Single-phase niobate and active electrode material, and preparation methods therefor and use thereof

Abstract

The present invention belongs to the technical fields of inorganic non-metallic materials, electrochemistry, material chemistry and chemical power supply products, and more specifically relates to a single-phase niobate and an active electrode material for lithium-ion batteries, and preparation methods therefor and the use thereof. The single-phase niobate provided by the present invention has a chemical formula of Ti x Nb y O z (0.15≤x / z≤0.25, and 0.20≤y / z≤0.28) and has the characteristics of a high titanium content and a low niobium content. The single-phase niobate provided by the present invention is prepared by means of a liquid phase method based on a precursor solution, can be subjected to a suitable post-treatment, has high safety performance, specific capacity, first-cycle coulombic efficiency, rate capability, cycle performance and temperature adaptability when being used for a negative electrode of a lithium-ion battery, and has relatively low costs. The preparation method for the active electrode material provided by the present invention is simple, and the active electrode material has wide application prospects in the field of ultra-fast charging and high-power lithium-ion batteries. The present invention provides more options for an active negative electrode material of a lithium-ion battery, and can vigorously promote the rapid development of high-performance lithium-ion batteries.

Description

A single-phase niobate, an active electrode material, its preparation method, and its applications Technical Field

[0001] This invention belongs to the technical fields of inorganic non-metallic materials, electrochemistry, materials chemistry and chemical power source products. More specifically, it relates to a single-phase niobate for lithium-ion batteries, an active electrode material, its preparation method and application. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy output, high conversion efficiency, long lifespan, and low self-discharge, have been widely and rapidly adopted in various fields of human life, from consumer electronics to electric vehicles and large-scale energy storage. The global market for lithium-ion batteries is projected to grow at a rate of 20% to 30% annually until 2030. Against this backdrop, higher demands are being placed on lithium-ion batteries, such as combining safety, stability, high energy density, weather resistance, and ultra-fast charging capabilities to meet the urgent needs of emerging application areas such as hybrid electric vehicles, start-stop power supplies, high-end electric motorcycles, electric engineering vehicles, electric buses, electric logistics vehicles, baseband processing units (BBUs), warehouse robots, power tools, drones, electric ships, military applications, and frequency and peak-valley regulation in grid-connected energy storage systems.

[0003] Lithium-ion batteries mainly consist of four parts: a positive electrode, a negative electrode, a separator, and an electrolyte. Their charging and discharging principle is essentially based on Li... + Through transport by the electrolyte solution, reversible deintercalation and intercalation occur in the negative and positive electrode materials, accompanied by the interconversion of chemical energy and electrical energy. Taking a lithium-ion battery with LiCoO2 as the positive electrode and graphite as the negative electrode as an example, during charging, Li... + It is extracted from the positive electrode material, releasing an electron, Co 3+ Oxidized to Co 4+ Li + The electrolyte transports the Li through the membrane and embeds it into the graphite anode, while the graphite gains an electron to maintain charge balance; during discharge, Li + Co is extracted from the negative electrode material graphite and embedded into the positive electrode material. 4+ Restored to Co 3+ Battery charging rate is usually expressed in "rate". 1C charging refers to the charging current that fully charges the battery in 1 hour, while 10C charging is the charging current that fully charges the battery in 1 / 5 hour (12 minutes).

[0004] As a core component of lithium-ion batteries, the main commercially available anode materials are carbon (including silicon-carbon) and lithium titanate (Li4Ti5O). 12 Carbon materials (represented by graphite) possess high reversible specific capacity (approximately 300–360 mAh g⁻¹). –1Due to its low cost and long cycle life, graphite is widely used in small electronic devices. However, graphite presents significant safety concerns. Graphite has a very low operating potential (<0.2 V vs. Li / Li). + At higher charge / discharge rates (≥5C), graphite generates large overpotentials, making it prone to lithium dendrite formation. The formation of lithium dendrites significantly increases the probability of battery short circuits, posing a serious safety hazard. Furthermore, graphite has a low lithium-ion diffusion rate, resulting in poor rate performance. These problems severely limit its application in high-performance lithium-ion batteries. Adding silicon or silicon compounds to carbon materials to form silicon-carbon anode materials increases the specific capacity of the anode material, but fails to solve the aforementioned problems with carbon materials. Li4Ti5O 12 It possesses a highly secure and stable working platform (1.5–1.6 V vs. Li / Li). + It also exhibits excellent cycling performance. Modified (typically nano-sized and carbon-coated) Li₄Ti₅O₂... 12 It can achieve rapid charge and discharge. However, Li4Ti5O 12 Small reversible specific capacity (only 160–170 mAh g) –1 Furthermore, its low tap density makes it unsuitable for use in high-energy-density lithium-ion batteries. Therefore, developing lithium-ion battery anode materials with high safety, reversible specific capacity, rate performance (≥5C), cycle performance, and temperature adaptability is extremely important and urgent.

[0005] Niobates (or niobium-based mixed oxides) were first identified as potential anode materials in academic literature in 1983. However, due to the lack of commercially available cathode materials that matched their rate performance, they attracted limited interest at the time. Interest in niobate anode materials rekindled in 2011, with renewed interest in using titanium niobate (TiNb₂O₇) as an anode material and commercially available LiNi₂. 0.5 Mn 1.5 An experiment was conducted using O4 as the positive electrode material in a battery, demonstrating its significant advantages in fast charging capability, cycle life, and volumetric energy density. Subsequently, several novel niobate anode materials were developed, including Ti2Nb. 10 O 29 TiNb 24 O 62 And other non-titanium niobate niobates. These niobates, either intrinsically or after modification (such as carbon coating), can achieve high safety, reversible specific capacity, rate performance (≥5C), cycling performance, and temperature adaptability.

[0006] However, among the existing niobates, TiNb2O7 has a relatively low niobium content (76.8 wt%, calculated as Nb2O5, the same below), while other niobates generally have a niobium content >89%, such as Ti2Nb 10 O 29 The niobium content is 89.3 wt%, TiNb 24 O 62 TiNb₂O₇ contains 97.6 wt% niobium. Its relatively low niobium content and the availability of inexpensive titanium raw materials make TiNb₂O₇ significantly cheaper than other niobates, thus attracting widespread attention and substantial basic and applied research. However, the still relatively high niobium content of TiNb₂O₇ significantly hinders the industrialization of niobates. Therefore, developing niobates with even lower niobium contents than TiNb₂O₇ is crucial and urgently needed for the industrialization of niobates. Summary of the Invention

[0007] To address the issue of poor overall performance of existing commercially available anode materials for lithium-ion batteries, the present invention aims to provide a lithium-ion battery active electrode material with superior overall performance—a multi-titanium, low-niobium niobate. This material possesses high safety performance, specific capacity, first-cycle coulombic efficiency, rate performance, cycle performance, and temperature adaptability, while also being relatively low in cost.

[0008] This invention also provides a method for preparing single-phase niobate. This invention further provides an active electrode material containing the above-mentioned single-phase niobate.

[0009] Another object of the present invention is to provide the application of the above-mentioned single-phase niobate or active electrode material.

[0010] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0011] In a first aspect, the present invention provides a general formula Ti x Nb y O z A single-phase niobate, wherein 0.15 ≤ x / z ≤ 0.25 and 0.20 ≤ y / z ≤ 0.28; preferably, 0.171 ≤ x / z ≤ 0.215 and 0.228 ≤ y / z ≤ 0.263. Precise values ​​of x, y, and z within a defined range can be selected to provide a charge-balanced crystal structure. Typical compositions include Ti. 1.5 Nb 1.6 O7, Ti 1.4 Nb 1.68 O7, Ti 1.3 Nb 1.76 O7 and Ti 1.2 Nb 1.84 O7.

[0012] Compared with traditional TiNb2O7, the Ti of this invention...x NbyOz is characterized by "high titanium and low niobium" and is entirely a single-phase material, not a multiphase material. Based on considerations of defect chemical charge balance, particle number balance, and positional balance, the crystal structure of TixNbyOz in this invention retains the TiNb2O7 crystal structure (the crystal structure unit is a 3×3 octahedron with shared edges and points in an ordered connection) while containing at least one of cation interstitial sites (Ti ion interstitial site and Nb ion interstitial site) and oxygen ion vacancies, thus maintaining a thermodynamically metastable state. Because the niobium content of TixNbyOz in this invention is significantly low (e.g., Ti...),... 1.5 Nb 1.6 O7 contains only 63.9 wt% niobium, which is 16.8% lower than TiNb2O7. This significantly reduces the cost of niobates and is very beneficial to the industrialization of niobates.

[0013] The reversible specific capacity of the titanium-based, low-niobium niobate active electrode material of this invention can be 270–300 mAh / g, or even greater. Here, specific capacity is defined as a voltage window of 0.8–3.0 V vs. Li / Li at a rate of 0.1C. + The specific capacity was tested in the second cycle of a half-cell constant current cycling experiment. High specific capacity active materials have the advantage of improving the performance of electrochemical devices. Providing active electrode materials with high specific capacity can increase the energy density and power density of electrochemical devices incorporating such active electrode materials.

[0014] The titanium-based, low-niobium niobate active electrode material of this invention can achieve a voltage rating of 0.8–3.0 V vs. Li / Li at a rate of 0.1C during the second cycle of a half-cell constant current cycling test. + The appropriate voltage distribution was measured within the voltage window, with an average operating potential of 1.4–1.7 vs. Li / Li. + When the lithium intercalation voltage is between 2.0 V and 0.8 V, the specific capacity of this material is greater than 240 mAh g⁻¹. –1 When the delithiation voltage is between 0.8 V and 2.0 V, the specific capacity of this material is greater than 240 mAh g. –1 Providing active electrode materials with higher operating voltages can improve the safety performance of electrochemical devices incorporating such materials.

[0015] The titanium-based, low-niobium niobate active electrode material of this invention can achieve a first-cycle coulombic efficiency of 85–98%, typically 90–95%. Here, the first-cycle coulombic efficiency is obtained by testing in the first cycle of a half-cell constant-current cycling test at a rate of 0.1C with a voltage window of 0.8–3.0 V vs. Li / Li+. This invention provides an active electrode material with high first-cycle coulombic efficiency, which can improve the energy density and power density of electrochemical devices incorporating this active electrode material.

[0016] The titanium- and niobium-free niobate active electrode material of the present invention can have a capacity retention rate greater than 80%, typically above 85%. Here, the capacity retention rate is defined as the ratio of 0.8–3.0 V vs. Li / Li at 5C charge and discharge rates (equal charge and discharge rates) during 500 cycles of a half-cell constant current cycling test. + The voltage window was obtained from testing. Providing an active electrode material with high capacity retention can improve the cycling performance of electrochemical devices incorporating such an active electrode material.

[0017] The multi-titanium, low-niobium niobate active electrode material of the present invention can have a diameter greater than 10–12 cm. 2 s –1 Li + Diffusion rate. This invention provides an active electrode material with a high Li+ diffusion rate, which can improve the rate (fast charge) performance of electrochemical devices containing this active electrode material.

[0018] The multi-titanium, low-niobium niobate active electrode material of the present invention can achieve a 2.5 g cm⁻¹ after rolling. –3 Even higher electrode densities were achieved. This material achieved up to 3.0 g / cm³ after roll pressing. –3 Even higher electrode densities are possible. Providing materials with higher electrode densities can improve the energy density of electrochemical devices containing such active electrode materials. Specifically, high volumetric capacity can be achieved when the electrode density is high, based on the formula: volumetric capacity = mass capacity × electrode density × percentage of active material.

[0019] The titanium-based, low-niobium niobate active electrode material of the present invention may further contain Li. In other words, the active electrode material may be a lithium-based active electrode material. The active electrode material can be represented by the general formula LiλTixNbyOz, where x, y, and z satisfy the above-mentioned ranges, and the selection of λ can provide charge balance.

[0020] Active electrode materials may comprise a large number of primary particles (sometimes called microcrystals). The average particle size of the primary particles can be from 10 nm to 10 μm, preferably from 100 nm to 5 μm, although the ideal particle size depends on its application. For example, smaller primary particles (e.g., less than 100 nm) may be advantageous when the active electrode material is intended for use in high-power batteries. If the active electrode material is used to develop high-energy batteries, larger particle sizes (e.g., 1–5 μm) may be advantageous. These primary particles may partially or completely aggregate into secondary particles. Secondary particles are typically porous. In some cases, these primary particles are substantially non-agglomerated. When some or all of the primary particles aggregate into secondary particles, the average size of the secondary particles is 0.5–30 μm, preferably 2–20 μm, although the ideal particle size depends on its application. For example, in applications where the active electrode material is used in high-power batteries, smaller secondary particles (1.5–5 μm, or even smaller than 1.5 μm) may be advantageous. In applications where active electrode materials are intended for the development of high-energy batteries, larger secondary particles (8–20 μm, or even larger) may be advantageous. The particle size of both primary and secondary particles can be measured using any known conventional techniques, such as electron microscopy imaging and laser particle size analysis.

[0021] The active electrode material can form a carbon-coated layer on the surface of both primary and secondary particles. For secondary particles, carbon can coat the voids within the particles. The carbon-coated layer may contain graphitic carbon. Carbon coating methods can include chemical vapor deposition, organic pyrolysis, ball milling, etc. The carbon content, based on the total weight of the active electrode material, can be less than 5 wt%, preferably less than 2 wt%, and more preferably less than 1 wt%.

[0022] In a second aspect, the present invention provides an electrochemical device comprising a negative electrode, a positive electrode, and an electrolyte and a separator disposed between the negative electrode and the positive electrode, wherein the negative electrode comprises an active electrode material developed according to a first aspect of the present invention. The electrolyte may be a liquid electrolyte. An alternative or additional electrolyte may be a solid electrolyte. The separator may be a polymer separator or a ceramic separator. The negative electrode may further contain a conductive agent and a binder. For example, the negative electrode may consist of 80 wt% active material, 10 wt% conductive agent, and 10 wt% binder. Alternatively, the negative electrode may consist of 92 wt% active material, 4 wt% conductive agent, and 4 wt% binder. The amount of active electrode material in the negative electrode may be between 70 wt% and 99 wt%, preferably between 80 wt% and 98 wt%, and more preferably between 90 wt% and 96 wt%.

[0023] In a third aspect, the present invention provides an active electrode material according to the first aspect of the present invention, which is used as a negative electrode active material or as a component of a negative electrode active material in a negative electrode, and is combined with a positive electrode, an electrolyte and a separator for use in the charging and discharging of a lithium-ion battery.

[0024] In a fourth aspect, the present invention provides a method for processing an active electrode material as an active negative electrode material or a component of a negative electrode active material for use in a lithium-ion battery, wherein the method includes diffusing lithium ions into the negative electrode active material.

[0025] In a fifth aspect, the present invention provides a method for preparing a general formula Ti according to the first aspect of the present invention. x Nb y O z A liquid-phase method for single-phase niobate, comprising the following steps:

[0026] 1. Dissolve the titanium source and niobium source raw materials in any one of water, alcohol, or alcohol-water solvent to form a solution;

[0027] 2. The solution is treated by any one of the following methods: spray drying, solvothermal method, sol-gel method, direct evaporation method, or coprecipitation method to obtain precursor powder.

[0028] 3. The precursor powder is sintered in a temperature range of 700–1200 °C to form an active electrode material.

[0029] Here, the titanium and niobium source materials are titanium and niobium compounds soluble in water or alcohol. For the titanium source material, water-soluble titanium oxysulfate and titanium chloride, and ethanol-soluble tetraisopropyl titanate and tetrabutyl titanate, can be selected. For the niobium source material, water-soluble niobium oxalate (including hydrated niobium oxalate) and ammonium niobium oxalate (including hydrated ammonium niobium oxalate), and ethanol-soluble niobium chloride and niobium ethanol can be selected. Dissolving the titanium and niobium source materials in water, alcohol, or an alcohol-water solvent to form a solution achieves complete mixing of titanium and niobium ions at the atomic / molecular level. This is crucial for preparing multi-titanium, low-niobium niobates (metastable, containing at least one defect: cation interstitial and oxygen ion vacancy). In contrast, the traditional solid-state sintering method for preparing TiNb2O7 by ball milling and mixing titanium dioxide (TiO2) and niobium pentoxide (Nb2O5) cannot produce multi-titanium, low-niobium niobates because the niobates obtained by this traditional solid-state sintering method are in a thermodynamically stable state.

[0030] When preparing single-phase niobate using the liquid-phase method in this invention, the alcohol used includes, but is not limited to, ethanol, and may also be other alcohols such as isopropanol, butanol, and ethylene glycol.

[0031] The sintering step of the precursor powder can be maintained for 0.5 hours to 24 hours, more preferably 2 hours to 10 hours. For example, the sintering step can last for 2 hours to 10 hours or even longer. The sintering step can be performed for 24 hours to 10 hours or even less.

[0032] In some methods, sintering can be beneficial. For example, precursor powders can be heated at a first heating temperature for a certain time, and then at a second heating temperature for a certain time. Generally, the second heating temperature is higher than the first heating temperature. Performing such a two-step sintering can help the solid-state reaction form the desired crystal structure.

[0033] The sintering step of the precursor powder can be carried out in a gaseous atmosphere. The gaseous atmosphere can be inert, reducing, or oxidizing. When it is desirable to produce an oxygen-deficient material, sintering the precursor material in an inert or reducing atmosphere is preferred. Suitable gaseous environments include: air, O2, N2, Ar, He, CO2, CO, H2, and mixtures thereof.

[0034] This method may require one or more post-treatment steps on the formed titanium-niobium-sparing niobate. In some cases, the method may include a post-treatment step of heat treatment of the titanium-niobium-sparing niobate, sometimes referred to as "annealing." This heat treatment step may be carried out in an atmosphere different from that of the sintering precursor powder. The heat treatment step may be carried out in an inert or reducing gas atmosphere. Such a heat treatment step may be carried out at temperatures above 500 °C, such as 700 °C. The heat treatment step may be beneficial in forming more defects in the active electrode material. In some cases, the method may include mixing the titanium-niobium-sparing niobate with a carbon source to form a carbon coating on the titanium-niobium-sparing niobate. The mixture of titanium-niobium-sparing niobate and carbon source can be heated to form a carbon coating on the titanium-niobium-sparing niobate. Suitable carbon sources include, but are not limited to: carbohydrate materials (e.g., sugars, polymers), conductive carbon (e.g., carbon black), and aromatic carbon materials (e.g., pitch carbon). Carbon coating of titanium-niobium-sparing niobate can also be achieved using chemical vapor deposition or organic pyrolysis. A preferred method for carbon coating is to grind the active electrode material with a carbon source, and then heat the active electrode material and carbon source in a furnace under an inert or reducing atmosphere, thereby causing the carbon source to pyrolyze into carbon and coat the surface of the titanium-niobate particles. Another preferred method for forming a carbon coating involves mixing the titanium-niobate with a carbon source, dispersing the titanium-niobate and carbon source in an aqueous slurry, and then spray drying. The titanium-niobate and carbon source are then heated in a furnace under an inert or reducing atmosphere, thereby causing the carbon source to pyrolyze into carbon and coat the surface of the titanium-niobate particles. If the carbon source is conductive carbon, pyrolysis of the material after spray drying is unnecessary. In some cases, the method may include grinding the titanium-niobate to modify its particle size. For example, the titanium-niobate can be processed by one or more processes, including air jet milling, sieving, or ball milling. This can provide a more suitable particle size for the desired application of the titanium-niobate. In addition, conventional modification methods (doping, compositing, and nano-sizing, etc.) can be used to modify titanium-rich and niobium-poor niobates. For example, for doping modification, only a small amount of a water- or alcohol-soluble compound containing the dopant element needs to be added during the material preparation process.

[0035] The present invention includes combinations of the foregoing aspects and preferred features, unless such combinations are explicitly not permitted.

[0036] The beneficial effects of this invention are as follows:

[0037] (1) The multi-titanium and low-niobium niobate active electrode material provided by the present invention is applied to the negative electrode of lithium-ion battery. It not only has a series of advantages such as high specific capacity, safety performance, first-cycle coulombic efficiency, rate performance and cycle performance, but also has low cost and is suitable for industrial production.

[0038] (2) The method for preparing multi-titanium, low-niobium niobate provided by this invention is simple. Batteries assembled with other battery components are suitable for safe, stable, high-energy, weather-resistant, and ultra-fast charging applications, including hybrid electric vehicles, start-stop power supplies, high-end electric motorcycles, electric engineering vehicles, electric buses, electric logistics vehicles, baseband processing power supplies (BBU), warehouse robot power tools, drones, electric ships, military applications, and frequency and peak-valley regulation in grid-connected energy storage systems. Its application prospects are very broad. This invention provides more options for active negative electrode materials in lithium-ion batteries and can greatly promote the rapid development of high-performance lithium-ion batteries. Attached Figure Description

[0039] Figure 1 shows the Ti obtained in Example 1. 1.5 Nb 1.6 X-ray diffraction (XRD) pattern of O7 porous microspheres;

[0040] Figure 2 shows the Ti obtained in Example 1. 1.5 Nb 1.6 Scanning electron microscope (SEM) image of O7 porous microspheres;

[0041] Figure 3 shows the Ti obtained in Example 1. 1.5 Nb 1.6 Charge-discharge curves of O7 / Li half-cell at different rates;

[0042] Figure 4 shows the Ti obtained in Example 1. 1.5 Nb 1.6 Cycling performance of O7 / Li half-cell at 5C rate;

[0043] Figure 5 shows the Ti obtained in Example 2. 1.4 Nb 1.68 X-ray diffraction (XRD) pattern of O7 porous microspheres;

[0044] Figure 6 shows the Ti obtained in Example 2. 1.4 Nb 1.68 Scanning electron microscope (SEM) image of O7 porous microspheres;

[0045] Figure 7 shows the Ti obtained in Example 2. 1.4 Nb 1.68 Charge-discharge curves of O7 / Li half-cell at different rates;

[0046] Figure 8 shows the Ti obtained in Example 2. 1.4 Nb 1.68 Cycling performance of O7 / Li half-cell at 5C rate;

[0047] Figure 9 shows the Ti obtained in Example 3. 1.4 Nb 1.68 X-ray diffraction (XRD) pattern of O7 particles;

[0048] Figure 10 shows the Ti obtained in Example 3. 1.6 Nb 1.52 Scanning electron microscope (SEM) image of O7 particles;

[0049] Figure 11 shows the Ti obtained in Example 3. 1.6 Nb 1.52 Charge-discharge curves of O7 / Li half-cell at different rates;

[0050] Figure 12 shows the Ti obtained in Example 3. 1.6 Nb 1.52 Cycling performance of O7 / Li half-cell at 5C rate;

[0051] Figure 13 shows the Ti obtained in Example 4. 1.3 Nb 1.76 X-ray diffraction (XRD) pattern of O7 particles;

[0052] Figure 14 shows the Ti obtained in Example 4. 1.3 Nb 1.76 Scanning electron microscope (SEM) image of O7 particles;

[0053] Figure 15 shows the Ti obtained in Example 4. 1.3 Nb 1.76 Charge-discharge curves of O7 / Li half-cell at different rates;

[0054] Figure 16 shows the Ti obtained in Example 4. 1.3 Nb 1.76 Cycling performance of O7 / Li half-cell at 5C rate;

[0055] Figure 17 shows the Ti obtained in Example 5. 1.2 Nb 1.84 X-ray diffraction (XRD) pattern of O7 porous microspheres;

[0056] Figure 18 shows the Ti obtained in Example 5. 1.2 Nb 1.84 Scanning electron microscope (SEM) image of O7 porous microspheres;

[0057] Figure 19 shows the Ti obtained in Example 5. 1.2 Nb 1.84 Charge-discharge curves of O7 / Li half-cell at different rates;

[0058] Figure 20 shows the Ti obtained in Example 5. 1.2 Nb 1.84 Cycling performance of O7 / Li half-cell at 5C rate;

[0059] Figure 21 shows the X-ray diffraction (XRD) pattern of the TiNb2O7 micron particles obtained in Comparative Example 1;

[0060] Figure 22 shows a scanning electron microscope (SEM) image of the TiNb2O7 micron particles obtained in Comparative Example 1;

[0061] Figure 23 shows the charge-discharge curves of the TiNb2O7 / Li half-cell obtained in Comparative Example 1 at different rates;

[0062] Figure 24 shows the cycling performance of the TiNb2O7 / Li half-cell obtained in Comparative Example 1 at a 5C rate.

[0063] Figure 25 shows the X-ray diffraction (XRD) pattern of the TiNb2O7 porous microspheres obtained in Comparative Example 2;

[0064] Figure 26 shows a scanning electron microscope (SEM) image of the TiNb2O7 porous microspheres obtained in Comparative Example 2;

[0065] Figure 27 shows the charge-discharge curves of the TiNb2O7 / Li half-cell obtained in Comparative Example 2 at different rates;

[0066] Figure 28 shows the carbon-coated Ti obtained in Example 25. 1.5 Nb 1.6 O7 (C-Ti) 1.5 Nb 1.6 O7) Transmission electron microscope (TEM) image of porous microspheres;

[0067] Figure 29 shows the C-Ti obtained in Example 25. 1.5 Nb 1.6 Charge-discharge curves of O7 / Li half-cell at different rates;

[0068] Figure 30 shows the C-Ti obtained in Example 25. 1.5 Nb 1.6 Cycling performance of O7 / Li half-cell at 5C rate;

[0069] Figure 31 shows the LiNi obtained in Example 26. 0.5 Mn 1.5 O4 / Ti 1.5 Nb 1.6 Charge and discharge curves of the O7 full battery at different rates;

[0070] Figure 32 shows the LiNi obtained in Example 26. 0.5 Mn 1.5 O4 / Ti 1.5 Nb 1.6 Cycling performance of O7 full cell at 7C rate. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0072] Example 1: Preparation of multi-titanium and low-niobium niobate by spray drying

[0073] 0.03 mol titanium oxysulfate and 0.032 mol niobium oxalate (hydrated) were dissolved in 300 mL of deionized water and stirred to form a homogeneous aqueous solution. Ti was prepared by spray drying. 1.5 Nb 1.6 O7 precursor powder. The spray dryer was set with an inlet temperature of 180 °C and an outlet temperature of 84 °C, and a peristaltic pump flow rate of 20 rpm to spray dry the above aqueous solution to obtain Ti. 1.5 Nb 1.6 O7 precursor powder. The obtained precursor powder was sintered in a muffle furnace at 1050 °C for 4 hours to obtain Ti. 1.5 Nb 1.6 O7 porous microspheres. Sieving was performed using a 300-mesh sieve.

[0074] Half-cell preparation and testing: 80 wt% of a high-titanium, low-niobium niobate, 10 wt% of a binder (polyvinylidene fluoride), and 10 wt% of conductive carbon (acetylene black) were added to N-methylpyrrolidone and mixed to prepare a slurry. This slurry was coated onto one side of a copper foil and dried. The fully dried electrode was rolled to obtain an active material loading of 4–5 mg cm⁻¹. –2 The working electrode was then used. A CR2032 half-cell was assembled, with the electrolyte being 1 M lithium hexafluorophosphate dissolved in a mixed solvent of ethylene carbonate / diethylene carbonate / dimethyl carbonate (volume ratio 1:1:1), the separator being glass fiber, and the counter electrode being a lithium sheet. The electrochemical testing temperature was approximately 25 °C. Each electrochemical test cycle was performed in constant current mode, with a voltage window of 0.8–3.0 V vs. Li / Li. + The charging rate (charging current density) and discharging rate (discharging current density) are equal, with 1C set to 250 mA g. –1 .

[0075] Figure 1 shows the Ti obtained in Example 1. 1.5 Nb 1.6 X-ray diffraction (XRD) pattern of O7 porous microspheres, analysis of which yielded the Ti prepared by spray drying method. 1.5 Nb 1.6The O7 porous microspheres have a single-phase sheared ReO3 type crystal structure, possessing the same crystal structure unit as TiNb2O7 (3×3 octahedrons with shared edges and points in an ordered connection). Figure 2 shows the Ti obtained in Example 1. 1.5 Nb 1.6 Scanning electron microscope (SEM) images of O7 porous microspheres show that Ti 1.5 Nb 1.6 The primary particle size of the O7 porous microspheres is between 0.1 and 0.4 μm, and the secondary particle size is between 0.5 and 2.5 μm. Figure 3 shows the Ti obtained in Example 1. 1.5 Nb 1.6 Charge-discharge curves of the O7 / Li half-cell at different rates. The active material loading was 5.01 mg cm⁻¹. –2 Ti 1.5 Nb 1.6 The reversible specific capacity of the O7 / Li half-cell at 0.1C is 277 mAh g. –1 The initial coulombic efficiency is 90.5%, and the reversible specific capacity at 5C is 147 mAh g. –1 Figure 4 shows the Ti obtained in Example 1. 1.5 Nb 1.6 Cycling performance of the O7 / Li half-cell at 5C rate. The active material loading is 5.01 mg cm⁻¹. –2 Ti 1.5 Nb 1.6 The O7 / Li half-cell retained 83.1% of its capacity after 500 cycles at 5C (refer to the second cycle).

[0076] Example 2: Preparation of multi-titanium and low-niobium niobates by solvothermal method

[0077] 0.0035 mol tetraisopropyl titanate and 0.0042 mol niobium ethanol were dissolved in 80 mL of ethanol and stirred to form a homogeneous ethanol solution. Ti was prepared using a solvothermal method. 1.4 Nb 1.68 O7 precursor powder was used. The above solution was transferred to a 100 mL reaction vessel, and the temperature was raised to 200 °C (heating rate of 4 °C / min) using external heating and maintained at 200 °C for 24 hours. After the reaction was complete, the temperature was lowered to room temperature. The suspension in the reaction vessel was centrifuged to separate the solid powder and washed. The obtained precursor powder was sintered in a muffle furnace at 800 °C for 20 h to obtain Ti. 1.4 Nb 1.68 O7 porous microspheres. Sieving was performed using a 300-mesh sieve. Subsequent half-cell preparation and testing methods were the same as in Example 1.

[0078] Figure 5 shows the Ti obtained in Example 2.1.4 Nb 1.68 X-ray diffraction (XRD) pattern of O7 porous microspheres, analysis of which yielded the Ti prepared by the solvothermal method. 1.4 Nb 1.68 The O7 porous microspheres have a single-phase sheared ReO3 type crystal structure, possessing the same crystal structure unit as TiNb2O7 (3×3 octahedrons with shared edges and points in an ordered connection). Figure 6 shows the Ti obtained in Example 2. 1.4 Nb 1.68 Scanning electron microscope (SEM) images of O7 porous microspheres show that Ti 1.4 Nb 1.68 The primary particle size of the O7 porous microspheres is between 0.05 and 0.2 μm, and the secondary particle size is between 0.5 and 3 μm. Figure 7 shows the Ti obtained in Example 2. 1.4 Nb 1.68 Charge-discharge curves of the O7 / Li half-cell at different rates. The active material loading is 4.96 mg cm⁻¹. –2 Ti 1.4 Nb 1.68 The reversible specific capacity of the O7 / Li half-cell at 0.1C is 282 mAh g. –1 The initial coulombic efficiency was 94.0%, and the reversible specific capacity at 5C was 135 mAh g. –1 Figure 8 shows the Ti obtained in Example 2. 1.4 Nb 1.68 Cycling performance of the O7 / Li half-cell at 5C rate. The active material loading is 4.96 mg cm⁻¹. –2 Ti 1.4 Nb 1.68 The O7 / Li half-cell retained 78.4% of its capacity after 500 cycles at 5C (refer to the second cycle).

[0079] Example 3: Preparation of multi-titanium and low-niobium niobates by sol-gel method

[0080] 0.032 mol titanium chloride and 0.0304 mol niobium oxalate (hydrated) were dissolved in 500 mL of ethanol-water (volume ratio 1:1) and stirred to form a homogeneous aqueous solution. Ti was prepared using the sol-gel method. 1.6 Nb 1.52 O7 precursor powder. The above solution was heated with a heater to induce hydrolysis, yielding a gel-like solid, and the solvent was further evaporated. The resulting solid was mixed with ethanol and ground in a planetary ball mill. The resulting slurry was filtered and washed with ethanol to obtain Ti. 1.6 Nb 1.52 O7 precursor powder. The obtained precursor powder was sintered in a muffle furnace at 950 °C for 12 hours to obtain Ti.1.6 Nb 1.52 O7 porous microspheres. Sieving was performed using a 300-mesh sieve. Subsequent half-cell preparation and testing methods were the same as in Example 1.

[0081] Figure 9 shows the Ti obtained in Example 3. 1.6 Nb 1.52 X-ray diffraction (XRD) patterns of O7 particles were analyzed to determine the Ti particles prepared by the sol-gel method. 1.6 Nb 1.52 The O7 particles exhibit a single-phase sheared ReO3-type crystal structure, possessing the same crystal structure unit as TiNb2O7 (3×3 octahedrons with shared edges and points in an ordered connection). Figure 10 shows the Ti obtained in Example 3. 1.6 Nb 1.52 Scanning electron microscope (SEM) images of O7 particles show that Ti... 1.6 Nb 1.52 The primary particle size of O7 particles is between 0.4 and 0.6 μm, and the secondary particle size is between 2 and 20 μm. Figure 11 shows the Ti obtained in Example 3. 1.6 Nb 1.52 Charge-discharge curves of O7 / Li half-cell at different rates. Active material loading was 5.05 mg cm⁻¹. –2 Ti 1.6 Nb 1.52 The reversible specific capacity of the O7 / Li half-cell at 0.1C is 283 mAh g. –1 The initial coulombic efficiency was 93.8%, and the reversible specific capacity at 5C was 140 mAh g. –1 Figure 12 shows the Ti obtained in Example 3. 1.6 Nb 1.52 Cycling performance of the O7 / Li half-cell at 5C rate. Active material loading is 5.05 mg cm⁻¹. –2 Ti 1.6 Nb 1.52 The O7 / Li half-cell retained 87.9% of its capacity after 500 cycles at 5C (refer to the second cycle).

[0082] Example 4: Preparation of multi-titanium and low-niobium niobate by direct evaporation method

[0083] 0.026 mol titanium oxysulfate and 0.0352 mol niobium ammonium oxalate (hydrated) were dissolved in 300 mL of deionized water and stirred to form a homogeneous aqueous solution. Ti was prepared by direct evaporation. 1.3 Nb 1.76 O7 precursor powder. The above solution was placed in a beaker and heated in an 80 °C water bath with constant stirring. After the water in the beaker was completely evaporated, Ti was obtained. 1.3 Nb1.76 O7 precursor powder. The obtained precursor powder was sintered in a muffle furnace at 1100 °C for 2 hours to obtain Ti. 1.3 Nb 1.76 O7 particles were sieved using a 300-mesh sieve. Subsequent half-cell preparation and testing methods were the same as in Example 1.

[0084] Figure 13 shows the Ti obtained in Example 4. 1.3 Nb 1.76 X-ray diffraction (XRD) patterns of O7 particles were analyzed to determine the Ti prepared by the direct evaporation method. 1.3 Nb 1.76 The O7 particles have a single-phase sheared ReO3-type crystal structure, possessing the same crystal structure unit as TiNb2O7 (3×3 octahedrons with shared edges and points in an ordered connection). Figure 14 shows the Ti obtained in Example 4. 1.3 Nb 1.76 Scanning electron microscope (SEM) images of O7 particles show that Ti... 1.3 Nb 1.76 The particle size of O7 particles is between 0.5 and 4 μm. Figure 15 shows the Ti obtained in Example 4. 1.3 Nb 1.76 Charge-discharge curves of O7 / Li half-cell at different rates. Active material loading was 4.95 mg cm⁻¹. –2 Ti 1.3 Nb 1.76 The reversible specific capacity of the O7 / Li half-cell at 0.1C is 279 mAh g. –1 The initial coulombic efficiency was 90.8%, and the reversible specific capacity at 5C was 138 mAh g. –1 Figure 16 shows the Ti obtained in Example 4. 1.3 Nb 1.76 Cycling performance of the O7 / Li half-cell at 5C rate. The active material loading is 4.95 mg cm⁻¹. –2 Ti 1.3 Nb 1.76 The O7 / Li half-cell retained 86.3% of its capacity after 500 cycles at 5C (refer to the second cycle).

[0085] Example 5: Preparation of multi-titanium and low-niobium niobate by co-precipitation method

[0086] 0.024 mol titanium chloride and 0.0368 mol niobium oxalate (hydrated) were dissolved in 300 mL of deionized water and stirred to form a homogeneous aqueous solution. Ti was prepared by co-precipitation. 1.2 Nb 1.84O7 precursor powder. The above solution was continuously stirred at a constant rate, and ammonia was added continuously until a precipitate was completely formed. The resulting precipitate was washed three times with distilled water and ethanol and then dried to obtain Ti. 1.2 Nb 1.84 O7 precursor powder. The obtained precursor powder was sintered in a muffle furnace at 1000 °C for 8 hours to obtain Ti. 1.2 Nb 1.84 O7 porous microspheres. Sieving was performed using a 300-mesh sieve. Subsequent half-cell preparation and testing methods were the same as in Example 1.

[0087] Figure 17 shows the Ti obtained in Example 5. 1.2 Nb 1.84 X-ray diffraction (XRD) pattern of O7 porous microspheres, analysis of which yielded the Ti prepared by co-precipitation method. 1.2 Nb 1.84 The O7 porous microspheres have a single-phase sheared ReO3-type crystal structure, possessing the same crystal structure unit as TiNb2O7 (3×3 octahedrons with shared edges and points in an ordered connection). Figure 18 shows the Ti obtained in Example 5. 1.2 Nb 1.84 Scanning electron microscope (SEM) images of O7 porous microspheres show that Ti 1.2 Nb 1.84 The primary particle size of the O7 porous microspheres is between 0.2 and 0.6 μm, and the secondary particle size is between 0.8 and 2.5 μm. Figure 19 shows the Ti obtained in Example 5. 1.2 Nb 1.84 Charge-discharge curves of the O7 / Li half-cell at different rates. The active material loading is 5.03 mg cm⁻¹. –2 Ti 1.2 Nb 1.84 The reversible specific capacity of the O7 / Li half-cell at 0.1C is 280 mAh g. –1 The initial coulombic efficiency was 90.7%, and the reversible specific capacity at 5C was 131 mAh g. –1 Figure 20 shows the Ti obtained in Example 5. 1.2 Nb 1.84 Cycling performance of the O7 / Li half-cell at 5C rate. The active material loading is 5.03 mg cm⁻¹. –2 Ti 1.2 Nb 1.84 The O7 / Li half-cell retained 85.5% of its capacity after 500 cycles at 5C (refer to the second cycle).

[0088] Comparative Example 1: Preparation of TiNb2O7 micron-sized particles by conventional solid-state sintering method

[0089] 0.01 mol of titanium dioxide and 0.02 mol of niobium pentoxide (molar ratio 1:2) were placed in a 70 mL ball mill jar and ground for 1 h in a high-energy ball mill (SPEX 8000M). The resulting mixture was sintered in a muffle furnace at 1200 °C for 4 h to obtain TiNb₂O₇ micron-sized particles. The particles were then sieved using a 300-mesh sieve. Subsequent half-cell preparation and testing methods were the same as in Example 1.

[0090] Figure 21 shows the XRD pattern of the TiNb2O7 micron particles obtained in Comparative Example 1. Analysis reveals that the TiNb2O7 micron particles prepared by the conventional solid-state sintering method have a single-phase sheared ReO3 crystal structure (the crystal structure unit is a 3×3 octahedron with shared edges and points in an ordered manner). Figure 22 shows a scanning electron microscope image of the TiNb2O7 micron particles obtained in Comparative Example 1, showing that the particle size of the TiNb2O7 micron particles is between 1 and 5 μm. Figure 23 shows the charge-discharge curves of the TiNb2O7 / Li half-cell obtained in Comparative Example 1 at different rates. The active material loading is 4.92 mg cm⁻¹. –2 The reversible specific capacity of the TiNb2O7 / Li half-cell at 0.1C is 268 mAh g. –1 The initial coulombic efficiency was 96.1%, and the reversible specific capacity at 5C was 177 mAh g. –1 Figure 24 shows the cycling performance of the TiNb₂O₇ / Li half-cell obtained in Comparative Example 1 at a 5C rate. The active material loading was 4.92 mg cm⁻¹. –2 The capacity retention of the TiNb2O7 / Li half-cell after 500 cycles at 5C was only 33.6% (referring to the second cycle). Its poor cycle performance is mainly due to the excessively large micron-sized particles of TiNb2O7.

[0091] Comparative Example 2: Preparation of TiNb2O7 porous microspheres by spray drying

[0092] The preparation process of TiNb2O7 porous microspheres by spray drying was the same as in Example 1, except that 0.02 mol titanium oxysulfate and 0.04 mol niobium oxalate (hydrated) were used. The subsequent half-cell preparation and testing methods were the same as in Example 1.

[0093] Figure 25 shows the XRD pattern of the TiNb2O7 porous microspheres obtained in Comparative Example 2. Analysis reveals that the TiNb2O7 porous microspheres prepared by spray drying have a single-phase shear ReO3 type crystal structure, but possess characteristics similar to Ti2Nb. 10 O 29The same crystal structure unit (3×4 octahedrons with shared edges and points in an ordered manner). Figure 26 shows a scanning electron microscope image of the TiNb₂O₇ porous microspheres obtained in Comparative Example 2, revealing that the primary particle size of the TiNb₂O₇ porous microspheres is between 0.1 and 0.3 μm, and the secondary particle size is between 0.5 and 2 μm. Figure 27 shows the charge-discharge curves of the TiNb₂O₇ / Li half-cell obtained in Comparative Example 2 at different rates. The active material loading was 4.71 mg cm⁻¹. –2 The reversible specific capacity of the TiNb2O7 / Li half-cell at 0.1C is 265 mAh g. –1 The first-cycle coulombic efficiency is 78.4%; at 5C, it has almost no capacity and very poor rate performance. The Ti in Example 1... 1.5 Nb 1.6 The rate performance of O7 porous microspheres is significantly better than that of TiNb2O7 porous microspheres in Comparative Example 2. The reason is that Ti 1.5 Nb 1.6 O7 contains a large number of at least one of cation interstitial sites and oxygen ion vacancies, which significantly enhance electrochemical kinetics.

[0094] Clearly, compared with TiNb2O7 micron-sized particles prepared by the traditional solid-state sintering method, TiNb2O7 micron-sized particles prepared by the liquid-phase method based on the precursor solution exhibit superior performance. 1.5 Nb 1.6 O7 material (a representative material of titanium-rich and niobium-poor niobates) exhibits comparable reversible specific capacity, first-cycle coulombic efficiency, and rate performance, but with significantly improved cycle performance and a 17% reduction in niobium content. These advantages, including high safety performance, first-cycle coulombic efficiency, specific capacity, rate performance, cycle performance, and lower cost, fully demonstrate that titanium-rich and niobium-poor niobates are promising anode materials for lithium-ion batteries.

[0095] Preparation of multi-titanium and low-niobium niobates by liquid-phase method based on precursor solution, Examples 6–24 are shown in Table 1.

[0096] Table 1

[0097]

[0098]

[0099] Example 25: Carbon coating of titanium-rich and niobium-poor niobates

[0100] Ti obtained in Example 1 1.5 Nb 1.6 O7 porous microspheres and lactose were mixed in deionized water at a mass ratio of 10:1. In this example, 0.4 g of Ti was used. 1.5 Nb 1.6O7 porous microspheres, 0.04 g lactose, and 30 mL deionized water. The slurry was placed in a beaker and heated in an 80 °C water bath with constant stirring. After the water in the beaker had completely evaporated, carbon-coated Ti was obtained. 1.5 Nb 1.6 O7 (C-Ti) 1.5 Nb 1.6 O7) porous microsphere precursor. The obtained precursor powder was heat-treated at 800 °C for 2 h in a tube furnace under an Ar atmosphere to obtain C-Ti. 1.5 Nb 1.6 O7 porous microspheres (carbon content 1.5 wt%). Sieving was performed using a 300-mesh sieve.

[0101] The subsequent half-cell preparation and testing methods are the same as in Example 1.

[0102] Figure 28 shows the C-Ti obtained in Example 25. 1.5 Nb 1.6 Transmission electron microscopy (TEM) images of O7 porous microspheres show C-Ti 1.5 Nb 1.6 The thickness of the carbon coating layer of O7 is approximately 3 nm. Figure 29 shows the C-Ti obtained in Example 25. 1.5 Nb 1.6 Charge-discharge curves of the O7 / Li half-cell at different rates. The active material loading is 4.98 mg cm⁻¹. –2 C-Ti 1.5 Nb 1.6 The reversible specific capacity of the O7 / Li half-cell at 0.1C is 325 mAh g. –1 The initial coulombic efficiency is 95.5%, and the reversible specific capacity at 5C is as high as 204 mAh g. –1 This rate performance is significantly better than that of C-Ti in Example 1. 1.5 Nb 1.6 The reason for the O7 porous microspheres is that carbon coating improves the performance of Ti. 1.5 Nb 1.6 The conductivity between O7 particles significantly improves electrochemical kinetics. Figure 30 shows the C-Ti obtained in Example 25. 1.5 Nb 1.6 Cycling performance of the O7 / Li half-cell at 5C rate. The active material loading is 4.98 mg cm⁻¹. –2 C-Ti 1.5 Nb 1.6 The O7 / Li half-cell retained 87.1% of its capacity after 500 cycles at 5C (refer to the second cycle).

[0103] Example 26: LiNi 0.5 Mn1.5 O4 / Ti 1.5 Nb 1.6 O7 Full Battery

[0104] Using Ti from Example 1 1.5 Nb 1.6 O7 porous microspheres are used as a negative electrode material; commercial LiNi 0.5 Mn 1.5 O4 is used as the positive electrode material. 92 wt% Ti is added. 1.5 Nb 1.6 O7 porous microspheres, 4 wt% binder (polyvinylidene fluoride), and 4 wt% conductive carbon (acetylene black) were added to N-methylpyrrolidone and mixed to prepare a slurry. This slurry was coated onto one side of a copper foil current collector and dried. The fully dried electrode was then rolled to obtain an active material loading of 18–20 mg cm⁻¹. –2 Ti 1.5 Nb 1.6 O7 negative electrode. LiNi 0.5 Mn 1.5 O4 positive electrode and Ti 1.5 Nb 1.6 The O7 negative electrode was prepared using the same method, except that aluminum foil was used as the current collector. The ratio of negative electrode capacity to positive electrode capacity was 1.1:1. Then, a CR2032 full cell was assembled. The electrolyte was obtained by dissolving 1 M lithium hexafluorophosphate in a mixed solvent of ethylene carbonate / diethylene carbonate / dimethyl carbonate (volume ratio 1:1:1), and the separator was a Cegard 2400 polypropylene membrane. The electrochemical testing temperature was approximately 25 °C. For each cycle of electrochemical testing, the voltage window was 1.5–3.5 V, with equal charging and discharging rates (current densities), and 1C was set to 140 mA g. –1 .

[0105] Figure 31 shows the LiNi obtained in Example 26. 0.5 Mn 1.5 O4 / Ti 1.5 Nb 1.6 Charge-discharge curves of the O7 full battery at different rates. The reversible specific capacity of this full battery at 0.5C is 137 mAh g. –1 The reversible specific capacity at 7C is 75 mAh g. –1 Figure 32 shows the LiNi obtained in Example 26. 0.5 Mn 1.5 O4 / Ti 1.5 Nb 1.6The O7 full cell exhibits excellent cycle performance at 7C. After 4000 cycles at 7C, the full cell retains 86.4% of its capacity (referring to the second cycle). This demonstrates that lithium-ion batteries based on multi-titanium, low-niobium niobate anodes can possess superior electrochemical performance.

[0106] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A single-phase niobate, characterized in that, Its general formula is Ti x Nb y O z Where 0.171≤x / z≤0.215 and 0.228≤y / z≤0.

263.

2. The single-phase niobate according to claim 1, characterized in that, The single-phase niobate has a sheared ReO3 type crystal structure; Its crystal structure unit is a 3×3 octahedron with shared edges and points in an ordered connection.

3. The single-phase niobate according to claim 1 or 2, characterized in that, It may contain doped elements.

4. A method for preparing a single-phase niobate as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Dissolve the titanium source and niobium source in a solvent to obtain a mixed solution; (2) The mixed solution is processed to obtain precursor powder; (3) Sinter the precursor powder.

5. The preparation method according to claim 4, characterized in that, In step (1), the titanium source is a titanium compound that is soluble in water or alcohol; preferably, it is selected from titanium oxysulfate, titanium chloride, tetraisopropyl titanate, and tetrabutyl titanate; the niobium source is a niobium compound that is soluble in water or alcohol; preferably, it is selected from niobium oxalate, ammonium niobium oxalate, niobium chloride, and niobium ethanol; the solvent is one or both of water and alcohol solvents.

6. The preparation method according to claim 4 or 5, characterized in that, In step (2), the treatment method of the mixed solution is spray drying, solvothermal method, sol-gel method, direct evaporation method or coprecipitation method; in step (3), the sintering of the precursor powder is carried out in a gaseous atmosphere, selected from one or more of air, O2, N2, Ar, He, CO2, CO and H2; the sintering temperature is 700–1200 °C and the sintering time is 0.5–24 hours.

7. A single-phase niobate active electrode material, characterized in that, The active electrode material comprises primary and / or secondary particles of single-phase niobate as described in any one of claims 1-3.

8. The single-phase niobate active electrode material according to claim 7, characterized in that, The average size of the primary particles is 10 nm to 10 μm; the average size of the secondary particles is 0.5 μm to 30 μm; the active electrode material contains a carbon layer formed on the surface of the primary particles and / or secondary particles.

9. The single-phase niobate active electrode material according to claim 7, characterized in that, The mass of the carbon layer is less than 5 wt% of the total mass of the active electrode material; preferably, less than 2 wt%; and most preferably, less than 1 wt%.

10. The single-phase niobate active electrode material according to any one of claims 7-9, characterized in that, It also contains Li.

11. The single-phase niobate active electrode material according to any one of claims 7-10, characterized in that, Its preparation method includes one or more of the following post-processing steps: (1) Heat treatment of single-phase niobate; (2) Carbon coating of single-phase niobate; (3) Mix single-phase niobate with conductive material; (4) Grind single-phase niobate to change the particle size of the active electrode material.

12. The use of a single-phase niobate active electrode material as described in any one of claims 1-3 or any one of claims 7-11 as a negative electrode material or as a component of a negative electrode material in a lithium-ion battery.

13. An electrochemical device comprising a negative electrode, a positive electrode, and an electrolyte and a membrane disposed between the negative electrode and the positive electrode, characterized in that, The negative electrode comprises a single-phase niobate as described in any one of claims 1-3 or a single-phase niobate active electrode material as described in any one of claims 7-11.

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