A lithium ion battery anode material with single crystal to single crystal transformation performance and a preparation method thereof

Abstract

The application discloses a lithium ion battery negative electrode material with single crystal to single crystal transformation performance and a preparation method thereof. 12 V V 2O 42 )8H2O, wherein V V represents that the valence of V is five; a structural formula of the lithium ion battery negative electrode material after single crystal to single crystal transformation is H3K2LiV V Sb(OH2)[GeNb 12 O 40 (V IV O)]·8H2O, wherein V IV represents that the valence of V is four; and the lithium ion battery negative electrode material with single crystal to single crystal transformation performance has a three-dimensional framework structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of single crystal to single crystal transformation materials, and particularly relates to a lithium ion battery negative electrode material with single crystal to single crystal transformation performance and a preparation method thereof. BACKGROUND

[0002] The continuous growth of global energy demand has greatly accelerated the research on high-performance, high-cost-effective and sustainable energy storage technologies. Among various choices, lithium ion batteries (LIBs) currently occupy an important position in the energy storage market due to their high working potential and amazing energy / power density. However, its relatively low capacity (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 achieve new performance benchmarks. In the past few decades, people have explored various promising anode materials such as pure metals, metal oxides and metal sulfides, and the conversion / alloying reaction mechanism of these materials can improve the performance of LIBs. Orthorhombic Nb2O5 is known for its fast energy storage capacity and has become a high-rate anode material for lithium ion batteries, showing great potential in future applications. However, despite the use of various strategies such as doping, surface functionalization and defect engineering, the capacity of Nb2O5 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, it is essential to develop new strategies to obtain high-rate niobium-based materials with higher capacity to improve battery performance.

[0003] Polyoxometalates (POMs) are also known as polyacids, which are usually inorganic oxyacid salts of high-valent transition metals such as V, Nb, Ta, Mo and W, which form a multi-core metal cluster structure through condensation and dehydration. Polyoxoniobates (PONbs) are a class of niobate anions composed of Nb atoms and O atoms, which have a clear structure and can accommodate a large number of electrons and ions while maintaining structural stability, so they are a very promising LIBs negative electrode material. In addition, their structure tunability and modifiability allow single crystal to single crystal transformation to occur under external stimuli, which provides a rare opportunity to study the relationship between structure and capacity at atomic level. In particular, the effect of single crystal to single crystal transformation on the performance of LIBs negative electrode materials has not been reported. However, it is well known that the synthesis is challenging due to the narrow pH range of niobate dissolution, strong alkalinity, low solubility and low reactivity, so the known PONbs structure types are very limited. Notably, fully inorganic extended PONbs frameworks bridged by metal linkers through coordination or covalent bonds are still very limited. SUMMARY

[0004] To solve the above problems, the application provides a lithium ion battery negative electrode material with single crystal to single crystal transformation performance and a preparation method thereof.

[0005] The application adopts the following technical scheme:

[0006] The lithium ion battery negative electrode material with single crystal to single crystal transformation performance has a structural formula of Li2K5Sb(OH2)(GeNb 12 V V 2O 42 )8H2O, which is abbreviated as FZU-3, wherein V V represents that the valence of V is five; the lithium ion battery negative electrode material with single crystal to single crystal transformation performance has a structural formula of H3K2LiV V Sb(OH2)[GeNb 12 O 40 (V IV O)]·8H2O after single crystal to single crystal transformation, which is abbreviated as FZU-3H, wherein V IV represents that the valence of V is four; and 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.

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

[0008] The application further provides a preparation method of the lithium ion battery negative electrode material with single crystal to single crystal transformation performance.

[0009] S1, synthesizing a niobate precursor K7HNb6O 19 ·13H2O;

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

[0011] S3, placing the polytetrafluoroethylene kettle in an oven to perform a hydrothermal reaction;

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

[0013] Preferably, 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.

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

[0015] Preferably, the lithium ion battery negative electrode material 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 the above technical solution, the present application has the following advantages compared with the background art: the lithium ion battery negative electrode material with single crystal to single crystal transformation performance prepared by the present application contains a rare inorganic two-dimensional PONbs framework, which can be used as a lithium ion battery negative electrode material and has the potential to be an advanced negative electrode material for LIBs. The V V reduction to V IV Under the driving of single crystal to single crystal transformation, FZU-3H shows faster reaction kinetics and higher lithium ion diffusion rate. Therefore, when the current density is 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 capacity and fast kinetics of FZU-3H are mainly due to the capacitance under low voltage conditions. In addition, theoretical calculations show that the single crystal to single crystal transformation produces more voids, which can accommodate more lithium ions and reduce the transfer energy barrier of lithium ions. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The lithium ion battery negative electrode material with single crystal to single crystal transformation performance prepared by the present application and the crystal morphology diagram after single crystal transformation;

[0018] Figure 2 The lithium ion battery negative electrode material with single crystal to single crystal transformation performance prepared by the present application and the structure diagram after single crystal transformation;

[0019] Figure 3 The lithium ion battery negative electrode material with single crystal to single crystal transformation performance prepared by the present application and the powder diffraction diagram after single crystal transformation;

[0020] Figure 4The lithium ion battery negative electrode material with single crystal to single crystal transformation performance prepared by the application and the infrared spectrum diagram after single crystal transformation;

[0021] Figure 5 The lithium ion battery negative electrode material with single crystal to single crystal transformation performance prepared by the application and the ultraviolet absorption spectrum diagram after single crystal transformation;

[0022] Figure 6 The lithium ion battery negative electrode material with single crystal to single crystal transformation performance prepared by the application and the lithium ion battery cyclic voltammetry comparison diagram after single crystal transformation;

[0023] Figure 7 The lithium ion battery negative electrode material with single crystal to single crystal transformation performance prepared by the application and the lithium ion battery constant current charge and discharge comparison diagram after single crystal transformation;

[0024] Figure 8 The lithium ion battery negative electrode material with single crystal to single crystal transformation performance prepared by the application and the lithium ion battery long cycle performance comparison diagram after single crystal transformation. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the application more clear and understandable, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and do not limit the application.

[0026] Reference should be made to Figures 1 to 8 .

[0027] Example 1

[0028] Li2K5Sb(OH2)(GeNb 12 V V 2O 42 )8H2O (abbreviation FZU-3) preparation:

[0029] S1, synthesis of niobate precursor K7HNb6O 19 ·13H2O, the synthesis method is according to the method provided in the literature Inorganic Chemistry (1979, Vol. 18, 93-103).

[0030] S2, niobate precursor, vanadium pentoxide, antimony trioxide, germanium dioxide and lithium chloride are weighed according to the molar ratio of 4:5:8:4:3, deionized water is 5 mL, which is added into a 23 mL polytetrafluoroethylene kettle, then it is stirred at room temperature for 1 h to make the raw materials uniformly mixed, and after stirring, the polytetrafluoroethylene kettle is placed in an iron kettle.

[0031] S3. Place the fixed polytetrafluoroethylene reactor at 160℃ for 5 days to allow it to undergo a full hydrothermal reaction.

[0032] S4. After the hydrothermal reaction, the polytetrafluoroethylene reactor was cooled to room temperature, filtered, and then washed with 100 mL of deionized water. The mixture was then dried in a vacuum drying oven for 12 hours to obtain brown blocky crystals, which constitute the lithium-ion battery anode material Li2K5Sb(OH2)(GeNb) exhibiting single-crystal to single-crystal transformation properties. 12 V V 2O 42 )8H2O, such as Figure 1 As shown in the middle left figure.

[0033] Example 2

[0034] H3K2LiV V Sb(OH2)[GeNb 12 O 40 (V IV Preparation of FZU-3H (O)]·8H2O:

[0035] The lithium-ion battery anode material Li2K5Sb(OH2)(GeNb) with single-crystal to single-crystal transition performance obtained in Example 1 12 V V 2O 42 8H2O exhibits single-crystal-to-single-crystal transformation properties; soaking brown blocky crystals in formic acid yields green blocky crystals (H3K2LiV). V Sb(OH2)[GeNb 12 O 40 (V IV O)]·8H2O, such as Figure 1 As shown in the middle right figure, the two crystals obtained in Example 1 and Example 2 were used as negative electrode materials for lithium-ion batteries.

[0036] Characterization and performance testing of crystals:

[0037] (1) Crystal structure determination

[0038] Select a single crystal of suitable size, regular shape, and transparency under a microscope. Then, using a Bruker APEX II CCD diffractometer at 175(2)K, monochromatize the Mo-Kα rays with a graphite monochromator. The incident light source was used to collect crystal diffraction data. In the structural analysis, the Shelextl-97 program was used to directly analyze and refine the crystal structure. Simultaneously, non-hydrogen atoms and their anisotropic treatment parameters were corrected using the full-matrix least squares method. All hydrogen atoms were obtained through theoretical hydrogenation. The resulting crystal structure diagram is shown below. Figure 2Part of the crystallographic data and refinement parameters are shown in Table 1.

[0039] Table 1: Crystal parameters of the compound

[0040]

[0041]

[0042] (2) Powder diffraction characterization:

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

[0044] (3) Infrared spectroscopy characterization:

[0045] As shown in Figure 4 , the absorption peaks of compound FZU-3 and FZU-3H at 3247 cm -1 and 1638 cm -1 belong to the characteristic absorption of the crystal water and the coordinated water in the structure, and several absorption peaks in the range of 1000-400 cm -1 can be attributed to the characteristic absorption peaks of Nb-O bond, 836 cm -1 belongs to the stretching vibration of ν(Nb=O t ), 646 cm -1 , 511 cm -1 and 403 cm -1 peak position belongs to the stretching vibration of ν(Nb-O b -Nb).

[0046] (4) Ultraviolet absorption spectroscopy characterization:

[0047] As shown in Figure 5 , the wide absorption band of compound FZU-3 and FZU-3H at 210 nm and 270 nm is mainly due to the charge transfer transition from O to Nb, and the wide absorption band of compound FZU-3H at 700 nm is due to the d-d transition of V IV .

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

[0049] Test method: mix the crystal, conductive carbon black and binder in proportion of 7:2:1, use water as solvent to adjust the slurry, coat on the copper foil, dry in the vacuum drying oven at 60 degrees overnight, cut into round pieces to assemble into 2032 button cells for electrochemical performance test.

[0050] Figure 6 Lithium ion battery negative material with single crystal to single crystal transition performance and lithium ion battery cyclic voltammetry comparison chart after single crystal transition; Figure 7 Lithium ion battery negative material with single crystal to single crystal transition performance and lithium ion battery constant current charge-discharge comparison chart after single crystal transition; Figure 8 Lithium ion battery negative material with single crystal to single crystal transition performance and lithium ion battery long cycle performance comparison chart after single crystal transition.

[0051] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A lithium-ion battery anode material having single crystal to single crystal transformation properties, characterized in that: The structure 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, wherein V V represents that the valence of V is five; the structure formula of the lithium ion battery negative electrode material with 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, wherein V IV represents that the valence of V is four; 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. The anode material for lithium-ion batteries with single crystal to single crystal transformation properties according to 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 tetragonal system, space group is I 4 / mmm, the cell parameters are: a = 10.77(5), b = 10.77(5), c = 10.99(10) (Å), α = β = γ = 90°; the crystal of the lithium ion battery negative electrode material with single crystal to single crystal transformation performance still belongs to tetragonal system after single crystal transformation, space group is I 4mm, the cell parameters are: a = 10.69(2), b = 10.69(2), c = 10.76(7) (Å), α = β = γ = 90°.

3. A method of producing a lithium-ion battery anode material having single crystal to single crystal transformation properties according to any one of claims 1-2, characterized in that, The method comprises the following steps: S1, synthesis of niobate precursor K7HNb6O 19 • 13H2O; S2, niobate precursor, vanadium pentoxide, antimony trioxide, germanium dioxide, lithium chloride and 5 mL of deionized water are weighed into a 23 mL Teflon kettle, and the raw materials are stirred at room temperature for 1 h to mix uniformly; S3, the Teflon kettle is placed in an oven for hydrothermal reaction; S4, the Teflon kettle after hydrothermal reaction is cooled to room temperature, filtered, washed with 100 mL of deionized water, and then dried in a vacuum drying box for 12 h to obtain a colorless block crystal, which is a lithium ion battery negative electrode material with single crystal to single crystal conversion performance.

4. The method for preparing a lithium-ion battery anode material with single-crystal to single-crystal transition performance as described in claim 3, characterized in that: The addition mole ratio of the niobate precursor, vanadium pentoxide, antimony trioxide, germanium dioxide and lithium chloride in step S2 is 4:5:8:4:

3.

5. The method for preparing a lithium-ion battery anode material with single-crystal to single-crystal transition performance as described in claim 3, characterized in that: The reaction temperature of the hydrothermal reaction in step S3 is 160℃, and the reaction time is 5 days.

6. The method for preparing a lithium-ion battery anode material with single-crystal to single-crystal transition performance as described in claim 3, characterized in that: The lithium ion battery negative electrode material with single crystal to single crystal conversion performance obtained in step S4 is soaked in formic acid to undergo single crystal to single crystal conversion.

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