Coated quaternary sodium electric precursor material as well as preparation method and application thereof

Abstract

The invention provides a coated quaternary sodium electric precursor material and a preparation method and application thereof, and the preparation method comprises the following steps: introducing a nickel-iron-manganese mixed salt solution, an aluminum source solution, a precipitator solution and a complexing agent solution into a base solution, and carrying out a co-precipitation reaction to obtain an inner core precursor material; the aluminum source solution comprises meta-aluminate, a precipitator and a complexing agent; after feeding is stopped and the pH value of the system is regulated and controlled, a coating metal source solution is introduced for a coating reaction, and the coated quaternary sodium electric precursor material is obtained; the coating metal source solution comprises a complexing agent. According to the preparation method disclosed by the invention, the composition of the aluminum source solution and the coating metal source solution is controlled during the coprecipitation reaction, so that uniform distribution of various elements can be realized, meanwhile, a uniform and stable coating layer is formed, and the stability and the cycle performance of the material are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a coated quaternary sodium battery precursor material and a preparation method and application thereof. Background Art

[0002] With the continuous increase in the use of lithium-ion batteries, the prices of key materials for lithium-ion batteries, such as lithium, nickel, and cobalt, have continued to rise. Price factors have, to a certain extent, restricted the development of lithium-ion batteries. Sodium-ion batteries are currently recognized as one of the more ideal alternative energy sources to lithium-ion batteries. On the one hand, sodium and lithium belong to the same main group and have similar physical and chemical properties and electrochemical reaction mechanisms. On the other hand, compared with lithium-ion batteries, sodium-ion batteries have the advantages of abundant resources, low prices, and wide distribution. Therefore, sodium-ion batteries have gradually become a research hotspot in the field of energy storage. Because sodium ions have a large ionic radius and slow kinetic rate, it is difficult for sodium ions to intercalate and deintercalate in the positive electrode material. The capacity of the positive electrode material determines the overall cell capacity of the sodium-ion battery. Therefore, the preparation of sodium-ion battery positive electrode materials with better performance is of great significance to promoting the commercial application of sodium-ion battery positive electrode materials.

[0003] Layered metal oxide cathode materials are currently a common type of sodium ion cathode material. Currently, layered transition metal oxide materials are mainly prepared by a high-temperature solid-phase method, in which sodium salts and transition metal oxides are mixed and then sintered at high temperature. However, the products obtained by this traditional method contain impurities and form secondary polycrystalline particles with agglomerated nanoparticles. At the same time, due to the large specific surface area and many side reactions, the secondary particle structure is prone to cracking and damage during long-term charge and discharge cycles, thereby reducing the cycle stability performance and severely limiting its application in sodium ion battery cathode materials.

[0004] For example, CN 119191387A discloses a high-capacity layered cathode material for sodium ion batteries, its preparation method, and application. The preparation method comprises: uniformly mixing a sodium source, a nickel source, an iron source, a manganese source, an aluminum source, and an antimony source to obtain a precursor powder, wherein, by molar mass, the ratio of sodium in the sodium source, nickel in the nickel source, iron in the iron source, manganese in the manganese source, aluminum in the aluminum source, and antimony in the antimony source is (0.88-1):0.35:0.2:0.4:0.025:0.025; and sintering the precursor powder at 600-1200°C for 6-24 hours to obtain a high-capacity layered cathode material for sodium ion batteries. The layered oxide cathode material obtained by this method through high-temperature solid-phase sintering has a high number of impurities and difficult-to-control particle morphology. During long-term charge-discharge cycles, side reactions are numerous, secondary particles are prone to cracking, and cycle stability is poor.

[0005] A sodium ion positive electrode material precursor is prepared by a coprecipitation method, and then the precursor is calcined with a sodium salt at high temperature to obtain a layered positive electrode material with uniform element distribution, good sphericity, and excellent electrochemical energy. For example, CN 119008919A discloses a modified sodium ion battery positive electrode material, a preparation method thereof, and a sodium ion battery. The disclosed modified sodium ion battery positive electrode material includes a sodium ion battery positive electrode material substrate and a coating layer located on at least a portion of the surface of the substrate, wherein the coating layer is titanium nitride coated with titanium nitride chloride. The modified positive electrode material provided herein uses titanium nitride chloride @ titanium nitride coating layer to coat and modify the sodium ion battery positive electrode material, which can significantly improve the structural stability and electrical performance of the sodium ion battery positive electrode material, reduce capacity decay, and increase the cycle life of the battery. However, the price of the coating layer material titanium used in this method is too high, making it difficult to apply on a large scale.

[0006] Based on the above research, it is necessary to provide a method for preparing a sodium battery precursor material, which can obtain a precursor material with uniform element distribution, excellent performance and industrial application. Summary of the Invention

[0007] The purpose of the present invention is to provide a coated quaternary sodium electrode precursor material, a preparation method and an application thereof. The preparation method can achieve uniform distribution of multiple elements by controlling the composition of the aluminum source solution and the coating metal source solution during the co-precipitation reaction, while also forming a uniform and stable coating layer, thereby improving the stability and cycle performance of the material.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a coated quaternary sodium electrolyte precursor material. The preparation method comprises the following steps:

[0010] (1) introducing a nickel-iron-manganese mixed salt solution, an aluminum source solution, a precipitant solution, and a complexing agent solution into a bottom solution to perform a coprecipitation reaction to obtain a core precursor material;

[0011] The aluminum source solution includes metaaluminate, a precipitant and a complexing agent;

[0012] (2) after stopping the feeding and adjusting the pH value of the system, introducing the coating metal source solution to carry out the coating reaction to obtain the coated quaternary sodium electrode precursor material;

[0013] The coating metal source solution includes a complexing agent.

[0014] The present invention realizes the co-precipitation of nickel, iron, manganese and aluminum, so that the four elements are evenly distributed, wherein the aluminum source solution is an aluminate solution containing a precipitant and a complexing agent, which is obtained by mixing an aluminum salt and an excess precipitant solution and then adding a complexing agent solution. The role of the precipitant in the aluminum source solution is to ensure the stability of the aluminate and to avoid the formation of free aluminum ions, thereby making the aluminum element distribution of the solution more even during the co-precipitation reaction. The role of the complexing agent is to regulate the complexing agent concentration of the aluminum source solution within a reasonable range and to reduce the fluctuation of the complexing agent concentration in the reactor when the aluminum source solution enters the reactor. After the co-precipitation reaction of the present invention, the feeding is stopped and the pH value of the system is regulated, and then a coating metal source solution is introduced to carry out a coating reaction. The coating metal source solution includes a complexing agent, which can maintain the complexing agent concentration of the coating metal source solution within a reasonable range and reduce the fluctuation of the complexing agent concentration in the reactor when the solution enters the reactor, thereby obtaining a stable and uniform coating layer. Therefore, the present invention can improve the circulation performance of the material through uniform co-precipitation and uniform coating.

[0015] Preferably, the pH of the aluminum source solution in step (1) is 9-12, for example, 9, 10, 11 or 12, and the concentration of the complexing agent is 1-10 g / L, for example, 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] The pH of the aluminum source solution and the concentration of the complexing agent of the present invention affect the co-precipitation of the elements. If the pH is too low, the conversion of aluminum ions into aluminate ions will not be complete, affecting the uniform distribution of the aluminum element. If the pH is too high, the pH of the system will be too high after the aluminum source solution is added during the reaction, affecting the stability of the entire reaction. If the concentration of the complexing agent in the aluminum source solution is too low or too high, the concentration of the complexing agent in the reactor will fluctuate, affecting the normal progress of subsequent reactions.

[0017] Preferably, the method for preparing the aluminum source solution in step (1) comprises: mixing an aluminum salt and an excess precipitant solution to obtain a metaaluminate solution, and then adding a complexing agent solution to obtain the aluminum source solution.

[0018] Preferably, the pH of the coprecipitation reaction in step (1) is 7.5-12, for example, 7.5, 8, 9, 10, 11 or 12, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the temperature of the coprecipitation reaction in step (1) is 20-65°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C or 65°C, and the stirring speed is 100-1500rpm, for example, 100rpm, 500rpm, 1000rpm or 1500rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the coprecipitation reaction in step (1) is carried out under a protective atmosphere.

[0021] Preferably, the protective atmosphere comprises nitrogen.

[0022] Preferably, the total metal ion concentration of the nickel-iron-manganese mixed salt solution in step (1) is 0.1-5 mol / L, for example, it can be 0.1 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] Preferably, the nickel-iron-manganese mixed salt solution in step (1) is prepared by mixing soluble salt with water, and the soluble salt includes any one of sulfate, nitrate or chloride, or a combination of at least two of them.

[0024] Preferably, the pH of the base solution in step (1) is 7.5-11, for example, 7.5, 8, 9, 10 or 11, and the concentration of the complexing agent is 0.1-10 g / L, for example, 0.1 g / L, 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, oxygen is first removed from the base liquid in step (1) before the nickel-iron-manganese mixed salt solution, aluminum source solution, precipitant solution and complexing agent solution are introduced.

[0026] Preferably, the method for removing oxygen from the bottom liquid includes removing oxygen from the reaction vessel by physical means (such as passing high-purity nitrogen, deoxygenating with a deoxygenator, etc.), or by chemical means, adding an appropriate amount of a reducing agent such as sodium sulfite, hydrazine hydrate or VC to the bottom liquid in advance to consume the oxygen in the reaction vessel to prevent the metal ions from being oxidized by oxygen during the reaction.

[0027] Preferably, in the coated metal salt solution of step (2), the concentration of the complexing agent is 0.1-10 g / L, for example, it can be 0.1 g / L, 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the coating metal source solution in step (2) also includes a metal fluoride salt.

[0029] Preferably, the metal fluoride salt comprises sodium fluoride.

[0030] The coating metal source solution of the present invention also includes a fluoride salt such as sodium fluoride, which can more stably complex metal ions and make the co-precipitation of the metal elements more uniform.

[0031] Preferably, the concentration of the metal fluoride salt in the coating metal source solution in step (2) is the same as the concentration of ammonia water.

[0032] Preferably, the coating metal source solution in step (2) includes copper ions and / or niobium ions.

[0033] Preferably, the pH value of the control system in step (2) is 8-9, for example, 8, 8.2, 8.4, 8.6, 8.8 or 9, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] In a second aspect, the present invention provides a coated quaternary sodium electrolyte precursor material, which is prepared by the preparation method described in the first aspect.

[0035] In a third aspect, the present invention provides a sodium battery positive electrode material, which is obtained by mixing and sintering a sodium source and the coated quaternary sodium battery precursor material as described in the second aspect.

[0036] Preferably, the sintering temperature is 400-1300°C, for example, it can be 400°C, 600°C, 800°C, 1000°C, 1200°C or 1300°C, and the time is 12-48h, for example, it can be 12h, 20h, 30h, 40h or 48h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the molar ratio of the sodium ions in the sodium source to the total metal ions in the coated quaternary sodium electric precursor material is (1-1.05):1, for example, it can be 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1 or 1.05:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] In a fourth aspect, the present invention provides a sodium ion battery, comprising the sodium cathode material as described in the third aspect.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention can achieve uniform distribution of multiple elements by controlling the composition of the aluminum source solution and the coating metal source solution during the coprecipitation reaction, while also forming a uniform and stable coating layer, thereby improving the stability and cycle performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a morphology diagram of the coated quaternary sodium electrode precursor material obtained in Example 1 of the present invention at a magnification of 3000 times. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0043] Example 1

[0044] This embodiment provides a method for preparing a coated quaternary sodium electrolyte precursor material, the preparation method comprising the following steps:

[0045] (1) preparing a nickel-iron-manganese mixed salt solution with a total metal concentration of 0.6 mol / L, wherein the molar ratio of nickel-iron-manganese is 60:20:20, and the metal salts used in the preparation are nickel sulfate, ferrous sulfate, and manganese sulfate in sequence;

[0046] An aluminum source solution was prepared by mixing aluminum sulfate and an excess sodium hydroxide solution to obtain a sodium metaaluminate solution with a molar concentration of 0.3 mol / L, and the sodium metaaluminate solution was mixed with 0.3 mol / L ammonia water to obtain an aluminum source solution. The pH of the aluminum source solution was 9.5, and the ammonia concentration was 3.5 g / L.

[0047] Mixing 0.3 mol / L copper sulfate solution with 0.6 mol / L ammonia water to obtain a copper source coating solution, wherein the ammonia concentration in the copper source coating solution is 3.5 g / L;

[0048] (2) Before the reaction, a base liquid is prepared in a reaction vessel by adding sodium hydroxide solution and ammonia water until the pH of the reaction base liquid reaches 9.5 and the ammonia concentration reaches 3 g / L. High-purity nitrogen gas with a purity of 99.999% is continuously introduced until the end of the reaction. According to the metal molar ratio Ni:Fe:Mn:Al=6:2:1:1, the nickel-iron-manganese mixed salt solution and the aluminum source solution are added to the base liquid at a certain rate to start the reaction. The pH value during the reaction is controlled within the range of 9.8 by using ammonia water and liquid caustic soda, and the ammonia concentration is 3-4 g / L. The temperature during the reaction is controlled at 45°C and the stirring speed is controlled at 400 rpm. After the reaction particle size D50 of the quaternary precursor reaches 10 μm, the feeding is stopped to obtain the matrix quaternary sodium precursor.

[0049] (3) The reaction speed was increased to 1000 rpm, the pH of the system in the reactor was maintained in the range of 8-9, the copper source coating solution was added to the reactor according to the set coating amount of 1000 ppm, and the reaction was terminated after the copper source coating solution was added. The obtained compound was washed, centrifuged and dried, and then dried in a vacuum freeze dryer for 12 hours to obtain the coated quaternary sodium electric precursor material. The morphology of the coated quaternary sodium electric precursor material is shown in FIG. Figure 1 shown.

[0050] Example 2

[0051] This embodiment provides a method for preparing a coated quaternary sodium electrolyte precursor material, the preparation method comprising the following steps:

[0052] (1) preparing a nickel-iron-manganese mixed salt solution with a total metal concentration of 2 mol / L, wherein the molar ratio of nickel-iron-manganese is 60:20:20, and the metal salts used in the preparation are nickel sulfate, ferrous sulfate, and manganese sulfate in sequence;

[0053] An aluminum source solution was prepared by mixing aluminum sulfate and an excess of sodium hydroxide solution to obtain a sodium metaaluminate solution with a molar concentration of 0.3 mol / L. The sodium metaaluminate solution was mixed with aqueous ammonia to obtain an aluminum source solution. The pH of the aluminum source solution was 9 and the ammonia concentration was 5 g / L.

[0054] Mixing 0.3 mol / L copper sulfate solution with aqueous ammonia to obtain a copper source coating solution, wherein the ammonia concentration in the copper source coating solution is 5 g / L;

[0055] (2) Before the reaction, a base liquid is prepared in a reaction vessel by adding sodium hydroxide solution and ammonia water until the pH of the reaction base liquid reaches 8 and the ammonia concentration reaches 10 g / L. High-purity nitrogen gas with a purity of 99.999% is continuously introduced until the end of the reaction. According to the metal molar ratio of Ni:Fe:Mn:Al=6:2:1:1, the nickel-iron-manganese mixed salt solution and the aluminum source solution are added to the base liquid at a certain rate to start the reaction. The pH value of the reaction process is controlled to 9 by ammonia water and liquid caustic soda, and the ammonia concentration is 4-5 g / L. The temperature during the reaction process is controlled at 65°C and the stirring speed is controlled at 800 rpm. After the reaction particle size D50 of the quaternary precursor reaches 10 μm, the feeding is stopped to obtain the matrix quaternary sodium precursor.

[0056] (3) increasing the reaction speed to 1000 rpm, maintaining the pH of the system in the reactor within the range of 8-9, adding the copper source coating solution to the reactor at a set coating amount of 1000 ppm, terminating the reaction after the copper source coating solution is added, and subjecting the obtained compound to washing, centrifugation, and drying, and then drying it in a vacuum freeze dryer for 12 hours to obtain the coated quaternary sodium electrode precursor material.

[0057] Example 3

[0058] This embodiment provides a method for preparing a coated quaternary sodium electrolyte precursor material, the preparation method comprising the following steps:

[0059] (1) preparing a nickel-iron-manganese mixed salt solution with a total metal concentration of 5 mol / L, wherein the molar ratio of nickel-iron-manganese is 60:20:20, and the metal salts used in the preparation are nickel sulfate, ferrous sulfate, and manganese sulfate in sequence;

[0060] An aluminum source solution was prepared by mixing aluminum sulfate and an excess of sodium hydroxide solution to obtain a sodium metaaluminate solution with a molar concentration of 0.3 mol / L. The sodium metaaluminate solution was mixed with aqueous ammonia to obtain an aluminum source solution. The pH of the aluminum source solution was 11.5, and the concentration of aqueous ammonia was 3 g / L.

[0061] Mixing 0.3 mol / L copper sulfate solution with aqueous ammonia to obtain a copper source coating solution, wherein the aqueous ammonia concentration in the copper source coating solution is 3 g / L;

[0062] (2) Before the reaction, a base liquid is prepared in a reaction vessel by adding sodium hydroxide solution and ammonia water until the pH of the reaction base liquid reaches 11 and the ammonia concentration reaches 2 g / L. High-purity nitrogen gas with a purity of 99.999% is continuously introduced until the end of the reaction. According to the metal molar ratio of Ni:Fe:Mn:Al=6:2:1:1, the nickel-iron-manganese mixed salt solution and the aluminum source solution are added to the base liquid at a certain rate to start the reaction. The pH value of the reaction process is controlled to 12 and the ammonia concentration is 3-4 g / L using ammonia water and liquid caustic soda. The temperature during the reaction process is controlled at 45°C and the stirring speed is controlled at 1000 rpm. After the reaction particle size D50 of the quaternary precursor reaches 10 μm, the feeding is stopped to obtain the matrix quaternary sodium precursor.

[0063] (3) The reaction speed is increased to 1200 rpm, the pH of the system in the reactor is maintained in the range of 8-9, the copper source coating solution is added to the reactor according to the set coating amount of 2000 ppm, and the reaction is terminated after the copper source coating solution is added. The obtained compound is washed, centrifuged and dried, and then dried in a vacuum freeze dryer for 12 hours to obtain the coated quaternary sodium electrode precursor material.

[0064] Example 4

[0065] This embodiment provides a method for preparing a coated quaternary sodium electrode precursor material. The preparation method is the same as that of Example 1 except that sodium fluoride is added to the copper source coating solution in step (1), and the concentration of sodium fluoride is the same as that of ammonia water.

[0066] Example 5

[0067] This embodiment provides a method for preparing a coated quaternary sodium electrolyte precursor material. The preparation method is the same as that of Example 1, except that the concentration of ammonia water in the aluminum source solution in step (1) is 0.5 g / L.

[0068] Example 6

[0069] This embodiment provides a method for preparing a coated quaternary sodium electrolyte precursor material. The preparation method is the same as that of Example 1, except that the concentration of ammonia water in the aluminum source solution in step (1) is 12.5 g / L.

[0070] Example 7

[0071] This embodiment provides a method for preparing a coated quaternary sodium electrode precursor material. The preparation method is the same as that of Example 1, except that the ammonia concentration in the copper source coating solution in step (1) is 0.1 g / L.

[0072] Example 8

[0073] This embodiment provides a method for preparing a coated quaternary sodium electrode precursor material. The preparation method is the same as that of Example 1, except that the ammonia concentration in the copper source coating solution in step (1) is 12.5 g / L.

[0074] Comparative Example 1

[0075] This comparative example provides a method for preparing a coated quaternary sodium electrolyte precursor material. The preparation method is the same as Example 1 except that no ammonia water is added to the aluminum source solution in step (1).

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing a coated quaternary sodium electrolyte precursor material. The preparation method is the same as Example 1 except that the aluminum source solution in step (1) is a 0.3 mol / L aluminum sulfate solution.

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing a coated quaternary sodium electrode precursor material. The preparation method is the same as that of Example 1, except that the copper source coating solution in step (1) does not contain ammonia water.

[0080] The coated quaternary sodium precursor material obtained in the above embodiments and comparative examples was mixed with sodium hydroxide in a molar ratio of 1:1, and then calcined at 800°C for 24h to obtain a positive electrode material; the positive electrode material was mixed with SP (carbon black conductive agent), CNT (carbon nanotube) and PVDF (polyvinylidene fluoride), wherein the mass ratio of the positive electrode material, SP+CNT and PVDF was controlled to be 90:5:5, and NMP (N-methylpyrrolidone) was used as a solvent. After slurrying and stirring for several hours, a positive electrode slurry was obtained, and then the positive electrode slurry was prepared into a positive electrode sheet. The positive electrode sheet was used with a sodium sheet, a polypropylene separator and a sodium hexafluorophosphate electrolyte to prepare a sodium ion battery. A constant current charge and discharge test was carried out in the voltage range of 2.0-4.0V, with a rate of 0.1C for the first 3 cycles and a rate of 1C thereafter. The test was carried out for a total of 200 cycles to test the initial discharge capacity and capacity retention rate of the prepared sodium ion battery. The test results are shown in Table 1:

[0081] Table 1

[0082]

[0083]

[0084] From Table 1 we can see that:

[0085] It can be seen from Example 1 and Comparative Examples 1-2 that the aluminum source solution of the present invention is preferably an aluminum aluminate solution, and preferably contains ammonia water, which can promote uniform precipitation between elements and improve the performance of the precursor material; it can be seen from Example 1 and Comparative Example 3 that the present invention preferably contains ammonia water in the copper source coating solution, which can promote the precipitation and uniform coating of copper ions, thereby improving battery performance; it can be seen from Example 1 and Example 4 that the present invention preferably contains fluoride salt in the copper source coating solution; it can be seen from Example 1 and Examples 5-6 that the concentration of the complexing agent in the aluminum source solution of the present invention will affect the uniform precipitation between the elements, thereby affecting the performance of the battery; it can be seen from Example 1 and Examples 7-8 that the concentration of the complexing agent in the copper source coating solution of the present invention is preferably within a specific range, which is beneficial to improving the performance of the battery.

[0086] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a coated quaternary sodium electrode precursor material, characterized in that: The preparation method comprises the following steps: (1) introducing a nickel-iron-manganese mixed salt solution, an aluminum source solution, a precipitant solution, and a complexing agent solution into a bottom liquid to perform a coprecipitation reaction to obtain a core precursor material; The aluminum source solution includes metaaluminate, a precipitant and a complexing agent; (2) after stopping the feeding and adjusting the pH value of the system, introducing the coating metal source solution to carry out the coating reaction to obtain the coated quaternary sodium electrode precursor material; The coating metal source solution includes a complexing agent.

2. The preparation method according to claim 1, characterized in that The pH of the aluminum source solution in step (1) is 9-12, and the concentration of the complexing agent is 1-10 g / L; Preferably, the method for preparing the aluminum source solution in step (1) comprises: mixing an aluminum salt and an excess precipitant solution to obtain a metaaluminate solution, and then adding a complexing agent solution to obtain the aluminum source solution.

3. The preparation method according to claim 1 or 2, characterized in that The pH of the coprecipitation reaction in step (1) is 7.5-12; Preferably, the temperature of the coprecipitation reaction in step (1) is 20-65° C., and the stirring speed is 100-1500 rpm; Preferably, the coprecipitation reaction in step (1) is carried out under a protective atmosphere.

4. The preparation method according to any one of claims 1 to 3, characterized in that The total metal ion concentration of the nickel-iron-manganese mixed salt solution in step (1) is 0.1-5 mol / L; Preferably, the pH of the base solution in step (1) is 7.5-11, and the concentration of the complexing agent is 0.1-10 g / L; Preferably, oxygen is first removed from the base liquid in step (1) before the nickel-iron-manganese mixed salt solution, aluminum source solution, precipitant solution and complexing agent solution are introduced.

5. The preparation method according to any one of claims 1 to 4, characterized in that In the coating metal salt solution of step (2), the concentration of the complexing agent is 0.1-10 g / L; Preferably, the coating metal source solution in step (2) further comprises a metal fluoride salt; Preferably, the metal fluoride salt comprises sodium fluoride.

6. The preparation method according to any one of claims 1 to 5, characterized in that The coating metal source solution in step (2) includes copper ions and / or niobium ions; Preferably, the pH value of the control system in step (2) is 8-9.

7. A coated quaternary sodium electrode precursor material, characterized in that: The coated quaternary sodium electrode precursor material is prepared by the preparation method according to any one of claims 1 to 6.

8. A sodium cathode material, characterized in that The sodium battery positive electrode material is obtained by mixing and sintering a sodium source and the coated quaternary sodium battery precursor material as claimed in claim 7.

9. The sodium cathode material according to claim 8, characterized in that The sintering temperature is 400-1300°C and the sintering time is 12-48h; Preferably, the molar ratio of sodium ions in the sodium source to total metal ions in the coated quaternary sodium electric precursor material is (1-1.05):

1.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the sodium cathode material according to claim 8 or 9.

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