High-entropy doped niobium pentoxide nano-particles as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion battery materials and electrochemistry, and discloses high-entropy doped niobium pentoxide nanoparticles as well as a preparation method and application thereof. The chemical formula of the nano-particles is Nb < 1-x > FeaCoeNiiCrjAlkO2, x = a + e + i + j + k, and x is larger than or equal to 0.04 and smaller than or equal to 0.06, 0 lt; a < lt >; 1, 0lt; lt, lt; 1, 0lt; ilt; 1, 0lt; jlt; 1, 0lt; klt; 1; the material has an orthorhombic system and a space group P2 / m, doped metal occupies Nb sites in an atomic-scale dispersion manner, and a unit cell parameter c axis is expanded to 0.41 nm; and the size of the nano particles is 50 to 200 nm. According to the preparation method, a hydrothermal method is combined with high-temperature sintering, niobium pentachloride is used as a niobium source, specific metal salt is used as a doping source, terephthalic acid is used as a ligand, and the material is prepared through the steps of solution preparation, hydrothermal reaction, drying and sintering. The nano-particles are high in electron conductivity and fast in lithium ion diffusion, the capacity reaches 156 mAh. G <-1 > under the rate of 100 C, the capacity retention rate is 88% or above after 1000 times of circulation under the rate of 10 C, and the nano-particles can be used as an excellent lithium ion battery negative electrode material and are suitable for the field of high-power lithium ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials and electrochemical technology, specifically relating to a high-entropy doped niobium pentoxide nanoparticle, its preparation method, and its application. Background Technology

[0002] High-power lithium-ion batteries (fast charge / discharge) are increasingly in demand in fields such as high-speed drones, consumer electronics, new energy vehicles, and military equipment. Although traditional graphite anode lithium-ion batteries perform well in most scenarios, their slow electrochemical kinetics, poor rate performance, and safety hazards caused by lithium dendrites at the interface make them unsuitable for the demands of high-power, high-safety lithium-ion batteries. Therefore, Li4Ti5O4 batteries with a working potential range of 1-2 V (vs. Li+ / Li) are being developed. 12 Lithium has attracted much attention due to its ability to effectively avoid the risk of dendrite formation, but its 175 mAh g⁻¹... -1 Its low theoretical capacity limits its large-scale application.

[0003] In recent years, products with high specific capacity (>200 mAh g) have been developed. -1 Niobium-based oxides (such as T-Nb₂O₅ and TiNb₂O₇) have become a research hotspot. Among them, orthorhombic T-Nb₂O₅ exhibits exceptionally fast energy storage characteristics, with its lithium-ion intercalation rate increasing almost linearly with the scan rate, and has been applied in various energy storage device research. The crystal structure of T-Nb₂O₅ is exceptionally complex, consisting of an open framework structure formed by tilted NbO₆ octahedra and NbO₇ pentagonal bipyramidal structures, providing quasi-two-dimensional continuous channels for ion transport, enabling the material to achieve high-rate performance. However, the practical application of T-Nb₂O₅ still faces key challenges. First, its intrinsic electronic conductivity is low, leading to significant polarization effects at high rates, severely limiting the improvement of power density. Second, its limited bulk diffusion channels and energy storage sites prevent its capacity from reaching the level of graphite. Although carbon composites have increased the conductivity by several orders of magnitude, alleviating the electron transport limitation, they cannot overcome the bottleneck of bulk ion diffusion kinetics. The applicant's previous research showed that doping Co into T-Nb2O5 improved the electronic conductivity of T-Nb2O5 and excited Nb. 4+ / Nb 3+ The redox reaction improves the rate performance and specific capacity of the material. However, the results show that when the doping concentration is greater than 2%, impurity phases appear in T-Nb2O5, making it difficult to maintain the quasi-two-dimensional lithium-ion migration channels of Nb2O5. The high-entropy (HE) strategy, as a special doping method, can construct a stable host crystal structure by introducing multiple elements to increase the entropy value, showing significant effectiveness in enhancing the stability of layered cathode oxides and improving the conductivity of solid electrolytes. This provides a new approach for achieving high-concentration doped T-Nb2O5. Summary of the Invention

[0004] Aiming at the defects of low electronic conductivity and insufficient energy storage sites in existing fast-charging niobium-based oxide anode materials, the present invention provides a high-entropy doped niobium pentoxide nanoparticle, its preparation method and application, so as to achieve the precise occupation of Nb sites by doped atoms without causing phase separation, and at the same time improve the electronic conductivity, lithium ion diffusion rate and specific capacity of the material, and solve the core contradiction that the fast-charging performance and capacity of traditional niobium-based materials cannot be兼得.

[0005] To achieve the above object, the present invention provides a high-entropy doped niobium pentoxide nanoparticle, and the chemical formula of the high-entropy doped niobium pentoxide nanoparticle is Nb 1-x Fe a Co e Ni i Cr j Al k O2, where x = a + e + i + j + k, 0.04 ≤ x ≤ 0.06, 0 < a < 1, 0 < e < 1, 0 < i < 1, 0 < j < 1, 0 < k < 1; it has an orthorhombic crystal system, space group P2 / m, the doped metals occupy the Nb sites in an atomic-level dispersion, and the c-axis of the unit cell parameter extends to 0.41 nm; the nanoparticle size is 50-200 nm. Further, the discharge capacity of the nanoparticle at a rate of 100 C is not less than 156 mAh g -1 , and the lithium ion diffusion coefficient is 10 -8 -10 -10 cm 2 / s.

[0006] Further, the value of x is 0.05; The present invention also provides a preparation method of the above-mentioned high-entropy doped niobium pentoxide nanoparticle, including the following steps: (1) Dissolve niobium source, iron source, cobalt source, nickel source, chromium source and aluminum source in N,N-dimethylformamide or ethanol to form a metal mixed solution A; (2) Dissolve the organic ligand in N,N-dimethylformamide or ethanol to form a ligand solution B; (3) Mix solution A and solution B evenly to obtain a precursor solution; (4) Place the precursor solution in a hydrothermal reaction kettle, react at 160-220 °C for 6-24 hours, and after the reaction is completed, centrifuge, wash and dry to obtain a precursor; (5) Sinter the precursor under a protective atmosphere to obtain the high-entropy doped niobium pentoxide nanoparticle.

[0007] Furthermore, the niobium source is niobium pentachloride; the iron source is ferric chloride or ferric nitrate; the cobalt source is cobalt chloride or cobalt nitrate; the nickel source is nickel chloride or nickel nitrate; the chromium source is chromium chloride or chromium nitrate; and the aluminum source is aluminum chloride or aluminum nitrate.

[0008] Furthermore, the organic ligand is terephthalic acid; and the molar ratio of the organic ligand to the niobium source is (2-5):1.

[0009] Further, in step (1), the molar volume ratio of the niobium source to N,N-dimethylformamide or ethanol is 1 mmol : (15-23) mL; in step (2), the molar volume ratio of the organic ligand to N,N-dimethylformamide or ethanol is 1 mmol : (1-1.6) mL.

[0010] Furthermore, in step (5), the sintering is carried out by heating to 700-800°C at a heating rate of 2-5°C / min, holding at that temperature for 3-6 hours, and then cooling to room temperature.

[0011] The present invention also provides a lithium-ion battery anode material comprising the above-mentioned high-entropy doped niobium pentoxide nanoparticles.

[0012] The present invention also provides a lithium-ion battery, wherein the negative electrode adopts the above-mentioned lithium-ion battery negative electrode material; the battery retains a capacity of not less than 88% after 1000 cycles at a 10 C rate, and the volume change rate is less than 1.5%.

[0013] The beneficial effects of this invention are: 1) The innovative preparation process of this invention achieves atomic-level precise doping: through pentavalent niobium ions (Nb... 5+ ) and ferric ions (Fe 3+ ), trivalent aluminum ions (Al) 3+ ), divalent cobalt ions (Co) 2+ ), divalent nickel ions (Ni 2+ ), trivalent chromium ions (Cr 3 + Under the synergistic coordination regulated by terephthalic acid ligands, a precursor solution with uniform metal ion distribution was formed. HE-Nb₂O₅ nanoparticles (50-200 nm) obtained after heat treatment exhibit the following characteristics: 1) Multiple dopant ions occupy Nb lattice sites at the atomic level, forming a stable solid solution structure (no impurity phase peaks in XRD); 2) The high entropy effect causes Li₂O₅ to undergo a process where... + The diffusion channels are expanded (the interplanar spacing increases by 5%); 3) Through the synergistic effect of multi-metal electrons, the electronic conductivity is improved, achieving a high specific capacity of 280 mAh / g and a capacity retention of 88% at 10 C rate.

[0014] 2) The invention innovatively develops an orthorhombic high-entropy doped Nb2O5 material, and realizes performance breakthrough through the synergistic effect of multiple metal ions. In terms of electronic structure regulation, the co-doping of five transition metals (Fe, Co, Ni, Cr and Al) significantly changes the local electronic environment of Nb, and synchronously activates Nb 5+ / Nb 4+ / Nb 3+ Multi-electron redox reaction, the theoretical capacity is increased by more than 40% (from 202 mAh / g to 280 mAh / g); in terms of ion transmission kinetics, the high-entropy induced lattice distortion reduces the lithium ion migration energy barrier from 0.78 eV to 0.52 eV, Li + Diffusion coefficient compared with undoped sample; the unique solid solution structure still maintains 92.3% capacity retention rate after 1000 cycles at 10 C high rate, and the volume change rate is less than 1.5%. These characteristics make it an ideal negative electrode material for the new generation of fast-charging lithium ion batteries, especially suitable for electric vehicle fast-charging systems and high-power energy storage equipment.

[0015] 3) The preparation process of the invention has significant industrialization advantages, adopts one-step hydrothermal method combined with controllable sintering process, and has low energy consumption; no toxic solvent is involved in the whole process, which meets the twelve principles of green chemistry; by adjusting the ligand / metal ratio and solvothermal temperature, the product morphology can be accurately controlled, and the batch stability is better than that of sol-gel method, which has large-scale production conditions. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a) XRD, b) enlarged XRD diagram of HE-Nb2O5 nanoparticles prepared in Example 1; Figure 2 is a) TEM, b) and c) atomic HAADF-STEM images of HE-Nb2O5 nanoparticles prepared in Example 1; e) TEM, f) and g) atomic HAADF-STEM images of undoped niobium pentoxide (Nb2O5) nanoparticles; Figure 3 is atomic HAADF-STEM and EDS mapping images of HE-Nb2O5 and Nb2O5 nanoparticles prepared in Example 1; Figure 4 is a) UV-Vis diffuse reflectance spectrum of HE-Nb2O5 and Nb2O5 nanoparticles prepared in Example 1; b) photon energy and (ahv) 2 Relationship curve; Figure 5 is the CV curve of the material prepared in Example 1 as an electrode material in a lithium ion half-cell; Figure 6is a rate capability plot of the material prepared in Example 1 as an electrode material in lithium ion half-cells at different current densities; Figure 7 is a long cycle performance plot of the material prepared in Example 1 as an electrode material in lithium ion half-cells at 10 C current density; Figure 8 is a lithium ion diffusion coefficient of the material prepared in Example 1 as an electrode material in lithium ion half-cells; Figure 9 is an XPS spectrum of the material prepared in Example 1 as an electrode material in lithium ion half-cells under different charge-discharge conditions. DETAILED DESCRIPTION

[0017] In order to make the technical solutions and advantages of the present application clearer, the following will further describe the present application and its beneficial effects in detail with specific embodiments and the accompanying drawings of the specification, but the embodiments of the present application are not limited thereto. In order to facilitate the understanding of the present application, the following will describe the present application more fully and in detail with the accompanying drawings of the specification and the preferred embodiments, but the protection scope of the present application is not limited to the following specific embodiments.

[0018] Unless otherwise defined, all the professional terms used in the following have the same meaning as that generally understood by the person skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific embodiments and are not intended to limit the protection scope of the present application.

[0019] Unless otherwise specified, the various reagents and raw materials used in the present application are commercially available products or products that can be prepared by known methods.

[0020] In order to better understand the present application, the following will further illustrate the content of the present application with embodiments, but the content of the present application is not limited to the following embodiments.

[0021] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or similar expressions means any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0022] Example 1 A preparation method of HE-Nb2O5 nanoparticles, comprising the following steps: 1) Dissolve 1.9 mmol of niobium pentachloride, 0.02 mmol of aluminum nitrate nonahydrate, 0.02 mmol of cobalt nitrate nonahydrate, 0.02 mmol of chromium nitrate nonahydrate, 0.02 mmol of iron nitrate nonahydrate and 0.02 mmol of nickel nitrate hexahydrate in 35 mL of ethanol, mix well to obtain mixed solution A; 2) Dissolve 5 mmol of terephthalic acid in 35 mL of ethanol to obtain mixed solution B; 3) Mix mixed solution A and mixed solution B well to prepare a colorless transparent precursor solution; 4) Transfer the precursor solution to a 70 mL polytetrafluoroethylene lined hydrothermal reactor, place it in a 200°C oven for 12 h, and then naturally cool to room temperature. Centrifugal collection of the precipitate, washed with anhydrous ethanol 3 times, 70°C vacuum drying for 12 h, to obtain precursor powder.

[0023] 5) Place the precursor in a muffle furnace, heat to 750°C at a rate of 5°C / min, hold for 3 h, then cool to room temperature to obtain HE-Nb2O5 nanoparticles.

[0024] Figure 1 Fig. 1 is a) XRD and b) enlarged XRD of HE-Nb2O5 and pure Nb2O5 nanoparticles prepared in this example; the XRD pattern shows that the phase of high-entropy doped niobium pentoxide nanoparticles is Nb2O5, the diffraction peak corresponds to the standard card of orthorhombic Nb2O5, and there is no other impurity phase; the enlarged XRD pattern shows that the (001) diffraction peak of high-entropy doped niobium pentoxide shifts to low angle (Δ2θ = 0.15°), indicating that high-entropy doping expands the interlayer spacing (d value increases by 0.2 Å).

[0025] Figure 2 Fig. 2 is a) TEM and b) atomic level HAADF-STEM images of HE-Nb2O5 and pure Nb2O5 nanoparticles prepared in this example; the TEM pattern shows that both samples exhibit nanoparticle morphology with a particle size of 50-100 nm. HAADF-STEM imaging reveals that HE-Nb2O5 and pure Nb2O5 exhibit clear (001) lattice stripes with interplanar spacings of 4.1 Å and 3.9 Å, respectively. This indicates that high-entropy doping widens the interlayer spacing by 0.2 Å. Notably, the relatively dark atoms (yellow dashed line area) in the Nb layer indicate that multi-element doping occupies the Nb sites.

[0026] Figure 3are atomic HAADF-STEM and EDS mapping diagrams of HE-Nb2O5 nanoparticles prepared in this embodiment. High-resolution STEM-EDS element surface scanning proves that the five elements of Fe, Co, Ni, Cr and Al are uniformly distributed at the atomic level in the high-entropy doped Nb2O5, without element segregation.

[0027] Figure 4 are UV-Vis diffuse reflectance spectra and photon energy vs. (αhv) 2 curves of HE-Nb2O5 and pure Nb2O5 nanoparticles prepared in this embodiment. Compared with undoped niobium pentoxide, high-entropy doped niobium pentoxide shows stronger light absorption characteristics in the wavelength range of 400-1500 nm. By calculation, the band gap of high-entropy doped niobium pentoxide is only 2.75 eV, which is lower than the band gap value of undoped niobium pentoxide (3.15 eV), which indicates that high-entropy doping effectively improves the intrinsic conductivity of the material.

[0028] The high-entropy doped niobium pentoxide nanoparticles (70 mg) prepared in Example 1 were used as the negative active component, mixed with acetylene black conductive agent (20 mg) and polyvinylidene fluoride binder (10 mg) in a mass ratio of 7:2:1, 1 mL of N-methyl pyrrolidone solvent was added and stirred to form a uniform slurry, which was coated on a copper foil current collector, dried at 70°C, and then the electrode sheet was cut into 0.78 cm 2 diameter circular electrode sheets. In a glove box with strict control of moisture and oxygen content, a metal lithium sheet was used as the counter electrode, Celgard 2400 was used as the separator, and 1M LiPF6 / EC:DMC (1:1 v / v) was used as the electrolyte to assemble a CR2032 type button-shaped half battery for electrochemical performance test.

[0029] Figure 5 are CV curves of lithium ion half batteries prepared in this application in the 1-3V interval. Compared with the pure Nb2O5 system, the non-faradic and faradic current response intensity of the lithium ion half battery prepared in this application is improved by 2 times, indicating that the electrochemical reaction activity is significantly improved. The 1.56 / 1.83V and 2.04 / 1.77V significant peak pairs of Nb2O5 correspond to the Nb 5+ / Nb 4+ redox process. The 2.04 / 1.77V redox peak of HE-Nb2O5 is obviously weakened, and a new 1.37 / 1.5V wide and slow peak pair appears, revealing the reversible conversion of low-valence Nb 4+ / Nb 3+ .

[0030] Figure 6is the rate performance of the lithium ion half battery prepared in this application example under different currents, the discharge capacity of HE-Nb2O5 under different current densities of 0.5, 1, 2, 5, 10, 20, 50C and 100C is 263.9, 261.5, 251, 240, 228, 205, 184 and 163 mAh g respectively -1 , while the average discharge capacity of Nb2O5 negative electrode under the same conditions is 195, 189, 179, 160, 146, 131, 89 and 42 mAh g respectively -1 . When the current density returns to 0.5C, the discharge capacity of HE-Nb2O5 quickly recovers to 290 mAh g -1 . It is proved that high-entropy doped Nb2O5 has excellent rate performance.

[0031] Figure 7 is the long cycle stability of the lithium ion half battery prepared in this application example under 10C current density, the first cycle capacity of HE-Nb2O5 under 10C is 243 mAh g -1 , higher than the capacity of Nb2O5 (115 mAh g -1 ), and the capacity retention rate of HE-Nb2O5 after 1000 cycles is 88%.

[0032] Figure 8 is the lithium ion diffusion coefficient calculated based on the GITT test of the lithium ion half battery prepared in this application example, compared with Nb2O5, HE-Nb2O5 material shows two orders of magnitude improvement in lithium ion diffusion ability, and the DLi+ range is 7.4×10 - 8cm 2 s -1 and 3×10 - 10 cm 2 s -1 . The faster ion migration rate in HE-Nb2O5 electrode helps to achieve excellent rate performance, which also explains its high capacity and high stability in large current test.

[0033] Figure 9 is the non-in situ Nb 3p XPS spectrum of the lithium ion half battery negative electrode prepared in this application example under different battery charge and discharge states, the results show the conversion process of Nb 5+ / Nb 4+ and Nb 4+ / Nb 3+ redox couples during discharge.

[0034] Example 2 A preparation method of HE-Nb2O5 nanoparticles, comprising the following steps: 1) Dissolve 0.950 mmol of niobium pentachloride, 0.01 mmol of aluminum nitrate nonahydrate, 0.01 mmol of cobalt nitrate nonahydrate, 0.01 mmol of chromium nitrate nonahydrate, 0.01 mmol of iron nitrate nonahydrate and 0.01 mmol of nickel nitrate hexahydrate in 17 mL of ethanol, mix well to obtain a mixed solution A; 2) Dissolve 2.5 mmol of terephthalic acid in 17 mL of ethanol to obtain a mixed solution B; 3) Mix the mixed solution A and the mixed solution B well to prepare a colorless transparent precursor solution; 4) Transfer the precursor solution to a 50 mL polytetrafluoroethylene-lined hydrothermal reaction kettle, place it in a 200°C oven for reaction for 12 h, and then naturally cool to room temperature. Centrifugal collection of the precipitate, washing with anhydrous ethanol 3 times, and vacuum drying at 70°C for 12 h to obtain a precursor powder.

[0035] 5) Place the precursor in a muffle furnace, heat to 750°C at a heating rate of 5°C / min, keep for 3 h, and then cool to room temperature to obtain HE-Nb2O5 nanoparticles.

[0036] Example 3 A method for preparing HE-Nb2O5 nanoparticles, comprising the following steps: 1) Dissolve 0.950 mmol of niobium pentachloride, 0.01 mmol of aluminum nitrate nonahydrate, 0.01 mmol of cobalt nitrate nonahydrate, 0.01 mmol of chromium nitrate nonahydrate, 0.01 mmol of iron nitrate nonahydrate and 0.01 mmol of nickel nitrate hexahydrate in 17 mL of ethanol, mix well to obtain a mixed solution A; 2) Dissolve 2.5 mmol of terephthalic acid in 17 mL of ethanol to obtain a mixed solution B; 3) Mix the mixed solution A and the mixed solution B well to prepare a colorless transparent precursor solution; 4) Transfer the precursor solution to a 50 mL polytetrafluoroethylene-lined hydrothermal reaction kettle, place it in a 180°C oven for reaction for 24 h, and then naturally cool to room temperature. Centrifugal collection of the precipitate, washing with anhydrous ethanol 3 times, and vacuum drying at 70°C for 12 h to obtain a precursor powder.

[0037] 5) Place the precursor in a muffle furnace, heat to 750°C at a heating rate of 5°C / min, keep for 3 h, and then cool to room temperature to obtain HE-Nb2O5 nanoparticles.

[0038] Example 4 A method for preparing HE-Nb2O5 nanoparticles, comprising the following steps: 1) 0.950 mmol niobium pentachloride, 0.01 mmol aluminum nitrate nonahydrate, 0.01 mmol cobalt nitrate nonahydrate, 0.01 mmol chromium nitrate nonahydrate, 0.01 mmol iron nitrate nonahydrate and 0.01 mmol nickel nitrate hexahydrate were dissolved in 17 mL of ethanol, mixed uniformly to obtain a mixed solution A; 2) 2.5 mmol terephthalic acid was dissolved in 17 mL of ethanol to obtain a mixed solution B; 3) The mixed solution A and the mixed solution B were mixed uniformly to prepare a colorless transparent precursor solution; 4) The precursor solution was transferred into a 50 mL polytetrafluoroethylene-lined hydrothermal reaction kettle, placed in a 200°C oven for reaction for 12 h, and then naturally cooled to room temperature. The precipitate was collected by centrifugation, washed with anhydrous ethanol for 3 times, and vacuum dried at 70°C for 12 h to obtain a precursor powder.

[0039] 5) The precursor was placed in a muffle furnace and heated to 700°C at a heating rate of 5°C / min, kept for 3 h, and then cooled to room temperature to obtain HE-Nb2O5 nanoparticles.

[0040] Comparative Example 1 1) 1.9 mmol niobium pentachloride, 0.02 mmol aluminum nitrate nonahydrate, 0.02 mmol cobalt nitrate nonahydrate, 0.02 mmol chromium nitrate nonahydrate and 0.02 mmol nickel nitrate hexahydrate were dissolved in 35 mL of ethanol, mixed uniformly to obtain a mixed solution A; 2) 5 mmol terephthalic acid was dissolved in 35 mL of ethanol to obtain a mixed solution B; 3) The mixed solution A and the mixed solution B were mixed uniformly to prepare a colorless transparent precursor solution; 4) The precursor solution was transferred into a 70 mL polytetrafluoroethylene-lined hydrothermal reaction kettle, placed in a 200°C oven for reaction for 12 h, and then naturally cooled to room temperature. The precipitate was collected by centrifugation, washed with anhydrous ethanol for 3 times, and vacuum dried at 70°C for 12 h to obtain a precursor powder.

[0041] 5) The precursor was placed in a muffle furnace and heated to 750°C at a heating rate of 5°C / min, kept for 3 h, and then cooled to room temperature to obtain Co / Ni / Cr / Al-Nb2O5 nanoparticles.

[0042] Comparative Example 2 1) 1.9 mmol niobium pentachloride, 0.02 mmol aluminum nitrate nonahydrate, 0.02 mmol chromium nitrate nonahydrate, 0.02 mmol iron nitrate nonahydrate and 0.02 mmol nickel nitrate hexahydrate were dissolved in 35 mL of ethanol, mixed uniformly to obtain a mixed solution A; 2) Dissolve 5 mmol of terephthalic acid in 35 mL of ethanol to obtain mixed solution B; 3) Mix mixed solution A and mixed solution B uniformly to prepare a colorless transparent precursor solution; 4) Transfer the precursor solution into a 70 mL Teflon-lined autoclave, place it in a 200°C oven for 12 h, and then naturally cool to room temperature after the reaction is completed. Centrifugal collection of the precipitate, washing with anhydrous ethanol for 3 times, and vacuum drying at 70°C for 12 h to obtain a precursor powder.

[0043] 5) Place the precursor in a muffle furnace, heat to 750°C at a heating rate of 5°C / min, keep for 3 h, and then cool to room temperature to obtain Al / Ni / Cr / Fe-Nb2O5 nanoparticles.

[0044] Comparative Example 3 1) Dissolve 1.9 mmol of niobium pentachloride, 0.02 mmol of cobalt nitrate nonahydrate, 0.02 mmol of iron nitrate nonahydrate, 0.02 mmol of chromium nitrate nonahydrate, and 0.02 mmol of nickel nitrate hexahydrate in 35 mL of ethanol, mix uniformly to obtain mixed solution A; 2) Dissolve 5 mmol of terephthalic acid in 35 mL of ethanol to obtain mixed solution B; 3) Mix mixed solution A and mixed solution B uniformly to prepare a colorless transparent precursor solution; 4) Transfer the precursor solution into a 70 mL Teflon-lined autoclave, place it in a 200°C oven for 12 h, and then naturally cool to room temperature after the reaction is completed. Centrifugal collection of the precipitate, washing with anhydrous ethanol for 3 times, and vacuum drying at 70°C for 12 h to obtain a precursor powder.

[0045] 5) Place the precursor in a muffle furnace, heat to 750°C at a heating rate of 5°C / min, keep for 3 h, and then cool to room temperature to obtain Co / Ni / Cr / Fe-Nb2O5 nanoparticles.

[0046] Comparative Example 4 1) Dissolve 1.9 mmol of niobium pentachloride, 0.02 mmol of iron nitrate nonahydrate, 0.02 mmol of aluminum nitrate nonahydrate, 0.02 mmol of cobalt nitrate nonahydrate, and 0.02 mmol of chromium nitrate nonahydrate in 35 mL of ethanol, mix uniformly to obtain mixed solution A; 2) Dissolve 5 mmol of terephthalic acid in 35 mL of ethanol to obtain mixed solution B; 3) Mix mixed solution A and mixed solution B uniformly to prepare a colorless transparent precursor solution; 4) The precursor solution was transferred to a 70 mL Teflon-lined autoclave, which was placed in a 200℃ oven for 12 h. After the reaction, the product was naturally cooled to room temperature, centrifuged to collect the precipitate, washed with anhydrous ethanol for 3 times, and vacuum dried at 70℃ for 12 h to obtain the precursor powder.

[0047] 5) The precursor was placed in a muffle furnace and heated to 750℃ at a heating rate of 5℃ / min, and then cooled to room temperature to obtain Co / Al / Cr / Fe-Nb2O5 nanoparticles.

[0048] Comparative Example 5 1) 1.9 mmol of niobium pentachloride, 0.02 mmol of iron nitrate nonahydrate, 0.02 mmol of aluminum nitrate nonahydrate, 0.02 mmol of cobalt nitrate nonahydrate, and 0.02 mmol of nickel nitrate hexahydrate were dissolved in 35 mL of ethanol to obtain a mixed solution A; 2) 5 mmol of terephthalic acid was dissolved in 35 mL of ethanol to obtain a mixed solution B; 3) The mixed solution A and the mixed solution B were mixed to obtain a colorless transparent precursor solution; 4) The precursor solution was transferred to a 70 mL Teflon-lined autoclave, which was placed in a 200℃ oven for 12 h. After the reaction, the product was naturally cooled to room temperature, centrifuged to collect the precipitate, washed with anhydrous ethanol for 3 times, and vacuum dried at 70℃ for 12 h to obtain the precursor powder.

[0049] 5) The precursor was placed in a muffle furnace and heated to 750℃ at a heating rate of 5℃ / min, and then cooled to room temperature to obtain Ni / Al / Co / Fe-Nb2O5 nanoparticles.

[0050] The lithium ion half-batteries prepared in Comparative Examples 1 / 2 / 3 / 4 / 5 were tested for cycle performance. The discharge capacities were 241, 222, 212, 216 and 229 mAh g-1, respectively, at a current density of 0.5C, all of which were higher than the capacity of undoped Nb2O5, but lower than the specific capacity of HE-Nb2O5, confirming that the five elements had a synergistic effect, and the high-entropy doped Nb2O5 exhibited the highest specific capacity. -1

[0051] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application. Any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered within the protection scope of the claims of the present application.​

Claims

1. A high entropy doped niobium pentoxide nanoparticle, characterized in that, The chemical formula of the high-entropy doped niobium pentoxide nanoparticles is Nb 1-x Fe a Co e Ni i Cr j Al k O2, where x = a + e + i + j + k, 0.04 ≤ x ≤ 0.06, 0 < a < 1, 0 < e < 1, 0 < i < 1, 0 < j < 1, 0 < k < 1; it has an orthorhombic crystal system, space group P2 / m, the doped metals occupy the Nb sites in an atomically dispersed manner, and the c-axis of the unit cell parameter extends to 0.41 nm; the nanoparticle size is 50 - 200 nm.

2. The high entropy doped niobium pentoxide nanoparticles of claim 1, wherein, The nanoparticles have a discharge capacity at 100 C rate of no less than 156 mAh g -1 , and a lithium ion diffusion coefficient of 10 -8 -10 -10 cm 2 / s.

3. The high entropy doped niobium pentoxide nanoparticles of claim 1, wherein, The value of x is 0.

05.

4. A method of preparing high entropy doped niobium pentoxide nanoparticles as claimed in any one of claims 1 to 3, characterized in that, The method comprises the following steps: (1) Dissolving a niobium source, an iron source, a cobalt source, a nickel source, a chromium source and an aluminum source in N,N-dimethylformamide or ethanol to form a metal mixed solution A; (2) Dissolving an organic ligand in N,N-dimethylformamide or ethanol to form a ligand solution B; (3) Mixing solution A and solution B uniformly to prepare a precursor solution; (4) Placing the precursor solution in a hydrothermal reaction kettle and reacting at 160-220 DEG C for 6-24 hours; after the reaction is completed, centrifuging, washing and drying to obtain a precursor; (5) Sintering the precursor under a protective atmosphere to obtain the high-entropy doped niobium pentoxide nanoparticles.

5. The preparation method according to claim 4, characterized in that, The niobium source is niobium pentachloride; the iron source is ferric chloride or ferric nitrate; the cobalt source is cobalt chloride or cobalt nitrate; the nickel source is nickel chloride or nickel nitrate; the chromium source is chromium chloride or chromium nitrate; and the aluminum source is aluminum chloride or aluminum nitrate.

6. The production method according to claim 4, characterized by, The organic ligand is terephthalic acid; and the molar ratio of the organic ligand to the niobium source is (2-5):

1.

7. The production method according to claim 4, characterized by, In step (1), the molar volume ratio of the niobium source to N,N-dimethylformamide or ethanol is 1 mmol:(15-23) mL; and in step (2), the molar volume ratio of the organic ligand to N,N-dimethylformamide or ethanol is 1 mmol:(1-1.6) mL.

8. The preparation method according to claim 4, characterized in that, In step (5), the sintering is heated to 700-800 DEG C at a heating rate of 2-5 DEG C / min, and after holding for 3-6 hours, it is cooled to room temperature.

9. A lithium-ion battery anode material, characterized in that, The high-entropy doped niobium pentoxide nanoparticles of any one of claims 1-3.

10. A lithium-ion battery, characterized by The negative electrode of the lithium ion battery uses the negative electrode material of claim 9; the capacity retention rate of the battery is not less than 88% after 1000 cycles at a rate of 10 C, and the volume change rate is less than 1.5%.

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