CN115986106A - Positive electrode material, preparation method thereof and sodium ion battery - Google Patents

Abstract

The invention discloses a positive electrode material and a preparation method thereof, wherein the positive electrode material comprises a layered Mn-based oxide, and the chemical formula of the layered Mn-based oxide is Na_i A_j [Ni_x Mn_y □_z B_{(1‑x‑y‑z)} ]O₂ Wherein: □ represents vacancy in material, the vacancy content z in chemical formula satisfies 0 < z ≦ 0.1,0.85 < i ≦ 1.10,0 < j ≦ 0.06,0 < x ≦ 0.3,0.5 < y ≦ 0.80, A is one of Mg or Ca, and B is transition metal element. The structure of the anode material is formed by a transition metal layer doped with vacancy/metal ions and alkali gold doped with inert elementsThe O3 phase structure formed by alternately stacking the metal layers can promote oxygen to participate in oxidation reduction and inhibit O in the charge-discharge process₂ The release of (2) reduces volume expansion and contraction, expands alkali metal layers, increases the conductivity of the material, and realizes high energy, high multiplying power and long cycle performance. The invention also discloses a sodium ion battery containing the cathode material.

Description

Positive electrode material, preparation method thereof and sodium-ion battery

Technical Field

The invention relates to the technical field of positive electrode materials, in particular to a positive electrode material, a preparation method thereof and a sodium ion battery.

Background

The lithium ion battery is widely applied to industries such as energy storage equipment and electric vehicles by virtue of the advantages of high working voltage, large energy density, long cycle life and the like. However, the lithium resources have the disadvantages of small reserve, uneven distribution, low recovery rate and the like, and the rapidly growing market of the lithium ion battery inevitably increases the consumption of the lithium resources, and causes the price of the lithium to be continuously increased, so that the requirement of large-scale low-cost energy storage is difficult to meet. The content of sodium in the earth crust is thousands of times of that of lithium, and the method has the advantages of rich resources, wide distribution, low price and the like. The electrochemical properties of sodium ions are similar to those of lithium ions, and the replacement of lithium with sodium is technically completely feasible.

The research on the positive electrode material of the sodium-ion battery focuses on the aspects of layered oxides, polyanionic compounds, prussian blue and the like, and the positive electrode material of the layered Mn-based oxide is one of more ideal positive electrode materials of the sodium-ion battery due to high specific capacity, rich resources, environmental friendliness and simple preparation process. According to the occupied site and O sequence of sodium ions, the layered Mn-based oxide is generally divided into two types of oxides, namely a P2 type oxide and an O3 type oxide, compared with a P2 type anode, the O3 type anode has more sodium storage sites, and more sodium is extracted and inserted between layers through the redox reaction of the Mn-based oxide, so that higher specific capacity and working voltage are provided, and the sodium ion anode material with high energy density is obtained. However, reversible oxygen redox reaction (O)^2– /O₂^n– ) Accompanied by irreversible O₂ Loss and Jahn-Teller effect caused by the Mn-based oxide cathode material bring structural instability and particle cracking of the material, resulting in deterioration of cycle stability and voltage hysteresis.

Disclosure of Invention

In view of the above problems, a first aspect of the present invention provides a positive electrode material comprising a layered Mn-based oxide, a chemical formula of the layered Mn-based oxideFormula is Na_i A_j [Ni_x Mn_y □_z B_(1-x-y-z) ]O₂ ，

Wherein:

□ represents vacancies in a material, the vacancy content z in the chemical formula satisfies 0 < z ≦ 0.1,

0.85＜i≤1.10，0＜j≤0.06，0＜x≤0.3，0.5＜y≤0.80，

a is one of Mg or Ca;

b is a transition metal element.

In some embodiments, B is at least one of Zr, co, cu, ru, fe, nb, al, or W, illustratively any one of Zr, co, cu, ru, fe, nb, al, or W, two combinations of Zr and Co, two combinations of Co and Cu, three combinations of Co, cu, and Ru, four combinations of Zr, co, cu, and Fe, and the like.

In some embodiments, the layered Mn-based oxide has the chemical formula Na_0.95 A_0.05 [Ni_0.2 Mn_0.6 □_0.05 B_0.15 ]O₂ Further, A is Ca, B is Co and Cu, and illustratively, the layered Mn-based oxide has a chemical formula of Na_0.95 Ca_0.05 [Ni_0.2 Mn_0.6 □_0.05 Co_0.07 Cu_0.08 ]O₂ ，Na_0.95 Ca_0.05 [Ni_0.2 Mn_0.6 □_0.02 Co_0.1 Cu_0.08 ]O₂ But not limited thereto.

In some embodiments, the positive electrode material contains an O3 phase whose main component is Mn oxide, and whose structure is an O3 type structure in which vacancy/metal ion-doped transition metal layers and inert element (Mg or Ca) -doped alkali metal layers are alternately stacked. Further, the cathode material is a single crystal material, and the single crystal particle size Dv50 is 3.0-6.0um, and by way of example, the single crystal particle size Dv50 may be, but is not limited to, 3 μm, 4 μm, 5 μm, 6 μm. Further, the specific surface area of the particles is 0.2 to 0.8m² The specific surface area of the particles may be, but is not limited to, 0.2m, as an example² /g、0.3m² /g、0.4m² /g、0.5m² /g、0.6m² /g、0.7m² /g、0.8m² /g。

The second aspect of the present invention provides a method for preparing the above-mentioned cathode material, comprising the steps of:

(1) Sodium source, A (CH)₃ COO)₂ 、Mn(CH₃ COO)₂ ·4H₂ O、Ni(CH₃ COO)₂ ·4H₂ O and B (CH)₃ COO)₂ Adding the mixture into a citric acid aqueous solution according to a ratio, and uniformly stirring to obtain a mixed solution;

(2) Heating the mixed solution for reaction, filtering and drying to obtain precursor powder;

(3) Presintering the precursor powder in an air atmosphere to obtain a process product;

(4) And (4) sintering the process product at a high temperature in an air atmosphere, crushing, and sieving to obtain the anode material.

In the preparation method, the materials are added into the aqueous solution of citric acid, the materials are stirred uniformly to obtain the mixed solution at the atomic level, then the mixed solution is heated to react to obtain the precursor powder, the crystal structure is more complete, the materials with nonuniform microcosmic appearance can not be generated, the stress concentration effect of the materials in the charging and discharging process can be reduced, the structural stability of the materials is improved, all acetates are fully decomposed by pre-burning in the air atmosphere to form more crystal nuclei, and then the crystal nuclei are recombined into large single crystals by high-temperature sintering, so that the growth mode is favorable for increasing more vacancies in the materials, more oxygen is favorable for participating in reversible redox reaction, and more capacity is provided. Therefore, the modified O3 type Mn-based sodium ion cathode material is obtained by uniformly introducing vacancy/doping elements into the transition metal layer and the alkali metal layer by a sol-gel method. The preparation method ensures that all elements are uniformly distributed, and the cracking of the material caused by internal stress caused by the anisotropy of volume expansion can be avoided in the charging and discharging processes; the vacancy of the transition metal layer is helpful for the oxidation reaction of oxygen, and the doping of the transition metal layer and the alkali metal layer effectively inhibits O₂ Reaction, improving the conductivity of the material, increasing the mean voltage of the material and inhibiting phase change, thereby realizing the high-energy basis of the batteryAnd the material can be kept to have better cycle and rate performance on the basis. In addition, the whole process for preparing the cathode material is simple and is easy for industrial production.

In some embodiments, the sodium source is NaOH, na₂ CO₃ Or CH₃ And (4) COONa.

In some embodiments, in step (1), the molar ratio of sodium to metal element is (0.85-1.1): 1.

in some embodiments, the solution concentration of citric acid is 1-5wt%, and by way of example, the solution concentration of citric acid may be, but is not limited to, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%.

In some embodiments, the solid content of the mixed solution is 5-20wt%, and by way of example, the solid content of the mixed solution may be, but is not limited to, 5wt%, 8wt%, 11wt%, 14wt%, 17wt%, 20wt%.

In some embodiments, the heating temperature in step (2) is 60-90 ℃, and as an example, the heating temperature may be, but is not limited to, 60 ℃, 70 ℃, 80 ℃, 90 ℃.

In some embodiments, in step (2), the reaction time is 1 to 5 hours.

In some embodiments, in step (2), the drying is vacuum drying, the drying temperature is 80-150 ℃, and the drying time is 3-9h.

In some embodiments, the pre-firing temperature in step (3) is 300-600 ℃, and illustratively, the pre-firing temperature may be, but is not limited to, 300 ℃, 400 ℃, 500 ℃, 600 ℃. Further, the pre-sintering atmosphere is air, and the time is 6-12h.

In some embodiments, the temperature of the high-temperature sintering in step (4) is 850-950 ℃, and the temperature of the high-temperature sintering may be, for example, but not limited to, 850 ℃, 880 ℃, 900 ℃, 920 ℃, 950 ℃. Furthermore, the time is 8-16h.

In some embodiments, the size Dv50 of the crush control material is 3.0-6.0 μm.

In some embodiments, the sieving is 300 mesh sieving, but is not limited thereto.

Correspondingly, the invention also provides a sodium ion battery, and good cycle and rate performance can be obtained by adopting the positive electrode material.

The invention has the following beneficial effects:

(1) The chemical formula of the cathode material is Na_i A_j [Ni_x Mn_y □_z B_(1-x-y-z) ]O₂ The structure is an O3 phase structure formed by alternately stacking vacancy/metal ion doped transition metal layers and inert element doped alkali metal layers. This structure has the following advantages:

firstly, the structure is O3 type sodium ion battery anode material which has good sodium storage sites, so that the sodium ion battery anode material has higher capacity;

secondly, cation vacancies and metal ions with strong doping electronegativity are introduced into a material transition metal layer, random TM (transition metal) vacancies cause non-bonded O2p orbitals, and oxygen anions (O) are activated under the condition of removing more sodium^2– ) Redox, maintaining the charge neutrality of the material, thereby achieving higher capacity;

thirdly, doping metal ions with strong electronegativity with O in the transition metal layer of the material₂^n- The 2p orbital interaction becomes strong and the expansion of the Na layer becomes large, thereby enhancing the reversibility of the anion redox reaction and Na under high voltage⁺ Diffusion kinetics;

fourthly, the inactive components fixed in the alkali metal layer can directly destroy Na⁺ Vacancy ordering and as a strut to limit TM layer sliding, enhance sodium ion mobility and inhibit phase change;

fifthly, the stronger B-O bond can effectively reduce the loss of lattice oxygen and improve the redox reversibility of anions.

Therefore, the cathode material can promote oxygen to participate in oxidation reduction and inhibit O during charge and discharge₂ The volume expansion and contraction are reduced, the alkali metal layer is enlarged, the conductivity of the material is increased, and the high energy, high multiplying power and long cycle performance of the battery are realized.

Drawings

Fig. 1 is an SEM image of the positive electrode material prepared in example 1 of the present invention.

Fig. 2 is a XRD test result pattern of the cathode material prepared in example 1 of the present invention.

Fig. 3 is a graph of 1C cycle performance of the positive electrode materials prepared in examples 1 to 2 of the present invention and comparative examples 1 to 3.

Detailed Description

The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.

Example 1

This example provides a positive electrode material for sodium ion battery, which has a chemical formula

Na_0.95 Ca_0.05 [Ni_0.2 Mn_0.6 □_0.05 Co_0.07 Cu_0.08 ]O₂ The structure of the composite material is an O3 type structure formed by alternately stacking vacancy/metal ion doped transition metal layers and inert element doped alkali metal layers.

The preparation method of the positive electrode material of the sodium-ion battery comprises the following steps:

(1) Will CH₃ COONa、Ca(CH₃ COO)₂ 、Mn(CH₃ COO)₂ ·4H₂ O、Ni(CH₃ COO)₂ ·4H₂ O、Cu(CH₃ COO)₂ And Co (CH)₃ COO)₂ As a raw material, according to n_Ni ：n_Mn ：n_□ ：n_Co ：n_Cu ：n_Ca＝ 0.2：0.6：0.05：0.07：0.08：0.05，n_Na /(n_Ni +n_Mn +n_□ +n_Co +n_Cu ) Weighing materials according to the requirement of 0.95, then putting the materials into 2wt% citric acid water solution, and stirring for 2 hours to obtain a uniformly mixed solution with the solid content of 10 wt%;

(2) Reacting the mixed solution at 80 ℃ for 3h to obtain sol, filtering, and drying the filtered material in a vacuum oven at 110 ℃ for 6h to obtain yellow precursor powder;

(3) Sintering the precursor powder in a box type furnace with air at 450 ℃ for 6h to fully decompose all acetates to obtain a brown process product;

(4) And sintering the process product in a box type furnace with air at 900 ℃ for 12h, naturally cooling to room temperature, and then performing rough grinding and airflow fine grinding by using a rotary wheel mill to obtain the sodium-ion battery anode material.

Example 2

This example provides a positive electrode material for sodium ion battery, which has a chemical formula

Na_0.95 Ca_0.05 [Ni_0.2 Mn_0.6 □_0.02 Co_0.1 Cu_0.08 ]O₂ The structure of the metal ion-doped O3-type metal oxide film is an O3-type structure formed by alternately stacking vacancy/metal ion-doped transition metal layers and inert element-doped alkali metal layers.

The preparation method of the positive electrode material of the sodium-ion battery comprises the following steps:

(1) Will CH₃ COONa、Ca(CH₃ COO)₂ 、Mn(CH₃ COO)₂ ·4H₂ O、Ni(CH₃ COO)₂ ·4H₂ O、Cu(CH₃ COO)₂ And Co (CH)₃ COO)₂ As a raw material, according to n_Ni ：n_Mn ：n_□ ：n_Co ：n_Cu ：n_Ca＝ 0.2：0.6：0.02：0.1：0.08：0.05，n_Na /(n_Ni +n_Mn +n_□ +n_Co +n_Cu ) Weighing materials according to the requirement of 0.95, then putting the materials into 2wt% citric acid aqueous solution, and stirring for 2 hours to obtain a uniformly mixed solution with the solid content of 10 wt%;

(2) Reacting the mixed solution at 80 ℃ for 3h to obtain sol, filtering, and drying the filtered material in a vacuum oven at 110 ℃ for 6h to obtain yellow precursor powder;

(3) Sintering the precursor powder in a box type furnace with air at 550 ℃ for 6h to fully decompose all acetates to obtain a brown process product;

(4) And sintering the product in the process in a box furnace filled with air at 900 ℃ for 12h, naturally cooling to room temperature, and then performing coarse grinding by using a rotary wheel mill and fine grinding by using air flow to obtain the sodium-ion battery anode material.

Comparative example 1

The comparative example provides a positive electrode material of a sodium ion battery having a chemical formula

Na_0.95 Ca_0.05 [Ni_0.20 Mn_0.75 □_0.05 ]O₂ The structure of the catalyst is an O3 type structure formed by alternately stacking a transition metal layer with vacant sites and an alkali metal layer doped with inert elements.

The preparation method of the positive electrode material of the sodium-ion battery comprises the following steps:

(1) Will CH₃ COONa、Ca(CH₃ COO)₂ 、Mn(CH₃ COO)₂ ·4H₂ O、Ni(CH₃ COO)₂ ·4H₂ O as a raw material according to n_Ni ：n_Mn ：n_□ ：n_Ca＝ 0.2：0.75：0.05：0.05：0.05，n_Na /(n_Ni +n_Mn +n_□ ) Weighing materials according to the requirement of 0.95, then putting the materials into 2wt% citric acid water solution, and stirring for 2 hours to obtain a uniformly mixed solution with the solid content of 10 wt%;

(2) Reacting the mixed solution at 80 ℃ for 3h to obtain sol, filtering, and drying the filtered material in a vacuum oven at 110 ℃ for 6h to obtain yellow precursor powder;

(3) Sintering the precursor powder in a box furnace filled with air at 450 ℃ for 6h to fully decompose all acetate to obtain a brown process product;

(4) Sintering the product in the process for 12h at 900 ℃ in a box furnace filled with air, naturally cooling to room temperature, and then performing coarse grinding by a rotary wheel mill and fine grinding by airflow to obtain the sodium-ion battery cathode material with the granularity Dv50 of 3.6 mu m.

Comparative example 2

This comparative example provides a positive electrode material for a sodium ion battery of the formula

Na_0.95 Ca_0.05 [Ni_0.2 Mn_0.6 Co_0.12 Cu_0.08 ]O₂ The structure of the metal ion doped transition metal oxide film is an O3 type structure formed by alternately stacking metal ion doped transition metal layers and inert element doped alkali metal layers.

The preparation method of the positive electrode material of the sodium-ion battery comprises the following steps:

(1) Will CH₃ COONa、Ca(CH₃ COO)₂ 、Mn(CH₃ COO)₂ ·4H₂ O、Ni(CH₃ COO)₂ ·4H₂ O、Cu(CH₃ COO)₂ And Co (CH)₃ COO)₂ As a raw material, according to n_Ni ：n_Mn ：n_Co ：n_Cu ：n_Ca＝ 0.2：0.6：0.12：0.08：0.05，n_Na /(n_Ni +n_Mn +n_Co +n_Cu ) The materials were weighed to a requirement of 0.95.

(2) Uniformly mixing the precursor powder in a ball mill, and sintering for 6 hours at 450 ℃ in an air box furnace to fully decompose all acetates to obtain a brown process product;

(3) And sintering the product in the process in a box furnace filled with air at 900 ℃ for 12h, naturally cooling to room temperature, and then performing coarse grinding by using a rotary wheel mill and fine grinding by using air flow to obtain the sodium-ion battery anode material.

Comparative example 3

This comparative example provides a positive electrode material for a sodium ion battery of the formula

Na_0.95 [Ni_0.18 Mn_0.54 □_0.15 Co_0.06 Cu_0.07 ]O₂ The structure of the metal ion-doped O3-type structure is formed by alternately stacking vacancy/metal ion-doped transition metal layers and alkali metal layers.

The preparation method of the positive electrode material of the sodium-ion battery comprises the following steps:

(1) Will CH₃ COONa、Mn(CH₃ COO)₂ ·4H₂ O、Ni(CH₃ COO)₂ ·4H₂ O、Cu(CH₃ COO)₂ And Co (CH)₃ COO)₂ As a raw material, according to n_Ni ：n_Mn ：n_□ ：n_Co ：n_Cu＝ 0.2：0.6：0.05：0.07：0.08，n_Na /(n_Ni +n_Mn +n_□ +n_Co +n_Cu ) Weighing materials according to the requirement of 0.95, then putting the materials into 2wt% citric acid water solution, and stirring for 2 hours to obtain a uniformly mixed solution with the solid content of 10 wt%;

(2) Reacting the mixed solution at 120 ℃ for 3h to obtain sol, filtering, and drying the filtered material in a vacuum oven at 110 ℃ for 6h to obtain yellow precursor powder;

(3) Sintering the precursor powder in a box type furnace with air at 450 ℃ for 6h to fully decompose all acetates to obtain a brown process product;

(4) And sintering the process product in a box type furnace with air at 900 ℃ for 12h, naturally cooling to room temperature, and then performing rough grinding and airflow fine grinding by using a rotary wheel mill to obtain the sodium-ion battery anode material.

Fig. 1 shows an SEM image of the positive electrode material of the sodium-ion battery prepared in example 1. As can be seen from FIG. 1, the morphology of the positive electrode material of the sodium-ion battery is in a single crystal state, the particle size is uniform, the surface of the material is relatively smooth, and the amount of micro powder is small, so that the side reaction of the material and the electrolyte can be reduced, and the long cycle performance of the battery can be realized.

Fig. 2 shows an XRD pattern of the positive electrode material of the sodium-ion battery prepared in example 1. As can be seen from the XRD data in fig. 2, the sodium-ion battery positive electrode material has good crystallinity without diffraction peaks of other crystal phases, indicating that the prepared material has high purity and no other impurities are formed. In addition, XRD has peaks at 16.1 degrees and 41.2 degrees which are characteristic diffraction peaks of (003) and (104) of O3 phase, and thediffraction peak 2 theta angle of 003 crystal plane is less than 16.5 degrees, which shows that doping of transition metal layer and alkali metal layer obviously improves the space between transition metal layers and is helpful for reducing Na⁺ Diffusion energy barrier, and the rate capability of the material is improved.

Fig. 3 is a graph showing cycle data of examples 1-2 and comparative examples 1-3, and it is apparent from the graph that the capacity and cycle performance of examples 1-2 are superior to those of comparative examples 1-3 because the positive electrode material of the present invention has an O3 phase structure in which vacancy/metal ion doped transition metal layers and inert element doped alkali metal layers are alternately stacked.

The sodium ion battery positive electrode materials of examples 1-2 and comparative examples 1-3 were measured for their average particle diameter using a particle size analyzer and for their specific surface area using a macbeck specific surface area analyzer 3020, while being subjected to electrochemical performance tests, and the results thereof are shown in table 1.

And (3) electrochemical performance testing: mixing a positive electrode material of a sodium-ion battery as an active substance with PVDF (polyvinylidene fluoride) as a binder and a conductive agent (Super-P) according to a mass ratio of 95.5. Using 1mol/L LiPF with metallic lithium as a counter electrode₆ And mixing three-component mixed solvents according to EC: DMC: EMC =1 (1). The charge and discharge test of the button cell is carried out on a cell test system of blue-electricity electronic corporation of Wuhan, under the condition of 25 ℃, the constant current charge and discharge of 0.1C is carried out to 2.0V, then the constant current charge of 0.1C is carried out to 4.0V, then the constant voltage charge is carried out to 0.05C, then the constant current discharge of 0.1C is carried out to 2.0V, then the discharge capacity is the first discharge specific capacity, the ratio of the discharge capacity to the charge capacity is the first charge and discharge efficiency, the corresponding 100 th circle of discharge specific capacity is obtained after 100 times of circulation, and the 100 th circle of charge and discharge efficiency is calculated.

TABLE 1 test results

As can be seen from the results in table 1, compared with comparative examples 1 to 3, the positive electrode materials of the sodium ion batteries in examples 1 to 2 have better first discharge average voltage, first discharge specific capacity, first charge-discharge efficiency and cycle performance, which indicates that more sodium ions participate in the reaction and the sodium ions can be inserted back during the charge-discharge process of the positive electrode materials prepared in examples 1 to 2, and indicates that the power performance is better, i.e., the rate performance is better. After the materials are cycled for 100 circles, the specific capacities of the materials are respectively 128.4mAh/g and 126.5mAh/g, which are obviously higher than those of comparative examples 1-3, which shows that the materials have better cycle performance and stable structure in the cycle process.

In comparative example 1, since there is no strong B-O bond, the loss of lattice oxygen is severe, and the redox reversibility of anion is poor, resulting in poor cycle performance.

In comparative example 2, since cation vacancy is small, that is, TM (transition metal) vacancy causes non-bonded O2p orbital to be small, oxygen anion (O) is activated in case of charging^2– ) The redox is small, and the specific capacity of the material is low in order to maintain the electroneutrality of the material.

In comparative example 3, the voltage of the material was higher due to more vacancies, but the structural stability of the material was poor, resulting in poor cycle performance of the material.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it is not limited to the embodiments, and those skilled in the art should understand that the technical solutions of the present invention can be modified or substituted with equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims (10)

1. The cathode material is characterized by comprising a layered Mn-based oxide, wherein the layered Mn-based oxide has a chemical formula of Na_i A_j [Ni_x Mn_y □_z B_(1-x-y-z) ]O₂ ，

Wherein:

□ represents vacancies in a material, the vacancy content z in the chemical formula satisfies 0 < z ≦ 0.1,

0.85＜i≤1.10，0＜j≤0.06，0＜x≤0.3，0.5＜y≤0.80，

a is one of Mg or Ca;

b is a transition metal element.

2. The positive electrode material according to claim 1, wherein B is at least one of Zr, co, cu, ru, fe, nb, al, or W.

3. The method for producing a positive electrode material according to any one of claims 1 to 2, characterized by comprising the steps of:

(1) Sodium source, A (CH)₃ COO)₂ 、Mn(CH₃ COO)₂ ·4H₂ O、Ni(CH₃ COO)₂ ·4H₂ O and B (CH)₃ COO)₂ Adding the mixture into a citric acid aqueous solution according to a ratio, and uniformly stirring to obtain a mixed solution;

(2) Heating the mixed solution for reaction, filtering and drying to obtain precursor powder;

(3) Presintering the precursor powder in an air atmosphere to obtain a process product;

(4) And (4) sintering the process product at a high temperature in an air atmosphere, crushing, and sieving to obtain the anode material.

4. The method for producing a positive electrode material according to claim 3, wherein the sodium source is NaOH or Na₂ CO₃ Or CH₃ COONa.

5. The method for producing a positive electrode material according to claim 3, wherein the concentration of the solution of citric acid is 1 to 5wt%.

6. The method for producing a positive electrode material according to claim 3, wherein the solid content of the mixed solution is 5 to 20wt%.

7. The method for producing a positive electrode material according to claim 3, wherein the heating temperature in the step (2) is 60 to 90 ℃.

8. The method for preparing a positive electrode material according to claim 3, wherein the pre-firing temperature in the step (3) is 300 to 600 ℃.

9. The method for preparing a positive electrode material according to claim 3, wherein the temperature of the high-temperature sintering in the step (4) is 850 to 950 ℃.

10. A sodium ion battery comprising the positive electrode material according to any one of claims 1 to 2 or the positive electrode material produced by the method for producing a positive electrode material according to any one of claims 3 to 9.

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