High-capacity porous niobium pentoxide material as well as preparation method and application thereof

Abstract

The invention discloses a high-capacity porous niobium pentoxide material as well as a preparation method and application thereof, relates to niobium pentoxide as well as preparation and application thereof, and aims to solve the technical problems of low conductivity and slow ion diffusion of the conventional orthorhombic phase niobium pentoxide material. The material is formed by interconnection of niobium pentoxide matrix nanoparticles of 100-300 nm, secondary nanoparticles of 10-30 nm grow on the surface, and the material is in a raspberry-shaped multistage assembly morphology; the catalyst has mesopores with the pore diameter of 2-20 nm and the specific surface area of 15-45 m < 2 > / g; and the material has an orthorhombic phase niobium pentoxide structure and a carbon doping characteristic. The preparation method comprises the following steps: by taking a surfactant containing quaternary ammonium cations as a soft template, driving niobium salt and organic quaternary ammonium cations to be assembled by utilizing an electrostatic-coordination synergistic effect, and sintering at high temperature in an inert atmosphere. When used as a negative electrode of a lithium ion battery, the lithium ion battery can reach the capacity of 350 mAh / g under the current density of 0.1 A / g, and can be used in the field of fast-charge alkali metal ion batteries.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy materials, and relates to a high-capacity porous niobium pentoxide material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of portable electronic products, hybrid / electric vehicles and balanced smart grid demand, the market demand for energy storage systems with high rate charge and discharge capacity is increasing day by day. Lithium ion batteries have become the core carrier of new energy systems due to their high energy density, long cycle life and environmental friendly characteristics, but the fast charging safety hazard (lithium dendrite generation) of commercial graphite negative electrode and the low theoretical capacity (175 mAh / g) of lithium titanate (LTO) negative electrode restrict its application in high power scenarios. Orthorhombic niobium pentoxide (T-Nb2O5) is considered as an ideal high-power negative electrode candidate material due to its intrinsic safety brought by high working potential (~1.6 V vs. Li + / Li), low volume strain (<4%) stability of Wadsley-Roth layered open framework, and fast ion intercalation / deintercalation mechanism dominated by pseudo-capacitance. However, the development of T-Nb2O5 negative electrode material faces two core bottlenecks: one is the extremely low intrinsic conductivity (~3×10 -6 S / cm) leading to severe polarization at high rate, and the other is the slow ion diffusion kinetics (Li + diffusion coefficient is only ~10 -12 cm 2 / s, which is 4 orders of magnitude lower than that of graphite).

[0003] To break through the above limitations, the existing technology mainly adopts three strategies of carbon composite, element doping and nanocrystallization. Although these strategies have made great progress in the research of T-Nb2O5 negative electrode material, it is still difficult to simultaneously solve the problems of low conductivity and slow ion diffusion, and there are significant compromises in process complexity, structural stability or economy. SUMMARY

[0004] The present application is to solve the technical problems of low conductivity and slow ion diffusion of the existing T-Nb2O5 negative electrode material, and to provide a high-capacity porous niobium pentoxide material and a preparation method and application thereof. The present application improves the low conductivity and slow ion diffusion of the existing orthorhombic niobium pentoxide negative electrode material through a structure-component dual regulation strategy, and obtains a breakthrough in the lithium storage capacity.

[0005] The high-capacity porous niobium pentoxide material of the present application is interconnected by niobium pentoxide matrix nanoparticles with a size of 100-300 nm, and has secondary niobium pentoxide nanoparticle with a size of 10-30 nm grown on the surface, showing a unique "raspberry-like" multi-level assembly morphology; has mesoporous pores with a pore size of 2-20 nm, a specific surface area of 15-45 m 2 / g; has a niobium pentoxide structure of orthorhombic phase and a carbon doping feature.

[0006] The preparation method of the high-capacity porous niobium pentoxide material described above comprises the following steps:

[0007] I. A surfactant containing organic quaternary ammonium cations and an ethanol solution of triethanolamine are added to a mixed solvent of ethanol and water to obtain a mixed solution; the mixed solution is heated to 50-70 ℃ under stirring for 0.5-3.0 h for reaction to obtain a micellar solution;

[0008] II. A niobium salt aqueous solution is added to the micellar solution, and an assembly reaction is carried out under uniform stirring at a temperature of 50-90 ℃ for 4-12 h; after centrifugal separation and freeze-drying, an organic quaternary ammonium cation-complexed niobium-oxygen precursor is obtained;

[0009] III. The niobium-oxygen precursor is placed in a high-temperature furnace, and is heated to 500-800 ℃ under an inert gas atmosphere for 2-5 h for high-temperature sintering to obtain the high-capacity porous niobium pentoxide material.

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

[0011] Preferably, the concentration of the surfactant containing organic quaternary ammonium cations in step I is 0.01-0.06 g / mL. The surfactant containing organic quaternary ammonium cations has a structure-component dual regulation effect in the synthesis process of the niobium pentoxide material: first, as a micellar soft template, it guides the hydrolysis and assembly of the niobium salt through electrostatic-coordination synergistic effect, so as to form a porous structure in the niobium-oxygen precursor nanosphere; second, as a carbon source, it is in-situ doped into the niobium pentoxide crystal lattice structure in the high-temperature sintering process. The addition amount of the surfactant directly affects the pore structure of the niobium-oxygen precursor, and the pore structure directly affects the distribution state of the doped carbon source on the pore surface. When the addition amount is too large, the pore structure of the niobium-oxygen precursor is destroyed, and the doped carbon source is distributed on the surface of the pore structure; when the addition amount is too small, the doped carbon source is not enough. SmallWhen the amount of the surfactant is too large, the niobium-oxygen precursor is seriously agglomerated due to the excessive electrostatic-coordination force, which is not conducive to the formation of the raspberry-like multi-level assembly morphology, and changes the shape of the pores of the material, and the excessive surfactant also increases the difficulty of purification and separation.

[0012] Preferably, the concentration of the triethanolamine in the triethanolamine ethanol solution in step one is 0.35 g / mL, and the mass of the surfactant containing the organic quaternary ammonium cation to the volume of the triethanolamine ethanol solution is 1 g:(0.25-1.5) mL. The triethanolamine acts as a catalyst in the synthesis reaction of the niobium-oxygen precursor, and can control the hydrolysis of the niobium oxalate and the nucleation rate of the nanoparticles, so as to control the size and uniformity of the matrix particles and the secondary nanoparticles of the niobium-oxygen precursor. When the amount of the triethanolamine is too small, the reaction rate is too slow, and the size of the generated niobium-oxygen precursor particles is too small; when the amount of the triethanolamine is too large, it is not conducive to controlling the reaction rate, which leads to the rapid growth of the niobium-oxygen precursor nanoparticles, and finally the size of the particles is too large and the uniformity is poor.

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

[0014] Preferably, the niobium salt in step two is niobium oxalate, and the concentration of the aqueous solution of the niobium salt is 0.04-0.10 mol / L. The niobium oxalate is the only niobium source, and when the concentration of the aqueous solution of the niobium oxalate is too small, the yield of the niobium-oxygen precursor is low due to the lack of the niobium source, and the complete matrix particles cannot be formed; when the concentration of the aqueous solution of the niobium oxalate is too large, the collision opportunities between the niobium source molecules increase, more nucleation and growth points are generated, and the particle size of the formed niobium-oxygen precursor is too small.

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

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

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

[0018] The application of the high-capacity porous niobium pentoxide material is to use it as a negative electrode in a lithium ion battery.

[0019] Compared with the prior art, the application has the following advantages:

[0020] The high-capacity porous niobium pentoxide material provided by the application is interconnected by matrix nanoparticles with a size of 100-300 nm, and a plurality of secondary nano-particles with a size of 10-30 nm are grown on the surface of the matrix nanoparticles, and the material presents a unique "raspberry-like" multi-level assembly morphology; on the other hand, the material has a rich porous structure and a high specific surface area, the pore size is mainly distributed in the range of 2-20 nm, and the material has an orthorhombic niobium pentoxide structure and a carbon doping feature; the structure-component dual regulation promotes the full contact and penetration of the electrolyte with the material, and at the same time, provides a large number of electrochemical active sites, thereby significantly improving the low conductivity and slow ion diffusion defects of the orthorhombic niobium pentoxide negative electrode material in the prior art.

[0021] The preparation method of the application uses a surfactant containing an organic quaternary ammonium cation as a soft template for guidance, and uses electrostatic-coordination synergistic action to drive the assembly of a niobium salt precursor and the organic quaternary ammonium cation to form an organic-inorganic composite, and the porous orthorhombic niobium pentoxide material with a unique "raspberry-like" multi-level morphology can be constructed by high-temperature sintering in an inert atmosphere, and in-situ carbon doping modification is realized at the same time. The method is simple and efficient, and by adjusting the process parameters, the particle size and pore size distribution of the material can be flexibly controlled, and the method has good repeatability and potential for large-scale production. On the other hand, the precursor is sintered at high temperature in an inert gas, so that the niobium oxide precursor is not fully oxidized, and an orthorhombic niobium pentoxide (T-Nb2O 5-x ), which has partial oxygen vacancies, is formed, thereby improving the intrinsic conductivity.

[0022] When the high-capacity porous niobium pentoxide material provided by the application is applied to the negative electrode of a lithium ion battery, the lithium storage capacity breaks through the theoretical value and reaches 350 mAh / g at a current density of 0.1 A / g, and the material has excellent rate performance and cycle stability. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Scanning electron microscope images of the niobium pentoxide materials prepared for 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 X-ray diffraction patterns of the niobium pentoxide materials prepared for Examples 1-5 and Comparative Example 1;

[0025] Figure 3 Nitrogen isothermal adsorption-desorption curve diagram of the niobium pentoxide material prepared for Example 1: a) and corresponding pore size distribution curve diagram: b);

[0026] Figure 4 Nitrogen isothermal adsorption-desorption curve diagram of the niobium pentoxide material prepared for Comparative Example 1;

[0027] Figure 5 Thermogravimetric analysis curve of the niobium pentoxide material prepared for Example 1 and Comparative Example 1;

[0028] Figure 6 Electron paramagnetic resonance spectrum of the niobium pentoxide material prepared for Example 1;

[0029] Figure 7 Cyclic voltammogram of the niobium pentoxide material prepared for Example 1 as an anode of a lithium ion battery at a scan rate of 0.2 mV / s;

[0030] Figure 8 Rate performance of the niobium pentoxide material prepared for Example 1 as an anode of a lithium ion battery;

[0031] Figure 9 Rate performance of the niobium pentoxide material prepared for Comparative Example 1 as an anode of a lithium ion battery;

[0032] Figure 10 Cycle performance of the niobium pentoxide material prepared for Example 1 as an anode of a lithium ion battery at a current density of 0.1 A / g;

[0033] Figure 11 Cycle performance of the niobium pentoxide material prepared for Example 1 as an anode of a lithium ion battery at a current density of 1.0 A / g. DETAILED DESCRIPTION

[0034] The technical method of the present application will be further described below in combination with specific embodiments.

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

[0036] I. 1.0 g of cetyltrimethylammonium bromide (CTAB) and 0.75 mL of a triethanolamine (TEA) ethanol solution with a concentration of 0.35 g / mL were added to 50 mL of a mixed solvent with a volume ratio of ethanol to water of 4:1 to obtain a mixed solution; the mixed solution was heated to 60 °C under stirring for 0.5 h for reaction to obtain a micellar solution;

[0037] II. 20 mL of a niobium oxalate aqueous solution with a concentration of 0.08 M was added to the micellar solution, and an assembly reaction was carried out under uniform stirring at a temperature of 80 °C for 8 h; after centrifugal separation and freeze-drying, a niobium-oxygen precursor complexed with organic quaternary ammonium cations was obtained;

[0038] III. The niobium oxide precursor was placed in a corundum boat, which was then placed in a tube furnace. Nitrogen was continuously introduced at a flow rate of 50 mL / min, while the temperature was raised to 300 °C at a rate of 2 °C / min, then to 700 °C at a rate of 10 °C / min and maintained for 2 h for high-temperature sintering. After cooling to room temperature, a high-capacity porous niobium pentoxide material was obtained.

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

[0040] I. 1.0 g of CTAB and 0.75 mL of a triethanolamine ethanol solution with a concentration of 0.35 g / mL were added to 50 mL of a mixed solvent with a volume ratio of ethanol / water of 4:1 to obtain a mixed solution. The mixed solution was heated to 60 °C under stirring for 0.5 h for reaction to obtain a micellar solution;

[0041] II. 20 mL of a niobium oxalate aqueous solution with a concentration of 0.06 M was added to the micellar solution, and the assembly reaction was carried out under uniform stirring at a temperature of 80 °C for 8 h. After centrifugal separation and freeze-drying, a niobium oxide precursor complexed with organic quaternary ammonium cations was obtained;

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

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

[0044] I. 1 g of CTAB and 0.75 mL of a triethanolamine ethanol solution with a concentration of 0.35 g / mL were added to 50 mL of a mixed solvent with a volume ratio of ethanol / water of 4:1 to obtain a mixed solution. The mixed solution was heated to 60 °C under stirring for 0.5 h for reaction to obtain a micellar solution;

[0045] II. 20 mL of a niobium oxalate aqueous solution with a concentration of 0.1 M was added to the micellar solution, and the assembly reaction was carried out under uniform stirring at a temperature of 80 °C for 8 h. After centrifugal separation and freeze-drying, a niobium oxide precursor complexed with organic quaternary ammonium cations was obtained;

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

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

[0048] I. 0.5 g of CTAB and 0.75 mL of an ethanol solution of TEA with a concentration of 0.35 g / mL were added to 50 mL of a mixed solvent with a volume ratio of ethanol / water of 4:1 to obtain a mixed solution. The mixed solution was heated to 60 ℃ under stirring for 0.5 h for reaction to obtain a micellar solution;

[0049] II. 20 mL of an aqueous solution of niobium oxalate with a concentration of 0.08 M was added to the micellar solution. The assembly reaction was carried out under uniform stirring at a temperature of 80 ℃ for 8 h. After centrifugal separation and freeze-drying, an organic quaternary ammonium cation complexed niobium oxide precursor was obtained;

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

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

[0052] I. 3 g of CTAB and 0.75 mL of an ethanol solution of triethanolamine with a concentration of 0.35 g / mL were added to 50 mL of a mixed solvent with a volume ratio of ethanol / water of 4:1 to obtain a mixed solution. The mixed solution was heated to 60 ℃ under stirring for 0.5 h for reaction to obtain a micellar solution;

[0053] II. 20 mL of an aqueous solution of niobium oxalate with a concentration of 0.08 M was added to the micellar solution. The assembly reaction was carried out under uniform stirring at a temperature of 80 ℃ for 8 h. After centrifugal separation and freeze-drying, an organic quaternary ammonium cation complexed niobium oxide precursor was obtained;

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

[0055] Comparative Example 1: This comparative example is to prepare a niobium pentoxide material without surfactant, and the specific steps are as follows:

[0056] I. 0.75 mL of triethanolamine ethanol solution with a concentration of 0.35 g / mL was added to 50 mL of mixed solvent with a volume ratio of ethanol / water of 4:1 to obtain a mixed solution. The mixed solution was heated to 60 °C and stirred for 0.5 h, then 20 mL of niobium oxalate aqueous solution with a concentration of 0.08 M was added, and the stirring was continued at a temperature of 80 °C for 8 h. Deionized water was added for centrifugal separation, and freeze-drying was performed to obtain a niobium oxide precursor material.

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

[0058] Figure 1 The scanning electron microscope photos of the niobium pentoxide materials obtained in Examples 1-5 and Comparative Example 1 are shown in Figure 1. Figure 1 As can be seen from the results, 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, and a large number of secondary nano-particles with a size of 10-30 nm were anchored on the surface, presenting a "raspberry-like" multi-level nano-assembly structure as a whole. The irregular matrix particles were connected to each other, but the boundaries between the particles were distinct, and there was no obvious agglomeration phenomenon, which was helpful for the penetration of electrolyte and the transmission of lithium ions. In the materials of Examples 1-5, as the concentration of niobium source or CTAB increased, the niobium oxide precursor gradually agglomerated and adhered to form larger and more irregular matrix particles.

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

[0060] Figure 3 The nitrogen isothermal adsorption-desorption curve of the niobium pentoxide material obtained in Example 1 is shown in Figure 2. 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 isothermal curve, indicating that there are a large number of mesoporous structures in the material, and the adsorption-desorption characteristics at low pressure also indicate that there is a certain amount of micropore. The specific surface area of the niobium pentoxide material of Example 1 is 43.1 m 2 / g, and from the corresponding pore size distribution curve, it can be seen that the pore size is mainly distributed in 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 in Figure 3. 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 without adding CTAB as a soft template, no pore structure can be formed, and the specific surface area of the material is significantly reduced to 8.0 m 2 / g.

[0062] Figure 5 The thermogravimetric analysis curve of the niobium pentoxide materials prepared in Example 1 and Comparative Example 1 is shown in Figure 4. Figure 5 The thermogravimetric analysis results show that the high-capacity porous niobium pentoxide material prepared in Example 1 has a significant weight loss process in the temperature range of 300-400 ℃, corresponding to the oxidation loss process of carbon components, and the weight loss is about 5.4%, while Comparative Example 1 without CTAB has almost no weight loss in this temperature range, indicating that the use of surfactant 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 in Figure 5. Figure 6 The electron paramagnetic resonance spectrum analysis results show that the high-capacity porous niobium pentoxide material prepared in Example 1 has a characteristic signal at g=2.001 belonging to oxygen vacancies, proving that oxygen vacancies are 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 respectively fully ground with polyvinylidene fluoride (PVDF) and conductive carbon black (Super P) at a mass ratio of 8:1:1, N-methyl pyrrolidone (NMP) was added and continuously ground to mix uniformly, to obtain a black paste slurry, the black slurry was uniformly coated on a copper foil, dried and cut into an electrode sheet with a diameter of 10 mm as a negative electrode of a lithium ion battery, a lithium sheet was used as a counter electrode, a polypropylene (PP) film was used as a separator, 1M lithium hexafluorophosphate (LiPF6) was used as a solute, a mixed solution of dimethyl carbonate (DMC): ethylene carbonate (EC): methyl ethyl carbonate (EMC) at a volume ratio of 1:1:1 was used as an electrolyte, and a CR2032 type button cell was assembled in a glove box, and after standing for 8h, the electrochemical performance was tested.

[0065] Figure 7 The cyclic voltammogram of the lithium ion battery with the niobium pentoxide material obtained in Example 1 as the negative electrode material is shown in Figure 2. Figure 7 It can be seen that the high-capacity porous niobium pentoxide material prepared in Example 1 has a first cycle at about 0.73 V, with a clear reduction peak, corresponding to the formation of an irreversible solid electrolyte interface phase SEI component, which can stabilize the battery reaction interface in the subsequent cycle process. The last two cycles can be well overlapped, revealing the high reversibility of the lithium ion storage process. In addition, a set of high-symmetry redox peaks at 1.6 V / 2.1 V also indicate that the Nb 5+ / Nb 4+ excellent electrochemical reaction reversibility.

[0066] Figure 8 The rate performance graph of the lithium ion battery with the niobium pentoxide material obtained in Example 1 as the negative electrode is shown in Figure 3. 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 310.2 mAh / g at a current density of 0.1 A / g, far exceeding the theoretical capacity of 202 mAh / g of the orthorhombic niobium pentoxide, and the reversible discharge specific capacity at current densities of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0 A / g is 294.5, 251.8, 212.5, 159.6, 95.5, 12.1 mAh / g, respectively, indicating that the material has excellent rate performance.

[0067] Figure 9 The rate performance graph of the lithium ion battery with the niobium pentoxide material prepared in Comparative Example 1 as the negative electrode is shown in Figure 4. Figure 9It can be seen that the niobium pentoxide material prepared in Comparative Example 1 without the soft template of the surfactant CTAB does not form a porous structure, has few electrochemical lithium storage active sites, and has poor rate performance, and the reversible discharge specific capacity at a current density of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 A / g is 220.5, 150.8, 96.5, 48.2, 3.5, and 1.4 mAh / g, respectively, which is much lower than the high-capacity porous niobium pentoxide material of Example 1.

[0068] Figure 10 The cycle performance graph of the niobium pentoxide material prepared in Example 1 as a negative electrode of a lithium ion battery at a current density of 0.1 A / g is shown in Figure 2, and according to Figure 10 It can be seen that the high-capacity porous niobium pentoxide material 1 prepared in Example 1 has a stable specific capacity of about 347.6 mAh / g at a current density of 0.1 A / g after 250 cycles, indicating excellent cycle stability at a low rate.

[0069] Figure 11 The cycle performance graph 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 is shown in Figure 3, and according to Figure 11 It can be seen that the high-capacity porous niobium pentoxide material 1 prepared in Example 1 has a stable specific capacity of about 100 mAh / g at a current density of 1 A / g after 3500 cycles, indicating excellent cycle stability at a high rate.

[0070] The present application proposes to construct a niobium-based precursor with a unique "raspberry-like" multi-level morphology (100-300 nm niobium pentoxide base particles anchoring 10-30 nm niobium pentoxide nanoparticles) on the surface of the soft template by electrostatic-coordination synergistic assembly technology, and to realize the construction of a porous structure and in-situ carbon doping simultaneously by sintering in an inert atmosphere. The high-capacity porous niobium pentoxide material of the present application has a porous structure and is a mesoporous structure with a pore size of 2-20 nm, which is beneficial to enhancing the electrolyte penetration and shortening the ion diffusion path, and the specific surface area provides abundant active sites. The present application improves the low conductivity and slow ion diffusion barrier of T-Nb2O5 by a structure-component dual regulation strategy, and when applied to a lithium ion battery negative electrode, breaks through the theoretical capacity of 202 mAh / g, and reaches a capacity of 350 mAh / g at a current density of 0.1 A / g.

Claims

1. A high capacity, porous niobium pentoxide material, characterized in that The material is interconnected by 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 the surface, presenting a unique "raspberry-like" multi-level assembly morphology; having mesoporous pores with a pore size of 2-20 nm, a specific surface area of 15-45 m 2 / g; having an orthorhombic niobium pentoxide structure and carbon doping characteristics.

2. A method of preparing a high capacity porous niobium pentoxide material, characterized in that, The method comprises the following steps: I. adding a surfactant containing organic quaternary ammonium cations and an ethanol solution of triethanolamine into a mixed solvent of ethanol and water to obtain a mixed solution; heating the mixed solution to 50-70 DEG C under stirring for 0.5-3.0 h to perform a reaction, and obtaining a micellar solution; II. adding a niobium salt aqueous solution into the micellar solution, performing an assembly reaction under uniform stirring at a temperature of 50-90 DEG C for 4-12 h, and obtaining a niobium oxide precursor complexed with organic quaternary ammonium cations after centrifugal separation and freeze-drying; III. placing the niobium oxide precursor into a high-temperature furnace, heating to 500-800 DEG C under an inert gas atmosphere for 2-5 h to perform high-temperature sintering, and obtaining a high-capacity porous niobium pentoxide material.

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

4. The method of claim 2 or 3, wherein the high capacity porous niobium pentoxide material is prepared by the steps of: The concentration of the surfactant containing organic quaternary ammonium cations in step I is 0.01-0.06 g / mL.

5. A method for preparing a high-capacity porous niobium pentoxide material according to claim 2 or 3, characterized in that, The concentration of triethanolamine in the ethanol solution of triethanolamine in step I is 0.35 g / mL, and the mass of the surfactant containing organic quaternary ammonium cations to the volume of the ethanol solution of triethanolamine is 1 g:(0.25-1.5) mL.

6. The method of claim 2 or 3, wherein the high capacity porous niobium pentoxide material is prepared by the steps of: In the mixed solvent of ethanol and water in step I, the volume ratio of alcohol to water is (2-5):

1.

7. The method of claim 2 or 3, wherein the high capacity porous niobium pentoxide material is prepared by the steps of: The niobium salt in step II is niobium oxalate, and the concentration of the niobium salt aqueous solution is 0.04-0.10 mol / L.

8. A method for preparing a high-capacity porous niobium pentoxide material according to claim 2 or 3, characterized in that, The volume ratio of the niobium salt aqueous solution to the micellar solution in step II is 1:(1-5).

9. The method of claim 2 or 3, wherein the high capacity porous niobium pentoxide material is prepared by the steps of: The inert gas in step III is one or more of nitrogen and argon, and the flow rate of the inert gas is 20-60 mL / min.

10. Use of a high-surface-area porous niobium pentoxide material according to claim 1, characterized in that, The application is to use the high-capacity porous niobium pentoxide material as a negative electrode in a lithium ion battery.

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