Sodium-ion battery positive electrode material, preparation method thereof and positive plate

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a sodium ion battery positive electrode material, a preparation method thereof and a positive plate. The sodium ion battery positive electrode material provided by the invention comprises a layered transition metal oxide and a coating layer coating the surface of the layered transition metal oxide, the coating layer comprises MOn / 2 and NayMXz, M comprises a rare earth element, X is a halogen element, n is greater than or equal to 2 and less than or equal to 4, y is greater than or equal to 1 and less than or equal to 4, and z is greater than or equal to 3 and less than or equal to 8. The surface of the layered transition metal oxide is coated with the rare earth element-containing metal oxide MOn / 2 and the composite sodium halide NayMXz, the metal oxide obstructs the contact between the positive electrode material and an electrolyte, the dissolution of transition metal is inhibited, the occurrence of side reaction is reduced, the corrosion of the electrolyte is effectively reduced, and the composite sodium halide NayMXz has relatively high ionic conductivity, so that the service life of the lithium ion battery is prolonged. The positive electrode material can serve as a bridge between an electrolyte and the positive electrode material, sodium ion transmission is carried out, and the rate capability is not sacrificed while the cycling stability is improved.

Description

Technical Field

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

[0002] Currently, the commercialized layered oxide cathode materials for sodium ion batteries are Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O2(P2 type) and Na[Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 Cu 1 / 9 O2 (O3 type) has been widely studied and commercially applied due to its relatively high capacity and good processing performance, and some of them have been applied to products such as two-wheeled vehicles, electric vehicles, and energy storage devices. However, due to the high residual alkali content on the surface of these materials and the easy dissolution of sodium ions in the bulk phase of the materials, they cause continuous side reactions with the electrolyte during the battery cycle, producing gases such as hydrogen and hydrofluoric acid, which in turn leads to the destruction of the material structure and the consumption of the electrolyte, affecting the electrochemical performance and safety performance of the battery, and to a certain extent limiting its application.

[0003] The Chinese patent application with application publication number CN117594778A filed on February 23, 2024 discloses a sodium ion battery positive electrode material, a preparation method and application thereof, wherein the sodium ion battery positive electrode material comprises a sodium ion layered oxide and a coating layer coated on the surface of the sodium ion layered oxide, wherein the coating layer comprises a co-sintered product of aluminum fluoride and compound X (oxide, phosphate, boric acid or borate), specifically disclosing NaNi 1 / 3 Mn 1 / 3 Fe 1 / 3 The layered positive electrode material obtained by ball-milling and mixing O2 sodium ion layered oxide with 0.5wt% AlF3 and sintering at 600℃ for 5h. The coating layer material can effectively reduce the side reaction of HF in the electrolyte, effectively enhance the ion transport on the surface of the positive electrode material, and alleviate the residual alkali on the surface, thereby improving the electrochemical performance of the sodium ion battery positive electrode material.

[0004] However, the cycle performance and rate performance of sodium ion batteries made from the above-mentioned sodium ion battery positive electrode materials are still poor. Summary of the Invention

[0005] The object of the present invention is to provide a sodium ion battery positive electrode material to solve the problems of poor cycle performance and rate performance of existing sodium ion battery positive electrode materials.

[0006] The second object of the present invention is to provide a method for preparing a positive electrode material for a sodium ion battery, so as to solve the problem of poor cycle performance and rate performance of the existing positive electrode materials for sodium ion batteries.

[0007] The third object of the present invention is to provide a positive electrode sheet to solve the problem of poor cycle performance and rate performance of existing sodium ion battery positive electrode materials.

[0008] In order to solve the above technical problems, the technical solution of the sodium ion battery positive electrode material of the present invention is:

[0009] A sodium ion battery positive electrode material, comprising a layered transition metal oxide and a coating layer coated on the surface of the layered transition metal oxide; the coating layer comprises MO n / 2 and Na y MX z , wherein M includes a rare earth element, X is a halogen element, 2≤n≤4, 1≤y≤4, 3≤z≤8.

[0010] The present invention improves the existing technology and provides a positive electrode material for sodium ion batteries by coating a rare earth element metal oxide MO on the surface of a layered transition metal oxide. n / 2 and compound sodium halide Na y MX z , forming a surface passivation layer. The metal oxide in the passivation layer has good electrochemical stability, blocks the contact between the positive electrode material and the electrolyte, inhibits the dissolution of the transition metal, reduces the occurrence of side reactions, effectively reduces the corrosion of the electrolyte, ensures the stability of the material structure, improves the cycle performance and safety performance of the battery, and alleviates the gas production during the battery cycle, thereby improving the cycle stability and safety performance of the sodium ion battery; and the composite sodium halide Na y MX z It has high ionic conductivity and can act as a bridge between the electrolyte and the positive electrode material to transport sodium ions, thereby improving the cycle stability of the positive electrode material without sacrificing its rate performance.

[0011] In order to further improve the cycle performance and rate performance of the sodium ion battery cathode material, preferably, the MO n / 2 Including M'O n / 2 and M”O n / 2 , the Na y MX z for Na y M' a M” b X z , wherein M" is selected from one or more of Mg, Al, and Zn, M' is a rare earth element, and a+b=1. n / 2 and other metal oxides M"On / 2 The synergistic effect and Na y M a M' b X z Higher ionic conductivity can further improve the cycle performance and rate performance of sodium ion batteries.

[0012] Preferably, the rare earth element is selected from one or both of Y and La.

[0013] The technical solution of the method for preparing the positive electrode material for sodium ion batteries of the present invention is:

[0014] A method for preparing a positive electrode material for a sodium ion battery comprises the following steps: n After mixing with layered transition metal oxides and sintering, MX n The mass of X is 1 to 5 wt% of the layered transition metal oxide; M includes a rare earth element, X is a halogen element, and 2≤n≤4.

[0015] The preparation method of the sodium ion battery positive electrode material of the present invention utilizes the surface residual alkali (such as Na2O, NaOH and Na2CO3) of layered transition metal oxide and MX n React to generate metal oxide MO n / 2 and compound sodium halide Na y MX z The reaction has two stages: (1) The first stage: the surface residual base of the layered transition metal oxide and MX n The reaction generates sodium halide NaX and MO n / 2 , the reaction equation is as follows:

[0016] Na2O+MX n →NaX+MO n / 2

[0017] Na2CO3+MX n →NaX+MO n / 2 +CO2↑

[0018] NaOH+MX n →NaX+MO n / 2 +H2O↑

[0019] (2) The second stage: The sodium halide NaX generated in the first stage continues to react with excess MX n The reaction generates compound sodium halide Na y MX z , the reaction equation is as follows:

[0020] NaX+MX n →Na y MX z

[0021] Wherein, M includes a rare earth element, X is a halogen element, 2≤n≤4; 1≤y≤4, 3≤z≤8.

[0022] The preparation method provided by the present invention makes full use of the residual alkali on the surface of the positive electrode material, so that the in-situ generated coating layer is in close contact with the positive electrode material, and has better stability than various mechanical mixing methods; and MX n It can fully react with the residual alkali on the surface of the positive electrode material, avoiding the gelation of PVDF glue due to the denaturation of the slurry alkalinity during the slurry making process, and effectively improving the processing performance of the material.

[0023] In order to further improve the cycle performance and rate performance, preferably, the MX n Including M'X n and M”X n ; wherein M" is selected from one or more of Mg, Al, and Zn, and M' is a rare earth element.

[0024] In order to further improve the cycle performance and rate performance, preferably, M'X n and M”X n The mass ratio is (1.2~1.5):(0.3~0.5).

[0025] In order to further improve the crystallinity of the coating layer and thus improve the cycle performance and rate performance, preferably, the sintering temperature is 300-750° C. and the sintering time is 6-8 hours.

[0026] In order to further remove residual alkali on the surface of the layered transition metal oxide and improve battery stability, preferably, the hydroxide content on the surface of the layered transition metal oxide is 10-15%, and the carbonate content is 1-1.5%.

[0027] The technical solution of the positive electrode sheet of the present invention is:

[0028] A positive electrode sheet comprises the sodium ion battery positive electrode material or the sodium ion battery positive electrode material prepared by the method for preparing the sodium ion battery positive electrode material.

[0029] The positive electrode sheet provided by the present invention can improve the cycle performance and rate performance of the sodium ion battery by utilizing the sodium ion battery positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 To verify the XRD patterns of the products obtained from the three schemes in the experiment;

[0031] Figure 2 Graph showing the cycle performance test results of batteries made of the sodium ion positive electrode materials of the embodiment and comparative example;

[0032] Figure 3 Graph showing rate performance test results of batteries made of sodium ion positive electrode materials according to Examples and Comparative Examples;

[0033] Figure 4 Graph showing the test results of residual alkali content on the surface of the sodium ion positive electrode materials of the embodiment and the comparative example. DETAILED DESCRIPTION

[0034] The technical concept of the sodium ion battery positive electrode material of the present invention is as follows:

[0035] Conventional coating with oxides, phosphates, and borates can, to a certain extent, eliminate the problem of residual alkalinity on the surface and improve the interfacial stability of the cathode, but surface lattice oxygen escape still exists. Existing technologies improve the electrochemical performance of sodium-ion battery cathode materials by co-sintering aluminum fluoride and compound X (oxide, phosphate, boric acid, or borate), but the results are still limited.

[0036] The present invention coats the surface of the layered transition metal oxide with a rare earth element metal oxide MO n / 2 and compound sodium halide Na y MX z , using MO n / 2 The barrier effect reduces the side reaction and utilizes the composite sodium halide Na y MX z The conductivity of the cathode material is used for sodium ion transport, which improves the cycle stability of the cathode material without sacrificing its rate performance.

[0037] The preparation method of the sodium ion battery positive electrode material provided by the present invention comprises the following steps: n After mixing with layered transition metal oxides and sintering, MX n The mass of the halogen element X is 1-5wt% of the layered transition metal oxide; wherein M includes a rare earth element, X is a halogen element, and 2≤n≤4.

[0038] It can be understood that the structure of the layered transition metal oxide is P2 type or O3 type.

[0039] In a specific embodiment, the mixing is performed at 1000-1500 rpm for 10-15 min.

[0040] In a specific embodiment, the sintering is performed in an inert atmosphere or air. The inert atmosphere includes nitrogen and argon.

[0041] In a specific embodiment, the positive electrode sheet is prepared from a sodium ion battery positive electrode material, a conductive agent, and a binder in a mass ratio of (85-90): (5-10): (5-10).

[0042] Understandably, when MX n The M in includes only rare earth elements, namely MX n For M'X n When sintering, the corresponding rare earth metal oxide M'O n / 2 and composite sodium halide containing rare earth elements Na y M'X z ; When MX n For M'X n and M”X n When sintering, the corresponding rare earth metal oxide M'O n / 2 、Other metal oxides M”O n / 2 and complex sodium halide Na containing rare earth elements and other metal elements y M' a M” b X z .

[0043] The preparation method of the sodium ion battery positive electrode material provided by the present invention has two stages of reaction. When the MX n When the amount of NaX generated in the first stage is insufficient to completely react with the sodium halide NaX, the coating layer in the positive electrode material of the sodium ion battery also includes NaX.

[0044] The embodiments of the present invention are further described below with reference to specific examples. Unless otherwise specified, the chemical reagents involved in the following examples are all commercially available conventional products.

[0045] 1. Specific embodiments of the sodium ion battery positive electrode material and preparation method thereof of the present invention

[0046] Example 1

[0047] The preparation method of the sodium ion battery positive electrode material of this embodiment is as follows:

[0048] Layered transition metal oxide NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and 1wt% YCl3 (calculated as chlorine element mass) were placed in a high-speed mixing device and mixed at a speed of 1200 rpm for 15 minutes to obtain a uniform mixture; the mixture was then placed in a box furnace and heated in a nitrogen atmosphere with a flow rate of 0.05m 3 / h, react at 350°C for 8h, and cool to obtain a coated sodium ion battery positive electrode material.

[0049] The coated sodium ion battery positive electrode material obtained in this embodiment is the sodium ion battery positive electrode material provided by the present invention, including layered transition metal oxide NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 O2 and a coating layer coated on the surface of a layered transition metal oxide; the coating layer is Y2O3 and Na3YCl6; the thickness of the coating layer is 2 to 50 nm.

[0050] Example 2

[0051] The preparation method of the sodium ion battery positive electrode material of this embodiment is as follows:

[0052] Layered transition metal oxide NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and 1.2wt% LaF3 (calculated as fluorine element mass) and 0.3wt% AlF3 (calculated as fluorine element mass) are placed in a high-speed mixing device and mixed at a speed of 1500 rpm for 10 minutes to obtain a uniform mixed material; the mixed material is then placed in a box furnace and heated in a nitrogen atmosphere with a flow rate of 0.05m 3 / h, react at 750℃ for 6h, and cool to obtain a coated sodium ion battery positive electrode material.

[0053] The coated sodium ion battery positive electrode material obtained in this embodiment is the sodium ion battery positive electrode material provided by the present invention, including layered transition metal oxide NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and a coating layer coated on the surface of a layered transition metal oxide; the coating layer is Al2O3, La2O3 and Na3La 0.8 Al 0.2 F6; the coating layer thickness is 2 to 50 nm.

[0054] Example 3

[0055] The preparation method of the sodium ion battery positive electrode material of this embodiment is as follows:

[0056] Layered transition metal oxide NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and 1.5wt% LaF3 (calculated as fluorine element mass) were placed in a high-speed mixing device and mixed at a speed of 1500 rpm for 10 minutes to obtain a uniform mixed material; the mixed material was then placed in a box furnace and heated in a nitrogen atmosphere with a flow rate of 0.05m 3 / h, react at 750℃ for 6h, and cool to obtain a coated sodium ion battery positive electrode material.

[0057] The coated sodium ion battery positive electrode material obtained in this embodiment is the sodium ion battery positive electrode material provided by the present invention, including layered transition metal oxide NaNi 1 / 3 Fe1 / 3 Mn 1 / 3 O2 and a coating layer coated on the surface of a layered transition metal oxide; the coating layer is La2O3 and Na3LaF6; and the thickness of the coating layer is 2 to 50 nm.

[0058] Example 4

[0059] The preparation method of the sodium ion battery positive electrode material of this embodiment is as follows:

[0060] Layered transition metal oxide NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and 5wt% YF3 (calculated as fluorine element mass) were placed in a high-speed mixing device and mixed at a speed of 1500 rpm for 10 minutes to obtain a uniform mixed material; the mixed material was then placed in a box furnace and heated in a nitrogen atmosphere with a flow rate of 0.05m 3 / h, react at 750℃ for 6h, and cool to obtain a coated sodium ion battery positive electrode material.

[0061] The coated sodium ion battery positive electrode material obtained in this embodiment is the sodium ion battery positive electrode material provided by the present invention, including layered transition metal oxide NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and a coating layer coated on the surface of a layered transition metal oxide; the coating layer is Y2O3 and Na3YF6; and the thickness of the coating layer is 2 to 50 nm.

[0062] 2. Specific Embodiments of the Positive Electrode Sheet of the Present Invention

[0063] Example 5

[0064] The preparation method of the positive electrode sheet of this embodiment is as follows: the coated sodium ion battery positive electrode material of Example 1 or 2 or 3 or 4, the conductive agent SP, and the binder PVDF are mixed in a mass ratio of 90:5:5, and an appropriate amount of N-methylpyrrolidone (NMP) solution is added. The ball milling equipment is used in a dry environment at room temperature to ball mill the mixture for 1 hour to form a slurry. The coating equipment is used to set the parameters for coating. The coated positive electrode sheet is dried in a vacuum oven at a drying temperature of 120°C for 2 hours; the dried electrode sheet is rolled to ensure that the thickness of the electrode sheet after rolling is 0.10±0.05 mm, and then cut into small discs with a diameter of 12 mm, i.e., the positive electrode sheet.

[0065] 3. Comparative Examples

[0066] Comparative Example 1

[0067] The positive electrode material of the sodium ion battery in this comparative example is a commercially available layered transition metal oxide NaNi1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0068] Comparative Example 2

[0069] The preparation method of the sodium ion battery positive electrode material of this comparative example is as follows:

[0070] Layered transition metal oxide NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and 1.5wt% of its mass of AlF3 (calculated as the mass of fluorine element) are placed in a high-speed mixing device and mixed at a speed of 1200 rpm for 15 minutes to obtain a uniformly mixed mixture; the mixture is then placed in a box furnace and reacted at a temperature of 550°C for 4 hours in an air atmosphere, and then cooled to obtain a coated sodium ion battery positive electrode material.

[0071] The coated sodium ion battery positive electrode material obtained in this embodiment is the sodium ion battery positive electrode material provided by the present invention, including layered transition metal oxide NaNi 2 / 9 Fe 1 / 3 Mn 1 / 3 Cu 1 / 9 O2 and a coating layer coated on the surface of the layered transition metal oxide; the coating layer is Al2O3 and Na3AlF6.

[0072] IV. Experimental Examples

[0073] (1) Verification test

[0074] This verification test indirectly proves that the coating layer obtained by the present invention includes metal oxide and composite halogen, and the test verification method is as follows:

[0075] Aluminum fluoride (AlF3) and sodium carbonate (Na2CO3) were weighed according to three molar ratios of 2:3 (Scheme 1), 3:3 (Scheme 2), and 4:3 (Scheme 3), respectively, and placed in high-speed mixing equipment, mixed at a speed of 1200 rpm for 15 minutes to obtain uniformly mixed materials. The three mixed materials were then placed in a box furnace, reacted at 400°C for 5 hours in an air atmosphere, and after cooling, the materials were taken out and packaged in aluminum-plastic bags, marked as Scheme 1, 2, and 3 respectively, and XRD tests were performed.

[0076] The results of material mass changes in each scheme during the sintering process of this test example are shown in Table 1. The actual sintering rates of schemes 1, 2, and 3 are 72.56%, 76.86%, and 79.63%, respectively.

[0077] Table 1 Material quality change results of each scheme in the sintering process

[0078] Trial plan Material ratio Material mass before burning / g Mass of material after burning / g Burning rate / % Option 1 2:3 4.720 3.425 72.56 Option 2 1:1 4.867 3.741 76.86 Option 3 4:3 4.853 3.865 79.63

[0079] XRD test results are as follows Figure 1 As shown, where the horizontal axis is the 2θ angle (Two-Theta, deg, °) and the vertical axis is the diffraction intensity (intensity), the XRD peaks of the product of Scheme 1 mainly match well with the NaF and Al2O3 crystal forms, the XRD peaks of the product of Scheme 2 mainly match well with the NaF, Na3AlF6 and Al2O3 crystal forms, and the XRD peaks of the product of Scheme 3 mainly match well with the Na3AlF6 and Al2O3 crystal forms; combined with the analysis of the burn-in rate and XRD results, it can be seen that the following chemical reactions occurred in Schemes 1, 2 and 3 respectively:

[0080] Scheme 1 Reaction 1: 2AlF3+3Na2CO3=2Al2O3+6NaF+3CO2↑

[0081] Scheme 2 Reaction 2: 3AlF3+3Na2CO3=Al2O3+Na3AlF6+3NaF+3CO2↑

[0082] Scheme 3 Reaction 3: 4AlF3+3Na2CO3=2Al2O3+2Na3AlF6+3CO2↑

[0083] The theoretical burn-in yields of reactions 1, 2, and 3 are approximately 72.97%, 76.97%, and 79.94%, respectively, which are basically consistent with the actual burn-in yields of schemes 1, 2, and 3 within the error range.

[0084] The results of the comprehensive verification test show that acidic aluminum fluoride can react with alkaline sodium carbonate to generate aluminum oxide and sodium fluoride or sodium fluoroaluminate or a complex of the two.

[0085] (2) Performance testing

[0086] Charge and discharge test:

[0087] The sodium ion positive electrode materials of the examples and comparative examples were fabricated into positive electrode sheets using the method of Example 5. This positive electrode sheet was then placed in a 2032-size button battery case. A button cell was assembled with a sodium sheet, a glass fiber separator, a positive electrode sheet, and an electrolyte containing sodium hexafluorophosphate. Electrochemical charge and discharge tests were then conducted over a voltage range of 2.0V to 4.0V, using a cycle of 0.1C / 0.5C / 1C.

[0088] The test results of cycle performance and rate performance are as follows: Figure 2 and Figure 3 As shown. Figure 2 and Figure 3As shown, the capacity retention rates of Examples 1, 2, 3, 4 and Comparative Examples 1 and 2 after 50 cycles at 1C are 96.87%, 98.00%, 97.09%, 98.26% and 95.50%, 96.18%, respectively, indicating that the cycle performance of the positive electrode material with a coating layer constructed by the present invention is significantly improved; at the same time, the 0.1C / 1C rate properties of Examples 1, 2, 3, 4 and Comparative Examples 1 and 2 are 94.88%, 95.01%, 95.10%, 94.53% and 94.17%, 93.59%, respectively, indicating that the rate properties of the positive electrode material with a coating layer constructed by the present invention are also improved.

[0089] Residual alkali content test:

[0090] The sodium ion positive electrode materials of the embodiment and the comparative example were tested for residual alkali content using the residual alkali content test method (GB / T 41704-2022) in the lithium ion battery positive electrode material detection method. The test results are as follows: Figure 4 shown.

[0091] from Figure 4 It can be seen that compared with Comparative Example 1, the hydroxide content in the surface residual alkali of Examples 1, 2, 3, and 4 was reduced from 12.10% in Comparative Example 1 to 4.56%, 0.62%, 0.78%, and 0.25%, respectively; the hydroxide content in Comparative Example 2 was reduced to 1.68% compared with Comparative Example 1. Although there was a reduction, the reduction was not as great as that in Examples 2 and 3. Similarly, the carbonate content in Examples 1, 2, 3, and 4 was reduced from 1.31w% in Comparative Example 1 to 0.87%, 0.21%, 0.25%, and 0.05%, respectively; the carbonate content in Comparative Example 2 was reduced to 0.37% compared with Comparative Example 1. This further proves that the preparation method provided by the present invention utilizes the reaction of the surface residual alkali of the positive electrode material with a halide to form a surface passivation layer comprising a metal oxide and a composite sodium halide, and in situ constructs a coating layer, so that the sodium ion battery prepared from the positive electrode material having the coating layer has better cycle stability and safety.

[0092] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sodium ion battery cathode material, characterized in that It comprises a layered transition metal oxide and a coating layer coated on the surface of the layered transition metal oxide; the coating layer comprises MO n / 2 and Na y MX z , wherein M includes a rare earth element, X is a halogen element, 2≤n≤4, 1≤y≤4, 3≤z≤8.

2. The sodium ion battery positive electrode material according to claim 1, wherein The MO n / 2 Including M'O n / 2 and M”O n / 2 , the Na y MX z for Na y M' a M” b X z , wherein M" is selected from one or more of Mg, Al, and Zn, M' is a rare earth element, and a+b=1.

3. The sodium ion battery positive electrode material according to claim 1 or 2, wherein The rare earth element is selected from one or two of Y and La.

4. A method for preparing a positive electrode material for a sodium ion battery according to any one of claims 1 to 3, characterized in that: The following steps are involved: MX n After mixing with layered transition metal oxides and sintering, MX n The mass of X is 1~5wt% of the layered transition metal oxide; Wherein M includes a rare earth element, X is a halogen element, and 2≤n≤4.

5. The method for preparing a positive electrode material for a sodium ion battery according to claim 4, wherein: The MX n Including M'X n and M”X n ; wherein M" is selected from one or more of Mg, Al, and Zn, and M' is a rare earth element.

6. The method for preparing a positive electrode material for a sodium ion battery according to claim 4, wherein: M'X n and M”X n The mass ratio is (1.2~1.5): (0.3~0.5).

7. The method for preparing a positive electrode material for a sodium ion battery according to claim 4, wherein: The sintering temperature is 300-750° C., and the sintering time is 6-8 hours.

8. The method for preparing a positive electrode material for a sodium ion battery according to claim 4, wherein: The surface hydroxide content of the layered transition metal oxide is 10-15%, and the carbonate content is 1-1.5%.

9. A positive electrode sheet, characterized in that: The invention relates to a sodium ion battery positive electrode material according to any one of claims 1 to 3 or a sodium ion battery positive electrode material prepared by the method for preparing the sodium ion battery positive electrode material according to any one of claims 4 to 8.

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