Positive electrode material, and preparation method therefor and use thereof

Abstract

A positive electrode material, and a preparation method therefor and the use thereof. The positive electrode material has a core-shell structure, wherein a core part comprises a carbon-coated Cu2+-doped iron-based phosphate sodium-ion material, and a shell layer is CuO. The iron-based phosphate sodium-ion material is selected from ferric sodium pyrophosphate, ferric sodium phosphate or ferric sodium phosphate pyrophosphate. The preparation method for the positive electrode material comprises: mixing the carbon-coated iron-based phosphate sodium-ion material, a copper source and a first solvent, and then subjecting the mixture to first drying and first calcination.

Description

A positive electrode material and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. CN202311868428.3 filed on December 29, 2023. The full text of the above-mentioned Chinese patent application is hereby cited as part of this application. Technical Field

[0003] The present invention relates to the field of batteries, and in particular to a positive electrode material and a preparation method and application thereof. Background Art

[0004] The development of resource-rich and environmentally friendly sodium-ion battery technology is of great significance and practical value to the development of large-scale energy storage technology.

[0005] However, the lack of low-cost and long-life cathode materials remains a major obstacle to the commercial application of sodium-ion batteries. Researchers have studied a variety of cathode materials for sodium-ion batteries, including transition metal oxides, polyanionic compounds, and Prussian blue analogs. Among them, sodium iron phosphate pyrophosphate is one of the most promising cathode materials for sodium-ion batteries. NASICON-structured materials have attracted attention due to their advantages such as three-dimensional ion transport tunnels, high operating potential, stable structure, low cost, and long cycle life. Major cathode materials include phosphates, pyrophosphates, and mixed polyanions, such as Na₃V₂(PO₄)₃, Na₃V₂(PO₄)₂F₃, Na₂FeP₂Oₐ, Na₂MnP₂Oₐ, Na₂CoP₂Oₐ, NaₐV₃(P₂Oₐ)₄, NaₐV₄(P₂Oₐ)₄(PO₄), and Na₄Fe₃(PO₄)₂(P₂Oₐ). However, the development of iron-phosphate cathode materials continues to be hampered by poor electronic conductivity, slow ion diffusion, difficulty controlling their structure after high-temperature sintering, and sensitivity to H2O and CO2. This sensitivity can lead to surface oxidation of iron-phosphate cathode materials, producing substances such as sodium carbonate. This can damage the electrode material, leading to electrolyte corrosion and other issues, ultimately resulting in a high initial irreversible capacity. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of poor electronic conductivity, slow ion diffusion rate and sensitivity to H2O and CO2 in existing iron-based phosphate cathode materials, and to provide a cathode material that can suppress the sensitivity to H2O and CO2 and Na + The diffusion rate is fast, the electrochemical performance of the material is good, and the preparation method is simple and efficient.

[0007] In order to achieve the above object, the present invention provides a positive electrode material, which has a core-shell structure, wherein the core comprises a carbon-coated Cu 2+ Doped iron-based phosphate sodium ion material, wherein the shell is CuO;

[0008] The iron-based phosphate sodium ion material is selected from at least one of sodium ferric pyrophosphate, sodium ferric phosphate and sodium ferric pyrophosphate.

[0009] Preferably, based on the total weight of the positive electrode material, the carbon content in the positive electrode material is 1-8 wt %, and the CuO content in the positive electrode material is 0.5-2.5 wt %.

[0010] A second aspect of the present invention provides a method for preparing a positive electrode material, the method comprising: 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.

[0011] Preferably, 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.

[0012] 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.

[0013] Preferably, the method satisfies at least one of the following conditions:

[0014] The reaction temperature is 80-100°C and the reaction time is 0.5-8h;

[0015] The second drying conditions include: temperature of 90-115°C and time of 0.5-8h;

[0016] The conditions for the second calcination include: a temperature of 450-600° C. and a time of 8-15 hours.

[0017] Preferably, 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.

[0018] Preferably, the method satisfies at least one of the following conditions:

[0019] The first drying conditions include: temperature of 80-100°C and time of 0.5-8h;

[0020] The conditions for the first calcination include: a temperature of 450-600° C. and a time of 2-10 hours.

[0021] The third aspect of the present invention provides a positive electrode material prepared by the above method.

[0022] A fourth aspect of the present invention provides a battery slurry, comprising a positive electrode material and a third solvent, wherein the positive electrode material is the positive electrode material described above.

[0023] A fifth aspect of the present invention provides a positive electrode plate, comprising a current collector and a battery slurry disposed on the current collector, wherein the battery slurry is the above-mentioned battery slurry.

[0024] A sixth aspect of the present invention provides a battery, comprising a positive electrode plate, wherein the positive electrode plate is the positive electrode plate described above.

[0025] A seventh aspect of the present invention provides an electrical device, the electrical device comprising a battery, and the battery is the battery described above.

[0026] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0027] (1) The cathode material of the present invention has excellent electrochemical performance and excellent cycle and high rate performance. This may be because the CuO coating can inhibit the sensitivity of the cathode material to H2O and CO2, reduce the formation of sodium carbonate on the surface of the material and cause battery bulging, and thus avoid the interface reaction between the electrode material and the electrolyte. Secondly, Cu 2+ Doped material Fe 2+ The dissolved vacancies due to Cu 2+ (0.073nm) than Fe 2+ (0.061nm) is large, so the unit cell volume of the positive electrode material can be increased, thereby improving the Na + The diffusion rate of the material is improved, and the electrochemical performance is ultimately improved;

[0028] (2) The preparation method of the present invention has a simple and efficient synthesis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is an XRD pattern of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1;

[0030] FIG2 is an enlarged XRD pattern of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1;

[0031] FIG3 is a TG graph of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1;

[0032] FIG4 is an electron microscope image of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1;

[0033] FIG5 is an EDS graph of the positive electrode material prepared in Example 1-3;

[0034] FIG6 is a charge and discharge curve of a battery prepared with the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 at 0.1C;

[0035] FIG7 is a graph showing the cycle performance of batteries prepared using the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 at 1C;

[0036] 8 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

[0037] 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.

[0038] 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.

[0039] 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;

[0040] The iron-based phosphate sodium ion material is selected from at least one of sodium ferric pyrophosphate, sodium ferric phosphate and sodium ferric pyrophosphate.

[0041] 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, and thus avoid 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 larger, which can increase the unit cell volume of the positive electrode material, thereby increasing the Na + The diffusion rate of the positive electrode material is increased, and the coated carbon layer can improve its electronic conductivity, thereby improving the cycle stability and high rate performance of the positive electrode material and extending the service life of the battery.

[0042] According to the above-mentioned positive electrode material provided by the present invention, for the core carbon-coated Cu 2+ There is no special requirement for the particle size of the doped iron-based phosphate sodium ion material and the thickness of the shell CuO, as long as the shell can wrap around the core surface. In order to ensure that the positive electrode material has both good cycle performance and good rate performance, preferably, the core carbon-coated CuO 2+ The particle size of the doped iron-based phosphate sodium ion material is 200-3000 nm.

[0043] In the present invention, there is no special requirement for the carbon content in the positive electrode material, as long as the carbon layer can be coated on the Cu 2+ The surface of the doped iron-based phosphate sodium ion material can improve its electronic conductivity to a certain extent, thereby achieving the objectives of the present invention. To further improve the cycle stability and high-rate performance of the positive electrode material, in a preferred embodiment, the carbon content in the positive electrode material is 1-8 wt% based on the total weight of the positive electrode material; specifically, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, or 8 wt%.

[0044] In the present invention, there is no special requirement for the content of CuO in the positive electrode material, as long as the shell CuO can be coated on the carbon-coated Cu core. 2+ The surface of the doped iron-based phosphate sodium ion material can suppress the positive electrode material's sensitivity to H2O and CO2 to a certain extent, thereby achieving the objectives of the present invention. To further improve the cycling stability and high-rate performance of the positive electrode material and suppress its sensitivity to H2O and CO2, in a preferred embodiment, the CuO content in the positive electrode material is 0.5-2.5 wt% based on the total weight of the positive electrode material; specifically, it can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, or 2.5 wt%.

[0045] A second aspect of the present invention provides a method for preparing a positive electrode material, the method comprising: 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.

[0046] In a preferred embodiment, 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.

[0047] In a more preferred embodiment, the preparation method of the carbon-coated iron-based phosphate sodium ion material includes: mixing the iron source solvent and the second solvent, then adding the carbon source and stirring, finally adding the sodium source and the phosphorus source under stirring conditions to react, then performing a second drying and grinding, and finally performing a second calcination and grinding under the conditions of a second protective atmosphere.

[0048] In the method of the present invention, since the copper source is reacted with the carbon-coated iron-based phosphate sodium ion material after it is formed, only a small amount of Cu 2+ Occupies Fe 2+ The dissolved vacancies are doped into the carbon-coated iron-based phosphate sodium ion material, and most of the Cu 2+ After the first calcination, copper oxide is formed on the surface of the carbon-coated iron-based phosphate sodium ion material and wrapped around the surface of the material.

[0049] In the present invention, there is no special requirement for the carbon content in the carbon-coated iron-based sodium phosphate material. As long as the carbon layer can be coated on the surface of the iron-based sodium phosphate material, its electronic conductivity can be improved to a certain extent, thereby achieving the purpose of the present invention. 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.

[0050] In a preferred embodiment, in the preparation method of the carbon-coated iron-based phosphate sodium ion material, the reaction temperature is 80-100°C and the time is 0.5-8h; specifically, the temperature can be 80°C, 85°C, 90°C, 95°C or 100°C; the time can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h or 8h.

[0051] In the present invention, there are no special requirements for the temperature and time of the second drying for preparing the carbon-coated iron-based phosphate sodium ion material, and the process conditions commonly used in the art can be referred to. In a preferred embodiment, the conditions for the second drying include: a temperature of 90-115°C and a time of 0.5-8 hours. Controlling the temperature and time of the second drying within the preferred range is beneficial to reducing 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.

[0052] In the present invention, there are no special requirements for the temperature and time of the second calcination for preparing the carbon-coated iron-based phosphate sodium ion material, and the process conditions conventionally 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 8-15h. Controlling the temperature and time of the second calcination within the preferred range is beneficial to the synthesis of the carbon-coated iron-based phosphate sodium ion material described in the present invention. Preferably, the second calcination is carried out 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.

[0053] In the method for preparing a carbon-coated iron-based phosphate sodium ion material provided by the present invention, there are no special requirements for the selection of sodium source, iron source, phosphorus source and carbon source, and the conventional selection in the field can be referred to. In the present invention, the sodium source that can be used includes but is not limited to one or more 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 of ferric nitrate, ferrous oxalate, iron powder, ferric oxide and ferric phosphate; the phosphorus source that can be used includes but is not limited to phosphoric acid, and one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate and ferric phosphate can also be selected; the carbon source that can be used includes but is not limited to one or more of ascorbic acid, citric acid, oxalic acid, glucose, fructose and sucrose.

[0054] In the method for preparing a carbon-coated iron-based phosphate sodium ion material provided by the present invention, there are no special requirements for the selection of the second solvent, and conventional selection in the art can be referred to. In the present invention, the second solvent that can be used includes, but is not limited to, one or more of water, acetone, anhydrous ethanol, and ethylene glycol.

[0055] In the method for preparing a carbon-coated iron-based phosphate sodium ion material provided by the present invention, there are no special requirements for the selection of a second protective atmosphere, and conventional selection in the art can be referred to. In the present invention, the second protective atmosphere that can be used includes, but is not limited to, one or more of an argon atmosphere, a helium atmosphere, a neon atmosphere, and a nitrogen atmosphere.

[0056] In a preferred embodiment, the preparation method of the positive electrode material comprises: mixing a copper source and a first solvent, then adding a carbon-coated iron-based phosphate sodium ion material and stirring, then performing a first drying and grinding, and finally performing a second calcination and grinding in the presence of a first protective atmosphere.

[0057] In the present invention, in the preparation method of the positive electrode material, there is no special requirement for the weight ratio of the carbon-coated iron-based phosphate sodium ion material and the copper in the copper source, as long as the Cu in the copper source is 2+The carbon-coated iron-based phosphate sodium ion material can be doped and copper oxide can be formed on its surface to suppress the sensitivity of the positive electrode material to H2O and CO2 to a certain extent. + Preferably, 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; specifically, it can be 100:0.5, 100:1, 100:1.5 or 100:2.

[0058] In the present invention, there are no specific requirements for the temperature and time of the first drying process for preparing the positive electrode material, and the process conditions commonly used in the art can be referred to. In a preferred embodiment, the conditions for the first drying include: a temperature of 80-100°C and a time of 0.5-8 hours. Controlling the temperature and time of the first drying within the preferred range is beneficial for reducing moisture and volatile matter in the material while preventing the decomposition of organic matter (such as citric acid), thereby improving the sintering yield.

[0059] In the present invention, there are no specific requirements for the temperature and time of the first calcination for preparing the positive electrode material; the process conditions commonly used in the art can be referenced. In a preferred embodiment, the conditions for the second calcination include a temperature of 450-600°C and a time of 20-10 hours. Controlling the temperature and time of the second calcination within the preferred ranges facilitates the synthesis of the positive electrode material of the present invention. Preferably, the first calcination is performed in the presence of a first protective atmosphere to prevent oxidation. Preferably, the first calcination is heated to the above temperature at a rate of 5°C / min.

[0060] In the method for preparing the positive electrode material provided by the present invention, there are no special requirements for the selection of the copper source, and the selection can refer to conventional methods in the art. In the present invention, the copper source that can be used includes, but is not limited to, one or more of copper nitrate, copper acetate, and copper carbonate.

[0061] In the method for preparing a positive electrode material provided by the present invention, there are no special requirements for the selection of the first solvent, and the selection can refer to conventional methods in the art. In the present invention, the first solvent that can be used includes, but is not limited to, one or more of water, acetone, anhydrous ethanol, and ethylene glycol.

[0062] In the method for preparing the positive electrode material provided by the present invention, there are no special requirements for the selection of the first protective atmosphere, and the conventional selection in the art can be referred to. In the present invention, the first protective atmosphere that can be used includes, but is not limited to, one or more of argon atmosphere, helium atmosphere, neon atmosphere, and nitrogen atmosphere.

[0063] The third aspect of the present invention provides a positive electrode material prepared by the above method. The positive electrode material is a core-shell structure, wherein the core portion comprises carbon-coated Cu2+ The doped iron-based phosphate sodium ion material, the shell layer is CuO, and the iron-based phosphate sodium ion material is selected from sodium ferric pyrophosphate, sodium ferric phosphate or sodium ferric pyrophosphate.

[0064] A fourth aspect of the present invention provides a battery slurry, comprising a positive electrode material and a third solvent, wherein the positive electrode material is the positive electrode material described above.

[0065] In the present invention, the battery slurry further includes a binder and a conductive agent. The raw materials and amounts of the binder and conductive agent can be selected according to conventional methods in the art. For example, the binder can be polyvinylidene fluoride (PVDF), the conductive agent can be carbon black, and the weight ratio of the positive electrode material to the conductive agent and binder is 8:1:1.

[0066] In the present invention, the third solvent that can be used in the battery slurry can refer to the solvents commonly used in the art, for example, including but not limited to one or more of water, ethanol, N-methylpyrrolidone (NMP) and methanol.

[0067] A fifth aspect of the present invention provides a positive electrode sheet, comprising 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 made of a metal material commonly used in the art, such as, but not limited to, platinum (Pt), palladium (Pd), and aluminum (Al) foil.

[0068] A sixth aspect of the present invention provides a battery, comprising a positive electrode plate, wherein the positive electrode plate is the positive electrode plate described above.

[0069] By adopting the positive electrode plate prepared by the battery slurry including the above-mentioned positive electrode material of the present invention, the battery provided by the present invention has good cycle stability and high rate performance, while its service life is increased.

[0070] A seventh aspect of the present invention provides an electrical device, the electrical device comprising a battery, and the battery is the battery described above.

[0071] By adopting the battery of the present invention, the electrical equipment of the present invention operates well and has a long service life.

[0072] The following examples further illustrate the cathode material, preparation method, and application of the present invention. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the scope of protection of the present invention is not limited to the following examples.

[0073] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0074] Example 1

[0075] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0076] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.78:1.28:0.78, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and obtain carbon-coated sodium iron pyrophosphate A1 (Na 1.56 Fe 1.22 P2O7@C);

[0077] Preparation of positive electrode material M1:

[0078] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A1 was added and stirred for 60 minutes to obtain a mixed solution S1, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A1 to copper in the copper source was 100:1. The mixed solution S1 was placed in an 80°C forced air drying oven and dried for 3 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tube furnace. The temperature was raised to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M1 was obtained.

[0079] Example 2

[0080] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0081] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.78:1.28:0.78, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and obtain carbon-coated sodium iron pyrophosphate A1 (Na 1.56 Fe 1.22 P2O7@C);

[0082] Preparation of positive electrode material M2:

[0083] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A1 was added and stirred for 60 minutes to obtain a mixed solution S2, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A1 to copper in the copper source was 100:0.5. The mixed solution S2 was placed in a forced air drying oven at 80°C and dried for 3 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tubular furnace. The temperature was raised to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M2 was obtained.

[0084] Example 3

[0085] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0086] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.78:1.28:0.78, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and obtain carbon-coated sodium iron pyrophosphate A1 (Na 1.56 Fe 1.22 P2O7@C);

[0087] Preparation of positive electrode material M3:

[0088] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A1 was added and stirred for 60 minutes to obtain a mixed solution S3, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A1 to copper in the copper source was 100:2. The mixed solution S3 was placed in an 80°C forced air drying oven and dried for 3 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tubular furnace. The temperature was raised to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M3 was obtained.

[0089] Example 4

[0090] Preparation of carbon-coated sodium iron pyrophosphate A2:

[0091] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.75:1:0.78, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and obtain carbon-coated sodium iron phosphate pyrophosphate A2 (Na4Fe3(PO4)2P2O7@C) after grinding;

[0092] Preparation of positive electrode material M4:

[0093] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron phosphate pyrophosphate A2 was added and stirred for 60 minutes to obtain a mixed solution S4, wherein the weight ratio of carbon-coated sodium iron phosphate pyrophosphate A2 to copper in the copper source was 100:1. The mixed solution S4 was placed in a forced air drying oven at 80°C and dried for 3 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tubular furnace. The temperature was raised to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M4 was obtained.

[0094] Example 5

[0095] Preparation of carbon-coated sodium iron pyrophosphate A3:

[0096] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.78:1.28:0.4, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and obtain carbon-coated sodium iron pyrophosphate A3 (Na 1.56 Fe 1.22 P2O7@C);

[0097] Preparation of positive electrode material M5:

[0098] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A3 was added and stirred for 60 minutes 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 an 80°C forced air drying oven and dried for 3 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tubular furnace. The temperature was raised to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M5 was obtained.

[0099] Example 6

[0100] Preparation of carbon-coated sodium iron pyrophosphate A4:

[0101] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.78:1.32:0.78, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and mainly obtain carbon-coated sodium iron pyrophosphate A4 (Na 1.56 Fe 1.22 P2O7@C);

[0102] Preparation of positive electrode material M6:

[0103] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A4 was added and stirred for 60 minutes to obtain a mixed solution S6, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A4 to copper in the copper source was 100:1. The mixed solution S6 was placed in an 80°C forced air drying oven and dried for 3 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tubular furnace. The temperature was raised to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M6 was obtained.

[0104] Example 7

[0105] Preparation of carbon-coated sodium iron pyrophosphate A5:

[0106] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.82:1.28:0.78, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and mainly obtain carbon-coated sodium iron pyrophosphate A5 (Na 1.56 Fe 1.22 P2O7@C);

[0107] Preparation of positive electrode material M7:

[0108] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A5 was added and stirred for 60 minutes to obtain a mixed solution S7, wherein the weight ratio of carbon-coated sodium iron pyrophosphate A5 to copper in the copper source was 100:1. The mixed solution S7 was placed in a blast drying oven at 80°C and dried for 3 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tube furnace. The temperature was raised to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M7 was obtained.

[0109] Example 8

[0110] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0111] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.78:1.28:0.78, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and obtain carbon-coated sodium iron pyrophosphate A1 (Na 1.56 Fe 1.22 P2O7@C);

[0112] Preparation of positive electrode material M8:

[0113] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A1 was added and stirred for 60 minutes to obtain a mixed solution S8, wherein the weight ratio of carbon-coated sodium iron pyrophosphate 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 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tube furnace. The temperature was raised to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M8 was obtained.

[0114] Example 9

[0115] Preparation of carbon-coated sodium iron phosphate A6:

[0116] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.5:1:0.4, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and obtain carbon-coated sodium iron phosphate A6 (Na2Fe(PO4)2@C) after grinding;

[0117] Preparation of positive electrode material M9:

[0118] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron phosphate A6 was added and stirred for 60 minutes to obtain a mixed solution S9, wherein the weight ratio of carbon-coated sodium iron phosphate A6 to copper in the copper source was 100:1. The mixed solution S9 was placed in a forced air drying oven at 80°C and dried for 3 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tube furnace. The temperature was raised to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M9 was obtained.

[0119] Example 10

[0120] Preparation of carbon-coated sodium iron phosphate A6:

[0121] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.5:1:0.4, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and obtain carbon-coated sodium iron phosphate A6 (Na2Fe(PO4)2@C) after grinding;

[0122] Preparation of positive electrode material M10:

[0123] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron phosphate A6 was added and stirred for 60 minutes to obtain a mixed solution S10, wherein the weight ratio of carbon-coated sodium iron phosphate A6 to copper in the copper source was 100:0.3. The mixed solution S10 was placed in an 80°C forced air drying oven and dried for 3 hours. After drying, it was ground. The ground material was placed in a porcelain boat and placed in a tube furnace. The temperature was increased to 500°C at 5°C / min under a flowing argon atmosphere and calcined for 5 hours. After grinding, the positive electrode material M10 was obtained.

[0124] Example 11

[0125] Preparation of carbon-coated sodium iron pyrophosphate A7:

[0126] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.78:1.28:0.78, then, place the obtained gel in a vacuum drying oven at 100°C and dry for 2h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 500°C at 5°C / min under a flowing argon atmosphere and calcine for 15h, and obtain carbon-coated sodium iron pyrophosphate A7(Na 1.56 Fe 1.22 P2O7@C);

[0127] Preparation of positive electrode material M11:

[0128] A copper source Cu(NO3)2·3H2O was added to 5 ml of anhydrous ethanol, and then carbon-coated sodium iron pyrophosphate A7 was added and stirred for 60 minutes 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 90°C forced air drying oven and dried for 2 hours. After drying, it 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 5°C / min under a flowing argon atmosphere and calcined for 4 hours. After grinding, the positive electrode material M11 was obtained.

[0129] Comparative Example 1

[0130] Preparation of carbon-coated sodium iron pyrophosphate A1:

[0131] Add iron source Fe(NO3)3·9H2O to 30ml of deionized water, stir evenly at 85°C, add carbon source C6H8O6 and stir to form a transparent solution, then add sodium source CH3COONa and phosphorus source H3PO4 and stir to react for 1h until the deionized water evaporates 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 is 1:0.78:1.28:0.78, then, place the obtained gel in a vacuum drying oven at 110°C and dry for 1h, grind after drying, place the ground material in a porcelain boat and put it into a tube furnace, heat to 600°C at 5°C / min under a flowing argon atmosphere and calcine for 10h, and obtain carbon-coated sodium iron pyrophosphate A1 (Na 1.56 Fe 1.22 P2O7@C).

[0132] Comparative Example 2

[0133] The method of Example 1 was followed, except that, in the process of preparing the positive electrode material, copper oxide powder was used to replace the copper source Cu(NO 3 ) 2 ·3H 2 O.

[0134] Test Case

[0135] (1) The positive electrode materials prepared in the examples and comparative examples were characterized. FIG1 is an XRD pattern of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1; FIG2 is an XRD magnified pattern of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1; FIG3 is a TG curve diagram of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1; FIG4 is an electron microscope diagram of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1, wherein FIG4(a) is an electron microscope diagram of the positive electrode material prepared in Example 1, FIG4(b) is an electron microscope diagram of the positive electrode material prepared in Example 2, FIG4(c) is an electron microscope diagram of the positive electrode material prepared in Example 3, and FIG4(d) is an electron microscope diagram of the positive electrode material prepared in Comparative Example 1; FIG5 is an EDS diagram of the positive electrode materials prepared in Examples 1-3, wherein FIG5(a) is an EDS diagram of the positive electrode material prepared in Example 1, FIG5(b) is an EDS diagram of the positive electrode material prepared in Example 2, and FIG5(c) is an EDS diagram of the positive electrode material prepared in Example 3;

[0136] As shown in Figure 1, the XRD diffraction peaks are consistent with the JCPDS data (PDF#01-086-4091), the lattice structure is the P-1 type space group of the triclinic system, and the prepared positive electrode materials have no obvious impurity peaks, indicating that sodium iron pyrophosphate was synthesized in the preparation process;

[0137] As shown in Figure 2, the characteristic peaks of Examples 1-3 at 10.7° and 16.7° are all shifted to the left, indicating that Cu 2+ Successfully occupied Fe 2+ , doped into sodium iron pyrophosphate;

[0138] As shown in FIG3 , the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 have good thermal stability below 380° C., carbon begins to decompose above 380° C., and the thermal stability remains good after carbon decomposition is complete above 450° C. In addition, the average carbon content of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 is approximately 4.0 wt %.

[0139] As shown in FIG4 , the average particle size of the positive electrode material prepared in Comparative Example 1 is about 1000 nm, and the particles are small but uniform. The average particle size of the positive electrode materials prepared in Examples 1-3 is about 2000 nm, and the particle size is relatively uniform. In addition, it can be seen from the comparison that the appearance morphology of Examples 1-3 changes after the addition of the copper source compared with Comparative Example 1.

[0140] The EDS photograph of the positive electrode material prepared in Example 1-3 is shown in FIG5 . As can be seen from FIG5 , the surface of the positive electrode material in Example 1-3 has evenly distributed particles, indicating that the elemental copper in the positive electrode material prepared in Example 1-3 is evenly distributed on the surface of the positive electrode material. This indicates that under the method described in the present invention, the copper source becomes CuO and is evenly wrapped on the surface of the material.

[0141] (2) Thermogravimetric analysis (TG) of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 was performed using the following test method: 8 mg of the prepared positive electrode material was subjected to a thermogravimetric analysis test in an oxygen atmosphere at a heating rate of 5°C / min to determine the thermal stability and carbon content of the positive electrode material. The test results of the carbon content of the positive electrode material are shown in Table 1.

[0142] 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.

[0143] Table 1

[0144] It can be seen from the data in Table 1 that the positive electrode materials prepared in Examples 1-3 have different amounts of added copper sources, and the final weight content of the copper element basically matches the weight of the copper ions in the copper sources added in each of Examples 1-3. This also shows that the copper ions in the added copper source all participate in the reaction, while in Comparative Example 1, since no copper source is added, the positive electrode material finally prepared does not contain copper.

[0145] (3) The electrochemical properties of the positive electrode materials prepared in Examples 1-11 and Comparative Examples 1-2 were tested according to the following method:

[0146] (a) The positive electrode materials prepared in Examples 1-11 and Comparative Examples 1-2, the conductive agent (carbon black), and PVDF were added to the solvent (NMP) in a weight ratio of 8:1:1, and then stirred in a vacuum mixer to form a stable and uniform battery slurry. The above positive electrode slurry was coated on the current collector (aluminum foil) and dried at 105°C for 6 hours to obtain a positive electrode sheet;

[0147] (b) Cutting a sodium metal sheet of appropriate size to serve as the negative electrode;

[0148] (c) dissolving 1 mol of sodium salt -NaPF6 in 1 L of organic solvent (the volume ratio of propylene carbonate and fluoroethylene carbonate is 100:6) to obtain an electrolyte;

[0149] (d) In a glove box, under an argon atmosphere, alternately stacking the positive electrode sheet prepared in step (a), the separator-glass fiber separator, and the negative electrode sheet prepared in step (b), and injecting the electrolyte prepared in step (c) to prepare a CR2032 button battery;

[0150] (e) The button cells were allowed to stand at 25°C for 12 hours and tested on a Land-2001A battery testing system. Each battery was subjected to a charge-discharge cycle test and a rate performance test at 25°C with a current rate of 1C and a voltage range of 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 first cycle discharge capacity was equal to the ratio of the first cycle discharge capacity of the button cell to the weight of the positive electrode material in the cell. The battery capacity after 50 cycles was recorded. The capacity retention rate and the first cycle discharge specific capacity of the battery at 0.1C and 5C rates are shown in Table 2. FIG6 is a 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; FIG7 is a cycle performance graph of the battery prepared with the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 at 1C; FIG8 is a discharge specific capacity test graph of the battery prepared with the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 at 0.1C, 0.2C, 0.5C, 1C, 2C and 5C rates;

[0151] As shown in Figure 6, the batteries prepared with the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 have three charge and discharge platforms at around 2.5V, 3.0V and 3.3V when charged and discharged at 0.1C, which indicates that the Na + The intercalation and deintercalation is a single-phase reaction.

[0152] As shown in Figure 7, the discharge specific capacities of Example 1, Example 2 and Example 3 after 50 cycles at a rate of 1C 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. The discharge specific capacities of Comparative Example 1 after 50 cycles at a rate of 1C are 74.4 mAh / g, and the battery capacity retention rate is 99.2%, respectively. This shows that the batteries prepared using the positive electrode materials prepared in Examples 1-3 have excellent cycle performance.

[0153] As shown in Figure 8, at rates of 0.1C, 0.2C, 0.5C, 1C, 2C and 5C, the discharge specific capacities of Example 1 are 91.7, 88.3, ​​84.8, 81.6, 77.8 and 71.0 mAh / g, respectively. The discharge specific capacities of Example 1, Example 2 and Example 3 at a 5C rate are 71.03%, 63.3% and 67.5% of that at a 0.1C rate, while the discharge specific capacity of Comparative Example 1 at a 5C rate is 62.2% of that at a 0.1C rate, which indicates that the batteries prepared using the positive electrode materials prepared in Examples 1-3 have good high-rate performance.

[0154] Table 2

[0155] It can be seen from the data in Table 2 that the positive electrode material described in the present invention has good electrochemical performance, and the battery prepared using the positive electrode material described in the present invention has good cycle stability and high rate performance, among which the battery prepared using the positive electrode material prepared in Example 1 has significantly better effect.

[0156] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A cathode material, characterized in that, The positive electrode material has a core-shell structure, and the core part includes Cu coated with carbon 2+ doped iron-based phosphate sodium ion material, and the shell layer is CuO; The iron-based sodium phosphate sodium ion material is selected from at least one of sodium iron pyrophosphate, sodium iron phosphate, and sodium iron pyrophosphate phosphate.

2. The cathode 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 1-8 wt%, and the CuO content in the positive electrode material is 0.5-2.5 wt%.

3. A method for preparing a cathode material, characterized in that, The method includes: mixing a carbon-coated iron-based sodium phosphate sodium ion material, a copper source, and a first solvent, and then performing first drying and first calcination.

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

5. The method according to claim 4, 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 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 time is 0.5-8 h; The conditions for the second drying include: temperature 90-115 °C, time 0.5-8 h; The conditions for the second calcination include: temperature 450-600 °C, time 8-15 h.

7. The method according to claim 3, characterized in that, The weight ratio of the carbon-coated iron-based sodium phosphate sodium ion material to 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 conditions for the first drying include: temperature 80-100 °C, time 0.5-8 h; The conditions for the first calcination include: temperature 450-600 °C, time 2-10 h.

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

10. A battery paste, 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 1-2 and 9.

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

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

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