Graphene-based composite sodium metal negative electrode and preparation method thereof

Abstract

The application provides a graphene-based composite sodium metal negative electrode and a preparation method thereof, and belongs to the technical field of sodium metal batteries.The application constructs a three-dimensional high-conductivity and high-specific-surface graphene-based deposition framework by introducing a carbon nanotube or metal sulfide strategy;electrostatic induction between an ionic liquid and graphene oxide, carbon nanotubes and metal sulfides is utilized to promote the uniform distribution of CNTs and MSx among rGO, reduce the sodium nucleation potential, and induce the uniform deposition of sodium metal;the three-dimensional structure provides more space for sodium storage, effectively alleviates the volume expansion problem of metal sodium;and a physical means is used to uniformly load the graphene-based composite sodium metal negative electrode on a current collector, the negative electrode is loaded into a button cell, an electrochemical deposition method is used, the button cell is discharged, and after the button cell is disassembled, the graphene-based composite sodium metal negative electrode can be obtained.The composite negative electrode can realize dendrite-free uniform deposition, thereby improving the cycle life of the sodium metal negative electrode.

Description

Technical Field

[0001] This invention belongs to the field of sodium metal battery technology, and specifically relates to a type of graphene-based composite sodium metal anode electrode material and its preparation method. This composite material can be used as an electrode material for sodium metal batteries. Background Technology

[0002] The rapid development of portable electronic products, electric vehicles, and smart grids has spurred an urgent demand in modern society for low-cost, high-energy-density batteries. Lithium-ion batteries, due to their excellent electrochemical performance, have been widely used in human production and daily life. However, the uneven distribution of lithium resources has led to a year-on-year increase in their price, fundamentally limiting their application. Sodium, belonging to Group 1 of lithium, shares similar physicochemical properties, and is widely distributed and abundant. Therefore, more and more researchers are focusing on sodium-based batteries. Due to the high theoretical capacity of metallic sodium (1166 mAh·g),... -1 Sodium metal anodes are considered a highly competitive, high-energy-density anode material for sodium-ion batteries due to their low redox potential (-2.714V vs. standard hydrogen electrode). Despite their inherent advantages in energy density and cost, sodium metal batteries still face numerous challenges during charge and discharge. These include safety issues caused by sodium dendrite formation, low coulombic efficiency (CE), and poor cycle stability.

[0003] Given the aforementioned problems faced by sodium metal anodes, numerous researchers have adopted a series of measures to address them. Studies have shown that three-dimensional porous deposition frameworks with high specific surface area can effectively reduce local current density and induce uniform sodium deposition. The three-dimensional porous structure can provide more sodium storage space, mitigating the volume changes of metallic sodium during deposition. Two-dimensional graphene oxide (GO), a lightweight material with a high specific surface area and abundant functional groups, can reduce the nucleation potential of sodium metal and limit the growth of sodium dendrites. However, during the reduction and oxidation process, GO sheets tend to stack, significantly reducing the specific surface area and electronic conductivity of reduced graphene oxide (rGO), thus limiting its practical application in sodium metal batteries.

[0004] The surface of acid-treated carbon nanotubes (CNTs) contains hydroxyl and carboxyl groups, which interact with metallic sodium. Metal sulfides (M...) x S y (Tin disulfide, tin sulfide, bismuth sulfide, molybdenum sulfide, and antimony sulfide) can undergo a gradual alloying reaction during sodium deposition, initially forming Na. x MS x(M-metal atoms) are then converted into Na2S and M, finally forming a Na-M alloy, thereby effectively controlling the nucleation and growth of sodium ions at the interface and achieving uniform deposition of sodium metal. Ionic liquids (ILs) are salts composed of cations and anions that exist in a liquid state below 100℃. Utilizing the electrostatic induction between ILs and GO, CNTs, and metal sulfides, the formation of CNTs and MS can be promoted. x A three-dimensional graphene-based composite material (3D-X / rGO) is constructed by uniformly distributing the reduced graphene oxide layers. The graphene-based composite sodium metal anode (3D-X / rGO@Na) improves the cycle stability of the battery, indicating its great potential for practical applications. Summary of the Invention

[0005] To address the aforementioned issues, a graphene-based composite sodium metal anode and its preparation method have been invented. A three-dimensional graphene-based material (3D-X / rGO) is constructed by utilizing a strategy of electrostatically inducing the uniform distribution of acidified carbon nanotubes or metal sulfides between rGO layers using ionic liquids. This composite material can induce uniform deposition of sodium metal, improving the cycle stability of the 3D-X / rGO@Na composite anode.

[0006] The technical solution of the present invention is as follows:

[0007] A graphene-based composite sodium metal anode comprises sodium metal, a graphene-based composite material, and a current collector.

[0008] The current collector includes copper foil, aluminum foil, copper foam, or nickel foam.

[0009] The graphene-based composite material includes reduced graphene oxide (rGO) and carbon nanotubes (CNTs) or reduced graphene oxide (rGO) and metal sulfides (M). x S y M—metal atom, x, y—1~3).

[0010] The graphene-based composite material (3D-X / rGO, X-CNTs or M) x S y ) structure as Figure 1 The diagram shows a three-dimensional structure with porous cross-linking, which increases the specific surface area of ​​the graphene-based deposition framework.

[0011] The carbon nanotubes mentioned include hydroxylated carbon nanotubes or carboxylated carbon nanotubes.

[0012] The metal sulfides mentioned include tin disulfide, tin sulfide, bismuth sulfide, molybdenum sulfide, or antimony sulfide.

[0013] The thickness of the graphene-based sodium metal composite anode is 1 nm to 600 μm, preferably 200 μm.

[0014] The preparation method of the above-mentioned graphene-based composite sodium metal anode includes the following steps:

[0015] Step 1: After grinding or ultrasonically mixing the ionic liquid IL with graphene oxide GO, a graphene oxide dispersion with a concentration of 3-10 mg / ml is obtained. -1 The mass ratio of IL to GO is (1:1) to (4:1).

[0016] Step 2: Add the graphene oxide dispersion obtained in Step 1 to carbon nanotubes, or add a metal source and a sulfur source to the graphene oxide dispersion and mix thoroughly. Continue ultrasonic treatment to obtain a mixture of graphene oxide-based composite materials. The mass ratio of graphene oxide to carbon nanotubes is (5:1) to (10:1); the mass ratio of graphene oxide to metal source is (1:1) to (5:1); and the molar ratio of metal source to sulfur source is (1:2) to (1:4).

[0017] Step 3: Transfer the graphene oxide-based composite material mixture obtained in Step 2 to a reaction vessel. The reaction temperature is 140-220℃ and the reaction time is 4-24h. After the reaction is completed, wash with deionized water and freeze-dry to obtain a black solid product (3D-X / rGO).

[0018] Step 4: The 3D-X / rGO obtained in Step 3 is attached to the current collector by physical means, dried and sliced, and then installed in a button cell. The counter electrode is a sodium sheet, and constant current discharge is performed under certain current density conditions.

[0019] Step 5: Disassemble the button cell after the discharge treatment in Step 4 to obtain a graphene-based composite sodium metal anode (3D-X / rGO@Na). The content of 3D-X / rGO is 2.5-33 wt%, and the mass content of sodium metal is 2.5-35 wt%.

[0020] The ionic liquids described in step 1 include, but are not limited to: 1-methyl-3-methylimidazolium chloride ([EMIm][Cl]), 1-methyl-3-methylimidazolium fluoride ([EMIm][F]), 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIm][HSO4]), 1-butyl-3-methylimidazolium dihydrogen phosphate ([BMIm][H2PO4]), 1-yl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]), and 1-pentyl-3-methylimidazolium fluoride ([PMIm][F]).

[0021] The carbon nanotubes mentioned in step 2 include, but are not limited to: hydroxylated single-walled carbon nanotubes, hydroxylated multi-walled carbon nanotubes, carboxylated single-walled carbon nanotubes, and hydroxylated multi-walled carbon nanotubes.

[0022] The metal sources mentioned in step 2 include, but are not limited to: tin chloride pentahydrate (SnCl4·5H2O), stannous chloride (SnCl2·2H2O), potassium stannate (K2SnO3·3H2O), sodium molybdate (Na2MoO4·2H2O), bismuth nitrate Bi(NO3)3·9H2O, and antimony chloride (SbCl3).

[0023] The sulfur source mentioned in step 2 includes, but is not limited to: thioacetamide, sodium sulfide, sodium thiosulfate, sulfur powder, and thiourea.

[0024] The freeze drying described in step 3 is performed using a freeze dryer and maintaining the temperature at -50 to -40°C for 24 to 48 hours.

[0025] In step 4, the physical methods include coating, direct pressing, and die pressing. Coating refers to uniformly mixing the prepared composite material with a binder and a conductive agent in a specific mass ratio to form a slurry, coating it onto a current collector, vacuum drying it, and then cutting it with a slicer to form a 10mm diameter sheet with a composite material loading of 1–3 mg·cm³. -2 The tablets are round, and the pressure range for tableting is 5 to 15 MPa.

[0026] The conductive agent includes any one of carbon black, acetylene black, Ketjen black, carbon fiber, etc. The binder includes any one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PAA), etc. The mass percentage of 3D-X / rGO is 80%–90%, the mass percentage of the conductive agent is 0–10%, and the mass percentage of the binder is 0–15%.

[0027] In step 4, after the graphene-based composite material is installed into a button cell, the upper limit of the voltage range is 0.5–1V and the areal current density is 0.5–8 mA·cm. -2 Under these conditions, constant current discharge lasts for 0–16 hours.

[0028] The beneficial effects of this invention are:

[0029] (1) This invention introduces a carbon nanotube or metal sulfide strategy to construct three-dimensional carbon materials with high conductivity and high specific surface area. Its three-dimensional porous structure can not only accelerate the Na... + It can improve the electrode reaction kinetic rate and increase the sodium storage space, effectively alleviating the volume expansion problem of metallic sodium;

[0030] (2) During the deoxygenation reduction of GO, the low surface tension of IL helps to reduce the surface energy of the reduced graphene oxide layer. At the same time, the electrostatic induction between IL and GO, CNTs and metal sulfides can promote the uniform distribution of CNTs and MSx in rGO.

[0031] (3) 3D-X / rGO has abundant sodium-loving sites, which can reduce the nucleation potential of sodium metal and induce uniform deposition of sodium metal, effectively suppressing the formation of sodium dendrites. Attached Figure Description

[0032] Figure 1 (a) shows the 3D-CNTs / rGO prepared in Example 1, and (b) shows the scanning electron microscope image of the CNTs / rGO prepared in the comparative example.

[0033] Figure 2 (a) shows the 3D-CNTs / rGO prepared in Example 2, and (b) shows the sodium metal deposition of the CNTs / rGO prepared in the comparative example at 4 mAh·cm⁻¹. -2 Scanning electron microscope image under the condition.

[0034] Figure 3 Half-cells assembled from the 3D-CNTs / rGO@Na prepared in Example 1 and the CNTs / rGO@Na prepared in the comparative example were used at 0.5 mA·cm⁻¹. -2 1mAh·cm -2 Coulomb efficiency diagram under the given conditions.

[0035] Figure 4 The image shows a scanning electron microscope (SEM) image of the 3D-SnS2 / rGO prepared in Example 3.

[0036] Figure 5 The 3D-SnS2 / rGO@Na assembled half-cell prepared in Example 3 was tested at 2 mA·cm⁻¹. -2 2mAh·cm -2 Coulomb efficiency diagram under the given conditions. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. The specific embodiments described are only for explaining the present invention and not for limiting it.

[0038] Example 1:

[0039] (1) Take 150 mg of graphene oxide and 300 mg of 1-butyl-3-methylimidazolium hydrogen sulfate [BMIm][HSO4] and add them to a 100 mL round bottom flask. Stir well with a glass rod and sonicate at room temperature for 1 h to obtain a GO dispersion with a concentration of 5 mg / mL.

[0040] (2) Add 15 mg of carboxylated multi-walled carbon nanotubes to the GO dispersion obtained in step (1) and continue sonication for 1 h to obtain a black mixture;

[0041] (3) The uniformly mixed black mixture from step (2) was transferred to a 50 mL polytetrafluoroethylene reactor for hydrothermal reaction and kept at a constant temperature of 180 °C for 20 h to obtain a gel-like mixture. After washing with deionized water and freeze-drying for 48 h, 3D-CNTs / rGO was obtained.

[0042] (4) Weigh 3D-CNTs / rGO, conductive agent Ketjen Black, and binder (PVDF) at a mass ratio of 8:1:1, add an appropriate amount of N-methylpyrrolidone (NMP), and stir thoroughly to form a uniform slurry. Coat the slurry onto copper foil, then dry it, and cut it into 10mm diameter discs using a slicer. The loading of 3D-CNTs / rGO is 1.5 mg·cm³. -2 .

[0043] (5) After inserting the disc obtained in step (4) into a button cell, the voltage range is limited to 1V and the areal current density is 0.5mA·cm. -2 The battery was subjected to constant current discharge for 2 hours under certain conditions. The battery was then disassembled to obtain a 3D-CNTs / rGO@Na composite anode, in which the content of 3D-CNTs / rGO was 10.8 wt% and the content of metallic sodium was 6.2 wt%.

[0044] A CR2032 button cell was assembled in an argon-protected glove box. The positive electrode was a copper foil disc loaded with 3D-CNTs / rGO material obtained in step (4), the negative electrode was a sodium sheet, the separator was Celgard 2400, and the electrolyte was 1M sodium salt NaPF6 and solvent diethylene glycol dimethyl ether. The coulombic efficiency of the half cell was tested under the following conditions: areal current density of 0.5 mA·cm⁻¹. -2 The deposition capacity is 1 mAh·cm². -2 .

[0045] Example 2

[0046] (1) Take 100 mg of graphene oxide and 100 mg of 1-butyl-3-methylimidazolium tetrafluoroborate [BMIm][BF4] and add them to a 100 mL round-bottom flask. Stir evenly with a glass rod and sonicate at room temperature for 1 h to obtain a GO dispersion with a concentration of 3 mg / mL.

[0047] (2) Add 20 mg of hydroxylated multi-walled carbon nanotubes to the GO dispersion obtained in step (1) and continue sonication for 1 h to obtain a black mixture;

[0048] (3) The uniformly mixed black mixture from step (2) was transferred to a 50 mL polytetrafluoroethylene reactor for hydrothermal reaction and kept at a constant temperature of 200 °C for 12 h to obtain a gel-like mixture. After washing with deionized water and freeze-drying for 48 h, 3D-CNTs / rGO was obtained.

[0049] (4) Weigh 3D-SnS2 / rGO, conductive carbon black, and binder (PVDF) at a mass ratio of 9:0:1, add an appropriate amount of N-methylpyrrolidone (NMP), and stir thoroughly to form a uniform slurry. Coat the slurry onto aluminum foil, dry it, and then slice it into 10mm diameter discs using a slicer. The loading of 3D-CNTs / rGO is 1 mg·cm³. -2 ;

[0050] (5) After inserting the disc obtained in step (4) into a button cell, the voltage range is limited to 1V and the areal current density is 0.5mA·cm. -2 Under constant current discharge conditions for 8 hours, the battery was disassembled and the disc was removed to obtain the 3D-CNTs / rGO@Na composite anode, in which the content of 3D-CNTs / rGO was 11.2wt% and the content of metallic sodium was 34.6wt%.

[0051] Example 3

[0052] (1) Take 150 mg of graphene oxide and 150 mg of 1-methyl-3-methylimidazolium fluoride ([EMIm][F]) and add them to a 100 mL round bottom flask. Stir evenly with a glass rod and sonicate at room temperature for 1 h to obtain a GO dispersion with a concentration of 5 mg / mL.

[0053] (2) Add 150 mg (0.4279 mmol) tin chloride pentahydrate and 75 mg (0.9982 mmol) thioacetamide to the GO dispersion obtained in step (1), and continue sonication for 1 h to obtain a brown mixture;

[0054] (3) The uniformly mixed mixture from step (2) was transferred to a 50 mL polytetrafluoroethylene reactor for hydrothermal reaction and kept at a constant temperature of 140 °C for 4 h to obtain the SnS2 / rGO composite material. After washing with deionized water and freeze-drying for 36 h, 3D-SnS2 / rGO was obtained.

[0055] (4) Weigh out 3D-SnS2 / rGO, conductive carbon black (Super P), and binder (PTFE) at a mass ratio of 8:0.5:1.5, add an appropriate amount of N-methylpyrrolidone (NMP), and stir thoroughly to form a uniform slurry. Coat the slurry onto aluminum foil, then dry it, and cut it into round slices with a diameter of 10 mm using a slicer. The loading of 3D-SnS2 / rGO is 3.0 mg·cm³. -2.

[0056] (5) After inserting the disc obtained in step (4) into a button cell, the voltage range is limited to an upper limit of 0.5V and the areal current density is 2mA·cm. -2 The battery was subjected to constant current discharge for 1 hour under certain conditions. The battery was then disassembled to obtain a 3D-SnS2 / rGO@Na composite anode, in which the content of 3D-SnS2 / rGO was 32.9 wt% and the content of metallic sodium was 18.8 wt%.

[0057] A CR2032 button cell was assembled in an argon-protected glove box. The positive electrode was a 3D-SnS2 / rGO aluminum foil disc with a load obtained in step (4), the negative electrode was a sodium sheet, the separator was Celgard 2400, and the electrolyte was 1M sodium salt NaPF6 and diethylene glycol dimethyl ether. The half-cell was subjected to coulombic efficiency testing under the following conditions: areal current density of 2 mA·cm⁻¹. -2 The deposition capacity is 2 mAh·cm². -2 .

[0058] Example 4

[0059] (1) Take 150 mg of graphene oxide and 600 mg of 1-butyl-3-methylimidazolium chloride [BMIm][Cl] and add them to a 100 mL round bottom flask. Stir evenly with a glass rod and sonicate at room temperature for 1 h to obtain a GO dispersion with a concentration of 10 mg / mL.

[0060] (2) Add 15 mg of carboxylated multi-walled carbon nanotubes to the GO dispersion obtained in step (1) and continue sonication for 1 h to obtain a black mixture;

[0061] (3) The uniformly mixed black mixture from step (2) was transferred to a 50 mL polytetrafluoroethylene reactor for hydrothermal reaction and kept at a constant temperature of 220 °C for 12 h to obtain a gel-like mixture. After washing with deionized water and freeze-drying for 24 h, 3D-CNTs / rGO was obtained.

[0062] (4) Cut the single-layer nickel foam into 10mm diameter discs using a slicer, place them in a mold, and press 1.5mg of 3D-CNTs / rGO evenly onto the nickel foam discs under a pressure of 5MPa using a mold method. The loading of 3D-CNTs / rGO is 1.9mg·cm³. -2 .

[0063] (5) After inserting the disc obtained in step (4) into a button cell, the voltage range is limited to 1V and the areal current density is 0.5mA·cm. -2The battery was subjected to constant current discharge for 16 hours. The battery was then disassembled to obtain a 3D-CNTs / rGO@Na composite anode, in which the content of 3D-CNTs / rGO was 5.2 wt% and the content of metallic sodium was 18.7 wt%.

[0064] Example 5

[0065] (1) Take 200 mg of graphene oxide and 400 mg of 1-butyl-3-methylimidazolium iodide ([BMIm][I]) and add them to a 100 mL round bottom flask. Stir well with a glass rod and sonicate at room temperature for 1 h to obtain a GO dispersion with a concentration of 7 mg / mL.

[0066] (2) Add 100 mg (0.4856 mmol) sodium molybdate and 148 mg (1.9425 mmol) thiourea to the GO dispersion obtained in step (1), and continue to sonicate for 1 h to obtain a brown mixture;

[0067] (3) The mixture from step (2) was transferred to a 50 mL polytetrafluoroethylene reactor for hydrothermal reaction. The temperature was kept constant at 180 °C for 8 h. After washing with deionized water and freeze-drying for 24 h, the solid product 3D-MoS2 / rGO was obtained.

[0068] (4) Cut the single-layer copper foam into 10mm diameter discs using a slicer, place them in a mold, and press 1.18mg of 3D-MoS2 / rGO composite material evenly onto the copper foam discs under a pressure of 15MPa using a mold method. The loading of 3D-MoS2 / rGO is 1.5mg·cm³. -2 .

[0069] (5) After inserting the disc obtained in step (4) into a button cell, the voltage range is limited to 1V and the areal current density is 8mA·cm. -2 The battery was subjected to constant current discharge for 0.25 hours under certain conditions. The battery was then disassembled to obtain a 3D-MoS2 / rGO@Na composite anode, in which the content of 3D-MoS2 / rGO was 2.5 wt% and the content of metallic sodium was 2.9 wt%.

[0070] Comparative Example

[0071] Comparative Examples 1 and 2 prepared carbon nanotube-reduced graphene oxide composite materials without the use of ionic liquids according to the methods of Examples 1 and 2, respectively. The difference was that no ionic liquid was added in step 1, and the rest was the same as in Examples 1 and 2.

[0072] like Figure 1As shown in (a), the ionic liquid successfully exfoliated the interlayer of rGO and dispersed carbon nanotubes in the interlayer, synthesizing a cross-linked carbon nanotube-supported three-dimensional structure. In contrast, the sheets of graphene oxide reduced without the use of ionic liquids are tightly stacked together, and the carbon nanotubes are randomly and disorderly aggregated on the surface of the reduced graphene oxide, such as... Figure 1 As shown in (b).

[0073] like Figure 2 The sodium plane deposited on the 3D-CNTs / rGO material substrate is relatively flat and smooth, indicating that the synthesized target material is conducive to the uniform deposition of sodium.

[0074] like Figure 3 The half-cell assembled with 3D-CNTs / rGO@Na maintained a high coulombic efficiency throughout 300 charge-discharge cycles, with an average CE of 99.4%, while the half-cell assembled with CNTs / rGO@Na began to fluctuate after about 120 cycles. This indicates that the 3D-CNTs / rGO@Na metal anode has good cycle stability.

[0075] like Figure 4 The results show that SnS2 / rGO with a three-dimensional structure was synthesized, and SnS2 was uniformly distributed between rGO layers.

[0076] like Figure 5 As shown, the half-cell assembled with 3D-SnS2 / rGO@Na maintained a high coulombic efficiency throughout 400 charge-discharge cycles, with an average CE of 99.7%, indicating that the 3D-SnS2 / rGO@Na metal anode has good cycle stability.

Claims

1. A method for preparing a graphene-based composite sodium metal anode, characterized in that, The method includes the following steps: Step 1: After grinding or ultrasonically mixing the ionic liquid IL with graphene oxide GO, a graphene oxide dispersion with a concentration of 3-10 mg / ml is obtained. -1 The mass ratio of IL to GO is 1:1 to 4:

1. Step 2: Add the graphene oxide dispersion obtained in Step 1 to carbon nanotubes, or add a metal source and a sulfur source to the graphene oxide dispersion and mix evenly, then continue ultrasonic treatment to obtain a mixture of graphene oxide-based composite materials; the mass ratio of graphene oxide to carbon nanotubes is 5:1 to 10:1; the mass ratio of graphene oxide to metal source is 1:1 to 5:1, and the molar ratio of metal source to sulfur source is 1:2 to 1:

4. Step 3: Transfer the graphene oxide-based composite material mixture obtained in Step 2 to a reaction vessel. The reaction temperature is 140–220℃, and the reaction time is 4–24 h. After the reaction is complete, wash with deionized water and freeze-dry to obtain a black solid product 3D-X / rGO; where X is CNTs or M x S y M is a metal atom, and x and y take values ​​from 1 to 3; Step 4: The 3D-X / rGO obtained in Step 3 is attached to the current collector by physical means, dried and sliced, and then installed in a button cell. The counter electrode is a sodium sheet, and constant current discharge treatment is performed. Step 5: Disassemble the button cell after the discharge treatment in Step 4 to obtain a graphene-based composite sodium metal anode 3D-X / rGO@Na; wherein the content of 3D-X / rGO is 2.5-33wt% and the mass content of sodium metal is 2.5-35wt%.

2. The preparation method according to claim 1, characterized in that, In step 1, the ionic liquid includes 1-methyl-3-methylimidazolium chloride [EMIm][Cl], 1-methyl-3-methylimidazolium fluoride [EMIm][F], 1-butyl-3-methylimidazolium hydrogen sulfate [BMIm][HSO4], 1-butyl-3-methylimidazolium dihydrogen phosphate [BMIm][H2PO4], 1-yl-3-methylimidazolium tetrafluoroborate [BMIm][BF4], or 1-pentyl-3-methylimidazolium fluoride [PMIm][F].

3. The preparation method according to claim 1 or 2, characterized in that, In step 2, the carbon nanotubes include hydroxylated single-walled carbon nanotubes, hydroxylated multi-walled carbon nanotubes, carboxylated single-walled carbon nanotubes, or hydroxylated multi-walled carbon nanotubes.

4. The preparation method according to claim 1 or 2, characterized in that, In step 2, the metal source includes stannous chloride pentahydrate, stannous chloride, potassium stannate, sodium molybdate, bismuth nitrate, or antimony chloride; the sulfur source includes thioacetamide, sodium sulfide, sodium thiosulfate, sulfur powder, or thiourea.

5. The preparation method according to claim 3, characterized in that, In step 2, the metal source includes stannous chloride pentahydrate, stannous chloride, potassium stannate, sodium molybdate, bismuth nitrate, or antimony chloride; the sulfur source includes thioacetamide, sodium sulfide, sodium thiosulfate, sulfur powder, or thiourea.

6. The preparation method according to claim 1, 2, or 5, characterized in that, In step 4, the physical methods include coating, direct pressing, and mold pressing. Coating involves uniformly mixing the prepared composite material with a binder and a conductive agent to form a slurry, which is then coated onto the current collector. After vacuum drying, the slurry is cut using a slicer to form a 10mm diameter sheet with a composite material loading of 1–3 mg·cm³. -2 The tablets are round, and the pressure range for tableting is 5 to 15 MPa.

7. The preparation method according to claim 6, characterized in that, The conductive agent includes carbon black, acetylene black, Ketjen black, or carbon fiber; the binder includes polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or polyvinyl alcohol (PAA); the mass percentage of 3D-X / rGO is 80%–90%, the mass percentage of the conductive agent is 0–10%, and the mass percentage of the binder is 0–15%.

8. The preparation method according to claim 1, 2, 5 or 7, characterized in that, In step 4, after the graphene-based composite material 3D-X / rGO is installed into a button cell, the upper limit of the voltage range is 0.5–1V and the areal current density is 0.5–8 mA·cm². -2 Under these conditions, constant current discharge lasts for 0–16 hours.

9. The preparation method according to claim 1, 2, 5 or 7, characterized in that, In step 4, the current collector includes copper foil, aluminum foil, copper foam, or nickel foam.

10. A graphene-based composite sodium metal anode obtained by the preparation method according to any one of claims 1-8, characterized in that, The graphene-based composite sodium metal negative electrode has a porous cross-linked three-dimensional structure with a thickness of 1 nm to 600 μm.

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