Single-phase niobate, active electrode material, preparation method and application thereof

Abstract

The present invention belongs to the technical field of inorganic non-metallic materials, electrochemistry, material chemistry and chemical power supply products, and more specifically, relates to a single-phase niobate for lithium-ion batteries, an active electrode material and a preparation method and application thereof. The single-phase niobate provided by the present invention is Ti x Nb y O z (0.15≤x / z≤0.25 and 0.20≤y / z≤0.28) and the characteristics of more titanium and less niobium. The single-phase niobate provided by the present invention is prepared by a liquid phase method based on a precursor solution and can be properly post-treated. When used for the negative electrode of a lithium-ion battery, it has high safety performance, specific capacity, first-week coulomb efficiency, rate performance, cycle performance and temperature adaptability, and is relatively low in cost. The preparation method involved in the active electrode material provided by the present invention is simple, and has broad application prospects in the field of ultra-fast charging and high-power lithium-ion batteries. The present invention provides more choices for active negative electrode materials for lithium-ion batteries, which can greatly promote the rapid development of high-performance lithium-ion batteries.

Description

Technical Field

[0001] 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 of a lithium-ion battery, an active electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries, due to their advantages such as high energy output, high conversion efficiency, long life, 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 expected to grow at an annual rate of 20%-30% by 2030. Against this backdrop, higher demands are being placed on lithium-ion batteries, such as safety, stability, high energy efficiency, weather resistance, and ultra-fast charging capabilities, to meet the urgent needs of emerging applications such as hybrid vehicles, start-stop power supplies, high-end electric motorcycles, electric engineering vehicles, electric buses, electric logistics vehicles, baseband processing units (BBUs), warehouse robotic power tools, drones, electric ships, military, and frequency and peak-valley regulation in grid-connected energy storage systems.

[0003] Lithium-ion batteries are mainly composed of four parts: positive electrode, negative electrode, diaphragm and electrolyte. The charging and discharging principle is essentially Li + Through the transport of electrolyte solution, reversible extraction and insertion are carried out in the negative and positive electrode materials, accompanied by the mutual conversion between chemical energy and electrical energy. Take the lithium-ion battery composed of LiCoO2 as the positive electrode and graphite as the negative electrode as an example. During the charging process, Li + It is released from the positive electrode material, releasing an electron, Co 3+ Oxidized to Co 4+ , Li + The electrolyte is transported through the diaphragm and embedded into the graphite negative electrode. At the same time, the graphite obtains an electron to maintain charge balance. During the discharge process, Li + It is released from the graphite of the negative electrode material and embedded in the positive electrode material. 4+ Reduction to Co 3+ The battery charge rate is usually expressed as a "rate". 1C charging refers to the charging current that fully charges the battery in 1 hour, and 10C charging refers to the charging current that fully charges the battery in 1 / 5 of an hour (12 minutes).

[0004] As one of the core components of lithium-ion batteries, the negative electrode materials that have been commercialized are mainly carbon (including silicon carbon) and lithium titanate (Li4Ti5O 12 Carbon materials (represented by graphite) have a high reversible specific capacity (about 300–360 mAh g -1), low cost and long cycle life, it is widely used in small electronic devices. However, there are safety issues that cannot be ignored in graphite. The working potential of graphite is very low (<0.2 V vs. Li / Li + ), when charging and discharging at a larger rate (≥5C), a large overpotential will be generated, which will easily produce lithium dendrites. The formation of lithium dendrites greatly increases the probability of battery short circuit, which brings serious safety hazards. In addition, the lithium ion diffusion rate of graphite is not high, resulting in poor rate performance. These problems seriously limit its application in high-performance lithium-ion batteries. Adding silicon or silicon compounds to carbon materials to form silicon-carbon negative electrode materials increases the specific capacity of the negative electrode materials, but fails to solve the problems of the above carbon materials. Li4Ti5O 12 Has a very safe and stable working platform (1.5–1.6 V vs. Li / Li + ) and excellent cycle performance. After modification (usually nano- and carbon-coated) Li4Ti5O 12 It can achieve fast charge and discharge. However, Li4Ti5O 12 Small reversible specific capacity (only 160–170 mAh g -1 ) and low tap density make it difficult to use in high-energy-density lithium-ion batteries. Therefore, it is very important and urgent to develop lithium-ion battery anode materials with high safety, reversible specific capacity, rate performance (≥5C), cycle performance and temperature adaptability.

[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 commercial cathode materials that matched their rate performance, they attracted limited interest at the time. Until 2011, there was a resurgence of interest in niobate anode materials, with the use of titanium niobate TiNb2O7 as anode material and commercial LiNi 0.5 Mn 1.5 The experiment of using O4 as the positive electrode material in the battery showed that the battery has significant advantages in fast charging capability, cycle life and volume energy density. Since then, a variety of new niobate negative electrode materials have been developed, including Ti2Nb 10 O 29 、TiNb 24 O 62 These niobates, either intrinsically or after modification (e.g., carbon coating), can achieve high safety, reversible specific capacity, rate capability (≥5C), cycle 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 contain >89% niobium, such as Ti2Nb 10 O 29 The niobium content is 89.3 wt%, TiNb 24 O 62 The niobium content of TiNb2O7 is 97.6 wt%. This relatively low niobium content and the inexpensive titanium raw material make TiNb2O7 significantly less expensive than other niobates. Consequently, TiNb2O7 has attracted widespread attention and attracted extensive basic and applied research. However, the high niobium content of TiNb2O7 significantly hinders the industrialization of niobates. Therefore, developing niobates with even lower niobium contents than TiNb2O7 is a key and pressing need for their industrialization. Summary of the Invention

[0007] In response to the problem of poor overall performance of existing commercial negative electrode materials for lithium-ion batteries, the purpose of the present invention is to provide a lithium-ion battery active electrode material with excellent overall performance - high-titanium-low-niobium niobate. This material has high safety performance, specific capacity, first-cycle coulombic efficiency, rate performance, cycle performance and temperature adaptability, and is low in cost.

[0008] The present invention also provides a method for preparing the single-phase niobate. The present invention also provides an active electrode material containing the single-phase niobate.

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

[0010] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are as follows:

[0011] In a first aspect, the present invention provides a general formula Ti x Nb y O z Single-phase niobate, where 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. You can choose x 、 y and z The precise value of , in order to provide a charge balanced crystal structure. Typical components are Ti 1.5 Nb 1.6 O7、Ti 1.4Nb 1.68 O7、Ti 1.3 Nb 1.76 O7 and Ti 1.2 Nb 1.84 O7.

[0012] Compared with the traditional TiNb2O7, the Ti x Nb y O z It has the characteristics of "more titanium and less niobium" and is a single-phase material rather than a multi-phase material. Based on the considerations of defect chemical charge balance, particle number balance and position balance, the Ti x Nb y O z The crystal structure of the TiNb2O7 retains the TiNb2O7 crystal structure (the crystal structure unit is a 3×3 octahedron connected in order with common edges and common points) while containing at least one of the cation gaps (at least one of the Ti ion gaps and the Nb ion gaps) and the oxygen ion vacancy, and is in a thermodynamically metastable state. x Nb y O z The niobium content is significantly lower (such as Ti 1.5 Nb 1.6 The niobium content of O7 is only 63.9 wt%, which is 16.8% lower than that of TiNb2O7. This significantly reduces the cost of niobate and is very conducive to the industrialization of niobate.

[0013] The reversible specific capacity of the high-titanium-low-niobium niobate active electrode material of the present invention can be 270-300 mAh g -1 Here, the specific capacity is defined as a voltage window of 0.8–3.0 V at a rate of 0.1C. vs. Li / Li + The specific capacity measured in the second cycle of a half-cell constant current cycling experiment. Active materials with high specific capacities have the advantage of improving the performance of electrochemical devices. Providing active electrode materials with high specific capacities can enhance the energy density and power density of electrochemical devices containing such active electrode materials.

[0014] The poly-titanium-poor niobate active electrode material of the present invention can have a resistance of 0.8-3.0 V at a rate of 0.1 C in the second cycle of the half-cell constant current cycle test. vs. Li / Li + The voltage window of the appropriate voltage distribution is measured, with an average working potential of 1.4–1.7 vs. Li / Li + When the lithium insertion voltage is between 2.0 V and 0.8 V, the specific capacity of the material is greater than 240 mAh g -1When the delithiation voltage is between 0.8 V and 2.0 V, the specific capacity of the material is greater than 240 mAh g -1 Providing an active electrode material with a higher operating voltage can improve the safety performance of an electrochemical device containing the active electrode material.

[0015] The poly-titanium-poor niobate active electrode material of the present invention can have an initial coulombic efficiency of 85-98%, usually 90-95%. Here, the initial coulombic efficiency is the first cycle of the half-cell constant current cycle test at a rate of 0.1C at 0.8-3.0 V. vs. Li / Li + The present invention provides an active electrode material with high first-cycle coulombic efficiency, which can improve the energy density and power density of electrochemical devices containing the active electrode material.

[0016] The poly-titanium-poly-niobium niobate active electrode material of the present invention can have a capacity retention rate greater than 80%, typically greater than 85%. Here, the capacity retention rate is determined by a half-cell constant current cycle test at a charge and discharge rate of 5C (equal charge and discharge rates) at 0.8-3.0 V for 500 cycles. vs. Li / Li + Providing an active electrode material with a high capacity retention rate can improve the cycle performance of an electrochemical device containing the active electrode material.

[0017] The poly-titanium-poor-niobium niobate active electrode material of the present invention may have a thickness greater than 10–12 cm 2 s -1 Li + The present invention provides a high Li + Active electrode materials with increased diffusion rates can improve the rate (fast charging) performance of electrochemical devices containing the active electrode materials.

[0018] The active electrode material of the present invention, which contains more titanium and less niobium, can have a viscosity of 2.5 g cm after rolling. -3 Even higher electrode density. The material achieved a density of up to 3.0 g cm after roller pressing. -3 Even higher electrode density. Providing materials with higher electrode density can improve the energy density of electrochemical devices containing the active electrode materials. Specifically, when the electrode density is high, high volumetric capacity can be achieved, based on the formula volumetric capacity = mass capacity × electrode density × active material ratio.

[0019] The polytitanium-poor niobate active electrode material of the present invention may further contain Li. In other words, the active electrode material may be a lithiated active electrode material. The active electrode material may be represented by the general formula Li λTi x Nb y O z Indicates that x, y and z Meet the above range, among which select λ Can provide charge balancing.

[0020] The active electrode material may include a large number of primary particles (sometimes referred to as crystallites). The average particle size of the primary particles may range from 10 nm to 10 μm, preferably from 100 nm to 5 μm, although the optimal particle size depends on the intended application. For example, when the active electrode material is intended for use in high-power batteries, smaller primary particles (e.g., less than 100 nm) may be advantageous. 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 fully aggregate into secondary particles. Secondary particles are typically porous. In some cases, these primary particles are substantially unagglomerated. When some or all of the primary particles aggregate into secondary particles, the average secondary particle size is 0.5–30 μm, preferably 2–20 μm, although the optimal secondary particle size depends on the intended application. For example, when 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. Where the active electrode material is intended for use in the development of high energy batteries, larger secondary particles (8–20 μm or even larger) may be advantageous. The particle size of the primary and secondary particles can be measured using any known conventional technique, such as electron microscopy imaging and laser particle size analysis.

[0021] The active electrode material may form a carbon coating on the surfaces of the primary and secondary particles. For the secondary particles, the carbon may be coated into the voids within the secondary particles. The carbon coating may comprise graphitic carbon. Carbon coating may be achieved by chemical vapor deposition, organic pyrolysis, ball milling, or other methods. The amount of carbon coated may be 5 wt% or less, preferably 2 wt% or less, and more preferably 1 wt% or less, based on the total weight of the active electrode material.

[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 the 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. A conductive agent and a binder may be further added to the negative electrode. For example, the negative electrode is composed of 80 wt% active material, 10 wt% conductive agent, and 10 wt% binder. Alternatively, the negative electrode is composed 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 applied to a negative electrode as a negative electrode active material or as a component of a negative electrode active material, and combined with a positive electrode, an electrolyte and a separator for 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 according to the first aspect of the present invention, wherein the method comprises diffusing lithium ions into the negative electrode active material.

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

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

[0027] 2. The solution is treated by any one of spray drying, solvothermal method, sol-gel method, direct evaporation to dryness, and coprecipitation method to obtain a precursor powder.

[0028] 3. Sintering the precursor powder at a temperature in the range of 700–1200°C to form an active electrode material.

[0029] Here, the titanium and niobium source materials are titanium compounds and niobium compounds soluble in water or alcohol. Examples of titanium source materials include water-soluble titanyl sulfate and titanium chloride, as well as ethanol-soluble tetraisopropyl titanate and tetrabutyl titanate. Examples of niobium source materials include water-soluble niobium oxalate (including hydrated niobium oxalate) and ammonium niobium oxalate (including hydrated ammonium niobium oxalate), as well as ethanol-soluble niobium chloride and niobium ethoxide. Dissolving the titanium and niobium source materials in water, alcohol, or alcohol-water solvents to form a solution allows for complete mixing of titanium and niobium ions at the atomic / molecular level, which is crucial for preparing high-titanium-low-niobium niobates (metastable, containing at least one defect, either a cation interstitial or an oxygen ion vacancy). In contrast, the traditional solid-phase sintering method for preparing TiNb2O7, which involves ball-milling titanium dioxide (TiO2) and niobium pentoxide (Nb2O5) and then sintering, cannot produce high-titanium-low-niobium niobates because the niobates obtained by this traditional solid-phase sintering method are thermodynamically stable.

[0030] When the present invention adopts a liquid phase method to prepare single-phase niobate, 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 step of sintering 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 shorter.

[0032] In some methods, a sintering step may be beneficial. For example, the precursor powder may be heated at a first heating temperature for a specified time, and then at a second heating temperature for a specified time. Typically, the second heating temperature is higher than the first heating temperature. This two-step sintering process can aid in the solid-state reaction to form the desired crystal structure.

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

[0034] The method may require one or more post-treatment steps of the formed polytitanium-minority niobate. In some cases, the method may include a post-treatment step of heat-treating the polytitanium-minority niobate, sometimes referred to as "annealing." This post-treatment heat treatment step may be performed in an atmosphere different from that used to sinter the precursor powder. The post-treatment heat treatment step may be performed in an inert or reducing atmosphere. Such a post-treatment heat treatment step may be performed at a temperature above 500°C, for example, 700°C. This post-treatment heat treatment step may facilitate the formation of more defects in the active electrode material. In some cases, the method may include mixing the polytitanium-minority niobate with a carbon source to form a carbon coating on the polytitanium-minority niobate. The mixture of the polytitanium-minority niobate and the carbon source may be heated to form the carbon coating on the polytitanium-minority niobate. Suitable carbon sources include, but are not limited to, carbohydrate materials (e.g., sugars, polymers), conductive carbons (e.g., carbon black), and aromatic carbon materials (e.g., pitch carbon). Carbon coating of the polytitanium-minority niobate may also be performed using chemical vapor deposition or organic pyrolysis. A preferred method for carbon coating involves grinding the active electrode material with a carbon source, then heating the active electrode material and carbon source in a furnace under an inert or reducing atmosphere, causing the carbon source to pyrolyze into carbon that is then coated on the surface of the polytitanium-minority niobate particles. Another preferred method for forming the carbon coating includes mixing the polytitanium-minority niobate with a carbon source, dispersing the polytitanium-minority niobate and carbon source in an aqueous slurry, and then spray drying. The polytitanium-minority niobate and carbon source are then heated in a furnace under an inert or reducing atmosphere, causing the carbon source to pyrolyze into carbon that is then coated on the surface of the polytitanium-minority niobate particles. If the carbon source is conductive carbon, pyrolysis of the material after spray drying is not required. In some cases, the method may include a step of grinding the polytitanium-minority niobate to modify the particle size of the polytitanium-minority niobate. For example, the polytitanium-minority niobate may be processed through one or more processes, including jet milling, sieving, or ball milling. This can provide a more suitable particle size for the desired application of the polytitanium-minority niobate. Furthermore, conventional modification methods (such as doping, compounding, and nano-crystallization) can be used to modify high-titanium, low-niobium niobates. For example, doping modification simply requires adding a small amount of a water- or alcohol-soluble compound containing the doping element during the material preparation process.

[0035] The present invention includes any combination of the above-described aspects and preferred features, unless such a combination is expressly not permitted.

[0036] The beneficial effects of the present invention are:

[0037] (1) The high-titanium-low-niobium niobate active electrode material provided by the present invention is applied to the negative electrode of lithium-ion batteries. 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 high-titanium, low-niobium niobate provided by the present invention is simple to prepare. The battery assembled with other battery components is 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, and frequency and peak-valley regulation in grid-connected energy storage systems. The application prospects are very broad. The present invention provides more options for active negative electrode materials for lithium-ion batteries and can greatly promote the rapid development of high-performance lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

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

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

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

[0047] Figure 9 Ti obtained in Example 3 1.6 Nb 1.52 X-ray diffraction (XRD) pattern of O7 particles;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0066] Figure 28 The carbon-coated Ti obtained in Example 25 1.5 Nb 1.6 O7(C-Ti 1.5 Nb 1.6 O7) Transmission electron microscopy (TEM) images of porous microspheres;

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

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

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

[0070] Figure 32 LiNi obtained in Example 26 0.5 Mn 1.5 O4 / Ti 1.5 Nb 1.6 Cycling performance diagram of O7 full battery at 7C rate. DETAILED DESCRIPTION

[0071] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present 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 only used to explain the present invention and are not intended to limit the present invention.

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

[0073] 0.03 mol titanyl sulfate and 0.032 mol niobium oxalate (hydrated) were dissolved in 300 mL deionized water and stirred to form a uniform aqueous solution. 1.5 Nb 1.6 The inlet temperature of the spray dryer was set to 180 °C, the outlet temperature was set to 84 °C, and the flow rate of the peristaltic pump was set to 20 rpm. The above aqueous solution was spray-dried to obtain Ti 1.5 Nb 1.6 O7 precursor powder. The obtained precursor powder is placed in a muffle furnace and sintered at 1050 ° C for 4 hours to obtain Ti 1.5 Nb 1.6 O7 porous microspheres were sieved using a 300 mesh sieve.

[0074] Half-cell preparation and testing: 80 wt% of a polytitanium-minor niobate, 10 wt% of a binder (polyvinylidene fluoride), and 10 wt% of a 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 roll-pressed to obtain an active material loading of 4–5 mg cm. -2The working electrode was then assembled. A CR2032 half-cell was constructed, in which the electrolyte was 1 M lithium hexafluorophosphate dissolved in a mixed solvent of ethylene carbonate / diethylene carbonate / dimethyl carbonate (volume ratio of 1:1:1), the separator was glass fiber, and the counter electrode was a lithium sheet. The electrochemical test 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 charge rate (charge current density) and discharge rate (discharge current density) are equal, and 1C is set to 250 mA g -1 .

[0075] Figure 1 Ti obtained in Example 1 1.5 Nb 1.6 The X-ray diffraction (XRD) pattern of O7 porous microspheres showed that the Ti 1.5 Nb 1.6 The O7 porous microspheres are a single-phase shear ReO3 type crystal structure with the same crystal structure unit as TiNb2O7 (3×3 octahedrons connected in order with common edges and common points). Figure 2 Ti obtained in Example 1 1.5 Nb 1.6 Scanning electron microscope (SEM) photos of O7 porous microspheres show that Ti 1.5 Nb 1.6 The primary particle size of O7 porous microspheres is between 0.1–0.4 μm, and the secondary particle size is between 0.5–2.5 μm. Figure 3 Ti obtained in Example 1 1.5 Nb 1.6 Charge and discharge curves of O7 / Li half-cell at different rates. The active material loading is 5.01 mg cm -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 first cycle coulombic efficiency is 90.5%, and the reversible specific capacity at 5C is 147 mAhg -1 . Figure 4 Ti obtained in Example 1 1.5 Nb 1.6 Cycling performance of O7 / Li half-cell at 5C rate. Active material loading is 5.01 mg cm -2 Ti 1.5 Nb 1.6 The capacity retention rate of the O7 / Li half-cell after 500 cycles at 5C is 83.1% (refer to the second cycle).

[0076] Example 2: Preparation of high-titanium and low-niobium niobate by solvent thermal method

[0077] 0.0035 mol of tetraisopropyl titanate and 0.0042 mol of niobium ethoxide were dissolved in 80 mL of ethanol and stirred to form a uniform ethanol solution. 1.4 Nb 1.68 O7 precursor powder. The above solution was transferred to a 100 mL reactor and the temperature was raised to 200 °C (heating rate of 4 °C / min) using an external heating method and maintained at 200 °C for 24 hours. After the reaction was completed, the temperature was cooled to room temperature. The suspension in the reactor was separated by centrifugation to obtain solid powder and washed. The obtained precursor powder was placed in a muffle furnace and sintered at 800 °C for 20 hours to obtain Ti 1.4 Nb 1.68 O7 porous microspheres were sieved using a 300-mesh sieve. The subsequent half-cell preparation and testing methods were the same as in Example 1.

[0078] Figure 5 Ti obtained in Example 2 1.4 Nb 1.68 X-ray diffraction (XRD) pattern of O7 porous microspheres shows that Ti 1.4 Nb 1.68 The O7 porous microspheres are a single-phase shear ReO3 type crystal structure with the same crystal structure unit as TiNb2O7 (3×3 octahedrons connected in order with common edges and common points). Figure 6 Ti obtained in Example 2 1.4 Nb 1.68 Scanning electron microscope (SEM) photos of O7 porous microspheres show that Ti 1.4 Nb 1.68 The primary particle size of O7 porous microspheres is between 0.05–0.2 μm, and the secondary particle size is between 0.5–3 μm. Figure 7 Ti obtained in Example 2 1.4 Nb 1.68 Charge and discharge curves of O7 / Li half-cell at different rates. The active material loading is 4.96 mg cm -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 first cycle coulombic efficiency is 94.0%, and the reversible specific capacity at 5C is 135 mAhg -1 . Figure 8 Ti obtained in Example 2 1.4 Nb 1.68Cycling performance of O7 / Li half-cell at 5C rate. The active material loading is 4.96 mg cm -2 Ti 1.4 Nb 1.68 The capacity retention rate of the O7 / Li half-cell after 500 cycles at 5C is 78.4% (refer to the second cycle).

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

[0080] 0.032 mol titanium chloride and 0.0304 mol niobium oxalate (hydrated) were dissolved in 500 mL ethanol-water (volume ratio 1:1) and stirred to form a uniform alcohol-water solution. 1.6 Nb 1.52 O7 precursor powder. Heat the above solution with a heater to allow hydrolysis to occur, obtaining a gel-like solid, and continue to evaporate the solvent. The resulting solid is mixed with ethanol and ground in a planetary ball mill. The resulting slurry is filtered and washed with ethanol to obtain Ti 1.6 Nb 1.52 O7 precursor powder. The obtained precursor powder is placed in a muffle furnace and sintered at 950 ° C for 12 hours to obtain Ti 1.6 Nb 1.52 O7 porous microspheres were sieved using a 300-mesh sieve. The subsequent half-cell preparation and testing methods were the same as in Example 1.

[0081] Figure 9 Ti obtained in Example 3 1.6 Nb 1.52 X-ray diffraction (XRD) pattern of O7 particles shows that Ti prepared by sol-gel method 1.6 Nb 1.52 The O7 particles are a single-phase sheared ReO3 type crystal structure with the same crystal structure unit as TiNb2O7 (3×3 octahedrons connected in order by common edges and common points). Figure 10 Ti obtained in Example 3 1.6 Nb 1.52 Scanning electron microscope (SEM) image of O7 particles shows that Ti 1.6 Nb 1.52 The primary particle size of O7 particles ranges from 0.4 to 0.6 μm, and the secondary particle size ranges from 2 to 20 μm. Figure 11 Ti obtained in Example 3 1.6 Nb 1.52 Charge and discharge curves of O7 / Li half-cell at different rates. The active material loading is 5.05 mg cm -2 Ti 1.6 Nb 1.52The reversible specific capacity of the O7 / Li half-cell at 0.1C is 283 mAh g -1 The first cycle coulombic efficiency is 93.8%, and the reversible specific capacity at 5C is 140 mAh g -1 . Figure 12 Ti obtained in Example 3 1.6 Nb 1.52 Cycling performance of O7 / Li half-cell at 5C rate. Active material loading is 5.05 mg cm -2 Ti 1.6 Nb 1.52 The capacity retention rate of the O7 / Li half-cell after 500 cycles at 5C is 87.9% (refer to the second cycle).

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

[0083] 0.026 mol titanyl sulfate and 0.0352 mol ammonium niobium oxalate (hydrated) were dissolved in 300 mL deionized water and stirred to form a uniform aqueous solution. Ti was prepared by direct evaporation. 1.3 Nb 1.76 O7 precursor powder. Place the above solution in a beaker, heat it in a water bath at 80 °C and stir continuously. After the water in the beaker is completely evaporated, Ti 1.3 Nb 1.76 O7 precursor powder. The obtained precursor powder is placed in a muffle furnace and sintered at 1100 ℃ for 2 hours to obtain Ti 1.3 Nb 1.76 O7 particles were sieved using a 300-mesh sieve. The subsequent half-cell preparation and testing methods were the same as in Example 1.

[0084] Figure 13 Ti obtained in Example 4 1.3 Nb 1.76 X-ray diffraction (XRD) pattern of O7 particles shows that Ti prepared by direct evaporation method 1.3 Nb 1.76 The O7 particles are a single-phase sheared ReO3 type crystal structure with the same crystal structure unit as TiNb2O7 (3×3 octahedrons connected in order by common edges and common points). Figure 14 Ti obtained in Example 4 1.3 Nb 1.76 Scanning electron microscope (SEM) image of O7 particles shows that Ti 1.3 Nb 1.76 The particle size of O7 particles ranges from 0.5–4 μm. Figure 15 Ti obtained in Example 4 1.3 Nb 1.76Charge and discharge curves of O7 / Li half-cell at different rates. The active material loading is 4.95 mg cm -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 first cycle coulombic efficiency is 90.8%, and the reversible specific capacity at 5C is 138 mAh g -1 . Figure 16 Ti obtained in Example 4 1.3 Nb 1.76 Cycling performance of O7 / Li half-cell at 5C rate. Active material loading is 4.95 mg cm -2 Ti 1.3 Nb 1.76 The capacity retention rate of the O7 / Li half-cell after 500 cycles at 5C is 86.3% (refer to the second cycle).

[0085] Example 5: Preparation of high-titanium and low-niobium niobate by coprecipitation

[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 uniform aqueous solution. 1.2 Nb 1.84 The above solution was stirred at a constant speed and ammonia was added continuously until a complete precipitation was produced. The obtained precipitate was washed 3 times with distilled water and ethanol and dried to obtain Ti 1.2 Nb 1.84 O7 precursor powder. The obtained precursor powder is placed in a muffle furnace and sintered at 1000 ℃ for 8 hours to obtain Ti 1.2 Nb 1.84 O7 porous microspheres were sieved using a 300-mesh sieve. The subsequent half-cell preparation and testing methods were the same as in Example 1.

[0087] Figure 17 Ti obtained in Example 5 1.2 Nb 1.84 The X-ray diffraction (XRD) pattern of O7 porous microspheres shows that the Ti 1.2 Nb 1.84 The O7 porous microspheres are a single-phase shear ReO3 type crystal structure with the same crystal structure unit as TiNb2O7 (3×3 octahedrons connected in order with common edges and common points). Figure 18 Ti obtained in Example 5 1.2 Nb 1.84 Scanning electron microscope (SEM) photos of O7 porous microspheres show that Ti 1.2 Nb1.84 The primary particle size of O7 porous microspheres is between 0.2–0.6 μm, and the secondary particle size is between 0.8–2.5 μm. Figure 19 Ti obtained in Example 5 1.2 Nb 1.84 Charge and discharge curves of O7 / Li half-cell at different rates. The active material loading is 5.03 mg cm -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 first cycle coulombic efficiency is 90.7%, and the reversible specific capacity at 5C is 131 mAh g -1 . Figure 20 Ti obtained in Example 5 1.2 Nb 1.84 Cycling performance of O7 / Li half-cell at 5C rate. Active material loading is 5.03 mg cm -2 Ti 1.2 Nb 1.84 The capacity retention rate of the O7 / Li half-cell after 500 cycles at 5C is 85.5% (refer to the second cycle).

[0088] Comparative Example 1: Preparation of TiNb2O7 micron particles by traditional solid phase sintering method

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

[0090] Figure 21 The XRD pattern of the TiNb2O7 micron particles obtained in Comparative Example 1 shows that the TiNb2O7 micron particles prepared by the traditional solid-phase sintering method have a single-phase shear ReO3 type crystal structure (the crystal structure unit is a 3×3 octahedron connected in an orderly manner with common edges and common points). Figure 22 This is a scanning electron microscope photograph of the TiNb2O7 micron particles obtained in Comparative Example 1. It can be seen that the particle size of the TiNb2O7 micron particles is between 1 and 5 μm. Figure 23 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 -2The reversible specific capacity of the TiNb2O7 / Li half-cell at 0.1C is 268 mAh g -1 The first cycle coulombic efficiency is 96.1%, and the reversible specific capacity at 5C is 177 mAh g -1 . Figure 24 The cycling performance of the TiNb2O7 / Li half-cell obtained in Comparative Example 1 at a rate of 5C is shown. The active material loading is 4.92 mg cm -2 The capacity retention of the TiNb2O7 / Li half-cell after 500 cycles at 5C is only 33.6% (refer to the second cycle). This poor cycling performance is mainly due to the excessively large micron size of the TiNb2O7 particles.

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

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

[0093] Figure 25 The XRD pattern of the TiNb2O7 porous microspheres obtained in Comparative Example 2 shows that the TiNb2O7 porous microspheres prepared by spray drying are a single-phase shear ReO3 type crystal structure, but have the same 10 O 29 The same crystal structure unit (3×4 octahedra connected in an orderly manner with common edges and points). Figure 26 This is a scanning electron microscope photograph of the TiNb2O7 porous microspheres obtained in Comparative Example 2. It can be seen that the primary particle size of the TiNb2O7 porous microspheres is between 0.1-0.3 μm, and the secondary particle size is between 0.5-2 μm. Figure 27 The charge-discharge curves of the TiNb2O7 / Li half-cell obtained in Comparative Example 2 at different rates. The active material loading is 4.71 mg cm -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%; there is almost no capacity at 5C, and the rate performance is very poor. 1.5 Nb 1.6 The rate performance of TiO7 porous microspheres is significantly better than that of TiNb2O7 porous microspheres in Comparative Example 2. 1.5 Nb 1.6 O7 contains at least one of a large number of cation interstitials and oxygen ion vacancies, and these defects significantly enhance the electrochemical kinetics.

[0094] Obviously, compared with the TiNb2O7 micron particles prepared by the traditional solid phase sintering method, the TiNb2O7 micron particles prepared by the liquid phase method based on the precursor solution are better than those prepared by the traditional solid phase sintering method. 1.5 Nb 1.6 The O7 material (a representative material of high-titanium, low-niobium niobates) exhibits comparable reversible specific capacity, initial coulombic efficiency, and rate performance, yet significantly improves cycling performance and utilizes a 17% reduction in niobium content. These advantages, including high safety, initial coulombic efficiency, specific capacity, rate performance, and cycling performance, along with lower cost, fully demonstrate that high-titanium, low-niobium niobates are promising anode materials for lithium-ion batteries.

[0095] Niobates with high titanium content and low niobium content were prepared by a liquid phase method based on a precursor solution. Examples 6-24 are shown in Table 1.

[0096] Table 1

[0097]

[0098]

[0099] Example 25: Carbon coating of high-titanium-low-niobium niobate

[0100] The 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. 1.5 Nb 1.6 O7 porous microspheres, 0.04 g lactose, 30 mL deionized water. The above slurry was placed in a beaker, heated in a water bath at 80 ° C and stirred continuously. After the water in the beaker was completely evaporated, carbon-coated Ti was obtained. 1.5 Nb 1.6 O7(C-Ti 1.5 Nb 1.6 The obtained precursor powder was placed in a tube furnace and heat treated at 800 ° C for 2 h in an Ar atmosphere to obtain C-Ti 1.5 Nb 1.6 O7 porous microspheres (carbon content 1.5 wt%) were sieved using a 300-mesh sieve.

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

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

[0103] Example 26: LiNi 0.5 Mn 1.5 O4 / Ti 1.5 Nb 1.6 O7 full battery

[0104] Using Ti of Example 1 1.5 Nb 1.6 O7 porous microspheres are used as negative electrode materials, commercial LiNi 0.5 Mn 1.5 O4 is the positive electrode material. 92 wt% Ti 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 roll-pressed to obtain an active material loading of 18–20 mg cm -2 Ti 1.5 Nb 1.6 O7 negative electrode. LiNi 0.5 Mn 1.5 O4 cathode and Ti 1.5 Nb1.6 The preparation method of the O7 negative electrode is the same, except that aluminum foil is used as the current collector. The ratio of the negative electrode capacity to the positive electrode capacity is 1.1:1. Then, a CR2032 full battery is assembled, in which the electrolyte is obtained by dissolving 1 M lithium hexafluorophosphate in a mixed solvent of ethylene carbonate / diethylene carbonate / dimethyl carbonate (volume ratio is 1:1:1) and the separator is a Cegard 2400 polypropylene film. The electrochemical test temperature is about 25 °C. For each cycle of electrochemical testing, the voltage window is 1.5–3.5 V. The charge rate (charge current density) and discharge rate (discharge current density) are equal, and 1C is set to 140 mA g -1 .

[0105] Figure 31 LiNi obtained in Example 26 0.5 Mn 1.5 O4 / Ti 1.5 Nb 1.6 The charge and discharge curves of the O7 full battery at different rates. The reversible specific capacity of the full battery at 0.5C is 137 mAh g -1 The reversible specific capacity at 7C is 75 mAh g -1 . Figure 32 LiNi obtained in Example 26 0.5 Mn 1.5 O4 / Ti 1.5 Nb 1.6 The cycling performance of the O7 full cell at 7C. After 4,000 cycles at 7C, the full cell maintained a capacity of 86.4% (see the second cycle). This demonstrates that lithium-ion batteries based on high-titanium, low-niobium niobate anodes can possess superior electrochemical performance.

[0106] It will be easily understood by those skilled in the art 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 in the scope of protection of the present invention.

Claims

1. A method for preparing a single-phase niobate, characterized in that: The general formula of the single-phase niobate is Ti x Nb y O z ; Among them, 0.171≤ x / z ≤0.215 and 0.228≤ y / z ≤0.263; The single-phase niobate has a sheared ReO3 type crystal structure; its crystal structure unit is a 3×3 octahedron connected in an orderly manner with common edges and common points; The specific steps include: (1) dissolving titanium source and niobium source raw materials in any one of water, alcohol and alcohol-water solvent to form a solution; (2) treating the solution by any one of spray drying, solvothermal method, sol-gel method, direct evaporation to dryness, and coprecipitation method to obtain a precursor powder; (3) Sintering the precursor powder in the temperature range of 700–1200 °C to form a single-phase niobate; In step (1), the titanium source is a titanium compound soluble in water or alcohol; the titanium compound is selected from titanyl sulfate, titanium chloride, tetraisopropyl titanate, and tetrabutyl titanate; the niobium source is a niobium compound soluble in water or alcohol; the niobium compound is selected from niobium oxalate, ammonium niobium oxalate, niobium chloride, and niobium ethoxide; The molar ratio of the titanium source to the niobium source is x : y .

2. The preparation method according to claim 1, characterized in that The precursor powder is sintered in a gaseous atmosphere selected from one or more of air, O2, N2, Ar, He, CO2, CO and H2; the sintering time is 0.5-24 hours.

3. A single-phase niobate prepared by the preparation method according to claim 1 or 2, characterized in that: The general formula of the single-phase niobate is Ti x Nb y O z ; Among them, 0.171≤ x / z ≤0.215 and 0.228≤ y / z ≤0.263; The single-phase niobate has a sheared ReO3 type crystal structure; its crystal structure unit is a 3×3 octahedron connected in order by sharing edges and points.

4. The single-phase niobate according to claim 3, characterized in that The single-phase niobate contains a doping element.

5. A single-phase niobate active electrode material, characterized in that: The active electrode material comprises primary particles and / or secondary particles of the single-phase niobate according to claim 3 or 4.

6. The single-phase niobate active electrode material according to claim 5, 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.

7. The single-phase niobate active electrode material according to claim 5, characterized in that: The active electrode material comprises a carbon layer formed on the surface of primary particles and / or secondary particles.

8. 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.

9. The single-phase niobate active electrode material according to any one of claims 6 to 8, characterized in that: Also contains Li.

10. A method for preparing a single-phase niobate active electrode material according to any one of claims 5 to 9, characterized in that: The single-phase niobate according to claim 3 or 4 is subjected to one or more of the following post-treatment steps: (1) Heat treatment of single-phase niobate; (2) Carbon coating of single-phase niobate; (3) Mixing single-phase niobate with conductive materials; (4) Grinding of single-phase niobate to change the particle size of the active electrode material.

11. Use of the single-phase niobate according to claim 3 or 4 or the single-phase niobate active electrode material according to any one of claims 5 to 9 as a negative electrode material or as a component of a negative electrode material in a lithium ion battery.

12. An electrochemical device comprising a negative electrode, a positive electrode, an electrolyte and a separator disposed between the negative electrode and the positive electrode, characterized in that: The negative electrode comprises the single-phase niobate according to claim 3 or 4 or the single-phase niobate active electrode material according to any one of claims 5 to 9.

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