Preparation method of a novel biomass porous graphene potassium ion battery negative electrode material

Abstract

The present invention relates to a method for preparing a novel biomass porous graphene potassium ion battery negative electrode material, and belongs to the technical field of potassium ion battery preparation. Inspired by the unique flaky structure and chemical composition of cell membranes and cell walls, the present invention designs highly twisted porous graphene as a high-efficiency negative electrode material for potassium ion batteries. It is characterized in that cheap and easily available white radish is used as the main raw material, and firstly, biomass graphite material is obtained after soaking, carbonization and vacuum hot pressing sintering, and then a biomass porous graphene negative electrode material (WHBG) is prepared by a modified Hummers method. The porous graphene potassium ion battery negative electrode material prepared by this method has excellent electrochemical properties, good conductivity and good cycle stability. The raw materials required for the present invention are easy to obtain, and the materials prepared by this process can solve the problems of poor structural stability and K + The problem of low diffusion rate.

Description

Technical Field

[0001] The invention relates to a method for preparing a novel biomass porous graphene potassium ion battery negative electrode material, belonging to the technical field of potassium ion battery preparation. Background Art

[0002] The excessive exploitation and use of fossil fuels such as coal, oil, and natural gas has led to unprecedented pollution of the living environment. The mining process causes geological damage and pollution, while its use also leads to a series of environmental problems such as the greenhouse effect, air pollution, and water contamination. Therefore, the exploration and development of green energy sources has become an inevitable trend in the development of a green society. In recent years, lithium-ion batteries have been widely used in energy storage systems for various scenarios, and demand for them is increasing. However, lithium ore reserves are limited, and the mining process also causes environmental pollution. Therefore, the search for new energy storage systems that are abundant, affordable, and have excellent performance is urgent.

[0003] For potassium ion battery negative electrode materials, carbonaceous materials have the advantages of environmental protection, low cost and wide availability. However, the commonly used graphite negative electrode has a slow K + Kinetic and structural instability limit the performance of potassium ion batteries. As a member of carbon materials, the advantage of using biomass as a carbon source is that it can directly prepare nanostructured carbon negative electrode materials with pores, and exhibit excellent non-stoichiometric capacity and rate performance, while reducing material costs. However, biomass carbon-based negative electrodes also face similar challenges as traditional graphite materials. Due to K + The ions are large in size and their volume changes during charge and discharge are severe, which will lead to faster structural collapse and capacity decay of the electrode. In addition, the long and tortuous diffusion paths and small effective electrochemical active surface area lead to the + The diffusion rate is very low, which limits the reaction kinetics and rate performance, showing a low practical specific capacity.

[0004] Therefore, this patent addresses these issues and, inspired by the unique lamella structure and chemical composition of biomass cell membranes and cell skins, synthesizes a series of biomass carbon-based anode materials using white radish as a biomass precursor. Experiments have demonstrated that these anode materials exhibit excellent electrochemical properties, providing a new approach for designing high-efficiency carbon-based anode materials for practical applications in potassium-ion batteries. Summary of the Invention

[0005] The purpose of the present invention is to further apply the current new energy storage system and enhance the potassium storage performance of potassium ion carbon-based negative electrode materials. A new process for preparing biomass porous graphene (WHBG) using white radish as a biomass precursor, a heat treatment method and an improved Hummers method is proposed.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention is a method for preparing a biomass porous graphene potassium ion battery negative electrode material, comprising the following steps:

[0008] S1. Cutting the white radish into small cubes and then soaking them in deionized water for pretreatment to remove soluble impurities. The soaked white radish cubes are then placed in a drying oven for drying to ensure that the water in the biological cells can evaporate quickly and form a contracted structure.

[0009] S2, carbonizing the precursor obtained in step S1 and mixing it with Fe2O3, and then sintering it by vacuum hot pressing to obtain a biomass graphite material;

[0010] S3, mixing the biomass graphite obtained in step S2 with NaNO3, slowly adding concentrated H2SO4 and stirring, then placing the mixed solution in an ice bath and adding KMnO4, followed by heating in a water bath;

[0011] S4. Add a small amount of 30% H2O2 to the solution in step S3 to remove excess KMnO4. Finally, centrifuge, dry, and reduce the mixture to obtain WHBG.

[0012] Specifically, in step S1, the size of the white radish pieces is 2x2 cm-4x4 cm, the thickness is 1-2 cm, the soaking time in deionized water is 30-120 min, the drying temperature is 80°C-120°C, and the insulation time is 12-24 h;

[0013] Specifically, in step S2, the carbonization temperature is 400-600°C, the carbonization atmosphere is one of argon and nitrogen, and the heating rate is 2-5°C min -1 , holding time is 2-6h, Fe2O3 content is 0.1-10wt.%, hot pressing furnace pressure is 1-1.5MPa, hot pressing temperature is 2000-2400℃, and holding time is 1-2h;

[0014] Specifically, in step S3, the mass ratio of biomass graphite and NaNO3 is 0.5:1-1:1, the volume of concentrated H2SO4 is 30-60 mL, the stirring time is 1-2 h, the KMnO4 content is 2-4 g, the water bath temperature is 35-100 ° C, and the stirring time is 30-60 min;

[0015] Specifically, in step S4, the concentration of H2O2 is 30-70%, the centrifuge speed is 6000-10000 rpm, the drying temperature is 60-100°C, and the drying time is 12-24 hours.

[0016] The potassium ion battery preparation process further comprises the following steps:

[0017] (1) The prepared biomass porous graphene material, conductive carbon black and binder (PVDF) were mixed in a mass ratio of 6:2:2-8:1:1 and an appropriate amount of N-methylpyrrolidone (NMP) was added to form a slurry, which was then coated on a copper foil current collector. The electrode sheet was dried in a vacuum drying oven at 80-110°C for 12 hours and cut into 9-12 mm electrode sheets for use.

[0018] (2) CR2032 button cells were used to assemble the battery. The entire battery assembly process was completed in a glove box with a water and oxygen content of less than 0.01 ppm. Metal potassium was used as the positive electrode, the separator was Whatman GF / D glass fiber, the electrolyte was 0.8M KPF6 inDEC / EC, and the negative electrode was the above-mentioned electrode sheet. The assembly order was as follows: negative electrode shell, metal potassium foil, separator (fully wetted with electrolyte), electrode sheet, gasket, spring, and positive electrode shell. The button cell was allowed to rest before testing.

[0019] Compared with the prior art, the present invention provides a method for preparing a novel biomass porous graphene (WHBG) potassium ion battery negative electrode material, which has the following benefits:

[0020] 1. The porous graphene material prepared by the present invention has excellent rate performance and cycle stability; at 25mAg -1 The initial discharge capacity at the current density is 1464 mAh g -1 , then at 1A g -1 Ultra-long cycling was performed at a current density of 1.5, and the capacity retention rate was 93.5% compared with the 11th cycle, which can meet the needs of practical applications.

[0021] 2. The biomass porous graphene material prepared by this method is low-cost and easy to obtain, and the hot pressing sintering method can retain the honeycomb-like wrinkled morphology of the original white radish material, avoiding the accumulation of graphene, thereby obtaining high reversible capacity and stability.

[0022] 3. WHBG with wrinkles and pores has mechanical stability during charge and discharge due to its dual stress buffering effect. Nanopores promote K + diffusion. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below with reference to specific embodiments, but is not limited to the following implementation cases.

[0024] Example 1

[0025] (1) White radish was first cut into 2x2 cm cubes with a thickness of 2 cm, and then soaked in deionized water for 60 min to remove soluble impurities; the soaked white radish cubes were placed in a drying oven at 80°C for 12 h to quickly evaporate the water in the biological cells and form a contracted structure;

[0026] (2) The precursor obtained in step (1) was placed in a tube furnace with an Ar gas atmosphere and heated at 2 ° C min -1 The carbonized precursor was mixed with 0 wt.% Fe2O3 and then rapidly heated to 2200°C in a hot press furnace at 1.15 MPa and kept at this temperature for 1 hour to obtain a biomass graphite precursor.

[0027] (3) Take 0.6g of the biomass graphite precursor obtained in step (2) and mix it with 1.0g of NaNO3 and add it to a beaker. At the same time, slowly add 50mL of H2SO4 and stir for 1h. Place the mixed beaker in an ice bath and slowly add 3.0g of KMnO4 and stir for 2h. Then heat the water bath to 35℃, stir for 30min, and then slowly add 150mL of deionized water;

[0028] (4) Following step (3), the reaction system was heated to 98°C and poured into 200 mL of deionized water at 60°C while still hot. 5 mL of 30% H2O2 was added dropwise to remove excess KMnO4. The reaction mixture was centrifuged at 6000 rpm and the product was transferred to a forced air drying oven at 60°C for 24 h to dry and reduce to obtain WHBG.

[0029] The biomass porous graphene negative electrode material prepared in Example 1 was -1 The initial discharge capacity at the current density is 423 mAh g -1 , at 25mA g -1 After 150 cycles, it can still retain 178 mAh g -1 , then at 1A g -1 Ultra-long cycling was carried out at a current density of 100 nm. Compared with the 11th cycle, the capacity retention rate was 65.5%. The potassium ion battery assembled with the WHBG negative electrode material prepared in Example 1 has a stable cycle capacity and can meet application requirements.

[0030] Example 2

[0031] (1) White radish was first cut into 2x2 cm cubes with a thickness of 1 cm, and then soaked in deionized water for 60 min to remove soluble impurities; the soaked white radish cubes were placed in a drying oven at 80°C for 12 h to quickly evaporate the water in the biological cells and form a contracted structure;

[0032] (2) The precursor obtained in step (1) was placed in a tube furnace with an Ar gas atmosphere and heated at 2 ° C min -1 The carbonized precursor was mixed with 2 wt.% Fe2O3 and then rapidly heated to 2200°C in a hot press at 1.15 MPa and kept at this temperature for 1 hour to obtain a biomass graphite precursor.

[0033] (3) Take 0.6g of the biomass graphite precursor obtained in step (2) and mix it with 1.0g of NaNO3 and add it to a beaker. At the same time, slowly add 50mL of H2SO4 and stir for 1h. Place the mixed beaker in an ice bath and slowly add 3.0g of KMnO4 and stir for 2h. Then heat the water bath to 35℃, stir for 30min, and then slowly add 150mL of deionized water.

[0034] (4) Following step (3), the reaction system was heated to 98°C and poured into 200 mL of deionized water at 60°C while still hot. 5 mL of 30% H2O2 was added dropwise to remove excess KMnO4. The reaction mixture was centrifuged at 6000 rpm and the product was transferred to a forced air drying oven at 60°C for 24 h to dry and reduce to obtain WHBG.

[0035] The biomass porous graphene negative electrode material prepared in Example 2 was -1 The initial discharge capacity at the current density is 636 mAh g -1 , at 25mA g -1 After 150 cycles, it can still retain 241mAh g -1 , at 1A g -1 Ultra-long cycling was carried out at a current density of 100 nm. Compared with the 11th cycle, the capacity retention rate was 78.8%. The potassium ion battery assembled with the WHBG negative electrode material prepared in Example 2 has a stable cycle capacity and can meet application requirements.

[0036] Example 3

[0037] (1) White radish was first cut into 3x3 cm cubes with a thickness of 2 cm, and then soaked in deionized water for 60 min to remove soluble impurities; the soaked white radish cubes were placed in a drying oven at 80°C for 12 h to quickly evaporate the water in the biological cells and form a contracted structure;

[0038] (2) The precursor obtained in step (1) was placed in a tube furnace with an Ar gas atmosphere and heated at 2 ° C min -1 The carbonized precursor was mixed with 5 wt.% Fe2O3 and then rapidly heated to 2200°C in a hot press at 1.15 MPa and kept at this temperature for 1 hour to obtain a biomass graphite precursor.

[0039] (3) Take 0.6g of the biomass graphite precursor obtained in step (2) and mix it with 1.0g of NaNO3 and add it to a beaker. At the same time, slowly add 50mL of H2SO4 and stir for 1h. Place the mixed beaker in an ice bath and slowly add 3.0g of KMnO4 and stir for 2h. Then heat the water bath to 35℃, stir for 30min, and then slowly add 150mL of deionized water.

[0040] (4) Following step (3), the reaction system was heated to 98°C and poured into 200 mL of deionized water at 60°C while still hot. 5 mL of 30% H2O2 was added dropwise to remove excess KMnO4. The reaction mixture was centrifuged at 6000 rpm and the product was transferred to a forced air drying oven at 60°C for 24 h to dry and reduce to obtain WHBG.

[0041] The biomass porous graphene negative electrode material prepared in Example 3 was -1 The initial discharge capacity at the current density is 945 mAh g -1 , at 25mA g -1 After 150 cycles, it can still retain 356mAh g -1 , at 1A g -1 Ultra-long cycling was performed at a current density of 1.5, and the capacity retention rate was 83.9% compared with the 11th cycle. The potassium ion battery assembled with the WHBG negative electrode material prepared in Example 3 has a stable cycle capacity and can meet application requirements.

[0042] Example 4

[0043] (1) White radish was first cut into 2x2 cm cubes with a thickness of 2 cm, and then soaked in deionized water for 60 min to remove soluble impurities; the soaked white radish cubes were placed in a drying oven at 80°C for 12 h to quickly evaporate the water in the biological cells and form a contracted structure;

[0044] (2) The precursor obtained in step (1) was placed in a tube furnace with an Ar gas atmosphere and heated at 2 ° C min -1 The carbonized precursor was mixed with 8 wt.% Fe2O3 and then rapidly heated to 2200°C in a hot press furnace at 1.15 MPa and kept at this temperature for 1 hour to obtain a biomass graphite precursor.

[0045] (3) Take 0.6g of the biomass graphite precursor obtained in step (2) and mix it with 1.0g of NaNO3 and add it to a beaker. At the same time, slowly add 50mL of H2SO4 and stir for 1h. Place the mixed beaker in an ice bath and slowly add 3.0g of KMnO4 and stir for 2h. Then heat the water bath to 35℃, stir for 30min, and then slowly add 150mL of deionized water.

[0046] (4) Following step (3), the reaction system was heated to 98°C and poured into 200 mL of deionized water at 60°C while still hot. 5 mL of H2O2 was added dropwise to remove excess KMnO4. The reaction mixture was centrifuged at 6000 rpm and the product was transferred to a forced air drying oven at 60°C for 24 h for drying and reduction to obtain WHBG.

[0047] The biomass porous graphene negative electrode material prepared in Example 4 was -1 The initial discharge capacity at the current density is 1464 mAh g -1 , at 25mA g -1 After 150 cycles, it can still retain 410mAh g -1 , at 1A g -1 Ultra-long cycling was performed at a current density of 100 nm. Compared with the 11th cycle, the capacity retention rate was 93.5%. The potassium ion battery assembled with the WHBG negative electrode material prepared in Example 4 has a stable cycle capacity and can meet application requirements.

[0048] Example 5

[0049] (1) White radish was first cut into 4x4 cm cubes with a thickness of 1 cm, and then soaked in deionized water for 60 min to remove soluble impurities; the soaked white radish cubes were placed in a drying oven at 80°C for 12 h to quickly evaporate the water in the biological cells and form a contracted structure;

[0050] (2) The precursor obtained in step (1) was placed in a tube furnace with an Ar gas atmosphere and heated at 2 ° C min -1 The carbonized precursor was mixed with 10 wt.% Fe2O3 and then rapidly heated to 2200°C in a hot press furnace at 1.15 MPa and kept at this temperature for 1 hour to obtain a biomass graphite precursor.

[0051] (3) Take 0.6g of the biomass graphite precursor obtained in step (2) and mix it with 1.0g of NaNO3 and add it to a beaker. At the same time, slowly add 50mL of H2SO4 and stir for 1h. Place the mixed beaker in an ice bath and slowly add 3.0g of KMnO4 and stir for 2h. Then heat the water bath to 35℃, stir for 30min, and then slowly add 150mL of deionized water.

[0052] (4) Following step (3), the reaction system was heated to 98°C and poured into 200 mL of deionized water at 60°C while still hot. 5 mL of 30% H2O2 was added dropwise to remove excess KMnO4. The reaction mixture was centrifuged at 6000 rpm and the product was transferred to a forced air drying oven at 60°C for 24 h to dry and reduce to obtain WHBG.

[0053] The biomass porous graphene negative electrode material prepared in Example 5 was -1 The initial discharge capacity at the current density is 1167 mAh g -1 , at 25mA g -1 After 150 cycles, it can still retain 372mAh g -1 , at 1A g -1 Ultra-long cycling was performed at a current density of 100 nm. Compared with the 11th cycle, the capacity retention rate was 82.6%. The potassium ion battery assembled with the WHBG negative electrode material prepared in Example 5 has a stable cycle capacity and can meet application requirements.

[0054] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for preparing a novel biomass porous graphene potassium ion battery negative electrode material, characterized in that: The preparation method of the potassium ion battery negative electrode material comprises the following steps: S1. Cutting the white radish into small cubes and then soaking them in deionized water for pretreatment to remove soluble impurities. The soaked white radish cubes are then placed in a drying oven for drying to ensure that the water in the biological cells can evaporate quickly and form a contracted structure. S2, carbonizing the precursor obtained in step S1 and mixing it with Fe2O3, and then sintering it by vacuum hot pressing to obtain a biomass graphite material; S3, mixing the biomass graphite obtained in step S2 with NaNO3, slowly adding concentrated H2SO4 and stirring, then placing the mixed solution in an ice bath and adding KMnO4, followed by heating in a water bath; S4. Add a small amount of 30% H2O2 to the solution in step S3 to remove excess KMnO4. Finally, centrifuge, dry, and reduce the mixture to obtain a biomass porous graphene material.

2. The method for preparing a novel biomass porous graphene potassium ion battery negative electrode material according to claim 1, wherein: The size of the white radish pieces is 2x2 cm-4x4 cm, the thickness is 1-2 cm, the soaking time in deionized water is 30-120 minutes, the drying temperature is 80°C-120°C, and the insulation time is 12-24 hours.

3. The method for preparing a novel biomass porous graphene potassium ion battery negative electrode material according to claim 1, wherein: In step S2, the carbonization temperature is 400-600°C, the carbonization atmosphere is one of argon and nitrogen, and the heating rate is 2-5°C min -1 , the holding time is 2-6h, the Fe2O3 content is 0.1-10wt.%, the hot pressing furnace pressure is 1-1.5MPa, the hot pressing temperature is 2000-2400℃, and the holding time is 1-2h.

4. The method for preparing a novel biomass porous graphene potassium ion battery negative electrode material according to claim 1, wherein: In step S3, the mass ratio of biomass graphite and NaNO3 is 0.5:1-1:1, the volume of concentrated H2SO4 is 30-60 mL, the stirring time is 1-2 h, the KMnO4 content is 2-4 g, the water bath temperature is 35-100°C, and the stirring time is 30-60 min.

5. The method for preparing a novel biomass porous graphene potassium ion battery negative electrode material according to claim 1, wherein: In step S4, the concentration of H2O2 is 30-70%, the centrifuge speed is 6000-10000 rpm, the drying temperature is 60-100°C, and the drying time is 12-24 hours.