Lithium battery positive electrode material, preparation method and application thereof

Abstract

The application relates to the technical field of lithium battery positive electrode materials, and particularly discloses a lithium battery positive electrode material, a preparation method and application thereof. The preparation method comprises the following steps: weighing positive electrode active material precursors, a molten medium and a dopant in a glove box, grinding and mixing, primary sintering, secondary sintering, and obtaining the lithium battery positive electrode material; wherein the temperature of the primary sintering is lower than that of the secondary sintering, and the molten medium is a compound in a molten state in the primary sintering process. In the primary sintering process at a lower temperature, the molten medium melts to form a uniform dispersion system, so that the positive electrode material precursors and the dopant are dispersed or dissolved in the melt, and then high-temperature crystallization is carried out in the secondary sintering process at a higher temperature. Since the doping elements are uniformly distributed in advance, the doping elements can be uniformly solid-solved in the process of lattice growth of the positive electrode active material, so that the high-performance lithium battery positive electrode material is efficiently and conveniently prepared.

Description

Technical Field

[0001] This invention relates to the field of lithium battery cathode material technology, and in particular to a lithium battery cathode material, its preparation method, and its application. Background Technology

[0002] Traditional lithium manganese oxide cathode materials, due to their unique Jahn-Teller effect and Mn 3+ disproportionation dissolution reaction (Mn) 3+ →Mn 4+ +Mn 2+ The irreversible phase transition (from cubic to tetragonal phase) during cycling leads to severe capacity decay and short cycle life in lithium-ion batteries, especially under high voltage or high temperature conditions. Other cathode materials (such as layered materials) are also prone to irreversible phase transitions, easily causing a decrease in battery capacity. One way to solve these problems is to dope with multiple elements, utilizing the high entropy effect to improve the stability of the material. Different elements play different roles in electrode materials, and their effects on the performance of the electrode material also vary. For example, in layered ternary cathode materials, the core role of Ni is to provide reversible capacity; the higher the content, the higher the specific capacity. The core role of Co is to suppress cation mixing and improve electronic conductivity. The role of Mn is to stabilize the structure and improve thermal safety. However, due to the complexity of the composition, multi-element doping is prone to problems of component inhomogeneity and poor consistency during the preparation process. Therefore, how to improve the consistency and uniformity of multi-element cathode materials is a key issue in the preparation.

[0003] To address the aforementioned issues, the main methods for preparing cathode materials currently used in the industry include: Solid-state reaction method: Doping elements are introduced into the lattice of electrode materials through a high-temperature solid-state method. For example, manganese source, lithium source and dopant (such as lithium fluoride, alumina) are mechanically mixed and then calcined at above 800°C for a long time.

[0004] Conventional liquid-phase methods, such as co-precipitation, first involve uniformly precipitating transition metal elements like Mn, Co, and Ni through co-precipitation, and then preparing the cathode material through a high-temperature solid-state reaction with a lithium source. This method can achieve atomic-level mixing.

[0005] However, solid-phase methods rely on solid-state diffusion, making it difficult for elements to be uniformly distributed at the atomic / molecular scale. This easily leads to regions with excessively high or low concentrations, resulting in unsatisfactory modification effects. Liquid-phase methods are time-consuming, inefficient, and have a limited range of applicability, making it difficult to achieve doping of certain metal elements. Summary of the Invention

[0006] Based on this, the purpose of this invention is to provide a lithium battery cathode material, its preparation method, and its application. By utilizing a low-melting-point melting medium to form a molten liquid phase at a lower temperature, dopant ions are rapidly and uniformly diffused into the reactants, achieving atomic-level uniform doping in the subsequent crystallization process, thereby efficiently and conveniently preparing a high-performance cathode material.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a lithium battery cathode material, comprising the following steps: weighing a cathode active material precursor, a molten medium, and a dopant in a glove box and then grinding and mixing them; sintering once and then sintering a second time to obtain the lithium battery cathode material; wherein the temperature of the first sintering is lower than the temperature of the second sintering, and the molten medium is a compound that is in a molten state during the first sintering process.

[0008] This invention selects a molten medium with a low eutectic point as the reaction medium. During the first sintering process at a lower temperature, the molten medium melts to form a uniform dispersion system, allowing the cathode material precursor and dopant to disperse or dissolve in the melt, achieving full contact and mixing of the reactants at the ionic scale. Subsequently, high-temperature crystallization is carried out during the second sintering process at a higher temperature. Since the dopant elements are pre-uniformly distributed, they can be uniformly dissolved into the cathode active material during the lattice growth process, achieving atomic-level uniform doping, thereby efficiently and conveniently preparing high-performance lithium battery cathode materials.

[0009] As a further improvement to the above-described scheme of the present invention, the metal halide is selected from at least one of lithium fluoride, lithium chloride, aluminum chloride, manganese chloride, aluminum fluoride, and nickel chloride.

[0010] As a further improvement to the above-mentioned solution of the present invention, the temperature of the first sintering is 300~600℃.

[0011] As a further improvement to the above-mentioned solution of the present invention, the temperature of the secondary sintering is 700~1000℃.

[0012] As a further improvement to the above-mentioned scheme of the present invention, the positive electrode active material precursor includes a lithium source and a manganese source, and the dopant is selected from at least one of titanium dioxide, iron trifluoride, zirconium dioxide, and aluminum fluoride.

[0013] As a further improvement to the above-mentioned scheme of the present invention, the positive electrode active material precursor includes a lithium source and a cobalt source, and the dopant is selected from at least one of sodium carbonate, aluminum fluoride, and zirconium dioxide.

[0014] The present invention also provides a lithium battery cathode material, which is prepared by the preparation method described above.

[0015] As a further improvement to the above-described solution of the present invention, the structural formula of the lithium battery cathode material is LiM. x Mn 2- x O 4-y Y y M is selected from Ti 4+ Fe 3+ Zr 4+ Mg 2+ Al 3+ Na + At least one of them, Y is selected from F - ,Br - Cl - At least one of the following, 0.12≤x≤0.25, 0≤y<0.1.

[0016] As a further improvement to the above-described solution of the present invention, the structural formula of the lithium battery cathode material is LiX. a Co 1-a O2, where X is Mn 2+ Ni 2+ Zr 4+ Mg 2+ Al 3+ Na + At least one of them, 0.06≤a≤0.94.

[0017] The present invention also provides an application of the lithium battery cathode material prepared by the preparation method described above in lithium batteries.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention selects a molten medium with a low eutectic point as the reaction medium. During the first sintering process at a lower temperature, the molten medium melts to form a uniform dispersion system, allowing the cathode material precursor and dopant to disperse or dissolve in the melt, achieving full contact and mixing of the reactants at the ionic scale. Subsequently, high-temperature crystallization is carried out during the second sintering process at a higher temperature. Since the dopant elements are pre-uniformly distributed, they can be uniformly dissolved into the cathode active material during the lattice growth process, achieving atomic-level uniform doping, thereby efficiently and conveniently preparing high-performance lithium battery cathode materials. Attached Figure Description

[0019] Figure 1 This is a SEM image of the lithium battery cathode material prepared in Example 1 of the present invention; Figure 2 The image shows the XRD pattern of the lithium battery cathode material prepared in Example 1 of this invention. Figure 3 Charge-discharge curves of the lithium battery cathode materials in Example 1 and the comparative example; Figure 4 The cycling performance diagrams are for the lithium battery cathode materials of Example 1 and the comparative example. Figure 5 The graph shows the charge / discharge rate performance of the lithium battery cathode material in Example 1 and the comparative example. Detailed Implementation

[0020] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0022] Example 1 This embodiment provides a lithium battery cathode material, LiTi. 0.05 Fe 0.03 Zr 0.03 Mn 1.89 O 3.91 F 0.09 Its preparation method includes the following steps: In a glove box under argon atmosphere and with water and oxygen content both less than 0.1 ppm, lithium chloride (LiCl), titanium dioxide (TiO2), ferric trifluoride (FeF3), zirconium dioxide (ZrO2), and manganese chloride (MnCl2) in a molar ratio of 1.05:0.05:0.03:0.03:1.89 were placed in a mortar and manually ground for 20 min until uniformly mixed and free of particles. The mixture was then transferred to an alumina crucible. The alumina crucible was placed in a tube furnace and heated to 550 °C at a rate of 5 °C / min under air atmosphere and held for 12 h. The resulting powder was then heated to 800 °C at a rate of 5 °C / min under air atmosphere and held for 12 h to obtain the lithium battery cathode material LiTi. 0.05 Fe 0.03 Zr 0.03 Mn 1.89 O 3.91 F 0.09 .

[0023] The lithium battery cathode material prepared in this embodiment was characterized to obtain... Figure 1 , Figure 2 .from Figure 1It can be seen that the lithium battery cathode material prepared in this embodiment has a uniform particle size distribution, with a particle size of approximately 500 nm. Figure 2 It can be seen that the lithium battery cathode material prepared in this embodiment maintains the pure phase of spinel-shaped lithium manganese oxide.

[0024] Example 2 This embodiment provides a lithium battery cathode material, LiTi. 0.05 Fe 0.03 Zr 0.03 Mn 1.81 O 3.91 F 0.09 Its preparation method includes the following steps: In a glove box under argon atmosphere and with water and oxygen content both less than 0.1 ppm, lithium chloride (LiCl), titanium dioxide (TiO2), ferric trifluoride (FeF3), zirconium dioxide (ZrO2), and manganese chloride (MnCl2) in a molar ratio of 1.05:0.05:0.03:0.03:1.9 were placed in a mortar and manually ground for 20 min until uniformly mixed and free of particles. The mixture was then transferred to an alumina crucible. The alumina crucible was placed in a tube furnace and heated to 550 °C at a rate of 5 °C / min under air atmosphere and held for 12 h. The resulting powder was then heated to 800 °C at a rate of 5 °C / min under air atmosphere and held for 12 h to obtain the lithium-ion battery cathode material LiTi. 0.05 Fe 0.03 Zr 0.03 Mn 1.81 O 3.91 F 0.09 .

[0025] Example 3 This embodiment provides a lithium battery cathode material, LiMg. 0.05 Fe 0.03 Zr 0.03 Mn 1.89 O 3.91 F 0.09 Its preparation method includes the following steps: In a glove box under argon atmosphere and with water and oxygen content both less than 0.1 ppm, lithium chloride (LiCl), magnesium oxide (MgO), ferric trifluoride (FeF3), zirconium dioxide (ZrO2), and manganese chloride (MnCl2) in a molar ratio of 1.05:0.05:0.03:0.03:1.89 were placed in a mortar and manually ground for 20 min until uniformly mixed and free of particles. The mixture was then transferred to an alumina crucible. The alumina crucible was placed in a tube furnace and heated to 550 °C at a rate of 5 °C / min under air atmosphere and held for 12 h. The resulting powder was added to ammonia water at a mass ratio of 1:2 and slowly stirred for 5 h. Subsequently, it was vacuum dried at 120 °C for 12 h, and then heated to 800 °C at a rate of 5 °C / min under an inert atmosphere and held for 2 h to obtain the lithium battery cathode material LiMg. 0.05 Fe 0.03 Zr 0.03 Mn 1.89 O 3.9 1F 0.09 .

[0026] Example 4 This embodiment provides a lithium battery cathode material, LiAl. 0.05 Fe 0.02 Na 0.05 Mn 1.78 O 3.94 F 0.06 Its preparation method includes the following steps: In a glove box under argon atmosphere and with water and oxygen content both less than 0.1 ppm, lithium chloride (LiCl), aluminum chloride (AlCl3), ferric trifluoride (FeF3), sodium carbonate (Na2CO3), and manganese chloride (MnCl2) in a molar ratio of 1.05:0.05:0.025:0.025:1.65 were placed in a mortar and manually ground for 20 min until uniformly mixed and free of particles. The mixture was then transferred to an alumina crucible. The alumina crucible was placed in a tube furnace and heated to 550°C at a rate of 5°C / min under air atmosphere and held for 12 h. The resulting powder was then heated to 800°C at a rate of 5°C / min under air atmosphere and held for 12 h to obtain the lithium battery cathode material LiAl. 0.05 Fe 0.02 Na 0.05 Mn 1.78 O 3.94 F 0.06 .

[0027] Example 5 This embodiment provides a lithium battery cathode material, LiTi. 0.05 Fe 0.05 Zr 0.02 Mn 1.88 O3.94 F 0.06 Its preparation method includes the following steps: In a glove box under argon atmosphere and with water and oxygen content both less than 0.1 ppm, lithium chloride (LiCl), titanium dioxide (TiO2), ferric trifluoride (FeF3), zirconium dioxide (ZrO2), and manganese chloride (MnCl2) in a molar ratio of 1.10:0.05:0.02:0.02:1.88 were placed in a mortar and manually ground for about 20 minutes until uniformly mixed and free of particles. The mixture was then transferred to an alumina crucible. The alumina crucible was placed in a tube furnace and heated to 600°C at a rate of 5°C / min under air atmosphere and held for 12 hours. The resulting powder was then heated to 800°C at a rate of 5°C / min under air atmosphere and held for 12 hours to obtain the lithium battery cathode material LiTi. 0.05 Fe 0.02 Zr 0.02 Mn 1.88 O 3.94 F 0.06 .

[0028] Example 6 This embodiment provides a lithium battery cathode material, LiAl. 0.02 Na 0.05 Co 0.93 O 1.94 F 0.06 Its preparation method includes the following steps: In a glove box under argon atmosphere and with water and oxygen content both less than 0.1 ppm, lithium chloride (LiCl), aluminum fluoride (AlF3), sodium carbonate (Na2CO3), and cobalt chloride (CoCl2) in a molar ratio of 1.05:0.02:0.025:0.93 were placed in a mortar and manually ground for about 20 minutes until uniformly mixed and free of particles. The mixture was then transferred to an alumina crucible. The alumina crucible was placed in a tube furnace and heated to 600°C at a rate of 5°C / min under air atmosphere and held for 12 hours. The resulting powder was then heated to 950°C at a rate of 5°C / min under air atmosphere and held for 12 hours to obtain the lithium battery cathode material LiAl. 0.02 Na 0.05 Co 0.93 O 1.94 F 0.06 .

[0029] Example 7 This embodiment provides a lithium battery cathode material, LiMg. 0.01 Al 0.02 Co 0.97 O 1.94 F 0.06 Its preparation method includes the following steps: In a glove box under argon atmosphere and with water and oxygen content both less than 0.1 ppm, lithium chloride (LiCl), magnesium oxide (MgO), aluminum fluoride (AlF3), and cobalt chloride (CoCl2) in a molar ratio of 1.05:0.01:0.02:0.94 were placed in a mortar and manually ground for about 20 min until uniformly mixed and free of particles. The mixture was then transferred to an alumina crucible. The alumina crucible was placed in a tube furnace and heated to 550 °C at a rate of 5 °C / min under air atmosphere and held for 12 h. The resulting powder was added to ammonia water at a mass ratio of 1:2 and slowly stirred for 5 h. Subsequently, it was vacuum dried at 120 °C for 12 h, and then heated to 970 °C at a rate of 5 °C / min under an inert atmosphere and held for 2 h to obtain the lithium battery cathode material LiMg. 0.01 Al 0.02 Co 0.97 O 1.94 F 0.06 .

[0030] Example 8 This embodiment provides a lithium battery cathode material, LiZr. 0.02 Al 0.02 Ni 0.8 Co 0.06 Mn 0.1 O 1.94 F 0.06 Its preparation method includes the following steps: In a glove box under argon atmosphere and with water and oxygen content both less than 0.1 ppm, lithium chloride (LiCl), zirconium dioxide (ZrO2), aluminum fluoride (AlF3), nickel chloride (NiCl2), cobalt chloride (CoCl2), and manganese chloride (MnCl2) in a molar ratio of 1.05:0.02:0.02:0.8:0.06:0.1 were placed in a mortar and manually ground for about 20 min until uniformly mixed and free of particles. The mixture was then transferred to an alumina crucible. The alumina crucible was placed in a tube furnace and heated to 550°C at a rate of 5°C / min under an oxygen atmosphere and held for 15 h. The resulting powder was then heated to 800°C at a rate of 5°C / min under an oxygen atmosphere and held for 12 h to obtain the lithium-ion battery cathode material LiZrO2. 0.02 Al 0.02 Ni 0.8 Co 0.06 Mn 0.1 O 1.94 F 0.06 .

[0031] Comparative Example This comparative example provides a lithium battery cathode material, LiMn2O4.

[0032] Test case The positive electrode materials obtained in Examples 1-8 and the comparative examples were respectively prepared into positive electrode sheets. The preparation method was as follows: the positive electrode material, polyvinylidene fluoride (PVDF) and superconducting carbon black were ground evenly in a mortar according to a mass ratio of 8:1:1. Then, an appropriate amount of solvent N-methylpyrrolidone (NMP) was added and the mixture was ground thoroughly to obtain a uniform slurry with a certain fluidity. The slurry was evenly coated onto a clean aluminum foil with a scraper and dried to obtain the positive electrode sheet.

[0033] The obtained positive electrode sheets were used to prepare batteries. The method was as follows: the positive electrode sheet, the negative electrode sheet (lithium metal), and the 302 electrolyte (1 mol / L LiPF6 dissolved in a solvent, which was obtained by mixing EC and DEC in a mass ratio of 1:1) were assembled into a CR2032 coin cell.

[0034] The prepared batteries were tested using the Xinwei battery testing system: the batteries were activated for three cycles at 0.1C, followed by a 1C cycle test; the rate tests were performed by cycling at 0.1C, 1C, 2C, 4C, 8C, and 10C currents for five cycles each. The capacity retention rate after 100 cycles was the ratio of the discharge specific capacity at the 100th cycle to the discharge specific capacity at the 4th cycle. The test results are shown in Table 1 and... Figure 3-4 As shown.

[0035] Table 1 Test Results

[0036] The test results show that, compared with the comparative example, the lithium battery cathode material prepared by this invention has significantly improved initial coulombic efficiency, charge-discharge capacity, cycle performance, and rate performance.

[0037] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0038] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a lithium battery cathode material, characterized in that, It includes the following steps: In a glove box, the precursor of the positive electrode active material, the molten medium and the dopant are weighed and ground and mixed; the mixture is sintered once and then sintered a second time to obtain the lithium battery positive electrode material; wherein, the temperature of the first sintering is lower than the temperature of the second sintering, and the molten medium is a compound that is in a molten state during the first sintering process.

2. The method for preparing the lithium battery cathode material according to claim 1, characterized in that, The molten medium is a metal halide, nitrate, or acetate, wherein the metal halide is selected from at least one of lithium fluoride, lithium chloride, aluminum chloride, manganese chloride, aluminum fluoride, and nickel chloride.

3. The method for preparing the lithium battery cathode material according to claim 1, characterized in that, The temperature for the first sintering is 300~600℃.

4. The method for preparing the lithium battery cathode material according to claim 1, characterized in that, The temperature for the secondary sintering is 700~1000℃.

5. The method for preparing the lithium battery cathode material according to claim 1, characterized in that, The positive electrode active material precursor includes a lithium source and a manganese source, and the dopant is selected from at least one of titanium dioxide, iron trifluoride, zirconium dioxide, and aluminum fluoride.

6. The method for preparing the lithium battery cathode material according to claim 1, characterized in that, The positive electrode active material precursor includes a lithium source and a cobalt source, and the dopant is selected from at least one of sodium carbonate, aluminum fluoride, and zirconium dioxide.

7. A lithium battery cathode material, characterized in that, It is prepared by the preparation method described in any one of claims 1-6.

8. The lithium battery cathode material according to claim 7, characterized in that, The structural formula of the lithium battery cathode material is LiM x Mn 2-x O 4-y Y y M is selected from Ti 4+ Fe 3+ Zr 4+ Mg 2+ Al 3+ Na + At least one of them, Y is selected from F - ,Br - Cl - At least one of the following, 0.12≤x≤0.25, 0≤y<0.

1.

9. The lithium battery cathode material according to claim 7, characterized in that, The structural formula of the lithium battery cathode material is LiX. a Co 1-a O2, where X is Mn 2+ Ni 2+ Zr 4+ Mg 2+ Al 3+ Na + At least one of them, 0.06≤a≤0.

94.

10. The application of a lithium battery cathode material prepared by any one of claims 1-6 in a lithium battery.

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