;

[0045] (4) The filter cake is calcined in an oxygen-free environment. Argon gas is used to isolate the air. The calcination temperature is 1700℃ and the heating rate is 20℃ / min. After reaching the set temperature, it is calcined for 1 hour and then cooled. The graphene-silicon composite material after charcoal reduction is taken out and compressed by 97% to form a self-assembled graphene-silicon battery anode material.

[0046] Example 4: Preparation of self-assembled graphene silicon battery anode material

[0047] (1) 60g of nano silica was added to 500mL of tartaric acid (5g / L) solution and ultrasonically dispersed for 30 minutes. Then it was transferred to a hydrothermal reactor and heated to 300℃ for 3 hours under normal pressure and nitrogen to obtain silica hybrid.

[0048] (2) After drying the above-mentioned silica hybrid, weigh 50g and put it into Figure 2 In a heating flask containing 500 mL of distilled water on the left, ultrasound was turned on and continuously applied to ensure thorough dispersion, maintaining the water bath temperature outside the container at 90°C. 100 mL of 12 g / L graphene oxide was slowly added dropwise (at a rate of 5 mL / min), allowing it to rapidly self-assemble with the silica hybrid to form a graphene oxide-silica composite under ultrasound. After the graphene oxide addition was complete, a peristaltic pump was quickly turned on, transferring 200 mL of water from a cooling flask (10°C) from the bottom to the heating flask via a peristaltic pump (at a rate of 1 mL / min). Meanwhile, the graphene oxide-silica composite solution in the heating flask flowed through the upper conduit into the top of the cooling flask, creating a circulation. This alternating hot and cold environment promoted a complete reaction of the composite. After 12 hours of circulation, the peristalsis was stopped, and the mixture was filtered and dried to obtain graphene oxide-silica composite particles.

[0049] (3) Weigh 40g of the above graphene oxide-silica composite particles into 200mL of distilled water, add 6g of charcoal as a reducing agent, ultrasonically disperse for 40 minutes, transfer the mixed solution to a filter (under shaking conditions) to form a filter cake;

[0050] (4) The filter cake is calcined in an oxygen-free environment. Argon gas is used to isolate the air. The calcination temperature is 1200℃ and the heating rate is 5℃ / min. After reaching the set temperature, it is calcined for 1 hour and then cooled. The graphene-silicon composite material after charcoal reduction is taken out and compressed by 97% to form a self-assembled graphene-silicon battery anode material.

[0051] Comparative Example 1: Preparation of graphene oxide-porous carbon / sulfur composite material

[0052] Graphene-silicon anode materials were prepared according to the method described in "Preparation and Electrochemical Performance Study of Graphene / Silicon Anode Materials" (Du Xia, 2013):

[0053] (1) Preparation of graphene: graphene oxide was vacuum sintered at 800℃ for 1.5 hours under argon protection to obtain graphene, which was labeled as TRG; a small amount of graphene oxide powder was pressed into tablets and then treated with a 700W microwave oven at high temperature for 2 minutes to obtain fluffy graphene, which was labeled as MSG.

[0054] (2) Preparation of silicon / graphene: First, a certain amount of graphene oxide was dissolved in a mixture of water and ethanol and sonicated to obtain a yellow-brown gel-like liquid. Then, a certain amount of silicon was added, and sonication was continued to disperse it into a suspension. After mechanical stirring at 55°C for 8 hours, rotary evaporation was performed. Finally, the viscous substance was vacuum dried at 60°C. After drying, vacuum thermal reduction was performed in a tube furnace to obtain SG1. Next, a certain amount of MSG was added to a mixture of water and ethanol, ultrasonically dispersed, and mechanically stirred at 55°C for 12 hours. Finally, it was dried to obtain SG2.

[0055] Application Example 1: Application of self-assembled graphene silicon battery anode material in silicon batteries

[0056] The battery was assembled according to the method described in "Preparation and Electrochemical Performance Study of Graphene / Silicon Anode Materials" (Du Xia, 2013):

[0057] The active material self-assembled graphene silicon battery anode material, SG1 or SG2, was mixed into a slurry with a ratio of m(active material):m(acetylene black):m(PVDF) = 75:15:10. This slurry was coated onto the current collector, dried, and then punched and pressed into sheets. The sheets were then vacuum-dried at 120°C for 12 hours, followed by vacuum heat treatment in a tube furnace at 300°C for 5 hours. The counter electrode used in the battery was a lithium sheet, and the electrolyte was a 1.0M LiPF6 organic solution with a V(EC):V(DEC):V(DMC) = 1:1:1. The separator was a Celgard 2400 membrane. The battery was subjected to constant rate (0.2C) charge-discharge tests using a LAND battery testing system with a scan rate of 0.2mV / s, a voltage range of 0V-1.5V, and a frequency range of 10Hz. -2 -10 5 Hz.

[0058] Table 1 Electrochemical performance of different anode materials

[0059]

[0060] The test results of the aforementioned batteries are shown in Table 1: During the first discharge, the self-assembled graphene-silicon battery anode material exhibits a higher specific capacity, and the battery maintains a higher specific capacity even after 300 charge-discharge cycles. Compared to the direct mixing of graphene and silicon particles in Comparative Example 1, the organic acid acidification process effectively disperses the silicon dioxide particles, functionalizing them and facilitating subsequent capture of graphene oxide for self-assembly. This also effectively increases the silicon loading and specific capacity. The continuous ultrasonication and peristalsis during the self-assembly process effectively prevent the aggregation of graphene oxide and silicon dioxide particles, ensuring uniform and effective coating of silicon dioxide with graphene oxide. Subsequent reduction to a highly efficient and stable graphene-coated silicon structure results in higher cycle stability.

Claims

1. A method for preparing a self-assembled graphene-silicon battery anode material, characterized in that, Includes the following steps: (1) React silicon dioxide with organic carboxylic acid or carboxylic acid polymer under hydrothermal conditions in the absence of oxygen to obtain a silica hybrid; (2) The graphene oxide dispersion was added dropwise to the continuously ultrasonically dispersed silica hybrid dispersion, and then the heating-cooling cycle was used to obtain the graphene oxide-silica composite solution. (3) Add a reducing agent to the graphene oxide-silica composite solution and filter to obtain a filter cake; (4) After calcining the filter cake in an oxygen-free environment, cool and compress it to obtain a self-assembled graphene silicon battery anode material. In step (1), the hydrothermal reaction temperature is between 80℃ and 360℃; the hydrothermal reaction time is 1-6 hours. In step (2), the heating temperature is 50℃-99℃; the cooling temperature is 0℃-10℃. In step (4), the calcination temperature is 800℃-1900℃; In step (3), the reducing agent is selected from one or more of charcoal, carbon black, graphite and activated carbon.

2. The preparation method according to claim 1, characterized in that, In step (1), the organic carboxylic acid is a dicarboxylic or polycarboxylic acid; the carboxylic acid polymer is a polymer of carboxylic acids containing hydroxyl or phenolic hydroxyl groups.

3. The preparation method according to claim 1, characterized in that, In step (1), the organic carboxylic acid is selected from glutamic acid, citric acid, tartaric acid or phthalic acid; the carboxylic acid polymer is selected from polylactic acid or tannin.

4. The preparation method according to claim 1, characterized in that, In step (1), the concentration of organic carboxylic acid or carboxylic acid polymer is 4 g / L-180 g / L; the mass ratio of organic carboxylic acid or carboxylic acid polymer to silica is 1:30-6:1; In step (2), the mass ratio of graphene oxide to silica hybrid is 1:100-2:1; the concentration of graphene oxide is 0.1 g / L-18 g / L. In step (3), the mass ratio of graphene oxide-silica composite to reducing agent is 60-4:

1.

5. The preparation method according to claim 1, characterized in that, In step (2), the dropping rate of the graphene oxide dispersion is 1 mL / min-10 mL / min; In step (4), the heating rate of calcination is 5℃ / min-25℃ / min.

6. A self-assembled graphene silicon battery anode material obtained by any one of the preparation methods of claims 1-5 and a lithium-ion battery thereof.

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