Modified sodium-ion battery cathode material, preparation method thereof and battery

Abstract

The application discloses a modified sodium ion battery positive electrode material and a preparation method and a battery thereof, and the preparation method comprises the following steps: adding an alkali metal salt into an organic solvent solution, stirring and dissolving to obtain an alkali metal salt solution; adding a sodium ion battery oxide positive electrode material powder into the alkali metal salt solution, stirring to make the two fully contact and perform ion exchange; performing suction filtration separation, cleaning a filter cake, and then drying to obtain a modified sodium ion battery positive electrode material with an alkali metal ion exchanged surface interface; wherein the alkali metal salt is at least one of a nitrate, an acetate, a sulfate and a chloride containing an alkali metal, the alkali metal comprises at least one of Li, Cs and K, the battery is a sodium ion battery, and the positive electrode of the battery is made of the modified sodium ion battery positive electrode material; the modified sodium ion battery positive electrode material prepared by the method has the advantages of long cycle life and high reversible specific capacity, and the surface interface of the modified sodium ion battery positive electrode material is relatively uniform and stable after being constructed.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a modified sodium ion battery positive electrode material, a preparation method thereof, and a battery. Background Art

[0002] As new renewable energy sources increase their share of the energy system, their development and utilization have become the energy foundation for scientific and industrial development in various countries. However, due to the dispersed and intermittent nature of these new energy sources, the development of energy storage batteries is crucial for grid-connected energy applications and peak-shaving. Currently, commercial lithium-ion batteries are primarily used in the power battery sector. Due to the relative scarcity of lithium resources and their limited distribution in my country, there is a high degree of external dependence, which hinders the promotion and application of large-scale energy storage technologies. To ensure national energy security and meet the needs of the vast energy storage market, the development of sodium-ion batteries, which are resource-rich (ranking sixth in the Earth's crust in terms of elemental abundance) and low cost, has become the key to technological breakthroughs. One of the key technical challenges in the application of sodium-ion batteries is the development of high-performance cathode materials, which is primarily determined by key performance indicators such as energy density, cost, and cycle life. Layered oxide cathodes offer advantages over other cathode materials, including high specific energy, high tap density, and ease of scalable preparation, making them a crucial component of the industrial development of sodium-ion batteries.

[0003] In practical applications, sodium ion battery cathode materials often exhibit problems such as poor interface stability, reduced cycle life and reduced energy density due to structural instability and low solvation ability of sodium ions. To address such problems, interface coating to reduce the contact between the "cathode-electrolyte" and ion doping to improve structural stability are commonly used modification methods. Compared with the introduction of heterogeneous atoms in the precursor stage, the post-processing of the finished oxide product only involves the regulation of the interface layer, which is lower in cost and more applicable. However, the sensitivity of oxide cathode materials to air humidity can easily lead to problems such as sodium ion dissolution and structural collapse. Conventional modification methods are mostly based on solid-phase sintering to avoid the influence of water. For example, Chinese patent CN115763768A discloses a sodium ion battery cathode material and its preparation method and application, which is achieved by mixing the raw materials of the coating with the oxide and then ball milling and calcining. However, the solid-phase reaction has the characteristic of uneven "solid-solid" contact, which is not conducive to the construction of a uniform interface and is not conducive to reducing interface side reactions. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the background technology and to provide a modified sodium ion battery positive electrode material, a preparation method thereof, and a battery.

[0005] To achieve the above object, the present invention proposes a method for preparing a modified sodium ion battery cathode material, comprising the following steps:

[0006] Adding an alkali metal salt to an organic solvent solution, stirring and dissolving the solution to obtain an alkali metal salt solution;

[0007] Adding sodium ion battery oxide positive electrode material powder to the alkali metal salt solution and stirring to ensure full contact between the two for ion exchange;

[0008] The solid and liquid phases are separated by suction filtration, and the filter cake is washed and dried to obtain a modified sodium ion battery positive electrode material with alkali metal ion exchange on the surface;

[0009] The alkali metal salt is at least one of nitrate, acetate, sulfate, and chloride containing an alkali metal, the alkali metal includes at least one of Li, Cs, and K, and the chemical formula of the sodium ion battery oxide positive electrode material powder is Na x Ni y Mn z Me w O2,Me is selected from at least one of Fe, Mg, Al, Cu, Co, Sn, Ti and Zn, wherein 0.67≤x≤1, 0≤y≤0.5, 0.3≤z≤0.6, 0≤w≤0.4, y+z+w=1.

[0010] Preferably, the concentration of the alkali metal salt solution is 0 to 3 mol / L.

[0011] Preferably, the organic solvent solution is formed by mixing water and an organic solvent, and the organic solvent includes at least one of methanol, ethanol, glycerol, acetonitrile and acetone.

[0012] Preferably, the mass-to-liquid ratio of the sodium ion battery oxide positive electrode material powder to the alkali metal salt solution is 0-1 kg / L.

[0013] Preferably, the filter cake after the suction filtration separation is washed three times with anhydrous ethanol.

[0014] Preferably, the filter cake is dried in a drying oven at a temperature of 40 to 150°C.

[0015] Preferably, the stirring time is 0 to 1 hour.

[0016] Preferably, the alkali metal salt is one of lithium nitrate, lithium acetate, lithium sulfate and lithium chloride, and the concentration of the alkali metal salt solution is 0.5 mol / L or 1 mol / L.

[0017] The present invention also provides a modified sodium ion battery positive electrode material prepared according to the above-mentioned preparation method of the modified sodium ion battery positive electrode material.

[0018] The present invention also provides a battery, which is a sodium ion battery, and the positive electrode of the battery is made of the above-mentioned modified sodium ion battery positive electrode material.

[0019] The beneficial effects of the present invention are as follows: the present invention fully mixes and contacts an alkali metal salt solution of a liquid phase system with a sodium ion battery oxide positive electrode material powder, and combines ion exchange technology to allow the alkali metal ions in the alkali metal salt solution to replace part of the sodium ions in the sodium ion battery oxide positive electrode material powder, so that the surface interface of the modified sodium ion battery positive electrode material is relatively uniform and stable after construction, effectively reducing the interfacial instability problem caused by low solvation of sodium ions, and improving the interfacial stability of the sodium ion battery oxide positive electrode material powder; the modified sodium ion battery positive electrode material prepared by this method has the advantages of long cycle life and high reversible specific capacity. Using this material to prepare the positive electrode of a sodium ion battery can effectively increase the service life of the battery.

[0020] The features and advantages of the present invention will be described in detail through embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Transmission electron microscope images of different sodium ion battery positive electrode materials according to embodiments of the present invention.

[0022] Figure 2 Surface morphologies of different sodium ion battery cathode materials according to embodiments of the present invention.

[0023] Figure 3 This is a cycle performance diagram of different sodium ion battery positive electrode materials according to an embodiment of the present invention.

[0024] Figure 4 Surface morphology of modified sodium ion battery positive electrode materials prepared with different solvents according to the embodiments of the present invention.

[0025] Figure 5 This is a cycle performance diagram of the modified sodium ion battery positive electrode material prepared with different solvents in the embodiments of the present invention.

[0026] Figure 6 This is a cycle performance diagram of modified sodium ion battery positive electrode materials prepared from different alkali metal salts in the embodiments of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0028] The present invention will be described in detail below with reference to the accompanying drawings.

[0029] Example 1

[0030] This embodiment provides a method for preparing a modified sodium ion battery cathode material, comprising the following steps:

[0031] S01 lithium acetate was added to an organic solvent solution of water and ethanol, and the mixture was stirred and dissolved to obtain a lithium acetate solution having a concentration of 0.5 mol / L;

[0032] S02. Take 1 mL of lithium acetate solution and add the chemical formula Na 0.8 Ni 1 / 3 Mn 1 / 3 Fe 1 / 3 O2 sodium ion battery oxide positive electrode material powder, stirring for 5 minutes to allow the two to fully contact and perform ion exchange;

[0033] S03. The solid and liquid phases were separated by filtration, and the mixture was washed three times with anhydrous ethanol. The filter cake was placed in a forced air drying oven and dried at 80°C to obtain a modified sodium ion battery positive electrode material with interfacial Li / Na ion exchange.

[0034] This embodiment also provides a battery, which is a sodium ion battery. The positive electrode of the battery is made of the modified sodium ion battery positive electrode material prepared by the above preparation method. When preparing the sodium ion battery positive electrode, the modified sodium ion battery positive electrode material is ground and fully mixed with conductive carbon black (conductive agent), polyvinylidene fluoride (PVDF binder), and a small amount of N-methylpyrrolidone (NMP) to form a uniform slurry. The slurry is coated on an aluminum foil substrate as a test electrode. The electrolyte of the sodium ion battery is 1MNaPF6 / PC:EMC (V:V=50:45)+5%FEC, and a button battery is prepared using a metal sodium sheet as a counter electrode.

[0035] Example 2

[0036] This embodiment provides a method for preparing a modified sodium ion battery positive electrode material. Except that the concentration of the lithium acetate solution in step S01 is changed to 1 mol / L, the remaining steps are the same as those in Example 1.

[0037] This embodiment also provides a battery, which is a sodium ion battery. The positive electrode of the battery is made of the modified sodium ion battery positive electrode material prepared by the above preparation method. The preparation method of the positive electrode of the sodium ion battery and the battery composition are also the same as those in Example 1.

[0038] Example 3

[0039] This embodiment provides a method for preparing a modified sodium ion battery positive electrode material. Except that the concentration of the lithium acetate solution in step S01 is changed to 2 mol / L, the remaining steps are the same as those in Example 1.

[0040] This embodiment also provides a battery, which is a sodium ion battery. The positive electrode of the battery is made of the modified sodium ion battery positive electrode material prepared by the above preparation method. The preparation method of the positive electrode of the sodium ion battery and the battery composition are also the same as those in Example 1.

[0041] Example 4

[0042] This embodiment provides a method for preparing a modified sodium ion battery positive electrode material. Except that the concentration of the lithium acetate solution in step S01 is changed to 0.1 mol / L, the remaining steps are the same as those in Example 1.

[0043] This embodiment also provides a battery, which is a sodium ion battery. The positive electrode of the battery is made of the modified sodium ion battery positive electrode material prepared by the above preparation method. The preparation method of the positive electrode of the sodium ion battery and the battery composition are also the same as those in Example 1.

[0044] Example 5

[0045] This embodiment provides a method for preparing a modified sodium ion battery positive electrode material, except that in step S01, lithium nitrate is added to an organic solvent solution prepared by mixing water, ethanol and glycerol, and the mixture is stirred and dissolved to obtain a lithium nitrate solution with a concentration of 0.5 mol / L. In step S02, 1 mL of the lithium nitrate solution is taken and a chemical formula of Na is added to the lithium nitrate solution. 0.8 Ni 1 / 3 Mn 1 / 3 Fe 1 / 3 The sodium ion battery oxide positive electrode material powder of O2 is dried at 100°C in step S03, and the remaining steps are the same as those in Example 1.

[0046] This embodiment also provides a battery, which is a sodium ion battery. The positive electrode of the battery is made of the modified sodium ion battery positive electrode material prepared by the above preparation method. The preparation method of the positive electrode of the sodium ion battery and the battery composition are also the same as those in Example 1.

[0047] Example 6

[0048] This embodiment provides a method for preparing a modified sodium ion battery positive electrode material, except that in step S01, lithium acetate and cesium acetate are added to an organic solvent solution prepared by mixing water, ethanol and methanol, and the mixture is stirred and dissolved to obtain a 0.5 mol / L lithium acetate and cesium acetate mixed solution, and in step S02, 1 mL of the lithium acetate and cesium acetate mixed solution is taken and a chemical formula of Na is added to the lithium acetate and cesium acetate mixed solution. 0.8 Ni 1 / 3 Mn 1 / 3 Fe 1 / 3 The remaining steps are the same as those in Example 1.

[0049] This embodiment also provides a battery, which is a sodium ion battery. The positive electrode of the battery is made of the modified sodium ion battery positive electrode material prepared by the above preparation method. The preparation method of the positive electrode of the sodium ion battery and the battery composition are also the same as those in Example 1.

[0050] Example 7

[0051] This embodiment provides a method for preparing a modified sodium ion battery positive electrode material, except that the chemical formula of the sodium ion battery oxide positive electrode material powder in step S01 is Na 0.9 Ni 0.4 Mn 0.3 Ti 0.3 O2, the remaining steps are the same as in Example 1.

[0052] This embodiment also provides a battery, which is a sodium ion battery. The positive electrode of the battery is made of the modified sodium ion battery positive electrode material prepared by the above preparation method. The preparation method of the positive electrode of the sodium ion battery and the battery composition are also the same as those in Example 1.

[0053] Example 8

[0054] This comparative example provides a method for preparing a modified sodium ion battery positive electrode material. Except that lithium chloride is used instead of lithium acetate in step S01, the remaining steps are the same as those in Example 1.

[0055] This reference example also provides a sodium ion battery, the positive electrode of the battery is made of the modified sodium ion battery positive electrode material prepared by the preparation method of this reference example, and the positive electrode preparation method and battery composition of the sodium ion battery are also the same as those in Example 1.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing a positive electrode material for a sodium ion battery. The steps are the same as those in Example 3, except that in step S01, lithium acetate is added to anhydrous ethanol and thoroughly stirred and dissolved to obtain a 2 mol / L lithium acetate mixture. No ion exchange occurs on the surface of the sodium ion battery oxide positive electrode material in an anhydrous ethanol environment.

[0058] This reference example also provides a sodium ion battery, the positive electrode of the battery is made of the sodium ion battery positive electrode material prepared by the preparation method of this reference example, and the preparation method of the positive electrode of the sodium ion battery and the battery composition are also the same as those in Example 3.

[0059] 1. Test on the Effect of Modification Treatment on the Performance of Sodium-ion Battery Cathode Materials

[0060] 1). The positive electrodes of the sodium ion battery of Example 1 (sodium ion battery oxide positive electrode material subjected to ion exchange modification), the sodium ion battery of Example 2 (sodium ion battery oxide positive electrode material subjected to ion exchange modification), the sodium ion battery of Example 3 (sodium ion battery oxide positive electrode material subjected to ion exchange modification) and the existing sodium ion battery (sodium ion battery oxide positive electrode material not subjected to ion exchange modification) were cycled for 300 cycles in the voltage range of 2.5 to 4.1 V (current density: 1C = 130 mA / g), and the electrochemical performance of the battery positive electrode material was tested. The specific test results are shown in Table 1 and Figure 3 、 Figure 5 shown.

[0061] Table 1 Schematic diagram of electrochemical performance of different sodium ion batteries

[0062]

[0063] From Table 1 and Figure 3 、 Figure 5 It can be seen that the modified sodium ion battery positive electrode material of the sodium ion battery of Example 1 retains a reversible specific capacity of 94.8 mAh / g and a capacity retention rate of 82.1% after cycling for 300 cycles in the voltage range of 2.5 to 4.1 V; the modified sodium ion battery positive electrode material of the sodium ion battery of Example 2 retains a reversible specific capacity of 88.4 mAh / g and a capacity retention rate of 69.1% after cycling for 300 cycles in the voltage range of 2.5 to 4.1 V; the modified sodium ion battery of Example 3 retains a reversible specific capacity of 88.4 mAh / g and a capacity retention rate of 69.1%. The positive electrode material retains a reversible specific capacity of 87.2 mAh / g and a capacity retention rate of 66.4% after cycling for 300 cycles in the voltage range of 2.5 to 4.1 V; the sodium ion battery oxide positive electrode material of the existing sodium ion battery retains a reversible specific capacity of only 77.4 mAh / g and a capacity retention rate of 63.4% after cycling for 300 cycles in the voltage range of 2.5 to 4.1 V. Although its capacity in the first week is relatively high, it is affected by interfacial side reactions and the capacity after 300 cycles is only 77.4 mAh / g.

[0064] This shows that the sodium ion battery oxide positive electrode material is modified by ion exchange, and since part of the sodium ions of the sodium ion battery positive electrode material are replaced by lithium ions, the stability of the modified sodium ion battery oxide positive electrode material under long cycles is significantly improved. In addition, although the concentration of the alkali metal salt solution used in the preparation of the modified sodium ion battery positive electrode material is an important parameter affecting the interface ion exchange rate, under the same immersion time, a higher concentration of lithium salt is conducive to accelerating the interface ion exchange rate, but in the actual test process, the modified sodium ion battery positive electrode material of Example 1 and Example 2 retains the reversible specific capacity and capacity retention rate after 300 cycles in the voltage range of 2.5 to 4.1 V compared with Example 3. It can be seen that in a specific alkali metal salt concentration range (0.5 to 1 mol / L), the cycle performance of the prepared modified sodium ion battery positive electrode material is better, mainly due to the influence of ion diffusion at the interface. Excessive ion exchange may be detrimental to the improvement of stability. Excessive ion exchange will cause lattice distortion at the interface of the positive electrode material after ion exchange.

[0065] 2) Take equal amounts of the modified sodium ion battery cathode material prepared in Example 1 and the existing unmodified sodium ion battery oxide cathode material, respectively, as transmission electron microscope samples placed in a transmission electron microscope for observation, and obtain the following Figure 1 Transmission electron microscopy image of the sample interface shown.

[0066] Figure 1 Figure a is a transmission electron micrograph of the interface of an existing unmodified sodium ion battery oxide cathode material, and Figure b is a transmission electron micrograph of the interface of a modified sodium ion battery cathode material. Since sodium ion battery oxide cathode materials are highly sensitive to humidity, sodium ions often precipitate on their surfaces to form sodium carbonate or sodium bicarbonate, forming a certain hydrated desodium phase. Figure 1 It can be seen from a that the interface of the existing unmodified sodium ion battery cathode material is in contact with the air more, showing more obvious cracks (such as Figure 1 As shown in the marked Ⅰ and Ⅱ in a), the larger interlayer spacing is mainly affected by the insertion of hydrogen protons into the interlayer. Figure 1 The modified sodium ion battery positive electrode material after ion exchange in b maintains a relatively consistent layered structure in the bulk and interface.

[0067] The surface morphology of the sodium ion battery positive electrode material was further observed. The modified sodium ion battery positive electrode material prepared in Example 1 and the existing unmodified sodium ion battery oxide positive electrode material were placed in a scanning electron microscope to observe the surface morphology of each material. The specific observation results are as follows: Figure 2 shown.

[0068] Figure 2Figure a shows the surface morphology of the unmodified sodium ion battery oxide cathode material, and Figure b shows the surface morphology of the modified sodium ion battery cathode material. Figure 2 It can be seen that the existing unmodified sodium-ion battery oxide positive electrode material maintains a relatively smooth surface, while the surface of the modified sodium-ion battery positive electrode material after the ion exchange reaction is relatively rough, which proves that certain chemical reactions occur at the interface during the ion exchange process, and there is a certain lattice distortion near the surface due to the structural evolution of the ion exchange process.

[0069] 2. Test on the influence of different solvents on the performance of sodium ion batteries during the preparation process

[0070] 1) Morphology observation: The modified sodium ion battery cathode material prepared in Example 3 and the modified sodium ion battery cathode material prepared in Comparative Example 1 were placed in a scanning electron microscope to observe the surface morphology of each material. The specific observation results are as follows: Figure 4 shown

[0071] Figure 4 Figure a shows the surface morphology of the modified sodium ion battery cathode material of Example 3, and Figure b shows the surface morphology of the sodium ion battery cathode material of Comparative Example 1. Figure 4 It can be seen that under anhydrous conditions, despite the high lithium salt concentration, the surface of the modified sodium ion battery cathode material prepared in Control Example 1 remains smooth, and its morphology is relatively close to that of the unmodified sodium ion battery oxide cathode material. In the presence of water, the surface of the modified sodium ion battery cathode material prepared in Example 3 exhibits greater roughness. It can be seen that although sodium ion battery cathode materials are highly sensitive to water, the introduction of appropriate water can promote the occurrence of ion exchange reactions to a certain extent.

[0072] 2) The positive electrodes of the sodium ion battery prepared in Example 3, the sodium ion battery prepared in Comparative Example 1, and the existing sodium ion battery (the sodium ion battery oxide positive electrode material has not been subjected to ion exchange modification) were cycled for 300 cycles in the voltage range of 2.5 to 4.1 V (current density: 1C = 130 mA / g), and the electrochemical performance of the battery positive electrode materials was tested. The specific test results are as follows: Figure 5 shown.

[0073] Depend on Figure 5It can be seen that despite the same lithium salt concentration and immersion time, the modified sodium-ion battery cathode material treated in an ethanol / water mixed solvent exhibited superior cycling stability after 300 cycles compared to the unmodified sodium-ion battery oxide cathode material. The sodium-ion battery oxide cathode material treated in anhydrous ethanol exhibited faster performance degradation after 300 cycles. This indicates that under anhydrous conditions, ion exchange is relatively slow, the interfacial modification effect is poor, and the solvent has a certain influence on the ion release of the sodium-ion battery oxide cathode material. The alkali metal salt solution prepared by dissolving the alkali metal salt in an organic solvent solution according to the present invention is more easily ion-exchanged when mixed with the sodium-ion battery oxide cathode material.

[0074] 3. Test on the influence of different alkali metal salts on sodium ion battery performance during the preparation process

[0075] The positive electrodes of the sodium ion battery prepared in Example 1, the sodium ion battery prepared in Example 8, and the existing sodium ion battery (the sodium ion battery oxide positive electrode material has not been subjected to ion exchange modification) were cycled for 300 cycles in the voltage range of 2.5 to 4.1 V (current density: 1C = 130 mA / g), and the electrochemical performance of the battery positive electrode materials was tested. The specific test results are as follows: Figure 6 shown.

[0076] Depend on Figure 6 The modified sodium-ion battery cathode material treated with 0.5M lithium acetate solution exhibited significantly improved cycling stability after 300 cycles compared to the unmodified sodium-ion battery oxide cathode material. The modified sodium-ion battery cathode material treated with 0.5M lithium chloride solution exhibited rapid performance degradation in the initial stage, but its cycling stability after 300 cycles was also significantly improved compared to the unmodified sodium-ion battery oxide cathode material. The modified sodium-ion battery cathode material treated with 0.5M lithium acetate solution exhibited superior performance stability compared to the modified sodium-ion battery cathode material treated with 0.5M lithium chloride solution. The difference in electrochemical performance of the cathode materials treated with LiCl and LiAc under the same conditions is primarily due to the fact that acetate ions dissociate and bind to some hydrogen protons in water, inhibiting the release of free protons in water and resulting in superior stability compared to chloride salts. This indicates that under the same lithium salt exchange conditions, the choice of lithium salt also has a significant impact on the performance of modified sodium-ion battery cathode materials, and the design of the lithium salt can also regulate sodium ion dissolution.

[0077] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention falls within the protection scope of the present invention.

Claims

1. A method for preparing a modified sodium ion battery cathode material, characterized in that: It includes the following steps: Adding an alkali metal salt to an organic solvent solution, stirring and dissolving the solution to obtain an alkali metal salt solution; Adding sodium ion battery oxide positive electrode material powder to the alkali metal salt solution and stirring to ensure full contact between the two for ion exchange; The solid and liquid phases are separated by filtration, and the filter cake is washed and dried to obtain a modified sodium ion battery positive electrode material with alkali metal ion exchange on the surface; The alkali metal salt is at least one of nitrate, acetate, sulfate, and chloride containing an alkali metal, the alkali metal includes at least one of Li, Cs, and K, and the chemical formula of the sodium ion battery oxide positive electrode material powder is Na x Ni y Mn z Me w O2, Me is selected from at least one of Fe, Mg, Al, Cu, Co, Sn, Ti and Zn, wherein 0.67≤x≤1, 0<y≤0.5, 0.3≤z≤0.6, 0<w≤0.4, y+z+w=1, the concentration of the alkali metal salt solution is greater than 0 mol / L and less than or equal to 3 mol / L, the organic solvent solution is formed by mixing water and an organic solvent, and the mass-to-liquid ratio of the sodium ion battery oxide positive electrode material powder to the alkali metal salt solution is greater than 0 kg / L and less than or equal to 1 kg / L.

2. The method for preparing a modified sodium ion battery cathode material according to claim 1, wherein: The organic solvent includes at least one of methanol, ethanol, glycerol, acetonitrile and acetone.

3. The method for preparing the modified sodium ion battery positive electrode material according to claim 1, wherein: The filter cake after filtration separation was washed three times with anhydrous ethanol.

4. The method for preparing the modified sodium ion battery positive electrode material according to claim 1, wherein: The filter cake is dried in a drying oven at a temperature of 40°C to 150°C.

5. The method for preparing the modified sodium ion battery positive electrode material according to claim 1, wherein: The stirring time is greater than 0 h and less than or equal to 1 h.

6. The method for preparing a modified sodium ion battery cathode material according to claim 1, wherein: The alkali metal salt is one of lithium nitrate, lithium acetate, lithium sulfate, and lithium chloride, and the concentration of the alkali metal salt solution is 0.5 mol / L or 1 mol / L.

7. A modified sodium ion battery positive electrode material obtained by the preparation method of the modified sodium ion battery positive electrode material according to any one of claims 1 to 6.

8. A battery, characterized in that: The battery is a sodium ion battery, and the positive electrode of the battery is made of the modified sodium ion battery positive electrode material according to claim 7.

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