A high-capacity porous niobium pentoxide material, a preparation method and application thereof

Abstract

The application relates to a high-capacity porous niobium pentoxide material and a preparation method and application thereof, relates to niobium pentoxide and preparation and application thereof, and aims to solve the technical problems of low conductivity and slow ion diffusion of existing orthogonal phase niobium pentoxide materials. The material is formed by interconnection of 100-300 nm niobium pentoxide matrix nanoparticles, growth of 10-30 nm secondary nanoparticles on the surface, and a 'raspberry-like' multi-level assembly morphology; the material has a pore diameter of 2-20 nm, a specific surface area of 15-45 m 2 / g; and has an orthogonal phase niobium pentoxide structure and carbon doping characteristics. The material is prepared by using a surfactant containing a quaternary ammonium cation as a soft template, utilizing electrostatic-coordination synergistic action to drive niobium salt and organic quaternary ammonium cation assembly, and high-temperature sintering in an inert atmosphere. When used as a negative electrode of a lithium ion battery, the material reaches a capacity of 350 mAh / g at a current density of 0.1 A / g, and can be used in the field of fast-charging type alkali metal ion batteries.

Description

Technical Field

[0001] This application belongs to the field of new energy materials technology, and relates to a high-capacity porous niobium pentoxide material, its preparation method and application. Background Technology

[0002] With the rapid development of portable electronic products, hybrid / electric vehicles, and balanced smart grids, the market demand for energy storage systems with high-rate charge / discharge capabilities is increasing daily. Lithium-ion batteries, due to their high energy density, long cycle life, and environmental friendliness, have become the core carrier of the new energy system. However, the fast-charging safety hazards (lithium dendrite formation) of commercial graphite anodes and the low theoretical capacity (175 mAh / g) of lithium titanate (LTO) anodes limit their application in high-power scenarios. Orthorhombic niobium pentoxide (T-Nb2O5) has a high operating potential (~1.6 V vs. Li...). + The intrinsic safety derived from Li, the low volumetric strain (<4%) stability of the Wadsley-Roth layered open framework, and the rapid ion insertion / extraction mechanism dominated by pseudocapacitance make T-Nb2O5 an ideal candidate material for high-power anodes. However, the development of T-Nb2O5 anode materials faces two major bottlenecks: one is the extremely low intrinsic conductivity (~3×10⁻⁶). -6 The high S / cm ratio leads to severe polarization at high magnification, and the slow ion diffusion kinetics (Li) + The diffusion coefficient is only ~10 -12 cm 2 / s, which is four orders of magnitude lower than that of graphite.

[0003] To overcome these limitations, existing technologies mainly employ three strategies: carbon composite, element doping, and nano-sizing. While these strategies have led to significant progress in the research of T-Nb2O5 anode materials, they still struggle to simultaneously address the issues of low conductivity and slow ion diffusion, and involve significant compromises in terms of process complexity, structural stability, or economic efficiency. Summary of the Invention

[0004] This invention aims to address the technical problems of low conductivity and slow ion diffusion in existing T-Nb2O5 anode materials by providing a high-capacity porous niobium pentoxide material, its preparation method, and its applications. This invention improves the low conductivity and slow ion diffusion of existing orthorhombic niobium pentoxide anode materials through a dual structure-composition regulation strategy, achieving a lithium storage capacity that surpasses the theoretical capacity.

[0005] The high-capacity porous niobium pentoxide material of this invention is composed of interconnected niobium pentoxide matrix nanoparticles with a size of 100-300 nm, and secondary niobium pentoxide nanoparticles with a size of 10-30 nm grown on its surface, exhibiting a unique "raspberry-like" hierarchical assembly morphology; it has mesoporous pores with a pore size of 2-20 nm and a specific surface area of ​​15-45 m². 2 / g; It has an orthorhombic niobium pentoxide structure and carbon doping characteristics.

[0006] The above-mentioned method for preparing high-capacity porous niobium pentoxide material includes the following steps:

[0007] 1. Add an ethanol solution containing an organic quaternary ammonium cation and triethanolamine to a mixed solvent of ethanol and water to obtain a mixture; heat the mixture to 50~70 ℃ under stirring and maintain the temperature for 0.5~3.0 h to react and obtain a micelle solution.

[0008] 2. Add niobium salt aqueous solution to micelle solution, stir at a constant speed at 50~90 ℃ for 4~12 h to carry out assembly reaction, and after centrifugation and freeze drying, obtain niobium oxygen precursor with organic quaternary ammonium cation complex.

[0009] 3. Place the niobium-oxygen precursor into a high-temperature furnace and heat it to 500~800 ℃ in an inert gas atmosphere for 2~5 h for high-temperature sintering to obtain high-capacity porous niobium pentoxide material.

[0010] Preferably, the surfactant containing organic quaternary ammonium cation in step one is one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.

[0011] Preferably, the concentration of the surfactant containing organic quaternary ammonium cations in step one is 0.01~0.06 g / mL. The surfactant containing organic quaternary ammonium cations plays a dual role in structure-composition regulation during the synthesis of niobium pentoxide materials. Firstly, it acts as a micellar soft template, guiding the hydrolysis and assembly of niobium salts through electrostatic-coordination synergy, thereby forming a porous structure in the niobium-oxygen precursor nanospheres. Secondly, it acts as a carbon source, in-situ incorporating into the niobium pentoxide lattice structure during high-temperature sintering. The amount of this surfactant added directly affects the pore structure of the niobium-oxygen precursor, which in turn directly affects the distribution of the doped carbon source on the pore surface. When the amount added is excessive… SmallWhen the surfactant is added, it may not provide enough template or structure guiding effect, resulting in low yield of niobium-oxygen precursor, few pore structures and insufficient carbon doping. When the amount added is too large, due to the excessive electrostatic-coordination force, the niobium-oxygen precursor will seriously agglomerate, which is not conducive to the formation of "raspberry" multi-level assembly morphology. At the same time, it will also change the pore shape of the material. Excessive surfactant also increases the difficulty of purification and separation.

[0012] Preferably, the concentration of triethanolamine in the ethanol solution of triethanolamine in step one is 0.35 g / mL, and the mass ratio of the surfactant containing the organic quaternary ammonium cation to the volume ratio of the ethanol solution of triethanolamine is 1 g: (0.25~1.5) mL. Triethanolamine acts as a catalyst in the synthesis reaction of niobium-oxygen precursors, regulating the hydrolysis of niobium oxalate and the nucleation rate of nanoparticles, thereby controlling the size and uniformity of the matrix particles and secondary nanoparticles of the niobium-oxygen precursor. When the amount of triethanolamine added is too small, the reaction rate is too slow, resulting in niobium-oxygen precursor particles that are too small; when the amount of triethanolamine added is too large, it is not conducive to controlling the reaction rate, leading to rapid growth of niobium-oxygen precursor nanoparticles, ultimately resulting in excessively large particle sizes and poor uniformity.

[0013] Preferably, in the mixed solvent of ethanol and water described in step one, the volume ratio of ethanol to water is (2~5):1.

[0014] Preferably, the niobium salt mentioned in step two is niobium oxalate, and the concentration of the niobium salt aqueous solution is 0.04~0.10 mol / L. The niobium oxalate is the sole niobium source. When the concentration of the niobium oxalate aqueous solution is too low, the yield of the niobium-oxygen precursor is low due to insufficient niobium source, and secondly, complete matrix particles cannot be formed. When the concentration of the niobium oxalate aqueous solution is too high, the collision opportunities between niobium source molecules increase, resulting in more nucleation and growth points, and the particle size of the formed niobium-oxygen precursor is too small.

[0015] Preferably, the volume ratio of the niobium salt aqueous solution to the micelle solution in step two is 1:(1~5).

[0016] Preferably, the inert gas mentioned in step three is one or more of nitrogen and argon.

[0017] Preferably, the inert gas flow rate in step three is 20~60 mL / min.

[0018] The aforementioned high-capacity porous niobium pentoxide material is used as a negative electrode in lithium-ion batteries.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] The high-capacity porous niobium pentoxide material provided by this invention, on the one hand, is composed of interconnected matrix nanoparticles with a size of 100~300 nm, and its surface is covered with many secondary nanoparticles with a size of 10~30 nm, exhibiting a unique "raspberry-like" hierarchical assembly morphology; on the other hand, it has a rich porous structure and high specific surface area, with pore sizes mainly distributed in the range of 2~20 nm, and has an orthorhombic niobium pentoxide structure and carbon doping characteristics. Such structure-composition dual regulation promotes full contact and penetration of electrolyte with material, while providing abundant electrochemical active sites, significantly improving the low conductivity and slow ion diffusion shortcomings of orthorhombic niobium pentoxide anode materials in the prior art.

[0021] The preparation method of this invention uses a surfactant containing organic quaternary ammonium cations as a soft template for guidance. Electrostatic-coordination synergy drives the assembly of niobium salt precursors and organic quaternary ammonium cations to form an organic-inorganic composite. High-temperature sintering in an inert atmosphere constructs a porous orthorhombic niobium pentoxide material with a unique "raspberry-like" hierarchical morphology, while simultaneously achieving in-situ carbon doping modification. This method is simple and efficient; by adjusting process parameters, the particle size and pore size distribution of the material can be flexibly controlled, exhibiting good repeatability and potential for large-scale production. Furthermore, high-temperature sintering of the precursor in an inert gas results in incomplete oxidation of the niobium-oxygen precursor, forming orthorhombic niobium pentoxide (T-Nb₂O₃) with partial oxygen vacancies. 5-x This improves its intrinsic conductivity.

[0022] When the high-capacity porous niobium pentoxide material provided by this invention is applied to the negative electrode of a lithium-ion battery, its lithium storage capacity exceeds its theoretical value, reaching a capacity of 350 mAh / g at a current density of 0.1 A / g, and it also exhibits excellent rate performance and cycle stability. Attached Figure Description

[0023] Figure 1 Scanning electron microscope images of niobium pentoxide materials prepared in Example 1 and Comparative Example 1; a) Example 1; b) Example 2; c) Example 3; d) Example 4; e) Example 5; f) Comparative Example 1;

[0024] Figure 2 The X-ray diffraction patterns of niobium pentoxide materials prepared in Examples 1-5 and Comparative Example 1 are shown below.

[0025] Figure 3 Nitrogen isothermal adsorption-desorption curves of the niobium pentoxide material prepared in Example 1: a) and corresponding pore size distribution curves: b).

[0026] Figure 4 The nitrogen isothermal adsorption-desorption curve of the niobium pentoxide material prepared in Comparative Example 1 is shown.

[0027] Figure 5 Thermogravimetric analysis curves of niobium pentoxide materials prepared in Example 1 and Comparative Example 1 are shown.

[0028] Figure 6 The electron paramagnetic resonance spectrum of the niobium pentoxide material prepared in Example 1;

[0029] Figure 7 Cyclic voltammetry curves of the niobium pentoxide material prepared in Example 1 as a negative electrode of a lithium-ion battery at a scan rate of 0.2 mV / s;

[0030] Figure 8 The rate performance diagram of the niobium pentoxide material prepared in Example 1 as the negative electrode of a lithium-ion battery is shown.

[0031] Figure 9 The rate performance of the niobium pentoxide material prepared in Comparative Example 1 as the negative electrode of a lithium-ion battery is shown in the figure.

[0032] Figure 10 The graph shows the cycling performance of the niobium pentoxide material prepared in Example 1 as a negative electrode in a lithium-ion battery at a current density of 0.1 A / g.

[0033] Figure 11 The graph shows the cycling performance of the niobium pentoxide material prepared in Example 1 as a negative electrode of a lithium-ion battery at a current density of 1.0 A / g. Detailed Implementation

[0034] The technical methods of this application will be further described below with reference to specific embodiments.

[0035] Example 1: The preparation method of the high-capacity porous niobium pentoxide material 1 in this example is carried out according to the following steps:

[0036] 1. Add 1.0 g of hexadecyltrimethylammonium bromide (CTAB) and 0.75 mL of a 0.35 g / mL triethanolamine (TEA) ethanol solution to 50 mL of a mixed solvent of ethanol and water in a volume ratio of 4:1 to obtain a mixture; heat the mixture to 60 °C and maintain the temperature for 0.5 h under stirring to obtain a micelle solution;

[0037] 2. Add 20 mL of 0.08 M niobate aqueous solution to the micelle solution and stir at a constant speed at 80 °C for 8 h to carry out the assembly reaction. After centrifugation and freeze drying, the niobium-oxygen precursor with organic quaternary ammonium cation complex is obtained.

[0038] 3. The niobium oxide precursor is placed in an alumina boat, which is then placed in a tube furnace. Nitrogen gas is continuously introduced at a flow rate of 50 mL / min, while the temperature is raised to 300 ℃ at a rate of 2 ℃ / min, and then raised to 700 ℃ at a rate of 10 ℃ / min and held for 2 h for high-temperature sintering. After cooling to room temperature, high-capacity porous niobium pentoxide material is obtained.

[0039] Example 2: The preparation method of the high-capacity porous niobium pentoxide material 2 in this example is carried out according to the following steps:

[0040] 1. Add 1.0 g CTAB and 0.75 mL of a 0.35 g / mL triethanolamine ethanol solution to 50 mL of a mixed solvent with an ethanol / water volume ratio of 4:1 to obtain a mixture; heat the mixture to 60 °C and maintain the temperature for 0.5 h under stirring to obtain a micelle solution;

[0041] 2. Add 20 mL of 0.06 M niobate aqueous solution to the micelle solution and stir at a constant speed for 8 h at 80 ℃ to carry out the assembly reaction. After centrifugation and freeze drying, the niobium-oxygen precursor with organic quaternary ammonium cation complex is obtained.

[0042] 3. The niobium oxide precursor was placed in an alumina boat, which was then placed in a tube furnace. Nitrogen gas was continuously introduced at a flow rate of 50 mL / min, while the temperature was raised to 300 ℃ at a rate of 2 ℃ / min, and then raised to 700 ℃ at a rate of 10 ℃ / min and held for 2 h for high-temperature sintering. After cooling to room temperature, high-capacity porous niobium pentoxide material was obtained.

[0043] Example 3: The preparation method of the high-capacity porous niobium pentoxide material 3 in this example is carried out according to the following steps:

[0044] 1. Add 1g CTAB and 0.75 mL of a 0.35 g / mL triethanolamine ethanol solution to 50 mL of a mixed solvent with an ethanol / water volume ratio of 4:1 to obtain a mixture; heat the mixture to 60 °C and maintain the temperature for 0.5 h under stirring to obtain a micelle solution.

[0045] 2. Add 20 mL of 0.1 M niobate aqueous solution to the micelle solution and stir at a constant speed for 8 h at 80 ℃ to carry out the assembly reaction. After centrifugation and freeze drying, the niobium-oxygen precursor with organic quaternary ammonium cation complex is obtained.

[0046] 3. The niobium oxide precursor was placed in an alumina boat, which was then placed in a tube furnace. Nitrogen gas was continuously introduced at a flow rate of 50 mL / min, while the temperature was raised to 300 ℃ at a rate of 2 ℃ / min, and then raised to 700 ℃ at a rate of 10 ℃ / min and held for 2 h for high-temperature sintering. After cooling to room temperature, high-capacity porous niobium pentoxide material was obtained.

[0047] Example 4: The preparation method of the high-capacity porous niobium pentoxide material 4 in this example is carried out according to the following steps:

[0048] 1. Add 0.5 g CTAB and 0.75 mL of 0.35 g / mL TEA ethanol solution to 50 mL of ethanol / water mixed solvent with a volume ratio of 4:1 to obtain a mixed solution; heat the mixed solution to 60 °C and maintain the temperature for 0.5 h under stirring to obtain a micelle solution.

[0049] 2. Add 20 mL of 0.08 M niobate aqueous solution to the micelle solution and stir at a constant speed for 8 h at a temperature of 80 ℃ to carry out the assembly reaction. After centrifugation and freeze drying, the niobium-oxygen precursor with organic quaternary ammonium cation complex is obtained.

[0050] 3. The niobium oxide precursor was placed in an alumina boat, which was then placed in a tube furnace. Nitrogen gas was continuously introduced at a flow rate of 50 mL / min, while the temperature was raised to 300 ℃ at a rate of 2 ℃ / min, and then raised to 700 ℃ at a rate of 10 ℃ / min and held for 2 h for high-temperature sintering. After cooling to room temperature, high-capacity porous niobium pentoxide material was obtained.

[0051] Example 5: The preparation method of the high-capacity porous niobium pentoxide material 5 in this example is carried out according to the following steps:

[0052] 1. Add 3 g CTAB and 0.75 mL of a 0.35 g / mL triethanolamine ethanol solution to 50 mL of a mixed solvent with an ethanol / water volume ratio of 4:1 to obtain a mixture; heat the mixture to 60 °C and maintain the temperature for 0.5 h under stirring to obtain a micelle solution.

[0053] 2. Add 20 mL of 0.08 M niobate aqueous solution to the micelle solution and stir at a constant speed for 8 h at a temperature of 80 ℃ to carry out the assembly reaction. After centrifugation and freeze drying, the niobium-oxygen precursor with organic quaternary ammonium cation complex is obtained.

[0054] 3. The niobium oxide precursor was placed in an alumina boat, which was then placed in a tube furnace. Nitrogen gas was continuously introduced at a flow rate of 50 mL / min, while the temperature was raised to 300 ℃ at a rate of 2 ℃ / min, and then raised to 700 ℃ at a rate of 10 ℃ / min and held for 2 h for high-temperature sintering. After cooling to room temperature, high-capacity porous niobium pentoxide material was obtained.

[0055] Comparative Example 1: This comparative example is for the preparation of niobium pentoxide material without the addition of surfactant. The specific steps are as follows:

[0056] 1. Add 0.75 mL of a 0.35 g / mL triethanolamine ethanol solution to 50 mL of a mixed solvent with an ethanol / water volume ratio of 4:1 to obtain a mixed solution; heat the mixed solution to 60 °C and stir for 0.5 h, then add 20 mL of a 0.08 M niobate aqueous solution, continue stirring at 80 °C for 8 h, add deionized water, centrifuge, and freeze-dry to obtain the niobium-oxygen precursor material;

[0057] 2. The niobium oxide precursor material is placed in an alumina boat, which is then placed in a tube furnace. Nitrogen gas is continuously introduced at a flow rate of 50 mL / min, while the temperature is raised to 300 ℃ at a rate of 2 ℃ / min, and then raised to 700 ℃ at a rate of 10 ℃ / min and held for 2 h for high-temperature sintering. After cooling to room temperature, niobium pentoxide material without surfactant is obtained.

[0058] Figure 1 Scanning electron microscope images of niobium pentoxide materials obtained in Examples 1-5 and Comparative Example 1; from Figure 1 The results show that the niobium pentoxide materials obtained in Examples 1-5 and Comparative Example 1 all formed matrix particles with a particle size of 100-300 nm. Numerous secondary nanoparticles with a size of 10-30 nm were anchored on their surfaces, exhibiting an overall "raspberry-like" multi-level nano-assembly structure. The irregular matrix particles were interconnected, but the boundaries between particles were clear, with no obvious agglomeration, which facilitates electrolyte penetration and lithium-ion transport. In the materials of Examples 1-5, with the increase of niobium source concentration or CTAB concentration, the niobium-oxygen precursor gradually agglomerated and adhered to form larger and more irregular matrix particles.

[0059] Figure 2 The X-ray diffraction patterns of the niobium pentoxide materials obtained in Examples 1-5 and Comparative Example 1 are shown below. Figure 2The X-ray diffraction analysis results show that the niobium pentoxide materials prepared in Examples 1-5 and Comparative Example 1 all have high crystallinity and can correspond well to the standard card of orthorhombic niobium pentoxide (PDF#30-0873), indicating that Examples 1-5 and Comparative Example 1 all formed orthorhombic niobium pentoxide.

[0060] Figure 3 This is the nitrogen isothermal adsorption-desorption curve of the niobium pentoxide material obtained in Example 1. Figure 3 It can be seen that the nitrogen isothermal adsorption-desorption curve of the high-capacity porous niobium pentoxide material prepared in Example 1 is a typical type IV isotherm, indicating the presence of a large number of mesoporous structures in the material. The adsorption-desorption characteristics in the low-pressure section also indicate the presence of a certain amount of micropores. The specific surface area of ​​the niobium pentoxide material in Example 1 is 43.1 m². 2 / g, as can be seen from the corresponding pore size distribution curve, the pore size is mainly distributed in the range of 2~20 nm, and the most probable pore size is 2.5 nm.

[0061] Figure 4 The nitrogen isothermal adsorption-desorption curve of the niobium pentoxide material obtained in Comparative Example 1 is shown below. Figure 4 It can be seen that the nitrogen isothermal adsorption-desorption curve of the niobium pentoxide material prepared in Comparative Example 1 shows that a porous structure cannot be formed without the addition of CTAB as a soft template, and the specific surface area of ​​the material is significantly reduced to 8.0 m². 2 / g.

[0062] Figure 5 Thermogravimetric analysis (TGA) curves of niobium pentoxide materials prepared in Example 1 and Comparative Example 1 are shown below. Figure 5 Thermogravimetric analysis results show that the high-capacity porous niobium pentoxide material prepared in Example 1 has a significant weight loss process in the range of 300~400 °C, corresponding to the oxidation loss process of carbon components, with a weight loss of about 5.4%. In contrast, the Comparative Example 1 without CTAB has almost no weight loss in this temperature range, indicating that the use of surfactants in Example 1 can incorporate carbon atoms into the material.

[0063] Figure 6 The electron paramagnetic resonance spectrum of the high-capacity porous niobium pentoxide material prepared in Example 1 is shown below. Figure 6 The electron paramagnetic resonance spectrum analysis results show that the high-capacity porous niobium pentoxide material prepared in Example 1 exhibits a characteristic signal belonging to oxygen vacancies at g=2.001, proving that oxygen vacancies have been formed in the material.

[0064] To verify the lithium-ion battery performance of the material, the niobium pentoxide material obtained in Example 1 and Comparative Example 1 was thoroughly ground with polyvinylidene fluoride (PVDF) and conductive carbon black (Super P) at a mass ratio of 8:1:1. After adding N-methylpyrrolidone (NMP) and continuing to grind and mix evenly, a black paste was obtained. The black paste was uniformly coated on copper foil, dried, and cut into electrode sheets with a diameter of 10 mm as the negative electrode of the lithium-ion battery. A lithium sheet was used as the counter electrode, a polypropylene (PP) film was used as the separator, 1M lithium hexafluorophosphate (LiPF6) was used as the solute, and a mixed solution of dimethyl carbonate (DMC): ethylene carbonate (EC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1 was used as the electrolyte. A CR2032 button battery was assembled in a glove box, and its electrochemical performance was tested after standing for 8 hours.

[0065] Figure 7 The image shows the cyclic voltammogram of a lithium-ion battery using niobium pentoxide material obtained in Example 1 as the negative electrode material. Figure 7 It can be seen that the high-capacity porous niobium pentoxide material prepared in Example 1 exhibits a significant reduction peak at around 0.73 V during the first cycle, corresponding to the formation of the irreversible solid electrolyte interphase (SEI) component. This component can stabilize the battery reaction interface during subsequent cycles. The latter two cycles overlap well, revealing the high reversibility of the lithium-ion storage process. Furthermore, the highly symmetrical set of redox peaks at 1.6 V / 2.1 V also indicates the high capacity of Nb. 5+ / Nb 4+ Excellent electrochemical reversibility.

[0066] Figure 8 The graph shows the rate performance of niobium pentoxide material obtained in Example 1 as the negative electrode of a lithium-ion battery; from Figure 8 It can be seen that the high-capacity porous niobium pentoxide material prepared in Example 1 has a first-cycle discharge capacity of up to 310.2 mAh / g at a current density of 0.1 A / g, which far exceeds the theoretical capacity of orthorhombic niobium pentoxide of 202 mAh / g. At the same time, the reversible discharge specific capacities at current densities of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 A / g are 294.5, 251.8, 212.5, 159.6, 95.5, and 12.1 mAh / g, respectively, indicating that the material has excellent rate performance.

[0067] Figure 9 The graph shows the rate performance of the niobium pentoxide material prepared in Comparative Example 1 as the negative electrode of a lithium-ion battery; from Figure 9It can be seen that the niobium pentoxide material prepared in Comparative Example 1 without the surfactant CTAB as a soft template has poor rate performance due to the lack of a porous structure, fewer electrochemical lithium storage active sites, and reversible discharge specific capacities of 220.5, 150.8, 96.5, 48.2, 3.5, and 1.4 mAh / g at current densities of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 A / g, respectively, which are far lower than the high-capacity porous niobium pentoxide material in Example 1.

[0068] Figure 10 The graph shows the cycling performance of the niobium pentoxide material prepared in Example 1 as a lithium-ion battery anode at a current density of 0.1 A / g. Figure 10 It can be seen that the high-capacity porous niobium pentoxide material 1 prepared in Example 1 maintained a specific capacity of ~347.6 mAh / g after 250 cycles at a current density of 0.1 A / g, indicating that it has excellent cycling stability under low rate conditions.

[0069] Figure 11 The graph shows the cycling performance of the niobium pentoxide material prepared in Example 1 as a lithium-ion battery anode at a current density of 1.0 A / g; according to Figure 11 It can be seen that the high-capacity porous niobium pentoxide material 1 prepared in Example 1 exhibited slow capacity decay in the early stage of charge-discharge cycling at a current density of 1 A / g, but after 3500 cycles, the specific capacity remained stable at ~100 mAh / g, indicating that it also has excellent cycling stability at high rates.

[0070] This invention proposes an electrostatic-coordination synergistic assembly technique to construct a niobium-based precursor with a unique "raspberry-like" multi-level morphology (10-30 nm niobium pentoxide nanoparticles anchored on the surface of 100-300 nm niobium pentoxide matrix particles) under the guidance of a soft template. Simultaneous porous structure construction and in-situ carbon doping are achieved through inert atmosphere sintering. The high-capacity porous niobium pentoxide material of this invention has a porous structure with mesopores of 2-20 nm, which is beneficial for enhancing electrolyte penetration and shortening ion diffusion paths, and the specific surface area provides abundant active sites. Through a dual structure-composition regulation strategy, this invention synergistically improves the low conductivity and slow ion diffusion barrier of T-Nb2O5, achieving a capacity exceeding its theoretical capacity of 202 mAh / g when applied to lithium-ion battery anodes, reaching 350 mAh / g at a current density of 0.1 A / g.

Claims

1. A method for preparing a high-capacity porous niobium pentoxide material, characterized in that, The method includes the following steps:

1. A surfactant containing an organic quaternary ammonium cation and an ethanol solution of triethanolamine are added to a mixed solvent of ethanol and water to obtain a mixture. The mixture is heated to 50-70 °C under stirring and maintained for 0.5-3.0 h to obtain a micelle solution. The concentration of the surfactant containing the organic quaternary ammonium cation is 0.01-0.06 g / mL, the concentration of triethanolamine in the ethanol solution is 0.35 g / mL, and the mass ratio of the surfactant containing the organic quaternary ammonium cation to the volume ratio of the ethanol solution of triethanolamine is 1 g: (0.25-1.5) mL.

2. Add niobium salt aqueous solution to micelle solution, stir at a constant speed at 50~90 ℃ for 4~12 h to carry out assembly reaction, and after centrifugation and freeze drying, obtain niobium oxygen precursor with organic quaternary ammonium cation complex.

3. The niobium oxide precursor is placed in a high-temperature furnace and sintered at 500-800 °C for 2-5 h under an inert gas atmosphere to obtain a high-capacity porous niobium pentoxide material. This material is composed of interconnected niobium pentoxide matrix nanoparticles with a size of 100-300 nm, and secondary niobium pentoxide nanoparticles with a size of 10-30 nm grow on its surface, exhibiting a unique "raspberry-like" hierarchical assembly morphology. It has mesoporous pores with a pore size of 2-20 nm and a specific surface area of ​​15-45 m². 2 / g; It has an orthorhombic niobium pentoxide structure and carbon doping characteristics.

2. The method for preparing a high-capacity porous niobium pentoxide material according to claim 1, characterized in that, The surfactant containing organic quaternary ammonium cation mentioned in step one is one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide and octadecyltrimethylammonium bromide.

3. A method for preparing a high-capacity porous niobium pentoxide material according to claim 1 or 2, characterized in that, In the mixed solvent of ethanol and water mentioned in step one, the volume ratio of alcohol to water is (2~5):

1.

4. A method for preparing a high-capacity porous niobium pentoxide material according to claim 1 or 2, characterized in that, The niobium salt mentioned in step two is niobium oxalate, and the concentration of the niobium salt aqueous solution is 0.04~0.10 mol / L.

5. A method for preparing a high-capacity porous niobium pentoxide material according to claim 1 or 2, characterized in that, The volume ratio of the niobium salt aqueous solution to the micelle solution in step two is 1:(1~5).

6. A method for preparing a high-capacity porous niobium pentoxide material according to claim 1 or 2, characterized in that, The inert gas mentioned in step three is one or more of nitrogen and argon, and the flow rate of the inert gas is 20~60 mL / min.

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