Copper-based sodium positive electrode material, preparation method therefor, and use thereof

Abstract

A copper-based sodium positive electrode material, and a preparation method therefor and a use thereof. The chemical structural formula of the copper-based sodium positive electrode material is NaxMyCunO2, wherein M comprises at least three of Li, K, Al, Ti, Cr, Mn, Fe, Co, Ni, Zn, Mg, Sn, Zr, Mo, Nb, Y, W, In, and Ge, 0.5≤x≤1, 0≤y<1, and y+n=1.

Description

A copper-based sodium cathode material and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of sodium ion battery positive electrode materials, and in particular to a copper-based sodium positive electrode material and a preparation method and application thereof. Background Art

[0002] The rapid development of new energy technologies, particularly the booming lithium-ion battery industry, has led to rising prices for raw materials used in lithium-ion synthesis. Lithium resources, in particular, have seen their prices soar. Many new energy companies are vying for lithium, deploying and scrambling for resources around the world, leading to a rapid increase in the overall price of lithium batteries. Therefore, sodium-ion batteries have become the preferred alternative to lithium-ion batteries.

[0003] Common sodium-ion battery cathode materials include Prussian, polyanion, and layered oxides. Layered oxides, as sodium-ion battery cathode materials, have been extensively researched and developed due to their ideal specific capacity, ease of synthesis, and cycle stability. However, the most common method for synthesizing layered oxide sodium cathode materials is the precursor wet synthesis method.

[0004] Layered sodium oxide cathode materials are composed of many metal ions, which have good coordination and complementarity with each other. Some of the variable valence metal ions provide the main capacity and improve the air stability of the material; some inhibit the phase change that occurs during the charge and discharge process; and some act as a structural skeleton, improving the cyclic stability of the material, etc. However, for the presence of a large number of complex metal ions, the precipitation rate is inconsistent due to the different solubility products, making it difficult to co-precipitate. In particular, in the presence of copper, it is difficult to precipitate evenly when copper is co-precipitated with other metal ions, resulting in uneven element distribution, which seriously affects the electrical properties of the synthetic material. In response to the above problems, the present invention solves the problem that copper-based sodium cathode materials are difficult to precipitate.

[0005] Summary of the Invention

[0006] The present disclosure aims to address at least one of the technical problems existing in the related art. To this end, the present disclosure provides a copper-based sodium cathode material, a preparation method, and applications thereof. This preparation method addresses the difficulty in precipitation during the preparation of existing copper-based sodium cathode materials, resulting in a copper-based sodium cathode material with uniform element distribution and superior electrical performance.

[0007] The above technical objectives of the present disclosure are achieved through the following technical solutions:

[0008] A copper-based sodium cathode material, the chemical structure of the copper-based sodium cathode material is Na x M y Cu nO2, wherein M includes at least three of Li, K, Al, Ti, Cr, Mn, Fe, Co, Ni, Zn, Mg, Sn, Zr, Mo, Nb, Y, W, In, and Ge, 0.5≤x≤1, 0≤y<1, and y+n=1.

[0009] A method for preparing the copper-based sodium positive electrode material as described above comprises the following steps:

[0010] (1) Prepare a mixed solution containing M salt, add a complexing agent and alkali solution, and perform coprecipitation reaction to obtain M y (OH)2;

[0011] (2) M y (OH)2 is mixed with a sodium source and a copper source and calcined to obtain the copper-based sodium positive electrode material.

[0012] In one embodiment, in step (1), the M salt is at least one of an oxide, chloride, sulfate, nitrate, oxalate, citrate, carbonate and acetate of the M element.

[0013] In one embodiment, in step (1), the concentration of the mixed solution containing M salt is 1-2.5 mol / L.

[0014] In one embodiment, in step (1), the concentration of the mixed solution containing M salt is 1.7-2 mol / L.

[0015] In one embodiment, in step (1), the temperature of the coprecipitation reaction is 25-90°C.

[0016] In one embodiment, in step (1), the temperature of the coprecipitation reaction is 60-75°C.

[0017] In one embodiment, in step (1), the pH of the coprecipitation reaction is 8.5-12.5.

[0018] In one embodiment, in step (1), the pH of the coprecipitation reaction is 9-10.5.

[0019] In one embodiment, in step (1), the coprecipitation reaction is further accompanied by stirring, and the stirring frequency is 30-60 Hz.

[0020] In one embodiment, in step (1), the stirring frequency is 40-50 Hz.

[0021] In one embodiment, in step (1), the complexing agent is aqueous ammonia with a concentration of 1-6 g / L.

[0022] In one embodiment, in step (1), the alkali solution includes at least one of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the alkali solution is 2-10 mol / L.

[0023] In one embodiment, in step (1), the coprecipitation reaction is carried out in a reactor.

[0024] In one embodiment, in step (1), the M y The particle size of (OH)2 is 4-12 μm.

[0025] In one embodiment, in step (1), the M y The particle size of (OH)2 is 4-7 μm.

[0026] In one embodiment, in step (2), the sodium source includes at least one of sodium carbonate, sodium hydroxide and sodium bicarbonate.

[0027] In one embodiment, in step (2), the copper source includes at least one of copper oxide, copper chloride, copper sulfate, copper nitrate, copper oxalate, copper citrate, copper carbonate and copper acetate.

[0028] In one embodiment, in step (2), the calcination temperature is 500-1100° C., and the calcination time is 5-20 h.

[0029] In one embodiment, in step (2), the calcination temperature is 800-950° C., and the calcination time is 12-16 hours.

[0030] In one embodiment, in step (2), the mixing method is to mix by a mixer, the mixing speed is 800-1500 rpm, and the mixing time is 10-60 min.

[0031] A sodium ion battery comprises the copper-based sodium positive electrode material described above.

[0032] The beneficial effects of the present disclosure are:

[0033] (1) The copper-based sodium cathode material disclosed in the present invention has excellent electrochemical properties. After being prepared into a battery, the first efficiency of the battery at 0.1C reaches 76.08%, the first charge specific capacity can reach 142.12 mAh / g, the first discharge specific capacity can reach 110.23 mAh / g, and the discharge specific capacity at 0.33C can reach 108.86 mAh / g;

[0034] (2) The preparation method of the copper-based sodium cathode material disclosed in the present invention combines the precursor and solid phase methods in two steps, thereby solving the problems of uneven distribution of many metal elements, difficulty in mixing, and uneven mixing in the solid phase method. At the same time, it solves the problem of inconsistent precipitation rates and uneven precipitation of many metal ions due to different solubility products during the wet precipitation process.

[0035] (3) In the preparation method of the copper-based sodium positive electrode material disclosed in the present invention, the Cu-free M is synthesized from the precursor end. y (OH)2 precursor, adding Cu source through the sintering end, and finally synthesizing Cu-based sodium cathode material have the following advantages: M without Cu y During the wet synthesis of (OH)2 precursor, M y The physical and chemical data of (OH)2, such as morphology, particle size, primary particles, secondary particles, elemental composition, specific surface area, tapping, moisture, sphericity, compactness, etc., are used to obtain high-performance precursor materials;

[0036] (4) The high-performance precursor M in the preparation method of the copper-based sodium positive electrode material disclosed in the present invention y Sintering (OH)2 with a copper source produces copper-based materials with superior performance. From a kinetic and thermodynamic perspective, during high-temperature sintering, only copper ions diffuse, reducing competition from other ions and facilitating efficient and rapid copper ion entry into the bulk, resulting in a more uniform distribution.

[0037] (5) Compared with the sodium cathode material synthesized by the solid-phase sintering method, the preparation method of the copper-based sodium cathode material disclosed in the present invention combines the precursor and the solid-phase method in two steps, which reduces the sintering step and only requires one sintering, without the need for a second sintering, thereby reducing the sintering cost; and the prepared cathode material has uniform element distribution and excellent electrical properties;

[0038] (6) The preparation method of the copper-based sodium positive electrode material disclosed in the present invention solves the problem of low precipitation rate of Cu and loss of Cu ions during the co-precipitation process, so that the metal ion utilization rate reaches 100%, and solves related problems at the industrial end. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG1 is a process flow chart of Example 1 of the present disclosure;

[0040] FIG2 is a SEM image of the precursor of Example 1 of the present disclosure;

[0041] FIG3 is a SEM image of the precursor of Comparative Example 1 of the present disclosure;

[0042] FIG4 is a SEM image of the copper-based sodium cathode material prepared in Example 1 of the present disclosure;

[0043] FIG5 is a SEM image of the copper-based sodium positive electrode material prepared in Comparative Example 1 of the present disclosure. DETAILED DESCRIPTION

[0044] The present disclosure is further described below with reference to specific embodiments.

[0045] Example 1

[0046] A copper-based sodium cathode material NaNi 0.30 Mn 0.50 Fe 0.15 Cu 0.05 The preparation method of O2, as shown in Figure 1, specifically includes the following steps:

[0047] (1) According to the molar ratio of Ni:Mn:Fe of 0.3:0.50:0.15, the corresponding nickel sulfate, manganese sulfate and ferrous sulfate raw materials were weighed to prepare a mixed solution with a concentration of 1.5 mol / L. The mixed solution, ammonia water and sodium hydroxide solution were introduced into a reactor for reaction. The concentration of ammonia water was 4 g / L and the concentration of sodium hydroxide solution was 10 mol / L. The reaction temperature was 70 ° C, the stirring frequency was 60 Hz, and the pH value was 9.0. Ni was co-precipitated to form 0.3 Mn 0.5 Fe 0.15 (OH) 1.9 The precursor has a particle size of 6 μm. The SEM image of the precursor is shown in FIG2 . As shown in FIG2 , the precursor has a good morphology and good sphericity. The secondary particles are composed of flaky primary particles, and the particle size consistency is relatively uniform. The tap compaction ratio is high, reaching about 1.8.

[0048] (2) The generated Ni 0.3 Mn 0.5 Fe 0.15 (OH) 1.9 The precursor is mixed with a certain amount of Na2CO3 and CuO. The mixing method is to mix the materials by a high-speed machine at a mixing speed of 1000 rpm and a mixing time of 30 minutes. The mixture is sintered at a high temperature of 980 ° C for 20 hours to generate NaNi 0.3 Mn 0.5 Fe 0.15 Cu 0.05 O2 copper-based sodium positive electrode material, the SEM image of the copper-based sodium positive electrode material is shown in Figure 4, as shown in Figure 4, using Ni 0.3 Mn 0.5 Fe 0.15 (OH) 1.9 The copper-based sodium positive electrode material obtained by adding CuO to the precursor has a relatively simple morphology, all of which are single crystal structures, with consistent particle size, relatively round particles and a relatively smooth surface.

[0049] Comparative Example 1

[0050] A copper-based sodium cathode material NaNi 0.30 Mn 0.50 Fe 0.15 Cu 0.05 The preparation method of O2 is different from that of Example 1 in that a copper source is directly added to the precursor by co-precipitation. Specifically, the following steps are included:

[0051] (1) According to the molar ratio of Ni:Mn:Fe:Cu of 0.3:0.50:0.15:0.05, the corresponding nickel sulfate, manganese sulfate, copper sulfate and ferrous sulfate were weighed to prepare a mixed solution with a concentration of 1.5 mol / L. The mixed solution, ammonia water and sodium hydroxide solution were introduced into a reactor for reaction. The concentration of ammonia water was 4 g / L and the concentration of sodium hydroxide solution was 10 mol / L. The reaction temperature was 70 ° C, the stirring frequency was 60 Hz, and the pH value was 9.0. Ni was co-precipitated to form 0.30 Mn 0.50 Fe 0.15 Cu 0.05 (OH)2 precursor, the particle size of the precursor is 3μm, and the SEM image of the precursor is shown in Figure 3. As shown in Figure 3, when a copper source is added to the precursor end to synthesize a copper-based material, the morphology is relatively poor, the material becomes amorphous, the particle size is relatively small, and it is difficult to grow; the primary particles, morphology, sphericity, and particle size are difficult to control;

[0052] (2) The generated Ni 0.30 Mn 0.50 Fe 0.15 Cu 0.05 The (OH)2 precursor is mixed with a certain amount of sodium carbonate. The mixing method is to mix the materials by a high-speed machine at a mixing speed of 1000 rpm and a mixing time of 30 minutes. The mixture is sintered at a high temperature of 980 ° C for 20 hours to generate NaNi 0.3 Mn 0.5 Fe 0.15 Cu 0.05 O2 copper-based sodium positive electrode material. The SEM image of the copper-based sodium positive electrode material is shown in Figure 5. As shown in Figure 5, the morphology of the copper-based sodium positive electrode material is relatively poor, the surface is dirty and rough, and not round.

[0053] Experiments have found that directly adding copper elements to the precursor end for co-precipitation results in poor morphology, poor sphericity, and low tap compaction, low industrialization, and difficulty in achieving mass production.

[0054] Example 2

[0055] A copper-based sodium cathode material NaNi 0.3 Mn 0.30 Fe 0.3 Cu 0.1The preparation method of O2 specifically comprises the following steps:

[0056] (1) According to the molar ratio of Ni:Mn:Fe of 0.3:0.3:0.3, the corresponding nickel sulfate, manganese sulfate and ferrous sulfate raw materials were weighed to prepare a mixed solution with a concentration of 1.7 mol / L. The mixed solution, ammonia water and potassium hydroxide solution were introduced into a reactor for reaction. The concentration of ammonia water was 2 g / L and the concentration of potassium hydroxide solution was 10 mol / L. The reaction temperature was 70 ° C, the stirring frequency was 60 Hz, and the pH value was 10. Ni was co-precipitated to form 0.3 Mn 0.3 Fe 0.3 (OH) 1.8 A precursor having a particle size of 5 μm;

[0057] (2) The generated Ni 0.3 Mn 0.3 Fe 0.3 (OH) 1.8 The precursor is mixed with a certain amount of Na2CO3 and CuO. The mixing method is to mix them by a high-speed machine at a mixing speed of 1000 rpm and a mixing time of 30 minutes. The mixture is sintered at a high temperature of 980℃ for 20 hours to generate NaNi 0.3 Mn 0.3 Fe 0.3 Cu 0.1 O2 copper-based sodium positive electrode material.

[0058] Example 3

[0059] A copper-based sodium cathode material NaNi 0.20 Mn 0.30 Fe 0.2 Zn 0.1 Cu 0.2 The preparation method of O2 specifically comprises the following steps:

[0060] (1) According to the molar ratio of Ni:Mn:Fe:Zn of 0.2:0.30:0.2:0.1, the corresponding nickel sulfate, manganese sulfate, ferrous sulfate and zinc sulfate are weighed to prepare a mixed solution with a concentration of 2.0 mol / L. The mixed solution, ammonia water and sodium hydroxide solution are introduced into a reactor for reaction, wherein the concentration of ammonia water is 3 g / L and the concentration of sodium hydroxide solution is 10 mol / L. The reaction temperature is 50-90°C, the stirring frequency is 40-60 Hz, and the pH value is 10.5. Ni is co-precipitated to form 0.2 Mn 0.3 Fe 0.2 Zn 0.1 (OH) 1.6 A precursor having a particle size of 4 μm;

[0061] (2) The generated Ni 0.2 Mn 0.3 Fe 0.2 Zn 0.1 (OH) 1.6 The precursor is mixed with a certain amount of Na2CO3 and CuO. The mixing method is to mix them by a high-speed machine at a mixing speed of 1000 rpm and a mixing time of 30 minutes. The mixture is sintered at a high temperature of 950℃ for 15 hours to generate NaNi 0.2 Mn 0.3 Fe 0.2 Zn 0.1 Cu 0.2 O2 copper-based sodium positive electrode material.

[0062] Example 4

[0063] A copper-based sodium cathode material NaNi 0.30 Mn 0.40 Fe 0.15 Mg 0.1 Cu 0.05 The preparation method of O2 specifically comprises the following steps:

[0064] (1) According to the molar ratio of Ni:Mn:Fe:Mg of 0.3:0.40:0.15:0.1, the corresponding nickel sulfate, manganese sulfate, magnesium sulfate and ferrous sulfate were weighed to prepare a mixed solution with a concentration of 2 mol / L. The mixed solution, ammonia water and sodium hydroxide solution were introduced into a reactor for reaction. The concentration of ammonia water was 5 g / L and the concentration of sodium hydroxide solution was 10 mol / L. The reaction temperature was 70 ° C, the stirring frequency was 60 Hz, and the pH value was 9.5. Ni was co-precipitated to form 0.3 Mn 0.5 Fe 0.15 (OH) 1.9 A precursor having a particle size of 6 μm;

[0065] (2) The generated Ni 0.30 Mn 0.40 Fe 0.15 Mg 0.1 Cu 0.05 (OH) 1.9 The precursor is mixed with a certain amount of Na2CO3 and CuO. The mixing method is to mix them by a high-speed machine at a mixing speed of 1000 rpm and a mixing time of 30 minutes. The mixture is sintered at a high temperature of 980℃ for 20 hours to generate NaNi 0.30 Mn 0.40 Fe 0.15 Mg 0.1 Cu 0.05 O2 copper-based sodium positive electrode material.

[0066] Example 5

[0067] A copper-based sodium cathode material NaNi 0.20 Mn 0.50 Fe 0.15 Ca 0.1 Cu 0.05 The preparation method of O2 specifically comprises the following steps:

[0068] (1) According to the molar ratio of Ni:Mn:Fe:Ca of 0.2:0.50:0.15:0.1, the corresponding nickel sulfate, manganese sulfate, ferrous sulfate and calcium sulfate were weighed to prepare a mixed solution with a concentration of 1.8 mol / L. The mixed solution, ammonia water and sodium hydroxide solution were introduced into a reactor for reaction. The concentration of ammonia water was 1 g / L and the concentration of sodium hydroxide solution was 10 mol / L. The reaction temperature was 70 ° C, the stirring frequency was 60 Hz, and the pH value was 10.5. Ni was co-precipitated to form 0.20 Mn 0.50 Fe 0.15 Ca 0.1 Cu 0.05 (OH) 1.9 Precursor, the particle size of the precursor is 6 μm;

[0069] (2) The generated Ni 0.20 Mn 0.50 Fe 0.15 Ca 0.1 Cu 0.05 (OH) 1.9 The precursor is mixed with a certain amount of Na2CO3 and CuO. The mixing method is to mix them by a high-speed machine at a mixing speed of 1000 rpm and a mixing time of 30 minutes. The mixture is sintered at a high temperature of 980℃ for 20 hours to generate NaNi 0.20 Mn 0.50 Fe 0.15 Ca 0.1 Cu 0.05 O2 copper-based sodium positive electrode material.

[0070] Example 6

[0071] A copper-based sodium cathode material NaNi 0.30 Mn 0.20 Fe 0.2 Al 0.1 Cu 0.2 The preparation method of O2 specifically comprises the following steps:

[0072] (1) According to the molar ratio of Ni:Mn:Fe:Al of 0.3:0.20:0.2:0.1, the corresponding nickel sulfate, manganese sulfate, aluminum sulfate and ferrous sulfate were weighed to prepare a mixed solution with a concentration of 1.9 mol / L. The mixed solution, ammonia water and sodium hydroxide solution were introduced into a reactor for reaction. The concentration of ammonia water was 2 g / L and the concentration of sodium hydroxide solution was 10 mol / L. The reaction temperature was 70 ° C, the stirring frequency was 60 Hz, and the pH value was 10.5. Ni was co-precipitated to form 0.30 Mn 0.20 Fe 0.2 Al 0.1 (OH) 1.6 A precursor having a particle size of 5.5 μm;

[0073] (2) The generated Ni 0.30 Mn 0.20 Fe 0.2 Al 0.1 (OH) 1.6 The precursor is mixed with a certain amount of Na2CO3 and Cu(OH)2 by a high-speed mixing machine at a mixing speed of 1000 rpm for 30 min and sintered at 980 ° C for 20 h to generate NaNi 0.30 Mn 0.20 Fe 0.2 Al 0.1 Cu 0.2 O2 copper-based sodium positive electrode material.

[0074] Test example

[0075] To test the electrochemical performance of the materials, the copper-based sodium cathode materials obtained by sintering Examples 1-6 and Comparative Example 1 were used in button cells for relevant electrochemical performance tests. The button cell assembly method is as follows: the copper-based sodium cathode material, conductive carbon black, and polyvinylidene fluoride were prepared into a positive electrode material slurry in a mass ratio of 90:5:5. The slurry concentration was adjusted with N-methylpyrrolidone. The adjusted slurry was coated on aluminum foil using an automatic coating machine, dried in a vacuum drying oven at 120-130°C, and then roll-pressed and punched. The button cells were assembled in a glove box. The electrolyte was sodium perchlorate, with the solvent being a 1:1:1 ratio (volume ratio) of EC (ethylene carbonate): PC (propylene carbonate): EMC (ethyl methyl carbonate). The battery separator was a glass fiber separator, and the metal sodium sheet served as the battery negative electrode. The resulting button half-cell was tested: the button half-cell was charged and discharged in the voltage range of 2.5V-4.0V on a battery tester. The initial charge and discharge capacity at 0.1C was measured and the initial efficiency was calculated. The discharge capacity at 0.33C was also measured. Table 1 shows the test results.

[0076] Table 1: Electrical performance test results

[0077] As can be seen from Table 1, after the copper-based sodium positive electrode material prepared by the preparation method of the present invention is prepared into a battery, the first efficiency of the battery reaches 76.08% at 0.1C, the first charge specific capacity can reach 142.12 mAh / g, and the first discharge specific capacity can reach 110.23 mAh / g; the discharge specific capacity at 0.33C can reach 108.86 mAh / g.

Claims

1. A copper-based sodium positive electrode material, characterized in that: The chemical structural formula of the copper-based sodium positive electrode material is Na x M y Cu n O2, wherein M includes at least 3 of Li, K, Al, Ti, Cr, Mn, Fe, Co, Ni, Zn, Mg, Sn, Zr, Mo, Nb, Y, W, In, and Ge, 0.5≤x≤1, 0≤y<1, and y+n=1.

2. A method for preparing a copper-based sodium positive electrode material as claimed in claim 1, characterized in that: The following steps are involved: (1) Prepare a mixed solution containing M salt, add a complexing agent and an alkali solution, and perform a coprecipitation reaction to obtain M y (OH)2; (2) M y (OH)2 is mixed with a sodium source and a copper source, and calcined to obtain the copper-based sodium positive electrode material.

3. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (1), the M salt is at least one of an oxide, chloride, sulfate, nitrate, oxalate, citrate, carbonate and acetate of the M element.

4. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (1), the concentration of the mixed solution containing M salt is 1-2.5 mol / L.

5. The method for preparing a copper-based sodium positive electrode material according to claim 4, characterized in that: In step (1), the concentration of the mixed solution containing M salt is 1.7-2 mol / L.

6. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (1), the temperature of the coprecipitation reaction is 25-90°C.

7. The method for preparing a copper-based sodium positive electrode material according to claim 6, characterized in that: In step (1), the temperature of the coprecipitation reaction is 6075°C.

8. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (1), the pH of the coprecipitation reaction is 8.5-12.

5.

9. The method for preparing a copper-based sodium positive electrode material according to claim 8, characterized in that: In step (1), the pH of the coprecipitation reaction is 9-10.

5.

10. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (1), the coprecipitation reaction is also accompanied by stirring, and the stirring frequency is 30-60 Hz.

11. The method for preparing a copper-based sodium positive electrode material according to claim 10, characterized in that: In step (1), the stirring frequency is 40-50 Hz.

12. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (1), the complexing agent is aqueous ammonia with a concentration of 1-6 g / L.

13. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (1), the alkali solution includes at least one of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the alkali solution is 2-10 mol / L.

14. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (1), the coprecipitation reaction is carried out in a reactor.

15. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (1), the M y The particle size of (OH)2 is 4-12 μm.

16. The method for preparing a copper-based sodium positive electrode material according to claim 15, characterized in that: In step (1), the M y The particle size of (OH)2 is 4-7 μm.

17. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (2), the sodium source includes at least one of sodium carbonate, sodium hydroxide and sodium bicarbonate.

18. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (2), the copper source includes at least one of copper oxide, copper chloride, copper sulfate, copper nitrate, copper oxalate, copper citrate, copper carbonate and copper acetate.

19. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (2), the calcination temperature is 500-1100° C., and the calcination time is 5-20 hours.

20. The method for preparing a copper-based sodium positive electrode material according to claim 19, characterized in that: In step (2), the calcination temperature is 800-950° C., and the calcination time is 12-16 hours.

21. The method for preparing a copper-based sodium positive electrode material according to claim 2, characterized in that: In step (2), the mixing method is to mix by a mixer, the mixing speed is 800-1500rpm, and the mixing time is 10-60min.

22. A sodium ion battery, characterized in that: Including the copper-based sodium positive electrode material as described in claim 1.

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