Lithium manganese iron phosphate positive electrode material, preparation method thereof and lithium manganese iron phosphate battery

Abstract

The invention provides a lithium iron manganese phosphate positive electrode material, a preparation method thereof and a lithium iron manganese phosphate battery, and belongs to the technical field of lithium iron manganese phosphate batteries. According to the preparation method, the positive electrode material of the lithium iron manganese phosphate battery is prepared by combining spray granulation with two times of sintering and carbon coating, so that the processability and the high-temperature electrochemical performance of the positive electrode material of the lithium iron manganese phosphate battery are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium manganese iron phosphate batteries, and in particular relates to a lithium manganese iron phosphate positive electrode material and a preparation method thereof, and a lithium manganese iron phosphate battery. Background Art

[0002] The conventional preparation methods of lithium manganese iron phosphate are dry method and liquid phase method. The prepared positive electrode material is single crystal particles with large specific surface area, usually >18m 2 / g, and the larger the specific surface area of ​​the positive electrode material, the larger the contact area with the solvent, which easily causes the slurry viscosity to increase, making it difficult to coat, and significantly affecting the battery processing process. Therefore, in order to reduce the slurry viscosity, the amount of solvent must be increased. At this time, the solid content of the slurry will decrease, the compaction density will decrease, and the prepared battery will have poor high-temperature storage performance and high-temperature cycle performance. The above problems hinder the practical application of lithium manganese iron phosphate positive electrode materials. Therefore, it is necessary to design a lithium manganese iron phosphate positive electrode material and its preparation method and lithium manganese iron phosphate battery, which can improve the processing performance and high-temperature electrochemical performance of the lithium manganese iron phosphate positive electrode material. Summary of the Invention

[0003] The present invention aims to at least partially address one of the technical problems in the related art. To this end, embodiments of the present invention provide a lithium iron manganese phosphate cathode material, a preparation method thereof, and a lithium iron manganese phosphate battery. The preparation method can improve the processing performance and high-temperature electrochemical performance of the lithium iron manganese phosphate cathode material.

[0004] The method for preparing the lithium manganese iron phosphate positive electrode material according to the embodiment of the present invention comprises the following steps:

[0005] (1) dispersing an iron source, a phosphorus source, a manganese source, a first carbon source, and an ion dopant in a dispersant to obtain a first mixed liquid, performing a first grinding process on the first mixed liquid to obtain a first slurry, and performing a first spraying process on the first slurry to obtain a spherical first precursor powder;

[0006] (2) performing a first sintering treatment on the first precursor powder under a nitrogen atmosphere to obtain a first sintered material;

[0007] (3) dispersing the first sintered material, a second carbon source, and a lithium source in a dispersant to obtain a second mixed solution, grinding the second mixed solution a second time to obtain a second slurry, and spraying the second slurry a second time to obtain a spherical second precursor powder;

[0008] (4) The second precursor powder is subjected to a second sintering treatment in a nitrogen atmosphere to obtain a second sintered material, and the second sintered material is subjected to a crushing treatment and a demagnetization treatment to obtain a spherical lithium manganese iron phosphate positive electrode material.

[0009] The advantages and technical effects of the method for preparing the lithium manganese iron phosphate positive electrode material according to the embodiment of the present invention are as follows:

[0010] (1) The embodiment of the present invention uses spray granulation to agglomerate nano-scale primary particles to form secondary spherical particles, thereby reducing the specific surface area of ​​the positive electrode material, and the specific surface area is controlled at 14m 2 / g~18m 2 / g, which improves the high-temperature cycle performance of the positive electrode material. At the same time, the spherical positive electrode material has good sphericity and fluidity, which significantly improves the processing performance of the positive electrode material;

[0011] (2) The lithium iron phosphate cathode material prepared in the embodiment of the present invention has a unique morphology, and the primary particles are nano-scale single crystal particles. Since the single crystal particles are small in size, the lithium ion diffusion path is short, thereby ensuring the capacity and rate performance of the cathode material;

[0012] (3) The embodiment of the present invention significantly improves the uniformity of carbon coating through a two-step sintering carbon coating method. Under the premise of ensuring a certain carbon content, the electronic conductivity of the positive electrode material is improved and manganese dissolution is inhibited, thereby improving the electrical performance of the positive electrode material.

[0013] (4) The preparation method of the embodiment of the present invention has a simple process, low energy consumption, and is suitable for large-scale production.

[0014] In some embodiments, the solid content of the first slurry and the second slurry is 30% to 50%.

[0015] In some embodiments, the median particle size of the solid material in the first slurry is less than or equal to 0.5 μm; and / or the median particle size of the solid material in the second slurry is 2 μm to 15 μm.

[0016] In some embodiments, the air source pressure of the spray equipment used in the first spray treatment and the second spray treatment is 0.3MPa~0.6MPa, the feeding frequency of the peristaltic pump of the spray equipment is 15Hz~30Hz, the air inlet temperature of the spray equipment is 240℃~300℃, and the exhaust temperature of the spray equipment is 100℃~110℃.

[0017] In some embodiments, the median particle size of the first precursor powder is 2 μm to 15 μm; and / or the median particle size of the second precursor powder is 2 μm to 15 μm.

[0018] In some embodiments, the temperature of the first sintering treatment is 500°C to 700°C, and the time of the first sintering treatment is 8h to 20h; and / or the temperature of the second sintering treatment is 700°C to 800°C, and the time of the second sintering treatment is 8h to 20h.

[0019] In some embodiments, the mass of the second carbon source is greater than or equal to the mass of the first carbon source.

[0020] In addition, an embodiment of the present invention further provides a lithium iron manganese phosphate positive electrode material, which is obtained by the preparation method of the lithium iron manganese phosphate positive electrode material of the embodiment of the present invention.

[0021] The advantages and technical effects brought by the lithium manganese iron phosphate positive electrode material of the embodiment of the present invention are:

[0022] (1) Due to the use of the preparation method of the embodiment of the present invention, the obtained lithium manganese iron phosphate positive electrode material is a secondary spherical particle formed by the agglomeration of nano-scale primary particles. The positive electrode material has high high-temperature cycle performance. At the same time, the spherical positive electrode material has good sphericity and good fluidity, which makes the positive electrode material have good processing performance.

[0023] (2) Due to the use of the preparation method of the embodiment of the present invention, the obtained lithium manganese iron phosphate positive electrode material has a uniform carbon coating layer, which makes the positive electrode material have good conductivity, thereby making the electrochemical performance of the positive electrode material higher.

[0024] In addition, an embodiment of the present invention further provides a lithium iron manganese phosphate battery, which uses the lithium iron manganese phosphate positive electrode material of the embodiment of the present invention.

[0025] The advantages and technical effects of the lithium manganese iron phosphate battery of the embodiment of the present invention are as follows:

[0026] Due to the use of the lithium manganese iron phosphate positive electrode material of the embodiment of the present invention, the lithium manganese iron phosphate battery of the embodiment of the present invention has high high-temperature storage stability and high-temperature cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a SEM image of the lithium manganese iron phosphate positive electrode material of Example 1;

[0028] Figure 2 This is an SEM image of the lithium manganese iron phosphate positive electrode material of Comparative Example 1;

[0029] Figure 3 This is the SEM image of the lithium manganese iron phosphate positive electrode material of Comparative Example 3. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0031] An embodiment of the present invention provides a method for preparing a lithium manganese iron phosphate positive electrode material, comprising the following steps:

[0032] (1) dispersing an iron source, a phosphorus source, a manganese source, a first carbon source, and an ion dopant in a dispersant to obtain a first mixed liquid, performing a first grinding process on the first mixed liquid to obtain a first slurry, and performing a first spraying process on the first slurry to obtain a spherical first precursor powder;

[0033] (2) performing a first sintering treatment on the first precursor powder under a nitrogen atmosphere to obtain a first sintered material;

[0034] (3) dispersing the first sintered material, a second carbon source, and a lithium source in a dispersant to obtain a second mixed solution, grinding the second mixed solution a second time to obtain a second slurry, and spraying the second slurry a second time to obtain a spherical second precursor powder;

[0035] (4) The second precursor powder is subjected to a second sintering treatment in a nitrogen atmosphere to obtain a second sintered material, and the second sintered material is subjected to a crushing treatment and a demagnetization treatment to obtain a spherical lithium manganese iron phosphate positive electrode material.

[0036] The embodiment of the present invention uses a spray granulation method to agglomerate the nano-scale primary particles into secondary spherical particles, thereby reducing the specific surface area of ​​the positive electrode material, and the specific surface area is controlled at 14m 2 / g~18m 2 / g, when the positive electrode material is used to assemble the battery, the positive electrode slurry has a high solid content, the coating difficulty is reduced, and the compaction density is high. On the other hand, the specific surface area is controlled at 14m 2 / g~18m 2 / g also improves the high-temperature storage performance and high-temperature cycling performance of the positive electrode material. At the same time, because the positive electrode material is spherical and has good sphericity, the fluidity of the positive electrode slurry is improved, thereby significantly improving the processing performance of the positive electrode material. In addition, the embodiment of the present invention also adopts a double-firing process to introduce two carbon coating processes, which improves the uniformity of the carbon coating while controlling the total carbon content, thereby further improving the high-temperature electrochemical performance of the positive electrode material.

[0037] In the preparation method of the embodiment of the present invention, the first spraying treatment is to granulate the raw materials to form spherical particles, and the first sintering treatment is used to form carbon-coated spherical particles. The second spraying treatment is then performed to mix the lithium source and the carbon source. The spraying method can improve the mixing effect, and the second sintering treatment is further used to form carbon-coated spherical lithium manganese iron phosphate.

[0038] The preparation method of the embodiment of the present invention has no particular restrictions on the types of iron source, phosphorus source, manganese source, lithium source, carbon source and ion dopant used. Any iron source, phosphorus source, manganese source, lithium source, carbon source and ion dopant in the prior art can be used as long as the lithium manganese iron phosphate positive electrode material can be prepared. For example, the iron source includes but is not limited to anhydrous iron phosphate; preferably, the tap density of the anhydrous iron phosphate is 0.8g / cm 3 ~1.64g / cm 3 . The phosphorus source includes but is not limited to at least one of phosphoric acid, ammonium monohydrogen phosphate and ammonium dihydrogen phosphate. The manganese source includes but is not limited to at least one of manganese carbonate, manganese oxalate, manganese acetate, manganese dioxide, manganese trioxide and manganese tetraoxide. The lithium source includes but is not limited to at least one of lithium carbonate, lithium acetate, lithium hydroxide and lithium phosphate. The carbon source includes but is not limited to at least one of glucose, polyethylene glycol, trimesic acid, white sugar, citric acid, sucrose, activated carbon, carbon nanotubes and graphene. The ion dopant includes but is not limited to at least one of aluminum oxide, aluminum hydroxide, titanium dioxide, magnesium oxide, magnesium hydroxide, zinc oxide, zirconium dioxide, vanadium pentoxide and ammonium metavanadate.

[0039] In some embodiments, the dispersant is at least one of water, ethanol, and methanol. The above dispersants can both evenly disperse the raw materials and evaporate quickly during the spraying process.

[0040] In some embodiments, the solid content of the first slurry is 30% to 50%, for example, 30%, 35%, 40%, 45%, 50%, etc. When the solid content of the first slurry is too low, solvent waste will result, resulting in low production efficiency. When the solid content of the first slurry is too high, the slurry is too viscous, and it is difficult to mix the iron source, phosphorus source, manganese source, first carbon source, and ion dopant uniformly.

[0041] The first grinding process is to reduce the particle size of the raw materials. In some embodiments, the median particle size of the solid material in the first slurry is less than or equal to 0.5 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, etc. The median particle size of the solid material in the first slurry determines the size of the primary particles in the subsequent spherical particles. If the median particle size of the solid material in the first slurry is too large, it indicates that the raw materials are not ground sufficiently, which will cause the primary particles in the subsequent spherical particles to be too large, affecting battery performance.

[0042] In some embodiments, the air source pressure of the spray equipment used in the first spray treatment is 0.3MPa to 0.6MPa, such as 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, etc., and the feeding frequency of the peristaltic pump of the spray equipment used in the first spray treatment is 15Hz to 30Hz, such as 15Hz, 20Hz, 25Hz, 30Hz, etc. When the air source pressure is too low, the first precursor powder will not be able to form a spherical shape, which will cause the final finished product, lithium manganese iron phosphate positive electrode material, to also not be spherical, affecting the processing performance of the positive electrode material. The air source pressure is higher than 0.6Mpa, which exceeds the equipment limit. When the feeding frequency is too low, the production efficiency is low. When the feeding frequency is too high, the forming is insufficient and rounded spherical particles cannot be formed well.

[0043] The main purpose of the first spraying treatment is granulation. In some embodiments, the air inlet temperature of the spray equipment used in the first spraying treatment is 240°C to 300°C, such as 240°C, 260°C, 280°C, 300°C, etc., and the exhaust temperature of the spray equipment used in the first spraying treatment is 100°C to 110°C, such as 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, etc. When the air inlet temperature is too low, the first precursor powder cannot be completely dried. When the air inlet temperature is too high, it will not have a more significant effect on the drying of the first precursor powder, but will increase energy consumption, which is not conducive to cost reduction and efficiency improvement. When the exhaust temperature is too low, the first precursor powder cannot be completely dried. When the exhaust temperature is too high, the discharge temperature of the first precursor powder is too high, which is not conducive to subsequent material storage and packaging.

[0044] In some embodiments, the median particle size of the first precursor powder is 2 μm to 15 μm, for example, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc. By controlling the spray conditions of the first spray treatment, the first precursor powder with controllable particle size is obtained, thereby obtaining a positive electrode material with controllable particle size, thereby controlling the specific surface area of ​​the positive electrode material to 14 m 2 / g~18m 2 / g, so as to improve the processing performance and high-temperature electrochemical performance of the positive electrode material.

[0045] In some embodiments, the temperature of the first sintering treatment is 500°C to 700°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, etc., and the time of the first sintering treatment is 8h to 20h, for example, 8h, 10h, 12h, 14h, 16h, 18h, 20h, etc. When the temperature of the first sintering treatment is too low, the iron source, phosphorus source, and manganese source do not react sufficiently, and a preliminary carbon coating structure cannot be formed. When the temperature of the first sintering treatment is too high, the iron source, phosphorus source, and manganese source react too violently, forming an intermediate material with good crystallinity. When step (4) is performed again, it is difficult to react with the lithium source to form a lithium iron manganese phosphate positive electrode material.

[0046] The main purpose of the second grinding process is to mix the first sintered material and other raw materials evenly, not to reduce the particle size. In some embodiments, the median particle size of the solid material in the second slurry is 2μm to 15μm, for example, 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 15μm, etc. When the median particle size of the solid material in the second slurry is too small, the specific surface area of ​​the material is too large, which reduces the subsequent slurry processing performance. When the median particle size of the solid material in the second slurry is too large, the lithium ion diffusion distance will be increased, reducing the kinetic properties of the material.

[0047] The main purpose of the second spray treatment is to allow other raw materials to evenly cover the surface of the first sintered material, and the spray parameters are the same as the first spray treatment.

[0048] In some embodiments, the air source pressure of the spray equipment used in the second spray treatment is 0.3MPa to 0.6MPa, such as 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, etc., and the feeding frequency of the peristaltic pump of the spray equipment used in the second spray treatment is 15Hz to 30Hz, such as 15Hz, 20Hz, 25Hz, 30Hz, etc. When the air source pressure is too low, the second precursor powder will not be able to form a spherical shape, which will cause the final finished product, lithium manganese iron phosphate positive electrode material, to also not be spherical, affecting the processing performance of the positive electrode material. The air source pressure is higher than 0.6Mpa, which exceeds the equipment limit. When the feeding frequency is too low, the production efficiency is low. When the feeding frequency is too high, the forming is insufficient and round spherical particles cannot be formed well.

[0049] In some embodiments, the inlet air temperature of the spray equipment used in the second spray treatment is 240°C to 300°C, for example, 240°C, 260°C, 280°C, 300°C, etc., and the exhaust air temperature of the spray equipment used in the second spray treatment is 100°C to 110°C, for example, 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, etc. When the inlet air temperature is too low, the second precursor powder cannot be completely dried. When the inlet air temperature is too high, it will not have a more significant effect on the drying of the second precursor powder, but will increase energy consumption, which is not conducive to cost reduction and efficiency improvement. When the exhaust air temperature is too low, the second precursor powder cannot be completely dried. When the exhaust air temperature is too high, the discharge temperature of the second precursor powder is too high, which is not conducive to subsequent material storage and packaging.

[0050] In some embodiments, the median particle size of the second precursor powder is 2 μm to 15 μm, for example, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc. By controlling the spray conditions of the second spraying process, the second precursor powder with controllable particle size is obtained, thereby obtaining a positive electrode material with controllable particle size, thereby controlling the specific surface area of ​​the positive electrode material to 14 m 2 / g~18m 2 / g, so as to improve the processing performance and high-temperature electrochemical performance of the positive electrode material.

[0051] In some embodiments, the temperature of the second sintering treatment is 700°C to 800°C, for example, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, etc., and the time of the second sintering treatment is 8h to 20h, for example, 8h, 10h, 12h, 14h, 16h, 18h, 20h, etc. When the temperature of the second sintering treatment is too low, the first sintering material does not react sufficiently with the second carbon source and the lithium source, and the final carbon coating structure cannot be formed. When the temperature of the second sintering treatment is too high, the effect of improving the crystallinity of the positive electrode material is not obvious, but energy consumption is increased, which is not conducive to cost reduction and efficiency improvement.

[0052] In some embodiments, the temperature of the second sintering treatment is higher than the temperature of the first sintering treatment. The first sintering treatment is a pre-sintering treatment, the main purpose of which is to allow the first carbon source to undergo preliminary carbonization to form a preliminary carbon coating. At this time, part of the main body material will still be exposed, so the temperature of the first sintering treatment needs to be set lower. The second sintering treatment is a high-temperature crystallization sintering step. In this step, a well-crystalline positive electrode material will be formed, and the second carbon source will be carbonized to form a secondary carbon coating, which will further coat the exposed main body material. Therefore, the temperature of the second sintering treatment needs to be set higher.

[0053] In some embodiments, the mass of the second carbon source is greater than or equal to the mass of the first carbon source. Since the carbon coating in the second sintering process is the final coating, the degree of coating determines the quality of the carbon coating layer. Therefore, the mass of the second carbon source is greater than or equal to the mass of the first carbon source. If the mass of the second carbon source is less than the mass of the first carbon source, some of the bulk material may be exposed, which is not conducive to further reducing the specific surface area of ​​the positive electrode material.

[0054] In addition, an embodiment of the present invention further provides a lithium iron manganese phosphate positive electrode material, which is obtained by the preparation method of the lithium iron manganese phosphate positive electrode material of the embodiment of the present invention.

[0055] Due to the use of the preparation method of the embodiment of the present invention, the obtained lithium manganese iron phosphate positive electrode material is a secondary spherical particle formed by the agglomeration of nano-scale primary particles. The specific surface area of ​​the positive electrode material is relatively small, which is 14m 2 / g~18m 2 / g, the positive electrode material has good processing properties and high high-temperature electrochemical performance. Due to the preparation method of the embodiment of the present invention, the obtained lithium manganese iron phosphate positive electrode material has a uniform carbon coating layer, which makes the positive electrode material have good conductivity, thereby further improving the electrochemical performance of the positive electrode material.

[0056] In some embodiments, the median particle size of the secondary particles of the lithium manganese iron phosphate positive electrode material is 2 μm to 15 μm, for example, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc. The particle size of the lithium manganese iron phosphate positive electrode material is controlled within the above range, so that the specific surface area of ​​the positive electrode material can be controlled to 14 m 2 / g~18m 2 / g, so as to improve the processing performance and high-temperature electrochemical performance of the positive electrode material.

[0057] In some embodiments, the lithium iron manganese phosphate cathode material is a secondary spherical particle formed by agglomeration of nanoscale primary particles, and the particle size of the primary particles is less than 100 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc. Due to the small particle size of the single crystal particles, the lithium ion diffusion path is short, thereby ensuring that the cathode material has high capacity and rate performance. When the particle size of the single crystal particles is too large, the capacity and rate performance of the cathode material will be reduced.

[0058] In some embodiments, the lithium manganese iron phosphate cathode material is a core-shell structure, including a core and a carbon coating layer coated on the surface of the core, wherein the core includes Li n Fe x Mn yPO4, 1≤n≤1.1, 0.2≤x≤0.5, x+y=1, and doped with metal elements. The above positive electrode materials have higher high-temperature electrochemical performance.

[0059] In some embodiments, the doping metal element may include but is not limited to at least one of Al, Ti, Mg, Zn, Zr, and V. Doping with the above metal elements can optimize the crystal structure of lithium manganese iron phosphate and improve the material's cycle and rate performance.

[0060] In some embodiments, based on the total mass of the lithium iron manganese phosphate positive electrode material as 100%, the content of the doping metal element is 800ppm to 5000ppm (1wt% = 10000ppm), for example, 800ppm, 1000ppm, 2000ppm, 3000ppm, 4000ppm, 5000ppm, etc. When the content of the doping metal element is too low, it is not conducive to optimizing the positive electrode crystal structure. When the content of the doping metal element is too high, it is not conducive to the full utilization of the specific capacity of the positive electrode material.

[0061] In some embodiments, the carbon coating layer comprises 1% to 3% of the total mass of the lithium manganese iron phosphate cathode material, for example, 1%, 1.5%, 2%, 2.5%, 3%, etc. When the carbon coating layer comprises too little, it is not conducive to improving the conductivity of the cathode material, thereby hindering the electrochemical performance of the battery. When the carbon coating layer comprises too much, it is not conducive to fully utilizing the specific capacity of the cathode material.

[0062] In addition, an embodiment of the present invention further provides a lithium iron manganese phosphate battery, which uses the lithium iron manganese phosphate positive electrode material of the embodiment of the present invention.

[0063] Due to the use of the lithium manganese iron phosphate positive electrode material of the embodiment of the present invention, the lithium manganese iron phosphate battery of the embodiment of the present invention has high high-temperature storage stability and high-temperature cycle stability.

[0064] The present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0065] Example 1

[0066] A method for preparing a lithium manganese iron phosphate positive electrode material, the preparation process is as follows:

[0067] (1) The tap density of 10 kg is 0.8 g / cm 3FePO4, H3PO4, and MnCO3 were dispersed in a certain mass of deionized water at a molar ratio of 0.5:0.5:0.5 with 77g of Al2O3 and 200g of glucose, ensuring that the solid content of the mixture was 30%. The mixture was ground to obtain a first slurry with a solid content of 30%. The median particle size (D50) of the solid material in the first slurry was ≤0.5μm. The first slurry was spray-dried with an air source pressure of 0.3MPa, a peristaltic pump feed frequency of 15Hz, an air inlet temperature of 240°C, and a spray exhaust temperature of 100°C, to obtain a spherical first precursor powder with a D50 of 2μm.

[0068] (2) The first precursor powder was placed in a nitrogen atmosphere and sintered at 500° C. for 20 h to obtain a first sintered material.

[0069] (3) The first sintered material was dispersed with lithium carbonate in a certain mass of deionized water at a molar ratio of (Mn+Fe):Li=1:1, and 200g of glucose was added to ensure that the solid content of the mixture was 30% and ground to obtain a second slurry with a solid content of 30%. The median particle size (D50) of the solid material in the second slurry was 2μm. The second slurry was spray-dried with an air source pressure of 0.3MPa, a peristaltic pump feed frequency of 15Hz, an air inlet temperature of 240°C, and a spray exhaust temperature of 100°C to obtain a spherical second precursor powder with a D50 of 2μm.

[0070] (4) The second precursor powder was placed in a nitrogen atmosphere, sintered at 800 ° C for 8 h, and crushed and demagnetized to obtain a D50 = 2 μm and a specific surface area of ​​18 m 2 / g of spherical lithium manganese iron phosphate positive electrode material, the lithium manganese iron phosphate positive electrode material is a large particle spherical polycrystalline formed by the agglomeration of single crystal particles with a primary particle size of less than 100nm, the lithium manganese iron phosphate positive electrode material is a core-shell structure, the core is Al-doped LiMn 0.5 Fe 0.5 PO4, the core is covered with a carbon coating layer. Based on the total mass of the lithium manganese iron phosphate positive electrode material as 100%, the content of the carbon coating layer is 1%, and the content of the Al element is 800ppm.

[0071] Application Example 1

[0072] A lithium manganese iron phosphate battery, the preparation method is as follows:

[0073] The lithium manganese iron phosphate cathode material of Example 1 was used as a sample, and N-methylpyrrolidone was used as a dispersant. The sample powder was mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 90:5:5 and evenly coated on the surface of a clean aluminum foil, and then blade-coated to form a film. After blast drying, the electrode sheet was obtained, punched into a disc with a diameter of 8 mm, and further dried in a vacuum oven at 120 ° C for 6 h to remove moisture. The prepared electrode sheet was used as the working electrode of the half-cell, metallic lithium was used as the counter electrode, and 1 mol / L LiPF6 / ethylene carbonate (EC)-dimethyl carbonate (DMC) (mass ratio of EC and DMC 1:1) was used as the electrolyte. A lithium-ion battery was assembled in a glove box.

[0074] Example 2

[0075] A method for preparing a lithium manganese iron phosphate positive electrode material, the preparation process is as follows:

[0076] (1) The tap density of 10 kg is 1.64 g / cm 3 FePO4, ammonium monohydrogen phosphate, and manganese oxalate were dispersed in a certain mass of deionized water at a molar ratio of 0.2:0.8:0.8 with 368g of aluminum hydroxide and 600g of polyethylene glycol. The solid content of the mixture was ensured to be 30% and then ground to obtain a first slurry with a solid content of 30%. The median particle size (D50) of the solid material in the first slurry was ≤0.5μm. The first slurry was spray-dried with an air source pressure of 0.6MPa, a peristaltic pump feed frequency of 30Hz, an air inlet temperature of 300°C, and a spray exhaust temperature of 110°C to obtain a spherical first precursor powder with a D50 of 15μm.

[0077] (2) The first precursor powder is placed in a nitrogen atmosphere and sintered at 700° C. for 8 h to obtain a first sintered material.

[0078] (3) The first sintered material was dispersed in a certain mass of deionized water with lithium acetate in a molar ratio of (Mn+Fe):Li=1:1.1, and then 600g of polyethylene glycol was added to ensure that the solid content of the mixture was 50% and ground to obtain a second slurry with a solid content of 50%. The median particle size (D50) of the solid material in the second slurry was 15μm. The second slurry was spray-dried with an air source pressure of 0.6MPa, a peristaltic pump feed frequency of 30Hz, an air inlet temperature of 300°C, and a spray exhaust temperature of 110°C to obtain a spherical second precursor powder with a D50 of 15μm.

[0079] (4) The second precursor powder was placed in a nitrogen atmosphere, sintered at 700 ° C for 20 h, and crushed and demagnetized to obtain D50 = 15m and a specific surface area of ​​14m 2 / g of spherical lithium manganese iron phosphate positive electrode material, the lithium manganese iron phosphate positive electrode material is a large particle spherical polycrystalline formed by the agglomeration of single crystal particles with a primary particle size of less than 100nm, the lithium manganese iron phosphate positive electrode material is a core-shell structure, the core is Al-doped LiMn 0.8 Fe 0.2 PO4, the core is covered with a carbon coating layer. Based on the total mass of the lithium manganese iron phosphate positive electrode material as 100%, the content of the carbon coating layer is 3%, and the content of the Al element is 5000ppm.

[0080] Application Example 2

[0081] The lithium manganese iron phosphate battery of this application embodiment is the same as the lithium manganese iron phosphate battery of application embodiment 1, except that the positive electrode material of embodiment 2 is used.

[0082] Example 3

[0083] A method for preparing a lithium manganese iron phosphate positive electrode material, the preparation process is as follows:

[0084] (1) The tap density of 10 kg is 1.1 g / cm 3 FePO4, ammonium dihydrogen phosphate, and manganese acetate were dispersed in a certain mass of deionized water at a molar ratio of 0.3:0.7:0.7, along with 127g of titanium dioxide and 400g of glucose. The mixture was ground to a solid content of 40% to obtain a first slurry with a solid content of 40%. The median particle size (D50) of the solid material in the first slurry was ≤0.5μm. The first slurry was spray-dried with an air source pressure of 0.4MPa, a peristaltic pump feed frequency of 20Hz, an air inlet temperature of 260°C, and a spray exhaust temperature of 105°C to obtain a spherical first precursor powder with a D50 of 8μm.

[0085] (2) The first precursor powder was placed in a nitrogen atmosphere and sintered at 600° C. for 12 h to obtain a first sintered material.

[0086] (3) The first sintered material was dispersed with lithium hydroxide in a certain mass of deionized water at a molar ratio of (Mn+Fe):Li=1:1.05, and 400g of glucose was added to ensure that the solid content of the mixture was 40% and ground to obtain a second slurry with a solid content of 40%. The median particle size (D50) of the solid material in the second slurry was 8μm. The second slurry was spray-dried with an air source pressure of 0.4MPa, a peristaltic pump feed frequency of 20Hz, an air inlet temperature of 260°C, and a spray exhaust temperature of 105°C to obtain a spherical second precursor powder with a D50 of 8μm.

[0087] (4) The second sintered precursor powder was placed in a nitrogen atmosphere, sintered at 750 ° C for 12 h, and crushed and demagnetized to obtain a D50 = 8 μm and a specific surface area of ​​15 m 2 / g of spherical lithium manganese iron phosphate positive electrode material, the lithium manganese iron phosphate positive electrode material is a large particle spherical polycrystalline formed by the agglomeration of single crystal particles with a primary particle size of less than 100nm, the lithium manganese iron phosphate positive electrode material is a core-shell structure, the core is Ti-doped LiMn 0.7 Fe 0.3 PO4, the core is covered with a carbon coating layer. Based on the total mass of the lithium manganese iron phosphate positive electrode material as 100%, the content of the carbon coating layer is 2%, and the content of the Ti element is 3000ppm.

[0088] Application Example 3

[0089] The lithium manganese iron phosphate battery of this application embodiment is the same as the lithium manganese iron phosphate battery of application embodiment 1, except that the positive electrode material of embodiment 3 is used.

[0090] Example 4

[0091] A method for preparing a lithium manganese iron phosphate positive electrode material is the same as the preparation method of Example 1, except that Al2O3, MnCO3, lithium carbonate, and glucose are replaced by magnesium oxide, manganese dioxide, lithium phosphate, and trimesic acid, respectively, and the core of the obtained lithium manganese iron phosphate positive electrode material is Mg-doped LiMn 0.5 Fe 0.5 PO4.

[0092] Application Example 4

[0093] The lithium manganese iron phosphate battery of this application embodiment is the same as the lithium manganese iron phosphate battery of application embodiment 1, except that the positive electrode material of embodiment 4 is used.

[0094] Example 5

[0095] The preparation method of this embodiment is the same as that of Example 1, except that the mass of glucose added in step (1) is 100 g, and the mass of glucose added in step (3) is changed to 300 g.

[0096] Application Example 5

[0097] The lithium manganese iron phosphate battery of the comparative example is the same as the lithium manganese iron phosphate battery of example 1, except that the positive electrode material of example 5 is used.

[0098] Example 6

[0099] The preparation method of this embodiment is the same as that of Example 1, except that the mass of glucose added in step (1) is 240 g, and the mass of glucose added in step (3) is changed to 160 g.

[0100] Application Example 6

[0101] The lithium manganese iron phosphate battery of this application embodiment is the same as the lithium manganese iron phosphate battery of application embodiment 1, except that the positive electrode material of embodiment 6 is used.

[0102] Example 7

[0103] The preparation method of this embodiment is the same as that of Example 1, except that during the first slurry grinding process, the median particle size of the solid material is controlled to be 0.5 μm ≤ (D50) ≤ 1 μm. The lithium manganese iron phosphate positive electrode material is a large spherical polycrystalline formed by the agglomeration of single crystal particles with a primary particle size of 200-300 nm.

[0104] Application Example 7

[0105] The lithium manganese iron phosphate battery of this application embodiment is the same as the lithium manganese iron phosphate battery of application embodiment 1, except that the positive electrode material of embodiment 7 is used.

[0106] Comparative Example 1

[0107] A method for preparing a lithium manganese iron phosphate positive electrode material, the preparation process is as follows:

[0108] (1) The tap density of 10 kg is 0.8 g / cm 3 FePO4, H3PO4, and MnCO3 were dispersed in a predetermined mass of deionized water at a molar ratio of 0.5:0.5:0.5, along with 77g of Al2O3 and 200g of glucose. The mixture was ground to a solids content of 30% to obtain a first slurry having a solids content of 30%. The solid material in the first slurry had a median particle size (D50) of 0.5 μm or less. The first slurry was stirred and evaporated to dryness to obtain a first precursor powder having a median particle size (D50) of 0.5 μm or less.

[0109] (2) The first precursor powder was placed in a nitrogen atmosphere and sintered at 500° C. for 20 h to obtain a first sintered material.

[0110] (3) The first sintered material was dispersed with lithium carbonate in a certain mass of deionized water at a molar ratio of (Mn+Fe):Li=1:1, and 200 g of glucose was added to ensure that the solid content of the mixture was 30% and then ground to obtain a second slurry with a solid content of 30%. The median particle size (D50) of the solid material in the second slurry was ≤0.5 μm. The second slurry was stirred and evaporated to dryness to obtain a second precursor powder with a median particle size (D50) ≤0.5 μm.

[0111] (4) The second precursor powder was placed in a nitrogen atmosphere, sintered at 800 ° C for 8 h, and crushed and demagnetized to obtain a median particle size (D50) of 0.8 μm and a specific surface area of ​​21 m 2 / g non-spherical lithium manganese iron phosphate positive electrode material, the lithium manganese iron phosphate positive electrode material is a core-shell structure, the core is non-spherical Al-doped LiMn 0.5 Fe 0.5 PO4, the core is covered with a carbon coating layer. Based on the total mass of the lithium manganese iron phosphate positive electrode material as 100%, the content of the carbon coating layer is 1%, and the content of the Al element is 800ppm.

[0112] Comparative Application Example 1

[0113] The lithium manganese iron phosphate battery of the comparative example is the same as the lithium manganese iron phosphate battery of the embodiment 1, except that the positive electrode material of the comparative example 1 is used.

[0114] Comparative Example 2

[0115] A method for preparing a lithium manganese iron phosphate positive electrode material, the preparation process is as follows:

[0116] (1) The tap density of 10 kg is 0.8 g / cm 3 FePO4, H3PO4, and MnCO3 were dispersed in a predetermined mass of deionized water at a molar ratio of 0.5:0.5:0.5, along with 77g of Al2O3 and 200g of glucose. The mixture was ground to a solids content of 30% to obtain a first slurry having a solids content of 30%. The solid material in the first slurry had a median particle size (D50) of 0.5 μm or less. The first slurry was stirred and evaporated to dryness to obtain a first precursor powder having a median particle size (D50) of 0.5 μm or less.

[0117] (2) The first precursor powder was placed in a nitrogen atmosphere and sintered at 500° C. for 20 h to obtain a first sintered material.

[0118] (3) The first sintered material was dispersed with lithium carbonate in a certain mass of deionized water at a molar ratio of (Mn+Fe):Li=1:1, and then 200g of glucose was added to ensure that the solid content of the mixed solution was 30% and ground to obtain a second slurry with a solid content of 30%. The median particle size (D50) of the solid material in the second slurry was ≤0.5μm. The second slurry was spray-dried, and the air source pressure of the spray equipment was 0.3MPa, the feed frequency of the peristaltic pump was 15Hz, the inlet air temperature was 240℃, and the exhaust air temperature of the spray was 100℃, to obtain a spherical second precursor powder with D50=2μm.

[0119] (4) The second precursor powder was placed in a nitrogen atmosphere, sintered at 800 ° C for 8 h, and crushed and demagnetized to obtain a median particle size (D50) of 2 μm and a specific surface area of ​​20 m 2 / g of spherical lithium manganese iron phosphate positive electrode material, the lithium manganese iron phosphate positive electrode material is a core-shell structure, the core is spherical Al-doped LiMn 0.5 Fe 0.5 PO4, the core is covered with a carbon coating layer. Based on the total mass of the lithium manganese iron phosphate positive electrode material as 100%, the content of the carbon coating layer is 1%, and the content of the Al element is 800ppm.

[0120] Application Comparative Example 2

[0121] The lithium manganese iron phosphate battery of the comparative example is the same as the lithium manganese iron phosphate battery of the embodiment 1, except that the positive electrode material of the comparative example 2 is used.

[0122] Comparative Example 3

[0123] A method for preparing a lithium manganese iron phosphate positive electrode material, the preparation process is as follows:

[0124] (1) The tap density of 10 kg is 0.8 g / cm 3 FePO4, H3PO4, and MnCO3 were dispersed in a certain mass of deionized water at a molar ratio of 0.5:0.5:0.5, along with 800 ppm of Al2O3 and 400 g of glucose. The mixture was ground to a solid content of 30% to obtain a first slurry with a solid content of 30%. The median particle size (D50) of the solid material in the first slurry was ≤ 0.5 μm. The first slurry was spray-dried with an air source pressure of 0.3 MPa, a peristaltic pump feed frequency of 15 Hz, an air inlet temperature of 240°C, and a spray exhaust temperature of 100°C to obtain a spherical first precursor powder with a D50 of 2 μm.

[0125] (2) The first precursor powder was placed in a nitrogen atmosphere and sintered at 500° C. for 20 h to obtain a first sintered material.

[0126] (3) The first sintered material was dispersed with lithium carbonate in a certain mass of deionized water at a molar ratio of (Mn+Fe):Li=1:1, ensuring that the solid content of the mixed solution was 30% and then ground to obtain a second slurry with a solid content of 30%. The median particle size (D50) of the solid material in the second slurry was 2 μm. The second slurry was spray-dried with an air source pressure of 0.3 MPa, a peristaltic pump feed frequency of 15 Hz, an air inlet temperature of 240°C, and a spray exhaust temperature of 100°C to obtain a spherical second precursor powder with a D50 of 2 μm.

[0127] (4) The second precursor powder was placed in a nitrogen atmosphere, sintered at 800 ° C for 8 h, and crushed and demagnetized to obtain a D50 = 2 μm and a specific surface area of ​​15 m 2 / g spherical manganese iron phosphate lithium positive electrode material, the manganese iron phosphate lithium positive electrode material is a core-shell structure, the core is Al-doped LiMn 0.5 Fe 0.5 PO4, the core is covered with a carbon coating layer. Based on the total mass of the lithium manganese iron phosphate positive electrode material as 100%, the content of the carbon coating layer is 1%, and the content of the Al element is 800ppm.

[0128] Application Comparative Example 3

[0129] The lithium manganese iron phosphate battery of the comparative example is the same as the lithium manganese iron phosphate battery of the embodiment 1, except that the positive electrode material of the comparative example 3 is used.

[0130] Comparative Example 4

[0131] The preparation method of this comparative example is the same as that of Example 1, except that lithium carbonate is added in step (1).

[0132] Comparative Application Example 4

[0133] The lithium manganese iron phosphate battery of the comparative example is the same as the lithium manganese iron phosphate battery of the embodiment 1, except that the positive electrode material of the comparative example 4 is used.

[0134] Performance test: The batteries of application examples 1 to 7 and application comparative examples 1 to 4 were subjected to charge and discharge tests in the voltage range of 3V to 4.3V. The room temperature charge and discharge current densities were 0.1C, 1C, and 4C. The high temperature cycle was 45°C and 1C for 300 cycles. The performance test results are shown in Table 1.

[0135] Table 1. Electrical properties of the positive electrode materials of various embodiments and comparative examples

[0136]

[0137] Table 1 compares the specific surface area and electrochemical performance of the positive electrode materials of Examples 1 to 7 and Comparative Examples 1 to 4. As can be seen from Table 1, the specific surface areas of Examples 1 to 4 are significantly lower than those of Comparative Examples 1 to 3, while the capacity, rate capability, and cycle performance are significantly higher than those of Comparative Examples 1 to 3.

[0138] The difference between Example 5 and Example 1 is that in Example 1, the mass of the second carbon source is equal to the mass of the first carbon source, while in Example 5, the mass of the second carbon source is greater than the mass of the first carbon source. From the comparison between Example 1 and Example 5, it can be seen that when the mass of the second carbon source is greater than the mass of the first carbon source, the rate performance and cycle performance of the positive electrode material can be improved to a certain extent.

[0139] The difference between Example 6 and Example 1 is that in Example 1, the mass of the second carbon source is equal to the mass of the first carbon source, while in Example 6, the mass of the second carbon source is less than the mass of the first carbon source. From the comparison of Example 1 and Example 6, it can be seen that when the mass of the second carbon source is less than the mass of the first carbon source, the capacity, rate capability, and cycle performance of the positive electrode material will be reduced to a certain extent.

[0140] The difference between Example 7 and Example 1 is that the lithium iron manganese phosphate positive electrode material in Example 1 is a large spherical polycrystal formed by the agglomeration of single crystal particles with a primary particle size of less than 100 nm, while the lithium iron manganese phosphate positive electrode material in Example 7 is a large spherical polycrystal formed by the agglomeration of single crystal particles with a primary particle size of 200 nm to 300 nm. A comparison of Examples 1 and 7 shows that when the particle size of the positive electrode material primary particles increases, the capacity, rate capability, and cycle performance of the positive electrode material are reduced to a certain extent.

[0141] In Comparative Example 1, steps (1) and (3) were not subjected to spraying treatment, and the obtained lithium manganese iron phosphate positive electrode material was non-spherical particles, and the secondary particle median diameter was smaller than that of Example 1, and the specific surface area was larger than that of Example 1. From the comparison of Example 1 and Comparative Example 1 in Table 1, it can be seen that the capacity, rate and cycle performance of the lithium manganese iron phosphate positive electrode material of Comparative Example 1 are significantly lower than those of Example 1.

[0142] In comparative example 2, step (1) is not subjected to spraying treatment, and only one spraying treatment is performed in step (3), and the median particle size (D50) of the solid material in the second slurry is ≤0.5 μm. From the comparison of Example 1 and comparative example 2 in Table 1, it can be seen that although comparative example 2 can also achieve the purpose of preparing spherical particles by only one spraying in step (3), the material properties will be affected. The reason is that when step (1) in comparative example 2 does not use spraying treatment to granulate, forming small particles of the carbon-coated first sintered material, the carbon layer is easily ground and fallen off during the second grinding process, affecting the coating effect; while the spherical carbon-coated first sintered material powder of Example 1 has a smaller specific surface area, and most of the carbon layer exists inside the spherical particles, and there is no risk of grinding and falling off.

[0143] In comparative example 3, carbon coating is performed only once in step (1). From the comparison between Example 1 and comparative example 3, it can be seen that although the total amount of carbon coating in comparative example 3 is the same as that in Example 1, the material properties will be affected. The reason is that: in Example 1, the first sintering treatment is pre-firing, the main purpose of which is to allow the carbon source to undergo preliminary carbonization to form a carbon coating layer. At this time, part of the main body material will still be exposed, and the specific surface area is relatively high; the second sintering treatment is the second carbon coating, which will further coat the exposed main body material, thereby achieving the purpose of reducing the specific surface area. Therefore, the specific surface area of ​​the positive electrode material obtained by carbon coating twice in Example 1 is smaller than that of the positive electrode material obtained by coating all the carbon materials at one time in comparative example 3.

[0144] In Comparative Example 4, lithium carbonate is added in step (1). A comparison between Example 1 and Comparative Example 4 shows that changing the order of lithium salt addition in Comparative Example 4 reduces the performance of the positive electrode material to a certain extent. Furthermore, lithium carbonate is relatively expensive and is typically added before the final high-temperature sintering step. Adding it too early results in losses in subsequent steps, increasing costs.

[0145] Figure 1 This is a scanning electron microscope image of the positive electrode material prepared in Example 1 of the present invention. It is found that the positive electrode material is secondary spherical particles formed by the agglomeration of nanometer-scale primary particles. Figure 2 This is a scanning electron microscope image of the positive electrode material prepared in Comparative Example 1, which shows that the positive electrode material is non-spherical particles.

[0146] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0147] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a lithium manganese iron phosphate positive electrode material, characterized in that: The steps include: (1) dispersing an iron source, a phosphorus source, a manganese source, a first carbon source, and an ion dopant in a dispersant to obtain a first mixed liquid, performing a first grinding process on the first mixed liquid to obtain a first slurry, and performing a first spraying process on the first slurry to obtain a spherical first precursor powder; (2) performing a first sintering treatment on the first precursor powder under a nitrogen atmosphere to obtain a first sintered material; (3) dispersing the first sintered material, a second carbon source, and a lithium source in a dispersant to obtain a second mixed solution, grinding the second mixed solution a second time to obtain a second slurry, and spraying the second slurry a second time to obtain a spherical second precursor powder; (4) The second precursor powder is subjected to a second sintering treatment in a nitrogen atmosphere to obtain a second sintered material, and the second sintered material is subjected to a crushing treatment and a demagnetization treatment to obtain a spherical lithium manganese iron phosphate positive electrode material.

2. The method for preparing the lithium manganese iron phosphate positive electrode material according to claim 1, wherein: The solid content of the first slurry and the second slurry is 30% to 50%.

3. The method for preparing the lithium manganese iron phosphate positive electrode material according to claim 1, characterized in that: The median particle size of the solid material in the first slurry is less than or equal to 0.5 μm; and / or the median particle size of the solid material in the second slurry is 2 μm to 15 μm.

4. The method for preparing the lithium manganese iron phosphate positive electrode material according to claim 1, characterized in that: The air source pressure of the spray equipment used in the first spray treatment and the second spray treatment is 0.3MPa~0.6MPa, the feeding frequency of the peristaltic pump of the spray equipment is 15Hz~30Hz, the air inlet temperature of the spray equipment is 240℃~300℃, and the exhaust temperature of the spray equipment is 100℃~110℃.

5. The method for preparing the lithium manganese iron phosphate positive electrode material according to claim 1, characterized in that: The median particle size of the first precursor powder is 2 μm to 15 μm; and / or the median particle size of the second precursor powder is 2 μm to 15 μm.

6. The method for preparing the lithium manganese iron phosphate positive electrode material according to any one of claims 1 to 5, characterized in that: The temperature of the first sintering treatment is 500° C. to 700° C., and the time of the first sintering treatment is 8 hours to 20 hours; and / or the temperature of the second sintering treatment is 700° C. to 800° C., and the time of the second sintering treatment is 8 hours to 20 hours.

7. The method for preparing the lithium manganese iron phosphate positive electrode material according to any one of claims 1 to 5, characterized in that: The mass of the second carbon source is greater than or equal to the mass of the first carbon source.

8. A lithium manganese iron phosphate positive electrode material, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 7.

9. The lithium iron manganese phosphate positive electrode material according to claim 8, characterized in that The lithium manganese iron phosphate cathode material is a secondary spherical particle formed by agglomeration of nanometer-scale primary particles, and the particle size of the primary particles is less than 100 nm; and / or, the lithium manganese iron phosphate cathode material comprises a core and a carbon coating layer coated on the surface of the core, and the core comprises Li n Fe x Mn y PO4, 1≤n≤1.1, 0.2≤x≤0.5, x+y=1, and doped metal elements; based on the total mass of the lithium manganese iron phosphate positive electrode material as 100%, the content of the doped metal elements is 800ppm~5000ppm, and the content of the carbon coating layer is 1%~3%.

10. A lithium manganese iron phosphate battery, characterized in that: The lithium manganese iron phosphate positive electrode material according to claim 8 is used.

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