Preparation method and application of double-coated sodium ion battery negative electrode material

Abstract

The present invention relates to the field of sodium-ion batteries and discloses a method for preparing a double-coated sodium-ion battery negative electrode material and its application. The preparation method comprises: 1) uniformly mixing a tin source solution, a graphene dispersion, a carbon nanotube dispersion, and soluble carbon, spraying, drying, and sintering to obtain agglomerates of graphene / carbon nanotube-coated tin powder; 2) crushing the agglomerates to obtain graphene / carbon nanotube-coated tin powder; and 3) mixing the graphene / carbon nanotube-coated tin powder with a gaseous carbon source under a heated protective atmosphere, and performing gaseous coating to form a carbon coating layer to obtain a double-coated sodium-ion battery negative electrode material. The sodium-ion battery negative electrode material prepared by the method of the present invention comprises an inner coating layer of graphene / carbon nanotubes and an outer coating layer of carbon, which not only significantly improves the conductivity of the material but also effectively suppresses volume changes in the tin-based negative electrode material.

Description

Technical Field

[0001] The present invention relates to the field of sodium ion batteries, and in particular to a preparation method and application of a double-coated layer sodium ion battery negative electrode material. Background Art

[0002] Sodium-ion batteries, with their low cost advantages, have seen rapid technological development and rapid improvements in battery performance in recent years. Simultaneously, key materials such as sodium-based cathodes and amorphous carbon anodes have become increasingly mature and are gradually gaining large-scale application. Currently, sodium-ion battery products are widely used in electric two-wheelers, low-speed vehicles, and energy storage applications.

[0003] Currently, the negative electrode materials for sodium-ion batteries are generally based on amorphous carbon, namely soft carbon and hard carbon. However, the main problem with amorphous carbon is its low initial coulombic efficiency. A large amount of active sodium is consumed during the formation phase, resulting in a decrease in the specific energy of the battery cell and increased costs. Furthermore, amorphous carbon has a limited sodium storage capacity of only around 300 mAh / g, resulting in a low battery energy density. Furthermore, amorphous carbon has a low sodium insertion potential, close to 0V, making it prone to sodium precipitation at high charge states, causing battery failure and, in severe cases, safety accidents.

[0004] To this end, tin-based alloy anode materials with higher sodium storage capacity have been developed (for example, CN110212238A discloses a tin-based anode sodium-ion secondary battery). Its sodium storage capacity can reach 847 mAh / g, making it an ideal anode active material. However, tin-based alloy anode materials also have drawbacks: relatively poor conductivity, large volume changes during charge and discharge, and rapid capacity decay, making them difficult to apply in practice. Summary of the Invention

[0005] To address the above technical issues, the present invention provides a method for preparing a double-coated sodium-ion battery anode material and its application. The sodium-ion battery anode material prepared by the present method comprises an inner coating of graphene / carbon nanotubes and an outer coating of carbon. This method not only significantly improves the material's conductivity but also effectively suppresses volume changes in tin-based anode materials.

[0006] The specific technical solutions of the present invention are:

[0007] In a first aspect, the present invention provides a method for preparing a double-coated layer sodium ion battery negative electrode material, which comprises the following steps:

[0008] 1) The tin source solution, graphene dispersion, carbon nanotube dispersion and soluble carbon are uniformly mixed, sprayed, dried and sintered in a reducing atmosphere to obtain graphene / carbon nanotube-coated tin powder agglomerates.

[0009] 2) crushing the agglomerates to obtain graphene / carbon nanotube-coated tin powder.

[0010] 3) The graphene / carbon nanotube coated tin powder is mixed with a gaseous carbon source under a heated protective atmosphere, and a carbon coating layer is formed on the surface of the graphene / carbon nanotube coated tin powder after gas phase coating to obtain a double-coated sodium ion battery negative electrode material.

[0011] To address the shortcomings of existing sodium-ion tin-based alloy anode materials, which suffer from poor conductivity, large volume changes during charge and discharge, and rapid specific capacity decay, the present invention first coats the surface of tin powder with a graphene / carbon nanotube composite material through wet spray granulation and reducing atmosphere sintering. The introduction of soluble carbon during the spraying process provides sufficient reaction sites for tin reduction. The coating formed by this wet spray granulation-sintering process is more complete and uniform, effectively improving the performance of the anode material. Furthermore, the present invention further forms a carbon coating layer on the surface of the graphene / carbon nanotube-coated tin powder through vapor deposition, thereby obtaining a sodium-ion battery anode material with a double-layer coating structure. In this double-layer sodium-ion battery anode material, the inner coating layer (graphene / carbon nanotubes) of the planar graphene and the fibrous carbon nanotubes form a line-surface conductive network, significantly improving the material's conductivity and providing a flexible buffer space to mitigate the volume changes caused by sodium ion insertion and extraction, thereby extending the anode material's service life. The outer carbon coating layer can not only further inhibit the volume expansion of the tin-based negative electrode material, but also improve the compatibility of the material with the electrolyte, forming a stable SEI film layer.

[0012] Preferably, in step 1), the mass ratio of the tin source, graphene, carbon nanotubes and soluble carbon is in the range of 1:(0.01-0.02):(0.01-0.02):(1.8-2.7).

[0013] The present invention requires strict control of the amount of graphene, carbon nanotubes and soluble carbon relative to tin. The present invention found that when the content of graphene and carbon nanotubes is too low, a line-surface conductive network cannot be formed, and the electronic conductivity of the material decreases; while too high will lead to a decrease in the specific capacity of the material, and at the same time, the agglomeration of the bulk phase of the material increases. Soluble carbon is mainly used for pyrolysis of carbon sources to generate carbon matrix dispersed metal tin particles, to prevent their high-temperature agglomeration, and then to form nano-scale uniformly distributed tin particles; at the same time, it also acts as an auxiliary reduction role, reducing part of the tin oxide produced by spray pyrolysis from the bulk phase. Too high or too low a soluble carbon content will have a negative effect on the uniformity of the bulk phase of the material and the electrochemical properties of the material.

[0014] Preferably, the particle size of the graphene / carbon nanotube coated tin powder is 2-5 μm.

[0015] The present invention discovered that the particle size of graphene / carbon nanotube-coated tin powder has a certain impact on the performance of the final material. If the particle size is too large, the material's specific capacity cannot be fully utilized. At the same time, the contact area between the material and the electrolyte is small, and the material's rate performance at high current densities is significantly reduced. Conversely, if the particle size is too small, the material's chemical activity is correspondingly enhanced, and side reactions increase after contact with the electrolyte, increasing polarization and reducing electrochemical performance.

[0016] Preferably, the carbon coating layer accounts for 2-6 wt % of the double-coated layer sodium ion battery negative electrode material.

[0017] The present invention found that the content of the carbon coating also has a certain influence on the performance of the final material. If the carbon coating is too thick, the transmission resistance of sodium ions in the negative electrode material will increase, thereby causing the capacity of the battery to decay. This is because a thicker carbon coating will increase the internal resistance of the electrode material, affecting the embedding and extraction efficiency of sodium ions in the electrode material. The carbon coating can buffer the volume change of the electrode during the charge and discharge process and maintain the structural stability of the electrode. A carbon coating that is too thin cannot provide sufficient support and may cause structural damage to the electrode material during the cycle, resulting in capacity decay. Due to the large ionic radius of sodium ions, the volume will expand and contract significantly during the charge and discharge process of the tin-based negative electrode material. A sufficient carbon coating can effectively suppress this volume change, but a too thin carbon coating cannot be effectively controlled, which may cause damage to the electrode material and a decline in battery performance.

[0018] Preferably, in step 1), the tin source is tin halide; more preferably tin chloride or tin bromide.

[0019] The type of tin source has a certain impact on the spray granulation effect. The present invention has found that the above-mentioned types of tin halides are selected as tin sources not only because they are soluble in water, but also because they can be more evenly combined with the graphene dispersion, providing more uniform reaction sites for the subsequent generation of reduced tin blocks, thereby improving the purity of the material.

[0020] Preferably, in step 1), the soluble carbon is selected from glucose, citric acid and ascorbic acid.

[0021] The present invention selects the above-mentioned glucose, citric acid and ascorbic acid as soluble carbon mainly because these carbon sources are pyrolyzed to generate a carbon matrix that disperses the metal tin particles more effectively, thereby preventing the metal tin particles from agglomerating at high temperatures and thereby forming nanoscale uniformly distributed tin particles. At the same time, these carbon sources can also act as auxiliary reducing agents, reducing part of the tin oxide produced by the spray pyrolysis from within the bulk phase.

[0022] Preferably, in step 1), the concentration of the tin source solution is 0.2-0.5 mol / L; the concentration of the graphene dispersion is 0.5-2 wt %; and the concentration of the carbon nanotube dispersion is 0.5-2 wt %.

[0023] Preferably, in step 1), the sintering temperature is 800-1200° C. and the sintering time is 8-12 h.

[0024] Preferably, in step 1), the atmosphere required for sintering is H2 / N2, wherein the mass proportion of hydrogen is 1-4 wt%, and the optimal is 2 wt%.

[0025] Preferably, in step 3), the gaseous carbon source is selected from methane, ethylene, acetylene and benzene.

[0026] The gaseous carbon sources selected in the present invention are all gas molecules with fewer carbon atoms, which are conducive to deposition on the surface of the tin negative electrode material.

[0027] Preferably, in step 3), the protective atmosphere is selected from argon, nitrogen, helium, neon, krypton and xenon.

[0028] Preferably, in step 3), the temperature of the gas-phase coating is 700-900° C., and the time is 3-5 hours.

[0029] Preferably, in step 3), the thickness of the carbon coating layer is 50-150 nm, and the optimal thickness is 80-120 nm.

[0030] In a second aspect, the present invention provides the use of the double-coated sodium ion battery negative electrode material obtained by the above preparation method in a sodium ion battery.

[0031] Preferably, the method for preparing the sodium ion battery comprises the following steps:

[0032] S1, preparing a positive electrode sheet;

[0033] S2. Evenly mix the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent, disperse the mixture, and obtain a negative electrode slurry, which is then coated on a negative electrode current collector to obtain a negative electrode sheet;

[0034] S3. Assemble the positive electrode sheet, negative electrode sheet and separator into a battery cell, and then further make a sodium ion battery.

[0035] Further preferably, S1 specifically includes: uniformly mixing the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, dispersing the mixture to obtain a positive electrode slurry, and coating the mixture on a positive electrode current collector to obtain a positive electrode sheet.

[0036] Further preferably, S3 specifically includes: winding or stacking the positive electrode sheet, the negative electrode sheet and the separator to assemble a battery cell, baking to remove water, and then injecting liquid and forming to make a sodium ion battery.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The method of the present invention can produce a sodium ion battery negative electrode material with a double-layer coating structure, wherein the inner coating layer is graphene / carbon nanotubes. The graphene with a planar structure and the carbon nanotubes with a fibrous structure are combined to form a line-surface conductive network, which can not only significantly improve the conductivity of the material, but also provide an elastic buffer space to alleviate the volume change caused by the insertion / extraction process of sodium ions in the negative electrode material, thereby improving the service life of the negative electrode material; and the outer carbon coating layer can further inhibit the volume expansion of the tin-based negative electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a diagram of the double-coating structure under a high-resolution transmission electron microscope in Example 1.

[0040] Figure 2 Schematic diagram of the thickness of the carbon coating layer of the material under high-resolution transmission electron microscopy in Example 1. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the embodiments.

[0042] In a first aspect, the present invention provides a method for preparing a double-coated layer sodium ion battery negative electrode material, which comprises the following steps:

[0043] 1) The tin source solution, graphene dispersion, carbon nanotube dispersion and soluble carbon are uniformly mixed, sprayed, dried and sintered in a reducing atmosphere to obtain graphene / carbon nanotube-coated tin powder agglomerates.

[0044] In some preferred implementation cases, in step 1), the mass ratio of the tin source, graphene, carbon nanotubes and soluble carbon is in the range of 1:(0.01-0.02):(0.01-0.02):(1.8-2.7).

[0045] In some preferred implementation cases, in step 1), the tin source is tin halide; more preferably tin chloride or tin bromide.

[0046] In some preferred embodiments, in step 1), the soluble carbon is selected from glucose, citric acid and ascorbic acid.

[0047] In some preferred implementation cases, in step 1), the concentration of the tin source solution is 0.2-0.5 mol / L; the concentration of the graphene dispersion is 0.5-2 wt %; and the concentration of the carbon nanotube dispersion is 0.5-2 wt %.

[0048] In some preferred implementation cases, in step 1), the atmosphere required for sintering is H2 / N2, wherein the mass proportion of hydrogen is 1-4 wt%, and optimally 2 wt%.

[0049] In some preferred implementation cases, in step 1), the sintering temperature is 800-1200° C., and the sintering time is 8-12 hours.

[0050] 2) crushing the agglomerates to obtain graphene / carbon nanotube-coated tin powder with a particle size of 2-5 μm.

[0051] 3) Mixing the graphene / carbon nanotube-coated tin powder with a vapor-phase carbon source under a heated protective atmosphere, and forming a carbon coating layer on the surface of the graphene / carbon nanotube-coated tin powder after vapor-phase coating to obtain a double-coated sodium-ion battery anode material. The carbon coating layer accounts for 2-6 wt% of the double-coated sodium-ion battery anode material.

[0052] In some preferred implementation cases, in step 3), the thickness of the carbon coating layer is 50-150 nm, and the optimal thickness is 80-120 nm.

[0053] In some preferred implementation cases, in step 3), the gaseous carbon source is selected from methane, ethylene, acetylene and benzene.

[0054] In some preferred embodiments, in step 3), the protective atmosphere is selected from argon, nitrogen, helium, neon, krypton and xenon.

[0055] In some preferred implementation cases, in step 3), the temperature of the vapor coating is 700-900° C., and the time is 3-5 hours.

[0056] In a second aspect, the present invention provides the use of the double-coated sodium ion battery negative electrode material obtained by the above preparation method in a sodium ion battery.

[0057] In some preferred implementation cases, the method for preparing the sodium ion battery comprises the following steps:

[0058] S1. Prepare the positive electrode sheet.

[0059] In some more preferred implementation cases, S1 specifically includes: uniformly mixing the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, dispersing the mixture to obtain a positive electrode slurry, and coating the mixture on a positive electrode current collector to obtain a positive electrode sheet.

[0060] S2. Evenly mix the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent, disperse them to obtain a negative electrode slurry, and apply it on a negative electrode current collector to obtain a negative electrode sheet.

[0061] S3. Assemble the positive electrode sheet, negative electrode sheet and separator into a battery cell, and then further make a sodium ion battery.

[0062] In some more preferred implementation cases, S3 specifically includes: winding or stacking the positive electrode sheet, the negative electrode sheet and the separator to assemble a battery cell, baking to remove water, and then injecting liquid and forming to make a sodium ion battery.

[0063] Specific Examples and Comparative Examples.

[0064] Example 1

[0065] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0066] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (ascorbic acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0067] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0068] 3) The graphene / carbon nanotube-coated tin powder was mixed with a vapor-phase carbon source (methane) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 80 seem. Vapor-phase coating was performed at 800°C for 3 hours. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 90-110 nm and accounted for approximately 4 wt% of the double-coated sodium-ion battery anode material.

[0069] Figure 1 This is a diagram of the double-coating structure under a high-resolution transmission electron microscope in Example 1. Figure 2 Schematic diagram of the thickness of the carbon coating layer of the material under high-resolution transmission electron microscopy in Example 1.

[0070] (2) Preparation of sodium ion battery, including the following steps:

[0071] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0072] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0073] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0074] Example 2 (Compared with Example 1, the only difference is that the tin source is tin bromide, the soluble carbon is glucose, and the gaseous carbon source is ethylene)

[0075] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0076] 1) A tin source solution (tin bromide, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (glucose) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0077] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0078] 3) The graphene / carbon nanotube-coated tin powder was mixed with a vapor-phase carbon source (ethylene) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 80 seem. Vapor-phase coating was performed at 800°C for 3 hours. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 90-110 nm and accounted for approximately 4 wt% of the double-coated sodium-ion battery anode material.

[0079] (2) Preparation of sodium ion battery, including the following steps:

[0080] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0081] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0082] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0083] Example 3 (Compared with Example 1, the only difference is that the soluble carbon is citric acid and the gaseous carbon source is benzene)

[0084] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0085] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (citric acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0086] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0087] 3) Mixing the graphene / carbon nanotube-coated tin powder with a vapor-phase carbon source (benzene) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 80 seem. Vapor-phase coating was performed at 800°C for 3 hours. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 90-110 nm and accounted for approximately 4 wt% of the double-coated sodium-ion battery anode material.

[0088] (2) Preparation of sodium ion battery, including the following steps:

[0089] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0090] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0091] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0092] Comparative Example 1 (Compared with Example 1, the only difference is that the ratio of graphene, carbon nanotubes and soluble carbon to tin source is too low)

[0093] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0094] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (ascorbic acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.005:0.005:1.5.

[0095] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0096] 3) The graphene / carbon nanotube-coated tin powder was mixed with a vapor-phase carbon source (methane) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 80 seem. Vapor-phase coating was performed at 800°C for 3 hours. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 90-110 nm and accounted for approximately 4 wt% of the double-coated sodium-ion battery anode material.

[0097] (2) Preparation of sodium ion battery, including the following steps:

[0098] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0099] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0100] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0101] Comparative Example 2 (Compared with Example 1, the only difference is that the ratio of graphene, carbon nanotubes and soluble carbon to the tin source is too high)

[0102] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0103] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (ascorbic acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.04:0.04:4.

[0104] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0105] 3) The graphene / carbon nanotube-coated tin powder was mixed with a vapor-phase carbon source (methane) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 80 seem. Vapor-phase coating was performed at 800°C for 3 hours. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 90-110 nm and accounted for approximately 4 wt% of the double-coated sodium-ion battery anode material.

[0106] (2) Preparation of sodium ion battery, including the following steps:

[0107] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0108] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0109] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0110] Comparative Example 3 (Comparative Example 3 differs from Example 1 only in that the particle size of the graphene / carbon nanotube-coated tin powder obtained in step 2 is too small)

[0111] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0112] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (ascorbic acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0113] 2) crushing the agglomerates to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 1 μm.

[0114] 3) The graphene / carbon nanotube-coated tin powder was mixed with a vapor-phase carbon source (methane) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 80 seem. Vapor-phase coating was performed at 800°C for 3 hours. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 90-110 nm and accounted for approximately 4 wt% of the double-coated sodium-ion battery anode material.

[0115] (2) Preparation of sodium ion battery, including the following steps:

[0116] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0117] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0118] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0119] Comparative Example 4 (Comparative Example 4 differs from Example 1 only in that the particle size of the graphene / carbon nanotube-coated tin powder obtained in step 2 is too large)

[0120] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0121] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (ascorbic acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0122] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 10 μm.

[0123] 3) The graphene / carbon nanotube-coated tin powder was mixed with a vapor-phase carbon source (methane) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 80 seem. Vapor-phase coating was performed at 800°C for 3 hours. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 90-110 nm and accounted for approximately 4 wt% of the double-coated sodium-ion battery anode material.

[0124] (2) Preparation of sodium ion battery, including the following steps:

[0125] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0126] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0127] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0128] Comparative Example 5 (Comparative Example 5 differs from Example 1 only in that it has only one coating layer and no outer carbon coating layer)

[0129] (1) Preparation of single-coating layer sodium ion battery negative electrode material, including the following steps:

[0130] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (ascorbic acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0131] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0132] (2) Preparation of sodium ion battery, including the following steps:

[0133] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0134] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0135] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0136] Comparative Example 6 (Comparative Example 6 differs from Example 1 only in that the outer carbon coating layer is too thin)

[0137] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0138] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (ascorbic acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0139] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0140] 3) The graphene / carbon nanotube-coated tin powder was mixed with a vapor-phase carbon source (methane) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 50 seem. Vapor-phase coating was performed at 800°C for 40 minutes. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 10-20 nm and accounted for approximately 1 wt% of the double-coated sodium-ion battery anode material.

[0141] (2) Preparation of sodium ion battery, including the following steps:

[0142] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0143] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0144] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0145] Comparative Example 7 (Comparative Example 7 differs from Example 1 only in that the outer carbon coating layer is too thick)

[0146] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0147] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (ascorbic acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0148] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0149] 3) Mixing the graphene / carbon nanotube-coated tin powder with a vapor-phase carbon source (methane) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 300 seem and vapor-coating at 800°C for 5 hours. After vapor-coating, a carbon coating layer is formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer has a thickness of approximately 250-300 nm and constitutes approximately 10 wt% of the double-coated sodium-ion battery anode material.

[0150] (2) Preparation of sodium ion battery, including the following steps:

[0151] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0152] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0153] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0154] Comparative Example 8 (Comparative Example 8 differs from Example 1 only in that urea is used as soluble carbon)

[0155] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0156] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (urea) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0157] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0158] 3) The graphene / carbon nanotube-coated tin powder was mixed with a vapor-phase carbon source (methane) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 80 seem. Vapor-phase coating was performed at 800°C for 3 hours. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 90-110 nm and accounted for approximately 4 wt% of the double-coated sodium-ion battery anode material.

[0159] (2) Preparation of sodium ion battery, including the following steps:

[0160] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0161] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0162] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0163] Comparative Example 9 (Comparative Example 9 differs from Example 1 only in that acetone is used as the gaseous carbon source)

[0164] (1) Preparation of double-coated sodium ion battery negative electrode material, including the following steps:

[0165] 1) A tin source solution (tin chloride, concentration 0.35 mol / L), a graphene dispersion (concentration 1.25 wt%), a carbon nanotube dispersion (concentration 1.25 wt%), and soluble carbon (ascorbic acid) were uniformly mixed. The mixture was sprayed, dried, and sintered (1000°C, 10 h) in a reducing atmosphere (H2 / N2, with a hydrogen content of 2 wt%) to obtain graphene / carbon nanotube-coated tin powder agglomerates. The mass ratio of tin source solution, graphene dispersion, carbon nanotube dispersion, and soluble carbon was 1:0.02:0.02:2.5.

[0166] 2) The agglomerates are crushed to obtain graphene / carbon nanotube-coated tin powder with an average particle size of about 3 μm.

[0167] 3) The graphene / carbon nanotube-coated tin powder was mixed with a vapor-phase carbon source (acetone) under a heated protective atmosphere (argon) at a controlled inlet gas flow rate of 80 seem. Vapor-phase coating was performed at 800°C for 3 hours. After vapor-phase coating, a carbon coating layer was formed on the surface of the graphene / carbon nanotube-coated tin powder to obtain a double-coated sodium-ion battery anode material. The carbon coating layer had a thickness of approximately 90-110 nm and accounted for approximately 4 wt% of the double-coated sodium-ion battery anode material.

[0168] (2) Preparation of sodium ion battery, including the following steps:

[0169] S1. Prepare a positive electrode sheet: uniformly mix and disperse the sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, wherein the mass ratio of the sodium-based positive electrode active material, the binder, and the conductive agent is 95:3:2, to obtain a positive electrode slurry, which is coated on a positive electrode current collector to obtain a positive electrode sheet.

[0170] S2. Evenly mix and disperse the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent to obtain a negative electrode slurry, wherein the mass ratio of the double-coated sodium ion battery negative electrode material to the binder and the conductive agent is 96:3:1, and apply the slurry on the negative electrode current collector to obtain a negative electrode sheet.

[0171] S3. Wind or stack the positive electrode sheet, negative electrode sheet and separator to form a battery cell, bake to remove water, inject liquid and form a battery cell to make a sodium ion battery.

[0172] Performance testing:

[0173] The performance of the batteries obtained in the above embodiments and comparative examples was tested, and the results are shown in Table 1.

[0174] Table 1

[0175]

[0176] From the comparison of the data in the above table, we can see that:

[0177] Compared to Example 1, when the graphene and carbon nanotube content in Comparative Example 1 is too low, a line-surface conductive network cannot be formed, resulting in a decrease in the material's electronic conductivity, an increase in the battery's internal resistance, a decrease in rate capability, and a reduction in cycling performance. Conversely, when the graphene and carbon nanotube content in Comparative Example 2 is too high, the material's gram-specific capacity is reduced and material costs are increased.

[0178] Compared with Example 1, the particle size of the graphene / carbon nanotube-coated tin powder in Comparative Example 3 is too small, the chemical activity of the material is correspondingly enhanced, and the side reactions increase after contact with the electrolyte, affecting the cycle performance of the battery; on the contrary, the particle size of the graphene / carbon nanotube-coated tin powder in Comparative Example 4 is too large, the material contact area is reduced, the internal resistance is increased, and at the same time, the gram capacity of the material cannot be fully utilized.

[0179] Compared with Example 1, the negative electrode material in Comparative Example 5 has no outer carbon coating layer, and the insertion and extraction of sodium ions cause a large change in the material volume, the material structure is destroyed, and the cycle performance deteriorates.

[0180] Compared with Example 1, the outer carbon coating layer of the negative electrode material in Comparative Example 6 is thinner, and the volume change of the material during the cycle is insufficiently suppressed, affecting the cycle performance of the battery; while in Comparative Example 7, the thicker outer carbon coating layer increases the internal resistance of the electrode material, affects the embedding and extraction efficiency of sodium ions in the electrode material, resulting in an increase in the internal resistance of the battery, and both the rate performance and the cycle performance are affected.

[0181] Compared to Example 1, Comparative Examples 8 and 9 used other types of soluble carbon and gaseous carbon sources. The results showed that cycle performance, rate capability, internal resistance, and material specific capacity were all affected; this demonstrates that the type of soluble carbon and gaseous carbon source significantly influences material performance. The preferred soluble carbon and gaseous carbon sources of the present invention exhibited superior performance.

[0182] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0183] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a double-coated sodium ion battery negative electrode material, characterized in that include: 1) uniformly mixing a tin source solution, a graphene dispersion, a carbon nanotube dispersion, and soluble carbon, spraying, drying, and sintering in a reducing atmosphere to obtain graphene / carbon nanotube-coated tin powder agglomerates; the mass ratio of the tin source, graphene, carbon nanotubes, and soluble carbon is 1:(0.01-0.02):(0.01-0.02):(1.8-2.7); the tin source is a tin halide; and the soluble carbon is selected from glucose, citric acid, and ascorbic acid; 2) crushing the agglomerates to obtain graphene / carbon nanotube-coated tin powder with a particle size of 2 to 5 μm; 3) mixing the graphene / carbon nanotube-coated tin powder with a gaseous carbon source under a heated protective atmosphere to form a carbon coating layer after gas coating to obtain a double-coated sodium ion battery negative electrode material; the gaseous carbon source is selected from methane, ethylene, acetylene and benzene; and the carbon coating layer accounts for 2-6 wt% of the double-coated sodium ion battery negative electrode material.

2. The preparation method according to claim 1, wherein: In step 1), the concentration of the tin source solution is 0.2-0.5 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1), The concentration of the graphene dispersion is 0.5-2 wt %; The concentration of the carbon nanotube dispersion is 0.5-2 wt %.

4. The preparation method according to claim 1, wherein: In step 1), the sintering temperature is 800-1200° C. and the sintering time is 8-12 hours.

5. The preparation method according to claim 1 or 4, characterized in that: In step 1), the reducing atmosphere is a mixed gas of H2 and N2, wherein the mass proportion of hydrogen is 1-4 wt%.

6. The preparation method according to claim 1, wherein: In step 3), the protective atmosphere is selected from argon, nitrogen, helium, neon, krypton and xenon.

7. The preparation method according to claim 1 or 6, characterized in that: In step 3), the temperature of the gas phase coating is 700-900° C., and the time is 3-5 hours.

8. Use of the double-coated sodium ion battery negative electrode material obtained according to the preparation method according to any one of claims 1 to 7 in a sodium ion battery.

9. The use according to claim 8, characterized in that: The preparation method of the sodium ion battery comprises the following steps: S1, preparing a positive electrode sheet; S2. Evenly mix the double-coated sodium ion battery negative electrode material with a binder, a conductive agent, and a solvent, disperse the mixture, and obtain a negative electrode slurry, which is then coated on a negative electrode current collector to obtain a negative electrode sheet; S3. Assemble the positive electrode sheet, negative electrode sheet and separator into a battery cell, and then further make a sodium ion battery.

10. The use according to claim 9, characterized in that: S1 specifically comprises: uniformly mixing a sodium-based positive electrode active material with a binder, a conductive agent, and a solvent, dispersing the mixture to obtain a positive electrode slurry, and coating the mixture on a positive electrode current collector to obtain a positive electrode sheet; S3 specifically includes: winding or stacking the positive electrode sheet, negative electrode sheet and separator to assemble into a battery cell, baking to remove water, then injecting liquid and forming to make a sodium ion battery.

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