A composite positive electrode material and its preparation method and application

Abstract

The present invention relates to the field of battery material technology, and more particularly to a composite positive electrode material, a preparation method thereof, and an application thereof. The composite positive electrode material is a core-shell structure, comprising a core and a coating layer coated on the surface of the core; wherein the chemical formula of the positive electrode active material is Na x‑a Li a Ni 1‑b‑c M b RE c O 2‑d F d The coating layer material includes Na3PO4 and Na3PS4. The sodium ion battery prepared using the composite cathode material of the present invention not only has high energy density but also excellent long-cycle stability, effectively making up for the shortcomings of existing technologies and providing a new design idea for the development of sodium ion batteries.

Description

Technical Field

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

[0002] With the rapid development of the global economy, energy demand has increased year by year. Traditional fossil energy can no longer meet the growing energy demand. The development and utilization of new energy has become the key to solving the energy crisis. Sodium-ion batteries, as a new energy storage technology, have the advantages of rich raw material resources, high charge and discharge rate, long cycle life, high safety, green environmental protection and recyclability. They have huge application potential in many fields.

[0003] Sodium-ion battery cathode materials, with their high theoretical specific capacity and operating voltage, are among the most promising cathode materials currently available. However, their practical application still faces numerous challenges. Existing layered oxide cathode materials are prone to structural collapse during charge and discharge due to the intercalation and deintercalation of sodium ions, reducing energy density and leading to capacity decay. Polyanion compound cathode materials are prone to decomposition at high temperatures, affecting the cycling performance of sodium-ion batteries. Prussian blue compound cathode materials are prone to phase transitions during cycling, affecting material stability.

[0004] Based on this, developing a sodium ion battery positive electrode material with stable structure, high energy density and good cycle stability is of great practical significance for the development of sodium ion batteries. Summary of the Invention

[0005] In response to the problem that existing sodium ion battery positive electrode materials have poor structural stability, which easily leads to a decrease in the energy density of sodium ion batteries and a deterioration in cycle performance, the present invention provides a composite positive electrode material and its preparation method and application. The composite positive electrode material is a core-shell structure, including a positive electrode active material and a coating layer coated on the surface of the positive electrode active material. The sodium ion battery prepared using the composite positive electrode material of the present invention can maintain structural stability during the charge and discharge cycle, ensuring that the sodium ion battery has a high energy density and long cycle stability, and provides a new design idea for the development of sodium ion battery positive electrode materials.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A first aspect of the present invention provides a composite positive electrode material, wherein the composite positive electrode material is a core-shell structure, comprising a positive electrode active material and a coating layer coated on the surface of the positive electrode active material;

[0008] Wherein, the chemical formula of the positive electrode active material is Na x-a Li a Ni 1-b-c Mb RE c O 2-d F d , wherein M is any one of Mn, Fe, Zn, Zr, Nb, Mo, Cu or Ti; RE is any one of La, Eu or Dy; 0.8≤x≤1, 0<a≤0.2, 0<b≤0.3, 0<c≤0.2, 0<d≤1;

[0009] The materials of the coating layer include Na3PO4 and Na3PS4.

[0010] The present invention designs a composite positive electrode material with a core-shell structure, which uses a positive electrode active material with a high specific capacity as the core and a coating material that can improve the cycle stability of the battery material as the shell, which can not only improve the higher energy density, but also maintain a good capacity retention rate after multiple charge and discharge cycles. The positive electrode active material is a doped multi-element layered metal oxide. The doping elements effectively improve the structural stability of the positive electrode material by occupying specific lattice sites, reduce structural changes and phase changes during the charge and discharge process, and thus improve the cycle life of the sodium ion battery. In particular, the incorporation of rare earth elements plays the role of a supporting structure and inhibits the occurrence of phase change. In addition, since the insertion and removal of sodium ions will cause the volume change of the material, which may cause the pulverization and structural collapse of the material, rare earth elements can act as a buffer to absorb and disperse the stress generated by the volume change, thereby reducing the risk of structural collapse of the positive electrode material.

[0011] The coating layer material acts as a physical barrier, effectively preventing side reactions between the electrode material and the electrolyte, reducing the risk of structural damage to the positive electrode active material, maintaining the structural integrity of the positive electrode active material, and thereby improving the cycle stability of the positive electrode material. The composite positive electrode material provided by the present invention has excellent structural stability, and the sodium ion battery prepared using it has high energy density and long cycle stability, solving the problem of poor structural stability of existing sodium ion battery positive electrode materials, which easily leads to reduced energy density and poor cycle performance of sodium ion batteries.

[0012] Preferably, the mass ratio of Na3PO4 to Na3PS4 in the coating layer is 1:0.8-1:1.2.

[0013] Preferably, the coating layer has a thickness of 2 nm to 10 nm.

[0014] More preferably, the coating layer has a thickness of 5 nm to 10 nm.

[0015] The preferred coating layer can not only inhibit the side reaction between the positive electrode active material and the electrolyte, but also reduce the dissolution and structural damage of the positive electrode active material, thereby improving the capacity retention rate and cycle stability of the battery.

[0016] Preferably, the positive electrode active material is Na 0.8 Li 0.1 Ni 0.7 Mn 0.2 La 0.1 O 1.4 F 0.6 、Na 0.7 Li 0.2 Ni 0.55 Zn 0.35 Eu 0.1 OF、Na 0.75 Li 0.25 Ni 0.6 Zr 0.2 Dy 0.1 O 1.3 F 0.7 、Na 0.75 Li 0.05 Ni 0.55 Fe 0.3 La 0.1 5O 1.25 F 0.75 Or Na 0.7 Li 0.1 Ni 0.5 Cu 0.3 Eu 0.2 O 1.2 F 0.8 .

[0017] Preferably, the preparation method of the positive electrode active material comprises the following steps:

[0018] According to the designed ratio, the sodium source, lithium source, nickel source, M source, RE source and fluorine source are uniformly mixed to obtain a mixed inorganic material; the mixed inorganic material is wet ball-milled, heated to 700° C.-1200° C., calcined, and ground to obtain the positive electrode active material.

[0019] Further preferably, the solvent for the wet ball milling is anhydrous ethanol; and the mass volume ratio of the mixed inorganic material to the solvent is 1 g:4 mL-1 g:8 mL.

[0020] Preferably, the diameter of the wet ball milling beads is 100 μm-500 μm; the ball-to-material ratio is 5:1-10:1; the rotation speed is 600 rpm-900 rpm; and the ball milling time is 1 h-3 h.

[0021] Preferably, the calcination time is 10h-15h.

[0022] Preferably, the temperature is raised to 700° C.-1200° C. in a programmed temperature rising manner, with a heating rate of 3° C. / min-8° C. / min.

[0023] Preferably, the sodium source is sodium fluoride or sodium carbonate.

[0024] Preferably, the lithium source is lithium carbonate or lithium fluoride.

[0025] Preferably, the nickel source is nickel carbonate or nickel oxide.

[0026] Preferably, the M source is any one of manganese carbonate, manganese dioxide, iron carbonate, iron oxide, zinc carbonate, zinc oxide, zirconium carbonate, zirconium oxide, niobium carbonate, niobium oxide, molybdenum carbonate, molybdenum oxide, copper carbonate, copper oxide or titanium dioxide.

[0027] Preferably, the RE source is any one of lanthanum oxide, europium oxide or dysprosium oxide.

[0028] Preferably, the fluorine source is sodium fluoride or lithium fluoride.

[0029] The second aspect of the present invention provides a method for preparing the composite positive electrode material, comprising the following steps: weighing the positive electrode active material, Na3PO4 and Na3PS4 according to the designed ratio, mixing them evenly, fusing and coating them to obtain a coating material; in an inert atmosphere, heating the coating material to 300°C-500°C for sintering, and cooling to obtain a composite positive electrode material.

[0030] Preferably, the specific steps of the fusion coating are: coating the mixture at 400°C-500°C and 300rpm-800rpm for 50min-80min; and then coating at 300°C-400°C and 200rpm-500rpm for 4h-6h.

[0031] The present invention utilizes a fusion coating method to coat the positive electrode active material, thereby enabling the coating layer material and the positive electrode active material to construct a more efficient sodium ion transmission channel, effectively enhancing the conductivity and stability of the composite positive electrode material, thereby improving the cycle stability of the sodium ion battery.

[0032] Preferably, the temperature is raised to 300° C.-500° C. in a programmed temperature rising manner, with a heating rate of 3° C. / min-5° C. / min.

[0033] Preferably, the sintering time is 4h-6h.

[0034] Preferably, the cooling is performed by programmed cooling, with a cooling rate of 5°C / min-10°C / min.

[0035] The third aspect of the present invention provides an application of the composite positive electrode material or the composite positive electrode material prepared by the method for preparing the composite positive electrode material in the preparation of a sodium ion battery.

[0036] In summary, the present invention provides a composite positive electrode material with a core-shell structure, comprising a positive electrode active material and a coating layer coated on the surface of the positive electrode active material. A sodium ion battery prepared using the composite positive electrode material of the present invention can maintain structural stability during the charge and discharge cycle, ensuring that the sodium ion battery has a high energy density and long-cycle stability. Testing has shown that the sodium ion battery prepared using the composite positive electrode material provided by the present invention still has a capacity retention rate of 84.1% after 500 cycles, providing a new design idea for the development of sodium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The following are scanning electron microscope images of the composite positive electrode materials described in each embodiment. DETAILED DESCRIPTION

[0038] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment provides a composite positive electrode material, which specifically includes the following contents:

[0041] The composite positive electrode material is a core-shell structure, comprising a positive electrode active material and a coating layer with a thickness of 7 nm coated on the surface of the positive electrode active material;

[0042] Wherein, the chemical formula of the positive electrode active material is Na 0.8 Li 0.1 Ni 0.7 Mn 0.2 La 0.1 O 1.4 F 0.6 ; The coating layer material is Na3PO4 and Na3PS4 in a mass ratio of 1:1.

[0043] The preparation method of the composite positive electrode material is as follows:

[0044] Step 1. According to the designed ratio, 0.5345g of sodium carbonate, 0.1850g of lithium carbonate, 2.6141g of nickel oxide, 0.8651g of manganese dioxide, 0.8154g of lanthanum oxide and 1.2852g of sodium fluoride were mixed to obtain a mixed inorganic material; the mixed inorganic material was put into a planetary ball mill, 30mL of anhydrous ethanol was added, and ball milling beads with a diameter of 250μm were used. The mixed inorganic material was wet-milled at a ball-to-material ratio of 8:1 and a speed of 800rpm for 2h, and dried at 90°C for 20min. The dried mixed inorganic material was sent to a muffle furnace and heated to 850°C at a heating rate of 5°C / min for calcination for 12h, and ground to obtain the positive electrode active material.

[0045] Step 2: Evenly mix 5 g of the positive electrode active material, 0.1752 g of Na3PO4 and 0.1752 g of Na3PS4, and perform fusion coating. First, coat the mixture at 450 ° C and 600 rpm for 60 minutes; then coat it at 350 ° C and 400 rpm for 5 hours to obtain a coated material; in an inert atmosphere, heat the coated material to 450 ° C at a heating rate of 4 ° C / min and sinter for 5 hours. After sintering, cool it to room temperature at a cooling rate of 6 ° C / min to obtain a composite positive electrode material.

[0046] Example 2

[0047] This embodiment provides a composite positive electrode material, which specifically includes the following contents:

[0048] The composite positive electrode material is a core-shell structure, comprising a positive electrode active material and a coating layer with a thickness of 5 nm coated on the surface of the positive electrode active material;

[0049] Wherein, the chemical formula of the positive electrode active material is Na 0.7 Li 0.2 Ni 0.55 Zn 0.35 Eu 0.1 OF; the coating layer material is Na3PO4 and Na3PS4 in a mass ratio of 1:0.9.

[0050] The preparation method of the composite positive electrode material is as follows:

[0051] Step 1. According to the designed ratio, 0.3695g of lithium carbonate, 2.0540g of nickel oxide, 1.4243g of zinc oxide, 0.8795g of europium oxide and 2.0995g of sodium fluoride were mixed uniformly to obtain a mixed inorganic material; the mixed inorganic material was put into a planetary ball mill, 35mL of anhydrous ethanol was added, and ball milling beads with a diameter of 300μm were used. The mixed inorganic material was wet-milled for 2h at a ball-to-material ratio of 10:1 and a speed of 800rpm, and dried at 90°C for 20min. The dried mixed inorganic material was sent to a muffle furnace and heated to 900°C at a heating rate of 5°C / min for calcination for 11h, and ground to obtain the positive electrode active material.

[0052] Step 2: Evenly mix 5 g of the positive electrode active material, 0.1651 g of Na3PO4 and 0.1352 g of Na3PS4, and perform fusion coating. First, coat the mixture at 420°C and 750 rpm for 80 min; then coat it at 360°C and 400 rpm for 6 h to obtain a coated material; in an inert atmosphere, heat the coated material to 400°C at a heating rate of 5°C / min and sinter for 5 h. After sintering, cool it to room temperature at a cooling rate of 5°C / min to obtain a composite positive electrode material.

[0053] Example 3

[0054] This embodiment provides a composite positive electrode material, which specifically includes the following contents:

[0055] The composite positive electrode material is a core-shell structure, comprising a positive electrode active material and a coating layer with a thickness of 7 nm coated on the surface of the positive electrode active material;

[0056] Wherein, the chemical formula of the positive electrode active material is Na 0.75 Li 0.25 Ni 0.6 Zr 0.2 Dy 0.1 O 1.3 F 0.7 ; The coating layer material is Na3PO4 and Na3PS4 in a mass ratio of 1:1.1.

[0057] The preparation method of the composite positive electrode material is as follows:

[0058] Step 1. According to the designed ratio, 0.1325g of sodium carbonate, 0.4618g of lithium carbonate, 2.2407g of nickel oxide, 1.2322g of zirconium oxide, 0.9325g of dysprosium oxide and 1.4697g of sodium fluoride were mixed to obtain a mixed inorganic material; the mixed inorganic material was put into a planetary ball mill, 28mL of anhydrous ethanol was added, and ball milling beads with a diameter of 400μm were used. The mixed inorganic material was wet-milled for 2h at a ball-to-material ratio of 6:1 and a speed of 800rpm, and dried at 90°C for 20min. The dried mixed inorganic material was sent to a muffle furnace and heated to 1150°C at a heating rate of 5°C / min for calcination for 11h, and ground to obtain the positive electrode active material.

[0059] Step 2: Evenly mix 5 g of the positive electrode active material, 0.1547 g of Na3PO4 and 0.1702 g of Na3PS4, and perform fusion coating. First, coat the mixture at 400°C and 800 rpm for 75 min; then coat it at 400°C and 300 rpm for 6 h to obtain a coated material; in an inert atmosphere, heat the coated material to 390°C at a heating rate of 3°C / min and sinter for 5 h. After sintering, cool it to room temperature at a cooling rate of 10°C / min to obtain a composite positive electrode material.

[0060] Example 4

[0061] This embodiment provides a composite positive electrode material, which specifically includes the following contents:

[0062] The composite positive electrode material is a core-shell structure, comprising a positive electrode active material and a coating layer with a thickness of 8 nm coated on the surface of the positive electrode active material;

[0063] Wherein, the chemical formula of the positive electrode active material is Na 0.75 Li 0.05 Ni 0.55 Fe 0.3 La 0.15 O 1.25 F 0.75 ; The coating layer material is Na3PO4 and Na3PS4 in a mass ratio of 1:1.

[0064] The preparation method of the composite positive electrode material is as follows:

[0065] Step 1. According to the designed ratio, 0.0923g of lithium carbonate, 2.0539g of nickel oxide, 1.1977g of iron oxide, 1.2218g of lanthanum oxide and 1.5746g of sodium fluoride were mixed to obtain a mixed inorganic material; the mixed inorganic material was put into a planetary ball mill, 30mL of anhydrous ethanol was added, and ball milling beads with a diameter of 250μm were used. The mixed inorganic material was wet-milled at a ball-to-material ratio of 8:1 and a speed of 800rpm for 2h, and dried at 90°C for 20min. The dried mixed inorganic material was sent to a muffle furnace and heated to 1050°C at a heating rate of 6°C / min for calcination for 12h, and ground to obtain the positive electrode active material.

[0066] Step 2: Evenly mix 5 g of the positive electrode active material, 0.1841 g of Na3PO4 and 0.1841 g of Na3PS4, and perform fusion coating. First, coat the mixture at 480°C and 500 rpm for 60 min; then coat it at 360°C and 500 rpm for 5 h to obtain a coated material; in an inert atmosphere, heat the coated material to 500°C at a heating rate of 4°C / min and sinter for 5 h. After sintering, cool it to room temperature at a cooling rate of 6°C / min to obtain a composite positive electrode material.

[0067] Example 5

[0068] This embodiment provides a composite positive electrode material, which specifically includes the following contents:

[0069] The composite positive electrode material is a core-shell structure, comprising a positive electrode active material and a coating layer with a thickness of 10 nm coated on the surface of the positive electrode active material;

[0070] Wherein, the chemical formula of the positive electrode active material is Na 0.7 Li 0.1 Ni 0.5 Cu 0.3 Eu 0.2 O 1.2 F 0.8 ; The coating layer material is Na3PO4 and Na3PS4 in a mass ratio of 1:1.2.

[0071] The preparation method of the composite positive electrode material is as follows:

[0072] Step 1. According to the designed ratio, 0.2649 g of sodium carbonate, 0.1847 g of lithium carbonate, 1.8673 g of nickel oxide, 1.2151 g of copper oxide, 0.8798 g of europium oxide and 1.6796 g of sodium fluoride were mixed to obtain a mixed inorganic material; the mixed inorganic material was put into a planetary ball mill, 30 mL of anhydrous ethanol was added, and ball milling beads with a diameter of 500 μm were used. The mixed inorganic material was wet-milled for 2 h at a ball-to-material ratio of 5:1 and a speed of 900 rpm, and dried at 90 ° C for 20 min. The dried mixed inorganic material was sent to a muffle furnace and heated to 920 ° C at a heating rate of 4 ° C / min for calcination for 12 h, and ground to obtain the positive electrode active material.

[0073] Step 2: Evenly mix 5 g of the positive electrode active material, 0.1931 g of Na3PO4 and 0.2318 g of Na3PS4, and perform fusion coating. First, coat the mixture at 450 ° C and 400 rpm for 60 minutes; then coat it at 330 ° C and 500 rpm for 5 hours to obtain a coated material; in an inert atmosphere, heat the coated material to 420 ° C at a heating rate of 4 ° C / min and sinter for 6 hours. After sintering, cool it to room temperature at a cooling rate of 10 ° C / min to obtain a composite positive electrode material.

[0074] Comparative Example 1

[0075] This comparative example provides a composite positive electrode material, which differs from Example 1 in that the lanthanum oxide in the positive electrode active material is replaced by an equal molar amount of erbium oxide, and the other components and parameters remain unchanged and are not described again here.

[0076] Comparative Example 2

[0077] This comparative example provides a composite positive electrode material, which differs from Example 1 in that manganese dioxide in the positive electrode active material is replaced by an equimolar amount of cobalt oxide, and other components and parameters remain unchanged and are not described again here.

[0078] Comparative Example 3

[0079] This comparative example provides a composite positive electrode material, which differs from Example 1 in that the lanthanum oxide in the positive electrode active material is replaced by an equimolar amount of zinc oxide, and the other components and parameters remain unchanged and are not described again here.

[0080] Comparative Example 4

[0081] This comparative example provides a composite positive electrode material, which differs from Example 1 in that the lithium carbonate in the positive electrode active material is replaced by an equimolar amount of potassium carbonate, and the other components and parameters remain unchanged and are not described again here.

[0082] Comparative Example 5

[0083] This comparative example provides a composite positive electrode material, which differs from Example 1 in that rare earth elements are omitted from the positive electrode active material, and its chemical formula is Na 0.8 Li 0.1 Ni 0.8 Mn 0.2 O 1.3 F 0.7 , other components and parameters remain unchanged and will not be described here.

[0084] Comparative Example 6

[0085] This comparative example provides a composite positive electrode material, which differs from Example 1 in that the coating layer material is replaced with an equal amount of Na3PO4, and other components and parameters remain unchanged, which will not be described here.

[0086] Comparative Example 7

[0087] This comparative example provides a composite positive electrode material, which differs from Example 1 in that the coating layer material is replaced with an equal amount of Na3PS4, and the other components and parameters remain unchanged and will not be described again here.

[0088] In order to further demonstrate the technical effects of the present invention, the present invention conducted application performance tests on the composite positive electrode materials obtained in Examples 1-5 and Comparative Examples 1-7, and prepared each composite positive electrode material into a sodium ion battery. The specific production steps are as shown in the test examples.

[0089] Test example

[0090] The composite positive electrode material, conductive carbon black and polyvinylidene fluoride are evenly mixed in a mass ratio of 90:5:5, coated on aluminum foil to make a positive electrode sheet, a sodium sheet is used as a negative electrode sheet, polypropylene is used as a separator, NaClO4 is used as an electrolyte salt, ethylene carbonate, propylene carbonate and fluoroethylene carbonate are used as electrolyte solvents, the electrolyte concentration is 1 mol / L, and a button test battery is assembled under an inert atmosphere.

[0091] The present invention conducted electrical performance testing on the button-type batteries obtained in the experimental examples, with charge and discharge voltages ranging from 2.0V to 4.3V. The initial charge and discharge test was conducted at a rate of 0.1C, followed by 200 and 500 cycles of charge and discharge at a rate of 0.5C. Capacity retention is expressed in mAh / g, with the ratio of the battery's capacity at the 200th and 500th cycles to the initial capacity. The test results are shown in Table 1.

[0092] Table 1 Electrochemical performance test results of button batteries prepared using the composite positive electrode materials obtained in various examples and comparative examples

[0093]

[0094] As can be seen from Table 1, the sodium ion batteries prepared using the composite positive electrode materials obtained in Examples 1-5 have excellent performance, especially Example 1, whose first cycle 0.1C discharge specific capacity is as high as 175.5 mAh / g; after 200 cycles, the 0.5C discharge specific capacity is as high as 154.8 mAh / g, and the capacity retention rate is as high as 88.2%; after 500 cycles, the 0.5C discharge specific capacity is as high as 147.6 mAh / g, and the capacity retention rate is as high as 84.1%.

[0095] according to Figure 1 It can be seen that the composite cathode material provided by the present invention is a core-shell structure, wherein the coating layer is a mixture of Na3PO4 and Na3PS4, and the core is Na x-a Li a Ni 1-b-c M b RE c O 2-d F d Positive electrode active material; the composite positive electrode material has high energy density and excellent cycle stability, effectively making up for the shortcomings of the existing technology.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements 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 composite positive electrode material, characterized in that The composite positive electrode material is a core-shell structure, comprising a positive electrode active material and a coating layer coated on the surface of the positive electrode active material; Wherein, the chemical formula of the positive electrode active material is Na x-a Li a Ni 1-b-c M b RE c O 2-d F d , wherein M is any one of Mn, Fe, Zn, Zr, Nb, Mo, Cu or Ti; RE is any one of La, Eu or Dy; 0.8≤x≤1, 0<a≤0.2, 0<b≤0.3, 0<c≤0.2, 0<d≤1; The materials of the coating layer include Na3PO4 and Na3PS4.

2. The composite cathode material according to claim 1, wherein The mass ratio of Na3PO4 to Na3PS4 in the coating layer is 1:0.8-1:1.2; and / or The coating layer has a thickness of 2 nm to 10 nm.

3. The composite cathode material according to claim 1, wherein Stated positive active substance properties Na 0.8 Li 0.1 Ni 0. 7Mn 0.2 La 0.1 O 1.4 F 0.6 , Na 0.7 Li 0.2 Ni 0.55 Zn 0.35 EU 0.1 OF, Na 0.75 Li 0.25 Ni 0.6 Zr 0.2 Dy 0.1 O 1.3 F 0.7 , Na 0.75 Li 0.05 Ni 0.55 Fe 0.3 La 0.15 O 1.25 F 0.75 OrNa 0.7 Li 0.1 Ni 0.5 Cu 0.3 EU 0.2 O 1.2 F 0.8 .

4. The composite cathode material according to claim 1 or 3, wherein: The preparation method of the positive electrode active material comprises the following steps: According to the designed ratio, the sodium source, lithium source, nickel source, M source, RE source and fluorine source are uniformly mixed to obtain a mixed inorganic material; the mixed inorganic material is wet ball-milled, heated to 700° C.-1200° C., calcined, and ground to obtain the positive electrode active material.

5. The composite cathode material according to claim 4, wherein The solvent of the wet ball milling is anhydrous ethanol; the mass volume ratio of the mixed inorganic material to the solvent is 1g:2mL-1g:4mL; and / or The diameter of the ball milling beads in the wet ball milling is 100 μm-500 μm; the ball-to-material ratio is 5:1-10:1; the rotation speed is 600 rpm-900 rpm; and the ball milling time is 1 h-3 h.

6. The composite cathode material according to claim 4, wherein The calcination time is 10h-15h; and / or The temperature is raised to 700°C-1200°C by a programmed temperature increase method, with a heating rate of 3°C / min-8°C / min.

7. A method for preparing a composite positive electrode material according to any one of claims 1 to 6, characterized in that: The steps include: The positive electrode active material, Na3PO4 and Na3PS4 are weighed according to the designed ratio, mixed evenly, and fused and coated to obtain a coating material; under an inert atmosphere, the coating material is heated to 300°C-500°C for sintering, and cooled to obtain a composite positive electrode material.

8. The method for preparing a composite positive electrode material according to claim 7, wherein: The specific steps of the fusion coating are: coating the mixture at 400-500°C and 300-800 rpm for 50-80 minutes; and then coating at 300-400°C and 200-500 rpm for 4-6 hours.

9. The method for preparing a composite positive electrode material according to claim 7, wherein: Raise the temperature to 300°C-500°C by programmed temperature increase at a rate of 3°C / min-5°C / min; and / or The sintering time is 4h-6h; and / or The cooling is carried out by programmed cooling at a cooling rate of 5°C / min-10°C / min.

10. Use of the composite cathode material according to any one of claims 1 to 6 or the composite cathode material prepared by the method for preparing the composite cathode material according to any one of claims 7 to 9 in preparing a sodium ion battery.

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