Coating modification method for improving electrochemical performance of NaNi0. 5Mn0. 5O2 positive electrode material

Abstract

The invention relates to electrochemistry, in particular to a coating modification method for improving the electrochemical performance of a NaNi0. 5Mn0. 5O2 positive electrode material, which comprises the following steps: preparing DMF (Dimethyl Formamide) and PTA (Pure Terephthalic Acid) into a solution, then preparing DMF and Ni (NO) 3.6 H2O into a solution, and mixing the two solutions to obtain a precursor solution; pouring the precursor solution into a reaction kettle for reaction, cooling the solution to room temperature after the reaction is finished, centrifuging for 3 minutes, and drying in a drying box after the centrifugation is finished, so as to obtain a Ni-MOFs precursor; the preparation method comprises the following steps: weighing Na2CO3, NiO and MnO2, grinding, transferring the ground particles into a calcining furnace, heating, and raising the temperature to 900 DEG C to obtain an O3 type material; acetate, the Ni-MOFs precursor, ferric nitrate and titanium dioxide are weighed and dissolved, then the solution is heated, dewatered and dried, and a high-entropy oxide precursor is obtained; and grinding the high-entropy oxide precursor, and heating to 950 DEG C to obtain the NaNi0. 5Mn0. 5O2 positive electrode material. The Ni-MOFs high-entropy oxide coated O3-NaNi0. 5Mn0. 5O2 sodium ion battery positive electrode material prepared by the preparation method disclosed by the invention shows excellent cycle performance, and a relatively high capacity retention rate is realized.

Description

Technical Field

[0001] The present invention relates to electrochemistry, and particularly to a coating modification method for improving the electrochemical performance of a NaNi 0.5 Mn 0.5 O2 cathode material. Background Art

[0002] Sodium-ion batteries (SIBs) have emerged as a promising new energy material, not only because of their low raw material cost and large reserves, but also because SIBs have higher safety and superior high / low temperature reliability compared to the most advanced lithium-ion batteries. O3-type materials can provide higher specific capacity because there is an adequate Na + reservoir in the initial framework, which makes them attractive when paired with sodium-free anodes.

[0003] However, their practical application prospects are limited by two key drawbacks, namely the inherent air sensitivity of sodium-ion batteries and the slow Na diffusion kinetics. When O3-type materials are exposed to air, active Na escapes from the lattice to the surface, accompanied by the formation of a Na-deficient phase and the oxidation of transition metal ions in the matrix.

[0004] Therefore, there is a need for a simple and general preparation method for NaNi 0.5 Mn 0.5 O2 cathode materials that can optimize air sensitivity and kinetics. Summary of the Invention

[0005] The main object of the present invention is to provide a coating modification method for improving the electrochemical performance of a NaNi 0.5 Mn 0.5 O2 cathode material, aiming to solve the problem that the air sensitivity and kinetics of sodium-ion electrode materials in the prior art are difficult to meet commercial requirements.

[0006] To achieve the above object, the present invention proposes a coating modification method for improving the electrochemical performance of a NaNi 0.5 Mn 0.5 O2 cathode material, and the method includes the following steps:

[0007] Prepare a precursor solution by preparing a solution of DMF and PTA, then preparing a solution of DMF and Ni(NO)3·6H2O, and then mixing the two solutions to obtain a precursor solution;

[0008] Prepare a precursor by pouring the precursor solution into a reaction kettle and reacting at 120°C for 12 h. After the reaction, cool the solution to room temperature, centrifuge at 8500 rpm for 3 min, and then place it in a drying oven at 80°C for 6 h to obtain a Ni-MOFs precursor;

[0009] To prepare the O3-type material, weigh 3.387 g of Na2CO3, 2.24 g of NiO, and 2.61 g of MnO2 reagents and grind them. Then transfer the ground particles into a calcination furnace and heat them continuously at 500 °C for 12 h, and then raise the temperature to 900 °C and continue for 12 h to obtain the O3-type material;

[0010] To prepare the high-entropy oxide precursor, weigh acetate, Ni-MOFs precursor, iron nitrate, and titanium dioxide and dissolve them. Then heat the solution to remove water and dry it to obtain the high-entropy oxide precursor;

[0011] Coat NNMO with the high-entropy oxide HEO-Ni. Grind the high-entropy oxide precursor and then calcine it at 950 °C for 24 h to obtain the NaNi 0.5 Mn 0.5 O2 cathode material.

[0012] Furthermore, for the step of preparing the precursor solution, preparing a solution of DMF and PTA, then preparing a solution of DMF and Ni(NO)3·6H2O, and then mixing the two solutions to obtain the precursor solution, further includes:

[0013] Add 10 - 20 ml of DMF to 0.4984 g of PTA, then take 10 ml of DMF and add 0.8724 g of Ni(NO)3·6H2O to it, and stir each of the two solutions for 5 - 10 min;

[0014] Mix the two solutions to obtain the precursor solution.

[0015] Furthermore, for the step of mixing the two solutions to obtain the precursor solution, further includes:

[0016] Slowly pour the PTA solution into the Ni(NO)3·6H2O solution and continuously stir at a speed of 350 rmp for 30 min to obtain a transparent turquoise mixed solution;

[0017] Transfer the mixed solution to the inner lining of a reaction kettle, raise the temperature to 120 °C and react for 12 h;

[0018] After the reaction, cool the mixed solution to room temperature, transfer it to a centrifuge and centrifuge at 8500 rpm for 3 min;

[0019] During centrifugation, wash it alternately with absolute ethanol and deionized water. After washing, transfer it back to the centrifuge for centrifugation. After centrifuging 3 times, transfer it to an 80 °C drying oven and dry it for 6 h to obtain the Ni-MOFs precursor.

[0020] Further, in the step of preparing the high-entropy oxide precursor by weighing acetate, Ni-MOFs precursor, iron nitrate and titanium dioxide for dissolution and then heating and drying the solution to remove water to obtain the high-entropy oxide precursor, the following steps are further included:

[0021] Weigh acetate, Ni-MOFs precursor, iron nitrate and titanium dioxide and dissolve them in deionized water of citric acid with a molar ratio of HEO-Ni of 1 time, and stir at room temperature for 30 min;

[0022] After adding the bare NNMO with the corresponding molar mass according to the surface coating amount to the above solution, transfer the mixed solution to an oil bath at 60 °C and continuously stir until the water is completely evaporated;

[0023] After the water is completely evaporated, a brownish-green colloid is formed. Transfer the brownish-green colloid to a blast drying oven and dry it at 80 °C for 6 h to obtain the high-entropy oxide precursor.

[0024] Further, the acetate includes: manganese acetate, copper acetate, magnesium acetate, sodium acetate.

[0025] Further, in the step of coating the high-entropy oxide HEO-Ni on NNMO, after grinding the high-entropy oxide precursor and heating it to 950 °C for calcination for 24 h to obtain the NaNi 0.5 Mn 0.5 O2 cathode material for sodium-ion batteries, the following steps are further included:

[0026] Place the high-entropy oxide precursor in an agate mortar and grind it into fine powder. Then place the fine powder in a tube furnace and anneal it at 950 °C for 24 h to obtain the NNMO@HEO-Ni composite material.

[0027] In the present invention, the O3-NaNi coated with Ni-MOFs high-entropy oxide is prepared by the sol-gel method and the low-temperature annealing treatment process. By performing physical characterization tests on this material and studying its electrochemical properties, it can be concluded that the cathode material for sodium-ion batteries disclosed in the present invention shortens the diffusion path of sodium ions, can achieve a high capacity retention rate, and improves the electrochemical performance. 0.5 Mn 0.5 O2 sodium-ion battery cathode material, and through physical characterization tests on this material and research on its electrochemical properties, it can be concluded that the sodium-ion battery cathode material disclosed in the present invention shortens the diffusion path of sodium ions, can achieve a high capacity retention rate, and improves the electrochemical performance. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the processes shown in these drawings.

[0029] Figure 1 Schematic flow chart of Example 1 in the method for coating modification to improve the electrochemical performance of the NaNi 0.5 Mn 0.5 O2 cathode material;

[0030] Figure 2 Schematic flow chart of Example 1 in the method for coating modification to improve the electrochemical performance of the NaNi 0.5 Mn 0.5 XRD patterns of Examples 1-3 in the method for coating modification to improve the electrochemical performance of the NaNi

[0031] Figure 3 SEM images, HRTEM images, and selected area electron diffraction patterns of Examples 1-3 in the method for coating modification to improve the electrochemical performance of the NaNi 0.5 Mn 0.5 O2 cathode material;

[0032] Figure 4 First charge-discharge diagrams of Examples 1-3 in the method for coating modification to improve the electrochemical performance of the NaNi 0.5 Mn 0.5 O2 cathode material;

[0033] Figure 5 Rate performance of Examples 1-3 and the control example in the method for coating modification to improve the electrochemical performance of the NaNi 0.5 Mn 0.5 O2 cathode material;

[0034] Figure 6 Cycling diagrams at 0.1C rate of Examples 1-3 and the control example in the method for coating modification to improve the electrochemical performance of the NaNi 0.5 Mn 0.5 O2 cathode material;

[0035] Figure 7 Cycling diagrams at 1C rate of Examples 1-3 and the control example in the method for coating modification to improve the electrochemical performance of the NaNi 0.5 Mn 0.5 O2 cathode material; Detailed implementation manners

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0037] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0038] In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0039] It can be understood that the preparation method of enhancing the layered cathode material of sodium-ion batteries by combining the high-entropy oxide coating layer of MOF belongs to the field of electrochemistry. Achieving the synchronous improvement of the air sensitivity and kinetics of the sodium-ion battery cathode material is crucial for promoting the commercial application of O3-type Na-based layered oxide cathodes. In particular, the surface coating method is an effective way to improve the cycle life of electrode materials. The surface coating not only maintains the structural stability of the material but also prevents the formation of Na2CO3 and / or NaHCO3 on the material surface by hardly absorbing CO2 and H2O.

[0040] MOF (Metal organic Framework) is a group of porous materials with high crystallinity and has been widely used as a synthetic metal oxide. This is mainly due to their unique structural characteristics, including a large surface area, a well-defined pore structure, the presence of metal active sites, and a channel-based structure. High-entropy oxide (HEO) is an oxide obtained by mutually dissolving 5 or more metal or non-metal oxides in an equimolar or near-equimolar ratio to obtain a single structure. HEO represents a multi-element metal system that can crystallize in a single phase, where different systems can adopt different crystal structures, including single-phase rock salt, spinel, and perovskite structures. Generally, five or more main elements share equal atomic sites in HEO, and these sites can stabilize the solid solution state, showing excellent mechanical properties such as high fracture toughness, high strength, good high and low temperature properties, and energy storage properties.

[0041] In the prior art, NaNi 0.5 Mn 0.5The O2 material has inherent air sensitivity and slow Na diffusion kinetics. When the O3 material is exposed to air, some active Na will escape from the lattice to the material surface, accompanied by the formation of Na-deficient phases and the oxidation of transition metal ions in the matrix, which affects the electrochemical performance of the material. At the same time, the conductivity of the common coating components is relatively low, resulting in an increase in surface polarization of the material and a significant reduction in electrochemical performance. It can be understood that in the present invention, a porous MOF material is combined with high entropy to prepare a high entropy oxide. The MOF material itself has a large specific surface area and a high porosity. The large specific surface area enables the electrode material to fully contact with the electrolyte, while the high porosity can accelerate the transport rate of sodium ions.

[0042] In the O3-NaTMO2 system of the present invention, the octahedral TM sites Ni 2+ , Cu 2+ and Fe 3+ will provide charge compensation for the capacity, and Mg 2+ and Ti 4+ can stabilize the entire structural matrix during the Na-(de)intercalation process, and Mn 4+ enriches the structure.

[0043] The coating modification method for improving the electrochemical performance of the NaNi 0.5 Mn 0.5 O2 cathode material disclosed in the present invention is as Figure 1 shown, and the specific steps are as follows:

[0044] S1. Prepare a precursor solution. Add 10 - 20 ml of DMF to 0.4984 g of PTA, then take 10 ml of DMF and add 0.8724 g of Ni(NO)3·6H2O to it, and stir the two solutions for 5 - 10 min respectively; slowly pour the PTA solution into the Ni(NO)3·6H2O solution, and continuously stir at a speed of 350 rmp for 30 min to obtain a transparent turquoise mixed solution; transfer the mixed solution to the inner lining of the reaction kettle, heat it to 120 °C and react for 12 h; after the reaction, cool the mixed solution to room temperature, transfer it to a centrifuge and centrifuge at 8500 rpm for 3 min; during centrifugation, wash it alternately with absolute ethanol and deionized water, then transfer it back to the centrifuge for centrifugation, and after centrifuging 3 times, transfer it to an 80 °C drying oven and dry it for 6 h to obtain the Ni-MOFs precursor;

[0045] S2. Prepare the precursor. Pour the precursor solution into the reaction kettle and react at 120 °C for 12 h. After the reaction, cool the solution to room temperature, centrifuge it at 8500 rpm for 3 min, and then put it into an 80 °C drying oven and dry it for 6 h to obtain the Ni-MOFs precursor;

[0046] S3. Prepare the O3-type material. Weigh 3.387 g of Na2CO3, 2.24 g of NiO, and 2.61 g of MnO2 reagents and grind them. Then transfer the ground particles into a calcination furnace and heat them continuously at 500 °C for 12 h, and then raise the temperature to 900 °C and continue for 12 h to obtain the O3-type material;

[0047] S4. Prepare the high-entropy oxide precursor. Weigh acetate, Ni-MOFs precursor, iron nitrate, and titanium dioxide and dissolve them in citric acid deionized water with a molar ratio of 1 times the HEO-Ni molar ratio, and stir for 30 min at room temperature; add the corresponding molar mass of bare NNMO according to the surface coating amount to the above solution, and then transfer the mixed solution to an oil bath at 60 °C and continue to stir until the water is completely evaporated; after the water is completely evaporated, a brownish-green colloid is formed. Transfer the brownish-green colloid to a forced-air drying oven and dry it at 80 °C for 6 h to obtain the high-entropy oxide precursor;

[0048] S5. Coating of high-entropy oxide HEO-Ni on NNMO. Place the high-entropy oxide precursor in an agate mortar and grind it into fine powder. Then place the fine powder in a tube furnace and anneal it at 950 °C for 24 h to obtain the NNMO@HEO-Ni composite material.

[0049] Among them, the NNMO involved in the present invention is the abbreviation of the NaNi 0.5 Mn 0.5 O2 cathode material. The PTA involved in the present invention is terephthalic acid (Pure Terephthalic Acid); when preparing the O3-type NaNi 0.5 Mn 0.5 O2 material, it is necessary to calcine at two-stage temperatures to promote the complete chemical reaction and phase change inside the material. After cooling, the material needs to be placed in a glove box with an argon atmosphere; according to the different NNMO materials coated with high-entropy oxide HEO-Ni, they also need to be placed in a glove box with an argon atmosphere.

[0050] Among them, the present invention also discloses specific application examples 1-3 and comparative example 1. Examples 1-3 and comparative example 1 are distinguished according to the coating amounts of different high-entropy oxides HEO-Ni, as follows:

[0051] Table 1 Specific ratios of Examples 1-3 and comparative example

[0052]

[0053] It is understandable that taking NHEO-10 as an example, the present invention also includes the step of measuring the element content in NHEO-10, and deducing the element composition of NHEO-10 from the ICP-OES test results. As shown in the following table, the relative molar ratio of Na and Cu in the NHEO-10 material is 10:1. Also, based on the content of the Cu coating layer, it is inferred that HEO-Ni in the coating layer accounts for 10% of NNMO, which proves that the actually prepared composite material NHEO is consistent with that proposed in the original design.

[0054] The specific element content of NHEO-10 is shown in the following table:

[0055] Table 2 Specific elements of NHEO-10

[0056] Element Name Content Na 40.4％ Ni 27.9％ Mn 26.2％ Cu 3.9％ Fe 0.7％ Ti 0.6％ Mg 0.4％

[0057] As Figure 2 shown, the present invention conducted X-ray diffraction (XDR) experiments with Examples 1-3 and Comparative Example, and the specific experimental conclusions are as follows:

[0058] The two composite materials of NHEO-5 and NHEO-10 can well correspond to the O3-phase NNMO material, with the space group being the typical R3m and the standard card being JCPDS-54-0887. It is worth noting that for the NHEO-15 composite material, it can be seen that the main diffraction peak (003) has a significant left shift at 2θ = 16.8°, mainly due to the increase in the coating amount of the high-entropy oxide HEO-Ni, which indicates that the low coating amount of HEO-Ni has no effect on the NNMO structure. The high-entropy oxide-coated NNMO prepared by the sol-gel method in the present invention realizes good coating and mixing of the NNMO material.

[0059] As Figure 3 shown, the present invention conducted SEM images (scanning electron microscope), HRTEM images (high resolution transmission electron microscopy), and selected area electron diffraction patterns (SAED) with Examples 1-3 and Comparative Example 1, and the specific experimental conclusions are as follows:

[0060] As Figure 3As shown, the a-c subfigures in the figure are SEM images of NHEO-5, NHEO-10, and NHEO-15, and the d-f subfigures in the figure are HRTEM images of NHEO-5, NHEO-10, and NHEO-15; the g-i subfigures in the figure are selected area electron diffraction patterns of NHEO-5, NHEO-10, and NHEO-15.

[0061] Figure 3 In the a-c figures of, a composite material structure presenting a blocky layer structure can be clearly observed. From the SEM images, it can be observed that with the increase of the high-entropy oxide coating layer, there are some fine particles on the surface of the NNMO composite material, and the surface of NNMO is no longer smooth. As Figure 3 shown in Figure d, for the NHEO-5 material, a lattice spacing of (angstrom) can be observed at 5 nm, corresponding to the (110) crystal plane in the NNMO structure. At the same time, the thickness of the coating layer is about 2.18 nm. Some particles can also be observed on the surface of NHEO-5 under HRTEM characterization. In Figure 3 Figure e, it can be seen that the coating layer of NHEO-10 is significantly thicker, about 18.06 nm, and the thickness of the coating layer is basically consistent. The lattice spacing of the composite material is The lattice spacing is enlarged compared with that of NHEO-5, corresponding to the (012) crystal plane. At the same time, the particle distribution on the surface of the composite material is relatively uniform, and the surface NNMO is uniformly coated with the high-entropy oxide HEO-Ni. As Figure 3 shown in Figure f, after the coating layer is further increased, the lattice spacing of NHEO-15 shrinks, about corresponding to the (104) crystal plane. However, lattice fringes of the high-entropy oxide can be clearly seen in the coating layer outside NHEO-15, indicating that HEO-Ni is introduced into the NNMO material. As Figure 3 shown in g-i, Figure 3 g-i is the spot pattern of selected area electron diffraction observed along the

[010] zone axis of the composite material. Examples 1-3 all show clear (101) diffraction spots, indicating that this is a typical hexagonal structure with good crystallinity. It is proved that after the surface modification of NNMO, the composite materials in Examples 1-3 still maintain the hexagonal structure and have good crystallinity.

[0062] As Figure 4As shown, at a rate of 0.1C, NHEO-10 exhibits an excellent discharge specific capacity of 140.2 mAh / g, NHEO-15 has a discharge specific capacity of 112 mAh / g, NHEO-5 has a discharge specific capacity of 102 mAh / g, and NNMO has a discharge specific capacity of 95 mAh / g. It can be seen from the first charge-discharge curves that the discharge specific capacities of Examples 1-3 are all more excellent than those of the uncoated NNMO material in Comparative Example 1. The high-entropy oxide materials prepared by Ni-MOFs have more excellent electrochemical activity than the ordinary oxide coating layers in the prior art.

[0063] In the present invention, as Figure 5 shown, the tests were carried out at a rate of 0.1-5C. Taking Example 2 as an example, even at a rate of 5C, it still has a discharge specific capacity of 66.8 mAh / g. After 5 cycles at a rate of 5C and then back to a rate of 0.1C again, it still has a discharge specific capacity of 139.6 mAh / g, indicating that Example 2 has good reversibility, representing an increase in the sodium layer spacing, improving the diffusion rate of sodium ions, and optimizing the air sensitivity and kinetics.

[0064] As Figure 6 shown, the discharge specific capacities of Examples 1-3 after 100 cycles at a voltage range of 2-4V and at a rate of 0.1C. Among them, Example 2 has a discharge specific capacity of 67 mAh / g, while Comparative Example 1 is only 38 mAh / g.

[0065] Specifically, as Figure 7 shown, taking Example 2 as an example, in the high-rate test, in the voltage range of 2-4V and at a rate of 1C, a 200-cycle long-term cycling test was carried out. The capacity retention rate of Example 2 is 53.04%, while the capacity retention rate of the uncoated NNMO in Comparative Example 1 is only 25%. The cycle stability of Example 2 is improved by 28.04%.

[0066] Combining all the above examples, in the present invention, the O3-NaNi 0.5 Mn 0.5 O2 sodium-ion battery cathode material coated with Ni-MOFs high-entropy oxide is prepared by the sol-gel reaction and the matching low-temperature annealing treatment process. The XRD diffraction peaks of the high-entropy oxide coating material can completely correspond to those of the original material. At the same time, the lattice spacing of the material described in the present invention can be obtained through the high-resolution TEM image, proving that the trace high-entropy oxide coating does not affect the crystal structure of the material. And the O3-NaNi 0.5 Mn 0.5 O2 sodium-ion battery cathode material coated with Ni-MOFs high-entropy oxide exhibits excellent cycle performance, shortens the diffusion path of sodium ions, and shows excellent electrochemical performance.

[0067] The above are only the preferred embodiments of the present invention, and do not thereby limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method to improve NaNi 0.5 Mn 0.5 A coating modification method for improving the electrochemical performance of an O2 positive electrode material, characterized in that: The following steps are involved: Preparing a precursor solution, preparing a solution of DMF and PTA, preparing a solution of DMF and Ni(NO)3·6H2O, and mixing the two solutions to obtain a precursor solution; Prepare the precursor, pour the precursor solution into the reactor and react at 120°C for 12 hours. After the reaction, cool the solution to room temperature, centrifuge at 8500 rpm for 3 minutes, and dry it in a drying oven at 80°C for 6 hours to obtain the Ni-MOFs precursor; To prepare the O3 type material, 3.387 g Na2CO3, 2.24 g NiO and 2.61 g MnO2 reagents were weighed and ground, and then the ground particles were moved into a calcining furnace and heated at 500 °C for 12 h, and then heated to 900 °C for 12 h to obtain the O3 type material; A high entropy oxide precursor is prepared by weighing acetate, Ni-MOFs precursor, ferric nitrate and titanium dioxide, dissolving them, and then heating the solution to remove water and dry it to obtain a high entropy oxide precursor; High entropy oxide HEO-Ni coated NNMO, the high entropy oxide precursor was ground and heated to 950℃ and calcined for 24h to obtain NaNi 0.5 Mn 0.5 O2 positive electrode material.

2. The method for increasing NaNi as claimed in claim 1 0.5 Mn 0.5 A coating modification method for improving the electrochemical performance of an O2 positive electrode material, characterized in that: The step of preparing a precursor solution, preparing a solution of DMF and PTA, preparing a solution of DMF and Ni(NO)3·6H2O, and mixing the two solutions to obtain a precursor solution, further includes: Add 0.4984 g of PTA to 10-20 ml of DMF, then add 0.8724 g of Ni(NO)3·6H2O to 10 ml of DMF, and stir the two solutions for 5-10 min respectively; The two solutions are mixed to obtain a precursor solution.

3. Raising NaNi as claimed in claim 2 0.5 Mn 0.5 A coating modification method for improving the electrochemical performance of an O2 positive electrode material, characterized in that: The step of mixing the two solutions to obtain a precursor solution also includes: The PTA solution was slowly poured into the Ni(NO)3·6H2O solution and stirred continuously at 350 rpm for 30 min to obtain a transparent turquoise mixed solution; The mixed solution was transferred to the inner lining of the reactor and heated to 120°C for 12 h; After the reaction, the mixed solution was cooled to room temperature, transferred to a centrifuge and centrifuged at 8500 rpm for 3 min; During the centrifugation, the mixture was washed alternately with anhydrous ethanol and deionized water, and then transferred to a centrifuge for centrifugation. After centrifugation for 3 times, the mixture was transferred to a drying oven at 80° C. and dried for 6 h to obtain a Ni-MOFs precursor.

4. The method for increasing NaNi as claimed in claim 1 0.5 Mn 0.5 A coating modification method for improving the electrochemical performance of an O2 positive electrode material, characterized in that: The step of preparing the high entropy oxide precursor, weighing acetate, Ni-MOFs precursor, ferric nitrate and titanium dioxide to dissolve, and then heating the solution to remove water and dry to obtain the high entropy oxide precursor, also includes: Acetate, Ni-MOFs precursor, ferric nitrate and titanium dioxide were weighed and dissolved in deionized water with citric acid at a molar ratio of 1 times that of HEO-Ni, and stirred at room temperature for 30 min; After adding the corresponding molar mass of bare NNMO to the above solution according to the surface coating amount, the mixed solution was transferred to an oil bath at 60°C and stirred continuously until the water was completely evaporated; After the water is completely evaporated, a brown-green colloid is formed. The brown-green colloid is moved to a forced air drying oven and dried at 80° C. for 6 h to obtain a high entropy oxide precursor.

5. The method for increasing NaNi as claimed in claim 4 0.5 Mn 0.5 A coating modification method for improving the electrochemical performance of an O2 positive electrode material, characterized in that: The acetate includes: manganese acetate, copper acetate, magnesium acetate and sodium acetate.

6. The method for increasing NaNi as claimed in claim 1 0.5 Mn 0.5 A coating modification method for improving the electrochemical performance of an O2 positive electrode material, characterized in that: The high entropy oxide HEO-Ni is coated with NNMO, and the high entropy oxide precursor is ground and heated to 950° C. and calcined for 24 hours to obtain NaNi 0.5 Mn 0.5 The step of O2 cathode material also includes: The high entropy oxide precursor was placed in an agate mortar and ground into fine powder, and then the fine powder was placed in a tube furnace and annealed by calcining at 950°C for 24 hours to obtain the NNMO@HEO-Ni composite material.

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