Method for preparing hard carbon negative electrode material by modifying biomass

Abstract

The application discloses a method for preparing hard carbon negative materials by biomass modification, and relates to the field of sodium ion battery negative materials.The amino urea and aluminum complex introduced by biomass modification change the chemical properties of the surface of the hard carbon, provide more active sites for sodium ions, thereby accelerating the diffusion rate of the sodium ions and improving the battery capacity.The introduction of the aluminum complex helps to stabilize the surface structure of the hard carbon and reduce the structural damage in the charging and discharging process, thereby improving the initial coulombic efficiency of the battery.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery anode materials, and in particular to a method for preparing hard carbon anode materials by biomass modification. Background Technology

[0002] Lithium-ion batteries, as green and environmentally friendly energy storage devices, have been widely used in the electronics market, new energy vehicles, and other energy storage fields due to their outstanding advantages such as high energy density, long cycle life, and safety without pollution. However, with the continuous growth of market demand for lithium-ion batteries, problems such as lithium resource shortages and rising prices have seriously hindered their development. Sodium-ion batteries, due to their abundant resources, low price, and wide distribution, have attracted widespread attention and are expected to become a substitute for lithium-ion batteries.

[0003] Patent application CN202311603819.2 discloses a hard carbon anode material, a hard carbon anode sheet, and a sodium-ion secondary battery. The hard carbon anode material includes a first hard carbon particle, a second hard carbon particle, and a third hard carbon particle. The first hard carbon particle is a multi-faceted hard carbon particle, the second hard carbon particle is a hard carbon particle with few or no facets, and the third hard carbon particle is obtained by heating the first hard carbon particle, the second hard carbon particle, a carbon source, and a hot molten salt.

[0004] Patent application CN202311445666.3 discloses a negative electrode material, a negative electrode sheet, and a sodium-ion battery for sodium-ion batteries. The negative electrode material comprises a negative electrode active material and an organic additive. The organic additive contains at least two sodium sulfonate groups, at least one biphenyl functional group, and at least one azo functional group, with the benzene rings conjugated with the azo functional group. The organic additive used in this invention contains biphenyl and azo functional groups, and the conjugation between the benzene rings and between the benzene rings and the azo functional group allows for the formation of large delocalized π bonds. The biphenyl functional group is rigid, which can suppress the expansion of the negative electrode material during sodium insertion / extraction. Furthermore, the sodium sulfonate groups can both adsorb onto the negative electrode surface and accelerate the transfer of sodium ions on the negative electrode surface, and also reduce the consumption of electrolyte and active sodium ions on the negative electrode surface during sodium-ion battery formation.

[0005] Compared to lithium-ion batteries, sodium ions have an atomic radius that is more than 35% larger than that of lithium ions. The graphite anode, which is the mainstream material in lithium-ion batteries, cannot meet the requirements of sodium-ion batteries. Soft carbon materials have insufficient sodium storage capacity, so hard carbon anodes are the mainstream material used in sodium batteries.

[0006] Hard carbon materials offer diverse sodium storage locations and forms, resulting in a large theoretical capacity. Furthermore, hard carbon materials enable faster charging of the anode and address over-discharge safety issues, broadening the application scope of sodium batteries. However, hard carbon, as the preferred anode material, is still in the early stages of research and development. Materials prepared under current technological conditions still limit the capacity and initial coulombic efficiency of sodium-ion batteries to some extent. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing hard carbon anode materials through biomass modification. By modifying biomass, the battery capacity and initial coulombic efficiency are improved.

[0008] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0009] This invention provides a method for preparing hard carbon anode materials by modifying biomass, comprising the following steps:

[0010] (1) The biomass material is washed, dried, and then pre-carbonized in an air atmosphere to obtain the treated biomass material.

[0011] (2) The biomass material obtained in step (1) is subjected to wet ball milling, dried and then subjected to high-temperature carbonization under an inert atmosphere, followed by functional group modification.

[0012] The functionalization modification was performed using mercaptoacetic acid vapor plasma.

[0013] (3) The modified material in step (2) is washed and dried to obtain the hard carbon anode material.

[0014] Preferably, the biomass material is at least one of wood and bamboo. Coconut shell is selected as an example in this embodiment of the invention, but it is not limited thereto.

[0015] Ultrasonic washing can be used when washing biomass materials.

[0016] In some embodiments of the present invention, in step (1), the pre-carbonization conditions are: the pre-carbonization temperature is 200-450℃, and the heating rate is 1-10℃ / min.

[0017] In some embodiments of the present invention, in step (2), the conditions for wet ball milling are as follows: the mass ratio of material, ball, and anhydrous ethanol is 1:1.2-2.5:0.7-1.5, the ball milling time is 1-3 hours, and the ball milling speed is 65-130 rpm.

[0018] In some embodiments of the present invention, in step (2), the high-temperature carbonization conditions are: the high-temperature carbonization temperature is 1100-1600℃, and the high-temperature carbonization time is 2-6 hours;

[0019] The high-temperature carbonization process involves first heating and then cooling, with a heating rate of 0.5-5℃ / min and a cooling rate of 2-8℃ / min.

[0020] In some embodiments of the present invention, in step (2), the inert gas is at least one of nitrogen, argon, or helium.

[0021] The inert gas flow rate is 10-50 ml / min.

[0022] Preferably, in step (2), the method of functionalization modification is as follows:

[0023] T1: The high-temperature carbonized biomass material is placed in a radio frequency plasma generator. Under the conditions of power of 100-600W, mercaptoacetic acid vapor flow rate of 20-40mL / min, and plasma chamber pressure of 10-15Pa, the high-temperature carbonized biomass material is treated with radio frequency 13.56MHz glow plasma for 10-30min to obtain mercapto hard carbon.

[0024] T2: The thiol-based hard carbon prepared in step T1 undergoes a thiol-alkenyl addition reaction with 4-propenylthioaminourea under alkaline conditions, and a thiol-alkenyl addition reaction with aluminum acrylate to obtain a modified hard carbon anode material of aminourea and aluminum complex.

[0025] Further, in step T2, by weight, 100-120 parts of mercapto hard carbon, 4-7 parts of sodium methoxide, 1-5 parts of 4-propenylthioaminourea, and 0.05-0.5 parts of aluminum acrylate prepared in step T1 are mixed and stirred at 50-60°C, along with 3-6 parts of sodium tert-butoxide and 1000-1400 parts of ethanol. The mixture is stirred and reacted at 60-70°C for 50-90 minutes, and the ethanol is removed to obtain the hard carbon anode material.

[0026] The biomass-modified hard carbon anode material prepared by this method effectively improves battery capacity and initial coulombic efficiency, with battery capacity increasing by 28% and initial coulombic efficiency increasing by 20.5%.

[0027] In some embodiments of the present invention, in step (2), the washing is repeated with an acid solution and deionized water, wherein the acid solution is selected from hydrochloric acid, sulfuric acid, nitric acid, and acetic acid, and the concentration of the acid solution is 0.5-5M.

[0028] The present invention also provides a hard carbon anode material for sodium-ion batteries, which is prepared using the method described above.

[0029] The beneficial effects of this invention are:

[0030] This invention modifies the chemical properties of hard carbon surface through biomass modification, introducing aminourea and aluminum complexes to provide more active sites for sodium ions, thereby accelerating the diffusion rate of sodium ions and increasing battery capacity. The introduction of aluminum complexes helps stabilize the surface structure of hard carbon, reducing structural damage during charge and discharge processes, thus improving the battery's initial coulombic efficiency. Attached Figure Description Detailed Implementation

[0031] In view of the shortcomings of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention, which will be further explained below, including its implementation process and principles.

[0032] Example 1

[0033] A method for preparing hard carbon anode materials by biomass modification, comprising the following steps:

[0034] Step 1: Weigh 5g of coconut shell, ultrasonically wash (50kHz), and dry for later use;

[0035] Step 2: Transfer the material from Step 1 to a muffle furnace and heat it to 200°C at a heating rate of 10°C / min. Pre-carbonize for 2 hours in an air atmosphere, and then allow it to cool naturally to room temperature for later use.

[0036] Step 3: The material from Step 2 is wet-milled in a spherical mill at a mass ratio of material, spherical mill, and anhydrous ethanol of 1:1.2:0.7 for 1 hour at a milling speed of 65 rpm. After mixing evenly, it is dried and ready for use.

[0037] Step 4: Transfer the material from Step 3 to a tube furnace, introduce high-purity nitrogen gas at a flow rate of 10 ml / min, heat to 1100℃ at a heating rate of 5℃ / min, carbonize at high temperature for 2 hours, and then cool to room temperature at a cooling rate of 8℃ / min. The obtained hard carbon sample is then sent to an RF plasma generator for functionalization modification.

[0038] The method for functionalization modification is as follows:

[0039] T1: The hard carbon obtained in step 4 is then sent to an RF plasma generator for functionalization modification; it is spread out on a ceramic boat and placed in an RF plasma generator (LfeCorporation, LTA-302). Under the conditions of 100W power, 20mL / min flow rate of mercaptoacetic acid vapor, and 10Pa pressure in the plasma chamber, the hard carbon sample is treated with 13.56MHz glow discharge (RF) plasma for 10min. After the treatment, the gas is continued to be ventilated for 2min, and then the mercapto hard carbon is taken out.

[0040] T2: Add 100g of mercapto hard carbon, 4g of sodium methoxide, 1g of 4-propenylthiourea, and 0.1g of aluminum acrylate prepared in step T1 to the reactor. Mix and stir at 50°C for 110 min. Add 3g of sodium tert-butoxide and 1000g of ethanol. Stir and react at 60°C for 50 min. Distill off the ethanol to obtain the modified hard carbon sample.

[0041] Step 5: The modified hard carbon sample obtained in Step 4 is repeatedly washed with 0.5M hydrochloric acid and deionized water, and then dried to obtain the hard carbon anode material.

[0042] Example 2

[0043] A method for preparing hard carbon anode materials by biomass modification, comprising the following steps:

[0044] Step 1: Weigh 10g of coconut shell, ultrasonically wash (60kHz), and dry for later use;

[0045] Step 2: Transfer the material from Step 1 to a muffle furnace and heat it to 300°C at a heating rate of 6°C / min. Pre-carbonize for 3 hours in an air atmosphere, and then allow it to cool naturally to room temperature for later use.

[0046] Step 3: The material from Step 2 is wet-milled in a spherical mill at a mass ratio of material, sphericals, and anhydrous ethanol of 1:1.7:1 for 2 hours at a milling speed of 90 rpm. After mixing evenly, it is dried and ready for use.

[0047] Step 4: Transfer the material from Step 3 to a tube furnace, introduce argon gas at a flow rate of 25 ml / min, heat to 1250°C at a heating rate of 3°C / min, carbonize at high temperature for 3 hours, and then cool to room temperature at a cooling rate of 6°C / min. The obtained hard carbon sample is then sent to an RF plasma generator for functionalization modification.

[0048] The method for functionalization modification is as follows:

[0049] T1: The hard carbon obtained in step 4 is then sent to an RF plasma generator for functionalization modification; it is spread out on a ceramic boat and placed in an RF plasma generator (LfeCorporation, LTA-302). Under the conditions of 300W power, 30mL / min flow rate of mercaptoacetic acid vapor, and 10Pa pressure in the plasma chamber, the hard carbon sample is treated with 13.56MHz glow discharge (RF) plasma for 20min. After the treatment, the gas is continued to be ventilated for 2min, and then the mercapto hard carbon is taken out.

[0050] T2: Add 110g of mercapto hard carbon, 5g of sodium methoxide, 2.5g of 4-propenylthiourea, and 0.2g of aluminum acrylate prepared in step T1 to the reactor. Mix and stir at 55°C for 110 min. Add 4g of sodium tert-butoxide and 1100g of ethanol. Stir and react at 65°C for 65 min. Remove the ethanol by distillation to obtain the modified hard carbon sample.

[0051] Step 5: The modified hard carbon sample obtained in Step 4 is repeatedly washed with 2.5M sulfuric acid and deionized water, and then dried to obtain the hard carbon anode material.

[0052] Example 3

[0053] A method for preparing hard carbon anode materials by biomass modification, comprising the following steps:

[0054] Step 1: Weigh 15g of coconut shell, ultrasonically wash (70kHz), and dry for later use;

[0055] Step 2: Transfer the material from Step 1 to a muffle furnace and heat it to 380°C at a heating rate of 3°C / min. Pre-carbonize for 4 hours in an air atmosphere, and then allow it to cool naturally to room temperature for later use.

[0056] Step 3: The material from Step 2 is wet-milled in a spherical mill at a mass ratio of material, sphericals, and anhydrous ethanol of 1:2.1:1.3 for 2 hours at a milling speed of 105 rpm. After mixing evenly, it is dried and ready for use.

[0057] Step 4: Transfer the material from Step 3 to a tube furnace, introduce helium gas at a flow rate of 40 ml / min, heat to 1450℃ at a heating rate of 1.5℃ / min, carbonize at high temperature for 5 hours, and then cool to room temperature at a cooling rate of 4℃ / min. The obtained hard carbon sample is then sent to an RF plasma generator for functionalization modification.

[0058] The method for functionalization modification is as follows:

[0059] T1: The hard carbon obtained in step 4 is then sent to an RF plasma generator for functionalization modification; it is spread out on a ceramic boat and placed in an RF plasma generator (LfeCorporation, LTA-302). Under the conditions of 300W power, 30mL / min flow rate of mercaptoacetic acid vapor, and 15Pa pressure in the plasma chamber, the hard carbon sample is treated with 13.56MHz glow discharge (RF) plasma for 20min. After the treatment, the gas is continued to be ventilated for 2min, and then the mercapto hard carbon is taken out.

[0060] T2: Add 110g of mercapto hard carbon, 6g of sodium methoxide, 4g of 4-propenylthioaminourea, and 0.4g of aluminum acrylate prepared in step T1 to the reactor. Mix and stir at 55°C for 110 min. Add 5g of sodium tert-butoxide and 1300g of ethanol. Stir and react at 65°C for 80 min. Remove the ethanol by distillation to obtain the modified hard carbon sample.

[0061] Step 5: The modified hard carbon sample obtained in Step 4 is repeatedly washed with 4M hydrochloric acid and deionized water, and then dried to obtain the hard carbon anode material.

[0062] Example 4

[0063] A method for preparing hard carbon anode materials by biomass modification, comprising the following steps:

[0064] Step 1: Weigh 20g of coconut shell, ultrasonically wash (80kHz), and dry for later use;

[0065] Step 2: Transfer the material from Step 1 to a muffle furnace and heat it to 450°C at a heating rate of 1°C / min. Pre-carbonize for 5 hours in an air atmosphere, and then allow it to cool naturally to room temperature for later use.

[0066] Step 3: The material from Step 2 is wet-milled in a spherical mill at a mass ratio of material, spherical mill, and anhydrous ethanol of 1:2.5:1.5 for 3 hours at a milling speed of 130 rpm. After mixing evenly, it is dried and ready for use.

[0067] Step 4: Transfer the material from Step 3 to a tube furnace, introduce high-purity nitrogen gas at a flow rate of 50 ml / min, heat to 1600℃ at a heating rate of 0.5℃ / min, carbonize at high temperature for 6 hours, and then cool to room temperature at a cooling rate of 2℃ / min. The obtained hard carbon sample is then sent to an RF plasma generator for functionalization modification.

[0068] The method for functionalization modification is as follows:

[0069] T1: The hard carbon obtained in step 4 is then sent to an RF plasma generator for functionalization modification; it is spread out on a ceramic boat and placed in an RF plasma generator (LfeCorporation, LTA-302). Under the conditions of 600W power, 40mL / min flow rate of mercaptoacetic acid vapor, and 15Pa pressure in the plasma chamber, the hard carbon sample is treated with 13.56MHz glow discharge (RF) plasma for 20min. After the treatment, the gas is continued to be ventilated for 2min, and then the mercapto hard carbon is taken out.

[0070] T2: Add 120g of mercapto hard carbon, 7g of sodium methoxide, 5g of 4-propenylthioaminourea, and 0.5g of aluminum acrylate prepared in step T1 to the reactor. Mix and stir at 60°C for 110 min. Add 6g of sodium tert-butoxide and 1400g of ethanol. Stir and react at 70°C for 90 min. Remove the ethanol by distillation to obtain the modified hard carbon sample.

[0071] Step 5: Wash the modified hard carbon sample obtained in Step 4 repeatedly with 5M acetic acid and deionized water, and dry it to obtain the hard carbon anode material.

[0072] Comparative Example 1

[0073] In this comparative example, the hard carbon sample obtained in step 4 of the biomass modification process for preparing hard carbon anode materials was not sent to the radio frequency plasma generator for functionalization modification, and the other conditions were kept the same as in Example 1.

[0074] Comparative Example 2

[0075] In this comparative example, 4-propenylthiourea was not added during the functionalization modification process, and all other conditions were kept the same as in Example 1.

[0076] Test Example 1

[0077] The biomass-modified hard carbon anode material obtained in the above specific implementation is ground evenly with acetylene black and sodium carboxymethyl cellulose (CMC) in a mass ratio of 8:1:1. Then, an appropriate amount of deionized water is added to make a slurry, which is then evenly coated on copper foil using a coating machine. The slurry is placed in a vacuum drying oven and dried at 80°C for 12 hours. After that, it is prepared into a disc electrode with a diameter of 12 mm using a punching machine.

[0078] The electrode sheet obtained above was used as the negative electrode, a glass fiber (Whitman, GF / D) disc with a diameter of 19 mm was used as the separator, and a sodium metal sheet with a diameter of 12 mm and a thickness of 0.2 mm was used as the counter electrode and reference electrode. The electrolyte was a 1 mol / L sodium perchlorate / ethylene carbonate / dimethyl carbonate solution. The sodium-ion battery was assembled in a glove box filled with high-purity argon gas according to the construction of a CR2016 standard coin cell. The battery was charged and discharged on a battery test platform at a current density of 30 mA / g. The results are shown in Table 1.

[0079] Table 1

[0080]

[0081] The test results from the above specific implementation scheme show that the biomass-modified hard carbon anode material prepared by this method effectively improves the battery capacity and initial coulombic efficiency.

[0082] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a hard carbon negative electrode material by biomass modification, characterized in that, The method comprises the following steps: (1) washing and drying the biomass material, and then pre-carbonizing the biomass material in an air atmosphere to obtain a treated biomass material; (2) wet ball-milling the treated biomass material obtained in step (1), drying, and then high-temperature carbonizing the biomass material in an inert atmosphere, and then performing functional group modification; The method for functional group modification is: T1: placing the high-temperature carbonized biomass material in a radio frequency plasma generator, and treating the high-temperature carbonized biomass material with a radio frequency of 13.56 MHz for 10-30 min under the conditions that the power is 100-600 W, the flow rate of mercaptoacetic acid vapor gas is 20-40 mL / min, and the pressure in the plasma cavity is 10-15 Pa to obtain mercapto hard carbon; T2: mixing and stirring 100-120 parts of the mercapto hard carbon prepared in step T1, 4-7 parts of sodium methoxide, 1-5 parts of 4-propenylthiosemicarbazide, 0.05-0.5 parts of aluminum acrylate, 3-6 parts of sodium tert-butoxide, 1000-1400 parts of ethanol, and 60-70℃ for 50-90 min, removing the ethanol to obtain a modified hard carbon negative electrode material; (3) washing and drying the modified material in step (2) to obtain the hard carbon negative electrode material.

2. The method of claim 1, wherein the biomass is modified by a process comprising: The biomass material is at least one of wood and bamboo.

3. The method for preparing hard carbon anode materials by biomass modification according to claim 1, characterized in that, In step (1), the pre-carbonization is performed at a temperature of 200-450℃ and a heating rate of 1-10℃ / min.

4. The method for preparing hard carbon anode materials by biomass modification according to claim 1, characterized in that, In step (2), the wet ball-milling is performed at a material:ball:anhydrous ethanol mass ratio of 1:1.2-2.5:0.7-1.5, a ball-milling time of 1-3 h, and a ball-milling rotation speed of 65-130 rpm.

5. The method for preparing hard carbon anode materials by biomass modification according to claim 1, characterized in that, In step (2), the high-temperature carbonization is performed at a temperature of 1100-1600℃ for 2-6 h; The high-temperature carbonization is performed by first increasing the temperature and then decreasing the temperature, the temperature increasing rate is 0.5-5℃ / min, and the temperature decreasing rate is 2-8℃ / min.

6. The method of claim 1, wherein the biomass is modified by a process comprising: In step (2), the inert gas is at least one of nitrogen, argon, or helium, The flow rate of the inert gas is 10-50 ml / min.

7. The method for preparing hard carbon anode materials by biomass modification according to claim 1, characterized in that, In step (3), the material is repeatedly washed with an acid solution and deionized water, The acid solution is selected from one of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid, and the concentration of the acid solution is 0.5-5 M.

8. A sodium-ion battery hard carbon anode material, characterized in that, The method is prepared by any one of claims 1-7.

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