Metal-doped spherical porous carbon and application of metal-doped spherical porous carbon in silicon-carbon composite material

Abstract

The invention discloses metal-doped spherical porous carbon and application of the metal-doped spherical porous carbon to a silicon-carbon composite material. The preparation method comprises the following steps: adding amino acid, silicon dioxide and a metal compound into an organic alkali solution, uniformly mixing, transferring into a high-pressure reaction kettle, carrying out hydrothermal reaction, soaking with a sodium hydroxide solution, etching, and freeze-drying to obtain metal-doped spherical porous carbon; the method for preparing the silicon-carbon composite material by applying the metal-doped silicon-carbon composite material comprises the following steps of: introducing silane gas to perform deposition and passivation coating of the nano silicon to obtain the metal-doped silicon-carbon composite material. The silicon-carbon composite material prepared by the invention is applied to the lithium ion battery, and has the advantages of good power performance, low expansion and the like.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material preparation, specifically a metal-doped spherical porous carbon, and also relates to the application of this metal-doped spherical porous carbon in silicon-carbon composite materials. Background Technology

[0002] Currently, commercially available silicon-carbon materials mainly consist of porous carbon and deposited nano-silicon. Due to its porous structure, porous carbon is easily crushed under high compaction pressure, leading to exposure of the core silicon and reducing its cycling and storage performance. Spherical structures, with their advantages of high yield, strong deformation capability, and easily controllable pore size, represent a novel type of porous carbon material. However, they still suffer from poor electronic conductivity. Therefore, it is necessary to dope them with metal or non-metal compounds to improve the electronic conductivity and reduce material expansion. Chinese Patent Publication No. CN118495501A, published on August 16, 2024, discloses a spherical porous silicon-carbon composite material, its preparation method, and its application. The preparation method involves adding polystyrene microspheres to a resin solution, adding scandium-metal-organic framework composite material for uniform dispersion, drying, carbonization, and steam activation to obtain the porous carbon material. However, because its metal-organic framework does not contain lithium, it is not conducive to lithium-ion insertion / extraction during charge and discharge, resulting in poor performance in reducing irreversible capacity and improving initial efficiency and storage performance. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a metal-doped spherical porous carbon that is applied to lithium-ion batteries and has good power performance, low expansion, and good storage performance.

[0004] Another object of the present invention is to provide the application of the metal-doped spherical porous carbon in silicon-carbon composite materials.

[0005] The present invention provides a metal-doped spherical porous carbon, prepared by the following method: According to the mass ratio of amino acids:silica:metal compound:organic acid = 100:10-30:1-5:500-1500, amino acids, template agent silica, and metal compound are added to a 10-30wt% organic base solution and mixed evenly. Then, the mixture is transferred to a high-pressure reactor and reacted at 100-200℃ for 1-6 hours. The mixture is then immersed in a 10wt% sodium hydroxide solution for 24 hours for etching. The resulting material is freeze-dried at -40℃ for 24 hours to obtain metal-doped spherical porous carbon.

[0006] The metal compound is one of lithium stearate, lithium octadecanoate, lithium acetate, lithium oxalate, lithium formate, or lithium oleate.

[0007] The organic base is one of trimethylamine, triethylamine, tri-n-propylamine, pyridine, or methylpyridine.

[0008] The present invention relates to the application of metal-doped spherical porous carbon in silicon-carbon composite materials.

[0009] The above-mentioned method for applying metal-doped spherical porous carbon to silicon-carbon composite materials includes: transferring metal-doped spherical porous carbon to a fluidized bed, introducing silane gas through silane pyrolysis at a temperature of 450-550℃ at a flow rate of 100-500 SCCM for 60-600 min, then introducing heteroatom gas and raising the temperature to 600-900℃ at a flow rate of 50-200 SCCM for 30-300 min, then cooling the temperature to 500-600℃ and introducing carbon source gas at a flow rate of 100-500 SCCM for 30-300 min for passivation coating, thereby obtaining metal-doped silicon-carbon composite materials.

[0010] The heteroatom gas is one of nitrogen trifluoride, boron trifluoride, or phosphorus pentafluoride.

[0011] The carbon source gas is one of methane, ethane, ethylene, acetylene, or propyne.

[0012] Compared with existing technologies, this invention has significant advantages. As can be seen from the above technical solution: This invention uses silicon dioxide as a template and obtains large-pore porous carbon through dehydration reaction and carbonization between amino acids and organic acids. This porous carbon has uniform pore size and high pore volume, allowing it to accommodate more nano-silicon and improve the specific capacity of the material. Simultaneously, the large-pore porous carbon is doped with metal, improving the electronic conductivity of the material, resulting in metal-doped spherical porous carbon with high electronic conductivity, thus improving power performance. Firstly, nano-silicon is deposited on the metal-doped spherical porous carbon using a silane pyrolysis method to improve specific capacity, and heteroatoms are deposited to improve the electronic conductivity of the material. Finally, amorphous carbon is deposited on the outer layer to improve the electronic conductivity of the material and isolate the core nano-silicon from the electrolyte, thus improving storage performance. Attached Figure Description

[0014] Figure 1 The image shows a SEM image of the metal-doped silicon-carbon composite material prepared in Example 1. Detailed Implementation

[0015] Example 1: A metal-doped spherical porous carbon is prepared by the following method: 100g of amino acids, 20g of silica template agent, and 3g of lithium stearate were added to 1000g of 20wt% trimethylamine solution, mixed evenly, and transferred to a high-pressure reactor. The mixture was reacted at 150℃ for 3h, followed by immersion and etching in 10wt% sodium hydroxide solution for 24h. The resulting material was then freeze-dried at -40℃ for 24h to obtain metal-doped spherical porous carbon.

[0016] The obtained metal-doped spherical porous carbon was used to prepare silicon-carbon composite materials. The method included: transferring the metal-doped spherical porous carbon into a fluidized bed, and passing silane gas at a flow rate of 300 SCCM for 300 min at a temperature of 500 °C using the silane pyrolysis method. Then, nitrogen trifluoride gas was introduced, and the temperature was raised to 800 °C. The gas was then passed through at a flow rate of 100 SCCM for 150 min. After that, the temperature was lowered to 550 °C, and ethylene gas was introduced at a flow rate of 300 SCCM for 150 min to passivate and coat the carbon, thereby obtaining the metal-doped silicon-carbon composite material.

[0017] Example 2: A metal-doped spherical porous carbon is prepared by the following method: 100g of amino acids, 10g of silica template agent, and 1g of lithium octadecate were added to 500g of 30wt% triethylamine solution, mixed evenly, and transferred to a high-pressure reactor. The mixture was reacted at 100℃ for 6h, followed by immersion and etching in 10wt% sodium hydroxide solution for 24h. The resulting material was then freeze-dried at -40℃ for 24h to obtain metal-doped spherical porous carbon.

[0018] The obtained metal-doped spherical porous carbon was used to prepare silicon-carbon composite materials. The method included: transferring the metal-doped spherical porous carbon into a fluidized bed, and passing silane gas at a flow rate of 100 SCCM for 600 min at a temperature of 550 °C using a silane pyrolysis method. Then, boron trifluoride gas was passed through, and the temperature was raised to 600 °C. The gas was then passed through at a flow rate of 200 SCCM for 30 min. After that, the temperature was lowered to 500 °C, and methane gas was passed through at a flow rate of 100 SCCM for 300 min to passivate and coat the carbon, thereby obtaining the metal-doped silicon-carbon composite material.

[0019] Example 3: A metal-doped spherical porous carbon is prepared by the following method: 100g of amino acids, 30g of silica template agent, and 5g of lithium acetate were added to 1500g of 10wt% tri-n-propylamine solution, mixed evenly, and transferred to a high-pressure reactor. The mixture was reacted at 200℃ for 1h, followed by immersion and etching in 10wt% sodium hydroxide solution for 24h. The resulting material was then freeze-dried at -40℃ for 24h to obtain metal-doped spherical porous carbon.

[0020] The obtained metal-doped spherical porous carbon was used to prepare silicon-carbon composite materials. The method included: transferring the metal-doped spherical porous carbon into a fluidized bed, and passing silane gas at a flow rate of 500 SCCM for 60 min at a temperature of 450 °C using silane pyrolysis, then switching to phosphorus pentafluoride gas and raising the temperature to 900 °C for 300 min at a flow rate of 50 SCCM, then cooling to 600 °C and passing acetylene gas at a flow rate of 500 SCCM for 30 min for passivation coating, thus obtaining the metal-doped silicon-carbon composite material.

[0021] Comparative Example 1: A method for preparing silicon-carbon composite materials using metal-doped spherical porous carbon includes the following steps: unlike Example 1, lithium stearate is not added, but otherwise the method is the same as Example 1.

[0022] Comparative Example 2: A method for preparing silicon-carbon composite materials using metal-doped spherical porous carbon includes: unlike Example 1, using commercially available granular porous carbon (manufacturer: Kuraray Co., Ltd., Japan, model: YP-50F) instead of metal-doped spherical porous carbon, otherwise the same as in Example 1.

[0023] Comparative Example 3: A method for preparing silicon-carbon composite materials using metal-doped spherical porous carbon includes the following steps: unlike Example 1, nitrogen trifluoride gas is not introduced, but otherwise the method is the same as Example 1.

[0024] Experiment 1: SEM Test Figure 1 The image shows a SEM image of the silicon-carbon composite material prepared in Example 1. As can be seen from the image, the material exhibits a spherical structure with a uniform size distribution and a particle size between 5 and 10 µm.

[0025] Experimental Example 2: Physicochemical Performance Test The specific surface area and tap density of each silicon-carbon composite material were tested according to the national standard GB / T 38823-2020 "Silicon-Carbon". The powder conductivity of each composite material was tested using a four-probe tester. The pore size and pore volume of the silicon-carbon composite materials in Examples 1-3 and Comparative Examples 1-3 were also tested. The test results are shown in Table 1 below.

[0026] Test Example 3: Button Battery Test The silicon-carbon composite materials corresponding to Examples 1-3 and Comparative Examples 1-3 were used as negative electrode materials for lithium-ion batteries to prepare coin cells according to the following method: A binder, conductive agent, and solvent were added to the corresponding silicon-carbon composite materials, stirred to form a slurry, coated onto copper foil, and dried and rolled to obtain a negative electrode sheet. The binder used was LA132, the conductive agent was SP (conductive carbon black), and the solvent was NMP. The ratio of composite material, SP, LA132, and NMP was 80g:10g:10g:220mL. The electrolyte was a solution with LiPF6 as the electrolyte and a concentration of 1mol / L. The solvent was a mixture of EC and DEC with a volume ratio of 1:1. The lithium metal sheet was used as the counter electrode, and the separator was a polypropylene (PP) membrane.

[0027] Each button cell was assembled in an argon-filled glove box, and then its electrochemical performance was tested. Specifically, the electrochemical performance was tested on a Wuhan Landian CT2001A battery tester, with a charge / discharge voltage range of 0.005V to 2.0V and a charge / discharge rate of 0.1C. The test results are shown in Table 1 below.

[0028] The negative electrode of the above coin cell was also subjected to full-charge expansion. The specific test process was as follows: the thickness D1 of the negative electrode of the rolled coin cell was measured, and then the full-charge thickness D2 of the negative electrode was dissected at 100% SOC of the coin cell. Then the expansion rate was calculated (expansion rate = (D1-D2) / D1*100%). The test results are shown in Table 1 below.

[0029] Table 1 As can be seen from the data in Table 1 above, the specific capacity and first-time efficiency of the silicon-carbon composite materials prepared in Examples 1-3 of this application are significantly better than those in Comparative Examples 1-3. The reason may be that by doping lithium into porous carbon, the electronic conductivity of the material powder is improved and the defects of the material are reduced, thereby improving the first-time efficiency; and the polarization is reduced, thereby improving the specific capacity of the material.

[0030] Experiment 4: Performance Test of Flexible Packaging The composite materials corresponding to Examples 1-3 and Comparative Examples 1-3 were doped with 90% artificial graphite as negative electrode materials (i.e., negative electrode sheets), and were combined with the positive electrode ternary material (LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 The battery is assembled with O2, electrolyte, and separator to form a 5Ah soft-pack battery. The separator is Celegard 2400, and the electrolyte is LiPF6 solution (the solvent is a mixed solution of EC and DEC with a volume ratio of 1:1 and the concentration of LiPF6 is 1.3mol / L).

[0031] The following performance tests were performed on each pouch battery: a. Liquid absorption capacity test: Use a 1mL burette and draw VmL of electrolyte. Add one drop to the surface of each negative electrode and time the test until the electrolyte is completely absorbed. Record the time t. The test results are shown in Table 2 below.

[0032] b. Liquid retention rate test: Calculate the theoretical liquid absorption capacity m1 of each negative electrode according to its parameters, and weigh the negative electrode as m2. Then, immerse the negative electrode in the electrolyte for 24 hours, weigh the negative electrode as m3, and calculate the liquid absorption capacity m3-m2 using the following formula: Liquid retention rate = (m3-m2)*100% / m1; the test results are shown in Table 2 below.

[0033] Table 2 As can be seen from Table 2, the liquid absorption and retention capacity of the silicon-carbon composite materials provided in Examples 1-3 is higher than that of Comparative Examples 1-3. The reason may be that the specific surface area of ​​the silicon-carbon composite materials provided in the embodiments of this application is larger, which can directly improve the liquid absorption and retention capacity of the silicon-carbon composite materials.

[0034] c. Ratio and cycling performance testing: Cycle performance and rate testing were performed on the prepared pouch cells. The test conditions for the cycle performance test are as follows: charge / discharge voltage range of 2.5 to 4.2V, temperature of 25±3.0℃, charge / discharge rate of 1.0C / 1.0C, and number of cycles of 500. The test conditions for the rate test are as follows: charge each battery to 4.2V at a rate of 2C and calculate the constant current charging capacity as A1. Then charge at 4.2V and a constant current of 0.1A for 2 hours and calculate the constant current capacity as A2. Then calculate the constant current ratio = A1 / (A1+A2)*100%, which is the constant current ratio. The test results are shown in Table 3 below.

[0035] D. High-temperature storage performance: The batteries of the examples and comparative examples were charged to full capacity at room temperature and cycled for three weeks at 2.5-4.2V. The charging capacity of the battery at full capacity was tested as B1. Then, the battery was placed in a high-temperature oven at 55°C and left to stand for 30 days. The capacity of the battery was then tested as B2. After that, the battery was discharged to 2.5V and charged to full capacity. The capacity of the battery was tested as B3. The charge retention of the battery was calculated as B2 / B1*100%, and the capacity recovery was calculated as B3 / B1*100%.

[0036] Table 3 As shown in Table 3, the rate capability, cycle performance, and high-temperature storage performance of the soft-pack lithium-ion batteries prepared using the silicon-carbon composite materials provided in Examples 1-3 are significantly better than those of Comparative Examples 1-3. The reasons may be as follows: the materials in the examples have high powder conductivity, which improves the constant current ratio of the materials; at the same time, the materials in the examples have high specific surface area, which improves the liquid retention performance of the materials and improves the cycle performance; and the materials in the examples are doped with lithium compounds, which reduces the loss of lithium ions under high temperature conditions and improves the high-temperature storage performance.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments without departing from the technical essence of the present invention shall still fall within the scope of the present invention.

Claims

1. A metal-doped spherical porous carbon, prepared by the following method: According to the mass ratio of amino acids:silica:metal compound:organic acid = 100:10-30:1-5:500-1500, amino acids, silica, and metal compounds are added to a 10-30wt% organic base solution and mixed evenly. Then, the mixture is transferred to a high-pressure reactor and reacted at 100-200℃ for 1-6 hours. The mixture is then immersed in a 10wt% sodium hydroxide solution for etching for 24 hours. The resulting material is freeze-dried at -40℃ for 24 hours to obtain metal-doped spherical porous carbon.

2. The metal-doped spherical porous carbon as described in claim 1, wherein: The metal compound is one of lithium stearate, lithium octadecanoate, lithium acetate, lithium oxalate, lithium formate, or lithium oleate.

3. The metal-doped spherical porous carbon as described in claim 1, wherein: The organic base is one of trimethylamine, triethylamine, tri-n-propylamine, pyridine, or methylpyridine.

4. Application of a metal-doped spherical porous carbon in silicon-carbon composite materials.

5. The method for applying metal-doped spherical porous carbon in silicon-carbon composite materials as described in claim 4, comprising: Metal-doped spherical porous carbon was transferred to a fluidized bed, and silane gas was introduced via silane pyrolysis at a temperature of 450-550℃ and a flow rate of 100-500 SCCM for 60-600 min. Then, heteroatom gas was introduced, and the temperature was raised to 600-900℃ and a flow rate of 50-200 SCCM was introduced for 30-300 min. The temperature was then lowered to 500-600℃, and carbon source gas was introduced at a flow rate of 100-500 SCCM for 30-300 min to passivate and coat the carbon, thus obtaining a metal-doped silicon-carbon composite material.

6. The method for applying metal-doped spherical porous carbon in silicon-carbon composite materials as described in claim 5, wherein: The heteroatom gas is one of nitrogen trifluoride, boron trifluoride, or phosphorus pentafluoride.

7. The method for applying metal-doped spherical porous carbon to silicon-carbon composite materials as described in claim 5, wherein: The carbon source gas is one of methane, ethane, ethylene, acetylene, or propyne.

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