Positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a positive electrode material and a preparation method and application thereof. The positive electrode material comprises a positive electrode material matrix and a coating layer coating at least part of the surface of the positive electrode material matrix, and the coating layer comprises Na3Zr2Si2PO12 and carbon; the positive electrode material base body comprises a nickel-iron-manganese positive electrode material base body; the positive electrode material has good air stability and good processing stability, can bear severe storage, transportation and processing processes, and also has high energy density and good cycle stability and rate capability.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and particularly relates to a cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] In the field of secondary batteries, sodium-ion batteries have broad application prospects due to their cost advantages. The working principle of sodium-ion batteries is similar to that of lithium-ion batteries, and they utilize the reversible insertion and extraction of sodium ions between the positive and negative electrodes to achieve energy storage and release. Starting from the existing sodium-ion battery structures and materials, the cathode material is an important factor affecting the performance of sodium-ion batteries. Among the commonly used sodium-ion battery cathode materials, layered oxide cathode materials have a relatively high theoretical capacity, which is generally of the O3 phase or P2 phase or O3-P2 composite phase structure. Among them, the P2-type transition metal layered oxide cathode material has a high voltage platform and excellent rate performance. The current mainstream P2-phase materials are mostly based on NiMn, with good cycle stability and a low residual alkali level. However, in this material, the capacity is solely provided by the valence change of Ni, and the specific capacity is relatively low. Therefore, NiFeMn-based cathode materials obtained by introducing the valence change of Fe have been further developed. The NiFeMn-based cathode material has a relatively high specific capacity, but it is extremely easy to absorb water in the air, and its processing stability and cycle stability are very poor. Summary of the Invention

[0003] Therefore, the present invention provides a cathode material, a preparation method thereof, and an application thereof. The preparation method of the cathode material is simple, and it has good air stability, high energy density, as well as good cycle stability and rate performance.

[0004] For this reason, the present invention provides the following technical solutions.

[0005] The present invention provides a cathode material, which includes a cathode material matrix and a coating layer covering at least a part of the surface of the cathode material matrix. The coating layer includes Na3Zr2Si2PO 12 and carbon; the cathode material matrix includes a nickel-iron-manganese cathode material matrix.

[0006] Optionally, the mass ratio of Na3Zr2Si2PO 12 to carbon in the coating layer is 100:5 to 20.

[0007] Optionally, the mass ratio of the cathode material matrix to the coating layer is 100:2 to 5.

[0008] Optionally, the general formula of the cathode material matrix is Na m Ni x Fe y Mn zO2, where x + y + z = 1, 0.2 ≤ x ≤ 0.3, 0.2 ≤ y ≤ 0.3, 0.4 ≤ z ≤ 0.6, 0.67 ≤ m ≤ 0.71.

[0009] The present invention provides a method for preparing the above positive electrode material, comprising the following steps: S1: Mix Na3Zr2Si2PO 12 , a carbon source, and water to obtain a coating slurry; S2: Mix the positive electrode material matrix and the coating slurry, and sinter to obtain the positive electrode material.

[0010] In the method for preparing the above positive electrode material provided by the present invention, typically but not limitedly, when mixing the positive electrode material matrix and the coating slurry, the coating slurry can be sprayed onto the positive electrode material matrix while stirring the positive electrode material matrix to make the coating slurry and the positive electrode material matrix more uniformly mixed.

[0011] Optionally, in the coating slurry, the mass ratio of Na3Zr2Si2PO 12 to the carbon source is 100:5 to 20.

[0012] Optionally, in the coating slurry, the solid content is 40% to 50%.

[0013] Optionally, the carbon source includes at least one of graphene oxide, graphene, carbon nanotubes, and carbon fibers.

[0014] Optionally, in S2, the mass ratio of the positive electrode material matrix to the coating slurry is 100:5 to 10.

[0015] Optionally, in S2, the sintering is carried out in a protective atmosphere, the temperature is 600 to 700 °C, and the time is 6 to 10 h; optionally, the protective atmosphere includes a noble gas atmosphere and / or a nitrogen atmosphere. Carrying out the second sintering in a protective atmosphere can prevent the carbon source from being oxidized and decomposed. Typically but not limitedly, the concentration of the protective atmosphere during the sintering process can be maintained at 99.999% by introducing the corresponding protective gas into the furnace.

[0016] Optionally, in S1, the method of mixing Na3Zr2Si2PO 12 , the carbon source, and water includes stirring; optionally, the stirring speed is 200 to 500 r / min, and the time is 1 to 5 h. Stirring at a high speed for a period of time can fully disperse Na3Zr2Si2PO 12 and the carbon source in water, avoid their agglomeration during subsequent operations, and facilitate subsequent coating.

[0017] Optionally, the step of preparing the cathode material matrix includes mixing a nickel-iron-manganese precursor and a sodium source, sintering, and pulverizing to obtain the cathode material matrix; optionally, in the step of preparing the cathode material matrix, the sintering is carried out in an oxygen-containing atmosphere at a temperature of 900-1000 °C for 10-15 h. Typically and non-limitingly, the oxygen-containing atmosphere during sintering can be maintained by introducing air into the furnace, and the air introduction rate is 5 m 3 / h.

[0018] Optionally, the sodium source includes soluble sodium salts; optionally, the sodium source includes at least one of sodium carbonate and sodium bicarbonate.

[0019] The present invention also provides the application of the above cathode material or the cathode material prepared by the above preparation method in a secondary battery; optionally, the secondary battery includes a sodium-ion battery. Typically and non-limitingly, an assembly method of a sodium-ion button half-cell can be: mixing the obtained cathode material with a conductive agent acetylene black and a binder PVDF in a mass ratio of 80-95:2-12:2-8, adding an appropriate amount of 1-methyl-2-pyrrolidone and ball-milling for 1-3 h to obtain a slurry, coating it on an aluminum sheet, drying and pressing to form a positive electrode sheet, using a sodium metal sheet as the negative electrode, sodium hexafluorophosphate (NaPF6) as the electrolyte, and a mixture of dimethyl carbonate and ethylene carbonate with a volume ratio of 1:1 as the solvent, and assembling it into a 2032 button battery.

[0020] The beneficial effects of the present invention are:

[0021] The cathode material provided by the present invention includes a cathode material matrix and a coating layer covering at least part of the surface of the cathode material matrix, and the coating layer includes Na3Zr2Si2PO 12 and carbon; the cathode material matrix includes a nickel-iron-manganese cathode material matrix. This cathode material has good air stability, good processing stability, high energy density, and good cycle stability and rate performance. Among them, the use of a nickel-iron-manganese cathode material matrix results in a material with a relatively high specific capacity; using Na3Zr2Si2PO 12 , a carbon source as a coating slurry, the obtained Na3Zr2Si2PO 12 composite carbon coating layer has strong hydrophobicity, which can reduce the erosion of free water on the cathode material, improve the air stability of the material, enable the material to withstand relatively harsh storage, transportation, and processing processes, and improve its processing stability. In addition, the Na3Zr2Si2PO 12 composite carbon coating layer also has good elasticity and conductivity. The excellent elasticity enables the coating layer to be stretched as the crystal expands during the charge and discharge cycle without breaking and still maintain a good coating state. This can avoid the erosion and damage of the electrolyte to the internal material after the coating layer breaks, and effectively enhance the cycle stability and rate performance of the material.

[0022] The preparation method of the above-mentioned cathode material provided by the present invention includes the following steps: S1: Mix Na3Zr2Si2PO 12 , a carbon source, and water to obtain a coating slurry; S2: Mix the cathode material matrix and the coating slurry, and sinter to obtain the cathode material. This preparation method is convenient and simple. The required cathode material can be obtained through simple mixing and sintering steps, which is convenient for the large-scale preparation of the cathode material. Description of the Drawings

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 This is the SEM image of the cathode material obtained in Example 1 of the present invention, with a magnification of 10,000 times. Specific Embodiments

[0025] The following embodiments are provided to better further understand the present invention. They are not limited to the best embodiments, and do not limit the content and protection scope of the present invention. Any product that is the same as or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features falls within the protection scope of the present invention.

[0026] For those embodiments in which specific experimental steps or conditions are not specified, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments whose manufacturers are not specified, they are all conventional reagent products that can be obtained through commercial purchase.

[0027] Example 1

[0028] This example provides a cathode material and its preparation method, including the following steps:

[0029] (1) Take 5.0 kg of Ni 0.30 Fe 0.20 Mn 0.50 (OH)2 precursor and 2.0 kg of sodium carbonate, mix them in a high-speed mixer, send them into a box furnace, and introduce air into the furnace at a rate of 5 m 3 / h to maintain an oxygen-containing atmosphere, sinter at 1000 °C for 12 h, and pulverize to obtain the cathode material matrix.

[0030] (2) Take 20 g of Na3Zr2Si2PO12 The solid electrolyte powder was uniformly dispersed in 30 g of graphene oxide slurry (graphene oxide content 6 wt%), and stirred in a stirrer at a rotation speed of 250 r / min for 1 h to obtain Na3Zr2Si2PO 12 composite graphene oxide-coated slurry.

[0031] (3) Take 500 g of the positive electrode material matrix obtained in (1), put it into a high-speed mixer and stir, while spraying the coated slurry obtained in (2) into it. After all the slurry is sprayed and mixed evenly, it is sent into a box furnace. The box furnace is filled with a nitrogen-containing atmosphere (nitrogen is introduced at a rate of 5 m 3 / h to maintain a nitrogen concentration of 99.999%), and sintered at 600 °C for 6 h to obtain the positive electrode material.

[0032] Observe the SEM image of the positive electrode material prepared in Example 1, as shown in Figure 1 .

[0033] Example 2

[0034] This example provides a positive electrode material and a preparation method thereof, including the following steps:

[0035] (1) Take 5.0 kg of Ni 0.30 Fe 0.20 Mn 0.50 (OH)2 precursor and 2.0 kg of sodium carbonate, mix them in a high-speed mixer, send them into a box furnace, and introduce air into the furnace at a rate of 5 m 3 / h to maintain an oxygen-containing atmosphere, sinter at 1000 °C for 10 h, and pulverize to obtain the positive electrode material matrix.

[0036] (2) Take 20 g of Na3Zr2Si2PO 12 The solid electrolyte powder was uniformly dispersed in 23 g of carbon fiber slurry (carbon fiber content 5 wt%), and stirred in a stirrer at a rotation speed of 200 r / min for 5 h to obtain Na3Zr2Si2PO 12 composite carbon fiber-coated slurry.

[0037] (3) Take 430 g of the positive electrode material matrix obtained in (1), put it into a high-speed mixer and stir, while spraying the coated slurry obtained in (2) into it. After all the slurry is sprayed and mixed evenly, it is sent into a box furnace. The box furnace is filled with a nitrogen-containing atmosphere (nitrogen is introduced at a rate of 5 m 3 / h to maintain a nitrogen concentration of 99.999%), and sintered at 600 °C for 10 h to obtain the positive electrode material.

[0038] Example 3

[0039] This example provides a positive electrode material and a preparation method thereof, including the following steps:

[0040] (1) Take 5.0 kg of Ni 0.30 Fe 0.20 Mn 0.50 (OH)2 precursor, 2.0 kg of sodium carbonate, mix them in a high-speed mixer, send them into a box furnace, and introduce air into the furnace at a rate of 5 m 3 / h to maintain an oxygen-containing atmosphere, sinter at 900 °C for 15 h, and pulverize to obtain the cathode material matrix.

[0041] (2) Take 20 g of Na3Zr2Si2PO 12 Solid electrolyte powder is uniformly dispersed in 40 g of carbon nanotube slurry (carbon nanotube content 10 wt%), and stirred in a stirrer at a speed of 500 r / min for 1 h to obtain Na3Zr2Si2PO 12 Composite carbon nanotube-coated slurry.

[0042] (3) Take 1200 g of the cathode material matrix obtained in (1), put it into a high-speed mixer for stirring, and at the same time spray the coated slurry obtained in (2) into it. After all the slurry is sprayed and mixed evenly, send it into a box furnace. The box furnace is filled with a nitrogen atmosphere (introduce nitrogen at a rate of 5 m 3 / h to maintain a nitrogen concentration of 99.999%), sinter at 700 °C for 6 h to obtain the cathode material.

[0043] Example 4

[0044] This example provides a cathode material and its preparation method, including the following steps:

[0045] (1) Take 5.0 kg of Ni 0.30 Fe 0.30 Mn 0.40 (OH)2 precursor, 2.0 kg of sodium carbonate, mix them in a high-speed mixer, send them into a box furnace, and introduce air into the furnace at a rate of 5 m 3 / h to maintain an oxygen-containing atmosphere, sinter at 1000 °C for 12 h, and pulverize to obtain the cathode material matrix.

[0046] (2) Take 20 g of Na3Zr2Si2PO 12 Solid electrolyte powder is uniformly dispersed in 30 g of graphene oxide slurry (graphene oxide content 6 wt%), and stirred in a stirrer at a speed of 250 r / min for 1 h to obtain Na3Zr2Si2PO 12 Composite graphene oxide-coated slurry.

[0047] (3) Take 500 g of the positive electrode material matrix obtained in (1), put it into a high-speed mixer for stirring, and at the same time spray the coating slurry obtained in (2) into it. After all the spraying and mixing are uniform, send it into a box furnace. The box furnace is filled with a nitrogen-containing atmosphere (nitrogen is introduced at a rate of 5 m 3 / h to maintain a nitrogen concentration of 99.999%), sinter at 600 °C for 6 h to obtain the positive electrode material.

[0048] Comparative Example 1

[0049] This comparative example provides a positive electrode material and a preparation method thereof, including the following steps:

[0050] Take 5.0 kg of Ni 0.30 Fe 0.20 Mn 0.50 (OH)2 precursor and 2.0 kg of sodium carbonate, mix them in a high-speed mixer, send them into a box furnace, and introduce air into the furnace at a rate of 5 m 3 / h to maintain an oxygen-containing atmosphere, sinter at 1000 °C for 12 h, and pulverize to obtain the positive electrode material.

[0051] Comparative Example 2

[0052] This comparative example provides a positive electrode material and a preparation method thereof, including the following steps:

[0053] (1) Take 5.0 kg of Ni 0.30 Fe 0.20 Mn 0.50 (OH)2 precursor and 2.0 kg of sodium carbonate, mix them in a high-speed mixer, send them into a box furnace, and introduce air into the furnace at a rate of 5 m 3 / h to maintain an oxygen-containing atmosphere, sinter at 900 °C for 15 h, and pulverize to obtain the positive electrode material matrix.

[0054] (2) Take 24 g of Na3Zr2Si2PO 12 solid electrolyte powder and disperse it evenly in 36 g of water, stir it in a stirrer at a rotation speed of 500 r / min for 1 h to obtain Na3Zr2Si2PO 12 coating slurry.

[0055] (3) Take 1200 g of the positive electrode material matrix obtained in (1), put it into a high-speed mixer for stirring, and at the same time spray the coating slurry obtained in (2) into it. After all the spraying and mixing are uniform, send it into a box furnace. The box furnace is filled with a nitrogen-containing atmosphere (nitrogen is introduced at a rate of 5 m 3 / h to maintain a nitrogen concentration of 99.999%), sinter at 700 °C for 6 h to obtain the positive electrode material.

[0056] Comparative Example 3

[0057] This comparative example provides a cathode material and a preparation method thereof, including the following steps:

[0058] (1) Take 5.0 kg of Ni 0.30 Fe 0.20 Mn 0.50 (OH)2 precursor and 2.0 kg of sodium carbonate, mix them in a high-speed mixer, send them into a box furnace, and introduce air into the furnace at a rate of 5 m 3 / h to maintain an oxygen-containing atmosphere, sinter at 900 °C for 15 h, and pulverize to obtain the cathode material matrix.

[0059] (2) Take 20 g of carbon nanotubes and disperse them evenly in 40 g of carbon nanotube slurry (carbon nanotube content 10 wt%), stir at a speed of 500 r / min in a stirrer for 1 h to obtain carbon nanotube-coated slurry.

[0060] (3) Take 1200 g of the cathode material matrix obtained in (1), put it into a high-speed mixer and stir, and at the same time spray the coated slurry obtained in (2) into it. After all the spraying and mixing are uniform, send it into a box furnace. The box furnace is in a nitrogen-containing atmosphere (introduce nitrogen at a rate of 5 m 3 / h to maintain a nitrogen concentration of 99.999%), sinter at 700 °C for 6 h to obtain the cathode material.

[0061] Comparative Example 4

[0062] This comparative example provides a cathode material and a preparation method thereof, including the following steps:

[0063] (1) Take 5.0 kg of Ni 0.30 Fe 0.20 Mn 0.50 (OH)2 precursor and 2.0 kg of sodium carbonate, mix them in a high-speed mixer, send them into a box furnace, and introduce air into the furnace at a rate of 5 m 3 / h to maintain an oxygen-containing atmosphere, sinter at 900 °C for 15 h, and pulverize to obtain the cathode material matrix.

[0064] (2) Take 20 g of Na3V2(PO4)3 solid electrolyte powder and disperse it evenly in 40 g of carbon nanotube slurry (carbon nanotube content 10 wt%), stir at a speed of 500 r / min in a stirrer for 1 h to obtain Na3Zr2Si2PO 12 composite carbon nanotube-coated slurry.

[0065] (3) Take 1200 g of the cathode material matrix obtained in (1), put it into a high-speed mixer and stir, and at the same time spray the coated slurry obtained in (2) into it. After all the spraying and mixing are uniform, send it into a box furnace. The box furnace is in a nitrogen-containing atmosphere (introduce nitrogen at a rate of 5 m 3Nitrogen is introduced at a rate of / h to maintain a nitrogen concentration of 99.999%, and sintered at 700 °C for 6 h to obtain the cathode material.

[0066] Comparative Example 5

[0067] This comparative example provides a layered cathode material and its preparation method, including the following steps:

[0068] (1) Take 5.0 kg of Ni 0.33 Mn 0.67 (OH)2 precursor and 2.0 kg of sodium carbonate, mix them in a high-speed mixer, feed them into a box furnace, and introduce air into the furnace at a rate of 5 m 3 / h to maintain an oxygen-containing atmosphere, sinter at 1000 °C for 12 h, and pulverize to obtain the cathode material matrix.

[0069] (2) Take 20 g of Na3Zr2Si2PO 12 Solid electrolyte powder is uniformly dispersed in 30 g of graphene oxide slurry (graphene oxide content 6 wt%), and stirred in a stirrer at a speed of 250 r / min for 1 h to obtain Na3Zr2Si2PO 12 Composite graphene oxide-coated slurry.

[0070] (3) Take 500 g of the cathode material matrix obtained in (1), put it into a high-speed mixer and stir, while spraying the coated slurry obtained in (2) into it. After all the spraying and mixing are uniform, feed it into a box furnace. The atmosphere in the box furnace is a nitrogen-containing atmosphere (introduce nitrogen at a rate of 5 m 3 / h to maintain a nitrogen concentration of 99.999%), and sinter at 600 °C for 6 h to obtain the cathode material.

[0071] Test Example 1

[0072] Take the cathode materials obtained in the examples and test examples, and test their water content in 7 days under 30% air humidity according to GB / T 6283-2008. The test data are shown in Table 1.

[0073] Test Example 2

[0074] Take the cathode materials obtained in the examples and test examples, mix the cathode materials with conductive agent acetylene black and binder PVDF evenly according to the mass ratio of 80:12:8, add an appropriate amount of 1-methyl-2-pyrrolidone and ball mill for 2 h to obtain a slurry. Coat the slurry on an aluminum sheet, dry and press it into a cathode sheet. Use a sodium metal sheet as the anode, sodium hexafluorophosphate (NaPF6) as the electrolyte, and a mixture of dimethyl carbonate and ethylene carbonate with a volume ratio of 1:1 as the solvent to assemble a 2032 coin cell. Use a Siken test system to conduct electrical performance tests. In the range of charge-discharge cut-off voltages of 2.0 - 4.1 V, test the initial charge-discharge specific capacity at 0.1 C, and the charge-discharge ratio is the initial efficiency. Rate performance test: The charge-discharge cut-off voltage is 2.0 - 4.1 V, test the discharge capacity C1 under the condition of 1 C and the discharge capacity C2 under the condition of 0.1 C, and its rate performance is C1 / C2. Cycle retention rate test: At room temperature, test its 50-cycle capacity retention rate under the condition of charge-discharge at 1 C / 1 C. All the obtained data are shown in Table 1.

[0075] Table 1

[0076]

[0077] In Comparative Example 1, the cathode material matrix without any coating is directly used as the cathode material. In Comparative Example 2, only Na3Zr2Si2PO 12 , is coated. In Comparative Example 3, only carbon nanotubes are coated. In Comparative Example 4, the solid electrolyte powder Na3V2(PO4)3 is used to replace Na3Zr2Si2PO 12 equally. In Comparative Example 5, a nickel-manganese cathode material matrix is used. It can be seen from Table 1 that compared with the examples, the charge-discharge specific capacity and initial efficiency of Comparative Examples 1 - 4 decrease slightly, the water content increases significantly, and the rate performance and cycle retention rate decrease significantly; although Comparative Example 5 has a low water content, excellent initial efficiency and cycle retention rate, due to the use of a nickel-manganese cathode material matrix instead of a nickel-iron-manganese cathode material matrix, the specific capacity is significantly lower. Therefore, the cathode material provided in this application can have good air stability, good processing stability, high energy density, and good cycle stability and rate performance through the cooperation of a specific cathode material matrix and coating material.

[0078] Obviously, the above examples are only for clear illustration and not for limitation of the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A cathode material, characterized in that, It includes a cathode material matrix and a coating layer covering at least part of the surface of the cathode material matrix; The coating layer includes Na3Zr2Si2PO 12 and carbon; The cathode material matrix includes a nickel-iron-manganese cathode material matrix.

2. The cathode material according to claim 1, characterized in that, In the coating layer, the mass ratio of Na3Zr2Si2PO 12 to carbon is 100:5 to 20; And / or, the mass ratio of the cathode material matrix to the coating layer is 100:2 to 5.

3. The cathode material according to claim 1 or 2, characterized in that, The general formula of the positive electrode material matrix is Na m Ni x Fe y Mn z O2, where x + y + z = 1, 0.2 ≤ x ≤ 0.3, 0.2 ≤ y ≤ 0.3, 0.4 ≤ z ≤ 0.6, 0.67 ≤ m ≤ 0.

71.

4. A method for preparing a cathode material according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1: Mix Na3Zr2Si2PO 12 , a carbon source, and water to obtain a coating slurry; S2: Mix the cathode material matrix and the coating slurry, and sinter to obtain the cathode material.

5. The preparation method according to claim 4, characterized in that, In the coating slurry, the mass ratio of Na3Zr2Si2PO 12 to the carbon source is 100:5 to 20; And / or, in the coating slurry, the solid content is 40% to 50%; And / or, the carbon source includes at least one of graphene oxide, graphene, carbon nanotubes, and carbon fibers.

6. The preparation method according to claim 4 or 5, characterized in that, In the S2, the mass ratio of the cathode material matrix to the coating slurry is 100:5 to 10.

7. The preparation method according to any one of claims 4 to 6, characterized in that, In the S2, the sintering is carried out in a protective atmosphere, the temperature is 600 to 700 °C, and the time is 6 to 10 h; optionally, the protective atmosphere includes a noble gas atmosphere and / or a nitrogen atmosphere; and / or, in the S1, the way of mixing Na3Zr2Si2PO 12 , a carbon source and water includes stirring; optionally, the stirring speed is 200 to 500 r / min and the time is 1 to 5 h.

8. The preparation method according to any one of claims 4 to 7, characterized in that, The steps of preparing the cathode material matrix include mixing a nickel-iron-manganese precursor and a sodium source, sintering, and pulverizing to obtain the cathode material matrix; optionally, in the steps of preparing the cathode material matrix, the sintering is carried out in an oxygen-containing atmosphere, the temperature is 900 to 1000 °C, and the time is 10 to 15 h.

9. The preparation method according to claim 8, characterized in that, The sodium source includes soluble sodium salts; optionally, the sodium source includes at least one of sodium carbonate and sodium bicarbonate.

10. Application of the cathode material according to any one of claims 1 to 3 or the cathode material prepared by the preparation method according to any one of claims 4 to 9 in a secondary battery; optionally, the secondary battery includes a sodium-ion battery.

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