A method for preparing a coated and modified high-voltage lithium cobalt oxide cathode material

Abstract

This invention relates to a method for preparing a coated and modified high-voltage lithium cobalt oxide cathode material, belonging to the field of new energy technology. The method of this invention achieves the synergistic effect of doping and coating through a special synthesis method. Its advantages include suppressing lattice distortion and stabilizing the crystal structure during charge and discharge, while also suppressing interfacial side reactions between the electrolyte and the battery cathode material. Most importantly, it activates the reversible redox reaction of lattice oxygen to provide capacity, thereby ensuring the excellent performance of the lithium cobalt oxide cathode material under high-voltage conditions. This invention uses a solid-state sintering method, which has the advantages of being solvent-free, using readily available raw materials, having low production costs, and high production efficiency, and has broad application prospects in industry.

Description

Technical Field

[0001] This invention relates to a method for preparing a high-voltage lithium cobalt oxide cathode material, belonging to the field of new energy technology. Background Technology

[0002] High-energy-density lithium-ion batteries are a crucial development direction in the energy storage field. Currently, the energy density of lithium-ion batteries is mainly limited by the cathode material. To further improve battery energy density, developing high-voltage, high-capacity cathode materials is essential. Among numerous cathode materials, layered materials have attracted widespread attention due to their high theoretical specific capacity and good electrochemical stability. LiCoO2 has the longest history of application, being the earliest commercially available cathode material for lithium-ion batteries. Its excellent cycle stability, rate performance, and compaction density still allow it to maintain a significant share of the consumer electronics energy storage market. However, the actual capacity of lithium cobalt oxide batteries is still only half of their theoretical capacity. To meet market demands, the cutoff voltage of lithium cobalt oxide is increasing. This leads to irreversible phase transitions and intensified interfacial reactions. Current characterization methods mainly include bulk doping and surface modification, but bulk doping struggles to address surface side reactions, while surface modification struggles to suppress irreversible phase transitions. Therefore, developing new doping and modification strategies is both important and urgent. Chinese invention patent application 202311499644.5 proposes a method for preparing high-voltage lithium cobalt oxide cathode material. This method activates the reversible redox activity of O by precisely controlling the configuration formed between anionic elements and O, thus contributing to the capacity. This achieves high capacity and high capacity retention rate of lithium cobalt oxide cathode material under high voltage conditions. However, the following problems still exist: 1. Doping modification has unavoidable disadvantages. Introducing dopants will cause lattice distortion, leading to structural instability. 2. It cannot solve the side reaction problem at the interface between the cathode material and the electrolyte. 3. The synthesis method is relatively complex, making it difficult to achieve large-scale industrial production. Summary of the Invention

[0003] The method of the present invention aims to improve and solve the problems of the prior art. The doping of the method of the present invention is surface gradient doping, which minimizes lattice distortion as much as possible. It realizes the synergistic effect of doping and coating, solves the problem of interfacial side reactions, and simplifies the synthesis process as much as possible without ensuring that the performance is not greatly lost.

[0004] The technical solution adopted in this invention is: a method for preparing a coated and modified high-voltage lithium cobalt oxide cathode material. The method employs solid-state sintering and, through the synergistic effect of introduced doping and coating, stabilizes the bulk phase and surface structure, while simultaneously activating the reversible redox reaction of oxygen to provide capacity. This achieves excellent performance of the lithium cobalt oxide cathode material under high-voltage conditions. The specific preparation steps are as follows:

[0005] (1) Weigh out Li salt, Co salt or oxide in a certain proportion, grind the weighed raw materials and mix them evenly;

[0006] (2) The mixed raw materials were pre-sintered, then annealed at high temperature and cooled to room temperature to obtain blank lithium cobalt oxide sample;

[0007] (3) Weigh out blank samples of lithium cobalt oxide, A salt or oxide in a certain proportion, grind the weighed materials and mix them evenly;

[0008] (4) The mixed raw materials are sintered and cooled to room temperature to obtain high-performance lithium cobalt oxide with doping and coating synergy.

[0009] In step (1), the Li salt is at least one of LiOH·H2O, Li2CO3, or LiCH3COO;

[0010] In step (1), the Co salt or oxide is at least one of CoSO4, Co(NO3)2, CoCl2 or Co(CH3COO)2;

[0011] In step (1), the salt or oxide containing element A is a salt or oxide containing element A, wherein element A is at least one of Nd, Sm, Pr, Pm, Eu, Gd, V, Zr, Ti, Sc, Yb, Tm, Mo, Zn, Al, Ga, Sn, Ca, Na, K, Mg, La or Ce;

[0012] In step (1), the ratio is Li in Li salt: Co in Co salt or oxide is 1.05-x: 1-y, 0≤x≤0.5, 0≤y≤0.5;

[0013] In step (1), the grinding is performed in an air or argon atmosphere;

[0014] In step (2), the pre-sintering temperature is 100-600℃, the heating rate is 1-20℃ / min, and the time is 1-10 hours; the annealing temperature is 200-1000℃, the heating rate is 1-20℃ / min, and the time is 1-24 hours.

[0015] In step (3), the ratio of the amount of blank sample lithium cobalt oxide to A salt or oxide is 1-z:z, 0≤z≤0.5;

[0016] In step (3), the sintering temperature is 200-800℃, the heating rate is 1-20℃ / min, and the time is 1-10 hours.

[0017] This invention provides a method for preparing high-performance coated and modified lithium cobalt oxide. Through the synergistic effect of coating and doping, this method simultaneously solves the problems of bulk structural instability and increased interfacial side reactions under high voltage conditions, thereby achieving a significant performance improvement.

[0018] Compared with existing technologies, the beneficial effects of this invention are as follows: 1. The method of this invention introduces vacancies by adjusting the ratio of Li source to Co source, allowing some of the coating elements to enter the crystal lattice to form gradient doping, while others remain on the surface to form a coating layer. This achieves a synergistic effect of doping and coating, stabilizing the structure and suppressing interfacial side reactions. The elements entering the crystal lattice also provide capacity for activating reversible oxygen redox processes. 2. The synthesis method used in this invention is simple and controllable, yielding products with excellent performance, high yield, and good reproducibility, making it highly suitable for large-scale industrial production. Attached Figure Description

[0019] Figure 1 (a) and (b) are XRD patterns of the high-voltage, high-capacity, and high-cycle-retention lithium cobalt oxide cathode material prepared by the method of the present invention and ordinary lithium cobalt oxide cathode material, respectively.

[0020] Figure 2 (a) and (b) are respectively a comparison of the rate performance of the high-voltage, high-capacity, and high-cycle-retention lithium cobalt oxide cathode material prepared by the method of the present invention with that of ordinary lithium cobalt oxide cathode material, and a comparison of the discharge specific capacity cycling performance under 1C (200mA / g) and 4.6V cutoff voltage conditions.

[0021] Figure 3 (a) and (b) are comparison graphs showing the changes in the cell parameter c value at 4.6V deep charging between the high-voltage, high-capacity, and high-cycle-retention lithium cobalt oxide cathode material prepared by the method of the present invention and the ordinary lithium cobalt oxide cathode material.

[0022] Figure 4 A comparison of O2 release during deep charge-discharge at 3.0-4.6V between the high-voltage, high-capacity, and high-cycle-retention lithium cobalt oxide cathode material prepared by the method of this invention and ordinary lithium cobalt oxide cathode materials. Detailed Implementation

[0023] The preparation method of high-voltage lithium cobalt oxide cathode material will be further explained in detail below.

[0024] This invention provides a method for preparing a coated and modified high-voltage lithium cobalt oxide cathode material, the preparation steps of which are as follows:

[0025] (1) Weigh out Li salt, Co salt or oxide in a certain proportion, grind the weighed raw materials and mix them evenly;

[0026] (2) The mixed raw materials were pre-sintered, then annealed at high temperature and cooled to room temperature to obtain blank lithium cobalt oxide samples.

[0027] (3) Weigh out blank samples of lithium cobalt oxide, A salt, or oxide in a certain proportion, grind the weighed materials, and mix them evenly.

[0028] (4) The mixed raw materials are sintered and cooled to room temperature to obtain high-performance lithium cobalt oxide with doping and coating synergy.

[0029] In step (1), the Li salt is at least one of LiOH·H2O, Li2CO3, or LiCH3COO;

[0030] In step (1), the Co salt or oxide is at least one of CoSO4, Co(NO3)2, CoCl2 or Co(CH3COO)2;

[0031] In step (1), the salt or oxide containing element A is a salt or oxide containing element A, wherein element A is at least one of Nd, Sm, Pr, Pm, Eu, Gd, V, Zr, Ti, Sc, Yb, Tm, Mo, Zn, Al, Ga, Sn, Ca, Na, K, Mg, La or Ce;

[0032] In step (1), the ratio is Li in Li salt: Co in Co salt or oxide is 1.05-x: 1-y, 0≤x≤0.5, 0≤y≤0.5;

[0033] In step (1), the grinding is performed in an air or argon atmosphere;

[0034] In step (2), the pre-sintering temperature is 100-600℃, the heating rate is 1-20℃ / min, and the time is 1-10 hours; the annealing temperature is 200-1000℃, the heating rate is 1-20℃ / min, and the time is 1-24 hours.

[0035] In step (3), the ratio of the amount of blank sample lithium cobalt oxide to A salt or oxide is 1-z:z, 0≤z≤0.5;

[0036] In step (3), the sintering temperature is 200-800℃, the heating rate is 1-20℃ / min, and the time is 1-10 hours.

[0037] Figure 1(a) and (b) are the XRD patterns of the high-capacity, long-cycle-life lithium cobalt oxide cathode material prepared by the method of this invention and the ordinary lithium cobalt oxide cathode material, respectively. The images illustrate that the material synthesized according to our method has a pure crystalline structure, retains its layered structure, and exhibits peaks related to the coating. This demonstrates that we achieved a synergistic effect of coating and doping while maintaining the original structure.

[0038] Figure 2 Figures (a) and (b) show a comparison of the rate performance of the high-voltage, high-capacity, and long-cycle-life lithium cobalt oxide cathode material modified according to the method of this invention, and a comparison of the discharge specific capacity cycling performance under 1C (200mAh / g) and 4.6V cutoff voltage conditions, respectively. The modified materials exhibit superior rate performance compared to the unmodified samples, especially at high current densities. Particularly at 1C current density, the initial capacity reaches an exceptionally high 220mAh / g, and after 100 cycles, it retains 96% of its capacity, a highly competitive performance.

[0039] Figure 3 (a) and (b) are comparison images under a high-resolution transmission electron microscope (TEM) of the high-voltage, high-capacity, and long-cycle-life lithium cobalt oxide cathode material produced by the method of this invention and ordinary lithium cobalt oxide cathode material. These images illustrate that, compared to ordinary lithium cobalt oxide, the material modified according to our method has a uniform coating layer, suppresses interfacial side reactions during cycling, and achieves a significant performance improvement.

[0040] Figure 4 This figure compares the leading edge peak area of ​​the K-edge absorption spectrum of oxygen in the high-voltage, high-capacity, long-cycle-life lithium cobalt oxide cathode material synthesized using the method of this invention with that of ordinary lithium cobalt oxide cathode material after charging at a depth of 4.6V. The figure illustrates that we first normalized the peak areas of the two materials in their initial states, and then compared the leading edge peak areas during the 4.6V deep charging process. The leading edge peak area reflects the information about the unoccupied electron-hole states of oxygen. A larger peak area indicates more unoccupied electron-hole states in oxygen, proving that oxygen participates more in the reaction and contributes to the capacity. Therefore, the redox activity of oxygen in the material synthesized according to our method is activated.

[0041] The following describes an embodiment of the method of the present invention:

[0042] Example 1:

[0043] (1) According to the molar ratio of Co in Co3O4 to Li in Li2CO3 being 0.99:1.04, weigh out Co3O4, Li2CO3 and raw materials, add all weighed raw materials into an agate mortar and grind them under an argon atmosphere until they are mixed evenly.

[0044] (2) Place the ground raw material in a muffle furnace, pre-sinter at 500°C at 10°C / min for 5 hours, then anneal at 900°C at 10°C / min for 12 hours, and cool to room temperature to obtain blank lithium cobalt oxide sample.

[0045] (3) According to the molar ratio of lithium cobalt oxide to ZnO of blank sample being 99:1, weigh the two raw materials, add all the weighed raw materials into an agate mortar and grind them until they are evenly mixed.

[0046] (4) Place the ground raw material from step (3) into a muffle furnace, heat it at 10℃ / min to 500℃ for 6 hours for pre-sintering, and then cool it to room temperature.

[0047] Example 2:

[0048] The experimental method in this embodiment is basically the same as that in Example 1. The raw materials used in this experiment are CoSO4 and LiOH·H2O.

[0049] Example 3:

[0050] The experimental method in this embodiment is basically the same as that in embodiment 1. In this experiment, the raw materials used in step (1) are CoCl2 and LiCH3COO in a ratio of 0.98:1.04, and the powder is ground in air.

[0051] Example 4

[0052] The experimental method in this embodiment is basically the same as that in Example 1. In this experiment, the raw material used in step (3) is a mixture of CeO2 and blank lithium cobalt oxide in a ratio of 98:2.

[0053] Example 5:

[0054] The experimental method in this embodiment is basically the same as that in Example 1. In this experiment, the raw materials used in step (1) are Co(NO3)2 and LiOH·H2O in a ratio of 0.98:1.02. In step (2), the temperature is increased to 600℃ at 6℃ / min for pre-sintering for 4 hours, and then increased to 1000℃ at 8℃ / min for annealing for 20 hours.

[0055] Example 6:

[0056] The experimental method in this embodiment is basically the same as that in Example 1. The raw materials used in step (1) are Co3O4 and LiCH3COO in a ratio of 0.94:1.03. The raw material used in step (3) is Sm2O3. In step (4), the temperature is increased to 700℃ at 6℃ / min for 8 hours.

[0057] Example 7:

[0058] The experimental method in this embodiment is basically the same as that in Example 1. The raw materials used in step (1) of this experiment are Co(NO3)2 and Li2CO, which are ground under an argon atmosphere. The pre-sintering temperature in step (2) is 400℃.

[0059] Example 8:

[0060] The experimental method in this embodiment is basically the same as that in embodiment 8. The raw materials used in step (1) of this experiment are Co3O4 and LiCH3COO in a ratio of 0.99:1.02, and the raw material used in step (3) is La2O3.

[0061] Example 9:

[0062] The experimental method in this embodiment is basically the same as that in embodiment 1. The raw materials used in step (1) are Co3O4 and LiCH3COO. In step (2), the temperature is increased to 200℃ at 2℃ / min and pre-sintered in an argon atmosphere for 5 hours.

[0063] Example 10:

[0064] The experimental method in this embodiment is basically the same as that in Example 1. The raw materials used in step (1) are CoCl2 and Li2CO3. In step (2), the temperature is increased to 900℃ at 2℃ / min and annealed in air atmosphere for 18 hours.

Claims

1. A method for preparing a coated and modified high-voltage lithium cobalt oxide cathode material, characterized in that, Solid-state sintering was employed, and the bulk phase and surface structure were stabilized through the synergistic effect of doping and coating. Simultaneously, the reversible redox reaction of oxygen was activated to provide capacity. The specific preparation steps are as follows: (1) Weigh out Li salt, Co salt or oxide in a certain proportion, grind the weighed raw materials and mix them evenly; (2) The mixed raw materials were pre-sintered, then annealed at high temperature and cooled to room temperature to obtain blank lithium cobalt oxide sample; (3) Weigh out blank samples of lithium cobalt oxide, A salt or oxide in a certain proportion, grind the weighed materials and mix them evenly; (4) The mixed raw materials are sintered and cooled to room temperature to obtain high-performance lithium cobalt oxide with doping and coating synergy; In step (1), the ratio is Li in Li salt: Co in Co salt or oxide is 1.05-x: 1-y, 0≤x≤0.5, 0≤y≤0.5; In step (3), the salt or oxide containing element A is a salt or oxide containing element A, wherein element A is at least one of Nd, Sm, Pr, Pm, Eu, Gd, V, Zr, Ti, Sc, Yb, Tm, Mo, Zn, Al, Ga, Sn, Ca, Na, K, Mg, La or Ce.

2. The method as described in claim 1, characterized in that, In step (1), the Li salt is at least one of LiOH·H2O, Li2CO3 or LiCH3COO.

3. The method as described in claim 1, characterized in that, In step (1), the Co salt or oxide is at least one of CoSO4, Co(NO3)2, CoCl2 or Co(CH3COO)2.

4. The method as described in claim 1, characterized in that, In step (1), grinding is performed in an air or argon atmosphere.

5. The method as described in claim 1, characterized in that, In step (2), the pre-sintering temperature is 100-600℃, the heating rate is 1-20℃ / min, and the time is 1-10 hours. The annealing temperature is 200-1000℃, the heating rate is 1-20℃ / min, and the time is 1-24 hours.

6. The method as described in claim 1, characterized in that, In step (3), the ratio of the amount of blank sample lithium cobalt oxide to A salt or oxide is 1-z:z, 0≤z≤0.

5.

7. The method as described in claim 1, characterized in that, In step (3), the sintering temperature is 200-800℃, the heating rate is 1-20℃ / min, and the time is 1-10 hours.

8. A high-voltage lithium cobalt oxide cathode material, characterized in that, Prepared by the method described in any one of claims 1-7.

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