Preparation method of metal-doped sodium titanate negative electrode material

Abstract

The application provides a preparation method of a metal-doped sodium titanate negative material, which comprises the following steps: S1, hydrolysis solution preparation: dissolving titanyl sulfate and metal A sulfate in water as a hydrolysis solution, wherein the molar ratio of A:Ti is 0.01-0.5:1; S2, bottom liquid preheating: taking a proper amount of deionized water in a reaction kettle and preheating to 80-110 DEG C; S3, hydrolysis: under the state of stirring, the hydrolysis solution is uniformly added into the reaction kettle, and the system temperature in the reaction kettle is kept constant; S4, preparation of metatitanic acid: after the hydrolysis, the slurry is cooled to room temperature, washed with water and dried to obtain metal-doped metatitanic acid; S5, preparation of sodium titanate: the sodium source and the metal-doped metatitanic acid are uniformly mixed according to the molar ratio of sodium and titanium 2:3, calcined under the argon atmosphere, and then naturally cooled to obtain the metal-doped sodium titanate. The metal-doped sodium titanate prepared by the application has low cost, simple process and excellent product performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a method for preparing a metal-doped sodium titanate negative electrode material. Background Art

[0002] With the increasing global demand for renewable energy, energy storage technology has become crucial for achieving energy transition and ensuring energy security. Among various energy storage technologies, sodium-ion batteries (Na-ion batteries) are emerging as a strong competitor to lithium-ion batteries, particularly in the field of large-scale energy storage, due to their abundant resources, low cost, and potentially high energy density. In Na-ion batteries, the choice of anode material plays a crucial role in their performance. Sodium titanate, as one such anode material, has garnered extensive attention and research in recent years. However, its practical application still faces several challenges. One challenge is its high cost, primarily due to the synthesis method and titanium source. Another challenge is the inherently poor conductivity of the material, which limits its performance under high current charge and discharge conditions. Currently, many approaches, such as nanoengineering, morphology manipulation, and metal / nonmetal coating, are employed, but these methods are associated with high costs, low yields, and difficulties in industrial production. While the introduction of heteroatoms into Na-ion batteries is an effective approach to improving conductivity, the doping methods typically employ hydrothermal, solid-phase, and sol-gel methods. These methods are costly and difficult to scale up.

[0003] Qiu Xiaoming et al. provide a method for preparing a nickel-doped sodium titanate / graphene composite material, which first prepares a precursor solution of the composite material, then prepares a sodium titanate / graphene composite material and performs nickel doping, and finally obtains a nickel-doped sodium titanate / graphene composite material after annealing. The nickel-doped sodium titanate / graphene composite material provided by this invention has a high sodium storage capacity and good reversibility. The sodium-based dual-ion battery prepared using the above composite material has a reversible capacity of 255.4mAh / g at a current density of 0.05A / g, and good cycle stability (CN202410100248.9). Liu Jinping et al. disclose an iron-doped sodium titanate nanoarray electrode material and a preparation method thereof, wherein the electrode material is composed of a titanium sheet as a substrate and an iron-doped sodium titanate array film, wherein the array film is assembled from interlaced sodium titanate nanosheets, the thickness of the sodium titanate nanosheets is 30 nanometers, and they are evenly and densely distributed on the surface of the titanium sheet, and the morphology and size of the array film can be effectively regulated by regulating the ratio of the precursors. The interlaced nanosheet array structure in this invention can make the electrolyte fully contact with the active material, increase the permeability of the electrolyte, and reduce the interface resistance; and the nanoarray is directly grown on the titanium sheet current collector, shortening the ion transmission path and facilitating the transmission of electrons (CN201911049478.2). Han Yong et al. proposed a preparation process for single / multi-element doped sodium titanate nanorod array coatings. Different sodium titanate nanorod array coatings were prepared on the surface of pure titanium using a hydrothermal (HT) method. The above coatings were hydrothermally treated again to achieve single / multi-element (Mg, Ca, Sr or Zn) doping of nanorod-shaped sodium titanate in the coating (CN201811456718.6). Weijia Meng et al. proposed the design and preparation of hollow NTO microspheres (H-NTO) with oxygen defects, which are made of two-dimensional ultrathin nanosheets with unique chemically bonded NTO / C(N) interfaces. The preparation involves first hydrothermally synthesizing TiO2 microspheres, then hydrothermally synthesizing NTO microspheres. Finally, the prepared NTO sample is calcined at 450°C for 2 hours in an Ar / H2 (95% / 5%) atmosphere. H-NTO exhibits high specific capacity and excellent rate performance as a negative electrode material for SIBs.

[0004] Wang Chao et al. proposed a potassium-doped sodium titanate electrode material and its preparation method and application. The potassium-doped sodium titanate electrode material has a rod-like layered structure and is synthesized by a simple solid-phase method. The precursors sodium carbonate, potassium carbonate and anatase phase titanium dioxide are ball-milled in proportion and then sintered in air by microwave. The addition of potassium increases the exposure of the (100) crystal plane of sodium titanate and reduces the exposure of the (003) crystal plane. The potassium-doped sodium titanate of this invention is used as a negative electrode material in sodium ion batteries. Due to the addition of potassium, the sodium ion diffusion channels become more numerous and shorter, which is beneficial to the storage of sodium ions, thereby improving the specific capacity and rate performance of the sodium titanate material (application number: CN202211220673.9). SDemirel et al. used Na2CO3, TiO2 and V2O5 powders to prepare Na2 Ti 6-x V x O 13 Samples (where x = 0, 0.025, 0.05, and 0.1) were prepared by heating the mixed powder at 800°C in air for 16 hours to remove carbonates from the structure. This was followed by a second heat treatment at 1100°C in air for 24 hours to obtain the pure final powder. The sample with x = 0.05 exhibited superior electrochemical performance compared to the undoped sample.

[0005] It can be seen that the existing sodium titanate doping technology mainly focuses on sodium titanate doping through the hydrothermal method. The titanium sources used are mostly expensive products such as tetrabutyl titanate and titanium metal. Although there have been some innovations in the process and improvements in performance, there are also some potential disadvantages such as high cost, low repeatability, low yield, difficulty in large-scale production, etc., and the process flow is complicated, which will be accompanied by more energy consumption and labor costs; even if the solid-phase doping method is currently used, although the process is simple and easy to scale up production, the titanium source is anatase titanium dioxide, which is relatively expensive, resulting in high cost of sodium titanate, and solid-phase doping is prone to uneven doping. Summary of the Invention

[0006] In order to solve the above problems existing in the existing sodium titanate negative electrode material doping technology, the present invention provides a method for preparing a metal-doped sodium titanate negative electrode material.

[0007] The present invention provides a method for preparing a metal-doped sodium titanate negative electrode material, which comprises the following steps:

[0008] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and metal A sulfate in water to form a hydrolysis solution, wherein the molar ratio of A:Ti is 0.01-0.5:1;

[0009] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reaction kettle and preheat it to 80℃-110℃;

[0010] S3, hydrolysis: under stirring, the hydrolysis solution is added to the reactor at a uniform rate, and the temperature of the system in the reactor is kept constant. The hydrolysis reaction ends when the feeding is completed;

[0011] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying to obtain metal-doped metatitanic acid (HTO-A);

[0012] S5. Preparation of sodium titanate: uniformly mixing a sodium source and metal-doped metatitanic acid according to a sodium to titanium molar ratio of 2:3, calcining under an argon atmosphere, and then naturally cooling to obtain metal-doped sodium titanate (NTO-A).

[0013] Furthermore, in step S1, A is one or a combination of K, Au, Cu, Zr, Mg, Nb, Ca, V, Sr, Mo, and Al.

[0014] Furthermore, the concentration of the hydrolysis solution in step S1 is 170-240 g / L.

[0015] Furthermore, the stirring speed in step S3 is 1000-1400 rpm.

[0016] Furthermore, the feeding rate of the hydrolysis solution in step S3 is 1.0-5 mL / min.

[0017] Furthermore, during the addition process in step S3, the system temperature is kept constant at 80°C-110°C.

[0018] Furthermore, the feeding time of the titanyl sulfate solution in step S3 is 1-12 hours.

[0019] Furthermore, in step S4, the drying temperature is 120° C. and the drying time is 10 hours.

[0020] Furthermore, in step S5, the sodium source is one or more of sodium acetate, sodium carbonate, sodium hydroxide, sodium oxalate, sodium oxide, and sodium peroxide.

[0021] Furthermore, the calcination in step S5 is as follows: heating to 800-950° C. at a heating rate of 5° C. / min and keeping the temperature for 5-15 hours.

[0022] The present invention uses a sulfate solution of metal ions and a titanyl sulfate solution for hydrolysis to obtain metatitanic acid (HTO) uniformly doped with trace amounts of metal elements. The metatitanic acid and a sodium source are then directly calcined to synthesize heterogeneous ion-regulated sodium titanate. The beneficial technical effects are as follows:

[0023] 1. The present invention directly uses a sulfate solution of metal ions and a titanyl sulfate solution for hydrolysis. The metal ions affect the hydrolysis kinetics and change the particle size distribution and morphology characteristics of the product.

[0024] 2. The present invention directly dopes during the hydrolysis process, which can reduce the additional doping steps and the step of converting metatitanic acid into titanium dioxide, thereby reducing production costs and energy consumption, simplifying the operation process, and facilitating repeated experiments and scale-up.

[0025] 3. The present invention can make the metal ions more evenly distributed in the lattice of metatitanic acid, and then evenly distributed in the lattice of sodium titanate, thereby improving the quality of the sodium titanate product and being beneficial to improving its electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the SEM spectrum of the hydrolysis product HTO-Al in Example 1 of the present invention;

[0027] Figure 2 is the XRD spectrum of the hydrolysis product HTO-Al in Example 1 of the present invention;

[0028] Figure 3 This is the SEM spectrum of NTO-Al prepared in Example 1 of the present invention;

[0029] Figure 4 This is the XRD spectrum of NTO-Al prepared in Example 1 of the present invention;

[0030] Figure 5 Mapping spectrum of NTO-Al prepared in Example 1 of the present invention;

[0031] Figure 6 The rate performance diagram of the NTO-Al negative electrode prepared in Example 1 of the present invention;

[0032] Figure 7 This is a performance diagram of the NTO-Al negative electrode prepared in Example 1 of the present invention after 200 cycles at 200 mA / g. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0034] Example 1

[0035] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0036] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and aluminum sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 240 g / L and the molar ratio of Al:Ti is 0.12:1;

[0037] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 80°C;

[0038] S3, hydrolysis: under stirring at 1200 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.2 mL / min, and the temperature of the reactor was kept constant at 80°C. The feeding time was 8 h. The hydrolysis reaction ended when the feeding was completed;

[0039] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying at 120° C. for 10 h to obtain aluminum-doped metatitanic acid (HTOAl);

[0040] S5. Preparation of sodium titanate: Sodium hydroxide and aluminum-doped metatitanic acid (HTOAl) were mixed evenly in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, heated to 900°C at a heating rate of 5°C / min, kept at this temperature for 10 hours, and then naturally cooled to obtain aluminum-doped sodium titanate (NTOAl).

[0041] Through testing, the aluminum metal-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the aluminum metal-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 153 mAh / g at 100 mA / g, a specific capacity of 114 mAh / g at 2000 mA / g, and a capacity retention rate of 74.5%; after 200 cycles at 200 mA / g, the specific capacity is still 123 mAh / g, and the capacity retention rate reaches 90%.

[0042] Example 2

[0043] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0044] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and molybdenum sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 170 g / L and the molar ratio of Mo:Ti is 0.35:1.

[0045] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 110°C;

[0046] S3, hydrolysis: under stirring at 1000 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.0 mL / min, and the temperature of the reactor was kept constant at 110°C. The feeding time was 12 h, and the hydrolysis reaction was terminated when the feeding was completed;

[0047] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying at 120° C. for 10 h to obtain molybdenum metal-doped metatitanic acid (HTOMo);

[0048] S5. Preparation of sodium titanate: Sodium acetate and molybdenum metal-doped metatitanic acid (HTOMo) were evenly mixed in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, heated to 800°C at a heating rate of 5°C / min, kept warm for 15 hours, and then naturally cooled to obtain molybdenum metal-doped sodium titanate (NTOMo).

[0049] Through testing, the molybdenum metal-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the molybdenum metal-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 204 mAh / g at 100 mA / g, a specific capacity of 120 mAh / g at 2000 mA / g, and a capacity retention rate of 58.8%; after 200 cycles at 200 mA / g, the specific capacity is still 145 mAh / g, and the capacity retention rate reaches 76%.

[0050] Example 3

[0051] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0052] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and gold sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 200 g / L and the molar ratio of Au:Ti is 0.01:1.

[0053] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 90°C;

[0054] S3, hydrolysis: under stirring at 1100 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.3 mL / min, and the temperature of the reactor was kept constant at 90°C. The feeding time was 6 h, and the hydrolysis reaction was terminated when the feeding was completed;

[0055] S4. Preparation of metatitanic acid: Cool the hydrolyzed slurry to room temperature, wash with water, and dry at 120° C. for 10 h to obtain gold-doped metatitanic acid (HTOAu);

[0056] S5. Preparation of sodium titanate: Sodium carbonate and metal-doped metatitanic acid (HTOAu) were mixed evenly in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, heated to 850°C at a heating rate of 5°C / min, kept at this temperature for 8 hours, and then naturally cooled to obtain gold-doped sodium titanate (NTOAu).

[0057] Through testing, the gold-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the gold-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 234 mAh / g at 100 mA / g, a specific capacity of 137 mAh / g at 2000 mA / g, and a capacity retention rate of 58.5%; after 200 cycles at 200 mA / g, the specific capacity is still 160 mAh / g, and the capacity retention rate reaches 80%.

[0058] Example 4

[0059] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0060] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and potassium sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 210 g / L and the molar ratio of K:Ti is 0.5:1.

[0061] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 100°C;

[0062] S3, hydrolysis: under stirring at 1400 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.4 mL / min, and the temperature of the reactor was kept constant at 100°C. The feeding time was 3 h. The hydrolysis reaction ended when the feeding was completed;

[0063] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying at 120° C. for 10 h to obtain potassium metal-doped metatitanic acid (HTOK);

[0064] S5. Preparation of sodium titanate: Sodium oxalate and potassium metal-doped metatitanic acid (HTOK) were uniformly mixed in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, and heated to 950°C at a heating rate of 5°C / min. The mixture was kept at this temperature for 5 h, and then naturally cooled to obtain potassium metal-doped sodium titanate (NTOK).

[0065] Through testing, the potassium metal-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the potassium metal-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 140 mAh / g at 100 mA / g, a specific capacity of 89 mAh / g at 2000 mA / g, and a capacity retention rate of 63.6%; after 200 cycles at 200 mA / g, the specific capacity is still 111 mAh / g, and the capacity retention rate reaches 72%.

[0066] Example 5

[0067] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0068] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and copper sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 220 g / L and the molar ratio of Cu:Ti is 0.44:1.

[0069] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 85°C;

[0070] S3, hydrolysis: under stirring at 1050 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.5 mL / min, and the temperature of the reactor was kept constant at 85°C. The feeding time was 1 h, and the hydrolysis reaction was terminated when the feeding was completed;

[0071] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying at 120° C. for 10 h to obtain copper-doped metatitanic acid (HTOCu);

[0072] S5. Preparation of sodium titanate: Sodium oxide and copper-doped metatitanic acid (HTOCu) were mixed evenly in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, and heated to 880°C at a heating rate of 5°C / min. The mixture was kept at this temperature for 7 hours and then naturally cooled to obtain copper-doped sodium titanate (NTOCu).

[0073] Through testing, the copper metal-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the copper metal-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 185 mAh / g at 100 mA / g, a specific capacity of 127 mAh / g at 2000 mA / g, and a capacity retention rate of 68.6%; after 200 cycles at 200 mA / g, the specific capacity is still 139 mAh / g, and the capacity retention rate reaches 80%.

[0074] Example 6

[0075] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0076] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and zirconium sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 190 g / L and the molar ratio of Zr:Ti is 0.08:1.

[0077] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 95°C;

[0078] S3, hydrolysis: under stirring at 1050 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.1 mL / min, and the temperature of the reactor was kept constant at 95°C. The feeding time was 10 h, and the hydrolysis reaction was terminated when the feeding was completed;

[0079] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying at 120° C. for 10 h to obtain zirconium metal-doped metatitanic acid (HTOZr);

[0080] S5. Preparation of sodium titanate: Sodium peroxide and zirconium metal-doped metatitanic acid (HTOZr) were mixed evenly in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, and heated to 850°C at a heating rate of 5°C / min. The mixture was kept at this temperature for 13 hours, and then naturally cooled to obtain zirconium metal-doped sodium titanate (NTOZr).

[0081] Through testing, the zirconium metal-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the zirconium metal-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 174 mAh / g at 100 mA / g, a specific capacity of 131 mAh / g at 2000 mA / g, and a capacity retention rate of 75.3%; after 200 cycles at 200 mA / g, the specific capacity is still 126 mAh / g, and the capacity retention rate reaches 75%.

[0082] Example 7

[0083] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0084] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and magnesium sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 230 g / L and the molar ratio of Mg:Ti is 0.27:1.

[0085] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 105°C;

[0086] S3, hydrolysis: under stirring at 1100 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.2 mL / min, and the temperature of the reactor was kept constant at 105 ° C. The feeding time was 7 h. The hydrolysis reaction was terminated when the feeding was completed;

[0087] S4. Preparation of metatitanic acid: Cool the hydrolyzed slurry to room temperature, wash with water, and dry at 120° C. for 10 h to obtain magnesium metal-doped metatitanic acid (HTOMg);

[0088] S5. Preparation of sodium titanate: Sodium hydroxide and magnesium metal-doped metatitanic acid (HTOMg) are uniformly mixed in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, heated to 800°C at a heating rate of 5°C / min, kept at this temperature for 15 hours, and then naturally cooled to obtain magnesium metal-doped sodium titanate (NTOMg).

[0089] Through testing, the magnesium metal-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the magnesium metal-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 193 mAh / g at 100 mA / g, a specific capacity of 129 mAh / g at 2000 mA / g, and a capacity retention rate of 66.8%; after 200 cycles at 200 mA / g, the specific capacity is still 133 mAh / g, and the capacity retention rate reaches 80%.

[0090] Example 8

[0091] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0092] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and niobium sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 185 g / L and the molar ratio of Nb:Ti is 0.4:1.

[0093] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 80°C;

[0094] S3, hydrolysis: under stirring at 1200 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.3 mL / min, and the temperature of the reactor was kept constant at 80°C. The feeding time was 6 h, and the hydrolysis reaction was terminated when the feeding was completed;

[0095] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying at 120° C. for 10 h to obtain niobium metal-doped metatitanic acid (HTONb);

[0096] S5. Preparation of sodium titanate: Sodium acetate and niobium metal-doped metatitanic acid (HTONb) were uniformly mixed in a sodium to titanium molar ratio of 2:3, and calcined under an argon atmosphere. The temperature was raised to 900°C at a heating rate of 5°C / min, kept at this temperature for 6 hours, and then naturally cooled to obtain niobium metal-doped sodium titanate (NTONb).

[0097] Testing revealed that the niobium-doped metatitanic acid prepared in step S4 was micron-spheres with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns. The niobium-doped sodium titanate negative electrode material prepared in step S5 had a specific capacity of 225 mAh / g at 100 mA / g, a specific capacity of 141 mAh / g at 2000 mA / g, and a capacity retention rate of 62.7%. After 200 cycles at 200 mA / g, the specific capacity was still 147 mAh / g, with a capacity retention rate of 77%.

[0098] Example 9

[0099] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0100] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and calcium sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 180 g / L and the molar ratio of Ca:Ti is 0.16:1.

[0101] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 90°C;

[0102] S3, hydrolysis: under stirring at 1300 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.4 mL / min, and the temperature of the reactor was kept constant at 90°C. The feeding time was 5 h, and the hydrolysis reaction was terminated when the feeding was completed;

[0103] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying at 120° C. for 10 h to obtain calcium metal-doped metatitanic acid (HTOCa);

[0104] S5. Preparation of sodium titanate: Sodium oxalate and calcium metal-doped metatitanic acid (HTOCa) were uniformly mixed in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, and heated to 950°C at a heating rate of 5°C / min. The mixture was kept at this temperature for 5 h, and then naturally cooled to obtain calcium metal-doped sodium titanate (NTOCa).

[0105] Through testing, the calcium metal-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the calcium metal-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 135 mAh / g at 100 mA / g, a specific capacity of 92 mAh / g at 2000 mA / g, and a capacity retention rate of 68.1%; after 200 cycles at 200 mA / g, the specific capacity is still 115 mAh / g, and the capacity retention rate reaches 70%.

[0106] Example 10

[0107] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0108] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and vanadium sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 235 g / L, and the molar ratio of V:Ti is 0.22:1.

[0109] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 110°C;

[0110] S3, hydrolysis: under stirring at 1400 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 1.2 mL / min, and the temperature of the reactor was kept constant at 110°C. The feeding time was 9 h, and the hydrolysis reaction was terminated when the feeding was completed;

[0111] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying at 120° C. for 10 h to obtain vanadium-doped metatitanic acid (HTOV);

[0112] S5. Preparation of sodium titanate: Sodium carbonate and vanadium-doped metatitanic acid (HTOV) were mixed evenly in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, and heated to 850°C at a heating rate of 5°C / min. The mixture was kept at this temperature for 12 hours, and then naturally cooled to obtain vanadium-doped sodium titanate (NTOV).

[0113] Through testing, the vanadium metal-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the vanadium metal-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 163 mAh / g at 100 mA / g, a specific capacity of 99 mAh / g at 2000 mA / g, and a capacity retention rate of 60.7%; after 200 cycles at 200 mA / g, the specific capacity is still 125 mAh / g, and the capacity retention rate reaches 75%.

[0114] Example 11

[0115] A method for preparing a metal-doped sodium titanate negative electrode material, the preparation method comprising the following steps:

[0116] S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and strontium sulfate in water to form a hydrolysis solution, wherein the concentration of the hydrolysis solution is 205 g / L and the molar ratio of Sr:Ti is 0.05:1.

[0117] S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reactor and preheat it to 80°C;

[0118] S3, hydrolysis: under stirring at 1300 rpm, the hydrolysis solution was uniformly added to the reactor at a feeding rate of 13 mL / min, and the temperature of the reactor was kept constant at 80°C. The feeding time was 8 h, and the hydrolysis reaction was terminated when the feeding was completed;

[0119] S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying at 120° C. for 10 h to obtain strontium metal-doped metatitanic acid (HTOSr);

[0120] S5. Preparation of sodium titanate: Sodium hydroxide and strontium metal-doped metatitanic acid (HTOSr) are uniformly mixed in a sodium to titanium molar ratio of 2:3, calcined under an argon atmosphere, heated to 800°C at a heating rate of 5°C / min, kept warm for 13 hours, and then naturally cooled to obtain strontium metal-doped sodium titanate (NTOSr).

[0121] Through testing, the strontium metal-doped metatitanic acid prepared in step S4 is a micron sphere with uniform particle size, smooth and dense surface, and a particle size of 5-10 microns; the strontium metal-doped sodium titanate negative electrode material prepared in step S5 has a specific capacity of 182 mAh / g at 100 mA / g, a specific capacity of 118 mAh / g at 2000 mA / g, and a capacity retention rate of 64.8%; after 200 cycles at 200 mA / g, the specific capacity is still 148 mAh / g, and the capacity retention rate reaches 84%.

[0122] Further analysis with the attached figures:

[0123] Figure 1 This is the SEM spectrum of the hydrolysis product HTO-Al in Example 1 of the present invention; Figure 2 This is the XRD spectrum of the hydrolysis product HTO-Al in Example 1 of the present invention. It can be seen that HTO-Al is a micron sphere with uniform particle size, smooth and dense surface, and the overall particle size is about 5-10 microns, corresponding to the peak of anatase titanium dioxide.

[0124] Figure 3 This is the SEM spectrum of NTO-Al prepared in Example 1 of the present invention; Figure 4 This is the XRD spectrum of NTO-Al prepared in Example 1 of the present invention; Figure 5 The mapping spectrum of NTO-Al prepared in Example 1 of the present invention. It can be seen that NTO-Al is a relatively solid micron sphere with nanorods grown on the surface. The overall particle size is about 5-10 microns and the sphericity is intact; XRD mainly corresponds to Na2Ti3O7 and Na2Ti6O 13 The mapping diagram shows uniform Al doping.

[0125] Figure 6 From the rate performance diagram of the NTO-Al negative electrode prepared in Example 1 of the present invention, it can be seen that the specific capacity of NTO-Al is 153 mAh / g at 100 mA / g, the specific capacity is 114 mAh / g at 2000 mA / g, and the capacity retention rate is 74.5%.

[0126] Figure 7 This is a performance graph of the NTO-Al negative electrode prepared in Example 1 of the present invention after 200 cycles at 200 mA / g. It can be seen that the specific capacity of the NTO-Al negative electrode is still 123 mAh / g after 200 cycles at 200 mA / g, and the capacity retention rate is as high as 90%.

[0127] In summary, the present invention uses a sulfate solution and a titanyl sulfate solution mixed with metal ions for hydrolysis to obtain metatitanic acid (HTO) uniformly doped with trace metal elements, and then directly calcining the metatitanic acid and a sodium source to synthesize heterogeneous ion-regulated sodium titanate. The present invention simplifies the process, and doping directly during the hydrolysis process can reduce additional doping steps, and reduces the steps of converting metatitanic acid into titanium dioxide, thereby reducing production costs and energy consumption, simplifying the operating procedures, and facilitating repeated experiments and scale-up. In addition, doping during the hydrolysis process can make the metal ions more evenly distributed in the lattice of metatitanic acid, thereby improving the quality of the sodium titanate product. In addition, through the action of metal ions, the metatitanic acid generated by hydrolysis is a micron sphere with uniform particle size, smooth and dense surface, and the sodium titanate prepared after calcination can better maintain its spherical shape, thereby improving its performance in electrochemical energy storage devices.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a metal-doped sodium titanate negative electrode material, the method comprising the following steps: S1. Preparation of hydrolysis solution: dissolving titanyl sulfate and metal A sulfate in water to form a hydrolysis solution, wherein the molar ratio of A:Ti is 0.01-0.5:1; S2. Preheating of base liquid: Take an appropriate amount of deionized water into the reaction kettle and preheat it to 80℃-110℃; S3, hydrolysis: under stirring, the hydrolysis solution is added to the reactor at a uniform rate, and the temperature of the system in the reactor is kept constant. The hydrolysis reaction ends when the feeding is completed; S4. Preparation of metatitanic acid: Cooling the hydrolyzed slurry to room temperature, washing with water, and drying to obtain metal-doped metatitanic acid; S5. Preparation of sodium titanate: uniformly mixing a sodium source and metal-doped metatitanic acid in a sodium to titanium molar ratio of 2:3, calcining under an argon atmosphere, and then naturally cooling to obtain metal-doped sodium titanate; In step S1, A is one or a combination of K, Au, Cu, Zr, Mg, Nb, Ca, V, Sr, Mo, and Al.

2. The method for preparing the metal-doped sodium titanate negative electrode material according to claim 1, characterized in that: The concentration of the hydrolysis solution in step S1 is 170-240 g / L.

3. The method for preparing the metal-doped sodium titanate negative electrode material according to claim 1, characterized in that: The stirring speed in step S3 is 1000-1400 rpm.

4. The method for preparing a metal-doped sodium titanate negative electrode material according to claim 1, characterized in that: The feeding rate of the hydrolysis solution in step S3 is 1.0-5 mL / min.

5. The method for preparing the metal-doped sodium titanate negative electrode material according to claim 1, characterized in that: During the addition process in step S3, the system temperature is kept constant at 80°C-110°C.

6. The method for preparing a metal-doped sodium titanate negative electrode material according to claim 1, characterized in that: The feeding time of the titanyl sulfate solution in step S3 is 1-12 hours.

7. The method for preparing a metal-doped sodium titanate negative electrode material according to claim 1, characterized in that: In step S4, the drying temperature is 120° C. and the drying time is 10 h.

8. The method for preparing a metal-doped sodium titanate negative electrode material according to claim 1, characterized in that: In step S5, the sodium source is one or more of sodium acetate, sodium carbonate, sodium hydroxide, sodium oxalate, sodium oxide, and sodium peroxide.

9. The method for preparing a metal-doped sodium titanate negative electrode material according to any one of claims 1 to 8, characterized in that: The calcination in step S5 is as follows: heating to 800-950° C. at a heating rate of 5° C. / min and keeping the temperature for 5-15 hours.

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