Sodium ion positive electrode precursor material, and preparation method therefor and use thereof

Abstract

A sodium ion positive electrode precursor material, and a preparation method therefor and a use thereof. The preparation method comprises the following steps: concurrently adding a nickel-copper-manganese mixed salt solution, a precipitant solution and a complexing agent solution, and carrying out a co-precipitation reaction under a protective atmosphere to obtain the nickel-copper-manganese mixed salt solution, wherein the precipitant solution comprises a carbonate system solution, and the complexing agent solution comprises a sodium citrate solution. A carbonate system is used to carry out the co-precipitation reaction, and a special sodium citrate complexing agent is used in combination, solving the problem of copper phase separation in the co-precipitation reaction process under a nickel-copper-manganese system, improving the sphericity and uniformity of a precursor material, and improving the specific capacity and cycling stability of a positive electrode material.

Description

A sodium ion positive electrode precursor material and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of sodium ion batteries and relates to a sodium ion positive electrode precursor material and a preparation method and application thereof. Background Art

[0002] Layered transition metal oxides (NaTMO2) have attracted significant interest as cathode materials for sodium-ion batteries (SIBs) due to their high specific capacity, compatibility with lithium-ion equipment, mature production processes, and excellent overall performance. TMs are redox-capable transition metals from the third period (Ti, V, Cr, Mn, Fe, Co, Ni, and Cu). By adjusting the composition and ratio of these elements, they exhibit tunable electrochemical activity, enabling the flexible design of new electrode compounds with improved electrochemical performance to meet the specific needs of downstream applications.

[0003] For example, CN107706375A discloses a method for preparing a manganese-based sodium ion composite oxide positive electrode material. The general formula of the positive electrode material is Na 1‐x Q x Mn 1‐y M y O2, wherein 0≤x≤0.4, 0≤y<0.4, Q and M are both modifying elements. The specific method is as follows: a sodium source, a manganese source, a compound of modifying elements Q and M are weighed according to a Na:Q:Mn:M molar ratio of 0.1-1.0:0-0.9:0.5-1.0:0-0.5, and then placed in a device with a crushing medium and a dispersant for crushing and uniform mixing, and then crystallized and synthesized at a temperature range of 500-900°C for 3-30 hours, then cooled to a range of 200-500°C and quenched at a constant temperature for 1-5 hours, then naturally cooled to room temperature, and finally mixed and crushed in a mixing and grinding device to obtain a manganese-based sodium ion composite oxide positive electrode material.

[0004] Mn 3+ The Jahn-Teller distortion is considered to be one of the most important factors in the structural evolution of O3-NaMnO2, which produces a strong Na-ordered phase and creates a unique high-capacity new high-pressure phase. When Mn is mixed with other transition metal elements in layered oxides with a composition of more than 50%, it can act as a promoter and stabilizer of the P2 phase. Compared with NaMnO2, this P2 phase generally has better cyclability and a smoother voltage distribution. For some Ni-containing NaTMO2 positive electrodes, under a certain high-voltage cutoff, the redox process is more reversible and stable than that of lithium-containing positive electrodes. It is particularly noteworthy that in recent years, the environmentally friendly and cost-effective Cu element has been introduced into the layered sodium-ion battery positive electrode material, which exhibits reversible Cu 2+ / 3+Redox and capacity, rate performance and cycle stability are enhanced.

[0005] After adding copper, it is easy to separate from the nickel and manganese elements, resulting in poor sphericity and consistency of the product structure, and poor capacity and cycle performance. For example, CN114956211A relates to a manganese-nickel-copper precursor with different morphologies. According to the selected chemical composition, a soluble manganese source material, a nickel source material and a copper source material are taken as raw materials. In the presence of a reducing agent and a complexing agent, a precipitant is added to react. The reducing agent includes at least one of acetaldehyde, phenol or hydrazine hydrate, the complexing agent includes at least one of ammonia water, sodium fluoride or hydroxyethylethylenediaminetriacetic acid, and the precipitant includes an alkaline solution (sodium hydroxide and potassium hydroxide). Copper in this reaction system is very easy to separate, resulting in uneven element distribution.

[0006] Therefore, how to solve the phase separation problem of copper in the precursor of sodium ion positive electrode materials under the nickel-copper-manganese system is a key issue that needs to be solved urgently.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of this application is to provide a sodium ion cathode precursor material, its preparation method, and its application. This application utilizes a carbonate system for coprecipitation, combined with a special sodium citrate complexing agent, to address the copper phase separation issue during the coprecipitation reaction in a nickel-copper-manganese system. This also improves the sphericity and consistency of the precursor material, thereby enhancing the specific capacity and cycle stability of the cathode material.

[0010] To achieve this goal, this application adopts the following technical solutions:

[0011] In a first aspect, the present application provides a method for preparing a sodium ion positive electrode precursor material, the preparation method comprising the following steps:

[0012] Adding a nickel-copper-manganese mixed salt solution, a precipitant solution, and a complexing agent solution in parallel, and performing a coprecipitation reaction under a protective atmosphere to obtain the nickel-copper-manganese mixed salt solution;

[0013] Wherein, the precipitant solution includes a carbonate system solution, and the complexing agent solution includes a sodium citrate solution.

[0014] The coprecipitation reaction provided in the present application is carried out under a protective atmosphere (such as a nitrogen atmosphere); in the present application, the salt in the mixed salt solution includes but is not limited to sulfate, nitrate or chloride, etc.

[0015] This application adopts a carbonate system for co-precipitation reaction, combined with a special sodium citrate complexing agent, the synergistic effect of the precipitant and the complexing agent, solves the problem of copper phase separation during the co-precipitation reaction in the nickel-copper-manganese system, and at the same time improves the sphericity and consistency of the precursor material, and improves the specific capacity and cycle stability of the positive electrode material.

[0016] In this application, if the precipitant is complexed with the sodium citrate complexing agent in a non-carbonate system, uniform precipitation of Ni, Cu and Mn metal elements cannot be achieved; and if other precipitation systems are used, such as a system of ammonia water and liquid alkali, the Cu phase separation problem cannot be solved;

[0017] In one embodiment, the total molar concentration of metal ions in the nickel-copper-manganese mixed salt solution is 0.5-2 mol / L, for example, 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, 1.5 mol / L, 1.75 mol / L or 2 mol / L.

[0018] In one embodiment, the molar concentration of the precipitant solution is 0.5 to 2 mol / L, for example, 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, 1.5 mol / L, 1.75 mol / L or 2 mol / L.

[0019] In one embodiment, the molar concentration of the complexing agent solution is 0.25 to 1.5 mol / L, such as 0.25 mol / L, 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L or 1.5 mol / L.

[0020] In one embodiment, the carbonate system solution includes sodium carbonate solution and / or sodium bicarbonate solution.

[0021] In one embodiment, the flow rate of the nickel-copper-manganese mixed salt solution is 2 to 10 L / h, for example, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h or 10 L / h.

[0022] In one embodiment, the flow rate of the precipitant solution is 2 to 8 L / h, for example, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h or 8 L / h.

[0023] In one embodiment, the flow rate of the complexing agent solution is 1 to 3 L / h, for example, 1 L / h, 1.25 L / h, 1.5 L / h, 1.75 L / h, 2 L / h, 2.25 L / h, 2.5 L / h, 2.75 L / h or 3 L / h.

[0024] In the present application, the flow rate of the nickel-copper-manganese mixed salt solution, the flow rate of the precipitant solution and the flow rate of the complexing agent solution work synergistically to regulate the ion concentration of the system and inhibit the occurrence of side reactions in the system. If the flow rate of any one party is not within the above range, it will lead to the appearance of impurities.

[0025] In one embodiment, the pH value during the coprecipitation reaction is 7.5 to 9.5, such as 7, 7.5, 8, 8.5, 9 or 9.5.

[0026] In one embodiment, the stirring speed of the coprecipitation reaction is 230-420 rpm, for example, 230 rpm, 250 rpm, 280 rpm, 300 rpm, 330 rpm, 350 rpm, 380 rpm, 400 rpm or 420 rpm.

[0027] In one embodiment, the coprecipitation reaction temperature is 30-70°C, such as 30°C, 40°C, 50°C, 60°C or 70°C.

[0028] In one embodiment, the coprecipitation reaction time is 40 to 120 hours, for example, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, 110 hours or 120 hours.

[0029] As an optional technical solution, the preparation method includes the following steps:

[0030] A nickel-copper-manganese mixed salt solution with a total molar concentration of metal ions of 0.5-2 mol / L, a precipitant solution with a molar concentration of 0.5-2 mol / L, and a complexing agent solution with a molar concentration of 0.25-1.5 mol / L are added in parallel, wherein the flow rate of the nickel-copper-manganese mixed salt solution is 2-10 L / h; the flow rate of the precipitant solution is 2-8 L / h; and the flow rate of the complexing agent solution is 1-3 L / h. A coprecipitation reaction is carried out for 40-120 hours at a stirring speed of 230-420 rpm and a reaction temperature of 30-70° C. in an environment with a pH value of 7.5-9.5, to obtain the nickel-copper-manganese mixed salt solution;

[0031] Wherein, the precipitant solution includes sodium carbonate solution and / or sodium bicarbonate solution, and the complexing agent solution includes sodium citrate solution.

[0032] In the second aspect, the present application provides a sodium ion positive electrode precursor material, which is prepared by the preparation method as described in the first aspect, and the chemical formula of the sodium ion positive electrode precursor material is Mn 1-x-y Ni x Cu yCO3; 0.1≤x≤0.4, 0<y≤0.2, for example, the x may be 0.1, 0.2, 0.3 or 0.4, etc., and the y may be 0.01, 0.05, 0.1, 0.15 or 0.2, etc.

[0033] In a third aspect, the present application provides a sodium ion positive electrode material, which is obtained by mixing and sintering the sodium ion positive electrode precursor material as described in the second aspect with a sodium source.

[0034] In a fourth aspect, the present application also provides a sodium ion battery, which includes the sodium ion positive electrode material as described in the third aspect.

[0035] Compared with the prior art, this application has the following beneficial effects:

[0036] This application adopts a carbonate system for co-precipitation reaction, combined with a special sodium citrate complexing agent, the synergistic effect of the precipitant and the complexing agent, solves the problem of copper phase separation during the co-precipitation reaction in the nickel-copper-manganese system, and at the same time improves the sphericity and consistency of the precursor material, and improves the specific capacity and cycle stability of the positive electrode material.

[0037] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0039] FIG1 is a SEM image of the sodium ion positive electrode precursor material provided in Example 1.

[0040] FIG2 is an SEM image of the sodium ion positive electrode precursor material provided in Comparative Example 2. DETAILED DESCRIPTION

[0041] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0042] Example 1

[0043] This embodiment provides a homogeneously precipitated sodium ion positive electrode precursor material, the chemical formula of which is Mn 0.7 Ni 0.2 Cu 0.1 CO3.

[0044] The preparation method of the precursor material is as follows:

[0045] Step 1, dissolving manganese sulfate, nickel sulfate, and copper sulfate crystals in pure water to prepare a solution A with a total metal molar concentration of 1 mol / L according to a molar ratio of Mn:Ni:Cu=0.7:0.2:0.1, dissolving sodium carbonate in pure water to prepare a sodium carbonate solution with a molar concentration of 1 mol / L, and dissolving sodium citrate in pure water to prepare a 0.7 mol / L sodium citrate solution;

[0046] Step 2: Solution A, sodium carbonate solution, and sodium citrate solution were simultaneously added to the reactor through metering pumps, and nitrogen with a purity of 99.9% was introduced into the reactor. The materials in the reactor were stirred by a stirring paddle. The stirring speed was 350 rpm, the flow rate of solution A was 6 L / h, the flow rate of sodium carbonate solution was 5 L / h, the pH of the reaction system was controlled to be 8.5, the flow rate of sodium citrate solution was 2 L / h, the reaction temperature was 50°C, and the reaction was carried out for 80 hours.

[0047] Step 3: After filtering, heat and dry at 100°C for 12 hours to obtain the product with the chemical formula of Mn 0.7 Ni 0.2 Cu 0.1 CO3 manganese nickel copper sodium ion battery cathode material precursor.

[0048] Example 2

[0049] This embodiment provides a homogeneously precipitated sodium ion positive electrode precursor material, the chemical formula of which is Mn 0.7 Ni 0.2 Cu 0.1 CO3.

[0050] The preparation method of the precursor material is as follows:

[0051] Step 1, dissolving manganese sulfate, nickel sulfate, and copper sulfate crystals in pure water to prepare a solution A with a total metal molar concentration of 2 mol / L according to a molar ratio of Mn:Ni:Cu=0.7:0.2:0.1, dissolving sodium carbonate in pure water to prepare a sodium carbonate solution with a molar concentration of 2 mol / L, and dissolving sodium citrate in pure water to prepare a 1.5 mol / L sodium citrate solution;

[0052] Step 2: Solution A, sodium carbonate solution, and sodium citrate solution were simultaneously added to the reactor through metering pumps, and nitrogen with a purity of 99.9% was introduced into the reactor. The materials in the reactor were stirred by a stirring paddle. The stirring speed was 420 rpm, the flow rate of solution A was 2 L / h, the flow rate of sodium carbonate solution was 2 L / h, the pH of the reaction system was controlled to be 9.5, the flow rate of sodium citrate solution was 1 L / h, the reaction temperature was 70°C, and the reaction was carried out for 120 h.

[0053] Step 3: After filtering, heat and dry at 100°C for 12 hours to obtain the product with the chemical formula of Mn 0.7 Ni 0.2 Cu 0.1 CO3 manganese nickel copper sodium ion battery cathode material precursor.

[0054] Example 3

[0055] This embodiment provides a homogeneously precipitated sodium ion positive electrode precursor material, the chemical formula of which is Mn 0.7 Ni 0.2 Cu 0.1 CO3.

[0056] The preparation method of the precursor material is as follows:

[0057] Step 1, dissolving manganese sulfate, nickel sulfate, and copper sulfate crystals in pure water to prepare a solution A with a total metal molar concentration of 0.5 mol / L according to a molar ratio of Mn:Ni:Cu=0.7:0.2:0.1, dissolving sodium carbonate in pure water to prepare a sodium carbonate solution with a molar concentration of 0.5 mol / L, and dissolving sodium citrate in pure water to prepare a 0.25 mol / L sodium citrate solution;

[0058] Step 2: Solution A, sodium carbonate solution, and sodium citrate solution were simultaneously added to the reactor through metering pumps, and nitrogen with a purity of 99.9% was introduced into the reactor. The materials in the reactor were stirred by a stirring paddle. The stirring speed was 250 rpm, the flow rate of solution A was 10 L / h, the flow rate of sodium carbonate solution was 8 L / h, the pH of the reaction system was controlled to be 7.5, the flow rate of sodium citrate solution was 3 L / h, the reaction temperature was 30°C, and the reaction was carried out for 40 hours.

[0059] Step 3: After filtering, heat and dry at 100°C for 12 hours to obtain the product with the chemical formula of Mn 0.7 Ni 0.2 Cu 0.1 CO3 manganese nickel copper sodium ion battery cathode material precursor.

[0060] Example 4

[0061] The difference between this embodiment and embodiment 1 is that the precipitant in this embodiment is sodium bicarbonate, and the chemical formula of the precursor material is Mn 0.65 Ni 0.15 Cu 0.2 CO3.

[0062] In the preparation method, the molar ratio of the transition metal is adaptively adjusted.

[0063] The rest of the preparation methods and parameters were the same as those in Example 1.

[0064] Example 5

[0065] The difference between this embodiment and embodiment 1 is that the molar concentration of the sodium carbonate solution in step 1 of this embodiment is 2.5 mol / L.

[0066] The rest of the preparation methods and parameters were the same as those in Example 1.

[0067] Example 6

[0068] The difference between this embodiment and embodiment 1 is that the total molar concentration of metals in solution A in step 1 of this embodiment is 0.3 mol / L.

[0069] The remaining preparation methods and parameters are the same as those in Example 1. Example 7

[0070] The difference between this embodiment and embodiment 1 is that the flow rate of the sodium citrate solution in step 2 of this embodiment is 4 L / h.

[0071] The rest of the preparation methods and parameters were the same as those in Example 1.

[0072] Example 8

[0073] The difference between this embodiment and embodiment 1 is that the flow rate of the sodium carbonate solution in step 2 of this embodiment is 1.0 L / h.

[0074] The rest of the preparation methods and parameters were the same as those in Example 1.

[0075] Comparative Example 1

[0076] This comparative example provides a sodium ion precursor positive electrode material in a hydroxide system, and the preparation method is as follows:

[0077] Step 1: dissolving manganese sulfate, nickel sulfate, and copper sulfate crystals in pure water to prepare a solution A with a total metal molar concentration of 1 mol / L according to a molar ratio of Mn:Ni:Cu=0.7:0.2:0.1; dissolving sodium hydroxide in pure water to prepare a sodium hydroxide solution with a molar concentration of 1 mol / L; and preparing a 0.7 mol / L ammonia solution;

[0078] Step 2: Solution A, sodium hydroxide solution, and ammonia solution were simultaneously added to the reactor through a metering pump, and nitrogen with a purity of 99.9% was introduced into the reactor. The materials in the reactor were stirred by a stirring paddle. The stirring speed was 350 rpm, the flow rate of solution A was 6 L / h, the flow rate of sodium hydroxide solution was 5 L / h, the pH of the reaction system was controlled to be 10, the flow rate of ammonia solution was 1 L / h, the reaction temperature was 50°C, and the reaction was carried out for 80 hours.

[0079] Step 3: After filtering, heat and dry at 100°C for 12 hours to obtain the product with the chemical formula of Mn 0.7 Ni 0.2 Cu 0.1 (OH)2 manganese nickel copper sodium ion battery cathode material precursor.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that the complexing agent solution in this comparative example is an ammonia solution.

[0082] The rest of the preparation methods and parameters were the same as those in Example 1.

[0083] The sodium ion precursor materials provided in Example 1-8 and Comparative Example 1-2 were mixed with sodium carbonate, sintered at 1000° C. for 12 h, and the obtained materials were pulverized to obtain sodium ion oxide positive electrode materials.

[0084] Figure 1 shows an SEM image of the sodium ion positive electrode precursor material provided in Example 1, and Figure 2 shows an SEM image of the sodium ion positive electrode precursor material provided in Comparative Example 2. From the comparison of Figures 1 and 2, it can be seen that the sodium ion precursor material obtained by the preparation method provided in the present application has a denser structure and a higher tap density, which indicates that the problems caused by copper phase separation have been overcome. The product structure in Comparative Example 2 has loose particles and uneven morphology, indicating that it has a serious copper phase separation problem.

[0085] The provided sodium ion positive electrode material is used as the main material and is homogenized in a ratio of 95 (main material): 2.5 (PVDF): 2.5 (SP). The aluminum foil is then spread flat on a coater for coating and placed in a 120°C forced air drying oven for drying for 3 hours. The battery is then punched, weighed, and the electrode is baked to form a CR2032 button battery. Finally, the battery is placed in a blue electric test system for electrical performance testing.

[0086] The batteries provided in Examples 1-8 and Comparative Examples 1-2 were subjected to electrochemical performance testing under charge and discharge voltage conditions of 2.0-4.0 V. The batteries were charged and discharged at a rate of 0.1C / 0.1C for the first cycle, followed by 50 cycles at a rate of 0.5C / 1C. Cycling stability was measured as the percentage of the discharge capacity at the 50th cycle divided by the discharge capacity at the first cycle. The test results are shown in Table 1.

[0087] Table 1

[0088] From the data results of Example 1 and Examples 5-8, it can be seen that in the present application, the molar concentrations and flow rates of the metal ions, precipitant solution and complexing agent solution in the nickel-copper-manganese mixed sulfate solution are coordinated to achieve uniform precipitation of Ni, Cu and Mn elements. If any one of them is too large or too small, side reactions will occur and inactive by-products will be generated.

[0089] From the data results of Example 1 and Comparative Examples 1-2, it can be seen that in the present application, the precipitant and the complexing agent are coordinated and neither of them can be missing to achieve homogeneous precipitation of copper in the nickel-copper-manganese system and avoid Cu phase separation. The coordination of other systems cannot obtain a precursor product with uniform precipitation and no phase separation.

[0090] In summary, the present application adopts a carbonate system for co-precipitation reaction, combined with a special sodium citrate complexing agent, the synergistic effect of the precipitant and the complexing agent, solves the problem of copper phase separation during the co-precipitation reaction under the nickel-copper-manganese system, and at the same time improves the sphericity and consistency of the precursor material, and improves the specific capacity and cycle stability of the positive electrode material.

[0091] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A method for preparing a sodium ion positive electrode precursor material, the preparation method comprising the following steps: Adding a nickel-copper-manganese mixed salt solution, a precipitant solution and a complexing agent solution in parallel, and performing a coprecipitation reaction under a protective atmosphere to obtain the nickel-copper-manganese mixed salt solution; Wherein, the precipitant solution comprises a carbonate system solution, and the complexing agent solution comprises a sodium citrate solution.

2. The method for preparing the sodium ion positive electrode precursor material according to claim 1, wherein: The total molar concentration of metal ions in the nickel-copper-manganese mixed salt solution is 0.5 to 2 mol / L; Optionally, the molar concentration of the precipitant solution is 0.5 to 2 mol / L; Optionally, the molar concentration of the complexing agent solution is 0.25 to 1.5 mol / L; Optionally, the carbonate system solution includes sodium carbonate solution and / or sodium bicarbonate solution.

3. The method for preparing a sodium ion positive electrode precursor material according to claim 1 or 2, wherein: The flow rate of the nickel-copper-manganese mixed salt solution is 2 to 10 L / h.

4. The method for preparing a sodium ion positive electrode precursor material according to any one of claims 1 to 3, wherein: The flow rate of the precipitant solution is 2 to 8 L / h; Optionally, the flow rate of the complexing agent solution is 1 to 3 L / h.

5. The method for preparing the sodium ion positive electrode precursor material according to any one of claims 1 to 4, wherein: The pH value during the coprecipitation reaction is 7.5 to 9.5; Optionally, the stirring speed of the coprecipitation reaction is 230-420 rpm.

6. The method for preparing a sodium ion positive electrode precursor material according to any one of claims 1 to 5, wherein: The temperature of the coprecipitation reaction is 30 to 70° C. Optionally, the coprecipitation reaction time is 40 to 120 hours.

7. The method for preparing a sodium ion positive electrode precursor material according to any one of claims 1 to 6, wherein: The preparation method comprises the following steps: A nickel-copper-manganese mixed salt solution with a total molar concentration of metal ions of 0.5-2 mol / L, a precipitant solution with a molar concentration of 0.5-2 mol / L, and a complexing agent solution with a molar concentration of 0.25-1.5 mol / L are added in parallel, wherein the flow rate of the nickel-copper-manganese mixed salt solution is 2-10 L / h; the flow rate of the precipitant solution is 2-8 L / h; the flow rate of the complexing agent solution is 1-3 L / h, and a coprecipitation reaction is performed for 40-120 hours at a stirring speed of 230-420 rpm and a reaction temperature of 30-70° C. in an environment with a pH value of 7.5-9.5, to obtain the nickel-copper-manganese mixed salt solution; Wherein, the precipitant solution includes sodium carbonate solution and / or sodium bicarbonate solution, and the complexing agent solution includes sodium citrate solution.

8. A sodium ion positive electrode precursor material, wherein the sodium ion positive electrode precursor material is prepared by the preparation method according to any one of claims 1 to 7, and the chemical formula of the sodium ion positive electrode precursor material is Mn 1-x-y Ni x Cu y CO3; 0.1≤x≤0.4, 0<y≤0.

2.

9. A sodium ion positive electrode material, which is obtained by mixing and sintering the sodium ion positive electrode precursor material according to claim 8 and a sodium source.

10. A sodium ion battery, comprising the sodium ion positive electrode material according to claim 9.

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