High-stability sodium titanate negative electrode material and preparation method and application thereof

Abstract

The invention discloses a high-stability sodium titanate negative electrode material and a preparation method and application thereof.The preparation method comprises the following steps that Na2Ti3O7-coated C is soaked in gamma-Al2O3 suspension liquid, a mixed solution is obtained, stirring and centrifuging are conducted, then low-temperature sintering is conducted, and Na2Ti3O7-coated C-Al2O3 is obtained; the preparation method comprises the following steps: soaking Na2Ti3O7 coated C-Al2O3 in a NaOH solution, and carrying out hydrothermal treatment to convert the surface layer part of Al2O3 into NaAlO2, so as to obtain Na2Ti3O7 coated C-Al2O3 / NaAlO2. The surface of the Na2Ti3O7 material is sequentially coated with the C layer, the Al2O3 layer and the NaAlO2 layer, and the C layer, the Al2O3 layer and the NaAlO2 layer serve as a protective layer and also serve as an ion conductor to provide an ion channel to increase the conductivity of the material; the NaAlO2 layer is generated through in-situ conversion of the hydrothermal reaction, interface bonding is tight, permeation of electrode liquid is avoided, and stability is good.

Description

Technical Field

[0001] The present invention relates to the technical field of negative electrode materials, and in particular to a high-stability sodium titanate negative electrode material and a preparation method and application thereof. Background Art

[0002] As a preferred type of battery for large-scale energy storage and smart grid applications, sodium-ion batteries have attracted much attention due to their abundant resources and low cost. However, despite their many advantages, their practical application still faces challenges such as energy density, power density, and long-cycle stability. The anode material plays a crucial role in the energy density and stability of the battery. The ideal anode material should have a low discharge voltage, high theoretical capacity, and good first-cycle coulombic efficiency, power characteristics, and long-cycle stability.

[0003] Titanium-based anode materials have attracted extensive research due to their high sodium storage activity, high stability, low cost and non-toxicity. Among them, sodium titanate (Na2Ti3O7, NTO) as a layered compound has a high theoretical capacity and a low discharge voltage platform (about 0.3V vs Na / Na + ), which is beneficial to improving the operating voltage and energy density of the full battery. However, the large band gap of the Na2Ti3O7 material itself (3.7eV) leads to slow sodium ion insertion / extraction kinetics. In addition, the large amount of sodium insertion in the Na2Ti3O7 lattice causes severe structural strain, exposing more reactive surface sites, leading to continuous decomposition of the electrolyte, resulting in a low first-cycle coulombic efficiency and poor cycling stability.

[0004] In order to solve the above technical problems, researchers mainly improve the performance of Na2Ti3O7 by designing nanoparticle structures, surface doping, etc. For example, patent CN115472791A discloses a mesoporous sodium titanate / carbon composite electrode material and its preparation method and application, using a surfactant as a template to obtain a composite electrode material. However, this method still faces the problem of how to further improve the electrochemical performance. Patent CN118529769A discloses a method for preparing a nano-sheet carbon-coated sodium titanate composite material. This method obtains nano-sheet Na2Ti3O7 through modification treatment, which improves the stability of the material. However, this method still faces the problem of how to further improve the purity and yield of the product.

[0005] In summary, existing titanium-based anode material preparation methods often suffer from complex processes, high costs, difficulty in large-scale production, and insufficient electrochemical performance of the products. Therefore, the development of a simple and efficient preparation method, and the optimization of the material structure design to improve its sodium storage performance and cycling stability, have become important research directions for sodium-ion battery anode materials. Summary of the Invention

[0006] In response to the deficiencies in the prior art, the present invention provides a high-stability sodium titanate negative electrode material, a preparation method thereof, and an application thereof. A C layer, an Al2O3 (aluminum oxide) layer, and a NaAlO2 (sodium aluminate) layer are sequentially coated on the surface of a Na2Ti3O7 material. The outer sodium ion conductor provides an ion channel, the middle mesoporous Al2O3 layer blocks electrode liquid corrosion, and the inner carbon layer increases the material conductivity. The material is coated in one step using an organic sodium source, avoiding complex processes such as a template method and a sol-gel method. The NaAlO2 layer is generated by in-situ chemical conversion using a hydrothermal method, which has obvious advantages in interface bonding strength, ion transmission efficiency, and process compatibility.

[0007] In order to solve the above technical problems, the present invention provides a method for preparing a high-stability sodium titanate negative electrode material, comprising the following steps:

[0008] S1, immersing the Na2Ti3O7@C composite material in a γ-Al2O3 suspension to obtain a mixed solution, stirring and centrifuging it, and then sintering it at a low temperature to form an Al2O3 layer on the surface of the Na2Ti3O7@C composite material to obtain a Na2Ti3O7@C-Al2O3 composite material;

[0009] S2. The Na2Ti3O7@C-Al2O3 composite material is immersed in NaOH solution, and the surface layer of Al2O3 is partially converted into NaAlO2 through hydrothermal treatment to obtain a highly stable sodium titanate negative electrode material Na2Ti3O7@C-Al2O3 / NaAlO2.

[0010] The present invention reduces the decomposition reaction rate of the electrolyte by Al2O3 / NaAlO2 double-layer coating, wherein the Al2O3 layer with a mesoporous structure blocks the corrosion of the electrode liquid, and NaAlO2 itself has sodium ions, which can improve the ionic conductivity of the negative electrode material while serving as a protective layer. The NaAlO2 layer promotes the Na + migrate.

[0011] The present invention uses sodium hydroxide (NaOH) hydrothermal treatment on the surface of the Al2O3 layer to in-situ convert it into an outer NaAlO2 layer. Compared with the process of directly performing NaAlO2 physical / chemical coating on the surface of alumina, it has the following technical advantages: (1) The Al2O3 surface is hydrothermally converted to OH by hydrothermal reaction. -Chemical bonding occurs, and a dense and uniform NaAlO2 layer (thickness controllable to nanometer level) is generated in situ, and the coating layer NaAlO2 is seamlessly combined with the inner layer Al2O3 to avoid interfacial corrosion caused by electrolyte penetration; (2) the generated NaAlO2 has a continuous crystal structure, its sodium ion diffusion channel is complete, the sodium ion transmission path is unobstructed, and the electrode polarization is low; (3) low-temperature hydrothermal conditions (70-90°C) avoid high-temperature thermal damage to the substrate material (such as the carbon coating or the sodium titanate core); at the same time, the process temperature is low, and energy consumption is reduced by 40%-60%; the target product is generated in one-step reaction without the need for subsequent sintering, and the process flow is shortened by about 30%.

[0012] Furthermore, the Na2Ti3O7@C composite material is prepared by mixing titanium dioxide, an organic sodium source, and water, sintering the mixture under a protective atmosphere, and then pyrolyzing the organic sodium source to form a carbon layer that coats the sodium titanate particles, forming the Na2Ti3O7@C composite material. This one-step coating with the organic sodium source avoids complex steps such as template and sol-gel methods, resulting in a nanoscale carbon material coating and resolving the issue of low loading during electrode preparation.

[0013] Furthermore, the titanium dioxide is anatase titanium dioxide with a particle size of 50-100 nm;

[0014] And / or, the organic sodium source is at least one of sodium citrate, sodium gluconate, and sodium stearate.

[0015] Furthermore, the sintering temperature is 450-550° C. and the sintering time is 5-10 hours.

[0016] Furthermore, the titanium dioxide and the organic sodium source are mixed at a Na:Ti molar ratio of (2.1-2.3):3, and the sodium source provides a surplus to prevent sodium volatilization during sintering. The thickness of the carbon layer in the Na2Ti3O7@C composite material is 2-5nm.

[0017] Furthermore, in S1, the particle size of γ-Al2O3 in the γ-Al2O3 suspension is ≤20nm, the concentration of γ-Al2O3 is 5-10wt%, the solvent is an organic solvent; and the dispersant is also included with a mass of 1-10% of the mass of γ-Al2O3.

[0018] Furthermore, the organic solvent is selected from at least one of ethanol, isopropanol, and acetone, and the dispersant is selected from at least one of polyacrylic acid, polyethylene glycol, and polyvinyl pyrrolidone.

[0019] Furthermore, in S1, the temperature of the low temperature sintering is 200-300 ° C, the time is 2-3h, the generated Al2O3 layer is a mesoporous structure with a pore size of 2-5nm, and the low temperature sintering retains the inner elastic layer sp 2structure (Raman ID / IG=0.85), avoiding NTO phase transition caused by high temperature.

[0020] Furthermore, in S1, the concentration of the Na2Ti3O7@C composite material in the mixed solution is 5-10 wt%.

[0021] Furthermore, in S2, the temperature of the hydrothermal treatment is 70-90°C and the time is 3-5 hours.

[0022] The second aspect of the present invention provides a sodium titanate negative electrode material prepared by the preparation method described in the first aspect.

[0023] The third aspect of the present invention provides the use of the sodium titanate negative electrode material described in the second aspect in a sodium ion battery or a lithium ion battery.

[0024] Beneficial effects of the present invention:

[0025] The present invention sequentially coats a C layer, an Al2O3 layer and a NaAlO2 layer on the surface of a Na2Ti3O7 material. The outer NaAlO2 layer serves as a protective layer and also provides an ion channel as an ion conductor. The middle Al2O3 layer with a mesoporous structure blocks electrode liquid corrosion, and the inner carbon layer increases the electrical conductivity of the material.

[0026] The present invention uses a one-step coating method of an organic sodium source to avoid complex processes such as a template method and a sol-gel method, thereby obtaining a nano-scale carbon material coating layer and solving the problem of low loading in the electrode preparation process.

[0027] The present invention uses sodium hydroxide (NaOH) hydrothermal treatment on the surface of the Al2O3 layer to in-situ transform and generate an outer NaAlO2 layer. The chemical bonding interface of NaAlO2 and Al2O3 is seamlessly combined, avoiding electrode liquid penetration, inhibiting side reactions, improving safety, and ensuring long-term cycle stability. The hydrothermal reaction is synthesized in one step without the need for a sintering process, avoiding damage to the base material while reducing energy consumption and improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is a 0.5C charge and discharge curve diagram of a negative electrode material battery according to Example 1 of the present invention;

[0030] Figure 2 This is the capacity retention curve of the negative electrode material of Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The following will provide a clear and complete description of the technical solutions of the present invention in conjunction with specific embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] This embodiment provides a method for preparing a high-stability sodium titanate negative electrode material, comprising the following steps:

[0033] S1, immersing the Na2Ti3O7@C composite material in a γ-Al2O3 suspension to obtain a mixed solution, stirring and centrifuging it, and then sintering it at a low temperature to form an Al2O3 layer on the surface of the Na2Ti3O7@C composite material to obtain a Na2Ti3O7@C-Al2O3 composite material;

[0034] S2. The Na2Ti3O7@C-Al2O3 composite material is immersed in NaOH solution, and the surface layer of Al2O3 is partially converted into NaAlO2 through hydrothermal treatment to obtain a highly stable sodium titanate negative electrode material Na2Ti3O7@C-Al2O3 / NaAlO2.

[0035] This embodiment reduces the decomposition reaction rate of the electrolyte by Al2O3 / NaAlO2 double-layer coating, wherein the mesoporous Al2O3 layer blocks the corrosion of the electrode liquid, and NaAlO2 itself contains sodium ions, which can improve the ionic conductivity of the negative electrode material while serving as a protective layer. The NaAlO2 layer promotes Na + Migration. The hydrothermal treatment of the Al2O3 layer with sodium hydroxide (NaOH) is used to in situ convert the outer NaAlO2 layer. Compared with the process of direct physical / chemical coating of NaAlO2 on the alumina surface, it has the following technical advantages: (1) The Al2O3 surface is converted to OH by hydrothermal reaction. - Chemical bonding occurs, and a dense and uniform NaAlO2 layer (thickness controllable to nanometer level) is generated in situ, and the coating layer NaAlO2 is seamlessly combined with the inner layer Al2O3 to avoid interfacial corrosion caused by electrolyte penetration; (2) the generated NaAlO2 has a continuous crystal structure, its sodium ion diffusion channel is complete, the sodium ion transmission path is unobstructed, and the electrode polarization is low; (3) low-temperature hydrothermal conditions (70-90°C) avoid high-temperature thermal damage to the substrate material (such as the carbon coating or the sodium titanate core); at the same time, the process temperature is low, and energy consumption is reduced by 40%-60%; the target product is generated in one-step reaction without the need for subsequent sintering, and the process flow is shortened by about 30%.

[0036] As a preferred embodiment, the Na2Ti3O7@C composite material is prepared by mixing titanium dioxide, an organic sodium source, and water, followed by sintering under a protective atmosphere. The organic sodium source decomposes to form a carbon layer that coats the sodium titanate particles, forming the Na2Ti3O7@C composite material. This one-step coating with the organic sodium source avoids complex processes such as template and sol-gel methods, resulting in a nanoscale carbon coating and addressing the issue of low electrode loading during the electrode preparation process. The titanium dioxide is anatase-type titanium dioxide with a particle size of 50-100 nm; the organic sodium source is at least one of sodium citrate, sodium gluconate, and sodium stearate. The sintering temperature is 450-550°C for 5-10 hours; the protective atmosphere is argon or an argon / hydrogen mixture (volume ratio Ar / H2 = 95:5); the titanium dioxide and organic sodium source are mixed in a Na:Ti molar ratio of (2.1-2.3):3, and the carbon layer in the Na2Ti3O7@C composite material has a thickness of 2-5 nm.

[0037] As a preferred embodiment, in S1, the particle size of γ-Al2O3 in the γ-Al2O3 suspension is ≤20nm, the concentration of γ-Al2O3 is 5-10wt%, and the solvent is an organic solvent; it also includes a dispersant with a mass of 1-10% of the mass of γ-Al2O3. Wherein, the organic solvent is selected from at least one of ethanol, isopropanol, and acetone, and the dispersant is selected from at least one of polyacrylic acid, polyethylene glycol, and polyvinyl pyrrolidone; the temperature of the low-temperature sintering is 200-300℃, the time is 2-3h, the generated Al2O3 layer is a mesoporous structure with a pore size of 2-5nm, and the low-temperature sintering retains the inner elastic layer sp 2 structure (Raman ID / IG=0.85), avoiding NTO phase transition caused by high temperature; the concentration of Na2Ti3O7@C composite material in the mixed solution is 5-10wt%.

[0038] As a preferred embodiment, in S2, the temperature of the hydrothermal treatment is 70-90°C and the time is 3-5 hours.

[0039] Example 1

[0040] This embodiment relates to a method for preparing a high-stability sodium titanate negative electrode material, comprising the following steps:

[0041] (1) Preparation of Na2Ti3O7@C composite material: Anatase TiO2 (particle size 80 nm, purity ≥99.9%), sodium citrate, and water were ball-milled at a molar ratio of Na:Ti = 2.2:3 (ball-to-material ratio 5:1, rotation speed 300 rpm, time 4 h). The mixture was then sintered at 500°C for 6 h under a protective atmosphere (volume ratio Ar / H2 = 95:5). The organic sodium source was decomposed to generate a carbon layer coating the sodium titanate particles, forming the Na2Ti3O7@C composite material.

[0042] (2) Preparation of γ-Al2O3 suspension: γ-Al2O3 (particle size 20 nm) was dispersed in ethanol (solid content 5 wt%), and polyacrylic acid (PAA, MW = 2000) was added as a dispersant (γ-Al2O3:PAA = 10:1 w / w). The mixture was ultrasonically treated for 30 min to obtain a γ-Al2O3 suspension.

[0043] (3) impregnating the Na2Ti3O7@C composite material obtained in step (1) into the γ-Al2O3 suspension obtained in step (2) to obtain a mixed solution, wherein the concentration of the Na2Ti3O7@C composite material in the mixed solution is 10 wt%, stirred for 2 h, centrifuged, and then sintered at 300° C. for 2 h to form an Al2O3 layer on the surface of the Na2Ti3O7@C composite material, thereby obtaining a Na2Ti3O7@C-Al2O3 composite material;

[0044] (4) The Na2Ti3O7@C-Al2O3 composite material was immersed in a 1M NaOH solution and hydrothermally treated at 80°C for 4 h to convert the Al2O3 surface layer into NaAlO2, thereby obtaining a highly stable sodium titanate negative electrode material Na2Ti3O7@C-Al2O3 / NaAlO2.

[0045] Comparative Example 1

[0046] The difference between this comparative example and Example 1 is that step (4) is omitted, and the other steps and parameters remain unchanged to prepare the Na2Ti3O7@C-Al2O3 composite material.

[0047] Comparative Example 2

[0048] The difference between this comparative example and Example 1 is that steps (2) to (4) are omitted, and the other steps and parameters remain unchanged to prepare the Na2Ti3O7@C composite material.

[0049] Comparative Example 3

[0050] The difference between this comparative example and Example 1 is that step (4) does not adopt an in-situ hydrothermal reaction conversion method, but directly coats NaAlO2 on the surface of the Na2Ti3O7@C-Al2O3 composite material, specifically:

[0051] (a) Presynthesis of NaAlO2 powder:

[0052] Al(NO3)3·9H2O and NaOH were dissolved in deionized water at a molar ratio of 1:3, and hydrothermally reacted at 80°C for 12 hours. The mixture was centrifugally dried and then ground to obtain NaAlO2 powder (average particle size 200 nm).

[0053] (b) Mechanical mixing coating:

[0054] The Na2Ti3O7@C-Al2O3 composite material prepared in step (3) of Example 1 was mixed with the NaAlO2 powder obtained in step (a) at a mass ratio of 95:5, and ethanol (solid-to-liquid ratio 1:10) was added and ball milled for 6 hours (rotation speed 400 rpm), and then vacuum dried at 60°C for 12 hours;

[0055] (c) High temperature sintering:

[0056] In an Ar atmosphere, the temperature was raised to 500°C at a rate of 5°C / min and kept at that temperature for 2 hours, so that the NaAlO2 particles were partially melted and attached to the surface of the composite material to form a physical coating layer.

[0057] Comparative Example 4

[0058] The difference between this comparative example and Example 1 is that the organic sodium source sodium citrate in step (1) is replaced by sodium carbonate, and the other steps and parameters remain unchanged.

[0059] Test Case

[0060] The negative electrode material obtained in Example 1 and Comparative Examples 1-4 was used as the negative electrode active material, acetylene black was used as the conductive agent, and PVDF was used as the binder. The active material: conductive agent: binder were added to the solvent NMP at a mass ratio of 8:1:1 to obtain a slurry with a binder concentration of 5 wt%. The slurry was applied to the surface of 6 μm aluminum foil by manual coating and dried to obtain a pole piece. The pole piece was used as the working electrode, the sodium sheet was used as the counter electrode, and the electrolyte was 1 mol / L NaPF6 (the solvent was ethylene carbonate (EC) and dimethyl carbonate (DMC), with a volume ratio of 1:1). A half-cell was assembled for electrochemical testing. Figure 1 As shown in the figure, the negative electrode material battery obtained in Example 1 has an initial discharge capacity of 152 mAh / g at 0.5C and a capacity retention rate of 97.3% after 400 cycles. Figure 2 The electrochemical performance test results of the sodium ion battery of the negative electrode materials of Example 1 and Comparative Examples 1-4 are shown in Table 1.

[0061] Table 1

[0062]

[0063] From the comparison between Example 1 and Comparative Example 1, it can be seen that there is no NaAlO2 outer layer in Comparative Example 1, which reduces the sodium ion transmission rate and the rate performance. The exposed NaAlO2 surface reacts weakly with the electrolyte (EC / DMC), the SEI film thickens, and the capacity retention rate decreases. In Comparative Example 2, only the carbon layer is coated, and the initial electrochemical performance is good. However, due to the lack of NaAlO2 and Al2O3 coating layers, the Ti 3+ Oxidized by electrolyte to Ti 4+, active sodium ions are consumed, and the capacity retention rate decreases; in Comparative Example 3, no in-situ hydrothermal reaction is performed, and NaAlO2 is directly coated on the outside of the Al2O3 layer. The directly coated NaAlO2 is prone to local agglomeration or discontinuous coverage, and there are cracks or pores in the coating layer, which accelerates the reaction with the electrolyte and reduces the capacity retention rate; in Comparative Example 4, there is no organic carbon coating, the specific capacity of the battery decreases, the discontinuous carbon layer cannot effectively block the penetration of the electrolyte, the interface side reaction is aggravated, and the capacity retention rate decreases.

[0064] In summary, the present invention sequentially coats a C layer, an Al2O3 layer, and a NaAlO2 layer on the surface of the Na2Ti3O7 material. The outer NaAlO2 layer acts as a protective layer and also provides an ion channel as an ion conductor. The middle mesoporous Al2O3 layer blocks electrode liquid corrosion, and the inner carbon layer increases the material conductivity. Through a one-step coating method using an organic sodium source, complex processes such as a template method and a sol-gel method are avoided to obtain a nano-scale carbon material coating layer, thereby solving the problem of low load in the electrode preparation process. The outer NaAlO2 layer is generated by in-situ conversion using sodium hydroxide (NaOH) hydrothermal treatment on the surface of the Al2O3 layer. The chemical bonding interface of NaAlO2 and Al2O3 is seamlessly combined, avoiding electrode liquid penetration, suppressing side reactions, improving safety, and ensuring long-term cycle stability. The hydrothermal reaction is synthesized in one step without the need for a sintering process, thereby avoiding damage to the base material while reducing energy consumption and improving efficiency.

[0065] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a high-stability sodium titanate negative electrode material, characterized in that: The steps include: S1, immersing the Na2Ti3O7@C composite material in a γ-Al2O3 suspension to obtain a mixed solution, stirring and centrifuging it, and then sintering it at a low temperature to form an Al2O3 layer on the surface of the Na2Ti3O7@C composite material to obtain a Na2Ti3O7@C-Al2O3 composite material; S2. The Na2Ti3O7@C-Al2O3 composite material is immersed in NaOH solution, and the surface layer of Al2O3 is partially converted into NaAlO2 through hydrothermal treatment to obtain a highly stable sodium titanate negative electrode material Na2Ti3O7@C-Al2O3 / NaAlO2.

2. The method for preparing a high-stability sodium titanate negative electrode material according to claim 1, wherein: In S1, the preparation method of the Na2Ti3O7@C composite material is: titanium dioxide, an organic sodium source and water are mixed, and then sintered under a protective atmosphere, and the organic sodium source is cracked to generate a carbon layer to coat the sodium titanate particles to form the Na2Ti3O7@C composite material.

3. The method for preparing a high-stability sodium titanate negative electrode material according to claim 2, wherein: The titanium dioxide is anatase titanium dioxide with a particle size of 50-100 nm; And / or, the organic sodium source is at least one of sodium citrate, sodium gluconate, and sodium stearate.

4. The method for preparing a high-stability sodium titanate negative electrode material according to claim 2, wherein: The sintering temperature is 450-550° C. and the sintering time is 5-10 hours.

5. The method for preparing a high-stability sodium titanate negative electrode material according to claim 1, wherein: In S1, the particle size of γ-Al2O3 in the γ-Al2O3 suspension is ≤20nm, the concentration of γ-Al2O3 is 5-10wt%, the solvent is an organic solvent, and the method further includes a dispersant whose mass is 1-10% of the mass of γ-Al2O3.

6. The method for preparing a high-stability sodium titanate negative electrode material according to claim 1, wherein: In S1, the low-temperature sintering temperature is 200-300° C. and the time is 2-3 hours.

7. The method for preparing a high-stability sodium titanate negative electrode material according to claim 1, wherein: In S1, the concentration of the Na2Ti3O7@C composite material in the mixed solution is 5-10 wt%.

8. The method for preparing a high-stability sodium titanate negative electrode material according to claim 1, wherein: In S2, the temperature of the hydrothermal treatment is 70-90°C and the time is 3-5 hours.

9. A sodium titanate negative electrode material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the sodium titanate negative electrode material according to claim 9 in a sodium ion battery or a lithium ion battery.

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