Metal phosphide coated sodium ferromanganese pyrophosphate positive electrode material and preparation method thereof

Abstract

The invention discloses a metal phosphide coated sodium ferromanganese pyrophosphate positive electrode material and a preparation method thereof.The positive electrode material is of a core-shell structure, comprises a core material and a coating shell layer, and is characterized in that the chemical general formula of the core material is NaaMn3-bFebP4O15 at phosphate, a is larger than or equal to 4.0 and smaller than or equal to 4.1, and b is larger than 0 and smaller than or equal to 1.5; and the coating shell layer is a metal phosphide ion conductor layer. The metal phosphide coated sodium ferromanganese pyrophosphate positive electrode material and the preparation method thereof have the characteristics of good electrolyte wettability, high interface stability and high electronic conductivity.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a metal phosphide-coated sodium manganese phosphate ferric phosphate cathode material and its preparation method. Background Technology

[0002] Sodium-ion batteries, with their abundant sodium resources and low raw material costs, are widely regarded as an important supplement and alternative to lithium-ion batteries in next-generation large-scale energy storage systems. Among the many sodium-ion battery cathode materials, sodium manganese iron pyrophosphate has become one of the current hot research materials due to its high operating voltage (>3.2 V vs. Na⁺ / Na), stable three-dimensional framework structure, and environmental friendliness.

[0003] However, this material still faces multiple challenges in its actual industrialization and long-term application:

[0004] First, manganese ions (especially trivalent Mn³⁺) in the material trigger typical Jahn-Teller distortion during charging and discharging, causing local distortion of the octahedral structure, which not only accelerates the dissolution of manganese ions but also destroys the overall stability of the crystal.

[0005] Secondly, under high-voltage operating conditions, catalytic side reactions are prone to occur between the material surface and the organic electrolyte, leading to continuous thickening of the interfacial film, increased impedance, and irreversible capacity loss.

[0006] Among commonly used material modification strategies, carbon coating can improve electron conductivity to some extent, but its effect on suppressing Mn³⁺ dissolution and high-pressure interfacial side reactions is limited. Some studies have attempted to use metal oxides as protective layers, which can enhance interfacial chemical stability, but these coating layers themselves have poor sodium ion conductivity, often sacrificing the material's fast-charging performance and rate capacity while improving cycle stability. Summary of the Invention

[0007] The purpose of this invention is to provide a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material and its preparation method, which has the characteristics of good electrolyte wettability, high interface stability and high electronic conductivity.

[0008] This invention can be achieved through the following technical solutions:

[0009] This invention relates to a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material. This cathode material has a core-shell structure, comprising a core material and a coating shell. The core material has the general chemical formula Na. a Mn 3-b Fe b P4O 15@Phosphate, where 4.0 ≤ a ≤ 4.1 and 0 < b ≤ 1.5; the coating layer is a metal phosphide ion conductor layer.

[0010] Furthermore, the metal phosphide ion conductor layer is an amorphous metal phosphide, which is one or more of zirconium phosphide (TiP), titanium phosphide (ZrP), nickel phosphide (Ni2P), cobalt phosphide (CoP), iron phosphide (FeP), and tin phosphide (Sn4P3).

[0011] Furthermore, the thickness of the metal phosphide ion conductor layer is 1-10 nm, and its mass is 0.1-3 wt% of the cathode material; this thickness range ensures the formation of a continuous and effective protective layer without excessively hindering sodium ion transport.

[0012] Another aspect of the present invention relates to a method for preparing the above-mentioned metal phosphide-coated sodium manganese phosphate ferric phosphate cathode material, the method comprising the following steps:

[0013] S1. Preparation of precursor solution: Dissolve sodium source, manganese source, iron source, core phosphorus source and carbon source in deionized water according to stoichiometric ratio to form a homogeneous precursor solution;

[0014] S2. Drying of precursor powder: The above precursor solution is spray-dried to achieve solid-liquid separation and obtain dry precursor powder.

[0015] S3. Single-stage step sintering: Under a protective atmosphere, the precursor powder is calcined in stages, and after natural cooling, the core Na is obtained. a Mn 3-b Fe b P4O 15 Material;

[0016] S4, Surface Coating: Coating the core Na... a Mn 3-b Fe b P4O 15 The material, the coated metal source, and the coated phosphorus source are mixed with water and reacted under stirring, so that the metal phosphide is uniformly adsorbed and deposited on the surface of the core material to form a uniformly coated precursor material.

[0017] S5 Secondary Calcination: Under a protective atmosphere, the above-mentioned precursor materials are calcined at high temperature, so that the amorphous metal phosphide coating layer is firmly attached to the core surface. Natural cooling yields the final Na. a Mn 3-b Fe b P4O 15 @Phosphate materials.

[0018] Furthermore, in step S3, the sintering process is a staged sintering process, including a first stage and a second stage: in the first stage, the temperature is raised to 300-400℃ and held for >0.1H to fully remove crystal water and volatile atmosphere; in the second stage, the temperature is raised to 550-700℃ and held for >0.1H to allow the material to fully nucleate and crystallize to obtain the core material; the protective atmosphere is nitrogen, argon, or a nitrogen-hydrogen / argon-hydrogen mixture, all of which are non-oxygen-containing atmospheres.

[0019] Furthermore, in step S5, the secondary sintering temperature is 350-550℃, and the holding time is >0.1H; within this temperature range, the metal source and phosphorus source adsorbed on the material surface decompose and bond to form a uniform and dense metal phosphide ion conductor layer.

[0020] Further, in step S1, the sodium source is one or more of sodium formate, sodium acetate, sodium oxalate, sodium citrate, sodium nitrate, sodium carbonate, sodium bicarbonate, and sodium hydroxide.

[0021] Furthermore, the manganese source is one or more of manganese nitrate, manganese sulfate, manganese acetate, manganese citrate, and manganese gluconate.

[0022] Furthermore, the iron source is one or more of ferrous sulfate, ferric sulfate, ferrous chloride, ferric oxide, ferric acetate, ferrous ammonium sulfate, and ferric citrate.

[0023] Furthermore, the core phosphorus source is one or more of the following: phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate.

[0024] Further, in step S1, the carbon source is one or more of the following: citric acid, glucose, sucrose, maltose, soluble starch, graphene and its derivatives, carbon nanotubes and their derivatives, and carbon black and its derivatives.

[0025] Further, in step S4, the coating metal source is one or more of zirconium source, titanium source, nickel source, cobalt source, iron source, and tin source; the zirconium source is one or more of zirconium oxychloride, zirconium sulfate, zirconium acetate, ammonium zirconium carbonate, and zirconium citrate; the titanium source is one or more of titanium oxysulfate, tetrabutyl carbonate, tetraethyl titanate, and tetraisopropyl titanate; the nickel source is one or more of nickel sulfate, nickel nitrate, and nickel acetate; the cobalt source is one or more of cobalt sulfate, cobalt nitrate, and cobalt acetate; the iron source is one or more of ferric sulfate, ferric nitrate, and ferric acetate; and the tin source is one or more of stannous sulfate, tributyltin chloride, and dibutyltin dilaurate.

[0026] Furthermore, in step S4, the coated phosphoric acid is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate; the coated phosphorus source has no alkali metal cation residue after thermal decomposition and can combine with the metal source to form an ion conductor layer.

[0027] This invention discloses a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material and its preparation method, which has the following beneficial effects:

[0028] First, the electrolyte wettability is excellent. Regarding the formation of the core material, the spray drying-step sintering method employed in this invention achieves atomic-level uniform mixing, resulting in microspheres with uniform particle size distribution, high specific surface area, and abundant pore structure, which is beneficial for electrolyte wettability and sodium ion transport. The in-situ introduced carbon network significantly improves the material's electronic conductivity. The step sintering strategy effectively prevents sodium volatilization and the formation of impurity phases.

[0029] Secondly, it exhibits high interfacial stability through the coating of the core material. The amorphous metal phosphide layer acts as a robust physical barrier, effectively isolating the core material from direct contact with the electrolyte and significantly inhibiting the dissolution of manganese / iron ions and interfacial side reactions.

[0030] Third, it has high electronic conductivity. The metal phosphide layer itself has good ionic conductivity. Its structure and the core material are both phosphorus-oxygen tetrahedra, which have excellent interfacial compatibility. It can provide a low-resistance fast channel for the insertion / extraction of sodium ions, achieving "protection without blocking".

[0031] Fourth, the synthesis process is simple and easy to implement. This invention organically combines core synthesis with surface modification, providing a complete technical route for the large-scale preparation of high-performance cathode materials. The final product shows significant advantages in cycle life and rate performance. Attached Figure Description

[0032] Figure 1 For the application of Na in Example 1 4.05 Mn 1.5 Fe 1.5 P4O 15 TEM image of the TiP material interface;

[0033] Figure 2 For Na in Comparative Example 1 4.05 Mn 1.5 Fe 1.5 P4O 15 TEM image of the material interface. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention will be further described in detail below with reference to embodiments.

[0035] This invention relates to a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material. This cathode material has a core-shell structure, comprising a core material and a coating shell. The core material has the general chemical formula Na. a Mn 3-b Fe b P4O 15 @Phosphate, where 4.0 ≤ a ≤ 4.1 and 0 < b ≤ 1.5; the coating layer is a metal phosphide ion conductor layer.

[0036] Furthermore, the metal phosphide ion conductor layer is an amorphous metal phosphide, which is one or more of zirconium phosphide (TiP), titanium phosphide (ZrP), nickel phosphide (Ni2P), cobalt phosphide (CoP), iron phosphide (FeP), and tin phosphide (Sn4P3).

[0037] Furthermore, the thickness of the metal phosphide ion conductor layer is 1-10 nm, and its mass is 0.1-3 wt% of the cathode material.

[0038] Another aspect of the present invention relates to a method for preparing the above-mentioned metal phosphide-coated sodium manganese phosphate ferric phosphate cathode material, the method comprising the following steps:

[0039] S1. Preparation of precursor solution: Dissolve sodium source, manganese source, iron source, core phosphorus source and carbon source in deionized water according to stoichiometric ratio to form a homogeneous precursor solution;

[0040] S2. Drying of precursor powder: The above precursor solution is spray-dried to achieve solid-liquid separation and obtain dry precursor powder.

[0041] S3. Single-stage step sintering: Under a protective atmosphere, the precursor powder is calcined in stages, and after natural cooling, the core Na is obtained. a Mn 3-b Fe b P4O 15 Material;

[0042] S4, Surface Coating: Coating the core Na... a Mn 3-b Fe b P4O 15 The material, the coated metal source, and the coated phosphorus source are mixed with water and reacted under stirring, so that the metal phosphide is uniformly adsorbed and deposited on the surface of the core material to form a uniformly coated precursor material.

[0043] S5 Secondary Calcination: Under a protective atmosphere, the above-mentioned precursor materials are calcined at high temperature, and then naturally cooled to obtain the final Na. a Mn 3-b Feb P4O 15 @Phosphate materials.

[0044] Furthermore, in step S3, the sintering process is a staged sintering process, including a first stage and a second stage: in the first stage, the temperature is raised to 300-400℃ and held for >0.1H; in the second stage, the temperature is raised to 550-700℃ and held for >0.1H; the protective atmosphere is nitrogen, argon, or a nitrogen-hydrogen / argon-hydrogen mixture.

[0045] Furthermore, in step S5, the secondary sintering temperature is 350-550℃, and the holding time is >0.1H.

[0046] Further, in step S1, the sodium source is one or more of sodium formate, sodium acetate, sodium oxalate, sodium citrate, sodium nitrate, sodium carbonate, sodium bicarbonate, and sodium hydroxide.

[0047] Furthermore, the manganese source is one or more of manganese nitrate, manganese sulfate, manganese acetate, manganese citrate, and manganese gluconate.

[0048] Furthermore, the iron source is one or more of ferrous sulfate, ferric sulfate, ferrous chloride, ferric oxide, ferric acetate, ferrous ammonium sulfate, and ferric citrate.

[0049] Furthermore, the core phosphorus source is one or more of the following: phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate.

[0050] Further, in step S1, the carbon source is one or more of the following: citric acid, glucose, sucrose, maltose, soluble starch, graphene and its derivatives, carbon nanotubes and their derivatives, and carbon black and its derivatives.

[0051] Further, in step S4, the coating metal source is one or more of zirconium source, titanium source, nickel source, cobalt source, iron source, and tin source; the zirconium source is one or more of zirconium oxychloride, zirconium sulfate, zirconium acetate, ammonium zirconium carbonate, and zirconium citrate; the titanium source is one or more of titanium oxysulfate, tetrabutyl carbonate, tetraethyl titanate, and tetraisopropyl titanate; the nickel source is one or more of nickel sulfate, nickel nitrate, and nickel acetate; the cobalt source is one or more of cobalt sulfate, cobalt nitrate, and cobalt acetate; the iron source is one or more of ferric sulfate, ferric nitrate, and ferric acetate; and the tin source is one or more of stannous sulfate, tributyltin chloride, and dibutyltin dilaurate.

[0052] Furthermore, in step S4, the coated phosphoric acid is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate.

[0053] Example 1

[0054] This embodiment relates to a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material. This cathode material has a core-shell structure, comprising a core material and a coating layer. The core material has the general chemical formula Na. a Mn 3-b Fe b P4O 15 @Phosphate, where 4.0 ≤ a ≤ 4.1, 0 < b ≤ 1.5; the coating layer is a metal phosphide ion conductor layer. Specifically, the metal phosphide ion conductor layer is an amorphous metal phosphide, and the metal phosphide is cobalt phosphide (CoP); the thickness of the metal phosphide ion conductor layer is 1-10 nm, and its mass is 0.5 wt% of the cathode material.

[0055] Example 2

[0056] This embodiment relates to a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material. This cathode material has a core-shell structure, comprising a core material and a coating layer. The core material has the general chemical formula Na. a Mn 3-b Fe b P4O 15 @Phosphate, where 4.0 ≤ a ≤ 4.1, 0 < b ≤ 1.5; the coating layer is a metal phosphide ion conductor layer. Specifically, the metal phosphide ion conductor layer is an amorphous metal phosphide, which is nickel phosphide (Ni2P); the thickness of the metal phosphide ion conductor layer is 1-10 nm, and its mass is 0.2 wt% of the cathode material.

[0057] Example 1

[0058] This embodiment relates to a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material. This cathode material has a core-shell structure, comprising a core material and a coating layer. The core material has the general chemical formula Na. a Mn 3-b Fe b P4O 15 @Phosphate, where 4.0 ≤ a ≤ 4.1, 0 < b ≤ 1.5; the coating layer is a metal phosphide ion conductor layer. Specifically, the metal phosphide ion conductor layer is an amorphous metal phosphide, which is cobalt phosphide (CoP), iron phosphide (FeP), or tin phosphide (Sn4P3); the thickness of the metal phosphide ion conductor layer is 1-10 nm, and its mass is 2 wt% of the cathode material.

[0059] Example 4

[0060] This embodiment relates to a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material. This cathode material has a core-shell structure, comprising a core material and a coating layer. The core material has the general chemical formula Na. a Mn 3-b Fe b P4O 15 @Phosphate, where 4.0 ≤ a ≤ 4.1, 0 < b ≤ 1.5; the coating layer is a metal phosphide ion conductor layer. Specifically, the metal phosphide ion conductor layer is an amorphous metal phosphide, which is zirconium phosphide (TiP) or titanium phosphide (ZrP); the thickness of the metal phosphide ion conductor layer is 1-10 nm, and its mass is 3 wt% of the cathode material.

[0061] Example 5

[0062] This embodiment relates to a method for preparing a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material, the preparation method comprising the following steps:

[0063] S1. Preparation of precursor solution: Dissolve sodium source, manganese source, iron source, core phosphorus source and carbon source in deionized water according to stoichiometric ratio to form a homogeneous precursor solution;

[0064] S2. Drying of precursor powder: The above precursor solution is spray-dried to achieve solid-liquid separation and obtain dry precursor powder.

[0065] S3. Single-stage step sintering: Under a protective atmosphere, the precursor powder is calcined in stages, and after natural cooling, the core Na is obtained. a Mn 3-b Fe b P4O 15 Materials; specifically, the sintering process is a staged sintering process, including a first stage and a second stage: the first stage is heated to 400℃ and held for 8 hours; the second stage is heated to 650℃ and held for 6 hours; the protective atmosphere is nitrogen.

[0066] S4, Surface Coating: Coating the core Na... a Mn 3-b Fe b P4O 15 The material, the coated metal source, and the coated phosphorus source are mixed with water and reacted under stirring, so that the metal phosphide is uniformly adsorbed and deposited on the surface of the core material to form a uniformly coated precursor material.

[0067] S5 Secondary Calcination: Under a protective atmosphere, the above-mentioned precursor materials are calcined at high temperature, and then naturally cooled to obtain the final Na. a Mn 3-b Fe b P4O 15@Phosphate materials; specifically, the secondary sintering temperature is 550℃, and the holding time is 7 hours.

[0068] In this embodiment, the sodium source is sodium formate or sodium acetate; the manganese source is manganese nitrate or manganese sulfate; the iron source is ferrous sulfate, ferric sulfate, ferrous chloride, or ferric oxide; the core phosphorus source is phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, or sodium phosphate. The carbon source is citric acid or glucose; the coating metal source is a zirconium source, specifically zirconium oxychloride, zirconium sulfate, zirconium acetate, ammonium zirconium carbonate, or zirconium citrate; and the coating phosphoric acid is phosphoric acid, ammonium dihydrogen phosphate, or diammonium hydrogen phosphate.

[0069] Example 6

[0070] This embodiment relates to a method for preparing a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material, the preparation method comprising the following steps:

[0071] S1. Preparation of precursor solution: Dissolve sodium source, manganese source, iron source, core phosphorus source and carbon source in deionized water according to stoichiometric ratio to form a homogeneous precursor solution;

[0072] S2. Drying of precursor powder: The above precursor solution is spray-dried to achieve solid-liquid separation and obtain dry precursor powder.

[0073] S3. Single-stage step sintering: Under a protective atmosphere, the precursor powder is calcined in stages, and after natural cooling, the core Na is obtained. a Mn 3-b Fe b P4O 15 Materials; specifically, the sintering process is a staged sintering process, including a first stage and a second stage: the first stage is heated to 350℃ and held for 10 hours; the second stage is heated to 550℃ and held for 5 hours; the protective atmosphere is argon.

[0074] S4, Surface Coating: Coating the core Na... a Mn 3-b Fe b P4O 15 The material, the coated metal source, and the coated phosphorus source are mixed with water and reacted under stirring, so that the metal phosphide is uniformly adsorbed and deposited on the surface of the core material to form a uniformly coated precursor material.

[0075] S5 Secondary Calcination: Under a protective atmosphere, the above-mentioned precursor materials are calcined at high temperature, and then naturally cooled to obtain the final Na. a Mn 3-b Fe b P4O 15 @Phosphate materials; specifically, the secondary sintering temperature is 450℃, and the holding time is 6 hours.

[0076] In this embodiment, the sodium source is sodium citrate or sodium hydroxide; the manganese source is manganese nitrate, manganese citrate, or manganese gluconate; the iron source is ferrous ammonium sulfate or ferric citrate; and the core phosphorus source is diammonium hydrogen phosphate or ammonium phosphate. The carbon source is maltose, carbon nanotubes and their derivatives, or carbon black and its derivatives; the coating metal source is a titanium source, specifically titanium oxysulfate, tetrabutyl carbonate, tetraethyl titanate, or tetraisopropyl titanate; and the coating phosphoric acid is diammonium hydrogen phosphate or ammonium phosphate.

[0077] Example 7

[0078] This embodiment relates to a method for preparing a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material, the preparation method comprising the following steps:

[0079] S1. Preparation of precursor solution: Dissolve sodium source, manganese source, iron source, core phosphorus source and carbon source in deionized water according to stoichiometric ratio to form a homogeneous precursor solution;

[0080] S2. Drying of precursor powder: The above precursor solution is spray-dried to achieve solid-liquid separation and obtain dry precursor powder.

[0081] S3. Single-stage step sintering: Under a protective atmosphere, the precursor powder is calcined in stages, and after natural cooling, the core Na is obtained. a Mn 3-b Fe b P4O 15 Materials; specifically, the sintering process is a staged sintering process, including a first stage and a second stage: the first stage is heated to 300℃ and held for 10 hours; the second stage is heated to 700℃ and held for 6 hours; the protective atmosphere is a nitrogen-hydrogen / argon-hydrogen mixture.

[0082] S4, Surface Coating: Coating the core Na... a Mn 3-b Fe b P4O 15 The material, the coated metal source, and the coated phosphorus source are mixed with water and reacted under stirring, so that the metal phosphide is uniformly adsorbed and deposited on the surface of the core material to form a uniformly coated precursor material.

[0083] S5 Secondary Calcination: Under a protective atmosphere, the above-mentioned precursor materials are calcined at high temperature, and then naturally cooled to obtain the final Na. a Mn 3-b Fe b P4O 15 @Phosphate materials; specifically, the secondary sintering temperature is 350℃, and the holding time is 8 hours.

[0084] In this embodiment, the sodium source is sodium citrate, sodium nitrate, sodium carbonate, or sodium bicarbonate; the manganese source is manganese acetate, manganese citrate, or manganese gluconate; the iron source is ferrous chloride, iron oxide, or ferric acetate; the core phosphorus source is phosphoric acid, disodium hydrogen phosphate, or ammonium phosphate. The carbon source is soluble starch, graphene and its derivatives, or carbon nanotubes and their derivatives; the coating metal source is a nickel source, specifically nickel sulfate or nickel nitrate; and the coating phosphoric acid is phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, or ammonium phosphate.

[0085] Example 8

[0086] This embodiment relates to a method for preparing a metal phosphide-coated sodium manganese phosphate pyrophosphate cathode material, the preparation method comprising the following steps:

[0087] S1. Preparation of precursor solution: Dissolve sodium source, manganese source, iron source, core phosphorus source and carbon source in deionized water according to stoichiometric ratio to form a homogeneous precursor solution;

[0088] S2. Drying of precursor powder: The above precursor solution is spray-dried to achieve solid-liquid separation and obtain dry precursor powder.

[0089] S3. Single-stage step sintering: Under a protective atmosphere, the precursor powder is calcined in stages, and after natural cooling, the core Na is obtained. a Mn 3-b Fe b P4O 15 Materials; specifically, the sintering process is a staged sintering process, including a first stage and a second stage: the first stage is heated to 320℃ and held for 5 hours; the second stage is heated to 600℃ and held for 8 hours; the protective atmosphere is nitrogen.

[0090] S4, Surface Coating: Coating the core Na... a Mn 3-b Fe b P4O 15 The material, the coated metal source, and the coated phosphorus source are mixed with water and reacted under stirring, so that the metal phosphide is uniformly adsorbed and deposited on the surface of the core material to form a uniformly coated precursor material.

[0091] S5 Secondary Calcination: Under a protective atmosphere, the above-mentioned precursor materials are calcined at high temperature, and then naturally cooled to obtain the final Na. a Mn 3-b Fe b P4O 15 @Phosphate materials; specifically, the secondary sintering temperature is 400℃, and the holding time is 6 hours.

[0092] In this embodiment, the sodium source is sodium formate, sodium acetate, or sodium oxalate; the manganese source is manganese gluconate; the iron source is ferrous ammonium sulfate or ferric citrate; the core phosphorus source is ammonium dihydrogen phosphate, diammonium hydrogen phosphate, or ammonium phosphate. The carbon source is graphene and its derivatives, carbon nanotubes and their derivatives, or carbon black and its derivatives; the coating metal source is cobalt or iron, with the cobalt source being cobalt sulfate, cobalt nitrate, or cobalt acetate, and the iron source being ferric sulfate, ferric nitrate, or ferric acetate; the coating phosphoric acid is phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, or ammonium phosphate.

[0093] Application Example 1 Na 4.05 Mn 1.5 Fe 1.5 P4O 15 Synthesis and Electrochemical Properties of TiP Materials

[0094] This embodiment involves Na 4.05 Mn 1.5 Fe 1.5 P4O 15 The preparation method of @TiP material includes the following steps:

[0095] S1. Preparation of precursor solution: According to Na... 4.05 Mn 1.5 Fe 1.5 P4O 15 The stoichiometric ratio in the molecular formula is as follows: sodium acetate, manganese sulfate, ferrous sulfate, phosphoric acid, and glucose (added at 5 wt% of the total solid content of the solution) are dissolved in deionized water in a molar ratio of 4.05:1.5:1.5:4.0 to form a homogeneous precursor solution.

[0096] S2. Drying of precursor powder: The above precursor solution is spray-dried with an inlet air temperature of 300°C and an outlet air temperature of 100°C to achieve solid-liquid separation and obtain dry precursor powder.

[0097] S3. Single-step sintering: In a nitrogen atmosphere, the temperature is raised to 350℃ and held for 5 hours to remove water of crystallization and volatile atmosphere; then the temperature is raised to 600℃ and held for 10 hours to allow the material to fully nucleate and crystallize, yielding Na. 4.05 Mn 1.5 Fe 1.5 P4O 15 Core materials;

[0098] S4, Surface Coating: Coating the core Na... a Mn 3-b Fe b P4O 15 Materials, titanium oxysulfate, and ammonium dihydrogen phosphate are mixed with water, wherein the molar ratio of titanium oxysulfate to ammonium dihydrogen phosphate is 1:1, and the mass of the core Na is... a Mn3-b Fe b P4O 15 0.8 wt% of the material weight is reacted under stirring to allow the metal phosphide to be uniformly adsorbed and deposited on the surface of the core material, forming a uniformly coated precursor material;

[0099] S5. Secondary calcination: Under a nitrogen atmosphere, the above precursor materials are calcined at 400°C to firmly adhere the amorphous metal phosphide coating layer to the core surface. Natural cooling yields Na. 4.05 Mn 1.5 Fe 1.5 P4O 15 @TiP materials.

[0100] Figure 1 for Na 4.05 Mn 1.5 Fe 1.5 P4O 15 TEM images of the TiP material show a dense, uniform TiP coating layer with a thickness of approximately 2–5 nanometers at the interface. This coating layer acts as a highly efficient physical barrier, effectively blocking corrosive components of the electrolyte and inhibiting the dissolution of the core active material, thereby significantly improving the structural integrity and chemical stability of the material during long-term cycling.

[0101] Will Na 4.05 Mn 1.5 Fe 1.5 P4O 15 @TiP material, SurP PVDF5130 is produced in a mass ratio of 9.3:0.4:0.3. For example, NMP is added and mixed, and the above materials are mixed evenly using a high-speed homogenizer to form a black paste with uniform color and high fluidity. Material, of The black paste was then coated onto aluminum foil using a 150µm four-sided coating apparatus, and the membrane was dried in a vacuum drying oven at 100℃ for 2 hours. The electrode membrane was punched into a disc with a radius of 0.6mm using a punching machine. Sodium metal was used as the counter electrode, and 1mol / L NaClO4EC+DEC (1:1 vol%)+5% FEC was used as the electrolyte. The separator was a PP / PE / PP three-layer separator. The membrane was assembled into a CR2016 button cell in a glove box.

[0102] Table 1 shows the electrochemical performance test results for Na. 4.05 Mn 1.5 Fe 1.5 P4O 15 The TiP electrode exhibits a discharge specific capacity of 128.6 mAh / g at a rate of 0.1C (1C = 129 mAh / g), slightly higher than the material in the comparative example. This may be related to the Na+ content. 4.05 Mn 1.5 Fe 1.5 P4O 15The secondary sintering of @TiP provides additional energy and time, allowing atoms to continue diffusing and migrating, ultimately forming a more stable, ordered, and defect-free crystal structure. This structural optimization directly leads to improved electrochemical performance. Furthermore, Table 1 shows that at 10C, the capacity retention of this electrode is as high as 93.5% compared to 0.1C, significantly higher than the material in the comparative example. This is due to the secondary sintering process, which repairs crystal defects, promotes grain growth, reduces grain boundaries, improves crystal structure integrity, facilitates sodium ion diffusion, lowers diffusion barriers, and reduces grain boundary and electron scattering. This comprehensive improvement in solid-phase ion / electron transport dynamics allows the material to achieve efficient sodium ion insertion / extraction even at high rates, resulting in significantly enhanced rate performance. Finally, at 1C, after 1000, 2000, and 3000 cycles, the capacity retention of this electrode is 97.8%, 95.3%, and 92.6%, respectively, with less capacity decay than the comparative example. The performance improvement can be attributed to the multiple protective effects of the TiP coating: First, the coating effectively stabilizes the material's surface structure by suppressing Mn during cycling. 3+ The Jahn-Teller distortion fundamentally reduces the solubility tendency of manganese ions, preserving the structural integrity of the material. Secondly, as an inert interface layer, it significantly reduces parasitic reactions between active particles and the electrolyte (such as HF erosion and solvent oxidative decomposition), enhancing the chemical stability of the interface. It is this synergistic stabilizing effect of the bulk and interface that together endows the electrode with excellent long-cycle performance. Elemental analysis results of the battery's negative electrode show that Na... 4.05 Mn 1.5 Fe 1.5 P4O 15 After 3000 cycles, the manganese content of the TiP electrode was only 13 ppm, which is negligible and has little impact on the battery cycle performance. This indirectly proves that the presence of the TiP coating layer has a positive effect on Na+. 4.05 Mn 1.5 Fe 1.5 P4O 15 The core material provides good protection.

[0103] Application Example 2 Na 4.05 Mn 2.0 Fe 1.0 P4O 15 Synthesis and Electrochemical Properties of ZrP Materials

[0104] This embodiment involves Na 4.05 Mn 2.0 Fe 1.0 P4O 15 The preparation method of ZrP material includes the following steps:

[0105] S1. Preparation of precursor solution: According to Na... 4.05 Mn 2.0 Fe 1.0 P4O 15 The stoichiometric ratio in the molecular formula is as follows: sodium acetate, manganese sulfate, ferrous sulfate, phosphoric acid, and citric acid (added in an amount of 7 wt% of the total solid content of the solution) are dissolved in deionized water in a molar ratio of 4.05:2.0:1.0:4.0 to form a homogeneous solution.

[0106] S2. Drying of precursor powder: The above solution is spray-dried with an inlet air temperature of 320°C and an outlet air temperature of 110°C to achieve solid-liquid separation and obtain dry precursor powder.

[0107] S3. Single-step sintering: In a nitrogen atmosphere, the temperature is raised to 380℃ and held for 7 hours to remove water of crystallization and volatile atmosphere; then the temperature is raised to 620℃ and held for 10 hours to allow the material to fully nucleate and crystallize, yielding Na. 4.05 Mn 2.0 Fe 1.0 P4O 15 Core materials;

[0108] S4, Surface Coating: Coating the core Na... 4.05 Mn 2.0 Fe 1.0 P4O 15 Materials, zirconium acetate, and phosphoric acid are mixed with water, wherein the molar ratio of zirconium acetate to phosphoric acid is 1:1, and the mass of the core Na is [missing information]. 4.05 Mn 2.0 Fe 1.0 P4O 15 1.0 wt% of the material weight is reacted under stirring to allow the metal phosphide to be uniformly adsorbed and deposited on the surface of the core material, forming a uniformly coated precursor material;

[0109] S5. Secondary calcination: Under a nitrogen atmosphere, the above precursor materials are calcined at 500°C to firmly adhere the amorphous metal phosphide coating layer to the core surface. Natural cooling yields Na. 4.05 Mn 2.0 Fe 1.0 P4O 15 @ZrP material.

[0110] Will Na 4.05 Mn 2.0 Fe 1.0 P4O 15 @ZrP materials, SurP PVDF5130 is produced in a mass ratio of 9.3:0.4:0.3. For example, NMP is added and mixed, and the above materials are mixed evenly using a high-speed homogenizer to form a black paste with uniform color and high fluidity. Material, ofThe black paste was then coated onto aluminum foil using a 150µm four-sided coating apparatus, and the membrane was dried in a vacuum drying oven at 100℃ for 2 hours. The electrode membrane was punched into a disc with a radius of 0.6mm using a punching machine. Sodium metal was used as the counter electrode, and 1mol / L NaClO4EC+DEC (1:1 vol%)+5% FEC was used as the electrolyte. The separator was a PP / PE / PP three-layer separator. The membrane was assembled into a CR2016 button cell in a glove box.

[0111] Table 1 shows the electrochemical performance test results for Na. 4.05 Mn 2.0 Fe 1.0 P4O 15 The @ZrP electrode achieved a discharge specific capacity of 126.9 mAh / g at 0.1C (1C = 129 mAh / g), slightly higher than the untreated comparative material. This improvement can be attributed to the introduction of a secondary sintering process, which provides atoms with additional energy and migration time, promoting a more complete and ordered crystal structure and significantly reducing defect density, thereby optimizing the intrinsic electrochemical activity of the material. Furthermore, the electrode exhibited excellent kinetic performance at a high rate of 10C, with a capacity retention (relative to 0.1C) of 94.2%, superior to the comparative example. This is mainly due to the effective repair of internal crystal defects, increased grain size, and reduced number of grain boundaries after secondary sintering. The improved structural integrity facilitates a smoother sodium ion diffusion path, lowers the migration barrier, and reduces electron transport resistance, jointly promoting a synergistic enhancement of ion and electron transport kinetics in the solid phase. Therefore, even at extremely high rates, efficient sodium ion insertion / extraction can still be achieved, resulting in a significant improvement in rate performance. Regarding long-term cycling stability, after 1000, 2000, and 3000 cycles at 1C, the capacity retention of this electrode was 97.0%, 94.5%, and 91.2%, respectively, with a significantly lower rate of decay compared to the comparative example. This superior performance is attributed to the multiple protective mechanisms of the ZrP coating: on the one hand, the coating effectively suppresses the Jahn-Teller distortion of Mn³⁺ during cycling, reducing the risk of manganese ion dissolution from the structural source and maintaining the integrity of the material bulk; on the other hand, as a stable inert interface layer, it significantly reduces side reactions between the active material and the electrolyte, improving interfacial chemical stability. This synergistic effect of "bulk modification" and "interfacial protection" jointly ensures the long-term cycle life of the electrode. Furthermore, elemental analysis of the negative electrode after cycling showed that Na… 4.05 Mn 2.0 Fe 1.0 P4O 15The manganese content in the negative electrode corresponding to the @ZrP electrode is only 24 ppm, which is negligible and far lower than that in the comparison sample. This data further confirms that the ZrP coating layer has a significant protective effect on the core material, effectively inhibiting the migration and deposition of manganese, thereby ensuring the cycle stability of the full cell.

[0112] Comparative Example 1 Na 4.05 Mn 1.5 Fe 1.5 P4O 15 Synthesis and electrochemical properties of materials

[0113] This embodiment involves Na 4.05 Mn 1.5 Fe 1.5 P4O 15 The material, and its preparation method includes the following steps:

[0114] Step 1: Dissolve sodium acetate, manganese acetate, ferrous sulfate, and phosphoric acid in water at a molar ratio of 4.05:1.5:1.5:4. Add glucose (5 wt% of the total solid content) as a carbon source to form a transparent brownish-red precursor solution.

[0115] Step 2: Spray dry the above precursor solution with an inlet air temperature of 300°C and an outlet air temperature of 100°C to remove moisture from the slurry and obtain dried precursor powder.

[0116] Step 3: Calcine the above precursor powder at 600℃ for 10 hours, then allow it to cool naturally to obtain Na. 4.05 Mn 1.5 Fe 1.5 P4O 15 Material.

[0117] Figure 2 for Na 4.05 Mn 1.5 Fe 1.5 P4O 15 The TEM image of the material shows that its interface is relatively smooth with only a small amount of carbon layer. This means that the interface of the material will be in direct contact with the electrolyte. During the repeated sodium insertion and extraction process, the interface cracking caused by the material volume change will trigger a violent reaction between the electrolyte and the material, which will aggravate the dissolution of the material and be detrimental to the cycling stability of the material.

[0118] Will Na 4.05 Mn 1.5 Fe 1.5 P4O 15 Material SurP and PVDF5130 are added in a mass ratio of 9.4:0.3:0.3. NMP is mixed, and the above materials are mixed evenly using a high-speed homogenizer to form a black slurry with uniform color and high fluidity. OfThe black paste was then coated onto aluminum foil using a 150µm four-sided coating apparatus, and the membrane was dried in a vacuum drying oven at 100℃ for 2 hours. The electrode membrane was punched into a disc with a radius of 0.6mm using a punching machine. Sodium metal was used as the counter electrode, 1mol / L NaClO4EC+DEC (1:1 vol%)+5% FEC was used as the electrolyte, and a PP / PE / PP three-layer separator was used. The membrane was assembled into a CR2016 button cell in a glove box.

[0119] Table 1 shows the Na 4.05 Mn 1.5 Fe 1.5 P4O 15 The key electrochemical performance of the electrode. At a low rate of 0.1C (1C = 129 mAh / g), the discharge specific capacity of this electrode was only 123.4 mAh / g, lower than that of the application example. This is mainly attributed to the underoptimization of the single sintering process, resulting in uneven distribution of elements such as manganese and iron, introducing a large number of vacancies and defects into the material structure. These microstructural defects directly reduce the effective active sites available for electrochemical reactions, thus limiting the intrinsic capacity of the material. Furthermore, the negative impact of these structural defects is more pronounced at high rates. As shown in Table 1, at a rate of 10C, the capacity retention (relative to 0.1C) of this electrode was only 91.3%, inferior to the application example. This indicates that the defects in the structure not only limit the number of active sites but also severely hinder rapid charge transport: on the one hand, increasing the impedance of electron conduction; on the other hand, setting a higher energy barrier for sodium ions when crossing different crystal phase interfaces, leading to a decrease in ion migration rate. This kinetic lag ultimately leads to a significant deterioration in rate performance. Finally, the electrode exhibits poor long-cycle stability at 1C rate, with capacity retention rates of 93.6%, 85.3%, and 61.2% after 1000, 2000, and 3000 cycles, respectively, showing an accelerated degradation trend. The severe performance degradation stems primarily from two aspects: First, the continuous Jahn-Teller effect of Mn³⁺ in the material bulk induces lattice distortion and structural stress accumulation, ultimately leading to manganese dissolution and damage to the host structure. Second, under high-voltage conditions, the material surface exhibits catalytic activity towards the electrolyte, exacerbating the oxidative decomposition of the electrolyte and forming a thick and unstable interface layer. Elemental analysis of the negative electrode after cycling revealed a manganese deposition level as high as 3500 ppm. This not only directly demonstrates the severity of manganese dissolution from the positive electrode, but these dissolved manganese ions also migrate to the negative electrode, damaging the solid electrolyte interface film and exacerbating the irreversible consumption of active sodium. This creates a vicious cycle with the performance degradation of the positive electrode, jointly leading to the rapid decline in battery capacity.

[0120] Comparative Example 2 Na 4.05 Mn 2.0 Fe 1.0P4O 15 Synthesis and electrochemical properties of materials

[0121] This embodiment involves Na 4.05 Mn 2.0 Fe 1.0 P4O 15 The material, and its preparation method includes the following steps:

[0122] Step 1: Dissolve sodium acetate, manganese acetate, ferrous sulfate, and phosphoric acid in water at a molar ratio of 4.05:2.0:1.0:4. Use citric acid (7wt% of the total solid content) as a carbon source to form a transparent brownish-red precursor solution.

[0123] Step 2: Spray dry the above precursor solution with an inlet air temperature of 320°C and an outlet air temperature of 120°C to remove moisture from the slurry and obtain dried precursor powder.

[0124] Step 3: Calcine the above precursor powder at 620℃ for 10 hours, then allow it to cool naturally to obtain Na. 4.05 Mn 2.0 Fe 1.0 P4O 15 Material.

[0125] Will Na 4.05 Mn 2.0 Fe 1.0 P4O 15 Material SurP and PVDF5130 are added in a mass ratio of 9.4:0.3:0.3. NMP is mixed, and the above materials are mixed evenly using a high-speed homogenizer to form a black slurry with uniform color and high fluidity. Of The black paste was then coated onto aluminum foil using a 150µm four-sided coating apparatus, and the membrane was dried in a vacuum drying oven at 100℃ for 2 hours. The electrode membrane was punched into a disc with a radius of 0.6mm using a punching machine. Sodium metal was used as the counter electrode, 1mol / L NaClO4EC+DEC (1:1 vol%)+5% FEC was used as the electrolyte, and a PP / PE / PP three-layer separator was used. The membrane was assembled into a CR2016 button cell in a glove box.

[0126] Table 1 shows the Na 4.05 Mn 2.0 Fe 1.0 P4O 15Key electrochemical performance of the electrode. At a low rate of 0.1C (1C = 129 mAh / g), the discharge specific capacity of this electrode was only 122.1 mAh / g, lower than that of the application example. This phenomenon can be attributed to the deficiencies of the single-stage sintering process, which resulted in uneven distribution of transition metal elements such as manganese and iron in the crystal lattice, forming a large number of vacancies and lattice defects. This reduced the effective sodium ion storage sites in the material, limiting the full realization of its theoretical capacity. Furthermore, the impact of structural defects on the electrode's kinetic performance was more pronounced at high rates. As shown in Table 1, at a high rate of 10C, the capacity retention rate of this electrode (relative to 0.1C) was only 92.3%, significantly inferior to the application example. This indicates that microstructural defects not only reduced the number of active sites but also severely hindered rapid charge transport: on the one hand, defects act as electron scattering centers, increasing the bulk electronic conduction impedance; on the other hand, the increased energy barriers at grain boundaries and phase boundaries significantly slowed down the cross-interfacial migration rate of sodium ions, ultimately leading to a significant decrease in rate performance. Long-term cycling performance testing further revealed the structural instability of this electrode. At 1C rate, after 1000, 2000, and 3000 cycles, its capacity retention decreased to 92.7%, 82.6%, and 57.4%, respectively, exhibiting a significant accelerated decay trend. This degradation behavior is mainly due to the combined effect of two mechanisms: firstly, the continuous Jahn-Teller distortion of Mn³⁺ in the material during cycling induces lattice distortion and local stress concentration, ultimately leading to manganese ion dissolution and host structure collapse; secondly, the electrode surface catalyzes the oxidative decomposition of the electrolyte under high voltage, forming a thick and unstable cathode-electrolyte interface film, further exacerbating the increase in interfacial impedance and capacity decay. Elemental analysis of the negative electrode after 3000 cycles showed a manganese deposition level as high as 4800 ppm, directly confirming severe manganese dissolution in the cathode material. After these dissolved manganese ions migrate to the surface of the negative electrode, they will disrupt the stability of the solid electrolyte interface film, catalyze the continuous consumption of sodium and electrolyte, and form a vicious cycle of "positive electrode structure degradation - manganese dissolution - negative electrode interface deterioration - capacity decay", ultimately leading to accelerated battery performance failure.

[0127] Table 1 Performance Test Results

[0128] Application Example 1 Application Example 2 Comparative Example 1 Comparative Example 2 0.1C discharge specific capacity (mAh / g) 128.6 126.9 123.4 122.1 Capacity retention at 10C rate (10C / 0.1C %) 93.5 94.2 91.3 92.3 Retention rate after 1000 cycles at 1C ratio (%) 97.8 97.0 93.6 92.7 Retention rate at 1C ratio for 2000 cycles (%) 95.3 94.5 85.3 82.6 Retention rate at 1C ratio for 3000 cycles (%) 92.6 91.2 61.2 57.4 Mn content (PPM) on the negative electrode side after 3000 cycles 13 24 3500 4800

[0129] The above embodiments are merely specific examples of the present invention, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A metal phosphide-coated sodium manganese iron phosphate pyrophosphate cathode material, the cathode material being in a core-shell structure, comprising an inner core material and a coating shell layer, characterized in that: The chemical formula of the core material is Na a Mn 3-b Fe b P4O 15 phosphate, wherein 4.0≤a≤4.1, 0 a metal phosphide ion conductor layer.

2. The metal phosphide-coated sodium manganese iron phosphatophosphate cathode material of claim 1, wherein: The metal phosphide ion conductor layer is an amorphous structure metal phosphide, and the metal phosphide is one or two or more of zirconium phosphide, titanium phosphide, nickel phosphide, cobalt phosphide, iron phosphide, and tin phosphide.

3. The metal phosphide-coated sodium manganese iron phosphatophosphate cathode material of claim 1, wherein: The thickness of the metal phosphide ion conductor layer is 1-10 nm, and the mass is 0.1-3 wt% of the positive electrode material.

4. A process for the preparation of the metal phosphide-coated sodium manganese iron pyrophosphate positive electrode material according to any one of claims 1 to 3, characterized in that The method comprises the following steps: S1, preparation of a precursor solution: dissolving a sodium source, a manganese source, an iron source, a core phosphorus source, and a carbon source in deionized water in stoichiometric proportions to form a uniform precursor solution; S2, drying of the precursor dry powder: spray drying the precursor solution to achieve solid-liquid separation to obtain a dried precursor powder; S3, one-step sintering: the precursor powder is calcined in stages in a protective atmosphere, and the inner core Na a Mn 3-b Fe b P4O 15 material; S4, surface coating: the core Na a Mn 3-b Fe b P4O 15 The material, the coating metal source and the coating phosphorus source are mixed with water, and the reaction is carried out under stirring, so that the metal phosphide is uniformly adsorbed and deposited on the surface of the core material, and a precursor material with uniform coating is formed. S5 secondary calcination: the precursor material is calcined at high temperature under a protective atmosphere, and then naturally cooled to obtain the final Na a Mn 3- b Fe b P4O 15 phosphate material.

5. The method for preparing the metal phosphide-coated sodium manganese phosphate ferric phosphate cathode material according to claim 4, characterized in that: In step S3, the sintering process is staged sintering, including a first stage and a second stage: the first stage is heated to 300-400℃, and the holding time is >0.1H; the second stage is heated to 550-700℃; the protective atmosphere is nitrogen, argon, or nitrogen / hydrogen / argon mixed gas.

6. The method for preparing the metal phosphide-coated sodium manganese phosphate ferric phosphate cathode material according to claim 4, characterized in that: In step S5, the secondary sintering temperature is 350-550℃.

7. The method for preparing the metal phosphide-coated sodium manganese phosphate ferric phosphate cathode material according to claim 4, characterized in that: In step S1, the sodium source is one or two or more of sodium formate, sodium acetate, sodium oxalate, sodium citrate, sodium nitrate, sodium carbonate, sodium bicarbonate, and sodium hydroxide; The manganese source is one or two or more of manganese nitrate, manganese sulfate, manganese acetate, and manganese citrate; The iron source is one or two or more of ferrous sulfate, iron sulfate, ferrous chloride, iron oxide, iron acetate, and ferrous ammonium sulfate; The core phosphorus source is one or two or more of phosphoric acid, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate.

8. The method for preparing the metal phosphide-coated sodium manganese phosphate ferric phosphate cathode material according to claim 4, characterized in that: In step S1, the carbon source is one or two or more of citric acid, glucose, sucrose, maltose, soluble starch, graphene and its derivatives, carbon nanotubes and their derivatives, and carbon black and its derivatives.

9. The method for preparing the metal phosphide-coated sodium manganese phosphate ferric phosphate cathode material according to claim 4, characterized in that: In step S4, the coating metal source is one or two or more of a zirconium source, a titanium source, a nickel source, a cobalt source, an iron source, and a tin source; the zirconium source is one or two or more of zirconium oxychloride, zirconium sulfate, zirconium acetate, and zirconium ammonium carbonate; the titanium source is one or two or more of titanium oxysulfate, tetrabutyl carbonate, and titanium tetraethyl titanate; the nickel source is one or two or more of nickel sulfate, nickel nitrate, and nickel acetate; the cobalt source is one or two or more of cobalt sulfate, cobalt nitrate, and cobalt acetate; the iron source is one or two or more of iron sulfate, iron nitrate, and iron acetate; and the tin source is one or two or more of stannous sulfate, tributyltin chloride, and dibutyltin dilaurate.

10. The method for preparing the metal phosphide-coated sodium manganese phosphate ferric phosphate cathode material according to claim 4, characterized in that: In step S4, the coating phosphoric acid is one or two or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate.

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