A high-performance lithium ion battery lithium-rich manganese-based positive electrode material and a self-assembly preparation method thereof

Abstract

The application discloses a self-assembly preparation method of a high-performance lithium ion battery lithium-rich manganese-based positive electrode material, and comprises the following steps: Q1, preparing a precursor by a sol-gel method; Q2, calcining the precursor: the precursor is kept at 400-600 DEG C for 3-6h under a certain atmosphere, is ground, is slowly heated to 600-1000 DEG C, is not subjected to constant temperature heating treatment, is slowly cooled immediately after, and the precursor calcined powder is obtained; Q3, self-assembly of nanoparticles: the precursor calcined powder in the above step is dispersed into a water-organic solvent (volume ratio 1:1) mixed solution, is reacted in a hydrothermal reaction kettle at 100-200 DEG C for 3-10h, is centrifuged, washed, dried, high-temperature sintered, and the self-assembly product, i.e., the high-performance lithium ion battery lithium-rich manganese-based positive electrode material, is obtained. The self-assembly preparation method of the application accords with the green chemistry concept, the process is simple, the obtained lithium-rich manganese-based positive electrode material has high purity, and has the advantages of high first charge-discharge efficiency, excellent cycle performance and the like.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage and new energy materials technology, specifically to a high-performance lithium-ion battery lithium-rich manganese-based cathode material and its self-assembly preparation method. Background Technology

[0002] As a novel type of rechargeable energy storage battery, lithium-ion batteries have been extensively studied due to their advantages such as high voltage, high energy density, operational safety, and lack of memory effect, and have been widely used in various portable electronic devices and the electric vehicle industry. With the increasing prevalence of lithium-ion batteries, there are higher demands on their performance, particularly their long-cycle performance, energy density, and operating voltage. However, the key to achieving high-performance lithium-ion batteries lies in the research and development of high-performance lithium-ion battery cathode materials.

[0003] According to the State Council's "Made in China 2025" national strategic plan to strengthen high-end manufacturing, the specific energy of new power batteries is required to reach 400Wh / kg by 2025. However, the actual specific capacity of commercially available cathode materials (such as layered LiCoO2, spinel LiMn2O4, olivine LiFePO4, and ternary materials) is relatively low (<200mAh / g), limiting battery development. Lithium-rich manganese-based cathode materials, such as xLi2MnO3·(1-x)LiMO2 (M = Ni, Mn, Co, etc.), are considered to be a cathode material with great development potential due to their high reversible specific capacity (>250mAh / g), high energy density (~1000Wh / kg), and low cost. However, the commercialization of lithium-rich manganese-based cathode materials requires solving major problems such as high initial irreversible capacity, poor cycle stability, severe voltage decay, and poor rate performance. To address these issues, researchers have conducted extensive studies, primarily focusing on optimizing material preparation processes, bulk element doping, and surface modification.

[0004] Bao et al. successfully prepared Li₂ with a surface spinel phase heterostructure by reducing the amount of lithium used and employing the sol-gel method and subsequent annealing process. 1.14 Mn 0.54 Ni 0.13 Co 0.13 The O2 material, after modification, showed an improved initial discharge specific capacity, with the discharge specific capacity at 0.1C increasing from 280.3 mAh g⁻¹. -1 Increased to 303.0 mAh g -1 After 100 cycles at 1C, the capacity retention increased from 78.8% to 83.7%, indicating that the improvement in the cycling stability of the material was not significant. Zheng et al. successfully prepared Li[Li] with a small amount of F substituting for O using NH4F as the fluorine source via the sol-gel method. 0.2 Mn0.54 Ni 0.13 Co 0.13 ]O 1.95 F 0.05 After 50 cycles at 0.2C, the capacity retention of the material increased from 72.4% to 88.1%, showing a significant improvement in cycle performance. However, the initial discharge specific capacity at 0.2C was only 227 mAh g⁻¹. -1 In summary, without significantly affecting other properties of the material, the electrochemical cycling performance of lithium-rich manganese-based cathode materials still has considerable room for improvement.

[0005] Poor cycle stability significantly hinders the application and industrialization of lithium-rich layered oxide cathodes in high-energy-density lithium-ion batteries. The structure of a material determines its performance, and this structure is greatly influenced by the material preparation process. Among these, sintering temperature and time have a significant impact on both structure and performance. Traditional sintering regimes primarily involve isothermal calcination at a specific temperature for a given sintering time. However, conventional lithium-rich manganese-based cathode materials synthesized using this sintering regime generally exhibit poor electrochemical performance, especially in terms of cycle performance. Therefore, controlling the sintering regime to improve structural stability during cycling is a crucial issue for achieving high-performance lithium-rich manganese-based cathode materials. Furthermore, achieving the self-assembly of nanomaterials is an important pathway to meeting the commercialization requirements of nanoelectrode materials.

[0006] Based on the above, this invention proposes a self-assembly preparation method for high-performance lithium-ion battery lithium-rich manganese-based cathode materials, which can effectively solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a high-performance lithium-ion battery lithium-rich manganese-based cathode material and its self-assembly preparation method. The self-assembly preparation method of the high-performance lithium-ion battery lithium-rich manganese-based cathode material of this invention conforms to the concept of green chemistry, has a simple process, and yields a high-purity lithium-rich manganese-based cathode material with advantages such as high initial charge-discharge efficiency and excellent cycle performance.

[0008] To solve the above technical problems, the technical solution provided by the present invention is as follows:

[0009] A self-assembly preparation method for a high-performance lithium-ion battery lithium-rich manganese-based cathode material includes the following steps:

[0010] Q1. Preparation of precursor by sol-gel method: Nickel source, manganese source, cobalt source and lithium source are dissolved in water to obtain a mixed metal salt solution. Then the mixed metal salt solution is slowly added dropwise to an organic acid solution. The pH of the system is adjusted by ammonia water. After water bath heating, evaporation, drying and pulverization, the precursor is obtained.

[0011] Q2. Calcination of precursor: The precursor is kept at 400-600℃ for 3-6 hours under a certain atmosphere, then ground and slowly heated to 600-1000℃ without constant temperature heating treatment, and then immediately and slowly cooled to obtain calcined precursor powder.

[0012] Q3. Nanoparticle self-assembly: The calcined precursor powder from the previous step is dispersed in a water-organic solvent (volume ratio of 1:1) mixed solution and reacted in a hydrothermal reactor at 100-200℃ for 3-10 hours. After centrifugation, washing, drying, and high-temperature sintering, the self-assembled product is obtained, which is the high-performance lithium-ion battery lithium-rich manganese-based cathode material.

[0013] This invention is a self-assembly preparation method for high-performance lithium-ion battery lithium-rich manganese-based cathode materials based on a variable-temperature sintering process. It breaks away from the conventional high-temperature isothermal sintering method and has the advantages of simple preparation method, green and environmentally friendly, high product purity, and stable structure of the obtained material. It also obtains nanoscale cathode material particles, which exhibit high initial coulombic efficiency and discharge specific capacity, excellent cycle performance and high energy density retention. Through hydrothermal method, the self-assembly of nanoscale cathode material particles is successfully realized, which makes its commercialization possible.

[0014] According to the above technical solution, as a further preferred technical solution, in step Q1, the nickel source is any one or a mixture of two or more of nickel acetate, nickel hydroxide, nickel chloride and nickel sulfate.

[0015] According to the above technical solution, as a further preferred technical solution, in step Q1, the manganese source is any one or a mixture of two or more of manganese chloride, manganese acetate and manganese sulfate.

[0016] According to the above technical solution, as a further preferred technical solution, in step Q1, the cobalt source is any one or a mixture of two or more of cobalt chloride, cobalt acetate, cobalt nitrate and cobalt sulfate.

[0017] According to the above technical solution, as a further preferred technical solution, in step Q1, the lithium source is any one or a mixture of two or more of lithium acetate, lithium hydroxide, lithium nitrate and lithium sulfate.

[0018] According to the above technical solution, as a further preferred technical solution, in step Q1, the organic acid is any one or a mixture of two or more of citric acid, tartaric acid and oxalic acid; after the mixed metal salt solution is slowly added dropwise to the organic acid solution, the molar ratio of the organic acid to the metal ions is 1:1.

[0019] According to the above technical solution, as a further preferred technical solution, in step Q1, the pH value is 6-10, the water bath heating temperature is 60-100℃, the water bath heating time is 8-14h, and the drying temperature is 90-120℃.

[0020] According to the above technical solution, as a further preferred technical solution, in step Q2, the certain atmosphere is either an oxygen atmosphere or an air atmosphere; the heating rate of the slow heating is 0-3℃ / min; and the cooling rate of the slow cooling is 0-3℃ / min.

[0021] According to the above technical solution, as a further preferred technical solution, in step Q3, the organic solvent is any one or a mixture of two or more of ethanol, ethylene glycol and glycerol.

[0022] This invention also provides a high-performance lithium-ion battery lithium-rich manganese-based cathode material, which is prepared by the self-assembly preparation method of the high-performance lithium-ion battery lithium-rich manganese-based cathode material as described above.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] The sintering method provided by this invention utilizes the red-hot state of transition metal oxide materials in the high-temperature range, where ion interdiffusion is relatively rapid. This facilitates the contact, reaction, nucleation, and growth of material particles, reducing the adverse effects of specific sintering temperatures on particle reaction and shaping in conventional high-temperature heat treatment processes. Combined with the prior sol-gel method, it can efficiently obtain structurally stable and high-performance cathode materials. Therefore, the self-assembly preparation method of high (cycle-ready) performance lithium-ion battery lithium-rich manganese-based cathode materials of this invention is both environmentally friendly and green, effectively yielding lithium-rich manganese-based cathode materials with advantages such as high product purity, nanoscale particles, good structural stability, minimal cation mixing, good electrochemical reversibility, high reversible specific capacity, good cycle performance, and high energy density retention. Furthermore, the hydrothermal self-assembly method of this invention successfully achieves the growth of nanoscale material particles, and the assembled material still maintains good electrochemical performance, which provides a possibility for the commercialization of nanoscale materials. Attached Figure Description

[0025] Figure 1 Li, a high-performance lithium-ion battery lithium-rich manganese-based cathode material prepared in Example 1 1.2 Mn 0.54 Ni 0.13 Co 0.13 SEM surface morphology of O2;

[0026] Figure 2Li, a high-performance lithium-ion battery lithium-rich manganese-based cathode material prepared in Example 1 1.2 Mn 0.54 Ni 0.13 Co 0.13 XRD pattern of O2;

[0027] Figure 3 Li, a high-performance lithium-ion battery lithium-rich manganese-based cathode material prepared in Example 2 1.2 Mn 0.54 Ni 0.13 Co 0.13 The first-week charge-discharge curve of an experimental lithium-ion battery made of O2.

[0028] Figure 4 Li, a high-performance lithium-ion battery lithium-rich manganese-based cathode material prepared in Example 1 1.2 Mn 0.54 Ni 0.13 Co 0.13 Linear cyclic voltammogram of an experimental lithium-ion battery made of O2;

[0029] Figure 5 The high-performance lithium-ion battery lithium-rich manganese-based cathode material Li prepared in Example 3 1.2 Mn 0.54 Ni 0.13 Co 0.13 Cycle performance curves of experimental lithium-ion batteries made with O2. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples, but these should not be construed as limiting the present patent.

[0031] Unless otherwise specified, the test methods or experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.

[0032] Example 1

[0033] A high-performance lithium-ion battery lithium-rich manganese-based cathode material and its self-assembly preparation method include the following steps:

[0034] According to Li 1.2 Mn 0.54 Ni 0.13 Co 0.13The stoichiometric ratio represented by O2 is used to obtain a mixed metal salt solution by dissolving nickel acetate, manganese acetate, cobalt nitrate, and lithium hydroxide in water. This solution is then slowly added dropwise to a citric acid solution, with a molar ratio of citric acid to metal ions of 1:1. The pH of the system is adjusted to 8 using ammonia. The mixture is heated in an 80°C water bath for 9 hours until evaporated to dryness, then dried at 100°C and pulverized to obtain a precursor. The precursor obtained in the previous step is calcined at 500°C for 4 hours in an oxygen atmosphere, ground, and then slowly heated to 950°C at a rate of 1°C / min without constant temperature heating. It is then immediately cooled slowly at a rate of 0.5°C / min to obtain the product. Figure 1 The image shown is an SEM image of the surface morphology of this material.

[0035] Example 2

[0036] A high-performance lithium-ion battery lithium-rich manganese-based cathode material and its self-assembly preparation method include the following steps:

[0037] The precursor from Example 1 was calcined at 500°C for 4 hours in air. After grinding, the temperature was slowly increased to 900°C at a rate of 0.5°C / min without isothermal heating. It was then immediately cooled slowly at a rate of 0.5°C / min to obtain the product. Figure 2 The image shown is the XRD pattern of this material.

[0038] Example 3

[0039] A high-performance lithium-ion battery lithium-rich manganese-based cathode material and its self-assembly preparation method include the following steps:

[0040] The precursor from Example 1 was calcined at 450°C for 6 hours in an oxygen atmosphere, then ground, and slowly heated to 850°C at a rate of 0.5°C / min without isothermal heating. It was then immediately cooled slowly at a rate of 1.0°C / min to obtain the product. Figure 3 The figure shown is the initial charge-discharge curve of this material.

[0041] Example 4

[0042] A high-performance lithium-ion battery lithium-rich manganese-based cathode material and its self-assembly preparation method include the following steps:

[0043] The powder obtained from grinding in Example 1 was dispersed in a water-ethanol mixture with a water-ethanol volume ratio of 1:1. The mixture was reacted at 160°C for 5 hours in a hydrothermal reactor. After centrifugation, washing, drying, and high-temperature calcination, a self-assembled product was obtained, showing significant particle growth. Figure 4 The image shown is an SEM image of the surface morphology of this material.

[0044] Test case

[0045] The product obtained in Example 1 was mixed with conductive agent Super P and binder PVDF at a mass ratio of 8:1:1. A certain amount of 1-methyl-2-pyrrolidone (NMP) was added and stirred on a magnetic stirrer for 4 hours to form a paste. This paste was then coated onto aluminum foil and dried in a vacuum drying oven at 100°C for 12 hours. The uniformly coated portion was cut into 12mm diameter discs from the aluminum foil to serve as working electrodes. These discs were then dried in a vacuum drying oven at 100°C for 12 hours and transferred to an argon glove box for assembly. A lithium metal sheet was used as the negative electrode, a PP three-layer microporous membrane as the separator, and a 1mol / L LiPF6 / EC:DEC = 1:1 (volume ratio) solution as the electrolyte. The assembled battery was allowed to stand for 7 hours before testing. At room temperature, the battery was subjected to constant current charge-discharge testing using a Land testing system. The voltage range was 2.0-4.7V. The battery underwent four pre-cycles at a current density of 20mA / g, followed by long-cycle testing at a current density of 200mA / g. The result of discharge specific capacity minus cycle number is as follows: Figure 5 As shown, the prepared material retains a capacity of 186.5 mAh / g after 100 cycles under the test conditions, with a capacity retention rate as high as 90.6%, demonstrating excellent cycle life characteristics.

[0046] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A self-assembly preparation method for a high-performance lithium-ion battery lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: Q1. Preparation of precursor by sol-gel method: Nickel source, manganese source, cobalt source and lithium source are dissolved in water to obtain a mixed metal salt solution. Then the mixed metal salt solution is slowly added dropwise to an organic acid solution. The pH of the system is adjusted by ammonia water. After water bath heating, evaporation, drying and pulverization, the precursor is obtained. Q2. Precursor calcination: The precursor is kept at 400-600℃ for 3-6 hours under a certain atmosphere, then ground and slowly heated to 600-1000℃ without isothermal heating treatment, followed by immediate and slow cooling to obtain the calcined precursor powder; in step Q2, the certain atmosphere is either an oxygen atmosphere or an air atmosphere; the heating rate of the slow heating is 0-3℃ / min; the cooling rate of the slow cooling is 0-3℃ / min. Q3. Nanoparticle self-assembly: The calcined precursor powder from the previous step is dispersed in a water-organic solvent mixture, wherein the volume ratio of water to organic solvent is 1:

1. The mixture is reacted in a hydrothermal reactor at 100-200℃ for 3-10 hours. After centrifugation, washing, drying, and high-temperature sintering, the self-assembled product, namely the high-performance lithium-ion battery lithium-rich manganese-based cathode material, is obtained.

2. The self-assembly preparation method of the high-performance lithium-ion battery lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step Q1, the nickel source is any one or a mixture of two or more of nickel acetate, nickel hydroxide, nickel chloride, and nickel sulfate.

3. The self-assembly preparation method of the high-performance lithium-ion battery lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step Q1, the manganese source is any one or a mixture of two or more of manganese chloride, manganese acetate, and manganese sulfate.

4. The self-assembly preparation method of the high-performance lithium-ion battery lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step Q1, the cobalt source is any one or a mixture of two or more of cobalt chloride, cobalt acetate, cobalt nitrate, and cobalt sulfate.

5. The self-assembly preparation method of the high-performance lithium-ion battery lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step Q1, the lithium source is any one or a mixture of two or more of lithium acetate, lithium hydroxide, lithium nitrate and lithium sulfate.

6. The self-assembly preparation method of the high-performance lithium-ion battery lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step Q1, the organic acid is any one or a mixture of two or more of citric acid, tartaric acid, and oxalic acid; after the mixed metal salt solution is slowly added dropwise to the organic acid solution, the molar ratio of the organic acid to the metal ions is 1:

1.

7. The self-assembly preparation method of the high-performance lithium-ion battery lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step Q1, the pH value is 6-10, the water bath heating temperature is 60-100℃, the water bath heating time is 8-14h, and the drying temperature is 90-120℃.

8. The self-assembly preparation method of the high-performance lithium-ion battery lithium-rich manganese-based cathode material according to claim 1, characterized in that, In step Q3, the organic solvent is any one or a mixture of two or more of ethanol, ethylene glycol, and glycerol.

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