A method for preparing a tin-thermally expanded graphene oxide composite negative electrode on the surface of a copper foam current collector.

Abstract

This invention relates to a method for preparing a tin-thermally expanded graphene oxide composite anode on the surface of a copper foam current collector, belonging to the technical field of tin-based composite anode materials. The invention uses a copper foam current collector as the cathode and a graphite plate as the anode, with the anode symmetrically placed on both sides of the copper foam current collector. Electrodeposition is performed sequentially in a graphene oxide electrodeposition solution, a tin salt solution, and another graphene oxide electrodeposition solution to form a three-layer structure of graphene oxide-tin oxide-graphene oxide on the surface of the copper foam current collector, thus obtaining a composite anode. The composite anode is then subjected to staged heat treatment to obtain the tin-thermally expanded graphene oxide composite anode on the surface of the copper foam current collector. This tin-thermally expanded graphene oxide composite anode on the surface of a copper foam current collector, as a lithium-ion battery anode material, can shorten the lithium-ion transport and diffusion path, buffer the volume expansion caused during cycling, and improve the specific capacity and cycle stability of the electrode material.

Description

Technical Field

[0001] This invention relates to a method for preparing a tin-thermally expanded graphene oxide composite anode on the surface of a copper foam current collector, belonging to the technical field of tin-based composite anode materials. Background Technology

[0002] High-energy-density lithium-ion batteries, as a primary power source, are widely used in large products such as portable electronic devices and electric vehicles. However, current lithium-ion batteries are not yet well-suited to the development requirements of large-scale energy storage applications such as electric vehicles in terms of energy density and power. The currently widely used graphite anode material has a theoretical specific capacity (372 mAh g / g). -1 The limited capacity of tin-based anode materials severely restricts their application in high-rate, high-energy, and high-stability applications. Therefore, finding high-capacity alternatives to traditional graphite-based anode materials is a current research hotspot. Tin-based anodes possess advantages such as high theoretical capacity, high conductivity, low cost, and good safety. However, as a novel anode material, tin undergoes significant volume expansion during charge and discharge. This massive volume expansion during charging and discharging easily leads to problems such as electrode pulverization, instability of the solid electrolyte interphase (SEI) film, and ion / electron transport barriers, ultimately resulting in rapid capacity decay and poor cycle life of the anode material. Summary of the Invention

[0003] To address the significant capacity decay caused by volume expansion during charge and discharge of tin-based anode materials, this invention proposes a method for preparing a tin-thermally expanded graphene oxide composite anode on the surface of a copper foam current collector. Using a copper foam current collector as the cathode and a graphite plate as the anode, the anodes are symmetrically placed on both sides of the copper foam current collector. Electrodeposition is performed sequentially in a graphene oxide electrodeposition solution, a tin salt solution, and another graphene oxide electrodeposition solution to form a three-layer structure of graphene oxide-tin oxide-graphene oxide on the surface of the copper foam current collector, resulting in a composite anode. This composite anode is then subjected to staged heat treatment to obtain the tin-thermally expanded graphene oxide composite anode on the surface of the copper foam current collector. This tin-thermally expanded graphene oxide composite anode on the surface of a copper foam current collector, as a lithium-ion battery anode material, can shorten the lithium-ion transport and diffusion path, buffer the volume expansion caused during cycling, and improve the specific capacity and cycle stability of the electrode material.

[0004] A method for preparing a tin-thermally expanded graphene oxide composite negative electrode on the surface of a copper foam current collector, the specific steps of which are as follows:

[0005] (1) Dissolve stannous sulfate and potassium pyrophosphate in deionized water to obtain a mixed solution; heat the mixed solution to 50-60°C, add methanesulfonic acid, β-naphthol, natural camphor and formaldehyde in sequence, stir to dissolve, and cool to room temperature to obtain stannous salt solution A;

[0006] (2) Graphene oxide is heat-treated in air to obtain pretreated graphene oxide. The pretreated graphene oxide is added to deionized water and ultrasonically treated to obtain graphene oxide dispersion. Gelatin is added dropwise to the graphene oxide dispersion and ultrasonically treated. The precipitate is removed by standing to obtain graphene oxide electrodeposition solution B.

[0007] (3) Using a copper foam current collector as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector, the graphene oxide is deposited on the cathode surface of the copper foam current collector by electrodeposition in graphene oxide electrodeposition solution B; then using a copper foam current collector with graphene oxide deposited on its surface as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector, the tin oxide is deposited on the surface of the graphene oxide by electrodeposition in tin salt solution A; then using a copper foam current collector with tin deposited on its surface as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector, the graphene oxide is deposited on the tin surface by electrodeposition in graphene oxide electrodeposition solution B. The cathode is then washed with ethanol and deionized water in sequence and dried to obtain the composite negative electrode C.

[0008] (4) The composite negative electrode C is placed in a protective atmosphere and heated at a constant rate to 235-300℃ and held for 1-6 hours. Then, a reducing gas is introduced and the temperature is raised at a constant rate to 400-800℃ and held for 1-3 hours to completely reduce and expand the graphene oxide. Then, it is cooled in the furnace or air to 150-230℃ and held for 1-3 hours to solidify Sn and complete the stabilization treatment, thus obtaining the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector.

[0009] Based on a volume of 100 mL of deionized water, the solution A in step (1) contains 1-3 g of stannous sulfate, 25-75 g of potassium pyrophosphate, 2-6 mL of methanesulfonic acid, 0.01-0.06 g of β-naphthol, 0.01-0.06 g of natural camphor, and 0.04-0.08 g of formaldehyde.

[0010] The heat treatment temperature in step (2) is 300-500℃, and the time is 1-4h.

[0011] In step (2), the concentration of pretreated graphene oxide in the graphene oxide dispersion is 0.005-0.015 g / L, and the volume ratio of gelatin to graphene oxide dispersion is 1-5:100.

[0012] In step (3), the constant voltage for electrodeposition of graphene oxide in the electrodeposition solution B is 1-5V, and the time is 10-60s.

[0013] In step (3), the constant current for electrodeposition in tin salt solution A is 10–20 mA / cm. 2 The duration is 100–600 seconds.

[0014] In step (4), the protective atmosphere is Ar or N2, and the reducing gas is an Ar-H2 mixture.

[0015] The volume fraction of Ar in the Ar-H2 mixture is 85-90%.

[0016] The uniform heating rate in the protective atmosphere is 3–8 °C / min, and the uniform heating rate in the reducing atmosphere is 5–10 °C / min.

[0017] The beneficial effects of this invention are:

[0018] (1) This invention uses copper foam as the current collector, stannous sulfate, potassium pyrophosphate and graphene oxide as raw materials, and methanesulfonic acid, β-naphthol, natural camphor, formaldehyde and gelatin as electrodeposition solution. A three-layer structure of carbon-coated Sn particles is formed by stepwise electrodeposition. Then, a graded heat treatment is performed to obtain a tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector. It is inexpensive, simple to prepare, has low pollution and excellent performance.

[0019] (2) The tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector of the present invention reaches the nanoscale size. The tin nanoparticles have a high surface area, which enhances the wettability of the electrolyte, increases the active sites, and shortens the lithium ion transport and diffusion path. The reduced graphene oxide thin layer provides active sites, increases the electrode capacity, and disperses the tin nanoparticles, reducing the pulverization effect caused by volume expansion.

[0020] (3) The nanostructure of the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector of the present invention can effectively release the influence of volume expansion, thereby avoiding electrode pulverization and maintaining the overall integrity of the electrode, thus significantly improving the specific capacity and cycle stability of the electrode material.

[0021] (4) The tin-thermally expanded graphene oxide composite anode on the surface of the foamed copper current collector of the present invention has a stable capacity of 809 mAh / g after 150 long cycles at a current density of 0.2C, showing excellent specific capacity and cycle stability. Attached Figure Description

[0022] Figure 1 Scanning electron microscope and EDS spectrum of the tin-thermally expanded graphene oxide composite negative electrode sample on the surface of the copper foam current collector in Example 1;

[0023] Figure 2 The cycling performance spectrum of the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector in Example 1 is shown.

[0024] Figure 3 The XRD pattern of the tin-thermally expanded graphene oxide composite negative electrode sample on the surface of the copper foam current collector in Example 2;

[0025] Figure 4 XPS analysis spectrum of tin-thermally expanded graphene oxide composite negative electrode on the surface of copper foam current collector in Example 2;

[0026] Figure 5 Scanning electron microscope and EDS spectrum of the tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector in Example 2.

[0027] Figure 6 The cycling performance spectrum of the tin-thermally expanded graphene oxide composite negative electrode sample on the surface of the copper foam current collector in Example 2 is shown.

[0028] Figure 7 The scanning electron microscope and EDS spectrum of the tin-thermally expanded graphene oxide composite negative electrode sample on the surface of the foamed copper current collector in Example 3 are shown. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0030] Example 1: A method for preparing a tin-thermally expanded graphene oxide composite negative electrode on the surface of a copper foam current collector, the specific steps of which are as follows:

[0031] (1) Dissolve stannous sulfate and potassium pyrophosphate in deionized water to obtain a mixed solution; heat the mixed solution to 50°C, add methanesulfonic acid, β-naphthol, natural camphor and formaldehyde in sequence, stir to dissolve, and cool to room temperature to obtain stannous salt solution A; based on a volume of 100 mL of deionized water, solution A contains 1 g of stannous sulfate, 25 g of potassium pyrophosphate, 2 mL of methanesulfonic acid, 0.01 g of β-naphthol, 0.01 g of natural camphor and 0.04 g of formaldehyde;

[0032] (2) Graphene oxide was placed in an air atmosphere and heat-treated at 300℃ for 1 hour to fully oxidize the graphene oxide and remove impurities to obtain pretreated graphene oxide. The pretreated graphene oxide was added to deionized water and ultrasonically oscillated for 2 hours to fully separate the pretreated graphene oxide to form nano-graphene oxide and obtain graphene oxide dispersion (the concentration of pretreated graphene oxide in the graphene oxide dispersion is 0.005 g / L). Gelatin was added dropwise to the graphene oxide dispersion and ultrasonically oscillated for 40 minutes. The mixture was allowed to stand for 24 hours to remove precipitates to obtain graphene oxide electrodeposition solution B. The volume ratio of gelatin to graphene oxide dispersion was 1:100.

[0033] (3) Using a copper foam current collector as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector (the distance between the anode and the cathode is 2 cm), in a graphene oxide electrodeposition solution B, electrodeposit graphene oxide on the cathode surface of the copper foam current collector for 10 s at a constant voltage of 1 V; then using a copper foam current collector with graphene oxide deposited on its surface as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector (the distance between the anode and the cathode is 2 cm), in a tin salt solution A, at a constant current of 10 mA / cm²... 2 Tin was deposited on the surface of graphene oxide by electrodeposition for 100 seconds. Then, a copper foam current collector with tin deposited on its surface was used as the cathode, and a graphite plate was used as the anode. The anode was symmetrically placed on both sides of the copper foam current collector (the distance between the anode and the cathode was 2 cm). In the graphene oxide electrodeposition solution B, graphene oxide was deposited on the tin surface by electrodeposition for 10 seconds at a constant voltage of 1 V. The cathode was then washed with ethanol and deionized water in sequence and dried to obtain a three-layer composite negative electrode C with carbon-coated Sn particles.

[0034] (4) The three-layer composite anode C with carbon-coated Sn particles is placed in a protective atmosphere (N2) and heated to 235℃ at a heating rate of 3℃ / min and held for 1h (higher than the melting point of Sn, for spheroidization treatment). Then, a reducing gas (90% Ar + 10% H2) is introduced and heated to 400℃ at a heating rate of 5℃ / min and held for 1h to completely reduce and expand the graphene oxide. Then, it is cooled to 150℃ in the furnace and held for 1h to solidify the Sn and complete the stabilization treatment, thus obtaining the tin-thermally expanded graphene oxide composite anode on the surface of the foamed copper current collector.

[0035] The morphology and elemental distribution of the tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector in this embodiment are shown in [reference needed]. Figure 1 ,from Figure 1 It can be seen that Cu is concentrated in a small area, while C, Sn, and O are basically evenly distributed; the film is composed of thermally expanded graphene oxide, and the coated particles are mainly Sn.

[0036] In this embodiment, the tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector is used as the negative electrode of the lithium-ion half-cell. A lithium metal sheet is used as the reference and counter electrode. The electrolyte is 1 mol / L LiPF6 (EC:DMC:EMC = 1:1:1 v / v), with 10% FEC solution added. The cycle performance of the lithium-ion half-cell after 150 cycles is shown in the figure. Figure 2 ,from Figure 2 It can be seen that at a current density of 0.2C, after 150 long cycles, it has a high capacity of 693mAh / g.

[0037] Example 2: A method for preparing a tin-thermally expanded graphene oxide composite negative electrode on the surface of a copper foam current collector, the specific steps of which are as follows:

[0038] (1) Dissolve stannous sulfate and potassium pyrophosphate in deionized water to obtain a mixed solution; heat the mixed solution to 55°C, add methanesulfonic acid, β-naphthol, natural camphor and formaldehyde in sequence, stir to dissolve, and cool to room temperature to obtain stannous salt solution A; based on 100 mL of deionized water, solution A contains 2 g of stannous sulfate, 50 g of potassium pyrophosphate, 4 mL of methanesulfonic acid, 0.03 g of β-naphthol, 0.03 g of natural camphor and 0.06 g of formaldehyde;

[0039] (2) Graphene oxide was placed in an air atmosphere and heat-treated at 400℃ for 2 hours to fully oxidize the graphene oxide and remove impurities to obtain pretreated graphene oxide. The pretreated graphene oxide was added to deionized water and ultrasonically oscillated for 3 hours to fully separate the pretreated graphene oxide to form nano-graphene oxide to obtain graphene oxide dispersion (the concentration of pretreated graphene oxide in the graphene oxide dispersion is 0.010 g / L). Gelatin was added dropwise to the graphene oxide dispersion and ultrasonically oscillated for 30 minutes. The mixture was allowed to stand for 20 hours to remove precipitates to obtain graphene oxide electrodeposition solution B. The volume ratio of gelatin to graphene oxide dispersion was 3:100.

[0040] (3) Using a copper foam current collector as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector (the distance between the anode and the cathode is 3 cm), in a graphene oxide electrodeposition solution B, electrodeposit graphene oxide on the cathode surface of the copper foam current collector for 30 s at a constant voltage of 3 V; then using a copper foam current collector with graphene oxide deposited on its surface as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector (the distance between the anode and the cathode is 3 cm), in a tin salt solution A, at a constant current of 15 mA / cm²... 2 Tin was deposited on the surface of graphene oxide by electrodeposition for 300 seconds. Then, a copper foam current collector with tin deposited on its surface was used as the cathode, and a graphite plate was used as the anode. The anodes were symmetrically placed on both sides of the copper foam current collector (the distance between the anode and the cathode was 3 cm). In the graphene oxide electrodeposition solution B, graphene oxide was deposited on the tin surface by electrodeposition at a constant voltage of 3V for 30 seconds. The cathode was then washed with ethanol and deionized water in sequence and dried to obtain a three-layer composite negative electrode C with carbon-coated Sn particles.

[0041] (4) The three-layer composite anode C with carbon-coated Sn particles is placed in a protective atmosphere (Ar), heated at a rate of 5℃ / min to 270℃ and held for 3h (higher than the melting point of Sn, for spheroidization treatment), then a reducing gas (88%Ar+12%H2) is introduced, and the temperature is raised at a rate of 8℃ / min to 600℃ and held for 2h to completely reduce and expand the graphene oxide. Then it is air-cooled to 200℃ and held for 2h to solidify the Sn and complete the stabilization treatment, thus obtaining the tin-thermally expanded graphene oxide composite anode on the surface of the copper foam current collector.

[0042] The X-ray diffraction pattern of the tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector in this embodiment is shown below. Figure 3 ,from Figure 3 It can be seen that the characteristic peak of graphene oxide exists around 9.28 degrees; in the XRD pattern of Cu / rGO@Sn electrode, only the characteristic peak of the copper foam current collector matrix can be observed, and no characteristic peak of graphene oxide is found.

[0043] The X-ray photoelectron spectroscopy of the tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector in this embodiment is shown in [reference needed]. Figure 4 ,from Figure 4 It can be seen that the carbon peak of the composite material can be decomposed into four characteristic peaks; among them, the highest bond strength is the C-C bond and the C=C bond (284.98 eV), while the binding energies of CO, C=O and C-OO bonds are also shown, located at 285.98 eV, 288.38 eV and 289.78 eV respectively; indicating that GO was successfully reduced to rGO by hydrogen heat treatment, and the structural integrity can still be maintained under hydrogen reduction.

[0044] The morphology and elemental distribution of the tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector in this embodiment are shown in [reference needed]. Figure 5 ,from Figure 5 It can be seen that the tin particles are deposited very uniformly, and the particle size has also been reduced to nanoscale.

[0045] In this embodiment, the tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector is used as the negative electrode of the lithium-ion half-cell. A lithium metal sheet is used as the reference and counter electrode. The electrolyte is 1 mol / L LiPF6 (EC:DMC:EMC = 1:1:1 v / v), with 10% FEC solution added. The cycle performance of the lithium-ion half-cell after 150 cycles is shown in the figure. Figure 6 ,from Figure 6 It can be seen that at a current density of 0.2C, after 150 long cycles, it has a high capacity of 809mAh / g, demonstrating excellent specific capacity and cycle stability.

[0046] Example 3: A method for preparing a tin-thermally expanded graphene oxide composite negative electrode on the surface of a copper foam current collector, the specific steps of which are as follows:

[0047] (1) Dissolve stannous sulfate and potassium pyrophosphate in deionized water to obtain a mixed solution; heat the mixed solution to 60°C, add methanesulfonic acid, β-naphthol, natural camphor and formaldehyde in sequence, stir to dissolve, and cool to room temperature to obtain stannous salt solution A; based on 100 mL of deionized water, solution A contains 3 g of stannous sulfate, 75 g of potassium pyrophosphate, 6 mL of methanesulfonic acid, 0.06 g of β-naphthol, 0.06 g of natural camphor and 0.08 g of formaldehyde;

[0048] (2) Graphene oxide was placed in an air atmosphere and heat-treated at 500℃ for 4 hours to fully oxidize the graphene oxide and remove impurities to obtain pretreated graphene oxide. The pretreated graphene oxide was added to deionized water and ultrasonically oscillated for 4 hours to fully separate the pretreated graphene oxide to form nano-graphene oxide to obtain graphene oxide dispersion (the concentration of pretreated graphene oxide in the graphene oxide dispersion was 0.015 g / L). Gelatin was added dropwise to the graphene oxide dispersion and ultrasonically oscillated for 50 min. The mixture was allowed to stand for 22 hours to remove precipitates to obtain graphene oxide electrodeposition solution B. The volume ratio of gelatin to graphene oxide dispersion was 5:100.

[0049] (3) Using a copper foam current collector as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector (the distance between the anode and the cathode is 6 cm), in a graphene oxide electrodeposition solution B, electrodeposit graphene oxide on the cathode surface of the copper foam current collector for 60 s at a constant voltage of 5 V; then using a copper foam current collector with graphene oxide deposited on its surface as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector (the distance between the anode and the cathode is 6 cm), in a tin salt solution A, at a constant current of 20 mA / cm 2 Tin was deposited on the surface of graphene oxide by electrodeposition for 600 seconds. Then, a copper foam current collector with tin deposited on its surface was used as the cathode, and a graphite plate was used as the anode. The anode was symmetrically placed on both sides of the copper foam current collector (the distance between the anode and the cathode was 6 cm). In the graphene oxide electrodeposition solution B, graphene oxide was deposited on the tin surface by electrodeposition at a constant voltage of 5V for 60 seconds. The cathode was cleaned with ethanol and deionized water in sequence and dried to obtain a three-layer composite negative electrode C with carbon-coated Sn particles.

[0050] (4) The three-layer composite anode C with carbon-coated Sn particles is placed in a protective atmosphere (N2) and heated to 300℃ at a heating rate of 8℃ / min and held for 6h (higher than the melting point of Sn, for spheroidization treatment). Then, a reducing gas (85% Ar + 15% H2) is introduced and heated to 800℃ at a heating rate of 10℃ / min and held for 3h to completely reduce and expand the graphene oxide. Then, it is cooled to 230℃ in the furnace and held for 3h to solidify the Sn and complete the stabilization treatment, thus obtaining the tin-thermally expanded graphene oxide composite anode on the surface of the foamed copper current collector.

[0051] The morphology and elemental distribution of the tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector in this embodiment are shown in [reference needed]. Figure 7 ,from Figure 7 It can be seen that the surface layer of the electrode is composed of a small amount of Sn element and thermally expanded graphene oxide.

[0052] The tin-thermally expanded graphene oxide composite anode on the surface of the copper foam current collector exhibits a capacity of 735 mAh / g after 150 cycles at a current density of 0.2C, demonstrating good specific capacity and cycle stability.

[0053] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a tin-thermally expanded graphene oxide composite negative electrode on the surface of a copper foam current collector, characterized in that, The specific steps are as follows: (1) Dissolve stannous sulfate and potassium pyrophosphate in deionized water to obtain a mixed solution; heat the mixed solution to 50-60°C, add methanesulfonic acid, β-naphthol, natural camphor and formaldehyde in sequence, stir to dissolve, and cool to room temperature to obtain stannous salt solution A; (2) Graphene oxide is heat-treated in air to obtain pretreated graphene oxide. The pretreated graphene oxide is added to deionized water and ultrasonically treated to obtain graphene oxide dispersion. Gelatin is added dropwise to the graphene oxide dispersion and ultrasonically treated. The precipitate is removed by standing to obtain graphene oxide electrodeposition solution B. (3) Using a copper foam current collector as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector, the graphene oxide is deposited on the cathode surface of the copper foam current collector by electrodeposition in graphene oxide electrodeposition solution B; then using a copper foam current collector with graphene oxide deposited on its surface as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector, the tin oxide is deposited on the surface of the graphene oxide by electrodeposition in tin salt solution A; then using a copper foam current collector with tin deposited on its surface as the cathode and a graphite plate as the anode, with the anodes symmetrically placed on both sides of the copper foam current collector, the graphene oxide is deposited on the tin surface by electrodeposition in graphene oxide electrodeposition solution B. The cathode is then washed with ethanol and deionized water in sequence and dried to obtain the composite negative electrode C. (4) The composite negative electrode C is placed in a protective atmosphere and heated at a constant rate to 235-300℃ and kept at that temperature for 1-6 hours. Then, a reducing gas is introduced and the temperature is raised at a constant rate to 400-800℃ and kept at that temperature for 1-3 hours. Then, it is cooled in the furnace or in the air to 150-230℃ and kept at that temperature for 1-3 hours to obtain the tin-thermally expanded graphene oxide composite negative electrode on the surface of the copper foam current collector.

2. The method for preparing the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector according to claim 1, characterized in that: Based on a volume of 100 mL of deionized water, the solution A in step (1) contains 1-3 g of stannous sulfate, 25-75 g of potassium pyrophosphate, 2-6 mL of methanesulfonic acid, 0.01-0.06 g of β-naphthol, 0.01-0.06 g of natural camphor, and 0.04-0.08 g of formaldehyde.

3. The method for preparing the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector according to claim 1, characterized in that: Step (2) involves heat treatment at a temperature of 300–500℃ for 1–4 hours.

4. The method for preparing the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector according to claim 1, characterized in that: In step (2), the concentration of pretreated graphene oxide in the graphene oxide dispersion is 0.005 to 0.015 g / L, and the volume ratio of gelatin to graphene oxide dispersion is 1 to 5:

100.

5. The method for preparing the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector according to claim 1, characterized in that: Step (3) Electrodeposition of graphene oxide in solution B is performed at a constant voltage of 1-5V for 10-60s.

6. The method for preparing the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector according to claim 1, characterized in that: Step (3) The constant current for electrodeposition in tin salt solution A is 10-20 mA / cm. 2 The duration is 100–600 seconds.

7. The method for preparing the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector according to claim 1, characterized in that: Step (4) The protective atmosphere is Ar or N2, and the reducing gas is a mixture of Ar-H2.

8. The method for preparing the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector according to claim 7, characterized in that: The volume fraction of Ar in the Ar-H2 mixture is 85-90%.

9. The method for preparing the tin-thermally expanded graphene oxide composite negative electrode on the surface of the foamed copper current collector according to claim 7, characterized in that: The uniform heating rate in the protective atmosphere is 3–8 °C / min, and the uniform heating rate in the reducing atmosphere is 5–10 °C / min.

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