Preparation process of high-specific-energy strong-conductivity graphite composite negative electrode material
By preparing a germanium-carbon three-dimensional framework nanocomposite anode material P-Ge@Graphene@PEDOT, combined with porous germanium nanoparticles, graphene, and PEDOT:PSS, the volume expansion problem of germanium materials during electrode cycling was solved, achieving high coulombic efficiency and improved cycling performance.
Patent Information
- Application Number
- CN202511325283.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-17
- Publication Date
- 2025-12-12
AI Technical Summary
Germanium (Ge) expands in volume to about 300% during alloying/dealloying, leading to particle breakage and pulverization, resulting in capacity loss and cycle performance degradation. Existing technologies struggle to effectively combine nano-processing with buffer framework structures to improve this problem.
A nanocomposite anode material, P-Ge@Graphene@PEDOT, with a germanium-carbon three-dimensional framework was prepared by combining porous germanium nanoparticles, graphene, and the conductive polymer PEDOT:PSS to form a stable conductive framework. The process was optimized to alleviate volume expansion and improve electrochemical performance.
It achieves superior coulombic efficiency, cycle performance, and conductivity, enhancing the application potential of lithium-ion batteries and solving the problem of volume expansion of germanium materials during electrode cycling.
Smart Images
Figure CN121123229A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a preparation of a new material, in particular to a preparation process of a high specific energy strong conductive graphite composite negative electrode material. BACKGROUND
[0002] High specific capacity silicon (Si), germanium (Ge) and the like gradually become hot spots in the field of battery negative electrode materials, the theoretical specific capacity of Ge reaches 1600 mAh.g-1, which is 4 times that of Si. -1 At the same time, Ge has the advantages of high intrinsic conductivity (> 100 times that of Si) and fast ion diffusion rate (> 400 times that of Si), and is widely studied; however, Ge will expand to about 300% in the alloying / deloy alloying process, and may further cause the crushing and pulverization of particles, so as to be peeled off on the current collector; the poor microstructure cycle stability will cause capacity loss and cycle performance decay; the common means to solve the above problems are nano-treatment of Ge active material or construction of a buffer skeleton, but how to reasonably combine the two methods to fully play the synergistic effect is the key to solving the problem.
[0003] In order to effectively solve the above problems of germanium (Ge) material, the application prepares a nano composite negative electrode material of germanium carbon three-dimensional skeleton: a germanium carbon composite negative electrode material P-Ge@Graphene@PEDOT composite material of graphene bridging polythiophene coated germanium particles, the size of germanium particles is reduced to nanoscale, at the same time, the composite structure is designed and the process is optimized, the synergistic effect is played, and the volume expansion problem of Ge-based negative electrode in the electrode cycle process is improved. The P-Ge@Graphene@PEDOT composite negative electrode material prepared by the application has the following advantages: (1) excellent coulombic efficiency, (2) excellent cycle performance and rate performance, (3) good conductivity and the like, and compared with ordinary negative electrode materials in the current market, the application selects graphene, conductive polymer PEDOT:PSS and nano germanium particles to composite to construct a three-dimensional conductive skeleton, utilizes the excellent properties of graphene and the advantages of PEDOT:PSS, and improves the volume change of germanium material caused by the embedding and stripping of lithium in the electrochemical process. Therefore, the P-Ge@Graphene@PEDOT composite negative electrode material prepared by the application has a wide application prospect in lithium ion batteries. SUMMARY
[0004] To address the above problems, this invention provides a preparation process for a high-energy-density, high-conductivity graphite composite negative electrode material, comprising the following steps: step (1) preparation of porous germanium nanoparticles, step (2) preparation of artificial graphene, step (3) preparation of graphene oxide / carbon nanotube dispersion, step (4) preparation of P-Ge@Graphene material, step (5) preparation of PEDOT:PSS aqueous dispersion, and step (6) preparation of P-Ge@Graphene@PEDOT composite material.
[0005] Preferably, step (1) involves the preparation of porous germanium nanoparticles. Magnesium powder, germanium dioxide, zinc chloride and aluminum trichloride were mixed and added to a tube furnace. Magnesium reduction reaction was carried out under certain conditions. After the reaction was completed, the mixture was naturally cooled to room temperature. The resulting material was washed with hydrochloric acid, distilled water and ethanol to remove impurities. Then it was dried under certain vacuum conditions for a period of time to obtain porous germanium nanoparticles. Step (2) Preparation of artificial graphene A certain amount of graphite powder, sodium sulfate and N,N-dimethylformamide (DMF) are mixed evenly, ultrasonically exfoliated and dispersed, and the resulting suspension is centrifuged and cooled to remove the thick layer of graphite, thus obtaining graphene. Step (3) Preparation of graphene oxide / carbon nanotube dispersion The artificial graphene prepared in step (2) was dispersed in deionized water and ultrasonically dispersed; then it was mixed with wet single-arm carbon nanotubes (SWCNTs) and ultrasonically dispersed to obtain graphene oxide / carbon nanotubes (GO / SWCNTs) dispersion. Preferably, step (4) involves the preparation of P-Ge@Graphene materials. The graphene oxide / carbon nanotube (GO / SWCNT) dispersion obtained in step (3) was dispersed in deionized water by ultrasound. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution. After stirring until the solution was clear, it was mixed with the graphene solution dispersed by ultrasound and ultrasound was performed again. Then the pH was adjusted with HCl solution. The solution was then placed in a water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH4) was dissolved in ice water to prepare sodium borohydride (NaBH4) aqueous solution. The sodium borohydride (NaBH4) aqueous solution was slowly added to the above solution while stirring. After stirring, the solution was filtered. The filtered product was placed in a vacuum drying oven for vacuum drying. Then it was placed in a tube sintering furnace. Under an argon-hydrogen atmosphere, the temperature was increased and sintered at a constant temperature for a period of time to obtain P-Ge@Graphene composite material. Step (5) Preparation of PEDOT:PSS aqueous dispersion Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) is dissolved in a certain amount of deionized water, and 3,4-ethylenedioxythiophene (EDOT) is added dropwise. The mixture is stirred slowly, and hydrochloric acid is added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin is slowly added dropwise, and the reaction is stirred rapidly. Inorganic salt ions are exchanged with anion and cation exchange resins for a period of time to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). Step (6) Preparation of P-Ge@Graphene@PEDOT composite material The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed to obtain a P-Ge@Graphene@PEDOT solution. Then it was stirred to evaporate the water and the water was removed under vacuum drying conditions to obtain the P-Ge@Graphene@PEDOT composite material.
[0006] Preferably, step (1) involves the preparation of porous germanium nanoparticles. Magnesium powder, germanium dioxide, zinc chloride, and aluminum trichloride were mixed and added to a tube furnace. A magnesium thermoelectric reduction reaction was carried out at 600-650℃ for 3-6 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The resulting material was washed with hydrochloric acid, distilled water, and ethanol to remove impurities. Then, it was dried under vacuum at 50-55℃ for 10-12 hours to obtain porous germanium nanoparticles.
[0007] The advantages of this invention are that this step achieves efficient and controllable preparation of porous germanium nanoparticles through low-temperature molten salt magnesium thermal reduction, which has the advantages of simple process, optimized structure and improved performance. Furthermore, the magnesium oxide byproduct generated by the magnesium thermal reduction reaction is removed during the acid washing process, naturally forming a porous structure of germanium particles. The porous structure increases the specific surface area of the material, provides more active sites, and is beneficial to electrolyte penetration and lithium ion diffusion.
[0008] Preferably, step (2) involves the preparation of artificial graphene. 2.5-3g of expandable graphite powder is packaged in a polyester bag. A platinum electrode acts as a conductive current collector in the middle of the graphite powder. The top of the polyester bag is sealed with a clip to prevent the graphite powder from detaching from the graphite electrode during electrochemical exfoliation. The pressure of the graphite powder is set by adjusting the nut. A titanium sheet is used as the cathode and placed in parallel. The distance between the cathode electrode and the graphite electrode is 2-2.5cm. The voltage is 10-12V and the reaction time is 4-5h. After the reaction is completed, the exfoliated product is washed several times with water and ethanol by vacuum filtration. After washing, sodium sulfate and N,N-dimethylformamide (DMF) are added and mixed evenly. Then, ultrasonic exfoliation and dispersion are performed. The resulting suspension is then centrifuged and cooled to remove the thick layer of graphite, thus obtaining graphene.
[0009] The advantages of this invention are that it uses an electrochemical exfoliation method to prepare artificial graphene, using graphite as the anode (or cathode). Under the action of an external electric field, ions are driven to intercalate, resulting in an increase in the interlayer spacing of the graphite. Graphene is then obtained through subsequent ultrasonic and cold-drying processes. This method is green and environmentally friendly, simple to operate, and the thickness, size, and defect density of the graphene sheets can be controlled by changing the exfoliation conditions.
[0010] Preferably, step (3) involves the preparation of the graphene oxide / carbon nanotube dispersion. The artificial graphene prepared in step (2) was dispersed in deionized water and ultrasonically dispersed; then it was mixed with wet single-arm carbon nanotubes (SWCNTs) and ultrasonically dispersed to obtain graphene oxide / carbon nanotubes (GO / SWCNTs) dispersion.
[0011] The advantage of using this invention is that this step achieves a balance between dispersibility, conductivity and interfacial bonding through the synergistic effect of GO and wet single-arm carbon nanotubes (SWCNTs), providing a good foundation for the subsequent preparation of composite materials.
[0012] Preferably, step (4) involves the preparation of P-Ge@Graphene materials. The graphene oxide / carbon nanotube (GO / SWCNT) dispersion obtained in step (3) was ultrasonically dispersed in deionized water for 3-4 hours. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution and stirred until the solution was clear. Then, it was mixed with the ultrasonically dispersed graphene solution and ultrasonically dispersed again for 1-2 hours. The pH was then adjusted to 7-7.5 with HCl solution. The solution was then placed in a 60-65℃ water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH4) was dissolved in ice water to prepare borohydride solution. Sodium borohydride (NaBH4) aqueous solution was slowly added to the above solution while stirring. After stirring for 3-4 hours, the mixture was filtered. The filtered product was placed in a vacuum drying oven at 60-65℃ and dried for 12-14 hours. Then, it was placed in a tube sintering furnace and sintered at a constant temperature of 700-750℃ (heating rate of 5-6℃ / min) under an argon-hydrogen atmosphere of 10-11%. The mass ratio of graphene to germanium nanoparticles was 1:20-3:200 to obtain P-Ge@Graphene composite material.
[0013] The advantages of using this invention are that the use of porous germanium nanoparticles in this step increases the active sites and electrolyte contact area, thereby improving electrochemical performance. Furthermore, the combination of porous germanium and graphene can alleviate the problem of volume expansion and improve rate performance. At the same time, the gradient sintering process under an argon-hydrogen atmosphere can promote the interfacial bonding between germanium and graphene, forming a stable conductive framework, and can also prevent excessive oxidation of germanium particles.
[0014] Preferably, step (5) involves the preparation of the PEDOT:PSS aqueous dispersion. Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) is dissolved in deionized water, and 3,4-ethylenedioxythiophene (EDOT) is added dropwise. The mixture is stirred slowly, and hydrochloric acid is added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin is slowly added dropwise, and the mixture is stirred rapidly for 24-25 hours. Inorganic salt ions are exchanged with anion and cation exchange resins for 4-5 hours respectively to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS).
[0015] The advantages of this invention are that this step combines the removal of inorganic salts with cation and anion exchange resins, reduces the interference of ionic impurities on the conductive network, and improves product purity. Through the dual-functional design of polystyrene sulfonic acid (PSS) and the synergistic regulation of pH and ion exchange, high purity, high conductivity, and process controllability of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) aqueous dispersion are achieved. Furthermore, the product can optimize the electrochemical performance of the electrode, providing key technical support for the subsequent preparation of anode materials.
[0016] Preferably, step (6) involves the preparation of the P-Ge@Graphene@PEDOT composite material. The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed for 1-1.5 h. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed for 1-2 h to obtain a P-Ge@Graphene@PEDOT solution. The water was then evaporated by stirring at 60-65 °C. Vacuum drying was set at 60-70 °C for 12-14 h to remove water and obtain the P-Ge@Graphene@PEDOT composite material.
[0017] The advantage of this invention is that it employs a two-step method of "ultrasonic dispersion followed by solution blending". First, P-Ge@Graphene is uniformly dispersed in deionized water, and then PEDOT:PSS aqueous dispersion is added sequentially. This avoids agglomeration caused by polarity differences and achieves gradient wetting of porous germanium nanoparticles, graphene and poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS), forming a "core-shell-network" composite structure.
[0018] In summary, the present invention has the following beneficial effects: 1. The advantages of using this invention are that this step achieves efficient and controllable preparation of porous germanium nanoparticles through low-temperature molten salt magnesium thermal reduction, which has the advantages of simple process, optimized structure and improved performance. Furthermore, the magnesium oxide byproduct generated by the magnesium thermal reduction reaction is removed during the acid washing process, naturally forming a porous structure of germanium particles. The porous structure increases the specific surface area of the material, provides more active sites, and is beneficial to electrolyte penetration and lithium ion diffusion. 2. The advantage of this invention lies in the fact that this step uses an electrochemical exfoliation method to prepare artificial graphene. This method refers to using graphite as the anode (or cathode), driving ions to intercalate under the action of an external electric field, thereby increasing the interlayer spacing of the graphite, and obtaining graphene through subsequent ultrasonic and cold-drying processes. This method is green and environmentally friendly, simple to operate, and the thickness, size, and defect density of the graphene sheets can be controlled by changing the exfoliation condition parameters. 3. The advantage of using this invention is that this step achieves a balance between dispersibility, conductivity and interfacial bonding through the synergistic effect of GO and wet single-arm carbon nanotubes (SWCNTs), providing a good foundation for the subsequent preparation of composite materials; 4. The advantages of using this invention are that the porous germanium nanoparticles used in this step increase the active sites and electrolyte contact area, improve electrochemical performance, and the combination of porous germanium and graphene can alleviate the problem of volume expansion and improve rate performance. At the same time, the gradient sintering process under argon-hydrogen atmosphere can promote the interfacial bonding between germanium and graphene, form a stable conductive framework, and avoid excessive oxidation of germanium particles. 5. The advantages of using this invention are that this step combines the removal of inorganic salts with cation and anion exchange resins, reduces the interference of ionic impurities on the conductive network, and improves product purity. Through the dual-functional design of polystyrene sulfonic acid (PSS) and the synergistic regulation of pH and ion exchange, high purity, high conductivity, and process controllability of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) aqueous dispersion are achieved. Furthermore, the product can optimize the electrochemical performance of the electrode, providing key technical support for the subsequent preparation of anode materials. 6. The advantage of this invention is that it employs a two-step method of "ultrasonic dispersion followed by solution blending". First, P-Ge@Graphene is uniformly dispersed in deionized water, and then poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) aqueous dispersion is added sequentially. This avoids agglomeration caused by polarity differences and achieves gradient wetting of porous germanium nanoparticles, graphene and poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS), forming a "core-shell-network" composite structure. Attached Figure Description
[0019] Figure 1 A process flow diagram for the preparation of a high-energy-density, high-conductivity graphite composite anode material. Detailed Implementation
[0020] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention.
[0021] Unless otherwise specified, the techniques used in the embodiments are conventional techniques well known to those skilled in the art. Furthermore, all component raw materials used in the embodiments are known commercially available products.
[0022] Example 1
[0023] Step (1) Preparation of porous germanium nanoparticles Magnesium powder, germanium dioxide, zinc chloride and aluminum trichloride were mixed and added to a tube furnace. Magnesium reduction reaction was carried out at 600℃ for 3 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The obtained material was washed with hydrochloric acid, distilled water and ethanol to remove impurities. Then it was dried under vacuum at 50℃ for 10 hours to obtain porous germanium nanoparticles. Step (2) Preparation of artificial graphene 2.5g of expandable graphite powder was packaged in a polyester bag. A platinum electrode was placed in the middle of the graphite powder to act as a conductive current collector. The top of the polyester bag was sealed with a clip to prevent the graphite powder from detaching from the graphite electrode during the electrochemical exfoliation process. The pressure of the graphite powder was set by adjusting the nut. A titanium sheet was used as the cathode and placed in parallel. The distance between the cathode electrode and the graphite electrode was 2cm. The voltage was 10V and the reaction time was 4h. After the reaction was completed, the exfoliated product was washed with water and ethanol by vacuum filtration. After washing, sodium sulfate and N,N-dimethylformamide (DMF) were added and mixed evenly. The mixture was then subjected to ultrasonic exfoliation and dispersion. The resulting suspension was then centrifuged and cooled to remove the thick layer of graphite, thus obtaining graphene. Step (3) Preparation of graphene oxide / carbon nanotube dispersion The artificial graphene prepared in step (2) was dispersed in deionized water and ultrasonically dispersed; then it was mixed with wet single-arm carbon nanotubes (SWCNTs) and ultrasonically dispersed to obtain graphene oxide / carbon nanotubes (GO / SWCNTs) dispersion. Step (4) Preparation of P-Ge@Graphene material The graphene oxide / carbon nanotube (GO / SWCNT) dispersion obtained in step (3) was ultrasonically dispersed in deionized water for 3 hours. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution. After stirring until the solution was clear, it was mixed with the ultrasonically dispersed graphene solution and ultrasonically dispersed again for 1 hour. Then, the pH was adjusted to 7 with HCl solution. The solution was then placed in a 60°C water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH2O) was dissolved in ice water. 4) Prepare an aqueous solution of sodium borohydride (NaBH4). Slowly add the aqueous solution of sodium borohydride (NaBH4) to the above solution while stirring. After stirring for 3 hours, filter the solution. Place the filtered product in a vacuum drying oven at 60°C for 12 hours. Then place it in a tube sintering furnace and heat the temperature to 700°C (heating rate of 5°C / min) under a 10% argon-hydrogen atmosphere. Sinter at a constant temperature for 5 hours. The mass ratio of graphene to germanium nanoparticles is 1:25 to obtain the P-Ge@Graphene composite material. Step (5) Preparation of PEDOT:PSS aqueous dispersion Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) was dissolved in deionized water, and 3,4-ethylenedioxythiophene (EDOT) was added dropwise. The mixture was stirred slowly, and hydrochloric acid was added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin was slowly added dropwise, and the mixture was stirred rapidly for 24 hours. Inorganic salt ions were exchanged with anion and cation exchange resins for 4 hours respectively to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). Step (6) Preparation of P-Ge@Graphene@PEDOT composite material The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed for 1 h. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed for 1 h to obtain a P-Ge@Graphene@PEDOT solution. Then the water was evaporated by stirring at 60 °C. Vacuum drying was set at 60 °C for 12 h to remove water and obtain the P-Ge@Graphene@PEDOT composite material.
[0024] Example 2
[0025] Step (1) Preparation of porous germanium nanoparticles Magnesium powder, germanium dioxide, zinc chloride and aluminum trichloride were mixed and added to a tube furnace. Magnesium reduction reaction was carried out at 600℃ for 3 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The obtained material was washed with hydrochloric acid, distilled water and ethanol to remove impurities. Then it was dried under vacuum at 50℃ for 10 hours to obtain porous germanium nanoparticles. Step (2) Preparation of artificial graphene 2.5g of expandable graphite powder was packaged in a polyester bag. A platinum electrode was placed in the middle of the graphite powder to act as a conductive current collector. The top of the polyester bag was sealed with a clip to prevent the graphite powder from detaching from the graphite electrode during the electrochemical exfoliation process. The pressure of the graphite powder was set by adjusting the nut. A titanium sheet was used as the cathode and placed in parallel. The distance between the cathode electrode and the graphite electrode was 2cm. The voltage was 10V and the reaction time was 4h. After the reaction was completed, the exfoliated product was washed with water and ethanol by vacuum filtration. After washing, sodium sulfate and N,N-dimethylformamide (DMF) were added and mixed evenly. The mixture was then subjected to ultrasonic exfoliation and dispersion. The resulting suspension was then centrifuged and cooled to remove the thick layer of graphite, thus obtaining graphene. Step (3) Preparation of graphene oxide / carbon nanotube dispersion The artificial graphene prepared in step (2) was dispersed in deionized water and ultrasonically dispersed; then it was mixed with wet single-arm carbon nanotubes (SWCNTs) and ultrasonically dispersed to obtain graphene oxide / carbon nanotubes (GO / SWCNTs) dispersion. Step (4) Preparation of P-Ge@Graphene material The graphene oxide / carbon nanotube (GO / SWCNT) dispersion obtained in step (3) was ultrasonically dispersed in deionized water for 3 hours. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution. After stirring until the solution was clear, it was mixed with the ultrasonically dispersed graphene solution and ultrasonically dispersed again for 1 hour. Then, the pH was adjusted to 7 with HCl solution. The solution was then placed in a 60°C water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH2O) was dissolved in ice water. 4) Prepare an aqueous solution of sodium borohydride (NaBH4). Slowly add the aqueous solution of sodium borohydride (NaBH4) to the above solution while stirring. After stirring for 3 hours, filter the solution. Place the filtered product in a vacuum drying oven at 60°C for 12 hours. Then place it in a tube sintering furnace and heat it to 700°C (heating rate of 5°C / min) under a 10% argon-hydrogen atmosphere. Sinter at a constant temperature for 5 hours. The mass ratio of graphene to germanium nanoparticles is 3:100 to obtain the P-Ge@Graphene composite material. Step (5) Preparation of PEDOT:PSS aqueous dispersion Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) was dissolved in deionized water, and 3,4-ethylenedioxythiophene (EDOT) was added dropwise. The mixture was stirred slowly, and hydrochloric acid was added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin was slowly added dropwise, and the mixture was stirred rapidly for 24 hours. Inorganic salt ions were exchanged with anion and cation exchange resins for 4 hours respectively to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). Step (6) Preparation of P-Ge@Graphene@PEDOT composite material The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed for 1 h. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed for 1 h to obtain a P-Ge@Graphene@PEDOT solution. Then the water was evaporated by stirring at 60 °C. Vacuum drying was set at 60 °C for 12 h to remove water and obtain the P-Ge@Graphene@PEDOT composite material.
[0026] Example 3
[0027] Step (1) Preparation of porous germanium nanoparticles Magnesium powder, germanium dioxide, zinc chloride and aluminum trichloride were mixed and added to a tube furnace. Magnesium reduction reaction was carried out at 600℃ for 3 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The obtained material was washed with hydrochloric acid, distilled water and ethanol to remove impurities. Then it was dried under vacuum at 50℃ for 10 hours to obtain porous germanium nanoparticles. Step (2) Preparation of artificial graphene 2.5g of expandable graphite powder was packaged in a polyester bag. A platinum electrode was placed in the middle of the graphite powder to act as a conductive current collector. The top of the polyester bag was sealed with a clip to prevent the graphite powder from detaching from the graphite electrode during the electrochemical exfoliation process. The pressure of the graphite powder was set by adjusting the nut. A titanium sheet was used as the cathode and placed in parallel. The distance between the cathode electrode and the graphite electrode was 2cm. The voltage was 10V and the reaction time was 4h. After the reaction was completed, the exfoliated product was washed with water and ethanol by vacuum filtration. After washing, sodium sulfate and N,N-dimethylformamide (DMF) were added and mixed evenly. The mixture was then subjected to ultrasonic exfoliation and dispersion. The resulting suspension was then centrifuged and cooled to remove the thick layer of graphite, thus obtaining graphene. Step (3) Preparation of graphene oxide / carbon nanotube dispersion The artificial graphene prepared in step (2) was dispersed in deionized water and ultrasonically dispersed; then it was mixed with wet single-arm carbon nanotubes (SWCNTs) and ultrasonically dispersed to obtain graphene oxide / carbon nanotubes (GO / SWCNTs) dispersion. Step (4) Preparation of P-Ge@Graphene material The graphene oxide / carbon nanotube (GO / SWCNT) dispersion obtained in step (3) was ultrasonically dispersed in deionized water for 3 hours. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution. After stirring until the solution was clear, it was mixed with the ultrasonically dispersed graphene solution and ultrasonically dispersed again for 1 hour. Then, the pH was adjusted to 7 with HCl solution. The solution was then placed in a 60°C water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH2O) was dissolved in ice water. 4) Prepare an aqueous solution of sodium borohydride (NaBH4). Slowly add the aqueous solution of sodium borohydride (NaBH4) to the above solution while stirring. After stirring for 3 hours, filter the solution. Place the filtered product in a vacuum drying oven at 60°C for 12 hours. Then place it in a tube sintering furnace and heat it to 700°C (heating rate of 5°C / min) under a 10% argon-hydrogen atmosphere. Sinter at a constant temperature for 5 hours. The mass ratio of graphene to germanium nanoparticles is 1:200 to obtain the P-Ge@Graphene composite material. Step (5) Preparation of PEDOT:PSS aqueous dispersion Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) was dissolved in deionized water, and 3,4-ethylenedioxythiophene (EDOT) was added dropwise. The mixture was stirred slowly, and hydrochloric acid was added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin was slowly added dropwise, and the mixture was stirred rapidly for 24 hours. Inorganic salt ions were exchanged with anion and cation exchange resins for 4 hours respectively to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). Step (6) Preparation of P-Ge@Graphene@PEDOT composite material The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed for 1 h. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed for 1 h to obtain a P-Ge@Graphene@PEDOT solution. Then the water was evaporated by stirring at 60 °C. Vacuum drying was set at 60 °C for 12 h to remove water and obtain the P-Ge@Graphene@PEDOT composite material.
[0028] Example 4
[0029] Step (1) Preparation of porous germanium nanoparticles Magnesium powder, germanium dioxide, zinc chloride and aluminum trichloride were mixed and added to a tube furnace. Magnesium reduction reaction was carried out at 600℃ for 3 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The obtained material was washed with hydrochloric acid, distilled water and ethanol to remove impurities. Then it was dried under vacuum at 50℃ for 10 hours to obtain porous germanium nanoparticles. Step (2) Preparation of artificial graphene 2.5g of expandable graphite powder was packaged in a polyester bag. A platinum electrode was placed in the middle of the graphite powder to act as a conductive current collector. The top of the polyester bag was sealed with a clip to prevent the graphite powder from detaching from the graphite electrode during the electrochemical exfoliation process. The pressure of the graphite powder was set by adjusting the nut. A titanium sheet was used as the cathode and placed in parallel. The distance between the cathode electrode and the graphite electrode was 2cm. The voltage was 10V and the reaction time was 4h. After the reaction was completed, the exfoliated product was washed with water and ethanol by vacuum filtration. After washing, sodium sulfate and N,N-dimethylformamide (DMF) were added and mixed evenly. The mixture was then subjected to ultrasonic exfoliation and dispersion. The resulting suspension was then centrifuged and cooled to remove the thick layer of graphite, thus obtaining graphene. Step (3) Preparation of graphene oxide / carbon nanotube dispersion The artificial graphene prepared in step (2) was dispersed in deionized water and ultrasonically dispersed; then it was mixed with wet single-arm carbon nanotubes (SWCNTs) and ultrasonically dispersed to obtain graphene oxide / carbon nanotubes (GO / SWCNTs) dispersion. Step (4) Preparation of P-Ge@Graphene material The graphene oxide / carbon nanotube (GO / SWCNT) dispersion obtained in step (3) was ultrasonically dispersed in deionized water for 3 hours. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution. After stirring until the solution was clear, it was mixed with the ultrasonically dispersed graphene solution and ultrasonically dispersed again for 1 hour. Then, the pH was adjusted to 7 with HCl solution. The solution was then placed in a 60°C water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH2O) was dissolved in ice water. 4) Prepare an aqueous solution of sodium borohydride (NaBH4). Slowly add the aqueous solution of sodium borohydride (NaBH4) to the above solution while stirring. After stirring for 3 hours, filter the solution. Place the filtered product in a vacuum drying oven at 60°C for 12 hours. Then place it in a tube sintering furnace and heat it to 700°C (heating rate of 5°C / min) under a 10% argon-hydrogen atmosphere. Sinter at a constant temperature for 5 hours. The mass ratio of graphene to germanium nanoparticles is 1:50 to obtain the P-Ge@Graphene composite material. Step (5) Preparation of PEDOT:PSS aqueous dispersion Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) was dissolved in deionized water, and 3,4-ethylenedioxythiophene (EDOT) was added dropwise. The mixture was stirred slowly, and hydrochloric acid was added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin was slowly added dropwise, and the mixture was stirred rapidly for 24 hours. Inorganic salt ions were exchanged with anion and cation exchange resins for 4 hours respectively to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). Step (6) Preparation of P-Ge@Graphene@PEDOT composite material The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed for 1 h. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed for 1 h to obtain a P-Ge@Graphene@PEDOT solution. Then the water was evaporated by stirring at 60 °C. Vacuum drying was set at 60 °C for 12 h to remove water and obtain the P-Ge@Graphene@PEDOT composite material.
[0030] Comparative Example 1
[0031] Step (1) Preparation of porous germanium nanoparticles Magnesium powder, germanium dioxide, zinc chloride and aluminum trichloride were mixed and added to a tube furnace. Magnesium reduction reaction was carried out at 600℃ for 3 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The obtained material was washed with hydrochloric acid, distilled water and ethanol to remove impurities. Then it was dried under vacuum at 50℃ for 10 hours to obtain porous germanium nanoparticles. Step (2) Preparation of graphene oxide / carbon nanotube dispersion Artificial graphene was dispersed in deionized water and then ultrasonically dispersed; subsequently, it was mixed with wet single-arm carbon nanotubes (SWCNTs) and ultrasonically dispersed to obtain a graphene oxide / carbon nanotube (GO / SWCNT) dispersion. Step (3) Preparation of P-Ge@Graphene material The graphene oxide / carbon nanotube (GO / SWCNT) dispersion obtained in step (2) was ultrasonically dispersed in deionized water for 3 hours. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution. After stirring until the solution was clear, it was mixed with the ultrasonically dispersed graphene solution and ultrasonically dispersed again for 1 hour. Then, the pH was adjusted to 7 with HCl solution. The solution was then placed in a 60°C water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH2O) was dissolved in ice water. 4) Prepare an aqueous solution of sodium borohydride (NaBH4). Slowly add the aqueous solution of sodium borohydride (NaBH4) to the above solution while stirring. After stirring for 3 hours, filter the solution. Place the filtered product in a vacuum drying oven at 60°C for 12 hours. Then place it in a tube sintering furnace and heat it to 700°C (heating rate of 5°C / min) under a 10% argon-hydrogen atmosphere. Sinter at a constant temperature for 5 hours. The mass ratio of graphene to germanium nanoparticles is 1:100 to obtain the P-Ge@Graphene composite material. Step (4) Preparation of PEDOT:PSS aqueous dispersion Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) was dissolved in deionized water, and 3,4-ethylenedioxythiophene (EDOT) was added dropwise. The mixture was stirred slowly, and hydrochloric acid was added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin was slowly added dropwise, and the mixture was stirred rapidly for 24 hours. Inorganic salt ions were exchanged with anion and cation exchange resins for 4 hours respectively to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). Step (5) Preparation of P-Ge@Graphene@PEDOT composite material The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed for 1 h. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed for 1 h to obtain a P-Ge@Graphene@PEDOT solution. Then the water was evaporated by stirring at 60 °C. Vacuum drying was set at 60 °C for 12 h to remove water and obtain the P-Ge@Graphene@PEDOT composite material.
[0032] Comparative Example 2
[0033] Step (1) Preparation of porous germanium nanoparticles Magnesium powder, germanium dioxide, zinc chloride and aluminum trichloride were mixed and added to a tube furnace. Magnesium reduction reaction was carried out at 600℃ for 3 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The obtained material was washed with hydrochloric acid, distilled water and ethanol to remove impurities. Then it was dried under vacuum at 50℃ for 10 hours to obtain porous germanium nanoparticles. Step (2) Preparation of artificial graphene 2.5g of expandable graphite powder was packaged in a polyester bag. A platinum electrode was placed in the middle of the graphite powder to act as a conductive current collector. The top of the polyester bag was sealed with a clip to prevent the graphite powder from detaching from the graphite electrode during the electrochemical exfoliation process. The pressure of the graphite powder was set by adjusting the nut. A titanium sheet was used as the cathode and placed in parallel. The distance between the cathode electrode and the graphite electrode was 2cm. The voltage was 10V and the reaction time was 4h. After the reaction was completed, the exfoliated product was washed with water and ethanol by vacuum filtration. After washing, sodium sulfate and N,N-dimethylformamide (DMF) were added and mixed evenly. The mixture was then subjected to ultrasonic exfoliation and dispersion. The resulting suspension was then centrifuged and cooled to remove the thick layer of graphite, thus obtaining graphene. Step (3) Preparation of P-Ge@Graphene material The graphene prepared in step (2) was dispersed in deionized water by ultrasound for 3 hours. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution. After stirring until the solution was clear, it was mixed with the graphene solution dispersed by ultrasound and ultrasound was performed again for 1 hour. Then, the pH was adjusted to 7 with HCl solution. The solution was then placed in a 60°C water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH4) was dissolved in ice water to prepare a sodium borohydride (NaBH4) aqueous solution. The sodium borohydride (NaBH4) aqueous solution was slowly added to the above solution while stirring. After stirring for 3 hours, the solution was filtered. The filtered product was placed in a vacuum drying oven at 60°C and dried for 12 hours. Then, it was placed in a tube sintering furnace and heated to 700°C (heating rate of 5°C / min) under a 10% argon-hydrogen atmosphere and sintered at a constant temperature for 5 hours. The mass ratio of graphene to germanium nanoparticles was 1:20, and P-Ge@Graphene composite material was obtained. Step (4) Preparation of PEDOT:PSS aqueous dispersion Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) was dissolved in deionized water, and 3,4-ethylenedioxythiophene (EDOT) was added dropwise. The mixture was stirred slowly, and hydrochloric acid was added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin was slowly added dropwise, and the mixture was stirred rapidly for 24 hours. Inorganic salt ions were exchanged with anion and cation exchange resins for 4 hours respectively to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). Step (5) Preparation of P-Ge@Graphene@PEDOT composite material The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed for 1 h. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed for 1 h to obtain a P-Ge@Graphene@PEDOT solution. Then the water was evaporated by stirring at 60 °C. Vacuum drying was set at 60 °C for 12 h to remove water and obtain the P-Ge@Graphene@PEDOT composite material.
[0034] Comparison of detection experiments:
[0035] The P-Ge@Graphene@PEDOT composite materials obtained in Examples 1 to 4, and comparative examples 1 and 2, were tested using the following specific testing methods: Cyclic voltammetry This method can be used to investigate the mechanism of lithium insertion / extraction potential, reaction ease, and reversibility in electrochemical reactions. In this invention, the cyclic voltammetry (CV) of the coin cell was performed on a Princeton Vera STAT instrument with a voltage of 0.01~1.5 V. The graphene content corresponds to the mass ratio of graphene to germanium nanoparticles in Examples 1-4 and Comparative Examples 1-2 of this invention. To make the data more intuitive, the ratio was converted into a percentage.
[0036] Constant current charge and discharge method For constant current charging and discharging, the charging and discharging voltage of the test sample should be set to 0.005~2V, the current value to 0.2C, and the number of cycles to 100, according to the different properties of the material. The voltage, plateau, and capacity data during the charging and discharging cycles of the sample should be recorded. The graphene content corresponds to the mass ratio of graphene to germanium nanoparticles in Examples 1-4 and Comparative Examples 1-2 of this invention. In order to make the data more intuitive, the ratio is converted into a percentage.
[0037] Table 1. Charge / discharge specific capacity test results
[0038] As shown in Table 1, Example 4 has the highest specific capacity, while Comparative Example 1 has a lower specific capacity. This indicates that the introduction of graphene can effectively suppress the volume expansion of germanium particles. The highest specific capacity is achieved when the mass ratio of graphene to germanium is 1:50, indicating that this ratio is the most suitable. Further increasing the graphene content will not have a significant impact on the specific capacity of the anode material; on the contrary, it will reduce its performance.
[0039] Table 2 Results of Cyclic Test
[0040] As shown in Table 2, Example 4 has the highest specific capacity retention rate, while Comparative Example 2 is relatively poor. After 100 cycles, the specific capacity retention rate of Example 4 is as high as 69%, indicating that a graphene content of 2% has the best effect on inhibiting the pulverization of germanium, the most stable electrochemical performance, and improves the cycle performance of germanium anode materials.
[0041] Table 3 Results of the first coulomb efficiency test
[0042] As shown in Table 3, Example 4 has the best coulombic efficiency, while Comparative Example 1 is worse. The introduction of graphene not only changes the volume expansion of germanium particles, but graphene itself also has good electrical conductivity, which improves the electrochemical performance of the anode material. This results in the final composite anode material having good stability and excellent electrical conductivity.
[0043] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.
Claims
1. A preparation process for a high-energy-density, high-conductivity graphite composite anode material, characterized in that, include: Step (1) Preparation of porous germanium nanoparticles, Step (2) Preparation of artificial graphene, Step (3) Preparation of graphene oxide / carbon nanotube dispersion, Step (4) Preparation of P-Ge@Graphene material, Step (5) Preparation of PEDOT:PSS aqueous dispersion, Step (6) Preparation of P-Ge@Graphene@PEDOT composite material.
2. The preparation process of a high-energy-density, high-conductivity graphite composite negative electrode material according to claim 1, characterized in that: Step (1) Preparation of porous germanium nanoparticles Magnesium powder, germanium dioxide, zinc chloride and aluminum trichloride were mixed and added to a tube furnace. Magnesium reduction reaction was carried out under certain conditions. After the reaction was completed, the mixture was naturally cooled to room temperature. The resulting material was washed with hydrochloric acid, distilled water and ethanol to remove impurities. Then it was dried under certain vacuum conditions for a period of time to obtain porous germanium nanoparticles. Step (2) Preparation of artificial graphene A certain amount of graphite powder, sodium sulfate and N,N-dimethylformamide (DMF) are mixed evenly, ultrasonically exfoliated and dispersed, and the resulting suspension is centrifuged and cooled to remove the thick layer of graphite, thus obtaining graphene. Step (3) Preparation of graphene oxide / carbon nanotube dispersion The artificial graphene prepared in step (2) was dispersed in deionized water and ultrasonically dispersed; then it was mixed with wet single-arm carbon nanotubes (SWCNTs) and ultrasonically dispersed to obtain graphene oxide / carbon nanotubes (GO / SWCNTs) dispersion. Preferably, step (4) involves the preparation of P-Ge@Graphene materials. The graphene oxide / carbon nanotube (GO / SWCNT) dispersion obtained in step (3) was dispersed in deionized water by ultrasound. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution. After stirring until the solution was clear, it was mixed with the graphene solution dispersed by ultrasound and ultrasound was performed again. Then the pH was adjusted with HCl solution. The solution was then placed in a water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH4) was dissolved in ice water to prepare sodium borohydride (NaBH4) aqueous solution. The sodium borohydride (NaBH4) aqueous solution was slowly added to the above solution while stirring. After stirring, the solution was filtered. The filtered product was placed in a vacuum drying oven for vacuum drying. Then it was placed in a tube sintering furnace. Under an argon-hydrogen atmosphere, the temperature was increased and sintered at a constant temperature for a period of time to obtain P-Ge@Graphene composite material. Step (5) Preparation of PEDOT:PSS aqueous dispersion Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) is dissolved in a certain amount of deionized water, and 3,4-ethylenedioxythiophene (EDOT) is added dropwise. The mixture is stirred slowly, and hydrochloric acid is added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin is slowly added dropwise, and the reaction is stirred rapidly. Inorganic salt ions are exchanged with anion and cation exchange resins for a period of time to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). Step (6) Preparation of P-Ge@Graphene@PEDOT composite material The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed to obtain a P-Ge@Graphene@PEDOT solution. Then it was stirred to evaporate the water and the water was removed under vacuum drying conditions to obtain the P-Ge@Graphene@PEDOT composite material.
3. The preparation process of a high-energy-density, high-conductivity graphite composite negative electrode material according to claim 2, characterized in that: Step (1) Preparation of porous germanium nanoparticles Magnesium powder, germanium dioxide, zinc chloride, and aluminum trichloride were mixed and added to a tube furnace. A magnesium thermoelectric reduction reaction was carried out at 600-650℃ for 3-6 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The resulting material was washed with hydrochloric acid, distilled water, and ethanol to remove impurities. Then, it was dried under vacuum at 50-55℃ for 10-12 hours to obtain porous germanium nanoparticles.
4. The preparation process of a high-energy-density, high-conductivity graphite composite negative electrode material according to claim 3, characterized in that: Step (2) Preparation of artificial graphene 2.5-3g of expandable graphite powder is packaged in a polyester bag. A platinum electrode acts as a conductive current collector in the middle of the graphite powder. The top of the polyester bag is sealed with a clip to prevent the graphite powder from detaching from the graphite electrode during electrochemical exfoliation. The pressure of the graphite powder is set by adjusting the nut. A titanium sheet is used as the cathode and placed in parallel. The distance between the cathode electrode and the graphite electrode is 2-2.5cm. The voltage is 10-12V and the reaction time is 4-5h. After the reaction is completed, the exfoliated product is washed several times with water and ethanol by vacuum filtration. After washing, sodium sulfate and N,N-dimethylformamide (DMF) are added and mixed evenly. Then, ultrasonic exfoliation and dispersion are performed. The resulting suspension is then centrifuged and cooled to remove the thick layer of graphite, thus obtaining graphene.
5. The preparation process of a high-energy-density, high-conductivity graphite composite negative electrode material according to claim 4, characterized in that: Step (3) Preparation of graphene oxide / carbon nanotube dispersion The artificial graphene prepared in step (2) was dispersed in deionized water and ultrasonically dispersed; then it was mixed with wet single-arm carbon nanotubes (SWCNTs) and ultrasonically dispersed to obtain graphene oxide / carbon nanotubes (GO / SWCNTs) dispersion.
6. The preparation process of a high-energy-density, high-conductivity graphite composite negative electrode material according to claim 5, characterized in that: Step (4) Preparation of P-Ge@Graphene material The graphene oxide / carbon nanotube (GO / SWCNT) dispersion obtained in step (3) was ultrasonically dispersed in deionized water for 3-4 hours. The porous germanium nanoparticles and polyvinylpyrrolidone (PVP) prepared in step (1) were dissolved in NaOH aqueous solution and stirred until the solution was clear. Then, it was mixed with the ultrasonically dispersed graphene solution and ultrasonically dispersed again for 1-2 hours. The pH was then adjusted to 7-7.5 with HCl solution. The solution was then placed in a 60-65℃ water bath and stirred at a constant temperature. Excess sodium borohydride (NaBH4) was dissolved in ice water to prepare borohydride solution. Sodium borohydride (NaBH4) aqueous solution was slowly added to the above solution while stirring. After stirring for 3-4 hours, the mixture was filtered. The filtered product was placed in a vacuum drying oven at 60-65℃ and dried for 12-14 hours. Subsequently, it was placed in a tube sintering furnace and sintered at a constant temperature of 700-750℃ (heating rate of 5-6℃ / min) under an argon-hydrogen atmosphere of 10-11%. The mass ratio of graphene to germanium nanoparticles was 1:20-3:200 to obtain P-Ge@Graphene composite material.
7. The preparation process of a high-energy-density, high-conductivity graphite composite negative electrode material according to claim 6, characterized in that: Step (5) Preparation of PEDOT:PSS aqueous dispersion Polystyrene sulfonic acid (PSS) contains amphoteric functional groups, and sulfonic acid is a strong acid. Therefore, it can not only act as a dispersant to improve the solubility of 3,4-ethylenedioxythiophene polymer (PEDOT), but also as a charge-balancing dopant to improve the conductivity of 3,4-ethylenedioxythiophene polymer (PEDOT). Polystyrene sulfonic acid (PSS) is dissolved in deionized water, and 3,4-ethylenedioxythiophene (EDOT) is added dropwise. The mixture is stirred slowly, and hydrochloric acid is added dropwise to control the pH of the system. Then, a mixture of (NH4)2S2O8 and ion exchange resin is slowly added dropwise, and the mixture is stirred rapidly for 24-25 hours. Inorganic salt ions are exchanged with anion and cation exchange resins for 4-5 hours respectively to obtain a deep blue solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS).
8. The preparation process of a high-energy-density, high-conductivity graphite composite negative electrode material according to claim 7, characterized in that: Step (6) Preparation of P-Ge@Graphene@PEDOT composite material The P-Ge@Graphene material prepared in step (3) was dissolved in deionized water and ultrasonically dispersed for 1-1.5 h. Then it was added to the PEDOT:PSS aqueous dispersion prepared in step (4) and ultrasonically dispersed for 1-2 h to obtain a P-Ge@Graphene@PEDOT solution. The water was then evaporated by stirring at 60-65 °C. Vacuum drying was set at 60-70 °C for 12-14 h to remove water and obtain the P-Ge@Graphene@PEDOT composite material.