Two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material, preparation method and application thereof

Abstract

The application relates to a two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material and a preparation method and application thereof. The composite electrode material has a two-dimensional layered structure, a particle size of 2-30 mu m, and a thickness of 8-12 nm. The composite electrode material is composed of internal few-layer reduced graphene oxide, an outer layer of ultrathin sodium titanate nanosheet, and nitrogen-doped carbon coated on the surface of the ultrathin sodium titanate nanosheet. Compared with the prior art, the preparation process is simple, easy to scale up, and controllable. The pore size, specific surface area and mesostructure of the obtained material can be adjusted. The sodium-ion battery or sodium battery containing the material has the advantages of high energy density and power density, and shows a broad market application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion battery electrode materials, in particular to a two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material and a preparation method and application thereof. BACKGROUND

[0002] Sodium ion batteries have the advantages of abundant resources and low cost, and highlight the huge natural potential in application fields such as large-scale energy storage and smart grids. However, the energy density, power density and long cycle stability still need to be further improved.

[0003] The negative electrode material plays a crucial role in the energy density and stability of the battery. The most ideal negative electrode material should have a low discharge voltage and a high theoretical capacity. At the same time, the first coulomb efficiency, power characteristics and cycle stability are also important performance indicators. Titanium-based negative electrode materials have attracted great interest due to their efficient sodium storage activity, high stability, low cost and non-toxicity. Among them, Na2Ti3O7 has a high theoretical capacity (310 mAh g -1 ) and a low discharge voltage platform (0.3 V vs Na / Na + ), which can produce higher working voltage and energy density in actual batteries. However, due to the large band gap (3.7 eV) of the Na2Ti3O7 material itself, it has slow sodium ion insertion / extraction dynamics, in addition, the large amount of sodium insertion in the Na2Ti3O7 lattice causes serious structural strain and exposes more reactive surface sites, resulting in continuous decomposition of the electrolyte and low first coulomb efficiency, thus showing poor cycle stability.

[0004] Currently, there are literatures that mainly solve the above problems through the design of nanoparticle structure (Adv. Mater. 2017, 29, 1700989), surface doping (Adv. Energy Mater. 2016, 6, 1502568) and the like, but materials that simultaneously consider the ion transport improvement of the bulk phase and the interface modification are still rarely reported. SUMMARY

[0005] The purpose of the present application is to provide a two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material and a preparation method and application thereof.

[0006] The purpose of the present application can be achieved by the following technical scheme: a two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material has a two-dimensional layered structure, the particle size is 2-30 mu m, the thickness is 8-12 nm, and is composed of an internal few-layer reduced graphene oxide, an outer ultrathin sodium titanate nanosheet and nitrogen-doped carbon coated on the surface of the ultrathin sodium titanate nanosheet.

[0007] Preferably, in the composite electrode material, the total mass of the few-layer reduced graphene oxide and carbon is 25%-30% of the mass of the composite electrode material.

[0008] The two-dimensional ultrathin sodium titanate nanosheet / carbon composite material provided by the application is prepared by using few-layer reduced graphene oxide as a template, uniformly loading monolayer mesoporous titanium dioxide, and then hydrothermally treating in an alkaline solution containing dopamine. The material has a two-dimensional layered structure, a particle size of 2-30 μm, and a thickness of about 10 nm. The material is composed of internal few-layer reduced graphene oxide, external ultrathin sodium titanate nanosheets, and nitrogen-doped carbon coated on the surface of the ultrathin sodium titanate nanosheets.

[0009] The composite electrode material is prepared by synthesizing monolayer mesoporous titanium oxide by a single micelle method, loading the monolayer mesoporous titanium oxide on few-layer reduced graphene oxide to form a precursor, and then mixing the precursor with dopamine and treating the mixture in an alkaline solution in one step.

[0010] A preparation method of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material, comprising the following steps:

[0011] (1) Synthesizing a precursor by a single micelle self-assembly method: adding a surfactant catalyst and a complexing agent into an organic solvent, stirring vigorously, then adding a titanium source, drying the solvent to obtain a titanium dioxide single micelle gel, dispersing the gel in an organic solvent to form a transparent solution, then adding few-layer reduced graphene oxide (rGO) into the mixture, heating in an oil bath, collecting black precipitates and drying, and finally calcining to obtain an rGO / TiO2 composite precursor;

[0012] (2) Preparing the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material by a hydrothermal treatment method: mixing the precursor obtained in step (1) with dopamine in an aqueous solution, then adding the mixture into an alkaline solution, and then hydrothermally treating in a reaction kettle, washing, and calcining at a high temperature to obtain the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material.

[0013] Preferably, in step (1), the surfactant is a non-ionic surfactant.

[0014] Further preferably, the surfactant is one or more of polyethylene oxide-polypropylene oxide, polyethylene oxide-polybutylene oxide, polyethylene oxide-polystyrene, or polyethylene oxide-poly(methyl methacrylate) diblock copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, or polypropylene oxide-polyethylene oxide-polypropylene oxide triblock copolymer.

[0015] Preferably, in step (1), the titanium source is one or more of titanium sulfate, titanium tert-butoxide, titanium methoxide, titanium tetrachloride, tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, or titanium acetylacetonate.

[0016] Preferably, in step (1), the catalyst is one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid or phosphoric acid.

[0017] Preferably, in step (1), the complexing agent is one or more of acetic acid, citric acid, acetylacetone or ethylenediaminetetraacetic acid.

[0018] Preferably, in step (1), the organic solvent is one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, benzene, toluene, diethyl ether, tetrahydrofuran, chloroform or dichloromethane.

[0019] Preferably, in step (2), the molar ratio of the rGO / TiO2 composite precursor to dopamine is (1-20):(0.01-1).

[0020] Preferably, in step (2), the molar ratio of the rGO / TiO2 composite precursor to base is (1-20):(0.01-1).

[0021] Preferably, step (2) is calcined in an inert atmosphere, and the calcination process is to heat to 300-800℃ at a heating rate of 1-5℃ / min, and keep constant temperature for 0.5-3h.

[0022] Further preferably, the inert atmosphere is nitrogen or argon.

[0023] An application of the above-mentioned two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material, the composite electrode material is used for preparing a sodium ion battery or a sodium battery.

[0024] Preferably, the two-dimensional ultrathin sodium titanate nanosheet / carbon composite material is used as a negative electrode of a sodium ion battery or a positive electrode of a sodium battery.

[0025] Preferably, the sodium ion battery and the sodium battery are room-temperature rechargeable sodium / sodium ion batteries, which comprise a positive electrode sheet, a negative electrode sheet, an electrolyte, a separator and a shell, the separator is a glass fiber separator, a polyethylene microporous membrane, a polypropylene microporous membrane or a composite separator thereof, and the electrolyte is a soluble sodium salt organic solution; in the sodium ion battery, the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material is a negative electrode, and a sodium ion embeddable / detachable active material is used as a positive electrode; in the sodium battery, the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material is a positive electrode, and metallic sodium is used as a negative electrode.

[0026] Further preferably, the sodium battery positive electrode sheet is obtained by coating the slurry obtained by uniformly mixing the positive electrode material, the conductive agent, the binder and the dispersant onto the current collector, and the current collector is copper foil; the sodium ion battery negative electrode sheet is obtained by coating the slurry obtained by uniformly mixing the negative electrode material, the conductive agent, the binder and the dispersant onto the current collector, and the positive electrode sheet is obtained by coating the slurry obtained by uniformly mixing the positive electrode material, the conductive agent, the binder and the dispersant onto the current collector, and the current collector is aluminum foil.

[0027] Further preferably, in the sodium ion battery and the sodium battery, the conductive agent is one or more of acetylene black, Super P or graphite; the binder is one or more of polytetrafluoroethylene, polyvinylidene fluoride or styrene butadiene rubber; and the dispersant is one or more of anhydrous ethanol, isopropyl alcohol or 1-methyl-2-pyrrolidone.

[0028] Further preferably, the sodium-embeddable / detachable ion active material comprises transition metal oxides, phosphates, pyrophosphates, sulfates and fluorophosphates; and the soluble sodium salt organic solution is obtained by dissolving sodium salt in an organic solvent, the sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium trifluoromethyl sulfonate and sodium nitrate, and the organic solvent is one or more of ethylene carbonate, propylene carbonate, fluorinated ethylene carbonate, dimethyl carbonate, diethyl carbonate, diethylene glycol dimethyl ether, 1,3-cyclopentanediol, ethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and triethylene glycol dimethyl ether.

[0029] Further preferably, the shell of the battery is made of aluminum shell, aluminum plastic film (soft package battery), stainless steel and composite materials thereof, and the shape is button type, cylindrical or square.

[0030] The composite electrode material has both the ultra-thin sodium titanate sheet structure and the stable carbon-coated interface, the synthesis method is simple, easy to scale up, and controllable, and the composite electrode material has the advantages of high initial coulombic efficiency, low working voltage, high capacity, excellent rate characteristics and cycle stability as the negative electrode of a sodium ion battery or the positive electrode of a sodium battery, and has a broad market application prospect.

[0031] Compared with the prior art, the present application has the following advantages:

[0032] 1. The ultra-thin sodium titanate nanosheet in the structure body effectively shortens the ion transmission path and improves the ion transmission rate, and the surface of the sodium titanate is coated with nitrogen-doped carbon, which not only can be embedded into the sodium titanate crystal lattice to increase the lattice spacing of the sodium titanate, release more sodium storage sites, reduce the intrinsic band gap of the sodium titanate and improve the electronic conductivity, but also can inhibit the adverse decomposition of the electrolyte on the surface to form a solid-state electrolyte interface film (SEI) with excellent structure and composition;

[0033] 2.The material has high first-week coulombic efficiency, high capacity, excellent rate characteristics and cycle stability through the synergistic design of the bulk phase and the interface;

[0034] 3.The composite electrode material has excellent kinetic characteristics, actual reversible capacity exceeding the theoretical capacity, ultra-high first-week coulombic efficiency and stable electrochemical storage, and the sodium-ion battery or sodium battery containing the material has the advantages of high energy density and power density, and has broad market application prospects.

[0035] 4.The preparation process is simple, easy to scale up production, and controllable, and the pore size, specific surface area and mesostructure of the obtained material can be adjusted. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is an XRD graph of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared in Example 1;

[0037] Figure 2 is a Raman graph of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared in Example 1;

[0038] Figure 3 is a TEM graph of the rGO / single-layer mesoporous titanium dioxide precursor prepared in Example 1;

[0039] Figure 4 is an AFM graph of the rGO / single-layer mesoporous titanium dioxide precursor prepared in Example 1;

[0040] Figure 5 is a TEM graph of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared in Example 1;

[0041] Figure 6 is a TEM graph of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared in Example 1;

[0042] Figure 7 is a HRTEM graph of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared in Example 1;

[0043] Figure 8 is an XPS graph of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared in Example 1;

[0044] Figure 9 is a charge-discharge curve graph of the sodium battery prepared in Example 1;

[0045] Figure 10 is a rate performance graph of the sodium battery prepared in Example 1;

[0046] Figure 11 is a cycle stability plot of the sodium battery prepared in Example 1;

[0047] Figure 12 is an XRD plot of the sample provided for Comparative Example 1;

[0048] Figure 13 is a TEM plot of the sample provided for Comparative Example 1;

[0049] Figure 14 is a HRTEM plot of the sample provided for Comparative Example 1. DETAILED DESCRIPTION

[0050] The present application will be described in detail below with reference to the drawings and specific examples. The following examples are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0051] In the following examples, unless otherwise specified, the raw materials or processing techniques are all conventional commercially available raw materials or conventional processing techniques in the art.

[0052] Example 1

[0053] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0054] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were redispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a clear solution, 5.0 mL of absolute ethanol mixed solution containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material.

[0055] Figure 1 The X-ray diffraction (XRD) pattern of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite material, part of the crystal face corresponds to the standard card (PDF #31-1329). The diffraction peak (2 theta = 8.5°) corresponds to the (001) crystal face, showing the highest intensity, which indicates that the (001) crystal face is the dominant crystal face of sodium titanate, and the diffraction peak moves to low angle, which indicates that the crystal face spacing is larger than the standard (001) crystal face, which indicates that the introduction of dopamine increases the spacing of the (001) crystal face of sodium titanate. Compared with the XRD data of the sample without dopamine, it can also be clearly confirmed. Figure 2 The Raman scattering spectrum of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite material, where the peaks at 192 and 273 cm -1 are the stretching vibrations of Na-O-Ti, the peaks at 432 and 668 are the stretching vibrations of Ti-O-Ti, and the peak at 863 is the stretching vibration of the shorter Ti-O bond in TiO6. Figure 3 The TEM image of the precursor rGO / mesoporous TiO2 shows a uniform two-dimensional sheet mesoporous structure. Figure 4 The AFM image of the precursor rGO / mesoporous TiO2, the thickness is about 10 nm. Figure 5TEM image of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material, the composite material presents a two-dimensional sheet structure, is dispersed and not aggregated, and has a particle length of about 5-7 μm and a thickness of about 10 nm, which is consistent with the precursor. The realization of the two-dimensional structure also confirms the templating effect of the internal few-layer reduced graphene oxide. Figure 6 TEM image of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material, the ultrathin two-dimensional sodium titanate nanosheet is uniformly distributed, and the nanosheet has a length of about 5 nm and a width of about 1-2 nm. Figure 7 High-resolution TEM image of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material, it can be seen that the lattice fringes of the (001) crystal plane of sodium titanate exist, and the lattice fringes have obvious defects, and the outer layer is covered with 2-3 nm of amorphous nitrogen-doped carbon. Figure 8 XPS N1s spectrum of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material, the existence of pyridine nitrogen and C-N-Ti bond in the spectrum also confirms the existence of the outer layer of nitrogen-doped carbon. Among them, the total amount of few-layer reduced graphene oxide and carbon is 28.2% of the mass of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite material.

[0056] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material is used as a positive active material, the positive active material is mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10, 1-methyl-2-pyrrolidone is used as a dispersant, the mixture is uniformly mixed to form a slurry, and the slurry is coated on a copper foil. After vacuum drying at 80°C, a positive electrode sheet with a diameter of 13 mm is obtained, a sodium metal sheet is used as a negative electrode (with a diameter of 16 mm), a glass fiber membrane (Whatman GF / D) is used as a separator, and 1M NaSO3CF3 dissolved in DGM is used as an electrolyte. A stainless steel shell is used as an outer shell, and a CR2025 type button cell is assembled. The sodium battery assembled in the above process is subjected to charge-discharge test at room temperature in a potential range of 0.01-3.0V, and the charge-discharge curve and rate performance are as shown in Figure 9 and Figure 10 The discharge platform at 0.2C is less than 0.5V, the specific capacity reaches 340mAh / g, and the initial coulombic efficiency is as high as 86.4%. At a rate of 80C, the discharge specific capacity can reach 110mAh / g (1C=310mA / g). The cycle stability at a rate of 0.2C is as shown in Figure 11 After 150 cycles, the reversible capacity is still 318mAh / g, and the capacity retention rate is close to 100%.

[0057] Example 2

[0058] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the application are as follows:

[0059] Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of a mixture solution containing 50 mg of graphene oxide in absolute ethanol was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained a monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain a two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material.

[0060] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as the positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. Using 1-methyl-2-pyrrolidone as a dispersant, the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as the negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaClO4 solution in EC:DEC (volume ratio of 1:1) was used as an electrolyte. A stainless steel shell was used as the outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0061] Example 3

[0062] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0063] Pluronic F127 (PEO106 PPO 70 PEO 106 , M w = 12600 g mol -1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The formed clear yellow solution was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of a mixture solution containing 50 mg of graphene oxide in absolute ethanol was added into the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursors grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added into 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0064] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as a positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. After mixing the above mixture uniformly, a slurry was prepared and coated onto a copper foil using 1-methyl-2-pyrrolidone as a dispersant. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained. Sodium metal sheet was used as the negative electrode (diameter of 16 mm), glass fiber membrane (Whatman GF / D) was used as the separator, and 1 M NaPF6 dissolved in EC:DMC (volume ratio of 1:1) was used as the electrolyte. A stainless steel shell was used as the outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0065] Example 4

[0066] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0067] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO106 , M w = 12600 g mol -1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of a mixture solution containing 50 mg of graphene oxide in absolute ethanol was added into the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursors grown on rGO. After mixing 0.15 g of the precursors with 60 mg of dopamine, the mixture was added into 30 mL of 0.1 M sodium hydroxide solution and treated at 150 °C in a reaction kettle for 24 h, followed by calcination at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0068] The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared was used as a positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10, and the mixture was mixed uniformly to form a slurry, which was coated onto a copper foil using 1-methyl-2-pyrrolidone as a dispersant. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as a negative electrode (with a diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaPF6 dissolved in DME was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0069] Example 5

[0070] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0071] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol-1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 min of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 min. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 min of stirring to form a transparent solution, 5.0 mL of a mixed solution of absolute ethanol containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 h under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0072] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as a negative active material, and the negative material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10, 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated on a copper foil. Commercial vanadium sodium phosphate fluoride was used as a positive active material, and the positive active material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 70:20:10, 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated on an aluminum foil. After vacuum drying at 80 °C, the negative and positive electrode sheets with a diameter of 13 mm were cut, glass fiber membrane (Whatman GF / D) was used as a separator, and 1M NaPF6 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as a shell to assemble a CR2025 type button cell. The sodium ion battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.1-3.0 V.

[0073] Example 6

[0074] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0075] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106, M w = 12600 g mol -1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 min of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 min. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 min of stirring to form a transparent solution, 5.0 mL of a mixture solution containing 50 mg of graphene oxide in absolute ethanol was added into the mixture. The whole solution was heated in an oil bath at 100 °C for 6 h under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursors grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added into 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0076] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as a negative active material. The negative material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10, and 1-methyl-2-pyrrolidone was used as a dispersant to mix the above mixture uniformly to form a slurry and coat it onto a copper foil. Commercial sodium vanadium phosphate was used as a positive active material. The positive active material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 70:20:10, and 1-methyl-2-pyrrolidone was used as a dispersant to mix the above mixture uniformly to form a slurry and coat it onto an lv2 foil. After vacuum drying at 80 °C, the negative and positive electrode sheets with a diameter of 13 mm were cut. Glass fiber membrane (Whatman GF / D) was used as a separator, and 1M NaPF6 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium ion battery assembled by the above process was tested for charge and discharge at room temperature within a potential range of 0.1-3.0 V.

[0077] Example 7

[0078] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0079] 1.5 g of Pluronic F127 (PEO 106PPO 70 PEO 106 , M w = 12600 g mol -1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of a mixture solution containing 50 mg of graphene oxide in absolute ethanol was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursors grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0080] The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared was used as a negative active material, and the negative material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10, 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated on a copper foil. Commercial vanadium sodium phosphate fluoride was used as a positive active material, and the positive active material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 70:20:10, 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated on an lv2 foil. After vacuum drying at 80 °C, the negative and positive electrode sheets with a diameter of 13 mm were cut, glass fiber membrane (Whatman GF / D) was used as a separator, and 1M NaClO4 solution in EC:DEC (volume ratio 1:1) was used as an electrolyte. A stainless steel shell was used as a shell to assemble a CR2025 type button cell. The sodium ion battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.1-3.0 V.

[0081] Example 8

[0082] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0083] Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of a mixture solution containing 50 mg of graphene oxide in absolute ethanol was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained a monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain a two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material.

[0084] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as a negative active material. The negative material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10, and 1-methyl-2-pyrrolidone was used as a dispersant to mix the above mixture uniformly to form a slurry and coat it onto a copper foil. Commercial sodium vanadium phosphate was used as a positive active material. The positive active material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 70:20:10, and 1-methyl-2-pyrrolidone was used as a dispersant to mix the above mixture uniformly to form a slurry and coat it onto an lv2 foil. After vacuum drying at 80 °C, the negative and positive electrode sheets with a diameter of 13 mm were cut. Glass fiber membrane (Whatman GF / D) was used as a separator, and 1M NaClO4 solution in EC:DEC (volume ratio of 1:1) was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium ion battery assembled by the above process was tested for charge and discharge at room temperature within a potential range of 0.1-3.0 V.

[0085] Example 9

[0086] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0087] 1.0 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1 ), 2.4 g of acetic acid and 3.2 g of concentrated hydrochloric acid (36 wt%) were added into 30 mL of tetrahydrofuran solution in turn. After stirring vigorously for 10 minutes, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The formed clear yellow solution was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45°C for 24 h to obtain F127 / TiO2 unimicellar gel. 3.0 g of F127 / TiO2 unimicellar gel and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After stirring for 5 minutes to form a transparent solution, 5.0 mL of a mixed solution of graphene oxide containing 50 mg of graphene oxide in absolute ethanol was added to the mixture. The whole solution was heated in an oil bath at 100°C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was separated and collected by centrifugation, washed with ethanol and dried in an oven. Finally, calcination at 350°C for 3 h under a nitrogen atmosphere was performed to remove the F127 template and improve the crystallinity, obtaining a monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1M sodium hydroxide solution, treated at 150°C in a reaction kettle for 24 h, and then calcined at 500°C for 3 h under nitrogen to obtain the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material.

[0088] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as a positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80°C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as a negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was subjected to charge and discharge tests at room temperature in a potential range of 0.01-3.0V.

[0089] Example 10

[0090] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0091] 2.0 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1 ), 2.4 g of acetic acid and 3.2 g of concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL of tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gel and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of a mixture solution containing 50 mg of graphene oxide in absolute ethanol was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained a monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain a two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material.

[0092] The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared was used as a positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry, which was coated onto a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as a negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium battery assembled in the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0093] Example 11

[0094] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0095] Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 1.5 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of a mixture solution containing 50 mg of graphene oxide in absolute ethanol was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursors grown on rGO. After mixing 0.15 g of the precursors with 60 mg of dopamine, the mixture was added to 30 mL of 0.1 M sodium hydroxide solution and treated at 150 °C in a reaction kettle for 24 h, followed by calcination at 500 °C for 3 h under nitrogen, to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0096] The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared was used as a positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10, and the mixture was mixed uniformly to form a slurry, which was coated onto a copper foil using 1-methyl-2-pyrrolidone as a dispersant. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as a negative electrode (with a diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium battery assembled in the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0097] Example 12

[0098] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0099] Pluronic F127 (PEO 106 PPO70 PEO 106 , M w = 12600 g / mol -1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 min of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 4.5 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 min. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 min of stirring to form a transparent solution, 5.0 mL of a mixture solution containing 50 mg of graphene oxide in absolute ethanol was added into the mixture. The whole solution was heated in an oil bath at 100 °C for 6 h under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursors grown on rGO. After mixing 0.15 g of the precursors with 60 mg of dopamine, the mixture was added into 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0100] The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material prepared was used as a positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10, and the mixture was mixed uniformly to form a slurry, which was coated onto a copper foil using 1-methyl-2-pyrrolidone as a dispersant. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as a negative electrode (with a diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium battery assembled in the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0101] Example 13

[0102] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0103] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w= 12600 g mol -1 ), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 min of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 min. Subsequently, 3.0 mL of glycerol was added dropwise. After 5 min of stirring to form a transparent solution, 5.0 mL of absolute ethanol mixed solution containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 h under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated by centrifugation and collected, washed with ethanol and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0104] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as the positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as the negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0105] Example 14

[0106] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0107] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 7.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of absolute ethanol mixed solution containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0108] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as the positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as the negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as the outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0109] Example 15

[0110] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0111] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of absolute ethanol mixed solution containing 30 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was separated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0112] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as the positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as the negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as the outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0113] Example 16

[0114] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0115] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of absolute ethanol mixed solution containing 70 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was separated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0116] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as the positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated on a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as the negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0117] Example 17

[0118] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0119] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of absolute ethanol mixed solution containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was separated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 30 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0120] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as a positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the above mixture was mixed uniformly to form a slurry and coated on a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as a negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0121] Example 18

[0122] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0123] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of absolute ethanol mixed solution containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was separated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 90 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0124] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as the positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as the negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as the outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0125] Example 19

[0126] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0127] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of absolute ethanol mixed solution containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was separated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.5 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0128] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as the positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as the negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as the outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0129] Example 20

[0130] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0131] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of absolute ethanol mixed solution containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was separated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 2.0 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 500 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0132] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as the positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80 °C, the positive electrode sheet with a diameter of 13 mm was obtained, and sodium metal sheet was used as the negative electrode (diameter of 16 mm). Glass fiber membrane (Whatman GF / D) was used as the separator, and 1 M NaSO3CF3 dissolved in DGM was used as the electrolyte. A stainless steel shell was used as the outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in the potential range of 0.01-3.0 V.

[0133] Example 21

[0134] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0135] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a transparent solution, 5.0 mL of absolute ethanol mixed solution containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was separated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursor grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 600 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0136] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as the positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80 °C, the positive electrode sheet with a diameter of 13 mm was obtained, and sodium metal sheet was used as the negative electrode (diameter of 16 mm). Glass fiber membrane (Whatman GF / D) was used as the separator, and 1 M NaSO3CF3 dissolved in DGM was used as the electrolyte. A stainless steel shell was used as the outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in the potential range of 0.01-3.0 V.

[0137] Example 22

[0138] The synthesis steps of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material used in the present application are as follows:

[0139] 1.5 g of Pluronic F127 (PEO 106 PPO 70 PEO 106 , M w = 12600 g mol -1), 2.4 g acetic acid and 3.2 g concentrated hydrochloric acid (36 wt%) were added sequentially into 30 mL tetrahydrofuran solution. After 10 minutes of vigorous stirring, 3.4 g of tetrabutyl titanate (TBOT) was added dropwise. The clear yellow solution formed was transferred into two 30 mm x 50 mm volumetric flasks and placed in an oven at 45 °C for 24 h to obtain F127 / TiO2 unimicellar gels. 3.0 g of F127 / TiO2 unimicellar gels and 3.0 mL of TMB were re-dispersed in 10.0 mL of absolute ethanol and stirred for 10 minutes. Subsequently, 5.0 mL of glycerol was added dropwise. After 5 minutes of stirring to form a clear solution, 5.0 mL of absolute ethanol mixed solution containing 50 mg of graphene oxide was added to the mixture. The whole solution was heated in an oil bath at 100 °C for 6 hours under gentle stirring at 400 rpm and allowed to cool to room temperature. The black precipitate was isolated and collected by centrifugation, washed with ethanol, and dried in an oven. Finally, calcination at 350 °C for 3 h under nitrogen atmosphere to remove the F127 template and increase the crystallinity, obtained monolayer mesoporous titanium dioxide precursors grown on rGO. After mixing 0.15 g of the precursor with 60 mg of dopamine, it was added to 30 mL of 0.1 M sodium hydroxide solution, treated at 150 °C for 24 h in a reaction kettle, and then calcined at 800 °C for 3 h under nitrogen to obtain two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode materials.

[0140] The prepared two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material was used as a positive active material, and the positive material was mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 80:10:10. 1-methyl-2-pyrrolidone was used as a dispersant, and the mixture was mixed uniformly to form a slurry and coated onto a copper foil. After vacuum drying at 80 °C, a positive electrode sheet with a diameter of 13 mm was obtained, and a sodium metal sheet was used as a negative electrode (diameter of 16 mm). A glass fiber membrane (Whatman GF / D) was used as a separator, and 1 M NaSO3CF3 dissolved in DGM was used as an electrolyte. A stainless steel shell was used as an outer shell to assemble a CR2025 type button cell. The sodium battery assembled by the above process was tested for charge and discharge at room temperature in a potential range of 0.01-3.0 V.

[0141] Comparative Example 1:

[0142] Compared with Example 1, most of them are the same, except that in this example, the introduction of dopamine is omitted.

[0143] As shown in Figure 12 Without the addition of dopamine, the crystal structure of the synthesized sodium titanate shows that the (001) crystal plane does not move to a low angle, and shows a peak consistent with the standard card (001) crystal plane position. As shown in Figure 13As shown in 14, the synthesized two-dimensional sodium titanate nanosheet has no carbon coating outside and shows obvious lattice edges without the addition of dopamine.

[0144] Comparative Example 2:

[0145] Most of them are the same as in Example 1, except that in this example, the introduction of F127 is omitted.

[0146] Comparative Example 3:

[0147] Most of them are the same as in Example 1, except that in this example, the introduction of TMB is omitted.

[0148] Most of them are the same as in Example 1, except that in this example, the introduction of glycerol is omitted.

[0149] Comparative Example 5:

[0150] Most of them are the same as in Example 1, except that in this example, the introduction of rGO is omitted.

[0151] Comparative Example 6:

[0152] Most of them are the same as in Example 1, except that in this example, the calcination step is omitted.

[0153] The above description of the comparative examples is to facilitate the ordinary skilled person in the art to understand and use the invention. Those skilled in the art can obviously make various modifications to these examples, and apply the general principles described herein to other examples without having to undergo creative labor. Therefore, the present application is not limited to the above examples, and the improvements and modifications made by those skilled in the art according to the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material, characterized in that, The two-dimensional layered structure has a particle size of 2-30 μm and a thickness of 8-12 nm, and is composed of internal few-layer reduced graphene oxide, an outer layer of ultrathin sodium titanate nanosheet, and nitrogen-doped carbon coated on the surface of the ultrathin sodium titanate nanosheet; The preparation method of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material comprises the following steps: (1) A precursor is synthesized by single-micelle self-assembly: a surfactant, a catalyst, and a complexing agent are added to an organic solvent, stirred, and then a titanium source is added, the solvent is dried to obtain a titanium dioxide single-micelle gel, the gel is dispersed in an organic solvent to form a transparent solution, and then few-layer reduced graphene oxide is added to the mixture, heated, the precipitate is collected and dried, and finally the rGO / TiO2 composite precursor is obtained after calcination; (2) A two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material is prepared by a hydrothermal treatment method: the precursor obtained in step (1) is mixed with dopamine in an aqueous solution, then added to an alkaline solution, and then subjected to hydrothermal treatment, washed, and calcined at an elevated temperature to obtain the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material; In step (1), the surfactant is one or more of polyethylene oxide-polypropylene oxide, polyethylene oxide-polybutylene oxide, polyethylene oxide-polystyrene, or polyethylene oxide-poly(methyl methacrylate) diblock copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, or polypropylene oxide-polyethylene oxide-polypropylene oxide triblock copolymer. 2.The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material of claim 1, wherein, In the composite electrode material, the total mass of the few-layer reduced graphene oxide and the carbon is 25%-30% of the mass of the composite electrode material. 3.The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material of claim 1, wherein, In step (1), the titanium source is one or more of titanium sulfate, titanium tert-butoxide, titanium methoxide, titanium tetrachloride, titanium tetrabutoxide, titanium isopropoxide, titanium tetraethoxide, or titanium acetylacetonate; The catalyst is one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, or phosphoric acid; The complexing agent is one or more of acetic acid, citric acid, acetylacetone, or ethylenediaminetetraacetic acid. 4.The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material of claim 1, wherein, In step (1), the organic solvent is one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, benzene, toluene, diethyl ether, tetrahydrofuran, chloroform, or dichloromethane. 5.The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material of claim 1, wherein, In step (2), the molar ratio of the rGO / TiO2 composite precursor to dopamine is (1-20):(0.01-1). 6.The two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material of claim 1, wherein, In step (2), the calcination is performed in an inert atmosphere, and the calcination process is to heat to 300-800 ℃ at a heating rate of 1-5 ℃ / min, and maintain the temperature for 0.5-3 h.

7. Use of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material according to claim 1 or 2, characterized in that, The composite electrode material is used to prepare a sodium ion battery or a sodium metal battery.

8. Use of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material according to claim 7, characterized in that, The sodium ion battery and the sodium battery comprise a positive electrode sheet, a negative electrode sheet, an electrolyte, a diaphragm and a shell, the diaphragm is a glass fiber diaphragm, a polyethylene, a polypropylene microporous membrane or a composite diaphragm thereof, and the electrolyte is a soluble sodium salt organic solution; in the sodium ion battery, the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material is a negative electrode, and a sodium ion-embeddable / detachable active material is used as a positive electrode; in the sodium metal battery, the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material is a positive electrode, and metal sodium is used as a negative electrode. 9.The use of the two-dimensional ultrathin sodium titanate nanosheet / carbon composite electrode material according to claim 8, characterized in that, The sodium ion-embeddable / detachable active material comprises one or more of a transition metal oxide, a phosphate, a pyrophosphate, a sulfate and a fluorophosphate; the soluble sodium salt organic solution is obtained by dissolving sodium salt in an organic solvent, the sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate and sodium trifluoromethylsulfonate, and the organic solvent is one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, diethylene glycol dimethyl ether, 1,3-cyclopentanediol, ethylene glycol dimethyl ether and triethylene glycol dimethyl ether.

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