Preparation method of hollow porous microsphere LiVO3 / C lithium ion battery negative electrode material

Abstract

The present invention relates to a method for preparing a novel hollow porous microsphere LiVO3 / C lithium ion battery negative electrode material. A synthesis process of spray drying and subsequent calcination was used to successfully prepare a hollow porous LiVO3 / C microsphere composite material using a template method. The specific operation is as follows: Step 1: Take Li2CO3, V2O5, C6H 12 N₄ is dissolved in an appropriate amount of deionized water, stirred and mixed thoroughly, and then hydrothermally treated. The resulting precursor solution is diluted, an appropriate amount of carbon source is added, and stirred thoroughly before spray drying and solid-phase sintering to produce Li₃VO₄ / C hollow porous microspheres. The second step involves ball milling the Li₃VO₄ / C with V₂O₅, ultrasonically mixing in an ethanol solution, and then drying. Finally, the dried material is calcined in air to produce the hollow porous microsphere LiVO₃ / C lithium-ion battery anode material. This method addresses the problems of LiVO₃, such as the difficulty in controlling its morphology, poor conductivity, and unstable performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for preparing a novel hollow porous microsphere LiVO3 / C lithium ion battery negative electrode material. Background Art

[0002] With the advancement of science and technology and the rapid development of human society, humanity's demand for energy is increasing day by day. The reserves of non-renewable energy sources such as coal, oil, and natural gas are rapidly depleting, leading to serious energy crises and pollution problems. The global energy structure is transforming towards clean, intelligent, and low-carbon energy, and the development of renewable energy has become the mainstream direction of global energy transformation. Lithium-ion batteries are widely used in communication facilities, power tools, and energy storage due to their advantages such as no memory effect, long cycle life, and environmental friendliness. However, with the development of science and technology, people have placed increasingly higher demands on lithium-ion batteries. Lithium-ion battery materials with high energy density, long cycle life, and low cost are currently the focus of research.

[0003] Traditional lithium-ion battery materials are increasingly unable to meet the needs of existing lithium-ion batteries. Currently, the most widely used graphite anode material in commercial lithium-ion batteries has a low battery power density due to its low theoretical capacity, and the lithium dendrites generated on the graphite electrode are prone to safety issues. Silicon-based anode materials are ideal anode materials for lithium-ion batteries, but their volume expansion can reach 300%, seriously affecting the cycle performance of silicon anode materials. In recent years, vanadate materials have been used as lithium-ion battery anode materials due to their advantages such as high energy density, high safety and small volume effect, and have been increasingly widely studied. Among them, vanadate materials such as Li3VO4, LiVO2, and Li3V2O5 have demonstrated strong application potential and are also current research hotspots. There is no doubt that the development of new vanadate materials is expected to further improve the performance of lithium-ion batteries, thereby promoting the development of lithium-ion batteries.

[0004] LiVO3 has a monoclinic structure and was initially used as a positive electrode material for lithium-ion batteries. However, there has been less research on negative electrode materials for lithium-ion batteries. From the chemical composition of LiVO3 itself, the vanadium element in it has a valence of +5, and theoretically it can also be reduced and used as a negative electrode material for lithium-ion batteries. Recent studies have found that LiVO3 as a negative electrode material for lithium-ion batteries has high specific capacity, high ionic conductivity and high coulombic efficiency, and has strong application value. The key factors restricting the development of LiVO3 negative electrode materials are: (1) The material has strong water absorption, making its morphology difficult to control. Currently, there are few reports on LiVO3 negative electrode materials with special morphologies; (2) LiVO3 negative electrode materials are difficult to composite with carbon. The synthesis of LiVO3 often needs to be achieved under air conditions, while composite with carbon can usually only be achieved under protective gas. In the presence of a carbon source, V is easily reduced to a lower valence state, and LiVO3 cannot be obtained. The preparation of LiVO3 / C composite materials with special morphology has always been a difficulty, which makes LiVO3 used as a negative electrode material for lithium-ion batteries have problems such as easy capacity attenuation and poor rate performance, thus limiting its further development.

[0005] Based on the above background, this patent develops a method for preparing hollow porous LiVO3 / C microsphere composite materials through a template method. A Li3VO4 / C microsphere composite material with a hollow porous structure is prepared by spray drying and subsequent annealing as a template. A vanadium source is then introduced, and finally, a hollow porous LiVO3 / C microsphere composite material is successfully prepared by low-temperature annealing in an air atmosphere. The prepared LiVO3 / C microsphere composite material has the synergistic characteristics of high lithium ion diffusion, high conductivity, and high stability, thereby demonstrating excellent comprehensive electrochemical performance. Summary of the Invention

[0006] The present invention proposes a method for preparing a novel hollow porous microsphere LiVO3 / C lithium-ion battery negative electrode material. The prepared LiVO3 / C microsphere composite material with a hollow porous structure is synthesized by a template method, which solves the problems of difficulty in compounding LiVO3 with carbon and difficulty in controlling the morphology. The porous structure provides a fast transport channel for lithium ion diffusion, increases the contact area between the electrode and the electrolyte, the hollow structure has good volume buffering capacity, and the carbon composite can enhance electron transport. Therefore, combining the hollow porous structure and the carbon composite can shorten the conductive path, improve the penetration of the electrolyte, and enhance the overall structural stability. This material has excellent comprehensive electrochemical properties as a lithium-ion battery negative electrode and has potential application value in lithium-ion batteries.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing a novel hollow porous microsphere LiVO3 / C lithium ion battery negative electrode material, the method comprising the following steps:

[0009] (1) Ball milling of Li3VO4 / C composite material and V2O5;

[0010] (2) The material obtained in step (1) is ultrasonically mixed with ethanol and dried to obtain LiVO3 / C precursor powder;

[0011] (3) The LiVO3 / C precursor powder obtained in step (2) is heated to 300-400°C in an air environment and calcined for 2-5 h to obtain a hollow porous microsphere LiVO3 / C composite material.

[0012] Preferably, the Li3VO4 / C composite material in step (1) is Li2CO3, V2O5, C6H 12 N4 is obtained through hydrothermal reaction, addition of carbon source, drying and calcination.

[0013] Preferably, the molar ratio of V2O5 to Li3VO4 in step (1) is (3-4): (3-5).

[0014] Preferably, in step (1), the ball milling speed is 100-150 rpm, and the ball milling time is 0.2-0.5 h.

[0015] Preferably, in step (2), the ultrasonic frequency is 40-50 KHz, and the ultrasonication time is 1-20 min.

[0016] Preferably, in step (3), the calcination temperature is 300-400°C, the heating rate is 3-10°C / min, and the calcination time is 2-5 h.

[0017] This paper prepares hollow porous LiVO3 / C microspheres using a template method. The hollow porous structure facilitates electrolyte penetration and effectively mitigates the volume effect, while the carbon coating enhances electron transport. The synergistic effect of the carbon coating and the hollow porous structure gives the LiVO3 / C microsphere composite material excellent overall electrochemical performance.

[0018] The principle behind this process is to use Li3VO4 / C microspheres as templates to directly obtain LiVO3 / C microspheres through a low-temperature solid-phase reaction. The core reaction process is: Li3VO4 + V2O5 → 3LiVO3. First, the valence state of V in Li3VO4 is +5, the same as the valence state of V in LiVO3, which facilitates the conversion of the two. Second, the microspherical morphology of Li3VO4 / C maintains a stable structure during ball milling. Ultrasonic treatment ensures thorough and uniform mixing of Li3VO4 / C and V2O5, enabling a solid-phase reaction at low temperatures, thus achieving morphological inheritance in the resulting LiVO3 / C. Furthermore, the carbon in Li3VO4 / C is already stable, improving the material's conductivity without reducing the valence state of V in the reaction raw materials, which helps to improve the purity of the reactants. Ultimately, LiVO3 / C microspheres with a porous structure and excellent conductivity are obtained, which have excellent performance for lithium-ion batteries.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The synthesis process is simple, the morphology is controllable, and the repeatability is strong;

[0021] (2) Using Li3VO4 / C and V2O5 as raw materials, the synthesis temperature is low;

[0022] (3) The prepared LiVO3 / C has a hollow porous microsphere structure, and LiVO3 and C are evenly composited;

[0023] (4) The synthesized LiVO3 / C hollow porous microspheres are conducive to electrolyte penetration, electron transport and structural stability, and have excellent performance as the negative electrode of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 XRD pattern of the sample prepared in Example 1.

[0025] Figure 2 SEM image of the sample prepared in Example 1.

[0026] Figure 3 XRD pattern of the sample prepared in Example 1.

[0027] Figure 4 SEM image of the sample prepared in Example 1.

[0028] Figure 5 The first three charge and discharge curves and cycle performance diagram of the sample prepared in Example 1: (a) the first three charge and discharge curves, (b) the cycle performance diagram.

[0029] Figure 6The first three charge and discharge curves and cycle performance diagram of the sample prepared in Example 2: (a) the first three charge and discharge curves, (b) the cycle performance diagram.

[0030] Figure 7 The first three charge and discharge curves and cycle performance diagram of the sample prepared in Example 3: (a) the first three charge and discharge curves, (b) the cycle performance diagram.

[0031] Figure 8 XRD pattern of the sample prepared in Example 4.

[0032] Figure 9 The first three charge and discharge curves and cycle performance diagram of the sample prepared in Example 4: (a) the first three charge and discharge curves, (b) the cycle performance diagram. DETAILED DESCRIPTION

[0033] Example 1

[0034] 3mmol Li2CO3, 1mmol V2O5, 5mmol C6H 12 N4 was used as raw material, dissolved in 80 mL of deionized water, stirred and mixed evenly, and heated at 120 o C for 24 h. After hydrothermal treatment, glucose with a carbon content of 10% was added, and the precursor solution was diluted to 50% and then spray-dried. Finally, the temperature was raised at a rate of 3 °C / min and 550 o C for 5 h to prepare Li3VO4 / C composite material. The XRD and SEM of the prepared material are shown in Figure 2. Figure 1 、 Figure 2 shown.

[0035] Li3VO4 / C composite material and V2O5 were used as raw materials. First, 3mmol V2O5 and 3mmol Li3VO4 / C were ball-milled at 100rpm for 0.3h to mix evenly. Then, the mixed powder material was transferred to a beaker filled with anhydrous ethanol. After ultrasonic mixing, it was placed in a drying oven. Finally, the material was dried in air at 5℃ for 10min. o C / min heating rate, 350 o C for 3 h to obtain a LiVO3 / C microsphere composite material with a hollow porous structure. The XRD and SEM of the prepared material are shown in Figure 2. Figure 3 、 Figure 4 shown.

[0036] The material was fabricated into a battery as follows: the prepared sample was mixed with acetylene black and polyvinylidene fluoride in a weight ratio of 8:1:1. The mixture was prepared using N-methylpyrrolidone as the solvent to form a slurry. The slurry was then coated onto a 10 μm-thick copper foil and dried at 60°C for 10 h. The slurry was then cut into 14 mm diameter discs and dried under vacuum at 120°C for 12 h. CR2025 cells were assembled in an argon-protected glove box using a lithium metal sheet as the counter electrode, a Celgard membrane as the separator, and a solution of LiPF₂ (1 mmol / L) dissolved in EC, DMC, and DEC (1:1:1 by volume) as the electrolyte. After 8 h of rest, the assembled cells were subjected to constant current charge and discharge tests using a CT3001 battery test system at a voltage range of 3–0.01 V and a current density of 500 mA g⁻¹. -1 .like Figure 5 The first three cycles of charge and discharge curves and cycling performance of the prepared LiVO3 / C lithium-ion battery negative electrode are shown in Figure 2. The initial charge and discharge specific capacities are 763.1 and 983.0 mAh g, respectively. -1 ( Figure 5 a) There are obvious charging and discharging platforms. After 20 cycles, the charging and discharging capacities are 532.0 and 535.1 mAh g, respectively. -1 ( Figure 5 b) exhibits excellent electrochemical performance.

[0037] Example 2

[0038] The method is the same as that of Example 1, except that different ratios of Li3VO4 / C (4mmol) and V2O5 (5mmol) are used to synthesize LiVO3 / C. The material obtained in Example 2 is made into a battery according to the method of Example 1. Figure 6 As shown in Figure 2, the initial charge and discharge specific capacities are 482.6 and 884.6 mAh g, respectively. -1 ( Figure 6 a) There are obvious charging and discharging platforms. After 20 cycles, the charging and discharging capacities are 126.6 and 128.4 mAh g, respectively. -1 ( Figure 6 b) Poor electrochemical performance.

[0039] Example 3

[0040] The method is the same as that of Example 1, except that in this example, 3 mmol of V2O5 and 3 mmol of Li3VO4 / C are not ground but directly mixed and calcined to prepare LiVO3 / C. The material obtained in Example 3 is made into a battery according to the method of Example 1. Figure 7 As shown in Figure 2, the initial charge and discharge specific capacities are 113.5 and 447.2 mAh g, respectively. -1 ( Figure 7a), after 20 cycles, the charge and discharge capacities were 43.7 and 44.0 mAh g -1 ( Figure 7 b) Poor electrochemical performance.

[0041] Example 4

[0042] 1.2 g of PVA, 7.5 mmol of LiNO₃, 2.5 mmol of NH₄VO₃, and 17.5 mmol of oxalic acid were accurately weighed according to stoichiometry and added to 15 mL of deionized water. The mixture was stirred for 12 hours to obtain a blue-green solution. The solution was then loaded into a syringe and electrostatically sprayed at 18 kV and 40°C. After spraying, the precursor material was quickly transferred to an 80°C forced-air drying oven and dried for 12 hours. The resulting Li₃VO₄ / C composite was then pre-calcined at 300°C in air for 3 hours and then calcined at 600°C in a nitrogen atmosphere for 5 hours.

[0043] Li3VO4 / C composite material and NH4VO3 were used as raw materials, added into a beaker containing anhydrous ethanol, stirred for 12 h, dried, and finally the material was placed in air at 350 o C for 1 h to obtain LiV3O8 / C composite material. The XRD pattern of the prepared material is shown in Figure 2. Figure 8 shown.

[0044] The material obtained in Example 4 was made into a battery according to the method in Example 1. Figure 9 As shown in Figure 2, the initial charge and discharge specific capacities are 518.3 and 846.7 mAh g, respectively. -1 ( Figure 9 a) There are obvious charge and discharge platforms. After 20 cycles, the charge and discharge capacities are 397.0 and 399.1 mAh g, respectively. -1 ( Figure 9 b) Poor electrochemical performance.

Claims

1. A method for preparing a hollow porous microsphere LiVO3 / C lithium ion battery negative electrode material, characterized in that: The method comprises the following steps: (1) The Li3VO4 / C composite material is mixed with V2O5 by ball milling. The Li3VO4 / C composite material is Li2CO3, V2O5, C6H 12 The Li3VO4 / C composite material was obtained by hydrothermal reaction of N4 at 120℃ for 24 h, addition of carbon source, drying and calcination. (2) The material obtained in step (1) is ultrasonically mixed with ethanol and dried to obtain LiVO3 / C precursor powder, with an ultrasonic frequency of 40-50 kHz and an ultrasonication time of 1-20 min; (3) The LiVO3 / C precursor powder obtained in step (2) is heated to 300-400°C in an air environment and calcined for 2-5 h to obtain a hollow porous microsphere LiVO3 / C composite material.

2. The method for preparing a hollow porous microsphere LiVO3 / C lithium ion battery negative electrode material according to claim 1, characterized in that: The molar ratio of V2O5 to Li3VO4 in step (1) is (3-4): (3-5).

3. The method for preparing a hollow porous microsphere LiVO3 / C lithium ion battery negative electrode material according to claim 1, characterized in that: In step (1), the ball milling speed is 100-150 rpm, and the ball milling time is 0.2-0.5 h.

4. The method for preparing a hollow porous microsphere LiVO3 / C lithium ion battery negative electrode material according to claim 1, characterized in that: In step (3), the calcination temperature is 300-400°C, the heating rate is 3-10°C / min, and the calcination time is 2-5h.

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