Preparation method of lithium iron phosphate battery positive electrode material

Abstract

The invention relates to the technical field of preparation of electrode materials, in particular to a preparation method of a lithium iron phosphate battery positive electrode material, which comprises the following steps: S1, preparation of a lithium iron phosphate / multi-walled carbon nanotube compound: S1-1, preparation of a lithium source solution, S1-2, preparation of a multi-walled carbon nanotube dispersion liquid, S1-3, preparation of a surfactant aqueous solution, S1-4, hydrothermal reaction, and S2, composite material granulation. S3, preparing the positive electrode material of the lithium battery: S3-1, mixing the graphene nanosheets; S3-2, preparing slurry; S3-3, coating and drying; and S3-4, performing vacuum treatment. The preparation process of the electrode material is simple, the uniformity of the prepared material can be effectively guaranteed, the compactness of the electrode material is prevented from being influenced, and the electrochemical performance, such as the energy density, the power density and the cycling stability of the battery material, of the battery material can be effectively improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electrode material preparation, and particularly relates to a preparation method of a lithium iron phosphate battery positive electrode material. BACKGROUND

[0002] Lithium ion batteries have become the core power source of modern electronic devices, electric vehicles and large-scale energy storage systems due to their high energy density, long cycle life and environmental protection advantages, and the positive electrode material plays a crucial role in the overall performance of the battery, and the lithium iron phosphate positive electrode material is favored due to its excellent thermal stability, safety, cost-effectiveness and environmental friendliness.

[0003] However, the low electronic and ionic conductivity of lithium iron phosphate limits its performance in high-power applications. In order to improve the conductivity of the material, the common method is to improve the electronic conductivity of the material by element doping or carbon coating. Although element doping and carbon coating can effectively improve the conductivity of the material, other problems follow, such as product quality fluctuations caused by uneven element doping and the influence of excessive carbon coating on the compactness of the material and the energy density of the battery. SUMMARY

[0004] In view of the above problems, the application provides a preparation method of a lithium iron phosphate battery positive electrode material to solve the problems that the method for improving the conductivity of the lithium iron phosphate electrode material in the prior art is prone to uneven doping, which causes product quality fluctuations, and excessive carbon coating easily affects the compactness of the electrode material and the energy density of the battery.

[0005] To achieve the above purpose, the application provides a preparation method of a lithium iron phosphate battery positive electrode material, which specifically comprises the following steps:

[0006] S1, preparing a lithium iron phosphate / multi-walled carbon nanotube composite:

[0007] S1-1, preparing a lithium source solution: dissolving a soluble lithium source in deionized water to prepare a lithium source solution;

[0008] S1-2, preparing a multi-walled carbon nanotube dispersion: adding multi-walled carbon nanotubes into deionized water and dispersing the multi-walled carbon nanotubes through ultrasonic treatment to prepare a multi-walled carbon nanotube dispersion;

[0009] S1-3, preparing a surfactant aqueous solution: adding polyvinylpyrrolidone and sodium polyacrylate into deionized water and stirring uniformly;

[0010] S1-4, hydrothermal reaction: the lithium source solution and the multi-walled carbon nanotube dispersion liquid are added into the surfactant aqueous solution, mixed thoroughly, then the iron source and the phosphorus source are added into the surfactant aqueous solution, stirred uniformly, and then added into a high-pressure reaction kettle, reacted under high-temperature conditions, and after the reaction is completed, the reaction liquid is filtered, washed, dried, and ball-milled to obtain a modified lithium iron phosphate / multi-walled carbon nanotube composite material precursor;

[0011] S2, composite material granulation: a binder is added to the modified lithium iron phosphate / multi-walled carbon nanotube composite material, deionized water is added, mixed thoroughly, homogenized, dried, carbonized at high temperature in an inert atmosphere furnace, and a modified lithium iron phosphate / multi-walled carbon nanotube composite material is obtained.

[0012] S3, preparation of a lithium battery positive electrode material:

[0013] S3-1, graphene nanosheet mixing: the modified lithium iron phosphate / multi-walled carbon nanotube composite material and the graphene nanosheet are mixed uniformly in a mixer, so that the graphene nanosheet is uniformly distributed on the surface of the modified lithium iron phosphate / multi-walled carbon nanotube composite material particles.

[0014] S3-2, slurry preparation: the modified lithium iron phosphate / multi-walled carbon nanotube composite material coated with the graphene nanosheet obtained in step S3-1, polyvinylpyrrolidone, sodium polyacrylate, and a binder are mixed, deionized water is added, and stirred uniformly to obtain a uniform slurry.

[0015] S3-3, coating and drying: the slurry is uniformly coated on an aluminum foil current collector, and the coated aluminum foil current collector is placed in a drying oven and dried until the slurry is completely dried.

[0016] S3-4, vacuum treatment: the dried aluminum foil current collector is placed in a vacuum oven for vacuum treatment to obtain a lithium battery positive electrode material.

[0017] Further, in step S1-1, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium oxalate, and the concentration of the lithium source solution is 1.5-2 mol / L.

[0018] Further, in step S1-2, the ultrasonic treatment time of the multi-walled carbon nanotube is 20-30 min, and the solid content of the multi-walled carbon nanotube dispersion liquid is 2-5 wt%.

[0019] Further, the mass ratio of polyvinylpyrrolidone and sodium polyacrylate in step S1-3 to the modified lithium iron phosphate / multi-walled carbon nanotube composite material precursor in step S1-4 is 0.07-0.23%:0.06-0.18%:1.

[0020] Further, in the step S1-4, the iron source is one or more of FeSO4.H2O, FePO4 and FeSO4.7H2O, the phosphorus source is one or more of ammonium dihydrogen phosphate, ammonium hydrogen phosphate and lithium dihydrogen phosphate, the molar ratio of lithium, iron and phosphorus is Li:Fe:P=1~1.04:0.97~1:1, the mass of the multi-walled carbon nanotubes in the multi-walled carbon nanotube dispersion is 0.02~0.05% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material precursor, the hydrothermal reaction temperature is 100~300℃, and the reaction time is 4~8h.

[0021] Further, in the steps S2 and S3, the binder is one or more of polyacrylic acid, chitosan and sodium carboxymethyl cellulose; in the step S2, the mass of the binder is 0.06~0.18% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the high-temperature carbonization treatment temperature is 650~800℃, the heating rate is 3~5℃ / min, and the holding time is 6~8h.

[0022] Further, in the step S3-2, the mass ratio of the modified lithium iron phosphate / multi-walled carbon nanotube composite material: polyvinylpyrrolidone: sodium polyacrylate: graphene nanosheet: binder in the lithium battery positive electrode material is 1:0.07~0.23%:0.06~0.18%:0.03~0.09%:0.06~0.18%; in the step S3-3, the drying temperature is 100~150℃, and the drying time is 1~3h; and in the step S3-4, the vacuum treatment pressure is-0.095MPa, the vacuum treatment temperature is 70~90℃, and the vacuum treatment time is 1~2h.

[0023] Advantages of the present application:

[0024] The preparation process of the electrode material in the present application is simple, and the prepared material can effectively ensure uniformity, avoid affecting the compactness of the electrode material, and effectively improve the electrochemical performance of the battery material, such as the energy density, power density and cycle stability of the battery material.

[0025] In the present application, a surfactant is used, which can effectively improve the dispersibility and interface bonding effect between lithium iron phosphate and multi-walled carbon nanotubes, and improve the conductivity of the battery material.

[0026] The preparation method of the positive electrode material in the present application is suitable for industrial scale production, and by adjusting the ratio of the surfactant, lithium iron phosphate and multi-walled carbon nanotubes, the performance of the electrode material can be optimized. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0028] Embodiment one

[0029] A preparation method of a lithium iron phosphate battery positive electrode material, specifically comprising the following steps:

[0030] S1, preparing a lithium iron phosphate / multi-walled carbon nanotube composite:

[0031] S1-1, preparing a lithium source solution: dissolving lithium carbonate in deionized water to prepare a lithium source solution with a concentration of 1.5 mol / L;

[0032] S1-2, preparing a multi-walled carbon nanotube dispersion: adding multi-walled carbon nanotubes into deionized water and dispersing the multi-walled carbon nanotubes by ultrasonic treatment for 30 min to prepare a multi-walled carbon nanotube dispersion with a content of 2 wt%;

[0033] S1-3, preparing a surfactant aqueous solution: according to the modified lithium iron phosphate / multi-walled carbon nanotube composite material precursor: polyvinylpyrrolidone: sodium polyacrylate = 1:0.09%:0.08%, polyvinylpyrrolidone and sodium polyacrylate are weighed and added into deionized water, and stirred uniformly;

[0034] S1-4, hydrothermal reaction: according to the molar ratio of lithium, iron and phosphorus elements 1.02:0.98:1, lithium source, iron source and phosphorus source are measured; first, the lithium source solution and the multi-walled carbon nanotube dispersion are added into the surfactant aqueous solution, wherein the mass of the multi-walled carbon nanotubes in the multi-walled carbon nanotube dispersion is 0.025% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material precursor, and they are mixed thoroughly, then ferrous sulfate FeSO4·7H2O and phosphoric acid H3PO4 are added into the surfactant aqueous solution, which is stirred uniformly and then added into a high-pressure reaction kettle, and the reaction is continued for 7 h at 100℃, after the reaction is completed, the reaction liquid is naturally cooled to room temperature, and after filtration, washing, drying and ball milling, the modified lithium iron phosphate / multi-walled carbon nanotube composite material precursor is prepared;

[0035] S2, granulating the composite material: deionized water and 0.1% binder are added into the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the binder is a uniform mixture of polyacrylic acid, chitosan and sodium hydroxymethyl cellulose, and after being mixed thoroughly and homogenized by mechanical stirring or ball milling, it is dried, carbonized at 650℃ in an inert atmosphere furnace for 6 h, and then microparticles with a particle size D50 of 9.62 μm are obtained, thereby the modified lithium iron phosphate / multi-walled carbon nanotube composite material is prepared;

[0036] S3, preparing a lithium battery positive electrode material:

[0037] S3-1 mixing graphene nanosheets: the modified lithium iron phosphate / multi-walled carbon nanotube composite material is mixed with graphene nanosheets in a mixer, the mass of graphene nanosheets is 0.03% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, so that the graphene nanosheets are uniformly distributed on the surface of the modified lithium iron phosphate / multi-walled carbon nanotube composite material particles;

[0038] S3-2 slurry preparation: the modified lithium iron phosphate / multi-walled carbon nanotube composite material coated with graphene nanosheets prepared in step S3-1, polyvinylpyrrolidone, sodium polyacrylate and a binder are mixed, the mass of polyvinylpyrrolidone is 0.2% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the mass of sodium polyacrylate is 0.1% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the mass of the binder is 0.1% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the binder is a uniform mixture of polyacrylic acid, chitosan and sodium hydroxymethyl cellulose, deionized water is added and stirred uniformly to prepare a uniform slurry, and the solid content is controlled to be 42%;

[0039] S3-3 coating and drying: the slurry is uniformly coated on an aluminum foil current collector, the coated aluminum foil current collector is placed in a drying oven, dried at 120℃ for 2h, and the slurry is completely dried;

[0040] S3-4 vacuum treatment: the dried aluminum foil current collector is placed in a vacuum oven, the vacuum pressure is-0.095MPa, and the vacuum treatment is carried out at 85℃ for 1.5h to prepare a lithium battery positive electrode material.

[0041] Example two

[0042] A preparation method of a lithium iron phosphate battery positive electrode material, specifically comprising the following steps:

[0043] S1, preparing a lithium iron phosphate / multi-walled carbon nanotube composite:

[0044] S1-1, preparing a lithium source solution: lithium carbonate is dissolved in deionized water to prepare a lithium source solution with a concentration of 1.55mol / L;

[0045] S1-2, preparing a multi-walled carbon nanotube dispersion: multi-walled carbon nanotubes are added to deionized water, and the multi-walled carbon nanotubes are dispersed by ultrasonic treatment for 30min to prepare a multi-walled carbon nanotube dispersion with a content of 5wt%;

[0046] S1-3, preparation of surfactant aqueous solution: polyvinylpyrrolidone and polyacrylic acid sodium were weighed according to the modified lithium iron phosphate / multi-walled carbon nanotube composite precursor: polyvinylpyrrolidone: polyacrylic acid sodium = 1:0.1%:0.07%, and added to deionized water, and stirred uniformly;

[0047] S1-4, hydrothermal reaction: lithium source, iron source and phosphorus source were weighed according to the molar ratio of lithium, iron and phosphorus elements 1.01:0.975:1; first, the lithium source solution and the multi-walled carbon nanotube dispersion were added to the surfactant aqueous solution, wherein the mass of the multi-walled carbon nanotube in the multi-walled carbon nanotube dispersion was 0.025% of the modified lithium iron phosphate / multi-walled carbon nanotube composite precursor, and they were mixed thoroughly, then ferrous sulfate FeSO4·7H2O and phosphoric acid H3PO4 were added to the surfactant aqueous solution, and after stirring uniformly, they were added to a high-pressure reaction kettle, and the reaction was continued for 5h at 150℃, after the reaction was completed, the reaction liquid was naturally cooled to room temperature, and after filtration, washing, drying and ball milling, the modified lithium iron phosphate / multi-walled carbon nanotube composite precursor was prepared;

[0048] S2, composite material granulation: deionized water and 0.1% binder were added to the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the binder was a uniform mixture of polyacrylic acid, chitosan and sodium hydroxymethyl cellulose, and after being mixed, homogenized and dried by mechanical stirring or ball milling, the mixture was carbonized at 800℃ in an inert atmosphere furnace for 8h to obtain microparticles with a particle size D50 of 8.83μm, and the modified lithium iron phosphate / multi-walled carbon nanotube composite material was prepared;

[0049] S3, preparation of lithium battery positive electrode material:

[0050] S3-1, graphene nanosheet mixing: the modified lithium iron phosphate / multi-walled carbon nanotube composite material was mixed with graphene nanosheets in a mixer, wherein the mass of the graphene nanosheets was 0.03% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, so that the graphene nanosheets were uniformly distributed on the surface of the modified lithium iron phosphate / multi-walled carbon nanotube composite material microparticles;

[0051] S3-2, slurry preparation: the modified lithium iron phosphate / multi-walled carbon nanotube composite material coated with graphene nanosheets prepared in step S3-1, polyvinylpyrrolidone, polyacrylic acid sodium and a binder were mixed, wherein the mass of the polyvinylpyrrolidone was 0.2% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the mass of the polyacrylic acid sodium was 0.1% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, and the mass of the binder was 0.1% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the binder was a uniform mixture of polyacrylic acid, chitosan and sodium hydroxymethyl cellulose, deionized water was added, and stirring was performed until a uniform slurry was obtained, and the solid content was controlled to be 45%;

[0052] S3-3 coating and drying: the slurry is uniformly coated on the aluminum foil current collector, and the coated aluminum foil current collector is placed in a drying oven and dried at 130°C for 2h to completely dry the slurry;

[0053] S3-4 vacuum treatment: the dried aluminum foil current collector is placed in a vacuum oven, vacuum pressure is -0.095MPa, and vacuum treatment is carried out at 90°C for 1.2h to obtain a lithium battery positive electrode material.

[0054] Example Three

[0055] A preparation method of a lithium iron phosphate battery positive electrode material, specifically comprising the following steps:

[0056] S1, preparation of lithium iron phosphate / multi-walled carbon nanotube composite:

[0057] S1-1, preparation of lithium source solution: lithium carbonate is dissolved in deionized water to prepare a lithium source solution with a concentration of 1.6mol / L;

[0058] S1-2, preparation of multi-walled carbon nanotube dispersion: multi-walled carbon nanotubes are added to deionized water, and the multi-walled carbon nanotubes are dispersed by ultrasonic treatment for 30min to prepare a multi-walled carbon nanotube dispersion with a content of 5wt%;

[0059] S1-3, preparation of surfactant aqueous solution: polyvinylpyrrolidone and sodium polyacrylate are weighed according to the modified lithium iron phosphate / multi-walled carbon nanotube composite precursor: polyvinylpyrrolidone: sodium polyacrylate = 1:0.08%:0.11%, and added to deionized water and stirred uniformly;

[0060] S1-4, hydrothermal reaction: lithium, iron and phosphorus sources are weighed according to the molar ratio of 1.02:0.99:1; first, the lithium source solution and the multi-walled carbon nanotube dispersion are added to the surfactant aqueous solution, wherein the mass of the multi-walled carbon nanotubes in the multi-walled carbon nanotube dispersion is 0.025% of the modified lithium iron phosphate / multi-walled carbon nanotube composite precursor, and the mixture is fully mixed, then ferrous sulfate FeSO4·7H2O and phosphoric acid H3PO4 are added to the surfactant aqueous solution, and after stirring uniformly, the mixture is added to a high-pressure reaction kettle, and the reaction is continuously carried out at 200°C for 4.5h, and after the reaction is completed, the reaction liquid is naturally cooled to room temperature, and after filtration, washing, drying and ball milling, the modified lithium iron phosphate / multi-walled carbon nanotube composite precursor is obtained;

[0061] S2, composite material granulation: 0.1% binder is added to the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the binder is a uniform mixture of polyacrylic acid, chitosan and sodium hydroxymethyl cellulose, and is fully mixed, homogenized by mechanical stirring or ball milling, and then dried. Carbonization is carried out at 800℃ in an inert atmosphere furnace for 7h, and microparticles with a particle size D50 of 9.88μm are obtained, and a modified lithium iron phosphate / multi-walled carbon nanotube composite material is prepared;

[0062] S3, preparation of lithium battery positive electrode material:

[0063] S3-1, graphene nanosheet mixing: the modified lithium iron phosphate / multi-walled carbon nanotube composite material is mixed with graphene nanosheets in a mixer, the mass of graphene nanosheets is 0.03% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, and the graphene nanosheets are uniformly distributed on the surface of the modified lithium iron phosphate / multi-walled carbon nanotube composite material microparticles;

[0064] S3-2, slurry preparation: the modified lithium iron phosphate / multi-walled carbon nanotube composite material coated with graphene nanosheets prepared in step S3-1, polyvinylpyrrolidone, polyacrylic acid sodium and binder are mixed, the mass of polyvinylpyrrolidone is 0.2% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the mass of polyacrylic acid sodium is 0.1% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the mass of the binder is 0.1% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the binder is a uniform mixture of polyacrylic acid, chitosan and sodium hydroxymethyl cellulose, deionized water is added, and stirring is performed until the slurry is uniform. The solid content of the slurry is controlled to be 43%;

[0065] S3-3, coating and drying: the slurry is uniformly coated on an aluminum foil current collector, and the coated aluminum foil current collector is placed in a drying oven and dried at 125℃ for 2h to completely dry the slurry;

[0066] S3-4, vacuum treatment: the dried aluminum foil current collector is placed in a vacuum oven, the vacuum pressure is-0.095MPa, and the vacuum treatment is carried out at 80℃ for 2h to prepare a lithium battery positive electrode material.

[0067] Comparative Example One

[0068] Compared with Example One, no surfactants polyvinylpyrrolidone and polyacrylic acid sodium are added, and the other steps are the same;

[0069] Comparative Example Two

[0070] Compared with Example One, no surfactants polyvinylpyrrolidone and polyacrylic acid sodium and multi-walled carbon nanotubes are added, and the other steps are the same;

[0071] The positive electrode material in the above examples 1-3 and comparative examples 1-2 is used to assemble a 2032 button cell, and the assembled 2032 button cell is subjected to electrical performance test in a voltage range of 2.5-4.2V, and the test results are shown in Table 1.

[0072] Table 1: Test data of 2030 button cell

[0073]

[0074] According to the test data in Table 1, it can be found that the electrochemical performance of the electrode material in examples 1-3 is better than that in comparative examples 1-2, indicating that the addition of surfactant and multi-walled carbon nanotubes has an improvement effect on the electrochemical performance of the prepared electrode material, and helps to improve the quality of the electrode material.

[0075] The preferred and optional technical means disclosed in the present application can be combined in any manner, unless otherwise specified, and one preferred or optional technical means is further limited by another technical means, to form several different technical solutions. Therefore, equivalent changes made in accordance with the claims are still within the scope of the present application.

Claims

1. A method for preparing a lithium iron phosphate battery cathode material, characterized in that, Specifically, the steps include the following: S1. Preparation of lithium iron phosphate / multi-walled carbon nanotube composite: S1-1. Preparation of lithium source solution: Dissolve soluble lithium source in deionized water to prepare lithium source solution; S1-2. Preparation of multi-walled carbon nanotube dispersion: Multi-walled carbon nanotubes are added to deionized water and dispersed by ultrasonic treatment to prepare multi-walled carbon nanotube dispersion. S1-3. Preparation of surfactant aqueous solution: Add polyvinylpyrrolidone and sodium polyacrylate to deionized water and stir until homogeneous; S1-4. Hydrothermal reaction: The lithium source solution and multi-walled carbon nanotube dispersion were added to the surfactant aqueous solution and mixed thoroughly. Then, iron source and phosphorus source were added to the surfactant aqueous solution and stirred evenly before being added to a high-pressure reactor. The reaction was carried out under high temperature conditions. After the reaction was completed, the reaction solution was filtered, washed, dried, and ball-milled to obtain the modified lithium iron phosphate / multi-walled carbon nanotube composite material precursor. S2. Granulation of composite materials: Add binder and deionized water to the modified lithium iron phosphate / multi-walled carbon nanotube composite material, mix thoroughly, homogenize and dry, and carbonize at high temperature in an inert atmosphere furnace to obtain the modified lithium iron phosphate / multi-walled carbon nanotube composite material. S3. Preparation of lithium battery cathode materials: S3-1 Graphene Nanosheet Mixing: The modified lithium iron phosphate / multi-walled carbon nanotube composite material and graphene nanosheets are mixed evenly in a mixer so that the graphene nanosheets are evenly distributed on the surface of the modified lithium iron phosphate / multi-walled carbon nanotube composite material particles. S3-2 Slurry Preparation: The modified lithium iron phosphate / multi-walled carbon nanotube composite material with graphene nanosheets on the surface obtained in step S3-1, polyvinylpyrrolidone, sodium polyacrylate and binder are mixed, deionized water is added, and the mixture is stirred evenly to prepare a uniform slurry. S3-3 Coating and Drying: Coat the slurry evenly onto the aluminum foil current collector, place the coated aluminum foil current collector into a drying oven, and dry until the slurry is completely dry; S3-4 Vacuum treatment: The dried aluminum foil current collector is placed in a vacuum oven and vacuum treated to obtain the positive electrode material for lithium batteries.

2. The method for preparing a lithium iron phosphate battery cathode material according to claim 1, characterized in that, In step S1-1, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium oxalate, and the concentration of the lithium source solution is 1.5~2 mol / L.

3. The method for preparing a lithium iron phosphate battery cathode material according to claim 1, characterized in that, In steps S1-2, the ultrasonic treatment time of multi-walled carbon nanotubes is 20-30 min, and the solid content of the multi-walled carbon nanotube dispersion is 2-5 wt%.

4. The method for preparing a lithium iron phosphate battery cathode material according to claim 1, characterized in that, The mass ratio of polyvinylpyrrolidone and sodium polyacrylate in step S1-3 to the modified lithium iron phosphate / multi-walled carbon nanotube composite precursor in step S1-4 is 0.07~0.23%:0.06~0.18%:

1.

5. The method for preparing a lithium iron phosphate battery cathode material according to claim 1, characterized in that, In steps S1-4, the iron source is one or more of FeSO4·H2O, FePO4, and FeSO4·7H2O, and the phosphorus source is one or more of ammonium dihydrogen phosphate, hydrogen phosphate, and lithium dihydrogen phosphate. The molar ratio of lithium, iron, and phosphorus is Li:Fe:P = 1~1.04:0.97~1:

1. The mass of multi-walled carbon nanotubes in the multi-walled carbon nanotube dispersion is 0.02~0.05% of the precursor of the modified lithium iron phosphate / multi-walled carbon nanotube composite material. The hydrothermal reaction temperature is 100~300℃, and the reaction time is 4~8h.

6. The method for preparing a lithium iron phosphate battery cathode material according to claim 1, characterized in that, In steps S2 and S3, the binder is one or more of polyacrylic acid, chitosan, and sodium carboxymethyl cellulose; in step S2, the mass of the binder is 0.06~0.18% of the modified lithium iron phosphate / multi-walled carbon nanotube composite material, the high-temperature carbonization treatment temperature is 650~800℃, the heating rate is 3~5℃ / min, and the holding time is 6~8h.

7. The method for preparing a lithium iron phosphate battery cathode material according to claim 1, characterized in that, In step S3-2, the mass ratio of modified lithium iron phosphate / multi-walled carbon nanotube composite material, polyvinylpyrrolidone, sodium polyacrylate, graphene nanosheets, and binder in the lithium battery cathode material is 1:0.07~0.23%:0.06~0.18%:0.03~0.09%:0.06~0.18%; in step S3-3, the drying temperature is 100~150℃, and the drying time is 1~3h; in step S3-4, the vacuum treatment pressure is -0.095MPa, the vacuum treatment temperature is 70~90℃, and the vacuum treatment time is 1~2h.

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