Sodium-based multi-metal oxide positive electrode strengthening method based on dry ice quenching

Abstract

The invention discloses a dry ice quenching-based sodium-based multi-element metal oxide positive electrode strengthening method, which comprises the following steps: uniformly mixing a metal oxide precursor and a sodium source, heating to a certain temperature in an air atmosphere at a certain heating rate, and sintering for a period of time to obtain a sodium-based multi-element metal oxide; placing the dry ice in a dry sealed chamber, and standing for a period of time to form a quenching chamber; rapidly placing the sodium-based multi-element metal oxide in a quenching chamber, sealing, and then standing and quenching in a vacuum state for a period of time; and carrying out low-temperature tempering heat treatment on the quenched sodium-based multi-element metal oxide in a certain atmosphere for a period of time to obtain the reinforced sodium-based multi-element metal oxide positive electrode material. According to the strengthening method, the dry ice is used as a quenching medium source, the problems of unstable intrinsic structure and high surface alkalinity caused by internal stress accumulation in the synthesis process of the sodium-based multi-element metal oxide are solved, and excellent electricity storage performance and long-acting stability are obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrochemistry and secondary battery technology, and particularly relates to a sodium-based multi-metal oxide positive electrode strengthening method based on dry ice quenching. BACKGROUND

[0002] As one of the most promising material systems for industrialization and application, sodium-based multi-metal oxide Na x M ɑ M β M γ O2 (M is Fe, Ni, Mn, Ti, Cu, etc., and ɑ+β+γ=1) has intrinsic structural instability due to internal stress accumulation during synthesis, and has a serious surface residual alkali problem due to the high alkaline synthesis environment, which limits the stable electrochemical performance. Therefore, it is urgent to develop a sodium-based multi-metal oxide positive electrode strengthening method to solve these problems. SUMMARY

[0003] In order to solve the problems presented in the background art, the purpose of the present application is to provide a sodium-based multi-metal oxide positive electrode strengthening method based on dry ice quenching. The strengthening method of the present application uses solid carbon dioxide (dry ice) as a quenching medium source, and uses the carbon dioxide generated by the sublimation of dry ice to form a low-temperature carbon dioxide supersaturated quenching environment. The high-temperature sintered sodium-based multi-metal oxide powder is rapidly quenched to reduce the defect density of the positive electrode crystal structure during annealing and inhibit the accumulation of internal stress, and to form a homogeneous and stable surface passivation layer, so as to achieve the synergistic strengthening of the sodium-based multi-metal oxide positive electrode bulk phase-surface, solve the intrinsic structural instability problem caused by internal stress accumulation during the synthesis of sodium-based multi-metal oxide, and the problem of high surface alkali, and obtain excellent storage performance and long-term stability.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: on the one hand, the present application provides a sodium-based multi-metal oxide positive electrode strengthening method based on dry ice quenching, which comprises the following steps:

[0005] (1) uniformly mix the metal oxide precursor and the sodium source, heat to a certain temperature at a certain heating rate in an air atmosphere, and sinter for a period of time to obtain a sodium-based multi-metal oxide;

[0006] (2) place solid carbon dioxide (dry ice) in a dry sealed chamber, and stand for a period of time to form a quenching chamber;

[0007] (3) quickly place the sodium-based multi-metal oxide prepared in step (1) into the quenching chamber, seal it, and stand for a period of time under vacuum quenching;

[0008] (4) quenching the sodium-based multi-metal oxide obtained in step (3) and then performing low-temperature tempering heat treatment under a certain atmosphere for a period of time to obtain a strengthened sodium-based multi-metal oxide positive electrode material.

[0009] Further, the metal oxide precursor in step (1) is at least two of NiO, MnO2, FeO, Fe2O3, Co2O3, ZrO2, ZnO, CuO, and TiO2.

[0010] The sodium source in step (1) is sodium carbonate.

[0011] Further, the molar ratio of the metal oxide precursor to the sodium source in step (1) is (0.6-1):1.

[0012] Further, the heating rate in step (1) is 2-10 ℃ / min, the sintering temperature is 800-1000 ℃, and the sintering time is 10-20 h.

[0013] Further, the dry sealed chamber in step (2) is achieved by a drying agent, and the drying agent is one or more of silica gel, zeolite molecular sieve, metal silicate, and mineral-based adsorbent.

[0014] Further, the dry ice in step (2) is one or more of block dry ice, granular dry ice, powdered dry ice, and dry ice-ethanol mixture.

[0015] Further, the mass ratio of the dry ice in step (2) to the sodium-based multi-metal oxide in step (1) is (5-50):100, preferably (25-50):100.

[0016] Further, the standing time in step (2) is 1-30 min.

[0017] Further, the pressure in the vacuum state in step (3) is 10 5 ~10 -5 Pa. The vacuum is mainly for dehumidification, because the treated material is a water-sensitive material, and water vapor will liquefy and damage the material after dry ice vaporization.

[0018] Further, the standing quenching time in step (3) is 2-120 min.

[0019] Further, the atmosphere for the low-temperature tempering heat treatment in step (4) is one or more of air, oxygen, carbon dioxide, nitrogen, and argon.

[0020] Further, the temperature for the low-temperature tempering heat treatment in step (4) is 150-400 ℃, and the time for the low-temperature tempering heat treatment is 30-180 min.

[0021] In another aspect, the application provides a reinforced sodium-based multi-metal oxide cathode material, which is prepared by the dry-ice quenching-based sodium-based multi-metal oxide cathode reinforcement method described above.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] In the application, low-temperature carbon dioxide generated by the sublimation of solid carbon dioxide (dry ice) forms a carbon dioxide-rich atmosphere in a dry sealed chamber, and sodium-based multi-metal oxide powder at high temperature is placed in the chamber for quenching treatment. On the one hand, the sodium-based multi-metal oxide grains are rapidly cooled and the stress relaxation in the grains by the low-temperature carbon dioxide sublimated and vaporized by the dry ice, which relieves the accumulation of internal stress generated during slow annealing, and the slightly higher temperature reduces the formation of defects in the crystal structure due to supercooling (dry ice is -78.5℃, and liquid nitrogen is -196°C). On the other hand, the formation of surface residual alkali is inhibited in the dry quenching environment, and gaseous carbon dioxide cannot be embedded between the sodium layers in the anhydrous medium environment, and the excess sodium source forms a homogeneous and stable passivation layer on the surface in the carbon dioxide-rich gaseous environment. In addition, the diffusion rates of different metal elements are different at different supercooling temperatures, and the segregation of specific metal elements on the surface layer to form a reinforced shell layer can be controlled by quenching, which together with the above-mentioned passivation layer forms a surface with enhanced stability, which can significantly improve the humidity sensitivity problem of the sodium-based multi-metal oxide cathode material.

[0024] The reinforced sodium-based multi-metal oxide cathode material has high initial discharge specific capacity and high capacity retention rate, and has excellent power storage performance and long-term stability. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The structure of the sealed chamber used in the embodiments of the application is shown in the accompanying drawings. DETAILED DESCRIPTION

[0026] In order to better understand the content of the application, the content of the application will be further described below in combination with specific implementation methods, but the protection content of the application is not limited to the following embodiments.

[0027] The structure of the sealed chamber used in the embodiments of the application is shown in the accompanying drawings. Figure 1 As shown in the accompanying drawings, the sealed chamber includes a dry ice tank, a quenching chamber (for placing substances that need to be quenched), a desiccant placement tank, a detachable sealing port, and a vacuum valve.

[0028] Example 1

[0029] NiFe2MnO4 is synthesized by selecting NiO, Fe2O3 and MnO2 as metal oxide precursors. 1 / 3 Fe1 / 3 Mn 1 / 3 O2. NiO, Fe2O3, MnO2and sodium carbonate were mixed uniformly in a molar ratio of 1:0.5:1:3, and sintered at 900℃ for 15 h in an air atmosphere at a temperature rising rate of 5℃ / min to obtain NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2. The sealed chamber was dried using color-changing silica gel, and 5 g of block dry ice was placed in the sealed chamber to form a quenching chamber. 20 g of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2was quickly taken out and placed in the quenching chamber, and after sealing, vacuum was extracted to a negative pressure of 10 5 Pa and left for 5 min. The quenched NaNi 1 / 3Fe 1 / 3 Mn 1 / 3 O2was tempered at 300℃ for 2 h in an air atmosphere, cooled to 150℃ and taken out to obtain reinforced NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3O2cathode material. 400 mg of reinforced NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2cathode material, 50 mg of polyvinylidene fluoride (PVDF), and 50 mg of conductive carbon black were prepared into a slurry in N-methyl pyrrolidone (NMP), coated on an aluminum foil with a doctor blade at a height of 250 μm, and dried into a cathode sheet. The cathode sheet was punched into a 12 mm diameter electrode sheet, and a button cell was prepared for electrochemical testing.

[0030] Example 2

[0031] NiO, Fe2O3, MnO2, CuO, TiO2were selected as metal oxide precursors to synthesize NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8Ti 1 / 8 O2. NiO, Fe2O3, MnO2, CuO, TiO2and sodium carbonate were mixed uniformly in a molar ratio of 1:0.5:1:0.5:0.5:4, and sintered at 900℃ for 16 h in an air atmosphere at a temperature rising rate of 5℃ / min to obtain NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8Ti 1 / 8O2. Dry the sealed chamber using color-changing silica gel and place 5 g of block dry ice in the sealed chamber to form a quenching chamber. Place 20 g of NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2. Take out and place in the quenching chamber, seal and vacuumize to a negative pressure of 10 5 Pa and stand for 5 min. Take out the quenched NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2. Anneal at 300°C for 2 h in air atmosphere, cool down to 150°C and take out to obtain reinforced NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 cathode material. Take 400 mg of reinforced NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 cathode material, 50 mg of polyvinylidene fluoride (PVDF) and 50 mg of conductive carbon black are mixed in N-methyl pyrrolidone (NMP) to form a slurry, which is coated on an aluminum foil with a doctor blade at a height of 250 μm and dried to form a cathode sheet. The cathode sheet is punched into a 12 mm diameter electrode sheet and prepared into a button cell for electrochemical testing.

[0032] Example 3

[0033] NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8Ti 1 / 8 O2. NiO, Fe2O3, MnO2, CuO, TiO2 and sodium carbonate are mixed in a molar ratio of 1:0.5:1:0.5:0.5:4, heated to 900°C at a rate of 5°C / min in air atmosphere and sintered for 16 h to obtain NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8Ti 1 / 8 O2. Dry the sealed chamber using color-changing silica gel and place 10 g of block dry ice in the sealed chamber to form a quenching chamber. Place 20 g of NaNi1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2was quickly taken out and placed in a quenching chamber, sealed and vacuumed to a negative pressure of 10 5 Pa and left for 5 min. The quenched NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2was tempered at 300°C in an air atmosphere for 2 h, cooled to 150°C and taken out to obtain the reinforced NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2cathode material. 400 mg of the reinforced NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2cathode material, 50 mg of polyvinylidene fluoride (PVDF) and 50 mg of conductive carbon black were prepared into a slurry in N-methyl pyrrolidone (NMP), coated on an aluminum foil with a doctor blade at a height of 250 μm, and dried into a cathode sheet. The cathode sheet was punched into a 12 mm diameter electrode sheet and prepared into a button cell for electrochemical testing.

[0034] Comparative Example 1

[0035] NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2was synthesized by selecting NiO, Fe2O3, MnO2as the metal oxide precursor. NiO, Fe2O3, MnO2and sodium carbonate were mixed uniformly in a molar ratio of 1:0.5:1:3, heated to 900°C at a heating rate of 5°C / min in an air atmosphere and sintered for 15 h to obtain NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2. 20 g of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2was quickly taken out and placed in air for quenching for 30 min to obtain NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2cathode material. The NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3O2 cathode material was dried in a vacuum oven at 100 °C overnight. 400 mg of the vacuum dried NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 cathode material, 50 mg of polyvinylidene fluoride (PVDF) and 50 mg of conductive carbon black were mixed in N-methyl pyrrolidone (NMP) to form a slurry, which was coated on an aluminum foil with a doctor blade of 250 pm height and dried to form a cathode sheet. The cathode sheet was punched into a 12 mm diameter electrode and assembled into a coin cell for electrochemical testing.

[0036] Comparative Example 2

[0037] NiO, Fe2O3, MnO2, CuO, and TiO2 were chosen as metal oxide precursors to synthesize NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8Ti 1 / 8 O2. NiO, Fe2O3, MnO2, CuO, and TiO2 were mixed in a molar ratio of 1 :0.5:1 :0.5:0.5:4, sintered in air at 900 °C for 16 h with a ramp rate of 5 °C / min, and naturally cooled in the furnace to 150 °C to obtain NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 cathode material. 400 mg of the NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / O2 cathode material, 50 mg of polyvinylidene fluoride (PVDF) and 50 mg of conductive carbon black were mixed in N-methyl pyrrolidone (NMP) to form a slurry, which was coated on an aluminum foil with a doctor blade of 250 pm height and dried to form a cathode sheet. The cathode sheet was punched into a 12 mm diameter electrode and assembled into a coin cell for electrochemical testing.

[0038] Comparative Example 3

[0039] NiO, Fe2O3, MnO2, CuO, and TiO2 were chosen as metal oxide precursors to synthesize NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8Ti 1 / 8O2. NiO, Fe2O3, MnO2, CuO, TiO2, and sodium carbonate were mixed uniformly in a molar ratio of 1:0.5:1:0.5:0.5:4. The mixture was heated to 900℃ in air at a heating rate of 5℃ / min and sintered for 16 h to obtain NaNi. 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8Ti 1 / 8 O2, 20 g NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 was quickly removed and placed in air to quench for 30 minutes. The quenched NaNi... 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 was annealed at 300°C for 2 hours in air atmosphere, and then cooled to 150°C to obtain NaNi. 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 cathode material. Take 400 mg of NaNi. 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 cathode material, 50 mg of polyvinylidene fluoride (PVDF), and 50 mg of conductive carbon black were formulated into a slurry in N-methylpyrrolidone (NMP). The slurry was coated onto aluminum foil using a 250 μm height surface of a scraper and then dried to form a cathode sheet. The cathode sheet was then stamped into a 12 mm diameter electrode and fabricated into a coin cell for electrochemical testing.

[0040] Comparative Example 4

[0041] NaNi was synthesized using NiO, Fe2O3, MnO2, CuO, and TiO2 as metal oxide precursors. 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8Ti 1 / 8 O2. NiO, Fe2O3, MnO2, CuO, TiO2, and sodium carbonate were mixed uniformly in a molar ratio of 1:0.5:1:0.5:0.5:4. The mixture was heated to 900℃ in air at a heating rate of 5℃ / min and sintered for 16 h to obtain NaNi. 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8Ti 1 / 8 O2. Add 20 g of NaNi 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 was quickly removed, and the powder was quenched by casting with liquid nitrogen for 5 minutes. The quenched NaNi... 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 was annealed at 300°C for 2 hours in air atmosphere, and then cooled to 150°C to obtain NaNi. 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 cathode material. Take 400 mg of NaNi. 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 O2 cathode material, 50 mg of polyvinylidene fluoride (PVDF), and 50 mg of conductive carbon black were formulated into a slurry in N-methylpyrrolidone (NMP). The slurry was coated onto aluminum foil using a 250 μm height surface of a scraper and then dried to form a cathode sheet. The cathode sheet was then stamped into a 12 mm diameter electrode and fabricated into a coin cell for electrochemical testing.

[0042] The electrochemical performance results of the comparative examples and embodiments described above are shown in the table below.

[0043]

[0044] Comparative Example 1 and Example 1 are sodium-based ternary metal oxides NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 was subjected to air quenching and dry ice quenching respectively. The table shows that dry ice quenching resulted in a slight increase in specific capacity compared to air quenching. This is attributed to the rapid adsorption of water on the surface during air quenching, which affects the water-sensitive NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 Na precipitation occurred on the surface of the O2 material; however, the dehumidification conditions and supersaturated carbon dioxide concentration in the dry ice quenching chamber significantly reduced surface damage. Simultaneously, the significantly improved capacity retention indicates that dry ice cryogenic quenching reduced stress accumulation and enhanced the internal fracture resistance of the particles.

[0045] Comparative Examples 2, 3, and 4 are sodium-based pentagonal metal oxides, NaNi. 1 / 4 Fe 1 / 4 Mn1 / 4 Cu 1 / 8 Ti 1 / 8 O2 was subjected to slow cooling annealing, air quenching, and liquid nitrogen quenching. The table shows that conventional slow cooling annealing, due to the gradual accumulation of internal stress, causes significant cracking of the cathode particles during long-term cycling, resulting in a decrease in cycle capacity retention (73.8%). Quenching significantly improves this situation. The effects of different quenching media also vary. For relatively stable sodium-based pentagonal metal oxides, air quenching reduces Na precipitation (112.34 mAh / g); however, liquid nitrogen quenching leads to a large accumulation of moisture, exacerbating the loss of active Na (107.1 mAh / g).

[0046] Examples 2 and 3 are sodium-based pentagonal metal oxides NaNi. 1 / 4 Fe 1 / 4 Mn 1 / 4 Cu 1 / 8 Ti 1 / 8 Electrochemical data after dry ice quenching were used for O2. The table shows that the cathode material obtained by dry ice quenching exhibits high initial discharge specific capacity, discharge specific capacity, initial coulombic efficiency, and capacity retention. The improved cycle capacity retention indicates that this milder quenching medium is more effective than liquid nitrogen in alleviating internal stress accumulation and toughening the cathode particles. Simultaneously, the higher and more stable specific capacity performance suggests that the low-temperature carbon dioxide atmosphere in the dehumidification chamber is beneficial for the cathode powder to form a stable surface layer during quenching. Furthermore, the amount of dry ice quencher added also affects its quenching effect and the final performance of the cathode material.

[0047] The above description is only a specific embodiment of the present invention and not all embodiments. Any equivalent modifications made by those skilled in the art to the technical solutions of the present invention by reading the present invention specification are covered by the claims of the present invention.

Claims

1. A method for strengthening sodium-based multi-metal oxide cathodes based on dry ice quenching, characterized in that, Includes the following steps: (1) Mix the metal oxide precursor with the sodium source evenly, raise the temperature to a certain temperature at a certain heating rate in the air atmosphere and sinter for a period of time to obtain sodium-based multi-metal oxide. (2) Place dry ice in a dry, sealed chamber and let it stand for a period of time to form a quenching chamber; (3) The sodium-based multi-metal oxide prepared in step (1) is quickly placed in the quenching chamber, sealed, and then quenched in a vacuum for a period of time. (4) The sodium-based multi-metal oxide quenched in step (3) is subjected to low-temperature tempering heat treatment in a certain atmosphere for a period of time to obtain the enhanced sodium-based multi-metal oxide cathode material.

2. The method for strengthening sodium-based multi-metal oxide cathodes based on dry ice quenching according to claim 1, characterized in that, The metal oxide precursor mentioned in step (1) is at least two of the following: NiO, MnO2, FeO, Fe2O3, Co2O3, ZrO2, ZnO, CuO, and TiO2; The sodium source mentioned in step (1) is sodium carbonate.

3. The method for strengthening sodium-based multi-metal oxide cathodes based on dry ice quenching according to claim 1, characterized in that, The molar ratio of the metal oxide precursor and the sodium source in step (1) is (0.6~1):

1.

4. The method for strengthening sodium-based multi-metal oxide cathodes based on dry ice quenching according to claim 1, characterized in that, The heating rate in step (1) is 2~10℃ / min, the sintering temperature is 800~1000℃, and the sintering time is 10~20 h.

5. The method for strengthening sodium-based multi-metal oxide cathodes based on dry ice quenching according to claim 1, characterized in that, The drying of the sealed chamber in step (2) is achieved by a desiccant, which is one or more of silica gel, zeolite molecular sieve, metal silicate, and mineral-based adsorbent. The dry ice mentioned in step (2) is one or more of the following: block dry ice, granular dry ice, powdered dry ice, and dry ice-ethanol mixture.

6. The method for strengthening sodium-based multi-metal oxide cathodes based on dry ice quenching according to claim 1, characterized in that, The mass ratio of the dry ice in step (2) to the sodium-based multi-metal oxide in step (1) is (5~50):100; The settling time in step (2) is 1 to 30 minutes.

7. The method for strengthening sodium-based multi-metal oxide cathodes based on dry ice quenching according to claim 1, characterized in that, The pressure of the vacuum state described in step (3) is 10. 5 ~10 -5 Pa; The static quenching time in step (3) is 2~120 min.

8. The method for strengthening sodium-based multi-metal oxide cathodes based on dry ice quenching according to claim 1, characterized in that, The atmosphere for the low-temperature tempering heat treatment in step (4) is one or more of air, oxygen, carbon dioxide, nitrogen, and argon.

9. The method for strengthening sodium-based multi-metal oxide cathodes based on dry ice quenching according to claim 1, characterized in that, The temperature of the low-temperature tempering heat treatment in step (4) is 150~400℃, and the time of the low-temperature tempering heat treatment is 30~180 min.

10. A reinforced sodium-based multi-metal oxide cathode material, characterized in that, It is prepared by the sodium-based multi-metal oxide cathode strengthening method based on dry ice quenching as described in any one of claims 1 to 9.

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