Carbon-coated LiVO3 / Li3VO4 lithium ion battery negative electrode material and preparation method

Abstract

The application provides a novel LiVO3-based lithium ion battery negative electrode material and a preparation method. A LiVO3-based composite material is successfully prepared by a two-step method through a hydrothermal synthesis process and subsequent calcination. The specific operation is as follows: in the first step, LiNO3, V2O5 and citric acid are dissolved in a proper amount of deionized water, stirred and mixed uniformly, and subjected to hydrothermal treatment; the precursor solution obtained after the hydrothermal treatment is dried, and finally the precursor powder obtained after the drying is calcined under air to obtain a LiVO3 / Li3VO4 material. In the second step, a proper amount of the LiVO3 / Li3VO4 material prepared in the first step is weighed, a certain proportion of a carbon source is added thereto, the mixture is uniformly mixed, and the carbon-coated LiVO3 / Li3VO4 composite material is obtained by calcination under a protective gas. The application solves the problems of unstable performance and poor conductivity of the LiVO3-based lithium ion battery negative electrode material.

Description

Technical Field

[0001] This invention relates to a lithium-ion battery anode material, and more particularly to a carbon-coated LiVO3 / Li3VO4 anode material and its preparation method, belonging to the field of electrochemical power sources. Background Technology

[0002] Energy is fundamental to human survival and development. However, the massive consumption of non-renewable energy sources such as coal, oil, and natural gas has led to a severe energy crisis and pollution problems. Vigorously developing renewable and clean energy is an effective way to solve energy and environmental issues. However, the development and use of new renewable and clean energy sources such as solar and wind power are limited by their randomness, intermittency, and geographical constraints, necessitating the development of energy storage devices with large capacity and high security. Therefore, the development of high-performance energy storage equipment is a hot research topic for scientists and technologists.

[0003] Lithium-ion batteries possess advantages such as high energy density, high operating voltage, long cycle life, low environmental pollution, no memory effect, and rapid charge / discharge capability, making them one of the most promising electrochemical energy storage devices. However, with technological advancements, higher demands are being placed on the energy density, cycle life, and environmental performance of lithium-ion batteries, and these performance indicators depend on the development of battery electrode materials. Currently, lithium-ion battery anode materials mainly focus on carbon materials, with the emerging Li4Ti5O4 being a promising candidate. 12 Si-based materials have also been increasingly used due to their high stability and high capacity. In recent years, vanadate materials have been regarded as an ideal anode material for lithium-ion batteries due to their comprehensive excellent electrochemical performance (lower operating platform, higher safety, and higher capacity), with Li3VO4 anode material being the representative.

[0004] LiVO3 is also a typical vanadate material with a monoclinic crystal structure, and was initially mainly studied as a cathode material for lithium-ion batteries. The vanadium in LiVO3 has a +5 valence, and theoretically, it can also be reduced and used as an anode material for lithium-ion batteries. Early explorations have shown that LiVO3, as an anode material for lithium-ion batteries, exhibits high initial capacity. Compared to Li3VO4 anode materials, LiVO3 contains less Li, offering significant advantages: 1) Due to the scarcity of Li resources, less Li corresponds to lower costs; 2) For the same V... 5+ → V 2+ The reduction process involves storing the same Li in both. + With a certain number of units, the theoretical capacity is higher; otherwise, it corresponds to a higher theoretical capacity. However, in practical applications, LiVO3 faces a series of challenges, such as low actual capacity and poor cycling stability.

[0005] Previous studies have shown that adjusting the size of electrode materials and combining them with additives that exhibit high conductivity or high stability can significantly improve material reaction kinetics, thereby enhancing their cycle stability. This invention attempts to synthesize carbon-coated LiVO3 / Li3VO4 composite materials, which, while fully leveraging the inherent advantages of LiVO3 materials, significantly improves their cycle performance. Summary of the Invention

[0006] This invention provides a carbon-coated LiVO3 / Li3VO4 anode material and its preparation method. A two-step method is employed to design a uniformly sized carbon-coated LiVO3 / Li3VO4 composite material. First, components that can decompose under air introduction in the precursor significantly suppress agglomeration during precursor sintering, resulting in uniformly sized LiVO3 / Li3VO4 particles through sintering. Second, a carbon-containing reducing agent is introduced, and surface coating is achieved through a low-temperature carbonization method without altering the composition of the LiVO3 / Li3VO4 particles, thus obtaining the carbon-coated LiVO3 / Li3VO4 composite material. The prepared composite material exhibits excellent overall electrochemical performance as a lithium-ion battery anode. Uniformly sized LiVO3 / Li3VO4 particles are obtained through solid-state sintering; a suitable carbon source is selected, and carbonization conditions are adjusted to obtain the carbon-coated LiVO3 / Li3VO4 composite material. The prepared carbon-coated LiVO3 / Li3VO4 composite material exhibits excellent electrochemical performance.

[0007] The synthesis of LiVO3 requires stringent conditions, typically requiring calcination in air, and pure LiVO3 exhibits unsatisfactory electrochemical performance. This invention improves the electrochemical reaction kinetics of LiVO3 anode materials by combining it with carbon and Li3VO4, thereby significantly enhancing its performance. Currently, the direct synthesis of carbon-coated LiVO3 / Li3VO4 composite materials faces challenges. Sintering under a protective gas atmosphere results in a reducing environment caused by carbonization of the carbon source, affecting the phase composition of LiVO3 and leading to its conversion into other components, making it impossible to obtain carbon-coated LiVO3 / Li3VO4 composite materials. Sintering in air, on the other hand, fails to retain carbon.

[0008] To achieve the objectives of this invention, the technical solution is as follows:

[0009] A LiVO 3 / C-type lithium-ion battery anode material and preparation method, the process including the following steps:

[0010] (1) Weigh LiNO3, V2O5 and citric acid according to the proportion and disperse them in deionized water. Stir and mix evenly, and perform hydrothermal treatment. After hydrothermal treatment, the precursor solution obtained is dried, and finally the dried precursor powder is calcined in air to obtain material A.

[0011] (2) Weigh the material A obtained in step (1), add a carbon source to it, grind and mix it evenly, and then calcine it under a protective gas to obtain carbon-coated LiVO3 / Li3VO4 composite material.

[0012] Preferably, the molar ratio of raw materials LiNO3, V2O5 and citric acid in step (1) is 2.1~2.5:1:(0.05~0.15); the hydrothermal treatment conditions are 100~140℃ for 20~30h.

[0013] Preferably, in step (1), the drying conditions are 60~100℃ for 12~24h.

[0014] Preferably, in step (1), the calcination atmosphere is air, and the calcination conditions are: a heating rate of 3~5℃ / min. -1 The calcination temperature is 250~550℃, and the calcination time is 2~5h.

[0015] Preferably, in step (2), the mass of the carbon source is 5% to 10% of the mass of material A, and the carbon source can be glucose, sucrose, polyvinyl alcohol or others.

[0016] Preferably, in step (2), the calcination atmosphere is N2, and the calcination conditions are: a heating rate of 3~5℃ / min. -1 The calcination temperature is 350~550℃ and the calcination time is 3~5h.

[0017] Preferably, the material obtained after calcination in step (2) is granular with an average size of 0.5-0.1 micrometers.

[0018] The principle of this invention is as follows:

[0019] In the first step, carbon-containing polymer materials can effectively suppress agglomeration during precursor sintering, thereby obtaining smaller sizes; carbon-containing polymers can be completely decomposed during air sintering without leaving any impurities; during air sintering, both LiVO3 and Li3VO4 can exist stably, with LiVO3 forming at a lower temperature and preferentially forming as the main phase, while Li3VO4 forming at a higher temperature is the auxiliary phase, distributed around LiVO3.

[0020] In the second step, the carbon source is uniformly mixed with LiVO3 / Li3VO4 particles and preferentially distributed around the Li3VO4 particles. During sintering, the carbon source carbonizes along the surface of Li3VO4, while Li3VO4 can maintain phase stability under carbonization, thereby protecting the LiVO3 main phase, and finally obtaining a carbon-coated LiVO3 / Li3VO4 composite material.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The carbon-coated LiVO3 / Li3VO4 composite material involved in this invention, as a negative electrode material for lithium-ion batteries, has the following significant characteristics:

[0023] (1) The synthesis process is stable and highly reproducible;

[0024] (2) In the carbon-coated LiVO3 / Li3VO4 composite material prepared, LiVO3 is the main phase and Li3VO4 is the auxiliary phase. It does not contain other vanadate impurities and LiVO3 / Li3VO4 is coated with carbon.

[0025] (3) The carbon-coated LiVO3 / Li3VO4 composite material prepared is a uniform particle with an average size of about 1 micrometer;

[0026] (4) The carbon-coated LiVO3 / Li3VO4 composite material prepared can be used as a negative electrode for lithium-ion batteries, showing excellent cycle performance. Attached Figure Description

[0027] Figure 1 XRD pattern of the sample prepared by one-time sintering in Example 1.

[0028] Figure 2 XRD pattern of the sample prepared by secondary sintering in Example 1.

[0029] Figure 3 SEM image of the sample prepared in Example 1.

[0030] Figure 4 (a) Initial charge-discharge curves and (b) Cyclic performance curves of the sample prepared in Example 1.

[0031] Figure 5 XRD pattern of the sample prepared in Example 2.

[0032] Figure 6 (a) Initial charge-discharge curves and (b) Cyclic performance curves of the sample prepared in Example 2.

[0033] Figure 7 XRD pattern of the sample prepared in Example 3.

[0034] Figure 8 XRD pattern of the sample prepared in Example 4.

[0035] Figure 9 (a) Initial charge-discharge curves and (b) Cyclic performance curves of the sample prepared in Example 4.

[0036] Figure 10 XRD pattern of the sample prepared in Example 5.

[0037] Figure 11XRD pattern of the sample prepared in Example 6. Detailed Implementation

[0038] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited to the scope described in the embodiments.

[0039] Example 1

[0040] Using 4.5 mmol LiNO3, 2 mmol V2O5, and 0.04 g citric acid as raw materials, the raw materials were dissolved in 40 mL of deionized water. After stirring and mixing thoroughly, the mixture was hydrothermally heated at 120 °C for 24 h to obtain a homogeneous solution. The solution was dried and calcined at 500 °C for 3 h under air at a heating rate of 5 °C / min to obtain a grayish-white powder sample. XRD (e.g., [missing information]) was then analyzed. Figure 1 (As shown) Tests revealed that the obtained sample was LiVO3 / Li3VO4. An appropriate amount of the prepared LiVO3 / Li3VO4 was weighed, and then 10% glucose (by mass) was added and ground in a mortar. The uniformly ground sample was calcined at 450℃ for 5 hours in a N2 atmosphere with a heating rate of 5℃ / min, finally obtaining a powder sample, which was then analyzed by XRD (…). Figure 2 The sample is LiVO3 / Li3VO4@C. SEM images of the prepared sample are shown below. Figure 3 As shown, they are granular with an average size of about 1 micrometer.

[0041] The materials were 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, and an N-methylpyrrolidone solvent was used to prepare a slurry. This slurry was coated onto a 10 μm thick copper foil, dried at 60 °C for 10 h, and then cut into 14 mm diameter discs. These discs were then vacuum dried at 120 °C for 12 h. A lithium metal sheet was used as the counter electrode, a Celgard membrane as the separator, and a solution of EC+DMC+DEC (volume ratio 1:1:1) containing 1 mmol / L LiPF6 was used as the electrolyte. The batteries were assembled into CR2025 type batteries in an argon-protected glove box. After assembly, the batteries were allowed to stand for 8 h, and then constant current charge-discharge tests were performed using a CT2001 battery testing system. The test voltage was 3–0.01 V, and the current density was 200 mA g. -1 .like Figure 4 The initial charge-discharge curves and cycle performance of the carbon-coated LiVO3 / Li3VO4 composite material used as the anode in a lithium-ion battery are shown. The initial charge-discharge specific capacities are 537.2 and 660.9 mAh g, respectively. -1 It exhibits a clear charge and discharge plateau, with charge and discharge capacities of 476.4 and 478.5 mAh g after 100 cycles, respectively. -1 It exhibits good electrochemical performance.

[0042] Example 2

[0043] 4 mmol LiNO3, 2 mmol V2O5, and 0.04 g citric acid were dispersed in 40 mL of deionized water and mixed thoroughly. The mixture was then hydrothermally treated at 120 °C for 24 h to obtain a homogeneous solution. The solution was dried and calcined in air at 500 °C for 5 h at a heating rate of 5 °C / min, finally yielding a white powder, which is LiVO3 (XRD value as shown). Figure 5 (As shown). The material obtained in Example 2 was used to make a battery according to the method in Example 1. Figure 6 As shown, the initial charge and discharge specific capacities are 481.0 and 640.6 mAh g, respectively. -1 After 100 cycles, the charge and discharge capacities were 266.2 and 267.9 mAh g, respectively. -1 The electrochemical performance was unsatisfactory. The results indicate that pure LiVO3 exhibits unsatisfactory performance.

[0044] Example 3

[0045] Weigh an appropriate amount of the LiVO3 sample obtained in Example 2, then add 10% glucose by mass and grind it in a mortar. The uniformly ground sample is calcined at 450°C for 5 hours in a N2 atmosphere with a heating rate of 5°C / min, finally obtaining a gray powder sample, which is then analyzed by XRD. Figure 7 The main phase of the sample was Li3VO4 / LiV2O5. The results showed that pure LiVO3 reacted chemically with the carbon source during sintering in a protective gas environment, generating new components. This confirms that LiVO3 cannot remain stable during carbonization of the carbon source, and also that carbon is consumed due to the reduction of LiVO3, which is detrimental to surface coating. In conclusion, direct in-situ carbonization of the carbon source onto the LiVO3 surface for carbon coating is difficult to achieve.

[0046] Example 4

[0047] Using 4.5 mmol LiNO3, 2 mmol V2O5, and 0.04 g citric acid as raw materials, the raw materials were dissolved in 40 mL of deionized water. After stirring and mixing thoroughly, the mixture was hydrothermally heated at 120 °C for 24 h to obtain a homogeneous solution. The solution was dried and calcined at 500 °C for 3 h under N2 at a heating rate of 5 °C / min to obtain a black powder sample. XRD analysis was performed... Figure 8 The test revealed that the obtained sample was LiVO3 / Li3VO4 / LiV2O5. The material obtained in Example 4 was used to fabricate a battery according to the method in Example 1. Figure 9 As shown, the initial charge and discharge specific capacities are 408.0 and 326.6 mAh g, respectively. -1After 100 cycles, the charge and discharge capacities were 282.5 and 281.1 mAh g, respectively. -1 The electrochemical performance was unsatisfactory. The results showed that carbon-coated LiVO3 / Li3VO4 composites could not be obtained by sintering directly with a carbon source under a protective gas atmosphere. Due to the low activity of LiV2O5, the prepared LiVO3 / Li3VO4 / LiV2O5 had low capacity.

[0048] Example 5

[0049] Using 4.5 mmol LiOH, 2 mmol V₂O₅, and 0.04 g citric acid as raw materials, the raw materials were dissolved in 40 mL of deionized water. After stirring and mixing thoroughly, the mixture was hydrothermally heated at 120 °C for 24 h to obtain a homogeneous solution. The solution was dried and calcined at 500 °C for 3 h under air at a heating rate of 5 °C / min to obtain a grayish-white powder sample. XRD analysis was performed... Figure 10 The tests revealed that the obtained sample was LiVO3 / Li3VO4, but the main diffraction peaks corresponded better with Li3VO4, indicating that Li3VO4 was the dominant component. The results show that the choice of Li source has a certain influence on the composition of the product under air calcination.

[0050] Example 6

[0051] LiVO3 / Li3VO4 samples were prepared according to the method described in Example 1. An appropriate amount of the prepared LiVO3 / Li3VO4 was weighed, and then 10% polyvinyl alcohol (polyvinyl alcohol by mass) was added and ground in a mortar. The uniformly ground sample was calcined at 450°C for 5 hours in a N2 atmosphere with a heating rate of 5°C / min, finally yielding a black powder sample, indicating the presence of carbon. XRD analysis confirmed the presence of carbon. Figure 11 The sample diffraction peaks correspond to LiVO3 / Li3VO4. The results indicate that carbon-coated LiVO3 / Li3VO4 composite materials were successfully prepared.

[0052] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in this application can be arbitrarily combined with each other without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-coated LiVO3 / Li3VO4 lithium-ion battery anode material, characterized in that: The method includes the following steps: (1) Weigh LiNO3, V2O5 and citric acid according to the proportion and disperse them in deionized water. Stir and mix evenly, and perform hydrothermal treatment. After hydrothermal treatment, the precursor solution obtained is dried. Finally, the dried precursor powder is calcined in air at 250~550℃ to obtain material A. The molar ratio of LiNO3, V2O5 and citric acid is (2.1~2.5):1:(0.05~0.15), and the calcination atmosphere is air. (2) Weigh the material A obtained in step (1), then add a carbon source to it, grind and mix it evenly, and calcine it at 350~550℃ under protective gas N2 to obtain carbon-coated LiVO3 / Li3VO4 composite material.

2. The method for preparing the carbon-coated LiVO3 / Li3VO4 lithium-ion battery anode material according to claim 1, characterized in that: The hydrothermal treatment conditions in step (1) are 100~140℃ for 5~30h.

3. The method for preparing the carbon-coated LiVO3 / Li3VO4 lithium-ion battery anode material according to claim 1, characterized in that: In step (1), the drying conditions are 60~100℃ for 12~24h.

4. The method for preparing the carbon-coated LiVO3 / Li3VO4 lithium-ion battery anode material according to claim 1, characterized in that: In step (1), the calcination conditions are: a heating rate of 3~5℃ / min. -1 The calcination time is 2-5 hours.

5. The method for preparing the carbon-coated LiVO3 / Li3VO4 lithium-ion battery anode material according to claim 1, characterized in that: In step (2), the mass of the carbon source is 5% to 10% of the calcined powder material, and the carbon source is glucose, sucrose, polyvinyl alcohol or others.

6. The method for preparing the carbon-coated LiVO3 / Li3VO4 lithium-ion battery anode material according to claim 1, characterized in that: In step (2), the calcination conditions are: a heating rate of 3~5℃ / min. -1 The calcination time is 3-5 hours.

7. The method for preparing the carbon-coated LiVO3 / Li3VO4 lithium-ion battery anode material according to claim 1, characterized in that: The material obtained after calcination in step (2) is granular with an average size of 0.5-0.1 micrometers.

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