Sodium-ion battery and preparation method of sodium-ion battery

Abstract

The invention provides a sodium ion battery and a preparation method of the sodium ion battery, and relates to the technical field of batteries. The preparation method of the negative electrode material of the sodium ion battery comprises the following steps: treating titanium-containing blast furnace slag to obtain metatitanic acid; metatitanic acid is treated, titanate is obtained, and the titanate has the nanoflower morphology; titanate is treated to obtain titanium dioxide, and the titanium dioxide has a nanoflower morphology and has oxygen vacancies. According to the negative electrode material prepared by the preparation method of the scheme, the migration rate of sodium ions can be improved, the specific capacity and the cycling stability of the negative electrode material are improved, and the negative electrode material has relatively good rate capability; and the negative electrode material is prepared by taking the titanium-containing blast furnace slag as a raw material, so that the cost of the raw material can be greatly reduced, and the environmental problem caused by solid waste accumulation can be solved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a sodium-ion battery and a method for preparing a sodium-ion battery. Background Technology

[0002] With the urgent global demand for renewable energy, developing low-cost energy storage technologies has become a top priority. However, my country's lithium resources are relatively scarce, and the high difficulty of extraction leads to high lithium resource costs, which in turn increases the manufacturing cost of lithium-ion batteries. Among various electrochemical energy storage systems, sodium-ion batteries are considered one of the most ideal candidates to replace lithium-ion batteries in large-scale static energy storage due to the extremely abundant, widely distributed, and inexpensive nature of sodium resources.

[0003] However, in related technologies, the negative electrode materials of sodium-ion batteries are difficult to effectively accommodate sodium ions with large ionic radii. During sodium ion insertion / extraction, significant lattice distortion energy must be overcome, resulting in a slow sodium ion migration rate during charge and discharge, thus affecting the reversible capacity of the sodium-ion battery. Furthermore, in related technologies, the negative electrode material undergoes substantial volume changes during cycling, which can easily lead to negative electrode material failure, resulting in poor cycle stability of the sodium-ion battery.

[0004] Therefore, new methods and strategies are needed to improve the problems existing in related technologies. Summary of the Invention

[0005] This application provides a sodium-ion battery and a method for preparing a sodium-ion battery, which can improve the migration rate of sodium ions, effectively buffer the volume strain generated during sodium ion insertion / extraction, have high cycle stability, help improve the reversible capacity of sodium-ion batteries, and help reduce the manufacturing cost of sodium-ion batteries.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, a method for preparing a negative electrode material for a sodium-ion battery is provided. The method includes: firstly, treating titanium-containing blast furnace slag to obtain metatitanic acid; then, treating the metatitanic acid to obtain titanate, the titanate having a nanoflower morphology; and finally, treating the titanate to obtain titanium dioxide.

[0008] The titanium dioxide prepared by the above method exhibits a nanoflower morphology and a three-dimensional nanoflower structure. As a negative electrode material for sodium-ion batteries, the nanoflower-morphological titanium dioxide effectively increases the specific surface area of ​​the negative electrode material, providing abundant active sites and shorter diffusion paths for sodium ions, thus enhancing the migration rate of sodium ions. Furthermore, the nanoflower-morphological titanium dioxide can effectively buffer the volumetric strain generated during sodium ion insertion / extraction, preventing pulverization of the negative electrode material and exhibiting high cycle stability. When the negative electrode material prepared by the above method is applied to sodium-ion batteries, the negative electrode material can maintain a stable structure during the charge and discharge process of the sodium-ion battery, which is beneficial to improving the cycle stability of the sodium-ion battery, ensuring a long cycle life, and contributing to improving the reversible capacity of the sodium-ion battery.

[0009] The titanium dioxide prepared by the above method also possesses oxygen vacancies. Oxygen vacancies arise from the detachment of oxygen atoms from the crystal lattice of metal oxides or other oxygen-containing compounds, resulting in the absence of oxygen atoms and the formation of vacancies. The presence of oxygen vacancies in the titanium dioxide in the anode material can improve the intrinsic electronic conductivity of the anode material, reduce the resistance to sodium ion migration, and thus increase the migration rate of sodium ions, contributing to an increase in the specific capacity of the anode material.

[0010] In summary, preparing titanium dioxide with nanoflower morphology and oxygen vacancies as an anode material for sodium-ion batteries can improve the migration rate of sodium ions, increase the specific capacity and cycle stability of the anode material, and exhibit better rate performance. Furthermore, using titanium-containing blast furnace slag as a raw material to prepare the aforementioned anode material can significantly reduce raw material costs, which is beneficial for addressing the environmental problems caused by solid waste accumulation and aligns with the green and sustainable development strategy. The aforementioned process for preparing anode materials using titanium-containing blast furnace slag as a raw material is also relatively simple.

[0011] When the aforementioned negative electrode materials are applied to sodium-ion batteries, they can ensure long cycle life and high reversible capacity, and also help reduce the manufacturing cost of sodium-ion batteries.

[0012] In one possible implementation of the first aspect, titanium-containing blast furnace slag is treated to obtain metatitanic acid, including:

[0013] First, titanium-containing blast furnace slag is mixed with concentrated sulfuric acid and reacted to prepare the first product. In this way, titanium oxides in the titanium-containing blast furnace slag can react with concentrated sulfuric acid to generate titanium oxysulfate, thus enabling the extraction of titanium resources from the blast furnace slag. The first product includes titanium oxysulfate.

[0014] The first product is then dissolved to obtain a first acid leaching solution, which includes titanium oxysulfate. Dissolving the first product allows the titanium oxysulfate in the first product to enter the first acid leaching solution. For example, the first product can be dissolved under heating conditions, which can effectively increase the leaching rate of titanium oxysulfate.

[0015] Next, the pH of the first acid leaching solution is adjusted to obtain the first solution, with a pH of 1.8–2.5. It should be noted that if the pH of the first solution is too high, the ferric sulfate and magnesium sulfate in the first solution are also prone to hydrolysis, and the hydrolysis products, if incorporated into the metatitanic acid, will affect the purity of the metatitanic acid. If the pH of the first solution is too low, the hydrolysis efficiency of titanium oxysulfate is low, resulting in a low extraction rate of metatitanic acid. Therefore, maintaining the pH of the first solution at 1.8–2.5 is beneficial for improving the hydrolysis efficiency of titanium oxysulfate and also helps to ensure the purity of the metatitanic acid.

[0016] Finally, the first solution is heated to a first preset temperature to hydrolyze titanium oxysulfate into metatitanic acid. The first solution at the first preset temperature can promote the hydrolysis reaction of titanium oxysulfate.

[0017] In one possible implementation of the first aspect, the mass ratio of titanium-containing blast furnace slag to concentrated sulfuric acid is 1:(1.3-1.4). It should be understood that when the mass ratio of titanium-containing blast furnace slag to concentrated sulfuric acid is greater than 1:1.3, the amount of concentrated sulfuric acid mixed with the titanium-containing blast furnace slag is insufficient, making it difficult to react fully with the slag, resulting in insufficient extraction of titanium oxysulfate. When the mass ratio of titanium-containing blast furnace slag to concentrated sulfuric acid is less than 1:1.4, the amount of concentrated sulfuric acid mixed with the slag is excessive. This leads to higher preparation costs due to excessive use of concentrated sulfuric acid, and also results in an excessively low pH value of the first product. Subsequent preparation operations requiring a higher pH value necessitate the addition of excessive alkaline particles or alkaline solutions, further increasing preparation costs.

[0018] Therefore, by having a suitable mass ratio between titanium-containing blast furnace slag and concentrated sulfuric acid, it is possible to ensure that concentrated sulfuric acid and titanium-containing blast furnace slag react fully while helping to reduce the cost of preparing titanium dioxide from titanium-containing blast furnace slag.

[0019] In one possible implementation of the first aspect, the first product is dissolved by mixing a first predetermined mass of the first product with a first predetermined volume of dilute sulfuric acid solution. The molar concentration of the dilute sulfuric acid solution is 0.3 mol / L to 0.8 mol / L, and the ratio of the first predetermined mass to the first predetermined volume is (1 / 7 to 1 / 5) mg / ml.

[0020] On the one hand, it allows the titanium oxysulfate in the first product to dissolve in dilute sulfuric acid solution; on the other hand, the dilute sulfuric acid solution can dilute the first product, giving the first acid leaching solution a higher pH value relative to the first product, facilitating subsequent extraction of metatitanic acid. Under certain conditions, the dilute sulfuric acid solution can react with the titanium oxide in the first product to generate titanium oxysulfate, which then dissolves in the dilute sulfuric acid solution, thus enabling further extraction of titanium resources from titanium-containing blast furnace slag.

[0021] In one possible implementation of the first aspect, adjusting the pH of the first acid leaching solution can be achieved by mixing at least one of sodium hydroxide and deionized water with the first acid leaching solution, thereby raising the pH of the first acid leaching solution. Specifically, deionized water can be used to adjust the pH of the first acid leaching solution by diluting it, and sodium hydroxide can react with hydrogen ions in the first acid leaching solution to achieve pH adjustment.

[0022] For example, sodium hydroxide can be mixed with the first acid leaching solution; or, deionized water can be mixed with the first acid leaching solution; or, both sodium hydroxide and deionized water can be mixed with the first acid leaching solution.

[0023] In one possible implementation of the first aspect, the first preset temperature is 105°C to 120°C. At the first preset temperature, the first solution can promote the hydrolysis reaction of titanium oxysulfate to generate metatitanic acid.

[0024] In one possible implementation of the first aspect, metatitanic acid is treated to obtain titanate, comprising the following steps: first, a second predetermined mass of metatitanic acid is mixed with a second predetermined volume of sodium hydroxide solution and stirred to form a mixture; then, the mixture is heated to a second predetermined temperature and maintained at the second predetermined temperature for a first predetermined time, allowing the substances in the mixture to react and obtain titanate. The reaction between metatitanic acid and sodium hydroxide to form titanate is characterized by a tendency for the morphology of titanate to change under alkaline conditions; furthermore, the heating of the mixture can further promote the reaction between metatitanic acid and sodium hydroxide.

[0025] In one possible implementation of the first aspect, the molar concentration of the sodium hydroxide solution is 6 mol / L to 6.8 mol / L. With a suitable molar concentration of sodium hydroxide solution, the mixture has a suitable pH value, allowing titanate to grow into a sheet-like structure, which can then curl to form a nanoflower structure. When the molar concentration of the sodium hydroxide solution is too high, the pH value of the mixture is too high, causing the sheet-like structure of titanate to excessively curl and form a linear structure, making it easier for titanate to transform into a nanowire morphology. When the molar concentration of the sodium hydroxide solution is too low, the pH value of the mixture is insufficient, making it difficult for irregularly shaped particulate metatitanic acid to transform into a sheet-like structure.

[0026] The ratio of the second preset mass to the second preset volume is 20 mg / mL to 30 mg / mL. It should be understood that when there is too little sodium hydroxide solution, it cannot react fully with metatitanic acid; when there is too much sodium hydroxide solution, the pH value of the titanate produced by the reaction is too high, which affects subsequent operations (for example, when it is necessary to lower the pH value of the titanate, the titanate needs to be rinsed too many times, which affects the overall preparation efficiency).

[0027] Therefore, by setting the ratio of the second preset mass to the second preset volume to 20 mg / mL to 30 mg / mL, it is possible to ensure that metatitanic acid can react fully with sodium hydroxide, and also to avoid the pH value of the generated titanate being too high, thereby reducing the need for rinsing titanate.

[0028] In one possible implementation of the first aspect, the second preset temperature is 145℃~155℃, and the first preset duration is 34 hours~40 hours. A high-temperature environment can more effectively promote the change in titanate morphology.

[0029] In one possible implementation of the first aspect, titanium dioxide is obtained by treating a titanate, comprising the following steps: First, the titanate is mixed with a dilute hydrochloric acid solution, and the titanate reacts with the dilute hydrochloric acid to obtain nano-flower-like metatitanic acid; then, the nano-flower-like metatitanic acid is heated in an inert gas to a third preset temperature and held at the third preset temperature for a second preset time to obtain titanium dioxide. The nano-flower-like metatitanic acid can decompose into titanium dioxide under certain temperature conditions, giving the titanium dioxide a nano-flower morphology. Furthermore, when the generated titanium dioxide is heated in an inert gas, oxygen ions in the titanium dioxide lattice gain sufficient energy due to thermal excitation to detach from lattice sites, forming oxygen vacancies.

[0030] In one possible implementation of the first aspect, the molar concentration of the dilute hydrochloric acid solution is 0.08 mol / L to 0.15 mol / L.

[0031] It should be understood that when the molar concentration of the dilute hydrochloric acid solution is too low, titanates are unlikely to react fully with the hydrochloric acid to form metatitanic acid; when the molar concentration of the dilute hydrochloric acid solution is too high, chloride ions in the hydrochloric acid solution easily combine with titanium ions in the titanate to form complexes, affecting the yield of metatitanic acid. Therefore, by maintaining an appropriate molar concentration of the dilute hydrochloric acid solution, it is possible to ensure that the titanates react fully with the hydrochloric acid to form metatitanic acid, thus guaranteeing the yield of metatitanic acid.

[0032] In one possible implementation of the first aspect, the third preset temperature is 550℃~620℃, and the second preset duration is 2 hours~2.5 hours. By heating the nano-flower-like metatitanic acid at the third preset temperature, the reaction of the nano-flower-like metatitanic acid can be promoted to generate titanium dioxide and water vapor; when the generated titanium dioxide is heated to the third preset temperature in an inert gas, oxygen ions in the titanium dioxide lattice are more easily detached from the lattice sites to form oxygen vacancies.

[0033] Secondly, a negative electrode material for a sodium-ion battery is provided, which is prepared by the method described in the first aspect for preparing the negative electrode material for a sodium-ion battery. The beneficial effects of the negative electrode material for the sodium-ion battery can be found in the first aspect and any possible implementation thereof, and will not be repeated here.

[0034] In one possible implementation of the second aspect, the method for preparing the negative electrode includes: first, uniformly dispersing titanium dioxide powder, carbon black conductive agent, and polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP) to prepare an electrode slurry; then, coating the electrode slurry onto a conductive substrate; and finally, drying the conductive substrate coated with the electrode slurry in a vacuum to obtain the negative electrode.

[0035] Carbon black possesses a high specific surface area and excellent electrical conductivity. By mixing carbon black conductive agent with PVDF and adding it to NMP solvent, the electronic conductivity of electrode materials can be significantly improved. Carbon black particles can form a conductive network in PVDF, reducing internal resistance and improving the utilization rate of active materials, thereby contributing to enhanced rate performance and cycle stability of ion batteries.

[0036] Thirdly, a method for preparing a sodium-ion battery is provided, the method comprising preparing a negative electrode and preparing a positive electrode, wherein a sodium metal sheet is prepared as the positive electrode; the negative electrode comprises a negative electrode material, which is prepared by the method for preparing the negative electrode material of the sodium-ion battery provided in the first aspect above.

[0037] It is understandable that the beneficial effects that the sodium-ion battery preparation method can achieve can be referred to in the first aspect and any of its possible implementation methods, and will not be repeated here.

[0038] Fourthly, a sodium-ion battery is provided, comprising a positive electrode and a negative electrode. The positive electrode comprises a sodium metal sheet, and the negative electrode comprises the negative electrode material of the sodium-ion battery provided in the second aspect above. It is understood that the beneficial effects achievable by the sodium-ion battery can be referred to in the second aspect and any possible implementation thereof, and will not be elaborated here.

[0039] In one possible implementation of the fourth aspect, the loading of titanium dioxide in the negative electrode is 1.0 mg / cm³. 2~1.5mg / cm 2 .

[0040] It should be noted that the titanium dioxide loading refers to the mass of titanium dioxide per unit area of ​​the negative electrode. Excessive titanium dioxide loading hinders electrolyte wetting of the negative electrode, making the structure of the negative electrode material easily damaged during the charge and discharge process of the sodium-ion battery, thus affecting the cycle stability of the sodium-ion battery. Conversely, insufficient titanium dioxide loading affects the insertion of sodium ions into the negative electrode, thus impacting the specific capacity of the sodium-ion battery.

[0041] The titanium dioxide loading was 1.0 mg / cm³. 2 ~1.5mg / cm 2 This facilitates the wetting of the negative electrode by the electrolyte and allows sodium ions to be inserted and extracted into the negative electrode, thereby enhancing the cycle stability and increasing the specific capacity of the sodium-ion battery.

[0042] In one possible implementation of the fourth aspect, the electrolyte of the sodium-ion battery is a chlorinated ester electrolyte, comprising sodium perchlorate (NaClO4), fluoroethylene carbonate (FEC), propylene carbonate (PC), and ethylene carbonate (EC). NaClO4 provides high ion mobility in the electrolyte, enhancing charge transport efficiency; the synergistic effect of FEC and EC suppresses overcharging and thermal runaway; the combination of PC and FEC supports low-temperature operation; the combination of EC and FEC ensures high-temperature stability of the electrolyte; and the production process of FEC is relatively mature, with a lower price than similar additives (such as vitamin C).

[0043] In one possible implementation of the fourth aspect, the molar concentration of NaClO4 in the electrolyte is 0.8 mol / L to 1.2 mol / L. For example, the molar concentration of NaClO4 in the electrolyte can be 0.8 mol / L, 0.9 mol / L, 1 mol / L or 1.2 mol / L.

[0044] It should be understood that when the concentration of NaClO4 is too high, it will increase the viscosity of the electrolyte, hinder the migration of sodium ions, and reduce the ionic conductivity, thereby affecting the rate performance and charge / discharge efficiency of the sodium-ion battery. On the other hand, when the concentration of NaClO4 is too low, it will result in insufficient number of free sodium ions in the electrolyte, a decrease in the migration rate of sodium ions, and an increase in the internal resistance of the sodium-ion battery, thereby reducing the rate performance and charge / discharge efficiency of the sodium-ion battery.

[0045] Therefore, by maintaining the molar concentration of NaClO4 in the electrolyte at 0.8 mol / L to 1.2 mol / L, the viscosity of the electrolyte can be avoided from being too high, ensuring the migration rate of sodium ions, and thus ensuring the rate performance and charge / discharge efficiency of the sodium-ion battery.

[0046] In one possible implementation of the fourth aspect, the mass percentage of FEC in the electrolyte is 3% to 8%, for example, 3%, 4%, 5%, 6%, 7% or 8% of the mass percentage of FEC in the electrolyte.

[0047] It should be understood that when the mass percentage of FEC in the electrolyte is too low, carbonate solvents (such as EC) are prone to decomposition and gas production, which can cause sodium-ion batteries to expand or experience capacity decay, thus shortening the cycle life of sodium-ion batteries. When the mass percentage of FEC in the electrolyte is too high, FEC may excessively consume the electrolyte, resulting in an excessively thick solid electrolyte interphase (SEI) film formed on the negative electrode surface, which can hinder sodium ion transport.

[0048] Therefore, by maintaining a FEC mass percentage of 3% to 8% in the electrolyte, the migration and transport rate of sodium ions can be guaranteed, which is also beneficial to ensuring the cycle life of sodium-ion batteries.

[0049] In one possible implementation of the fourth aspect, the volume ratio of PC to EC in the electrolyte is 1:1, which helps to suppress the generation of side reactions, such as avoiding excessive SEI film thickness (increased impedance) caused by excessive EC or continuous solvent decomposition (gas generation) caused by excessive PC. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of a sodium-ion battery according to some embodiments of this application;

[0051] Figure 2 According to Figure 1 An exploded view of a sodium-ion battery is shown.

[0052] Figure 3 A schematic diagram of the microstructure of titanium dioxide prepared by the preparation methods of some embodiments of this application;

[0053] Figure 4 A schematic diagram of the microstructure of nanoflower-shaped metatitanic acid prepared by the preparation methods of some embodiments of this application;

[0054] Figure 5 This is a schematic diagram of the CV curve of the negative electrode of a sodium-ion battery according to some embodiments of this application;

[0055] Figure 6 This is a schematic diagram of the specific capacity test of the negative electrode of a sodium-ion battery according to some embodiments of this application;

[0056] Figure 7 This is a schematic diagram of the CV curve of the negative electrode of a sodium-ion battery according to some other embodiments of this application;

[0057] Figure 8 This is a schematic diagram of the specific capacity test of the negative electrode of a sodium-ion battery according to other embodiments of this application.

[0058] Figure Labels

[0059] 100. Lithium-ion battery; 1. Negative electrode shell; 2. Spring; 3. Gasket; 4. Negative electrode; 5. Separator; 6. Positive electrode; 7. Positive electrode shell. Detailed Implementation

[0060] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this embodiment, unless otherwise stated, "a plurality of" means two or more.

[0061] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0062] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0063] Sodium-ion batteries are among the most common types of ion batteries. Based on their external structure, sodium-ion batteries can be categorized into button batteries, cylindrical batteries, and prismatic batteries. For ease of explanation, the following examples use button batteries as an example, but this should not be construed as a limitation of this application. Button batteries can be used in small electronic devices such as watches, calculators, and remote controls.

[0064] Reference Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the structure of a sodium-ion battery 100 according to some embodiments of this application; Figure 2 According to Figure 1The diagram shows an exploded view of a sodium-ion battery 100. The sodium-ion battery 100 may include a negative electrode shell 1, a spring 2, a gasket 3, a negative electrode 4, a separator 5, a positive electrode 6, and a positive electrode shell 7, all stacked together. The sodium-ion battery may also include an electrolyte. Both the negative electrode 4 and the positive electrode 6 are in contact with the electrolyte. The electrolyte acts as a medium for ion transport, connecting the positive electrode 6 and the negative electrode 4, thus establishing a conductive channel between the positive electrode 6 and the negative electrode 4 of the sodium-ion battery 100. For example, the spring 2 may be a stainless steel spring, the gasket 3 may be a stainless steel gasket, and the separator 5 may be a glass fiber disc.

[0065] Common ion batteries also include lithium-ion batteries. However, my country's lithium resources are relatively scarce, and the high difficulty of mining leads to high lithium resource costs, which in turn increases the manufacturing cost of lithium-ion batteries. In contrast, my country has relatively abundant and widely distributed sodium resources at a lower cost. Therefore, given the urgent need for low-cost energy storage technologies, sodium-ion batteries are considered one of the most ideal candidates to replace lithium-ion batteries in large-scale static energy storage applications, due to the abundant sodium reserves.

[0066] However, sodium ions have a large ionic radius. The high molar mass of sodium-ion batteries presents inherent challenges to their reversible storage and rapid transport in anode materials. Currently, research on anode materials for sodium-ion batteries mainly focuses on intercalation-type, alloy-type, and conversion-type systems. While alloy-type anode materials (such as Sn, P, and Sb) possess high theoretical specific capacity, they are prone to severe volume expansion (exceeding 300%) during cycling, leading to pulverization and failure of the active material, resulting in poor cycle stability of sodium-ion batteries. Hard carbon materials can provide even higher specific capacity, but their ion migration rate remains insufficient, limiting further improvements in the energy density and rate performance of sodium-ion batteries.

[0067] Among intercalated anode materials, titanium dioxide (TiO2) exhibits relatively small volume expansion (less than 4%) and good cycle stability during cycling. However, the intrinsic semiconductor properties of titanium dioxide result in extremely low electronic conductivity, severely limiting the effective utilization of its specific capacity. Simultaneously, the large ionic radius of sodium ions leads to a significant potential energy barrier that sodium ions must overcome to migrate within the titanium dioxide lattice, resulting in slow migration. These factors combined lead to a situation where the actual specific capacity of traditional titanium dioxide anode materials is far lower than its theoretical value, resulting in poor rate performance and failing to meet the requirements of high-performance sodium-ion batteries. While various methods have been employed to improve the electrochemical performance of titanium dioxide as an anode material, these methods often rely on high-purity titanium sources (such as tetrabutyl titanate and titanium tetrachloride), leading to high raw material costs for titanium dioxide production. This contradicts the low-cost goal of sodium-ion batteries.

[0068] Furthermore, in the metallurgical industry, titanium-containing blast furnace slag is a large amount of solid waste generated during the smelting of vanadium-titanium magnetite. The stockpiling of titanium-containing blast furnace slag not only occupies a large amount of land but also poses a potential threat to the surrounding environment. Titanium-containing blast furnace slag contains a certain amount of titanium resources. Extracting and utilizing these titanium resources can not only effectively realize the resource utilization of waste but also help solve the environmental problems caused by solid waste accumulation, aligning with the green and sustainable development strategy.

[0069] In summary, existing sodium-ion batteries are limited by problems such as low specific capacity, slow sodium ion migration, poor cycle stability, or high raw material costs associated with traditional anode materials. Meanwhile, a large amount of titanium-containing blast furnace slag has not been effectively utilized. Therefore, developing a novel anode material preparation technology that can simultaneously achieve high specific capacity, improved sodium ion migration rate, good cycle stability, and ultra-low raw material costs is of paramount importance for promoting the development and manufacturing of sodium-ion batteries and realizing the green recycling of industrial solid waste.

[0070] To address the aforementioned technical problems, this application proposes a method for preparing a negative electrode material for sodium-ion batteries. The method includes: first, treating titanium-containing blast furnace slag to obtain metatitanic acid; then, treating the metatitanic acid to obtain titanate, which exhibits a nanoflower morphology; and finally, treating the titanate to obtain titanium dioxide. It should be understood that titanates are compounds containing titanate ions, typically positive titanate ions (TiO3). 2- ) or metatitanate ions (TiO2) - ).

[0071] In some embodiments, the TiO2 mass percentage in the titanium-containing blast furnace slag is greater than 50%, which facilitates the extraction of metatitanic acid. For example, the titanium-containing blast furnace slag can be water-quenched titanium-containing blast furnace slag, which is titanium-containing blast furnace slag treated by a water quenching process. This can inhibit the crystallization of titanium minerals (such as perovskite), allowing titanium to exist in a more dispersed glassy or microcrystalline form, facilitating subsequent titanium extraction operations. Exemplary examples show the main components of water-quenched titanium-containing blast furnace slag as shown in Table 1:

[0072] Table 1. Mass percentage of major components in water-quenched titanium-containing blast furnace slag

[0073]

[0074]

[0075] It should be noted that the mass percentage of titanium in titanium-containing blast furnace slag varies considerably depending on its source. Therefore, the above-mentioned method for preparing the negative electrode material for sodium-ion batteries is applicable to titanium-containing blast furnace slag raw materials from different sources.

[0076] Reference Figure 3 , Figure 3 This is a schematic diagram of the microstructure of titanium dioxide powder prepared by the preparation methods of some embodiments of this application, and Figure 3 Images of titanium dioxide powder displayed under a scanning electron microscope (SEM). Figure 3 The resolution of image a) is 10 μm; Figure 3 The resolution of image b) is 5 μm; Figure 3 Image c) has a resolution of 2 μm. Figure 3 As can be seen, titanium dioxide has a nanoflower morphology and a three-dimensional nanoflower structure.

[0077] Nanoflower-shaped titanium dioxide, as an anode material for sodium-ion batteries, effectively increases the specific surface area of ​​the anode material, providing abundant active sites and shorter diffusion paths for sodium ions, thus enhancing their migration rate. Furthermore, the nanoflower-shaped titanium dioxide can effectively buffer the volumetric strain generated during sodium ion insertion / extraction, preventing pulverization of the anode material and exhibiting high cycle stability. When the anode material prepared by the above method is applied to sodium-ion batteries, it maintains a stable structure during charge and discharge, which is beneficial for improving the cycle stability of sodium-ion batteries, ensuring long cycle life, and contributing to increased reversible capacity.

[0078] It should be noted that specific capacity refers to the ratio of the amount of charge that reversibly participates in the reaction during the charge and discharge process to the mass of the active material; reversible capacity refers to the capacity of the battery that can be repeatedly recycled through reversible electrochemical reactions during the charge and discharge process. The two are conditionally positively correlated. When the structure of the negative electrode material remains stable during the charge and discharge process of a sodium-ion battery (for example, when the volume expansion of the negative electrode material is mitigated), increasing the specific capacity of the sodium-ion battery is beneficial to increasing its reversible capacity.

[0079] The titanium dioxide prepared by the above method also contains oxygen vacancies. Oxygen vacancies are formed when oxygen atoms detach from the crystal lattice of metal oxides or other oxygen-containing compounds, resulting in the absence of oxygen atoms in the lattice and the formation of vacancies. Oxygen vacancies have a significant impact on the photoelectric, catalytic, and energy storage properties of materials. The following are testing techniques that can be used to detect oxygen vacancies in metal oxide lattices: For example, X-ray photoelectron spectroscopy identifies the electronic state changes caused by oxygen vacancies by analyzing the binding energy shift of oxygen atoms on the surface (approximately 10 nm depth) of the negative electrode material. Another example is high-resolution imaging using transmission electron microscopy, which can observe the absence or distortion of lattice fringes in metal oxides, directly locating oxygen vacancies.

[0080] The presence of oxygen vacancies in titanium dioxide in the anode material can improve the intrinsic electronic conductivity of the anode material, reduce the resistance to sodium ion migration, and thus increase the migration rate of sodium ions, which helps to increase the specific capacity of the anode material.

[0081] In summary, preparing titanium dioxide with nanoflower morphology and oxygen vacancies as an anode material for sodium-ion batteries can improve the migration rate of sodium ions, increase the specific capacity and cycle stability of the anode material, and exhibit better rate performance. Furthermore, using titanium-containing blast furnace slag as a raw material to prepare the aforementioned anode material can significantly reduce raw material costs, which is beneficial for addressing the environmental problems caused by solid waste accumulation and aligns with the green and sustainable development strategy. The aforementioned process for preparing anode materials using titanium-containing blast furnace slag as a raw material is also relatively simple.

[0082] When the aforementioned negative electrode materials are applied to sodium-ion batteries, they can ensure long cycle life and high reversible capacity, and also help reduce the manufacturing cost of sodium-ion batteries.

[0083] It should also be noted that the titanium dioxide mentioned in the following description refers to titanium dioxide with nanoflower morphology and oxygen vacancies.

[0084] In some embodiments, the treatment of titanium-containing blast furnace slag to obtain metatitanic acid includes the following steps:

[0085] First, titanium-containing blast furnace slag is mixed with concentrated sulfuric acid and reacted to prepare the first product. In this way, the titanium oxides in the titanium-containing blast furnace slag can react with concentrated sulfuric acid to form soluble titanium salts (such as titanium oxysulfate), thus enabling the extraction of titanium resources from the titanium-containing blast furnace slag. The first product includes titanium oxysulfate.

[0086] In some embodiments, the mass ratio of titanium-containing blast furnace slag to concentrated sulfuric acid is 1:(1.3-1.4). For example, the mass ratio of titanium-containing blast furnace slag to concentrated sulfuric acid can be 1:1.3, 1:1.35, or 1:1.4. For example, 3g of titanium-containing blast furnace slag can be mixed with 4.2ml of concentrated sulfuric acid, and the mass fraction of the concentrated sulfuric acid can be 95%-98% (e.g., 95%, 96%, 97%, or 98%).

[0087] It should be understood that when the mass ratio of titanium-containing blast furnace slag to concentrated sulfuric acid is greater than 1:1.3, the amount of concentrated sulfuric acid mixed with the slag is insufficient, making it difficult to react fully with the slag and resulting in insufficient extraction of titanium oxysulfate. When the mass ratio is less than 1:1.4, the amount of concentrated sulfuric acid mixed with the slag is excessive. This leads to higher preparation costs due to the excessive use of concentrated sulfuric acid, and also results in an excessively low pH value for the first product. Subsequent preparation operations requiring pH adjustment necessitate the addition of excessive alkaline particles or solutions, further increasing preparation costs.

[0088] Therefore, by having a suitable mass ratio between titanium-containing blast furnace slag and concentrated sulfuric acid, it is possible to ensure that concentrated sulfuric acid and titanium-containing blast furnace slag react fully while helping to reduce the cost of preparing titanium dioxide from titanium-containing blast furnace slag.

[0089] After titanium-containing blast furnace slag is mixed with concentrated sulfuric acid, the mixture can be placed in a high-temperature environment for reaction. The reaction temperature can be 125℃~140℃, for example, 125℃, 128℃, 130℃, 132℃, 134℃, 136℃, 138℃ or 140℃; the reaction time can be 35 minutes~45 minutes, for example, 35 minutes, 38 minutes, 40 minutes, 41 minutes, 42 minutes, 43 minutes or 45 minutes.

[0090] For example, the particle size of the titanium-containing blast furnace slag can be less than or equal to 0.074 mm. The titanium-containing blast furnace slag and concentrated sulfuric acid can be mixed in an alumina crucible. Alumina has good corrosion resistance, which can prevent the crucible from being corroded or contaminated with the mixture inside the crucible. Then, the alumina crucible containing the titanium-containing blast furnace slag and concentrated sulfuric acid is placed in a high-temperature tube furnace to heat the mixture at high temperature.

[0091] The first product is then dissolved to obtain a first acid leaching solution, which includes titanium oxysulfate. The first product can be dissolved under heating conditions, which can effectively improve the leaching rate of titanium oxysulfate. The dissolution temperature of the first product is 58℃~70℃, for example, the dissolution temperature of the first product can be 58℃, 60℃, 62℃, 65℃, 67℃, 68℃ or 70℃; the dissolution time of the first product under heating conditions is 35 minutes~45 minutes, for example, the dissolution time of the first product under heating conditions is 35 minutes, 38 minutes, 40 minutes, 41 minutes, 42 minutes, 43 minutes or 45 minutes.

[0092] For example, the first product can be ground to a particle size of less than or equal to 0.15 mm (e.g., 0.15 mm, 0.1 mm, or 0.05 mm), and then dissolved to further improve the leaching rate of titanium oxysulfate.

[0093] In some embodiments, dissolving the first product includes: mixing the first product of a first preset mass with a first preset volume of dilute sulfuric acid solution. On the one hand, this allows the titanium oxysulfate in the first product to dissolve in the dilute sulfuric acid solution; on the other hand, the dilute sulfuric acid solution can dilute the first product, so that the first acid leaching solution has a higher pH value than the first product, which facilitates the subsequent extraction of metatitanic acid.

[0094] Under certain conditions, dilute sulfuric acid solution can react with titanium oxide in the first product to generate titanium oxysulfate, which dissolves in dilute sulfuric acid solution, thus enabling further extraction of titanium resources from titanium-containing blast furnace slag.

[0095] In some embodiments, the molar concentration of the dilute sulfuric acid solution is 0.3 mol / L to 0.8 mol / L. For example, the molar concentration of the dilute sulfuric acid solution can be 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, or 0.8 mol / L.

[0096] The ratio of the first preset mass to the first preset volume is (1 / 7 to 1 / 5) mg / ml. For example, the ratio of the first preset mass to the first preset volume can be (1 / 7) mg / ml, (1 / 6) mg / ml, or (1 / 5) mg / ml.

[0097] For example, the molar concentration of the dilute sulfuric acid solution can be 0.6 mol / L. When mixing the first product with dilute sulfuric acid, the ratio can be 6 ml of dilute sulfuric acid solution for every 1 mg of the first product.

[0098] In some other embodiments, dissolving the first product may also include mixing the first product with deionized water, which can achieve the purpose of dissolving the soluble titanium salt in deionized water; and the deionized water can dilute the first product, so that the first acid leaching solution has a higher pH value than the first product, which facilitates the subsequent extraction of metatitanic acid.

[0099] After obtaining the first acid leaching solution, the pH value of the first acid leaching solution is adjusted to obtain the first solution. The pH value of the first solution is 1.8 to 2.5, for example, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, or 2.5. Under such acidic conditions, it is more conducive to the hydrolysis reaction of titanium oxysulfate in the first solution to generate metatitanic acid, which is a precipitate.

[0100] It should be noted that when the pH of the first solution is too high, ferric sulfate and magnesium sulfate in the first solution are also prone to hydrolysis, and the hydrolysis products, when incorporated into metatitanic acid, will affect the purity of metatitanic acid. When the pH of the first solution is too low, the hydrolysis efficiency of titanium oxysulfate is low, resulting in a low extraction rate of metatitanic acid. Therefore, maintaining the pH of the first solution at 1.8–2.5 is beneficial for improving the hydrolysis efficiency of titanium oxysulfate and also helps to improve the purity of metatitanic acid.

[0101] In some embodiments, adjusting the pH value of the first acid leaching solution includes mixing at least one of sodium hydroxide and deionized water with the first acid leaching solution. This can raise the pH value of the first acid leaching solution. Deionized water can adjust the pH value of the first acid leaching solution by diluting it, and sodium hydroxide can react with hydrogen ions in the first acid leaching solution to adjust its pH value.

[0102] For example, sodium hydroxide can be mixed with the first acid leaching solution; or, deionized water can be mixed with the first acid leaching solution; or, both sodium hydroxide and deionized water can be mixed with the first acid leaching solution.

[0103] During the process of adjusting the pH value of the first acid leaching solution, the solution can be stirred at a first temperature, which is between 75℃ and 85℃. For example, the first temperature can be 75℃, 78℃, 80℃, 82℃, 84℃, or 85℃. High temperatures reduce the viscosity of the first acid leaching solution, promoting molecular diffusion and increasing the mixing rate. Stirring can be performed using magnetic stirring, a non-contact mixing technique that uses a magnetic field to drive a stir bar. The rotation of the stir bar propels the liquid flow, ensuring uniform mixing of reactants or solutions. This eliminates the need for mechanical transmission components, avoids direct contact between the acid and metal parts, and reduces the risk of corrosion.

[0104] The following explanation will be based on the example of mixing sodium hydroxide and deionized water with the first acid leaching solution.

[0105] To adjust the pH of the first acid leaching solution, it can be initially diluted by mixing it with deionized water at a volume ratio of 1:4 to obtain the second acid leaching solution. It should be understood that the pH of the second acid leaching solution is higher than that of the first. Then, sodium hydroxide solid particles or sodium hydroxide solution are added to the second acid leaching solution in batches until the first solution is obtained. This method of first diluting the first acid leaching solution with deionized water and then adding sodium hydroxide to the second acid leaching solution to adjust the pH of the first acid leaching solution reduces the amount of sodium hydroxide used, thus helping to lower the preparation cost of metatitanic acid from titanium-containing blast furnace slag.

[0106] After adjusting the pH of the first acid leaching solution to 1.8–2.5, the first solution is heated to a first preset temperature to hydrolyze titanium oxysulfate into metatitanic acid. The first preset temperature is 105℃–120℃, for example, it can be 105℃, 106℃, 107℃, 108℃, 109℃, 110℃, 112℃, 114℃, 116℃, 118℃, or 120℃. At the first preset temperature, the first solution promotes the hydrolysis of titanium oxysulfate to generate metatitanic acid.

[0107] During the heating of the first solution to the first preset temperature, the first solution can be stirred, and the stirring method can be the same as that for the first acid leaching solution described above. After heating the first solution to the first preset temperature, the first solution is kept at the first preset temperature, and stirring continues. Stirring can further promote the hydrolysis reaction of titanium oxysulfate. It should be noted that the simultaneous heating and stirring of the first solution results in a faster hydrolysis reaction of titanium oxysulfate, which in turn leads to a faster rate of formation of metatitanic acid precipitate in the first solution. This can easily cause the later-formed metatitanic acid to continue growing on the previously formed metatitanic acid precipitate, resulting in a larger particle size of the final metatitanic acid. The titanium dioxide prepared from the larger-particle-size metatitanic acid also has a larger particle size. When titanium dioxide is used in sodium-ion batteries, it is difficult for it to fully contact and react with the electrolyte.

[0108] Therefore, when the first solution turns grayish-black, it indicates that metatitanic acid has begun to form. At this point, stirring and heating can be stopped, and the first solution can be allowed to stand for 0.5 to 1.5 hours (e.g., 0.5, 0.8, 1, 1.2, or 1.5 hours) to allow the titanium oxysulfate in the first solution to hydrolyze slowly, ensuring that the generated metatitanic acid is relatively uniformly dispersed in the first solution and that the resulting metatitanic acid precipitate has a small particle size. Then, the first solution is heated and stirred again for 55 to 65 minutes (e.g., 55, 58, 60, 63, or 65 minutes) to further promote the hydrolysis of titanium oxysulfate.

[0109] As described above, the product obtained from the first solution reaction is metatitanic acid. The metatitanic acid is naturally cooled and then repeatedly washed and centrifuged with deionized water and anhydrous ethanol until the pH of the supernatant is 6.8–7.2 (e.g., 6.8, 6.9, 7.1, or 7.2). This reduces the hydrogen ions in the metatitanic acid, preventing interference with subsequent preparation operations (e.g., preparing metatitanic acid into nano-flower-like titanates). Finally, the metatitanic acid after removing the supernatant is dried in a vacuum for 10–15 hours (e.g., 10, 12, 14, or 15 hours) to obtain metatitanic acid powder. For example, the metatitanic acid obtained at this stage has an irregular granular morphology; the resulting metatitanic acid powder is white in color.

[0110] In some embodiments, metatitanic acid is treated to obtain titanate, including the following steps:

[0111] First, a second predetermined mass of metatitanic acid is mixed with a second predetermined volume of sodium hydroxide solution and stirred to form a mixture. Then, the mixture is heated to a second predetermined temperature and maintained at that temperature for a first predetermined time, allowing the substances in the mixture to react and generate titanate (e.g., sodium titanate). The titanate exhibits a nanoflower morphology. Finally, the obtained titanate is washed and centrifuged multiple times before drying to prepare titanate powder.

[0112] It should be understood that metatitanic acid reacts with sodium hydroxide to form titanate, and the morphology of titanate is prone to change in an alkaline environment.

[0113] In some embodiments, the molar concentration of the sodium hydroxide solution is 6 mol / L to 6.8 mol / L, for example, the molar concentration of the sodium hydroxide solution can be 6 mol / L, 6.1 mol / L, 6.2 mol / L, 6.3 mol / L, 6.4 mol / L, 6.5 mol / L, 6.6 mol / L, 6.7 mol / L, or 6.8 mol / L. By having a suitable molar concentration of sodium hydroxide solution and a suitable pH value in the mixture, titanate can grow into a sheet-like structure, and the sheet-like structure can curl to form a nanoflower structure. When the molar concentration of sodium hydroxide solution is too high, the pH value of the mixture is too high, causing the sheet-like structure of titanate to curl excessively to form a linear structure, making it easier for titanate to transform into a nanowire morphology. When the molar concentration of sodium hydroxide solution is too low, the pH value of the mixture is insufficient, making it difficult for irregularly shaped particulate metatitanic acid to transform into a sheet-like structure.

[0114] In some embodiments, the ratio of the second preset mass to the second preset volume is 20 mg / mL to 30 mg / mL. For example, the ratio can be 20 mg / mL, 22 mg / mL, 24 mg / mL, 26 mg / mL, 28 mg / mL, or 30 mg / mL. It should be understood that when there is too little sodium hydroxide solution, it cannot react sufficiently with metatitanic acid; when there is too much sodium hydroxide solution, the pH of the resulting titanate is too high, affecting subsequent operations (for example, when it is necessary to lower the pH of the titanate, the titanate needs to be rinsed too many times, affecting the overall preparation efficiency).

[0115] Therefore, by setting the ratio of the second preset mass to the second preset volume to 20 mg / mL to 30 mg / mL, it is possible to ensure that metatitanic acid can react fully with sodium hydroxide, and also to avoid the pH value of the generated titanate being too high, thereby reducing the need for rinsing titanate.

[0116] For example, 200 mg of metatitanic acid powder and 7.5 ml of a 6.3 mol / L sodium hydroxide solution can be mixed in a polytetrafluoroethylene (PTFE) liner and stirred for 1 hour to ensure thorough mixing of the metatitanic acid and sodium hydroxide solution, thus preparing a mixture. The PTFE liner has good corrosion resistance and chemical inertness, which can prevent contamination of the mixture.

[0117] The mixture can then be placed in a stainless steel high-pressure reactor and reacted at a first preset temperature for a first preset time.

[0118] In some embodiments, the second preset temperature is 145°C to 155°C, and the first preset duration is 34 hours to 40 hours. High-temperature environments can more effectively promote changes in the morphology of titanates.

[0119] In some embodiments, the titanate is treated to obtain titanium dioxide, including the following steps:

[0120] First, titanate is mixed with a dilute hydrochloric acid solution, and the reaction of titanate with dilute hydrochloric acid yields nano-flower-like metatitanic acid. (Refer to...) Figure 4 , Figure 4 This is a schematic diagram of the microstructure of nano-flower-like metatitanic acid prepared by the preparation methods of some embodiments of this application, and Figure 4 Images of nano-flower-like metatitanic acid under SEM. Figure 4 In (a) the resolution of the image is 20 μm; Figure 4 The resolution of image b) is 5 μm; Figure 4 Image c) has a resolution of 2μm; Figure 4 The resolution of image d) is 1 μm.

[0121] Then, the nano-flower-shaped metatitanic acid is heated to a third preset temperature in an inert gas atmosphere and held at the third preset temperature for a second preset time to obtain titanium dioxide; finally, the obtained titanium dioxide is naturally cooled to room temperature. The nano-flower-shaped metatitanic acid can decompose into titanium dioxide under certain temperature conditions, giving the titanium dioxide a nano-flower morphology.

[0122] For example, mixing titanate with a dilute hydrochloric acid solution can be achieved by immersing the titanate in the dilute hydrochloric acid solution, allowing the titanate to react fully with the hydrochloric acid. The immersion time of the titanate in the dilute hydrochloric acid solution is greater than or equal to 24 hours.

[0123] In some embodiments, the molar concentration of the dilute hydrochloric acid solution is 0.08 mol / L to 0.15 mol / L, for example, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, or 0.15 mol / L. It should be understood that when the molar concentration of the dilute hydrochloric acid solution is too low, titanate is unlikely to react fully with dilute hydrochloric acid to form metatitanic acid; when the molar concentration of the dilute hydrochloric acid solution is too high, chloride ions in the dilute hydrochloric acid solution easily combine with titanium ions in the titanate to form complexes, affecting the yield of metatitanic acid. Therefore, by using a suitable molar concentration of the dilute hydrochloric acid solution, it is possible to ensure that the titanate reacts fully with dilute hydrochloric acid to form metatitanic acid, thus ensuring the yield of metatitanic acid.

[0124] In some embodiments, the third preset temperature is 550°C to 620°C, and the second preset duration is 2 hours to 2.5 hours. By heating the nano-flower-like metatitanic acid at the third preset temperature, the reaction of the nano-flower-like metatitanic acid can be promoted to generate titanium dioxide and water vapor; when the generated titanium dioxide is heated in an inert gas, the oxygen ions in the titanium dioxide lattice gain sufficient energy due to thermal excitation to escape from the lattice sites and form oxygen vacancies.

[0125] In some embodiments, the inert gas may be argon; or the inert gas may be a mixture of argon and hydrogen, wherein the volume percentage of hydrogen in the mixture is 8% to 11%, for example, the volume percentage of hydrogen in the mixture may be 8%, 9%, 10% or 11%.

[0126] This application also proposes a negative electrode material for a sodium-ion battery, which is prepared by the above-described method for preparing a negative electrode material for sodium-ion batteries. The beneficial effects of the negative electrode material for sodium-ion batteries can be found in any of the above embodiments, and will not be repeated here.

[0127] This application also proposes a method for preparing a sodium-ion battery, which includes preparing a negative electrode and a positive electrode. The positive electrode is prepared by fabricating a sodium metal sheet. The negative electrode includes a negative electrode material, which is prepared by the method described above for preparing a negative electrode material for a sodium-ion battery. The beneficial effects of this method for preparing a sodium-ion battery can be found in the beneficial effects described in any of the above embodiments, and will not be repeated here.

[0128] In some embodiments, the method for preparing the negative electrode includes the following steps:

[0129] First, titanium dioxide powder, carbon black conductive agent, and polyvinylidene fluoride (PVDF) are uniformly dispersed in N-methyl-2-pyrrolidone (NMP) to prepare an electrode slurry. Then, the electrode slurry is coated onto a conductive substrate. Finally, the conductive substrate coated with the electrode slurry is dried in a vacuum to prepare the negative electrode.

[0130] The temperature at which the conductive substrate is dried in a vacuum is 40℃ to 60℃. For example, the temperature at which the conductive substrate is dried in a vacuum can be 40℃, 42℃, 45℃, 50℃, 52℃, 55℃, 58℃, or 60℃. The drying time of the conductive substrate in a vacuum is 20 hours to 26 hours. For example, the drying time of the conductive substrate in a vacuum can be 20 hours, 22 hours, 24 hours, 25 hours, or 26 hours.

[0131] For example, the conductive substrate mentioned above can be carbon cloth, copper foil, or aluminum foil.

[0132] Carbon black possesses a high specific surface area and excellent electrical conductivity. By mixing carbon black conductive agent with PVDF and adding it to NMP solvent, the electronic conductivity of electrode materials can be significantly improved. Carbon black particles can form a conductive network in PVDF, reducing internal resistance and improving the utilization rate of active materials, thereby contributing to enhanced rate performance and cycle stability of ion batteries.

[0133] In some embodiments, the mass ratio of titanium dioxide, carbon black conductive agent, and polyvinylidene fluoride is (6-10):(1-3):(1-2). For example, the mass ratio of titanium dioxide, carbon black conductive agent, and polyvinylidene fluoride can be 7:2:1.

[0134] In some embodiments, the titanium dioxide loading in the negative electrode is 1.0 mg / cm³. 2 ~1.5mg / cm 2 For example, the loading of titanium dioxide can be 1.0 mg / cm³. 2 1.1 mg / cm 2 1.2 mg / cm 2 1.3 mg / cm 2 1.4 mg / cm 2 Or 1.5 mg / cm 2 .

[0135] It should be noted that the titanium dioxide loading refers to the mass of titanium dioxide per unit area of ​​the negative electrode. Excessive titanium dioxide loading hinders electrolyte wetting of the negative electrode, making the structure of the negative electrode material easily damaged during the charge and discharge process of the sodium-ion battery, thus affecting the cycle stability of the sodium-ion battery. Conversely, insufficient titanium dioxide loading affects the insertion of sodium ions into the negative electrode, thus impacting the specific capacity of the sodium-ion battery.

[0136] The titanium dioxide loading was 1.0 mg / cm³. 2 ~1.5mg / cm 2 This facilitates the wetting of the negative electrode by the electrolyte and allows sodium ions to be inserted and extracted into the negative electrode, thereby enhancing the cycle stability and increasing the specific capacity of the sodium-ion battery.

[0137] This application also proposes a sodium-ion battery, wherein the positive electrode of the sodium-ion battery comprises a sodium metal sheet, and the negative electrode comprises the aforementioned negative electrode material. In manufacturing the sodium-ion battery, the aforementioned negative electrode material can be used as the negative electrode, and the sodium metal sheet can be used as the positive electrode. The beneficial effects of applying the aforementioned negative electrode material to a sodium-ion battery can be found in the beneficial effects described in any of the above embodiments, and will not be repeated here.

[0138] The electrolyte in sodium-ion batteries is a chlorine-containing ester electrolyte, which includes sodium perchlorate (NaClO4), fluoroethylene carbonate (FEC), propylene carbonate (PC), and ethylene carbonate (EC).

[0139] In some embodiments, the molar concentration of NaClO4 in the electrolyte is 0.8 mol / L to 1.2 mol / L. For example, the molar concentration of NaClO4 in the electrolyte can be 0.8 mol / L, 0.9 mol / L, 1 mol / L, or 1.2 mol / L.

[0140] It should be understood that when the concentration of NaClO4 is too high, it will increase the viscosity of the electrolyte, hinder the migration of sodium ions, and reduce the ionic conductivity, thereby affecting the rate performance and charge / discharge efficiency of the sodium-ion battery. On the other hand, when the concentration of NaClO4 is too low, it will result in insufficient number of free sodium ions in the electrolyte, a decrease in the migration rate of sodium ions, and an increase in the internal resistance of the sodium-ion battery, thereby reducing the rate performance and charge / discharge efficiency of the sodium-ion battery.

[0141] Therefore, by maintaining the molar concentration of NaClO4 in the electrolyte at 0.8 mol / L to 1.2 mol / L, the viscosity of the electrolyte can be avoided from being too high, ensuring the migration rate of sodium ions, and thus ensuring the rate performance and charge / discharge efficiency of the sodium-ion battery.

[0142] In some embodiments, the mass percentage of FEC in the electrolyte is 3% to 8%, for example, 3%, 4%, 5%, 6%, 7% or 8% of the mass percentage of FEC in the electrolyte.

[0143] It should be understood that when the mass percentage of FEC in the electrolyte is too low, carbonate solvents (such as EC) are prone to decomposition and gas production, which can cause sodium-ion batteries to expand or experience capacity decay, thus shortening the cycle life of sodium-ion batteries. When the mass percentage of FEC in the electrolyte is too high, FEC may excessively consume the electrolyte, resulting in an excessively thick solid electrolyte interphase (SEI) film formed on the negative electrode surface, which can hinder sodium ion transport.

[0144] Therefore, by maintaining a FEC mass percentage of 3% to 8% in the electrolyte, the migration and transport rate of sodium ions can be guaranteed, which is also beneficial to ensuring the cycle life of sodium-ion batteries.

[0145] In some embodiments, the volume ratio of PC to EC in the electrolyte is 1:1, which helps to suppress the generation of side reactions, such as avoiding excessive SEI film thickness (increased impedance) caused by excessive EC or continuous solvent decomposition (gas generation) caused by excessive PC.

[0146] After applying the above-mentioned negative electrode material to the negative electrode of a sodium-ion battery, the electrochemical performance of the negative electrode of the sodium-ion battery can be detected by cyclic voltammetry (CV) and galvanostatic charge-discharge method (GCD).

[0147] Reference Figure 5 and Figure 6 , Figure 5 This is a schematic diagram of the CV curve of the negative electrode of a sodium-ion battery according to some embodiments of this application; Figure 6 This is a schematic diagram of the specific capacity test of the negative electrode of a sodium-ion battery according to some embodiments of this application; wherein the titanium dioxide in the negative electrode material is prepared by heating nano-flower-shaped metatitanic acid to 600°C in an argon atmosphere.

[0148] It should be noted that, Figure 5 In the diagram, 1st represents the CV curve of the first cycle, 2nd represents the CV curve of the second cycle, and 3rd represents the CV curve of the third cycle; the horizontal axis represents the potential, and the vertical axis represents the current. Figure 6 The middle horizontal axis represents the number of cycles, the left vertical axis represents the specific capacity, and the right vertical axis represents the coulombic efficiency.

[0149] Reference Figure 5 In the CV curve of the first cycle, the negative electrode exhibits a reduction peak in the range of 0.0–0.5 V and an oxidation peak in the range of 2.0–2.5 V. This is related to the formation of an SEI film on the negative electrode surface by the electrolyte during the initial cycle. Furthermore, the CV curves of the second and third cycles almost overlap. The high degree of overlap in the CV curves across multiple cycles indicates good cycle stability of the negative electrode. (Reference) Figure 6 The specific capacity of the negative electrode after 80 cycles is 180mAh / g to 190mAh / g. Compared with the specific capacity after the first cycle, the capacity decay is less, and the sodium-ion battery has a high coulombic efficiency, indicating high cycle stability.

[0150] Reference Figure 7 and Figure 8 , Figure 7 This is a schematic diagram of the CV curve of the negative electrode of a sodium-ion battery according to some other embodiments of this application; Figure 8 This is a schematic diagram illustrating the specific capacity test of the negative electrode of a sodium-ion battery according to other embodiments of this application; wherein the titanium dioxide in the negative electrode material is prepared by heating nano-flower-shaped metatitanic acid to 600°C in the aforementioned mixed gas environment. It should be noted that... Figure 7The 1st, 2nd, 3rd, and x-coordinates, along with their meanings, can be found in the above explanation. Figure 5 Description; Figure 8 The meanings of the horizontal and vertical axes can be found in the above explanation. Figure 6 The description.

[0151] Reference Figure 7 The reason why the negative electrode shows reduction and oxidation peaks in the CV curve of the first cycle is related to... Figure 5 Similarly, the CV curves of the second and third cycles almost overlap. The high degree of overlap in the CV curves across multiple cycles indicates good cycle stability of the negative electrode. (Reference) Figure 8 The specific capacity of the negative electrode after 80 cycles is 130mAh / g to 140mAh / g. Compared with the specific capacity after the first cycle, the capacity decay is small, and the sodium-ion battery has a high coulombic efficiency, indicating high cycle stability.

[0152] In summary, the application of anode materials containing titanium dioxide to sodium-ion batteries can not only solve the problem of slow sodium-ion migration rate and increase the specific capacity of sodium-ion batteries, but also ensure the coulombic efficiency and cycle stability of sodium-ion batteries.

[0153] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a negative electrode material of a sodium ion battery, comprising: treating a titanium-containing blast furnace slag to obtain metatitanic acid; treating the metatitanic acid to obtain a titanate, the titanate having a nanoflower morphology; and treating the titanate to obtain titanium dioxide, the titanium dioxide having a nanoflower morphology and the titanium dioxide having oxygen vacancies.

2. The method of claim 1, wherein treating the titanium-containing blast furnace slag to obtain the metatitanic acid comprises: mixing the titanium-containing blast furnace slag with concentrated sulfuric acid and reacting to obtain a first product; dissolving the first product to obtain a first acid leaching solution, the first acid leaching solution comprising titanyl sulfate; adjusting a pH value of the first acid leaching solution to obtain a first solution, the pH value of the first solution being 1.8-2.5; and heating the first solution to a first preset temperature to make the titanyl sulfate hydrolyze to generate the metatitanic acid.

3. The method of claim 2, wherein the mass ratio of the titanium-containing blast furnace slag to the concentrated sulfuric acid is 1:(1.3-1.4).

4. The method of claim 2, wherein dissolving the first product comprises: mixing a first preset mass of the first product with a first preset volume of a dilute sulfuric acid solution; and the dilute sulfuric acid solution has a molar concentration of 0.3-0.8 mol / L, and the ratio of the first preset mass to the first preset volume is (1 / 7-1 / 5) mg / ml.

2. The production method according to claim 1, characterized by, 5. The method of claim 2, wherein adjusting the pH value of the first acid leaching solution comprises: mixing at least one of sodium hydroxide and deionized water with the first acid leaching solution.

6. The method of claim 2, wherein the first preset temperature is 105-120 °C.

7. The method of claim 1, wherein treating the metatitanic acid to obtain the titanate comprises: mixing a second preset mass of the metatitanic acid with a second preset volume of a sodium hydroxide solution to obtain a mixed solution; heating the mixed solution to a second preset temperature and maintaining at the second preset temperature for a first preset time period, so that the substances in the mixed solution react to obtain the titanate.

8. The method of claim 7, wherein the sodium hydroxide solution has a molar concentration of 6-6.8 mol / L, and the ratio of the second preset mass to the second preset volume is 20-30 mg / mL.

9. The method of claim 7, wherein the second preset temperature is 145-155 °C, and the first preset time period is 34-40 hours.

3. The method of claim 2, wherein, 10. The method of claim 1, wherein treating the titanate to obtain the titanium dioxide comprises: mixing the titanate with a dilute hydrochloric acid solution, the titanate reacting with the dilute hydrochloric acid to obtain nanoflower-shaped metatitanic acid; heating the nanoflower-shaped metatitanic acid to a third preset temperature in an inert gas and maintaining at the third preset temperature for a second preset time period to obtain the titanium dioxide.

4. The preparation method according to claim 2, characterized in that, 11. The method of claim 10, wherein the dilute hydrochloric acid solution has a molar concentration of 0.08-0.15 mol / L.

12. The method of claim 10, wherein the third preset temperature is 550-620 °C, and the second preset time period is 2-2.5 hours.

13. A sodium ion battery prepared by the method of any one of claims 1-12.

5. The preparation method according to claim 2, characterized in that, 14. The sodium ion battery of claim 13, comprising: a negative electrode comprising a negative electrode material prepared by the method of any one of claims 1-12. ​ 6. The preparation method according to claim 2, characterized in that, ​ 7. The production method according to any one of claims 1 to 6, characterized by, ​ ​ ​ 8. The production method according to claim 7, characterized by, ​ 9. The preparation method according to claim 7, characterized in that, ​ 10. The method of claim 1, wherein, ​ ​ ​ 11. The method of claim 10, wherein, ​ 12. The method of claim 10, wherein, ​ 13. A negative electrode material for a sodium-ion battery, characterized by, ​ 14. A method of preparing a sodium-ion battery, characterized by, ​ ​ A positive electrode is manufactured by manufacturing a sodium metal sheet into a positive electrode.

15. A sodium-ion battery, characterized in that, The application relates to a sodium ion battery. A positive electrode is manufactured by manufacturing a sodium metal sheet into a positive electrode. The application relates to a sodium ion battery. A negative electrode is manufactured by manufacturing a sodium metal sheet into a negative electrode.

16. The sodium-ion battery of claim 14, wherein, The loading of the titanium dioxide is 1.0 mg / cm 2 ~ 1.5 mg / cm 2 .

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