A sodium-ion battery anode sheet, a preparation method and application thereof

Abstract

The application relates to a sodium ion battery anode pole piece and a preparation method and application thereof. The preparation method of the sodium ion battery anode pole piece comprises the following steps: S1. providing a three-dimensional network structure carbon material composed of carbon nanofibers; S2. dispersing a molybdenum source, a sulfur source and the carbon material in deionized water, carrying out hydrothermal reaction, and then carrying out drying and calcination treatment to obtain a MoS2 / C composite material; S3. dispersing the MoS2 / C composite material, a binder and a conductive agent in deionized water according to a mass ratio to obtain a slurry; S4. uniformly coating the slurry on at least one surface of a negative electrode current collector, and drying to obtain a first negative electrode pole piece; and S5. preparing a TiO2 film layer on the first negative electrode pole piece to obtain the anode pole piece. The prepared sodium ion battery anode pole piece has good charge-discharge specific capacity and cycle life.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, specifically to a sodium-ion battery anode sheet, its preparation method, and its application. Background Technology

[0002] As demand continues to grow, the applications of lithium-ion batteries are expanding from portable electronic devices to wearable electronic devices, emerging electrical equipment, new energy electric vehicles, and smart grids. However, given the uneven geographical distribution of lithium resources, the low overall abundance of lithium reserves on Earth, and the high cost of applications in certain fields, developing new energy storage systems to replace lithium-ion batteries is of great significance. Since sodium resources are abundant globally, the refining technology is simple and convenient, and the energy storage mechanism is similar, sodium-ion batteries are a promising alternative to lithium-ion batteries.

[0003] Two-dimensional transition metal sulfides have become a research hotspot in sodium-ion battery anode materials due to their low cost and high theoretical specific capacity. Molybdenum disulfide nanosheets, with their unique sheet-like structure, have attracted considerable attention. However, when used alone as an electrode material, they are prone to stacking, leading to a reduction in the number of surface active sites and limiting the transport of fast ions. During sodium storage, the electrode material undergoes significant volume changes, affecting its overall structural stability and causing a rapid decline in electrochemical performance. To address the poor electronic conductivity and electrode structural stability of molybdenum disulfide, a three-dimensional network carbon substrate can be constructed. However, high specific surface area electrode materials are prone to numerous irreversible side reactions upon contact with the electrolyte, resulting in short cycle life and low initial coulombic efficiency. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a sodium-ion battery anode electrode, comprising a current collector, a MoS2 / C composite material layer disposed on at least one surface of the current collector, and a TiO2 thin film layer disposed on the side of the MoS2 / C composite material layer away from the current collector; the MoS2 / C composite material is molybdenum disulfide nanosheets supported on a carbon material with a three-dimensional network structure composed of carbon nanofibers. The prepared sodium-ion battery anode electrode exhibits good charge-discharge specific capacity and cycle life.

[0005] This invention is achieved through the following method:

[0006] The first objective of this invention is to provide a method for preparing a sodium-ion battery anode sheet, characterized by comprising the following steps:

[0007] S1. A carbon material with a three-dimensional network structure composed of carbon nanofibers is provided;

[0008] S2. Disperse the molybdenum source, sulfur source and the carbon material in deionized water, perform a hydrothermal reaction, and then dry and calcine to obtain the MoS2 / C composite material.

[0009] S3. Disperse the MoS2 / C composite material, binder, and conductive agent in deionized water according to the mass ratio to obtain a slurry;

[0010] S4. The slurry is uniformly coated on at least one surface of the negative electrode current collector and dried to obtain the first negative electrode sheet;

[0011] S5. Prepare a TiO2 thin film layer on the first negative electrode to obtain the anode electrode.

[0012] In one embodiment of the present invention, step S1 involves the preparation of a carbon material with a three-dimensional network structure composed of carbon nanofibers, comprising the following steps:

[0013] (1) A polymer nanofiber is provided;

[0014] (2) The polymer nanofibers and the adhesive are dispersed in a solvent according to the mass ratio to obtain a mixture;

[0015] (3) Freeze and crush the mixture to obtain crushed ice;

[0016] (4) Mix the crushed ice obtained in step (3) with the mixture obtained in step (2) according to the mass ratio, and freeze-dry to obtain a carbon material precursor;

[0017] (5) The carbon material precursor was calcined in an inert gas atmosphere to obtain a carbon material with a three-dimensional network structure composed of carbon nanofibers.

[0018] In one embodiment of the present invention, in step (1), the polymer is dispersed in an organic solvent to obtain a mixed solution, and the polymer nanofiber is prepared by spinning technology; the polymer is selected from one or more of polyacrylonitrile, polystyrene and polyvinylpyrrolidone; the organic solvent includes dimethylformamide; the mass ratio of the polymer to the organic solvent is 1:7 to 1:9.

[0019] In one embodiment of the present invention, the spinning technology is specifically solution blow spinning technology.

[0020] In one embodiment of the present invention, the needle used in the solution blowing technology is 30G, the propulsion speed of the mixed solution is 1.0-1.5ml / h, the airflow speed is 8-12m / s, and the distance between the nozzle and the left edge of the flat collection net is 25-40cm.

[0021] In one embodiment of the present invention, in step (2), the adhesive is selected from one or more of waterborne acrylic, waterborne polyurethane, waterborne epoxy resin, waterborne phenolic resin, waterborne silicone resin and polyvinyl acetate emulsion.

[0022] In one embodiment of the present invention, in step (2), the mass ratio of polymer nanofibers to adhesive is 1:5 to 1:10.

[0023] In one embodiment of the present invention, in step (2), the solvent is composed of deionized water and an alcohol solvent, wherein the alcohol solvent is selected from one or more of tert-butanol, methanol, ethanol and isopropanol; the mass ratio of deionized water to alcohol solvent is 3:1 to 6:1.

[0024] In one embodiment of the present invention, in step (3), the equipment used for freezing is a roller ice crusher with a crushing speed of 30 to 50 rad / min.

[0025] In one embodiment of the present invention, in step (3), the size of the crushed ice is 200-400 μm.

[0026] In one embodiment of the present invention, in step (4), the mass ratio of crushed ice to the mixture is 2:1 to 6:1.

[0027] In one embodiment of the present invention, in step (4), the freeze-drying temperature is -40℃ to -10℃ and the time is 12 to 36 hours.

[0028] In one embodiment of the present invention, in step (5), the inert gas is selected from one or more of nitrogen, argon and helium, and the inert gas flow rate is 40-80 mL / min; the heating rate of the calcination treatment is 0.5-5 °C / min, the temperature is 500-800 °C, and the time is 3-6 h.

[0029] In one embodiment of the present invention, in step S2, the molybdenum source is selected from one or more of sodium molybdate, ammonium molybdate tetrahydrate, and potassium molybdate; the sulfur source is selected from one or more of thiourea, thioacetamide, and sulfur powder; and the molar ratio of the molybdenum source to the sulfur source is 1:2 to 1:10.

[0030] In one embodiment of the present invention, in step S2, the hydrothermal reaction is carried out in a reaction vessel, and the temperature of the hydrothermal reaction is 160-200°C, and the time is 12-24 hours.

[0031] In one embodiment of the present invention, in step S2, the drying is carried out in a vacuum drying oven at a temperature of 60-80°C for a time of 12-24 hours.

[0032] In one embodiment of the present invention, in step S2, the heating rate of the calcination is 0.5-5℃ / min, the temperature is 500-800℃, and the time is 2-4h; the calcination is carried out in a tube furnace, and the atmosphere for calcination is an inert gas; the inert gas is one or more of nitrogen, argon, and helium, and the flow rate of the inert gas can be 40-80mL / min.

[0033] In one embodiment of the present invention, in step S3, the binder is selected from one or more of sodium alginate, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid, and sodium polyacrylate; the conductive agent is selected from one or more of conductive carbon black, carbon nanotubes, graphene, and carbon nanofibers. The conductive carbon black is selected from acetylene black and / or Ketjen black.

[0034] In one embodiment of the present invention, in step S3, the mass ratio of the MoS2 / C composite material, the binder, and the conductive agent is 7:1:2.

[0035] In one embodiment of the present invention, in step S4, the drying is carried out in a vacuum drying oven at a temperature of 100°C for a time of 6 hours.

[0036] In one embodiment of the present invention, in step S4, the loading of the first negative electrode is 0.8–1.1 mg / cm³. 2 .

[0037] In one embodiment of the present invention, in step S5, the TiO2 thin film layer is prepared by atomic deposition.

[0038] In one embodiment of the present invention, the atomic deposition temperature of the TiO2 thin film layer is 150°C, the titanium source is tetrakis(dimethylamino)titanium, the oxygen source is water, the pulse, purge and waiting processes of tetrakis(dimethylamino)titanium are 200ms, 25ms and 5s respectively, and the pulse, purge and waiting processes of water are 15ms, 30ms and 5s respectively. The inert carrier gas can be one or more of nitrogen, neon, argon, krypton and xenon.

[0039] The second objective of this invention is to provide a sodium-ion battery anode electrode, the sodium-ion battery anode electrode comprising a current collector, a MoS2 / C composite material layer disposed on at least one surface of the current collector, and a TiO2 thin film layer disposed on the side of the MoS2 / C composite material layer away from the current collector; the MoS2 / C composite material is molybdenum disulfide nanosheets supported on a carbon material with a three-dimensional network structure composed of carbon nanofibers.

[0040] In one embodiment of the present invention, the thickness of the MoS2 / C composite material layer is 80-200 μm, and the thickness of the TiO2 thin film layer is 1-10 nm.

[0041] A third objective of this invention is to provide a sodium-ion battery, including the aforementioned sodium-ion battery anode plate.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] The carbon material with a three-dimensional network structure composed of carbon nanofibers prepared using this application exhibits good structural stability and high reactive sites. Loading molybdenum disulfide onto this three-dimensional network structure solves the problems of easy stacking and poor electronic conductivity of molybdenum disulfide nanosheets, as well as the large specific surface area and susceptibility to side reactions with the electrolyte in the three-dimensional network structure carbon material, thereby improving the specific capacity and cycling performance of the composite material. Simultaneously, depositing a titanium dioxide layer on the electrode surface containing the molybdenum disulfide / carbon composite layer helps suppress the expansion of molybdenum disulfide, while also isolating the electrolyte and forming a stable SEI film, further improving cycling stability. Detailed Implementation

[0044] To address the technical problems mentioned in the background section, the inventors discovered that carbon materials with a three-dimensional network structure composed of carbon nanofibers possess excellent structural stability and high reactive sites. Loading molybdenum disulfide onto this three-dimensional network structure can solve the problems of easy stacking and poor electronic conductivity of molybdenum disulfide nanosheets, as well as the large specific surface area and susceptibility to side reactions with the electrolyte in three-dimensional network carbon materials, thereby improving the specific capacity and cycle performance of the composite material. Simultaneously, depositing a titanium dioxide layer on the electrode surface containing the molybdenum disulfide / carbon composite layer helps suppress the expansion of molybdenum disulfide, while also isolating the electrolyte and forming a stable SEI film, further improving cycle stability.

[0045] Specifically, the present invention provides a sodium-ion battery cathode material, which is achieved through the following method:

[0046] The first objective of this invention is to provide a method for preparing a sodium-ion battery anode sheet, characterized by comprising the following steps:

[0047] S1. A carbon material with a three-dimensional network structure composed of carbon nanofibers is provided;

[0048] Specifically, the preparation of a carbon material with a three-dimensional network structure composed of carbon nanofibers includes the following steps:

[0049] (1) A polymer nanofiber is provided;

[0050] Specifically, the polymer is dispersed in an organic solvent to obtain a mixed solution, and the polymer nanofibers are prepared by spinning technology; the polymer is selected from one or more of polyacrylonitrile, polystyrene and polyvinylpyrrolidone; the organic solvent includes dimethylformamide; the mass ratio of the polymer to the organic solvent is 1:7 to 1:9.

[0051] Specifically, the spinning technology can be electrospinning, solution blowing, meltblowing, and centrifugal spinning, with solution blowing being preferred.

[0052] Specifically, the solution blowing technology uses a 30G needle, the mixing solution propulsion speed is 1.0-1.5 ml / h, the airflow speed is 8-12 m / s, and the distance between the nozzle and the left edge of the flat collection net is 25-40 cm.

[0053] (2) The polymer nanofibers and the adhesive are dispersed in a solvent according to the mass ratio to obtain a mixture;

[0054] Specifically, the adhesive is selected from one or more of waterborne acrylic acid, waterborne polyurethane, waterborne epoxy resin, waterborne phenolic resin, waterborne silicone resin, and polyvinyl acetate emulsion. The adhesive is used for bonding between polymer nanofibers, and after carbonization, it acts as a linker between carbon nanofibers.

[0055] Specifically, the mass ratio of polymer nanofibers to adhesives is 1:5 to 1:10.

[0056] Specifically, the solvent is composed of deionized water and an alcohol solvent, wherein the alcohol solvent is selected from one or more of tert-butanol, methanol, ethanol, and isopropanol; the mass ratio of deionized water to alcohol solvent is 3:1 to 6:1.

[0057] (3) Freeze and crush the mixture to obtain crushed ice;

[0058] Specifically, the equipment used for freezing and crushing is a roller ice crusher with a crushing speed of 30–50 rad / min.

[0059] Specifically, the size of the crushed ice is 200–400 μm. The fiber length in the crushed ice is controlled to be 10–100 μm through crushing.

[0060] (4) Mix the crushed ice obtained in step (3) with the mixture obtained in step (2) according to the mass ratio, and freeze-dry to obtain a carbon material precursor;

[0061] Specifically, the mass ratio of crushed ice to the mixed liquid is 2:1 to 6:1. There are still gaps between the crushed ice, and the fibers cannot be well connected together. Mixing crushed ice with a mixed liquid containing polymer nanofibers can fill these gaps well. The fine fibers interconnect with the previous fibers, eliminating the fiber gaps and thus constructing a complete three-dimensional network structure of carbon material.

[0062] Specifically, in step (4), the freeze-drying temperature is -40℃ to -10℃ and the time is 12 to 36 hours.

[0063] (5) The carbon material precursor was calcined in an inert gas atmosphere to obtain a carbon material with a three-dimensional network structure composed of carbon nanofibers.

[0064] Specifically, the inert gas is selected from one or more of nitrogen, argon, and helium, and the inert gas flow rate is 40-80 mL / min; the heating rate of the calcination treatment is 0.5-5℃ / min, the temperature is 500-800℃, and the time is 3-6 h.

[0065] S2. Disperse the molybdenum source, sulfur source and the carbon material in deionized water, perform a hydrothermal reaction, and then dry and calcine to obtain the MoS2 / C composite material.

[0066] S3. Disperse the MoS2 / C composite material, binder, and conductive agent in deionized water according to the mass ratio to obtain a slurry;

[0067] S4. The slurry is uniformly coated on at least one surface of the negative electrode current collector and dried to obtain the first negative electrode sheet;

[0068] S5. Prepare a TiO2 thin film layer on the first negative electrode to obtain the anode electrode.

[0069] Specifically, in step S2, the molybdenum source is selected from one or more of sodium molybdate, ammonium molybdate tetrahydrate, and potassium molybdate; the sulfur source is selected from one or more of thiourea, thioacetamide, and sulfur powder; and the molar ratio of the molybdenum source to the sulfur source is 1:2 to 1:10.

[0070] Specifically, in step S2, the hydrothermal reaction is carried out in a reactor at a temperature of 160–200°C for a time of 12–24 hours.

[0071] Specifically, in step S2, the drying is carried out in a vacuum drying oven at a temperature of 60–80°C for 12–24 hours.

[0072] Specifically, in step S2, the heating rate of the calcination is 0.5-5℃ / min, the temperature is 500-800℃, and the time is 2-4h; the calcination is carried out in a tube furnace, and the atmosphere for calcination is an inert gas; the inert gas is one or more of nitrogen, argon, and helium, and the flow rate of the inert gas can be 40-80mL / min.

[0073] Specifically, in step S3, the binder is selected from one or more of sodium alginate, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, sodium carboxymethyl cellulose, polymethacrylamide, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyamide, polyimide, polyacrylate, styrene-butadiene rubber, chitosan, polyethylene glycol, and guar gum; the conductive agent is selected from one or more of conductive carbon black, carbon nanotubes, graphene, and carbon nanofibers. The conductive carbon black is selected from acetylene black and / or Ketjen black.

[0074] Specifically, in step S3, the mass ratio of the MoS2 / C composite material, binder, and conductive agent is 7:1:2.

[0075] Specifically, in step S4, the drying is carried out in a vacuum drying oven at a temperature of 100°C for 6 hours.

[0076] Specifically, in step S4, the loading of the first negative electrode is 0.8–1.1 mg / cm³. 2 .

[0077] Specifically, in step S5, the TiO2 thin film layer can be prepared by PVD (physical vapor deposition), CVD (chemical vapor deposition), or ALD (atomic layer deposition), preferably by atomic layer deposition.

[0078] Specifically, the atomic layer deposition temperature of the TiO2 thin film is 150℃, the titanium source is tetrakis(dimethylamino)titanium, the oxygen source is water, the pulse, purge and waiting processes of tetrakis(dimethylamino)titanium are 200ms, 25ms and 5s respectively, and the pulse, purge and waiting processes of water are 15ms, 30ms and 5s respectively. The inert carrier gas can be one or more of nitrogen, neon, argon, krypton and xenon.

[0079] This invention also provides a sodium-ion battery anode electrode, comprising a current collector, a MoS2 / C composite material layer disposed on at least one surface of the current collector, and a TiO2 thin film layer disposed on the side of the MoS2 / C composite material layer away from the current collector; the MoS2 / C composite material is molybdenum disulfide nanosheets loaded on a carbon material with a three-dimensional network structure composed of carbon nanofibers. Specifically, the molybdenum disulfide nanosheets are uniformly loaded on the surface of the carbon nanofibers constituting the three-dimensional network structure of the carbon material, thereby avoiding the accumulation of molybdenum disulfide nanosheets.

[0080] Specifically, the thickness of the MoS2 / C composite material layer is 80–200 μm, and the thickness of the TiO2 thin film layer is 1–10 nm.

[0081] The type of current collector is not specifically limited and can be selected according to actual needs. For example, the current collector can be copper foil, copper mesh or polymer conductive film. Preferably, the current collector is copper foil.

[0082] The present invention also provides a sodium-ion battery, comprising the above-described sodium-ion battery anode plate, cathode plate, separator, and electrolyte, wherein the separator is configured to isolate the anode plate from the cathode plate.

[0083] In the aforementioned sodium-ion batteries, the type of separator is not specifically limited and can be any separator material used in existing batteries, such as polyethylene, polypropylene, polyvinylidene fluoride, non-woven fabric, their multilayer composite membranes, and modified separators such as ceramic modification and PVDF modification, but not limited to these.

[0084] In the aforementioned sodium-ion battery, the electrolyte can be one or more of the following: organic liquid electrolyte, organic solid electrolyte, solid ceramic electrolyte, and gel electrolyte. Preferably, the electrolyte is an organic liquid electrolyte, which is obtained by dissolving a sodium salt in a non-aqueous organic solvent; wherein the sodium salt may include one or more of sodium difluorophosphate (NaPO2F2), sodium hexafluorophosphate (NaPF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSi), and sodium difluorooxalate borate (NaDFOB). The aforementioned non-aqueous organic solvent may include one or more of cyclic carbonates, chain carbonates, and carboxylic acid esters. Cyclic carbonates may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), butenyl carbonate, and γ-butyrolactone; chain carbonates may be selected from one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), methyl acetate (MA), ethyl acetate (EA), and ethyl propionate (EP).

[0085] In some embodiments, a certain amount of additives may be added to the organic liquid electrolyte. The additives may include one or more of the following: vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), vinyl sulfite (ES), methylene disulfonate (MMDS), 1,3-propanesulfonate lactone (PS), propylene sulfonate lactone (PES), propylene sulfate (TMS), trimethylsilane phosphate (TMSP), trimethylsilane borate (TMSB), and fluoroethylene carbonate (FEC).

[0086] The present invention further provides an electrical device, including the sodium-ion battery described above.

[0087] In some embodiments, the electrical equipment of the present invention includes, but is not limited to, backup power supplies, motors, electric vehicles, electric motorcycles, electric bicycles, bicycles, power tools, and large household batteries.

[0088] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0089] Example 1

[0090] (1) 6g of polyacrylonitrile powder (Mw = 260000) was dissolved in 44g of DMF to obtain a mixed solution. Polyacrylonitrile nanofibers were prepared using the industrial SBS method with a 30G needle, a polymer solution propulsion speed of 1.0ml / h, an airflow speed of 12m / s, and a distance of 40cm between the nozzle and the left edge of the flat collection net. The prepared nanofibers were then dispersed in deionized water / tert-butanol (mass ratio 4:1) using aqueous polyurethane as a binder. The total amounts of PAN nanofibers and WPU were 0.6wt% and 0.3wt%, respectively, to obtain a uniform nanofiber dispersion solution. The nanofiber dispersion solution was then frozen on the surface of a rotating low-temperature roller at -20°C using a roller ice crusher with a rotation speed of 50rad / min, rapidly converting the nanofiber dispersion solution into nanofiber crushed ice. Finally, the nanofiber crushed ice and the nanofiber dispersion solution were mixed at a mass ratio of 4:1 to fill the gaps between the crushed ice, transferred to a mold, and then the mixture was placed in a low-temperature environment and recast into ice blocks. Next, the material was freeze-dried for 24 hours, then calcined at 500 degrees Celsius under a nitrogen atmosphere at a heating rate of 5 degrees Celsius per minute to obtain a carbon nanofiber aerogel material with a three-dimensional network structure, designated as material No. 1.

[0091] (2) Disperse sodium molybdate, thiourea, and the above-mentioned material No. 1 into 50 mL of deionized water. Then pour the mixed solution into a 100 mL high-pressure reactor. The hydrothermal temperature is 180 °C, and the time is 12 hours. The material obtained after hydrothermal treatment is washed three times with deionized water and anhydrous ethanol, and then placed in a vacuum drying oven at 60 °C for 12 hours. After drying, the material is placed in a tube furnace under a nitrogen atmosphere for calcination. The heating rate is 5 °C per minute, and the calcination temperature is 600 °C. The material is named MoS2 / C and designated as material No. 2.

[0092] (3) A water-based slurry prepared from MoS2 / C, sodium alginate, and acetylene black in a weight ratio of 7:1:2 was uniformly coated onto copper foil to obtain a MoS2 / C electrode. The electrode was then dried in a vacuum oven at 80°C for 12 hours, resulting in an electrode loading of approximately 0.8 mg / cm³. 2 .

[0093] (4) TiO2 layers were deposited at 150°C using tetra(dimethylamino)titanium and water as the titanium and oxygen sources, respectively. The pulse, purge, and wait times for tetra(dimethylamino)titanium were 200 ms, 25 ms, and 5 s, respectively, while those for water were 15 ms, 30 ms, and 5 s, respectively. The inert carrier gas could be nitrogen, neon, argon, krypton, xenon, etc. Atomic layer deposition was performed on the MoS2 / C electrode, resulting in a high-performance TiO2-MoS2 / C sodium-ion battery anode.

[0094] Example 2

[0095] (1) 6g of polyacrylonitrile powder (Mw = 2,600,000) was dissolved in 44g of DMF to obtain a mixed solution. Polyacrylonitrile nanofibers were prepared using the industrial SBS method with a 30G needle, a polymer solution propulsion speed of 1.2ml / h, an airflow speed of 10m / s, and a distance of 30cm between the nozzle and the left edge of the flat collection net. The prepared nanofibers were then dispersed in deionized water / tert-butanol (mass ratio 5:1) using aqueous polyurethane as a binder. The total amounts of PAN nanofibers and WPU were 0.5wt% and 0.35wt%, respectively, to obtain a uniform nanofiber dispersion solution. The nanofiber dispersion solution was then frozen on the surface of a rotating low-temperature roller at -20°C using a roller ice crusher with a rotation speed of 50rad / min, rapidly converting the nanofiber dispersion solution into nanofiber crushed ice. Finally, the nanofiber crushed ice and the nanofiber dispersion solution were mixed at a mass ratio of 5:1 to fill the gaps between the crushed ice, transferred to a mold, and then the mixture was placed in a low-temperature environment and recast into ice blocks. Next, the material was freeze-dried for 24 hours, then calcined at 600 degrees Celsius under a nitrogen atmosphere at a heating rate of 5 degrees Celsius per minute to obtain a carbon nanofiber aerogel material with a three-dimensional network structure, designated as material No. 1.

[0096] (2) Disperse sodium molybdate, thiourea, and the above-mentioned material No. 1 into 50 mL of deionized water. Then pour the mixed solution into a 100 mL high-pressure reactor. The hydrothermal temperature is 200 °C, and the time is 18 hours. The material obtained after hydrothermal treatment is washed three times with deionized water and anhydrous ethanol, and then placed in a vacuum drying oven at 60 °C for 12 hours. After drying, the material is placed in a tube furnace under a nitrogen atmosphere for calcination. The heating rate is 5 °C per minute, and the calcination temperature is 600 °C. The material is named MoS2 / C and designated as material No. 2.

[0097] (3) A water-based slurry prepared from MoS2 / C, sodium alginate, and acetylene black in a weight ratio of 7:1:2 was uniformly coated onto copper foil to obtain a MoS2 / C electrode. The electrode was then dried in a vacuum oven at 80°C for 12 hours, resulting in an electrode loading of approximately 1.0 mg / cm³. 2 .

[0098] (4) TiO2 layers were deposited at 150°C using tetra(dimethylamino)titanium and water as the titanium and oxygen sources, respectively. The pulse, purge, and wait times for tetra(dimethylamino)titanium were 200 ms, 25 ms, and 5 s, respectively, while those for water were 15 ms, 30 ms, and 5 s, respectively. The inert carrier gas could be nitrogen, neon, argon, krypton, xenon, etc. Atomic layer deposition was performed on the MoS2 / C electrode, resulting in a high-performance TiO2-MoS2 / C sodium-ion battery anode.

[0099] Example 3

[0100] (1) 6g of polyacrylonitrile powder (Mw = 2,600,000) was dissolved in 44g of DMF to obtain a mixed solution. Polyacrylonitrile nanofibers were prepared using the industrial SBS method with a 30G needle, a polymer solution propulsion speed of 1.1ml / h, an airflow speed of 10m / s, and a distance of 30cm between the nozzle and the left edge of the flat collection net. The prepared nanofibers were then dispersed in deionized water / tert-butanol (mass ratio 5:1) using aqueous polyurethane as a binder. The total amounts of PAN nanofibers and WPU were 0.5wt% and 0.35wt%, respectively, to obtain a uniform nanofiber dispersion solution. The nanofiber dispersion solution was then frozen on the surface of a rotating low-temperature roller in a roller ice-making machine at -20°C with a rotation speed of 50rad / min, rapidly converting the nanofiber dispersion solution into nanofiber crushed ice. Finally, the nanofiber crushed ice and the nanofiber dispersion solution were mixed at a mass ratio of 5:1 to fill the gaps between the crushed ice, transferred to a mold, and then the mixture was placed in a low-temperature environment and recast into ice blocks. Next, the material was freeze-dried for 24 hours, then calcined at 600 degrees Celsius under a nitrogen atmosphere at a heating rate of 5 degrees Celsius per minute to obtain a carbon nanofiber aerogel material with a three-dimensional network structure, designated as material No. 1.

[0101] (2) Disperse sodium molybdate, thiourea, and the above-mentioned material No. 1 into 50 mL of deionized water. Then pour the mixed solution into a 100 mL high-pressure reactor. The hydrothermal temperature is 180 °C, and the time is 18 hours. The material obtained after hydrothermal treatment is washed three times with deionized water and anhydrous ethanol, and then placed in a vacuum drying oven at 60 °C for 12 hours. After drying, the material is placed in a tube furnace under a nitrogen atmosphere for calcination. The heating rate is 5 °C per minute, and the calcination temperature is 600 °C. The material is named MoS2 / C and designated as material No. 2.

[0102] (3) A water-based slurry prepared from MoS2 / C, sodium alginate, and acetylene black in a weight ratio of 7:1:2 was uniformly coated onto copper foil to obtain a MoS2 / C electrode. The electrode was then dried in a vacuum oven at 80°C for 12 hours, resulting in an electrode loading of approximately 1.0 mg / cm³. 2 .

[0103] (4) TiO2 layers were deposited at 150°C using tetra(dimethylamino)titanium and water as the titanium and oxygen sources, respectively. The pulse, purge, and wait times for tetra(dimethylamino)titanium were 200 ms, 25 ms, and 5 s, respectively, while those for water were 15 ms, 30 ms, and 5 s, respectively. The inert carrier gas could be nitrogen, neon, argon, krypton, xenon, etc. Atomic layer deposition was performed on the MoS2 / C electrode, resulting in a high-performance TiO2-MoS2 / C sodium-ion battery anode.

[0104] Example 4

[0105] (1) 6g of polyacrylonitrile powder (Mw = 2,600,000) was dissolved in 44g of DMF to obtain a mixed solution. Polyacrylonitrile nanofibers were prepared using the industrial SBS method with a 30G needle, a polymer solution propulsion speed of 1.0ml / h, an airflow speed of 8m / s, and a distance of 25cm between the nozzle and the left edge of the flat collection net. The prepared nanofibers were then dispersed in deionized water / tert-butanol (mass ratio 5:1) using aqueous polyurethane as a binder. The total amounts of PAN nanofibers and WPU were 0.5wt% and 0.30wt%, respectively, to obtain a uniform nanofiber dispersion solution. The nanofiber dispersion solution was then frozen on the surface of a rotating low-temperature roller at -20°C using a roller ice crusher with a rotation speed of 50rad / min, rapidly converting the nanofiber dispersion solution into nanofiber crushed ice. Finally, the nanofiber crushed ice and the nanofiber dispersion solution were mixed at a mass ratio of 5:1, filling the gaps between the crushed ice, and transferred to a mold. The mixture was then placed in a low-temperature environment and recast into ice blocks. Next, the material was freeze-dried for 24 hours, then calcined at 600 degrees Celsius under a nitrogen atmosphere at a heating rate of 5 degrees Celsius per minute to obtain a carbon nanofiber aerogel material with a three-dimensional network structure, designated as material No. 1.

[0106] (2) Disperse sodium molybdate, thiourea, and the above-mentioned material No. 1 into 50 mL of deionized water. Then pour the mixed solution into a 100 mL high-pressure reactor. The hydrothermal temperature is 200 °C, and the time is 18 hours. The material obtained after hydrothermal treatment is washed three times with deionized water and anhydrous ethanol, and then placed in a vacuum drying oven at 60 °C for 12 hours. After drying, the material is placed in a tube furnace under a nitrogen atmosphere for calcination. The heating rate is 5 °C per minute, and the calcination temperature is 600 °C. The material is named MoS2 / C and designated as material No. 2.

[0107] (3) A water-based slurry prepared from MoS2 / C, sodium alginate, and acetylene black in a weight ratio of 7:1:2 was uniformly coated onto copper foil to obtain a MoS2 / C electrode. The electrode was then dried in a vacuum oven at 80°C for 12 hours, resulting in an electrode loading of approximately 1.0 mg / cm³. 2 .

[0108] (4) TiO2 layers were deposited at 150°C using tetra(dimethylamino)titanium and water as the titanium and oxygen sources, respectively. The pulse, purge, and wait times for tetra(dimethylamino)titanium were 200 ms, 25 ms, and 5 s, respectively, while those for water were 15 ms, 30 ms, and 5 s, respectively. The inert carrier gas could be nitrogen, neon, argon, krypton, xenon, etc. Atomic layer deposition was performed on the MoS2 / C electrode, resulting in a high-performance TiO2-MoS2 / C sodium-ion battery anode.

[0109] Comparative Example 1

[0110] This comparative example includes the following specific steps:

[0111] (1) 6g of polyacrylonitrile powder (Mw = 2,600,000) was dissolved in 44g of DMF to obtain a mixed solution. Polyacrylonitrile nanofibers were prepared using the industrial SBS method with a 30G needle, a polymer solution propulsion speed of 1.0ml / h, an airflow speed of 8m / s, and a distance of 25cm between the nozzle and the left edge of the flat collection net. The prepared nanofibers were then dispersed in deionized water / tert-butanol (mass ratio 5:1) using aqueous polyurethane as a binder. The total amounts of PAN nanofibers and WPU were 0.5wt% and 0.30wt%, respectively, to obtain a uniform nanofiber dispersion solution. The nanofiber dispersion solution was then frozen on the surface of a rotating low-temperature roller at -20°C using a roller ice crusher with a rotation speed of 50rad / min, rapidly converting the nanofiber dispersion solution into nanofiber crushed ice. Finally, the nanofiber crushed ice and the nanofiber dispersion solution were mixed at a mass ratio of 5:1, filling the gaps between the crushed ice, and transferred to a mold. The mixture was then placed in a low-temperature environment and recast into ice blocks. Next, the material was freeze-dried for 24 hours, then calcined at 600 degrees Celsius under a nitrogen atmosphere at a heating rate of 5 degrees Celsius per minute to obtain a carbon material with a three-dimensional network structure.

[0112] (2) An electrode was prepared by uniformly coating a water-based slurry containing carbon material with a three-dimensional network structure, sodium alginate, and acetylene black in a weight ratio of 7:1:2 onto a copper foil. The electrode was then dried in a vacuum oven at 80 degrees Celsius for 12 hours, resulting in an electrode loading of approximately 1.0 mg / cm³. 2 A sodium-ion battery anode was obtained.

[0113] Comparative Example 2

[0114] This comparative example includes the following specific steps:

[0115] (1) Place 3.1 mg sodium molybdate and 2.5 mg thiourea in 50 ml of deionized water to prepare a solvothermal reaction solution.

[0116] (2) Place the mixed solution in an oven and set the solvothermal reaction conditions to 180°C for 10 hours.

[0117] (3) After natural cooling, molybdenum disulfide nanosheet sodium-ion battery anode material is obtained by washing, filtering and drying.

[0118] (4) A water-based slurry prepared by molybdenum disulfide nanosheet sodium-ion battery anode material, sodium alginate, and acetylene black in a weight ratio of 7:1:2 was uniformly coated onto copper foil to obtain an electrode. The electrode was then dried in a vacuum oven at 80 degrees Celsius for 12 hours, and the electrode loading was approximately 1.0 mg / cm³. 2 A MoS2 sodium-ion battery anode was obtained.

[0119] Comparative Example 3

[0120] This comparative example includes the following specific steps:

[0121] (1) Disperse 3.1 mg sodium molybdate and 2.5 mg thiourea in 50 mL of deionized water, then pour the mixture into a 100 mL high-pressure reactor. The hydrothermal temperature is 200 °C and the time is 18 hours. The material obtained after hydrothermal treatment is washed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60 °C for 12 hours.

[0122] (2) A water-based slurry prepared by MoS2, sodium alginate, and acetylene black in a weight ratio of 7:1:2 was uniformly coated onto copper foil to obtain a MoS2 electrode. The electrode was then dried in a vacuum oven at 80 degrees Celsius for 12 hours, and the electrode loading was approximately 1.0 mg / cm³. 2 .

[0123] (3) TiO2 layers were deposited at 150°C using tetra(dimethylamino)titanium and water as the titanium and oxygen sources, respectively. The pulse, purge, and wait times for tetra(dimethylamino)titanium were 200 ms, 25 ms, and 5 s, respectively, while those for water were 15 ms, 30 ms, and 5 s, respectively. The inert carrier gas could be nitrogen, neon, argon, krypton, xenon, etc. Atomic layer deposition was performed on the MoS2 electrode, resulting in a high-performance TiO2-MoS2 sodium-ion battery anode.

[0124] Comparative Example 4

[0125] This comparative example includes the following specific steps:

[0126] (1) 6g of polyacrylonitrile powder (Mw = 2,600,000) was dissolved in 44g of DMF to obtain a mixed solution. Polyacrylonitrile nanofibers were prepared using the industrial SBS method with a 30G needle, a polymer solution propulsion speed of 1.0ml / h, an airflow speed of 8m / s, and a distance of 25cm between the nozzle and the left edge of the flat collection net. The prepared nanofibers were then dispersed in deionized water / tert-butanol (mass ratio 5:1) using aqueous polyurethane as a binder. The total amounts of PAN nanofibers and WPU were 0.5wt% and 0.30wt%, respectively, to obtain a uniform nanofiber dispersion solution. The nanofiber dispersion solution was then frozen on the surface of a rotating low-temperature roller at -20°C using a roller ice crusher with a rotation speed of 50rad / min, rapidly converting the nanofiber dispersion solution into nanofiber crushed ice. Finally, the nanofiber crushed ice and the nanofiber dispersion solution were mixed at a mass ratio of 5:1, filling the gaps between the crushed ice, and transferred to a mold. The mixture was then placed in a low-temperature environment and recast into ice blocks. Next, the material was freeze-dried for 24 hours, then calcined at 600 degrees Celsius under a nitrogen atmosphere at a heating rate of 5 degrees Celsius per minute to obtain a carbon material with a three-dimensional network structure, denoted as CNF.

[0127] (2) A water-based slurry prepared by CNF, sodium alginate, and acetylene black in a weight ratio of 7:1:2 was uniformly coated onto copper foil to obtain a CNF electrode. The electrode was then dried in a vacuum oven at 80 degrees Celsius for 12 hours, and the electrode loading was approximately 1.0 mg / cm³. 2 .

[0128] (3) TiO2 layers were deposited at 150°C using tetra(dimethylamino)titanium and water as the titanium and oxygen sources, respectively. The pulse, purge, and wait times for tetra(dimethylamino)titanium were 200 ms, 25 ms, and 5 s, respectively, while those for water were 15 ms, 30 ms, and 5 s, respectively. The inert carrier gas could be nitrogen, neon, argon, krypton, xenon, etc. Atomic layer deposition was performed on the CNF electrode, resulting in a high-performance TiO2-CNF sodium-ion battery anode.

[0129] Button assembly:

[0130] Using the sodium-ion battery anode sheets prepared in Examples 1-4 and Comparative Examples 1-4 as the negative electrode and the metallic sodium sheet as the positive electrode, and 1.0 mol / L NaPF6 dissolved in diethylene glycol dimethyl ether as the electrolyte, CR2032 button batteries were assembled in an argon glove box.

[0131] Performance testing:

[0132] The button batteries prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to constant current charge-discharge tests at a current density of 50 mA / g, with a voltage range of 0-2V. The initial discharge capacity and initial coulombic efficiency were recorded. After 500 cycles, the capacity retention rate after 500 cycles was calculated. The specific values ​​are shown in Table 1.

[0133] Table 1. Electrochemical performance test results of Examples 1-4 and Comparative Examples 1-4

[0134]

[0135]

[0136] The content of this invention is not limited to the above examples; a combination of one or more examples can also achieve the purpose of this invention.

[0137] The various embodiments in this specification are described in a progressive manner, with each example focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The methods disclosed in the embodiments are described simply because they correspond to the methods disclosed in the embodiments; relevant parts can be found in the method section.

[0138] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a sodium-ion battery anode sheet, characterized in that, Includes the following steps: S1. A carbon material with a three-dimensional network structure composed of carbon nanofibers is provided, the preparation of which includes the following steps: (1) A polymer nanofiber is provided; a polymer is dispersed in an organic solvent to obtain a mixed solution, and the polymer nanofiber is prepared by spinning technology; the polymer is selected from one or more of polyacrylonitrile, polystyrene and polyvinylpyrrolidone; the organic solvent includes dimethylformamide; the mass ratio of the polymer to the organic solvent is 1:7 to 1:9; (2) A mixture is obtained by dispersing polymer nanofibers and adhesives in a solvent according to a mass ratio; the adhesive is selected from one or more of waterborne acrylic acid, waterborne polyurethane, waterborne epoxy resin, waterborne phenolic resin, waterborne silicone resin and polyvinyl acetate emulsion; the mass ratio of polymer nanofibers to adhesives is 1:5 to 1:10; the solvent is composed of deionized water and alcohol solvents, the alcohol solvents are selected from one or more of tert-butanol, methanol, ethanol and isopropanol; the mass ratio of deionized water to alcohol solvents is 3:1 to 6:1; (3) Freeze and crush the mixture to obtain crushed ice; (4) Mix the crushed ice obtained in step (3) with the mixture obtained in step (2) according to the mass ratio, and freeze-dry to obtain the carbon material precursor; (5) The carbon material precursor was calcined in an inert gas atmosphere to obtain a carbon material with a three-dimensional network structure composed of carbon nanofibers. S2. Disperse the molybdenum source, sulfur source and the carbon material in deionized water, perform a hydrothermal reaction, and then dry and calcine to obtain the MoS2 / C composite material. S3. Disperse the MoS2 / C composite material, binder, and conductive agent in deionized water according to the mass ratio to obtain a slurry; S4. The slurry is uniformly coated on at least one surface of the negative electrode current collector and dried to obtain the first negative electrode sheet; S5. Prepare a TiO2 thin film layer on the first negative electrode to obtain the anode electrode.

2. The method for preparing a sodium-ion battery anode sheet according to claim 1, characterized in that, At least one of the following characteristics must be met: In step (3), the size of the ice fragments is 200~400μm; In step (4), the mass ratio of crushed ice to the mixed liquid is 2:1 to 6:1; In step (5), the inert gas is selected from one or more of nitrogen, argon, and helium, and the inert gas flow rate is 40~80mL / min; the heating rate of the calcination treatment is 0.5~5℃ / min, the temperature is 500~800℃, and the time is 3~6h.

3. The method for preparing a sodium-ion battery anode sheet according to claim 1, characterized in that, In step S2, the molybdenum source is selected from one or more of sodium molybdate, ammonium molybdate tetrahydrate, and potassium molybdate, and the sulfur source is selected from one or more of thiourea, thioacetamide, and sulfur powder. The molar ratio of the molybdenum source to the sulfur source is 1:2 to 1:

10. The hydrothermal reaction is carried out at a temperature of 160~200℃ for a time of 12~24h. The drying temperature is 60~80℃, and the time is 12~24h; The calcination process involves a heating rate of 0.5~5℃ / min, a temperature of 500~800℃, and a time of 2~4h.

4. The method for preparing a sodium-ion battery anode sheet according to claim 1, characterized in that, At least one of the following characteristics must be met: In step S3, the binder is selected from one or more of sodium alginate, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid and sodium polyacrylate, and the conductive agent is selected from one or more of conductive carbon black, carbon nanotubes, graphene and carbon nanofibers. The mass ratio of MoS2 / C composite material, binder and conductive agent is 7:1:

2. In step S4, the loading of the first negative electrode is 0.8~1.1 mg / cm³. 2 ; In step S5, the TiO2 thin film layer is prepared by atomic deposition.

5. A sodium-ion battery anode electrode obtained by the preparation method according to any one of claims 1 to 4, characterized in that, It includes a current collector, a MoS2 / C composite material layer disposed on at least one surface of the current collector, and a TiO2 thin film layer disposed on the side of the MoS2 / C composite material layer away from the current collector; the MoS2 / C composite material is molybdenum disulfide nanosheets supported on a carbon material with a three-dimensional network structure composed of carbon nanofibers.

6. The sodium-ion battery anode sheet according to claim 5, characterized in that, The thickness of the MoS2 / C composite material layer is 80~200μm, and the thickness of the TiO2 thin film layer is 1~10nm.

7. A sodium-ion battery, characterized in that, Includes the sodium-ion battery anode sheet as described in claim 5 or 6.

Images