A positive electrode material, a preparation method and application thereof

Abstract

The application relates to the field of batteries, and discloses a positive electrode material and a preparation method and application thereof. 2+ The application relates to the field of batteries, and discloses a positive electrode material and a preparation method and application thereof. The core part comprises carbon-coated Cu The shell layer is CuO; the iron-based phosphate sodium ion material is selected from sodium iron pyrophosphate, sodium iron phosphate or sodium phosphate pyrophosphate. The preparation method of the positive electrode material comprises the following steps: mixing carbon-coated iron-based phosphate sodium ion material, a copper source and a first solvent, and then performing first drying and first calcination. The positive electrode material has good electrochemical performance, the battery prepared by using the positive electrode material has good cycle performance and high rate performance, the application prospect in the field of batteries is good, and the preparation method is simple and efficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] With the continuous expansion of global large-scale energy storage demand, the shortage of lithium resources on earth will become a bottleneck restricting the future large-scale application of lithium-ion batteries. Sodium element and lithium element are in the same main group, their chemical properties are similar to lithium element, and the crust abundance of sodium element is 2.64%, which is much higher than that of lithium element (0.006%), so it is of great significance and practical value to develop resource-rich and environmentally friendly sodium-ion battery technology for the development of large-scale energy storage technology.

[0003] There are still many technical problems to be overcome in the field of sodium-ion batteries, and the technical difficulty that needs to be broken through in particular is to develop a low-cost and high-performance positive electrode material. Although great progress has been made in the positive electrode material of ion battery in recent years. However, the lack of low-cost and long-life positive electrode material is still a major obstacle to the commercial application of sodium-ion batteries. Researchers have studied many positive electrode materials for sodium-ion batteries, such as transition metal oxides, polyanion compounds and prussian blue analogues. Among them, sodium iron pyrophosphate phosphate is one of the most promising sodium-ion battery positive electrode materials for industrialization, and the material with NASICON structure has attracted attention due to its three-dimensional ion transmission tunnel, high working potential and stable structure, low cost and good cycle life. Advantages such as, mainly phosphate, pyrophosphate, mixed polyanion type, such as Na3V2(PO4)3, Na3V2(PO4)2F3, Na2FeP2O7, Na2MnP2O7, Na2CoP2O7, Na7V3(P2O7)4, Na7V4(P2O7)4(PO4), Na4Fe3(PO4)2(P2O7) and the like. However, the electronic conductivity of the iron-based phosphate positive electrode material is poor, the ion diffusion rate is slow, the structure is difficult to control after high-temperature sintering, and it is sensitive to H2O and CO2. The sensitivity of the positive electrode material to H2O and CO2 will cause the surface of the material to be oxidized to generate sodium carbonate and other substances, resulting in the destruction of the structure of the electrode material, thereby causing problems such as electrolyte corrosion, and ultimately resulting in the material having a high initial irreversible capacity. SUMMARY

[0004] The purpose of the present application is to overcome the problems of poor electronic conductivity, slow ion diffusion rate and sensitivity to H2O and CO2 of the existing iron-based phosphate positive electrode material in the prior art, to provide a positive electrode material which can inhibit the sensitivity to H2O and CO2 and has a fast Na + diffusion rate, good electrochemical performance of the material, and a simple and efficient preparation method.

[0005] To achieve the above object, the present application provides a positive electrode material in one aspect, the positive electrode material is a core-shell structure, the core part comprises carbon-coated Cu 2+ The doped iron-based phosphate sodium ion material, and the shell layer is CuO.

[0006] The iron-based phosphate sodium ion material is selected from at least one of sodium iron pyrophosphate, sodium iron phosphate and sodium iron phosphate pyrophosphate.

[0007] Preferably, the content of carbon in the positive electrode material is 1-8wt%, and the content of CuO in the positive electrode material is 0.5-2.5wt% based on the total weight of the positive electrode material.

[0008] The second aspect of the present application provides a method for preparing a positive electrode material, which comprises mixing carbon-coated iron-based phosphate sodium ion material, copper source and first solvent, then first drying and first calcination.

[0009] Preferably, the preparation method of the carbon-coated iron-based phosphate sodium ion material comprises mixing sodium source, iron source, phosphorus source, carbon source and second solvent, then reacting, and then second drying and second calcination.

[0010] Preferably, the molar ratio of sodium in sodium source, iron in iron source, phosphorus in phosphorus source and carbon in carbon source is 1:0.6-0.79:1-1.29:0.5-1.

[0011] Preferably, the method at least meets one of the following conditions:

[0012] The temperature of the reaction is 80-100℃, and the time is 0.5-8h;

[0013] The conditions of the second drying include: temperature is 90-115℃, time is 0.5-8h;

[0014] The conditions of the second calcination include: temperature is 450-600℃, time is 8-15h.

[0015] Preferably, the weight ratio of carbon-coated iron-based phosphate sodium ion material and copper in copper source is 100:0.5-2.

[0016] Preferably, the method at least meets one of the following conditions:

[0017] The conditions of the first drying include: temperature is 80-100℃, time is 0.5-8h;

[0018] The conditions of the first calcination include: temperature is 450-600℃, time is 2-10h.

[0019] The third aspect of the present application provides the positive electrode material prepared by the above method.

[0020] The fourth aspect of the present application provides a battery slurry, the battery slurry comprising the positive electrode material and a third solvent, the positive electrode material being the above positive electrode material.

[0021] The fifth aspect of the present application provides a positive electrode sheet, the positive electrode sheet comprising a current collector and a battery slurry disposed on the current collector, the battery slurry being the above battery slurry.

[0022] The sixth aspect of the present application provides a battery, the battery comprising the positive electrode sheet, the positive electrode sheet being the above positive electrode sheet.

[0023] The seventh aspect of the present application provides an electric device, the electric device comprising the battery, the battery being the above battery.

[0024] Compared with the prior art, the technical scheme of the present application has the following advantages:

[0025] (1) The positive electrode material has excellent electrochemical performance, excellent cycle performance and high rate performance, which may be due to the fact that the CuO coating can inhibit the sensitivity of the positive electrode material to H2O and CO2, reduce the generation of sodium carbonate on the surface of the material, thereby avoiding the interface reaction between the electrode material and the electrolyte, and secondly, the Cu 2+ doped occupying material Fe 2 + dissolved vacancies, since the ionic radius of Cu 2+ (0.073 nm) is larger than that of Fe 2+ (0.061 nm), the unit cell volume of the positive electrode material can be increased, thereby improving the diffusion rate of Na + and ultimately improving the electrochemical performance of the material;

[0026] (2) The preparation method has simple and efficient synthesis process. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the XRD pattern of the positive electrode material prepared in Examples 1-3 and Comparative Example 1;

[0028] Figure 2 is the XRD zoomed-in pattern of the positive electrode material prepared in Examples 1-3 and Comparative Example 1;

[0029] Figure 3 is the TG curve of the positive electrode material prepared in Examples 1-3 and Comparative Example 1;

[0030] Figure 4 is the electron microscope image of the positive electrode material prepared in Examples 1-3 and Comparative Example 1;

[0031] Figure 5 is the EDS graph of the positive electrode material prepared in Example 1-3;

[0032] Figure 6 1 is the charge and discharge curve of the battery prepared with the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 at 0.1C;

[0033] Figure 7 1C cycle performance diagram of batteries prepared with the positive electrode materials prepared in Examples 1-3 and Comparative Example 1;

[0034] Figure 8 It is a test graph of the discharge specific capacity of batteries prepared with the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 at rates of 0.1C, 0.2C, 0.5C, 1C, 2C and 5C. DETAILED DESCRIPTION

[0035] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0036] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0037] In one aspect, the present invention provides a positive electrode material, wherein the positive electrode material is a core-shell structure, wherein the core portion comprises a carbon-coated Cu 2+ Doped iron-based phosphate sodium ion material, wherein the shell is CuO;

[0038] The iron-based phosphate sodium ion material is selected from at least one of sodium ferric pyrophosphate, sodium ferric phosphate and sodium ferric pyrophosphate.

[0039] In the present invention, the positive electrode material is Cu 2+ Doped iron-based phosphate sodium ion material, carbon layer and copper oxide. The positive electrode material of the present invention is made by doping Cu in the iron-based phosphate sodium ion material. 2+ At the same time, coating the carbon layer and copper oxide can inhibit the sensitivity of the positive electrode material to H2O and CO2, reduce the formation of sodium carbonate on the surface of the material and cause battery bulging, thereby avoiding the interface reaction between the electrode material and the electrolyte. 2+ Doped material Fe 2+ The vacancies dissolved, and Cu 2+The ion particle size is large, which can increase the cell volume of the positive electrode material, thereby improving the diffusion rate of Na + The coated carbon layer can improve the electronic conductivity of the positive electrode material, thereby improving the cycle stability and high-rate performance of the positive electrode material and prolonging the service life of the battery.

[0040] According to the positive electrode material provided in the present application, the carbon-coated Cu 2+ The particle size of the doped iron-based phosphate sodium ion material and the thickness of the shell CuO are not particularly required, as long as the shell can be wrapped on the surface of the core. In order to ensure that the positive electrode material has good cycle performance and good rate performance, preferably, the particle size of the carbon-coated Cu 2+ The particle size of the doped iron-based phosphate sodium ion material is 200-3000 nm.

[0041] In the present application, the content of carbon in the positive electrode material is not particularly required, as long as the carbon layer can be coated on the surface of the carbon-coated Cu 2+ doped iron-based phosphate sodium ion material to improve the electronic conductivity to a certain extent and achieve the purpose of the present application. In order to further improve the cycle stability and high-rate performance of the positive electrode material, in the preferred embodiment, the content of carbon in the positive electrode material is 1-8wt% based on the total weight of the positive electrode material; specifically, it can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt% or 8wt%.

[0042] In the present application, the content of CuO in the positive electrode material is not particularly required, as long as the shell CuO can be coated on the surface of the carbon-coated Cu 2+ doped iron-based phosphate sodium ion material to inhibit the sensitivity of the positive electrode material to H2O and CO2 to a certain extent and achieve the purpose of the present application. In order to further improve the cycle stability and high-rate performance of the positive electrode material and inhibit the sensitivity of the positive electrode material to H2O and CO2, in the preferred embodiment, the content of CuO in the positive electrode material is 0.5-2.5wt% based on the total weight of the positive electrode material; specifically, it can be 0.5wt%, 1wt%, 1.5wt%, 2wt% or 2.5wt%.

[0043] The second aspect of the present application provides a method for preparing a positive electrode material, which comprises: mixing a carbon-coated iron-based phosphate sodium ion material, a copper source and a first solvent, then performing first drying and first calcination.

[0044] In the preferred embodiment, the method for preparing the carbon-coated iron-based phosphate sodium ion material comprises: mixing a sodium source, an iron source, a phosphorus source, a carbon source and a second solvent, then performing reaction, and then performing second drying and second calcination.

[0045] In a more preferred embodiment, the method for preparing the carbon-coated iron-based phosphate-based sodium ion material comprises: mixing a second solvent with a source of iron, then adding a source of carbon and stirring, and finally adding a source of sodium and a source of phosphorus under stirring to react, followed by second drying and grinding, and finally second calcination and grinding under a second protective atmosphere.

[0046] In the method described in the present application, since the copper source reacts with the carbon-coated iron-based phosphate-based sodium ion material after the formation of the latter, only a small amount of Cu 2+ occupies Fe 2+ The dissolved vacancies are doped into the carbon-coated iron-based phosphate-based sodium ion material, and most of the Cu 2+ After the first calcination on the surface of the carbon-coated iron-based phosphate-based sodium ion material, copper oxide is formed to wrap the surface of the material.

[0047] In the present application, there is no special requirement for the content of carbon in the carbon-coated iron-based phosphate-based sodium ion material, as long as the carbon layer can coat the surface of the iron-based phosphate-based sodium ion material to improve the electronic conductivity of the material to a certain extent to achieve the purpose of the present application. Preferably, the molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source is 1:0.6-0.79:1-1.29:0.5-1; specifically, it can be 1:0.6:1:0.5, 1:0.65:1:0.5, 1:0.7:1:0.5, 1:0.75:1:0.5, 1:0.75:1:0.78, 1:0.78:1.28:0.85, or 1:0.78:1.28:0.78.

[0048] In a preferred embodiment, in the method for preparing the carbon-coated iron-based phosphate-based sodium ion material, the reaction temperature is 80-100℃, and the time is 0.5-8h; specifically, the temperature can be 80℃, 85℃, 90℃, 95℃, or 100℃; and the time can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, or 8h.

[0049] In the present application, there is no special requirement for the temperature and time for the second drying of the carbon-coated iron-based phosphate-based sodium ion material, which can refer to the process conditions commonly used in the art. In a preferred embodiment, the conditions for the second drying include a temperature of 90-115℃ and a time of 0.5-8h. Controlling the temperature and time for the second drying within the preferred range is beneficial to reduce the moisture and volatile matter in the material while not causing the decomposition of organic matter (such as citric acid), thereby improving the sintering yield.

[0050] In the present application, the temperature and time for the second calcination for preparing the carbon-coated iron-based phosphate sodium ion material are not particularly required, and the process conditions commonly used in the art can be referred to. In a preferred embodiment, the conditions for the second calcination include a temperature of 450-600°C and a time of 8-15h. Controlling the temperature and time for the second calcination within the preferred range is beneficial to the synthesis of the carbon-coated iron-based phosphate sodium ion material of the present application. Preferably, the second calcination is performed in the presence of a second protective atmosphere to avoid oxidation. Preferably, the second calcination is heated to the temperature at a rate of 5°C / min.

[0051] In the method for preparing the carbon-coated iron-based phosphate sodium ion material of the present application, the selection of the sodium source, iron source, phosphorus source and carbon source is not particularly required, and the conventional selection in the art can be referred to. In the present application, the sodium source that can be used includes, but is not limited to, one or more than two of sodium acetate, sodium carbonate, sodium oxalate and sodium dihydrogen phosphate; the iron source that can be used includes, but is not limited to, one or more than two of ferric nitrate, ferrous oxalate, iron powder, iron oxide and iron phosphate; the phosphorus source that can be used includes, but is not limited to, phosphoric acid, and one or more than two of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate and iron phosphate; and the carbon source that can be used includes, but is not limited to, one or more than two of ascorbic acid, citric acid, oxalic acid, glucose, fructose and sucrose.

[0052] In the method for preparing the carbon-coated iron-based phosphate sodium ion material of the present application, the selection of the second solvent is not particularly required, and the conventional selection in the art can be referred to. In the present application, the second solvent that can be used includes, but is not limited to, one or more than two of water, acetone, anhydrous ethanol and ethylene glycol.

[0053] In the method for preparing the carbon-coated iron-based phosphate sodium ion material of the present application, the selection of the second protective atmosphere is not particularly required, and the conventional selection in the art can be referred to. In the present application, the second protective atmosphere that can be used includes, but is not limited to, one or more than two of argon atmosphere, helium atmosphere, neon atmosphere and nitrogen atmosphere.

[0054] In a preferred embodiment, the method for preparing the positive electrode material includes mixing a copper source and a first solvent, then adding the carbon-coated iron-based phosphate sodium ion material and stirring, then performing first drying and grinding, and finally performing second calcination and grinding in the presence of a first protective atmosphere.

[0055] In the present application, in the method for preparing the positive electrode material, the weight ratio of the carbon-coated iron-based phosphate sodium ion material to copper in the copper source is not particularly required, as long as the Cu 2+The carbon-coated iron-based phosphate sodium-ion material can be doped and copper oxide can be formed on the surface of the carbon-coated iron-based phosphate sodium-ion material to inhibit the sensitivity of the positive electrode material to H2O and CO2 to a certain extent, thereby achieving the purpose of the present application. + Preferably, the weight ratio of the carbon-coated iron-based phosphate sodium-ion material to copper in the copper source is 100:0.5-2; specifically, it can be 100:0.5, 100:1, 100:1.5, or 100:2.

[0056] In the present application, the temperature and time for the first drying of the preparation of the positive electrode material are not particularly required, and the process conditions commonly used in the art can be referred to. In a preferred embodiment, the conditions of the first drying include a temperature of 80-100°C and a time of 0.5-8h. Controlling the temperature and time of the first drying in the preferred range is beneficial to reduce the moisture and volatile matter in the material while not causing the decomposition of the organic matter (such as citric acid), thereby improving the sintering yield.

[0057] In the present application, the temperature and time for the first calcination of the preparation of the positive electrode material are not particularly required, and the process conditions commonly used in the art can be referred to. In a preferred embodiment, the conditions of the second calcination include a temperature of 450-600°C and a time of 20-10h. Controlling the temperature and time of the second calcination in the preferred range is beneficial to synthesize the positive electrode material of the present application. Preferably, the first calcination is carried out in the presence of a first protective atmosphere, thereby avoiding oxidation. Preferably, the first calcination is heated to the temperature at a rate of 5°C / min.

[0058] In the method for preparing the positive electrode material provided by the present application, the selection of the copper source is not particularly required, and the conventional selection in the art can be referred to. In the present application, the copper source that can be used includes but is not limited to one or more than two of copper nitrate, copper acetate, and copper carbonate.

[0059] In the method for preparing the positive electrode material provided by the present application, the selection of the first solvent is not particularly required, and the conventional selection in the art can be referred to. In the present application, the first solvent that can be used includes but is not limited to one or more than two of water, acetone, anhydrous ethanol, and ethylene glycol.

[0060] In the method for preparing the positive electrode material provided by the present application, the selection of the first protective atmosphere is not particularly required, and the conventional selection in the art can be referred to. In the present application, the first protective atmosphere that can be used includes but is not limited to one or more than two of argon atmosphere, helium atmosphere, neon atmosphere, and nitrogen atmosphere.

[0061] The third aspect of the present application provides a positive electrode material prepared by the above method. The positive electrode material has a core-shell structure, the core part includes a carbon-coated Cu2+ The doped iron-based phosphate sodium-ion material has a shell layer of CuO, and the iron-based phosphate sodium-ion material is selected from sodium iron pyrophosphate, sodium iron phosphate, or sodium iron phosphate pyrophosphate.

[0062] The fourth aspect of the present application provides a battery slurry, which comprises a positive electrode material and a third solvent, wherein the positive electrode material is the positive electrode material described above.

[0063] In the present application, the battery slurry further comprises a binder and a conductive agent. The raw materials and amounts of the binder and the conductive agent can be selected according to conventional methods in the art, for example, the binder can be polyvinylidene fluoride (PVDF), and the conductive agent can be carbon black, and the weight ratio of the positive electrode material to the conductive agent and the binder is 8:1:1.

[0064] In the present application, the third solvent that can be used in the battery slurry described above can be a solvent commonly used in the art, for example, including but not limited to one or more of water, ethanol, N-methyl pyrrolidone (NMP), and methanol.

[0065] The fifth aspect of the present application provides a positive electrode tab, which comprises a current collector and a battery slurry disposed on the current collector, wherein the battery slurry is the battery slurry described above. Preferably, the current collector can be a metal material commonly used in the art, for example, including but not limited to platinum (Pt), palladium (Pd), aluminum (Al) foil, and the like.

[0066] The sixth aspect of the present application provides a battery, which comprises a positive electrode tab, wherein the positive electrode tab is the positive electrode tab described above.

[0067] The positive electrode tab prepared by using the battery slurry comprising the positive electrode material described above has good cycle stability and high rate performance, and the service life of the battery is improved.

[0068] The seventh aspect of the present application provides an electric device, which comprises a battery, wherein the battery is the battery described above.

[0069] By using the battery described in the present application, the electric device described in the present application operates well and has a long service life.

[0070] The following examples further illustrate the positive electrode material, the preparation method and the application thereof according to the present application. The examples are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0071] In the following examples, the experimental methods are conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are commercially available unless otherwise specified.

[0072] Example 1

[0073] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0074] An iron source Fe(NO3)3·9H2O was added in 30 ml of deionized water, stirred uniformly at 85°C, and then a carbon source C6H8O6 was added and stirred to form a transparent solution. Then a sodium source CH3COONa and a phosphorus source H3PO4 were added and stirred to react for 1 h until the deionized water evaporated to obtain a gel. The molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source was 1:0.78:1.28:0.78. Then, the obtained gel was placed in a vacuum drying oven at 110°C for drying for 1 h. After drying, the material was ground. The ground material was placed in a porcelain boat and put into a tube furnace. The temperature was raised to 600°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 10 h. After grinding, carbon-coated sodium iron pyrophosphate A1 (Na 1.56 Fe 1.22 P2O7@C) was obtained.

[0075] Preparation of a positive electrode material M1:

[0076] A copper source Cu(NO3)2·3H2O was added in 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A1 was added and stirred for 60 min to obtain a mixed solution S1. The weight ratio of carbon-coated sodium iron pyrophosphate A1 and copper in the copper source was 100:1. The mixed solution S1 was placed in a blast drying oven at 80°C for drying for 3 h. After drying, the material was ground. The ground material was placed in a porcelain boat and put into a tube furnace. The temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h. After grinding, the positive electrode material M1 was obtained.

[0077] Example 2

[0078] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0079] An iron source Fe(NO3)3·9H2O was added in 30 ml of deionized water, stirred uniformly at 85°C, and then a carbon source C6H8O6 was added and stirred to form a transparent solution. Then a sodium source CH3COONa and a phosphorus source H3PO4 were added and stirred to react for 1 h until the deionized water evaporated to obtain a gel. The molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source was 1:0.78:1.28:0.78. Then, the obtained gel was placed in a vacuum drying oven at 110°C for drying for 1 h. After drying, the material was ground. The ground material was placed in a porcelain boat and put into a tube furnace. The temperature was raised to 600°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 10 h. After grinding, carbon-coated sodium iron pyrophosphate A1 (Na 1.56 Fe 1.22 P2O7@C) was obtained.

[0080] Preparation of positive electrode material M2:

[0081] A copper source Cu(NO3)2·3H2O was added in 5 ml of anhydrous ethanol, and then the carbon-coated sodium iron pyrophosphate A1 was added and stirred for 60 min to obtain a mixed solution S2, wherein the weight ratio of the carbon-coated sodium iron pyrophosphate A1 to copper in the copper source was 100:0.5. The mixed solution S2 was placed in a blast drying oven at 80°C and dried for 3 h. After drying, the material was ground. The ground material was placed in a porcelain boat and put into a tube furnace. The temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h. After grinding, the positive electrode material M2 was obtained.

[0082] Example 3

[0083] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0084] An iron source Fe(NO3)3·9H2O was added in 30 ml of deionized water. After stirring uniformly at 85°C, a carbon source C6H8O6 was added and stirred to form a transparent solution. Then, a sodium source CH3COONa and a phosphorus source H3PO4 were added and stirred to react for 1 h until the deionized water evaporated to obtain a gel. The molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source was 1:0.78:1.28:0.78. Then, the obtained gel was placed in a vacuum drying oven at 110°C and dried for 1 h. After drying, the material was ground. The ground material was placed in a porcelain boat and put into a tube furnace. The temperature was raised to 600°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 10 h. After grinding, the carbon-coated sodium iron pyrophosphate A1 (NaFeP2O7@C) was obtained. 1.56 Fe 1.22 P2O7@C);

[0085] Preparation of positive electrode material M3:

[0086] A copper source Cu(NO3)2·3H2O was added in 5 ml of anhydrous ethanol, and then the carbon-coated sodium iron pyrophosphate A1 was added and stirred for 60 min to obtain a mixed solution S3, wherein the weight ratio of the carbon-coated sodium iron pyrophosphate A1 to copper in the copper source was 100:2. The mixed solution S3 was placed in a blast drying oven at 80°C and dried for 3 h. After drying, the material was ground. The ground material was placed in a porcelain boat and put into a tube furnace. The temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h. After grinding, the positive electrode material M3 was obtained.

[0087] Example 4

[0088] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0089] In 30 ml of deionized water, an iron source Fe(NO3)3·9H2O was added, stirred uniformly at 85°C, and then a carbon source C6H8O6 was added and stirred to form a transparent solution, and then a sodium source CH3COONa and a phosphorus source H3PO4 were added and stirred to react for 1 h until the deionized water evaporated to obtain a gel, wherein the molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source was 1:0.75:1:0.78, and then the obtained gel was placed in a vacuum drying box at 110°C and dried for 1 h, and after drying, the material was ground, and the ground material was placed in a porcelain boat and placed in a tube furnace, and heated to 600°C at 5°C / min under a flowing argon atmosphere, and calcined for 10 h, and after grinding, a carbon-coated sodium iron pyrophosphate A2 (Na4Fe3(PO4)2P2O7@C) was obtained.

[0090] Preparation of a positive electrode material M4:

[0091] In 5 ml of anhydrous ethanol, a copper source Cu(NO3)2·3H2O was added, and then the carbon-coated sodium iron pyrophosphate A2 was added and stirred for 60 min to obtain a mixed solution S4, wherein the weight ratio of the carbon-coated sodium iron pyrophosphate A2 and copper in the copper source was 100:1, and the mixed solution S4 was placed in a blast drying oven at 80°C and dried for 3 h, and after drying, the material was ground, and the ground material was placed in a porcelain boat and placed in a tube furnace, and heated to 500°C at 5°C / min under a flowing argon atmosphere, and calcined for 5 h, and after grinding, a positive electrode material M4 was obtained.

[0092] Example 5

[0093] Preparation of a carbon-coated sodium iron pyrophosphate A3:

[0094] In 30 ml of deionized water, an iron source Fe(NO3)3·9H2O was added, stirred uniformly at 85°C, and then a carbon source C6H8O6 was added and stirred to form a transparent solution, and then a sodium source CH3COONa and a phosphorus source H3PO4 were added and stirred to react for 1 h until the deionized water evaporated to obtain a gel, wherein the molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source was 1:0.75:1:0.78, and then the obtained gel was placed in a vacuum drying box at 110°C and dried for 1 h, and after drying, the material was ground, and the ground material was placed in a porcelain boat and placed in a tube furnace, and heated to 600°C at 5°C / min under a flowing argon atmosphere, and calcined for 10 h, and after grinding, a carbon-coated sodium iron pyrophosphate A3 (Na 1.56 Fe 1.22 P2O7@C) was obtained.

[0095] Preparation of a positive electrode material M5:

[0096] A copper source Cu(NO3)2·3H2O was added into 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A3 was added and stirred for 60 min to obtain a mixed solution S5, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A3 to copper in the copper source was 100:1. The mixed solution S5 was placed in a blast drying oven at 80°C and dried for 3 h. After drying, the material was ground. The ground material was placed in a porcelain boat and put into a tube furnace. The temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h. After grinding, the positive electrode material M5 was obtained.

[0097] Example 6

[0098] Preparation of carbon-coated sodium iron pyrophosphate A4:

[0099] A copper source Cu(NO3)2·3H2O was added into 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A3 was added and stirred for 60 min to obtain a mixed solution S5, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A3 to copper in the copper source was 100:1. The mixed solution S5 was placed in a blast drying oven at 80°C and dried for 3 h. After drying, the material was ground. The ground material was placed in a porcelain boat and put into a tube furnace. The temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h. After grinding, the positive electrode material M5 was obtained. 1.56 Fe 1.22 P2O7@C);

[0100] Preparation of positive electrode material M6:

[0101] A copper source Cu(NO3)2·3H2O was added into 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A3 was added and stirred for 60 min to obtain a mixed solution S5, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A3 to copper in the copper source was 100:1. The mixed solution S5 was placed in a blast drying oven at 80°C and dried for 3 h. After drying, the material was ground. The ground material was placed in a porcelain boat and put into a tube furnace. The temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h. After grinding, the positive electrode material M5 was obtained.

[0102] Example 7

[0103] Preparation of carbon-coated sodium iron pyrophosphate A5:

[0104] In 30 ml of deionized water, an iron source Fe(NO3)3·9H2O was added, stirred uniformly at 85°C, and then a carbon source C6H8O6 was added and stirred to form a transparent solution, and then a sodium source CH3COONa and a phosphorus source H3PO4 were added and stirred to react for 1 h until the deionized water evaporated to obtain a gel, wherein the molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source was 1:0.82:1.28:0.78, and then the obtained gel was placed in a vacuum drying box at 110°C for drying for 1 h, and after drying, grinding was performed, and the ground material was placed in a porcelain boat and placed in a tube furnace, and calcined at 600°C for 10 h under a flowing argon atmosphere with a temperature increase of 5°C / min, and after grinding, a carbon-coated sodium iron pyrophosphate A5 (Na 1.56 Fe 1.22 P2O7@C) was obtained.

[0105] Preparation of a positive electrode material M7:

[0106] In 5 ml of anhydrous ethanol, a copper source Cu(NO3)2·3H2O was added, and then the carbon-coated sodium iron pyrophosphate A5 was added and stirred for 60 min to obtain a mixed solution S7, wherein the weight ratio of the carbon-coated sodium iron pyrophosphate A5 and the copper in the copper source was 100:1, and the mixed solution S7 was placed in a blast drying oven at 80°C for drying for 3 h, and after drying, grinding was performed, and the ground material was placed in a porcelain boat and placed in a tube furnace, and calcined at 500°C for 5 h under a flowing argon atmosphere with a temperature increase of 5°C / min, and after grinding, the positive electrode material M7 was obtained.

[0107] Example 8

[0108] Preparation of a carbon-coated sodium iron pyrophosphate A1:

[0109] In 30 ml of deionized water, an iron source Fe(NO3)3·9H2O was added, stirred uniformly at 85°C, and then a carbon source C6H8O6 was added and stirred to form a transparent solution, and then a sodium source CH3COONa and a phosphorus source H3PO4 were added and stirred to react for 1 h until the deionized water evaporated to obtain a gel, wherein the molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source was 1:0.78:1.28:0.78, and then the obtained gel was placed in a vacuum drying box at 110°C for drying for 1 h, and after drying, grinding was performed, and the ground material was placed in a porcelain boat and placed in a tube furnace, and calcined at 600°C for 10 h under a flowing argon atmosphere with a temperature increase of 5°C / min, and after grinding, a carbon-coated sodium iron pyrophosphate A1 (Na 1.56 Fe 1.22 P2O7@C) was obtained.

[0110] Preparation of a positive electrode material M8:

[0111] A copper source Cu(NO3)2·3H2O was added into 5 ml of anhydrous ethanol, and then carbon-coated sodium iron phosphate A1 was added and stirred for 60 min to obtain a mixed solution S8, wherein the weight ratio of carbon-coated sodium iron phosphate A1 to copper in the copper source was 100:0.3. The mixed solution S8 was placed in a blast drying oven at 80°C and dried for 3 h. After drying, the material was ground, placed in a porcelain boat, and placed in a tube furnace. The temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h. After grinding, the positive electrode material M8 was obtained.

[0112] Example 9

[0113] Preparation of carbon-coated sodium iron phosphate A6:

[0114] A copper source Cu(NO3)2·3H2O was added into 5 ml of anhydrous ethanol, and then carbon-coated sodium iron phosphate A1 was added and stirred for 60 min to obtain a mixed solution S8, wherein the weight ratio of carbon-coated sodium iron phosphate A1 to copper in the copper source was 100:0.3. The mixed solution S8 was placed in a blast drying oven at 80°C and dried for 3 h. After drying, the material was ground, placed in a porcelain boat, and placed in a tube furnace. The temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h. After grinding, the positive electrode material M8 was obtained.

[0115] Preparation of positive electrode material M9:

[0116] A copper source Cu(NO3)2·3H2O was added into 5 ml of anhydrous ethanol, and then carbon-coated sodium iron phosphate A1 was added and stirred for 60 min to obtain a mixed solution S8, wherein the weight ratio of carbon-coated sodium iron phosphate A1 to copper in the copper source was 100:0.3. The mixed solution S8 was placed in a blast drying oven at 80°C and dried for 3 h. After drying, the material was ground, placed in a porcelain boat, and placed in a tube furnace. The temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h. After grinding, the positive electrode material M8 was obtained.

[0117] Example 10

[0118] Preparation of carbon-coated sodium iron phosphate A6:

[0119] In 30 ml of deionized water, an iron source Fe(NO3)3·9H2O was added, stirred uniformly at 85°C, and then a carbon source C6H8O6 was added and stirred to form a transparent solution, and then a sodium source CH3COONa and a phosphorus source H3PO4 were added and stirred to react for 1 h until the deionized water volatilized to obtain a gel, wherein the molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source was 1:0.5:1:0.4, and then the obtained gel was placed in a vacuum drying box at 110°C for drying for 1 h, and after drying, the material was ground, and then the ground material was placed in a porcelain boat and put into a tube furnace, and then the temperature was raised to 600°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 10 h, and after grinding, carbon-coated sodium iron phosphate A6 (Na2Fe(PO4)2@C) was obtained.

[0120] Preparation of the positive electrode material M10:

[0121] In 5 ml of anhydrous ethanol, a copper source Cu(NO3)2·3H2O was added, and then the carbon-coated sodium iron phosphate A6 was added and stirred for 60 min to obtain a mixed solution S10, wherein the weight ratio of the carbon-coated sodium iron phosphate A6 and copper in the copper source was 100:0.3, and then the mixed solution S10 was placed in a blast drying oven at 80°C for drying for 3 h, and after drying, the material was ground, and then the ground material was placed in a porcelain boat and put into a tube furnace, and then the temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 5 h, and after grinding, the positive electrode material M10 was obtained.

[0122] Example 11

[0123] Preparation of the carbon-coated sodium iron pyrophosphate A7:

[0124] In 30 ml of deionized water, an iron source Fe(NO3)3·9H2O was added, stirred uniformly at 85°C, and then a carbon source C6H8O6 was added and stirred to form a transparent solution, and then a sodium source CH3COONa and a phosphorus source H3PO4 were added and stirred to react for 1 h until the deionized water volatilized to obtain a gel, wherein the molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source, and carbon in the carbon source was 1:0.78:1.28:0.78, and then the obtained gel was placed in a vacuum drying box at 100°C for drying for 2 h, and after drying, the material was ground, and then the ground material was placed in a porcelain boat and put into a tube furnace, and then the temperature was raised to 500°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 15 h, and after grinding, the carbon-coated sodium iron pyrophosphate A7 (Na2Fe2P2O7@C) was obtained. 1.56 Fe 1.22 P2O7@C);

[0125] Preparation of the positive electrode material M11:

[0126] A copper source Cu(NO3)2·3H2O was added into 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A7 was added and stirred for 60 min to obtain a mixed solution S11, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A7 to copper in the copper source was 100:1. The mixed solution S11 was placed in a blast drying oven at 90°C and dried for 2 h. After drying, the material was ground. The ground material was placed in a porcelain boat and placed in a tube furnace. The temperature was raised to 600°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 4 h. After grinding, the positive electrode material M11 was obtained.

[0127] Comparative Example 1

[0128] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0129] A copper source Cu(NO3)2·3H2O was added into 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A7 was added and stirred for 60 min to obtain a mixed solution S11, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A7 to copper in the copper source was 100:1. The mixed solution S11 was placed in a blast drying oven at 90°C and dried for 2 h. After drying, the material was ground. The ground material was placed in a porcelain boat and placed in a tube furnace. The temperature was raised to 600°C at a rate of 5°C / min under a flowing argon atmosphere and calcined for 4 h. After grinding, the positive electrode material M11 was obtained. 1.56 Fe 1.22 P2O7@C).

[0130] Comparative Example 2

[0131] In accordance with the manner of Example 1, the difference is that, in the process of preparing the positive electrode material, copper oxide powder is used instead of the copper source Cu(NO3)2·3H2O.

[0132] Test Example

[0133] (1) The positive electrode materials prepared in the examples and comparative examples were characterized, Figure 1 is the XRD pattern of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1; Figure 2 is the XRD magnification pattern of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1; Figure 3 is the TG curve of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1; Figure 4 is the electron microscope image of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1, wherein, Figure 4 (a) is the electron microscope image of the positive electrode material prepared in Example 1, Figure 4 (b) is the electron microscope image of the positive electrode material prepared in Example 2, Figure 4(c) is an electron microscope image of the positive electrode material prepared in Example 3, Figure 4 (d) is an electron microscope image of the positive electrode material prepared in Comparative Example 1; Figure 5 is an EDS image of the positive electrode material prepared in Examples 1-3, wherein, Figure 5 (a) is an EDS image of the positive electrode material prepared in Example 1, Figure 5 (b) is an EDS image of the positive electrode material prepared in Example 2, Figure 5 (c) is an EDS image of the positive electrode material prepared in Example 3;

[0134] It can be seen from Figure 1 that the XRD diffraction peaks are consistent with the JCPDS data (PDF #01-086-4091), the crystal structure is P-1 type space group of triclinic system, and the prepared positive electrode material has no obvious impurity peak, indicating that sodium iron pyrophosphate is synthesized in the preparation process;

[0135] It can be seen from Figure 2 that the characteristic peaks of Examples 1-3 near 10.7° and 16.7° are shifted to the left, indicating that Cu 2+ successfully occupies Fe 2+ and is doped into sodium iron pyrophosphate;

[0136] It can be seen from Figure 3 that the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 have good thermal stability below 380℃, and the carbon starts to decompose after 380℃, and after the carbon decomposition is completed at 450℃, the thermal stability is still good, and the average carbon content of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 is about 4.0wt%;

[0137] It can be seen from Figure 4 that the average particle size of the positive electrode material prepared in Comparative Example 1 is about 1000nm, the particle size is small but uniform, the average particle size of the positive electrode material prepared in Examples 1-3 is about 2000nm, the particle size is uniform, and it can be seen that the appearance morphology of Examples 1-3 changes compared with Comparative Example 1 after adding copper source;

[0138] It can be seen from Figure 5 that the element copper of the positive electrode materials prepared in Examples 1-3 is uniformly distributed on the surface of the positive electrode material, which indicates that under the method described in the application, the copper source becomes CuO uniformly wrapped on the surface of the material.

[0139] (2) The thermal gravimetric analysis (TG) of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 is carried out by the following test method: 8mg of the prepared positive electrode material is taken, and the thermal gravimetric analysis test is carried out under oxygen atmosphere at a heating rate of 5℃ / min, to determine the thermal stability and carbon content of the positive electrode material, wherein the test results of the carbon content of the positive electrode material are shown in Table 1;

[0140] The positive electrode materials prepared in Examples 1-3 and Comparative Example 1 were subjected to elemental analysis, and the test results are shown in Table 1.

[0141] Table 1

[0142]

[0143] As can be seen from the data in Table 1, the weight content of copper element in the positive electrode materials prepared in Examples 1-3 substantially matches the weight of copper ions in the copper source added in each of Examples 1-3, which also indicates that the copper ions in the added copper source all participate in the reaction. The positive electrode material prepared in Comparative Example 1 does not contain copper element because no copper source is added.

[0144] (3) The electrochemical performance of the positive electrode materials prepared in Examples 1-11 and Comparative Examples 1-2 was tested, all according to the following method:

[0145] (a) The positive electrode materials prepared in Examples 1-11 and Comparative Examples 1-2, the conductive agent-carbon black and PVDF were added in the solvent-NMP at a weight ratio of 8:1:1, then stirred in a vacuum stirrer to form a stable and uniform battery slurry, and the above positive electrode slurry was coated on the current collector-aluminum foil and dried at 105°C for 6h to obtain a positive electrode sheet;

[0146] (b) A metal sodium sheet with a proper size was cut as a negative electrode sheet;

[0147] (c) 1 mol of sodium salt-NaPF6 was dissolved in 1 L of organic solvent (the volume ratio of propylene carbonate and fluoroethylene carbonate was 100:6) to obtain an electrolyte;

[0148] (d) In a glove box, the positive electrode sheet prepared in step (a), the separator-glass fiber separator, the negative electrode sheet prepared in step (b) were alternately stacked under an argon atmosphere, and the electrolyte prepared in step (c) was injected to assemble a CR2032 button cell;

[0149] (e) The above button cell was placed at 25°C for 12h, and tested on a Land-2001A battery test system. Each battery was subjected to charge-discharge cycle test and rate performance test at 25°C with a current of 1C rate, and the voltage range was 1.5V-4V. The capacity retention rate after 50 cycles was equal to the ratio of the discharge capacity after 50 cycles to the discharge capacity of the first cycle, and the specific discharge capacity of the first cycle was equal to the ratio of the discharge capacity of the first cycle to the weight of the positive electrode material in the battery. The battery capacity retention rate after 50 cycles and the specific discharge capacity of the first cycle of the battery at 0.1C and 5C rates were recorded, and the test results are shown in Table 2, Figure 6is the charge-discharge curve of the battery prepared from the positive electrode material prepared in Example 1-3 and Comparative Example 1 at 0.1C; Figure 7 is the cycle performance graph of the battery prepared from the positive electrode material prepared in Example 1-3 and Comparative Example 1 at 1C; Figure 8 is the discharge specific capacity test graph of the battery prepared from the positive electrode material prepared in Example 1-3 and Comparative Example 1 at 0.1C, 0.2C, 0.5C, 1C, 2C and 5C rate;

[0150] It can be seen from Figure 6 that the battery prepared from the positive electrode material prepared in Example 1-3 and Comparative Example 1 has three charge-discharge platforms at about 2.5V, 3.0V and 3.3V when charged and discharged at 0.1C, which indicates that the Na + deintercalation is a single-phase reaction.

[0151] It can be seen from Figure 7 that the discharge specific capacities of Example 1, Example 2 and Example 3 after 50 cycles at 1C rate are 82.1 mAh / g, 75.7 mAh / g and 78.5 mAh / g, respectively, and the battery capacity retention rates are 99.7%, 99.4% and 99.5%, respectively, while the discharge specific capacity of Comparative Example 1 after 50 cycles at 1C rate is 74.4 mAh / g, and the battery capacity retention rate is 99.2%, which indicates that the battery prepared from the positive electrode material prepared in Example 1-3 has excellent cycle performance.

[0152] It can be seen from Figure 8 that at 0.1C, 0.2C, 0.5C, 1C, 2C and 5C rate, the discharge specific capacities of Example 1 are 91.7, 88.3, 84.8, 81.6, 77.8 and 71.0 mAh / g, respectively, and the discharge specific capacities of Example 1, Example 2 and Example 3 at 5C rate are 71.03%, 63.3% and 67.5% of the discharge specific capacity at 0.1C rate, while the discharge specific capacity of Comparative Example 1 at 5C rate is 62.2% of the discharge specific capacity at 0.1C rate, which indicates that the battery prepared from the positive electrode material prepared in Example 1-3 has good high-rate performance.

[0153] Table 2

[0154]

[0155] It can be seen from the data in Table 2 that the positive electrode material according to the present application has good electrochemical performance, and the battery prepared from the positive electrode material according to the present application has good cycle stability and high-rate performance, and the battery prepared from the positive electrode material of Example 1 has significantly better effect.

[0156] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A positive electrode material, characterized in that The positive electrode material is a core-shell structure, wherein the core portion comprises carbon-coated Cu 2+ Doped iron-based phosphate sodium ion material, wherein the shell is CuO; The Cu 2+ Occupies Fe in iron-based phosphate sodium ion materials 2+ Dissolution vacancies; The iron-based phosphate sodium ion material is selected from at least one of sodium ferric pyrophosphate, sodium ferric phosphate and sodium ferric pyrophosphate.

2. The positive electrode material according to claim 1, characterized in that Based on the total weight of the positive electrode material, the carbon content in the positive electrode material is 1-8wt%, and the CuO content in the positive electrode material is 0.5-2.5wt%.

3. A method for preparing the positive electrode material according to claim 1 or 2, characterized in that: The method comprises: mixing a carbon-coated iron-based phosphate sodium ion material, a copper source and a first solvent, and then performing a first drying and a first calcination.

4. The method according to claim 3, characterized in that The preparation method of the carbon-coated iron-based phosphate sodium ion material comprises: mixing a sodium source, an iron source, a phosphorus source, a carbon source and a second solvent, reacting the mixture, and then performing a second drying and a second calcination.

5. The method according to claim 4, characterized in that The molar ratio of sodium in the sodium source, iron in the iron source, phosphorus in the phosphorus source and carbon in the carbon source is 1:0.6-0.79:1-1.29:0.5-1.

6. The method according to claim 4 or 5, characterized in that The method satisfies at least one of the following conditions: The reaction temperature is 80-100°C and the reaction time is 0.5-8h; The second drying conditions include: temperature of 90-115°C and time of 0.5-8h; The conditions for the second calcination include: a temperature of 450-600° C. and a time of 8-15 hours.

7. The method according to claim 3, characterized in that The weight ratio of the carbon-coated iron-based phosphate sodium ion material to the copper in the copper source is 100:0.5-2.

8. The method according to claim 3 or 7, characterized in that The method satisfies at least one of the following conditions: The first drying conditions include: temperature of 80-100°C and time of 0.5-8h; The conditions for the first calcination include: a temperature of 450-600° C. and a time of 2-10 hours.

9. A positive electrode material prepared by the method according to any one of claims 3 to 8.

10. A battery slurry, characterized in that: The battery slurry includes a positive electrode material and a third solvent, and the positive electrode material is the positive electrode material according to any one of claims 1 to 2 and 9.

11. A positive electrode plate, comprising a current collector and a battery slurry disposed on the current collector, characterized in that: The battery slurry is the battery slurry according to claim 10.

12. A battery comprising a positive electrode plate, characterized in that: The positive electrode sheet is the positive electrode sheet according to claim 11.

13. An electrical device comprising a battery, characterized in that: The battery is the battery according to claim 12.

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