Lithium ion battery negative electrode material with single-crystal-to-single-crystal conversion performance and preparation method of lithium ion battery negative electrode material

Abstract

The invention discloses a lithium ion battery negative electrode material with single crystal-to-single crystal conversion performance and a preparation method thereof, the structural formula of the lithium ion battery negative electrode material with the single crystal-to-single crystal conversion performance is Li2K5Sb (OH2) (GeNb12VV2O42) 8H2O, VV represents that the valence state of V is pentavalent, and the structural formula of the lithium ion battery negative electrode material with the single crystal-to-single crystal conversion performance is Li2K5Sb (OH2) (GeNb12VV2O42) 8H2O. After the lithium ion battery negative electrode material with the single crystal-to-single crystal conversion performance is subjected to single crystal-to-single crystal conversion, the structural formula is H3K2LiVVSb (OH2) [GeNb12O40 (VIVO)]. 8H2O, and VIV represents that the valence state of V is tetravalent; the crystal structure of the lithium ion battery negative electrode material with the single crystal-to-single crystal conversion performance is a three-dimensional frame structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of single-crystal to single-crystal transformation materials, and particularly relates to a lithium-ion battery anode material with single-crystal to single-crystal transformation performance and a preparation method thereof. Background Art

[0002] The continuous growth of global energy demand has greatly accelerated the research on high-performance, cost-effective and sustainable energy storage technologies. Among various options, lithium-ion batteries (LIBs) currently occupy an important position in the energy storage market due to their advantages such as high working potential and amazing energy / power density. However, their relatively low capacity (the theoretical value is 372 mAh g -1 ) is still difficult to meet the application requirements of electric vehicles. Therefore, it is of great significance to develop high-capacity anode materials to reach new performance benchmarks. In the past few decades, various promising anode materials have been explored, such as pure metals, metal oxides and metal sulfides, and the conversion / alloying reaction mechanisms of these materials can improve the performance of LIBs. Orthorhombic Nb 2 O 5 is well-known for its fast energy storage ability and has become a high-rate anode material for lithium-ion batteries, showing great potential in future applications. However, despite various strategies such as doping, surface functionalization, defect engineering, etc., the capacity of Nb 2 O 5 is still limited to about 200 mAh g -1 , which is difficult to meet the requirements of practical applications. The main reason is that people lack sufficient understanding of the relationship between the structure and capacity of niobium-based materials. Therefore, developing new strategies to obtain high-rate niobium-based materials with higher capacity is crucial for improving battery performance.

[0003] Polyoxometalates (POMs), also known as polyoxoanions, usually refer to inorganic oxygenates of high-valent transition metals such as V, Nb, Ta, Mo, and W that form polynuclear metal cluster structures through polycondensation and dehydration. Polyoxoniobates (PONbs) are a type of niobate anion composed of Nb and O atoms, with a well-defined structure that can accommodate a large number of electrons and ions while maintaining structural stability. Therefore, they are a promising anode material for LIBs. In addition, their structural tunability and modifiability allow for single-crystal-to-single-crystal transformations under external stimuli, providing a rare opportunity to study the relationship between structure and capacity at the atomic level. In particular, the effect of single-crystal-to-single-crystal transformation on the performance of LIBs anode materials has not been reported. However, it is well known that the synthesis of PONbs faces challenges due to the narrow pH range of dissolution, strong alkalinity, low solubility, and low reactivity of niobates, resulting in a very limited number of known PONbs structure types. Notably, the all-inorganic extended PONbs frameworks bridged by metal linkers through coordination or covalent bonds are still very limited. Summary of the Invention

[0004] To solve the above problems, the present invention proposes a lithium-ion battery anode material with single-crystal-to-single-crystal transformation performance and a preparation method thereof.

[0005] The present invention adopts the following technical solutions:

[0006] A lithium-ion battery anode material with single-crystal-to-single-crystal transformation performance, the structural formula of the lithium-ion battery anode material with single-crystal-to-single-crystal transformation performance is Li 2 K 5 Sb(OH 2 )(GeNb 12 V V 2 O 42 )8H 2 O, abbreviated as FZU-3, where V V represents that the valence state of V is pentavalent; the structural formula of the lithium-ion battery anode material with single-crystal-to-single-crystal transformation performance after single-crystal-to-single-crystal transformation is H 3 K 2 LiV V Sb(OH 2 )[GeNb 12 O 40 (V IV O)]·8H 2 O, abbreviated as FZU-3H, where V IV represents that the valence state of V is tetravalent; the crystal structure of the lithium-ion battery anode material with single-crystal-to-single-crystal transformation performance is a three-dimensional framework structure.

[0007] Preferably, the crystal structure of the anode material for a lithium-ion battery with single-crystal to single-crystal transformation performance belongs to the tetragonal crystal system, the space group is I4-mmm, and the unit cell parameters are: a = 10.77(5), b = 10.77(5), α = β = γ = 90°; after the single-crystal transformation of the anode material for a lithium-ion battery with single-crystal to single-crystal transformation performance, the crystal still belongs to the tetragonal crystal system, the space group is I4mm, and the unit cell parameters are: a = 10.69(2), b = 10.69(2), α = β = γ = 90°.

[0008] A preparation method of an anode material for a lithium-ion battery with single-crystal to single-crystal transformation performance includes the following steps:

[0009] S1. Synthesize the niobate precursor K 7 HNb 6 O 19 ·13H 2 O;

[0010] S2. Weigh the niobate precursor, vanadium pentoxide, antimony trioxide, germanium dioxide, lithium chloride and 5 mL of deionized water into a 23 mL polytetrafluoroethylene autoclave, and stir at room temperature for 1 h to mix the raw materials evenly;

[0011] S3. Place the polytetrafluoroethylene autoclave in an oven for hydrothermal reaction;

[0012] S4. Cool the polytetrafluoroethylene autoclave after the hydrothermal reaction to room temperature, filter, wash with 100 mL of deionized water, and then dry in a vacuum drying oven for 12 h to obtain colorless block crystals, which are the anode material for a lithium-ion battery with single-crystal to single-crystal transformation performance.

[0013] Preferably, the addition molar ratio of the niobate precursor, vanadium pentoxide, antimony trioxide, germanium dioxide and lithium chloride in step S2 is 4:5:8:4:3.

[0014] Preferably, the reaction temperature of the hydrothermal reaction in step S3 is 160 °C and the reaction time is 5 days.

[0015] Preferably, the anode material for a lithium-ion battery with single-crystal to single-crystal transformation performance obtained in step S4 is soaked in formic acid to undergo single-crystal to single-crystal transformation.

[0016] After adopting the above technical solution, compared with the background technology, the present invention has the following advantages: The anode material for a lithium-ion battery with single-crystal to single-crystal transformation performance prepared by the present invention contains a rare inorganic two-dimensional PONbs framework, can be used as an anode material for a lithium-ion battery, and has the potential to be an advanced anode material for LIBs. During the migration of V to the framework layer and the V of the secondary structural unitV Reduced to V IV Driven by the single-crystal to single-crystal transformation of , FZU-3H exhibits faster reaction kinetics and a higher lithium-ion diffusion rate. Therefore, at a current density of 1 A g -1 , the specific capacity of FZU-3H reaches 286 mAh g -1 . Electrochemical evaluation and in-situ XRD results show that the high capacitance and fast kinetics of FZU-3H are mainly attributed to the capacitance under low-voltage conditions. In addition, theoretical calculations show that the single-crystal to single-crystal transformation generates more voids, which can accommodate more lithium ions and reduce the transfer energy barrier of lithium ions. Description of the Drawings

[0017] Figure 1 The figure shows the anode material of a lithium-ion battery with single-crystal to single-crystal transformation performance prepared by the present invention and the crystal morphology diagram after single-crystal transformation;

[0018] Figure 2 The figure shows the structure diagram of the anode material of a lithium-ion battery with single-crystal to single-crystal transformation performance prepared by the present invention and after single-crystal transformation;

[0019] Figure 3 The figure shows the powder diffraction pattern of the anode material of a lithium-ion battery with single-crystal to single-crystal transformation performance prepared by the present invention and after single-crystal transformation;

[0020] Figure 4 The figure shows the infrared spectrum of the anode material of a lithium-ion battery with single-crystal to single-crystal transformation performance prepared by the present invention and after single-crystal transformation;

[0021] Figure 5 The figure shows the ultraviolet absorption spectrum of the anode material of a lithium-ion battery with single-crystal to single-crystal transformation performance prepared by the present invention and after single-crystal transformation;

[0022] Figure 6 The figure shows the cyclic voltammetry comparison diagram of a lithium-ion battery of the anode material of a lithium-ion battery with single-crystal to single-crystal transformation performance prepared by the present invention and after single-crystal transformation;

[0023] Figure 7 The figure shows the galvanostatic charge-discharge comparison diagram of a lithium-ion battery of the anode material of a lithium-ion battery with single-crystal to single-crystal transformation performance prepared by the present invention and after single-crystal transformation;

[0024] Figure 8 The figure shows the long-term cycling performance comparison diagram of a lithium-ion battery of the anode material of a lithium-ion battery with single-crystal to single-crystal transformation performance prepared by the present invention and after single-crystal transformation. Detailed Embodiments

[0025] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] See Figures 1 to 8 。

[0027] Example 1

[0028] Li 2 K 5 Sb(OH 2 )(GeNb 12 V V 2 O 42 )8H 2 O (abbreviated as FZU-3) preparation:

[0029] S1. Synthesize the niobate precursor K 7 HNb 6 O 19 ·13H 2 O, and the synthesis method is in accordance with the method provided in the literature "Inorganic Chemistry" (Inorganic Chemistry) (pages 93-103, Volume 18, 1979).

[0030] S2. Weigh the niobate precursor, vanadium pentoxide, antimony trioxide, germanium dioxide and lithium chloride according to a molar ratio of 4:5:8:4:3, with 5 mL of deionized water, add them to a 23 mL polytetrafluoroethylene autoclave, and then stir them at room temperature for 1 h to mix the raw materials evenly. After stirring, place the polytetrafluoroethylene autoclave in an iron autoclave.

[0031] S3. Place the fixed polytetrafluoroethylene autoclave at 160 °C for 5 days under constant temperature to allow it to fully carry out the hydrothermal reaction.

[0032] S4. Cool the polytetrafluoroethylene autoclave after the hydrothermal reaction to room temperature, filter, wash it with 100 mL of deionized water respectively, and then dry it in a vacuum drying oven for 12 h to obtain brown block crystals, that is, obtain the anode material Li of the lithium-ion battery with the property of single crystal to single crystal transformation 2 K 5 Sb(OH 2 )(GeNb 12 V V 2 O 42 )8H 2 O, as Figure 1 shown in the left figure in

[0033] Example 2

[0034] H3 K 2 LiV V Sb(OH 2 )[GeNb 12 O 40 (V IV O)]·8H 2 O (abbreviated as FZU - 3H) Preparation:

[0035] The lithium - ion battery anode material Li obtained in Example 1 with single - crystal to single - crystal transformation performance 2 K 5 Sb(OH 2 )(GeNb 12 V V 2 O 42 )8H 2 O has single - crystal to single - crystal transformation performance. Soak the brown block - shaped crystal with formic acid to obtain the green block - shaped crystal H 3 K 2 LiV V Sb(OH 2 )[GeNb 12 O 40 (V IV O)]·8H 2 O, as shown in the right - hand figure of Figure 1 Use the two kinds of crystals obtained in Example 1 and Example 2 as the lithium - ion battery anode materials.

[0036] Characterization and Performance Testing of Crystals:

[0037] (1) Crystal Structure Determination

[0038] Select single crystals with appropriate size, regular shape and transparency under the microscope. Use Mo - Kα radiation monochromatized by a graphite monochromator as the incident light source through a Bruker APEX II CCD diffractometer to collect crystal diffraction data at 175(2)K. In the structure analysis, use the Shelextl - 97 program to analyze and refine the crystal structure by the direct method. At the same time, use the full - matrix least - squares method to correct the non - hydrogen atoms and their anisotropic treatment parameters. All hydrogen atoms are obtained by theoretical hydrogenation. The obtained crystal structure diagram is as shown in Part of the crystallographic data and refinement parameters are shown in Table 1. Figure 2 Shown.

[0039] Table 1: Crystal Parameter Table of Compounds

[0040]

[0041]

[0042] (2) Powder diffraction characterization:

[0043] Take an appropriate amount of the single crystal prepared by the method of the above-mentioned embodiment 1 and embodiment 2, grind it into powder, and measure the powder diffraction pattern of the conductive material at room temperature (such as Figure 3 The comparison of the diffraction peaks simulated based on single crystal diffraction data shows that the experimental results are in good agreement with the fitting results of Mercury software, which indicates that the compound is pure phase. The anisotropy of the crystal causes some diffraction peaks to differ in peak intensity.

[0044] (3) Infrared spectroscopy characterization:

[0045] like Figure 4 As shown, compounds FZU-3 and FZU-3H have a peak at 3247 cm -1 and 1638cm -1 The absorption peak at 1000-400cm is attributed to the characteristic absorption of crystal water and coordinated water in the structure. -1 Several absorption peaks appearing in the range can be attributed to the characteristic absorption peaks of Nb-O bonds, 836 cm -1 Belongs to ν(Nb=O t ) stretching vibration, 646cm -1 , 511cm -1 and 403cm -1 The peak position is assigned to ν(Nb-O b -Nb) stretching vibration.

[0046] (4) UV absorption spectrum characterization:

[0047] like Figure 5 As shown in Figure 2, the broad absorption bands of compounds FZU-3 and FZU-3H at 210 nm and 270 nm are mainly attributed to the charge transfer transition from O to Nb, and the broad absorption band of compound FZU-3H at 700 nm is attributed to V IV dd transition.

[0048] (5) Selective ion exchange test with biomimetic properties:

[0049] Test method: Mix the crystal, conductive carbon black and binder in a ratio of 7:2:1, use water as solvent to make a slurry, apply it on the copper foil, dry it in a vacuum drying oven at 60 degrees overnight, cut it into discs and assemble it into 2032 button batteries for electrochemical performance testing.

[0050] Figure 6 A comparison diagram of the cyclic voltammetry of a lithium-ion battery negative electrode material having single crystal to single crystal transformation performance and a lithium-ion battery after single crystal transformation; Figure 7The negative electrode material of a lithium-ion battery with single-crystal to single-crystal transformation performance and the comparison chart of constant current charge and discharge of the lithium-ion battery after single-crystal transformation; Figure 8 The negative electrode material of a lithium-ion battery with single-crystal to single-crystal transformation performance and the comparison chart of long cycle performance of the lithium-ion battery after single-crystal transformation.

[0051] As mentioned above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A lithium-ion battery negative electrode material having single crystal to single crystal transformation performance, characterized in that: The structural formula of the lithium ion battery negative electrode material with single crystal to single crystal transformation performance is Li2K5Sb(OH2)(GeNb 12 V V 2O 42 )8H2O, where V V Indicates that the valence state of V is pentavalent; the structural formula of the lithium-ion battery negative electrode material having single crystal to single crystal transformation performance after single crystal to single crystal transformation is H3K2LiV V Sb(OH2)[GeNb 12 O 40 (V IV O)]·8H2O, where V IV It indicates that the valence state of V is tetravalent; the crystal structure of the lithium-ion battery negative electrode material with single crystal to single crystal transformation performance is a three-dimensional framework structure.

2. A lithium-ion battery negative electrode material having single crystal to single crystal transformation performance as claimed in claim 1, characterized in that: The crystal structure of the lithium-ion battery negative electrode material with single crystal to single crystal transformation performance belongs to the tetragonal system, the space group is I4-mmm, and the unit cell parameters are: a=10.77(5), b=10.77(5), α=β=γ=90°; after the single crystal transformation of the lithium ion battery negative electrode material having single crystal to single crystal transformation, the crystal still belongs to the tetragonal system, the space group is I4mm, and the unit cell parameters are: a=10.69(2), b=10.69(2), α=β=γ=90.

3. A method for preparing a lithium-ion battery negative electrode material having single crystal to single crystal transformation performance as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Synthesis of niobate precursor K7HNb6O 19 13H2O; S2. Weigh the niobate precursor, vanadium pentoxide, antimony trioxide, germanium dioxide, lithium chloride and 5 mL of deionized water into a 23 mL polytetrafluoroethylene kettle, and stir at room temperature for 1 h to mix the raw materials evenly; S3, placing the polytetrafluoroethylene kettle in an oven for hydrothermal reaction; S4. Cool the polytetrafluoroethylene kettle after the hydrothermal reaction to room temperature, filter it, and then wash it with 100 mL of deionized water. Then, dry it in a vacuum drying oven for 12 hours to obtain colorless block crystals, which are lithium-ion battery negative electrode materials with single crystal to single crystal transformation performance.

4. The method for preparing a lithium ion battery negative electrode material having single crystal to single crystal transformation performance as claimed in claim 3, characterized in that: The molar ratio of the niobate precursor, vanadium pentoxide, antimony trioxide, germanium dioxide and lithium chloride added in step S2 is 4:5:8:4:

3.

5. The method for preparing a lithium ion battery negative electrode material having single crystal to single crystal transformation performance as claimed in claim 3, characterized in that: The reaction temperature of the hydrothermal reaction in step S3 is 160° C., and the reaction time is 5 days.

6. The method for preparing a lithium ion battery negative electrode material having single crystal to single crystal transformation performance as claimed in claim 3, characterized in that: The lithium-ion battery negative electrode material with single crystal to single crystal transformation performance obtained in step S4 is immersed in formic acid to cause single crystal to single crystal transformation.

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