Lithium iron manganese phosphate material, preparation method and application

Abstract

The application discloses a lithium manganese iron phosphate material, a preparation method and application. In the lithium manganese iron phosphate material, a polyurethane polymer is introduced into a coating layer of the lithium manganese iron phosphate material. On one hand, the polyurethane polymer can reduce the contact between the material and electrolyte, thereby reducing the occurrence of a side reaction, and is beneficial to reducing the dissolution of manganese in the lithium manganese iron phosphate material, thereby being beneficial to prolonging the cycle stability and cycle life of the material. On the other hand, the polyurethane polymer has certain deformability and toughness, and application of the polyurethane polymer to the coating layer is beneficial to improving the stability of the lithium manganese iron phosphate structure.

Description

Technical Field

[0001] This invention relates to the field of cathode material technology, and more specifically, to lithium manganese iron phosphate material, its preparation method, and its application. Background Technology

[0002] Lithium manganese iron phosphate (LiMn) x Fe (1-x) Lithium manganese iron phosphate (LiFePO4) shares the same olivine structure as lithium iron phosphate (LiFePO4) and is expected to be widely used in power batteries. However, under high-temperature conditions, Mn in lithium manganese iron phosphate materials is easily dissolved from the material, leading to capacity decay and shortened cycle life during high-temperature cycling.

[0003] Existing methods for suppressing manganese leaching from lithium manganese iron phosphate (LFP) materials include improving the preparation method of LFP materials, changing the electrolyte composition, and surface coating of LFP materials. However, these methods still have some problems. First, improving the preparation method of LFP materials or changing the electrolyte composition may affect other battery performance aspects, such as energy density and power density. Second, although surface coating can improve the compatibility between LFP materials and electrolytes, existing coating materials such as alumina and titanium dioxide have limited improvement effects and may increase battery costs.

[0004] In summary, how to effectively improve the side reactions between lithium manganese iron phosphate materials and electrolytes, and enhance the cycle performance and safety performance of batteries, without changing the preparation method of lithium manganese iron phosphate materials and electrolyte composition, is a major challenge currently facing the technology. Summary of the Invention

[0005] The purpose of this invention is to provide lithium manganese iron phosphate materials, preparation methods, and applications, thereby improving the cycle stability and cycle life of lithium manganese iron phosphate materials.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a lithium manganese iron phosphate material, comprising lithium manganese iron phosphate and a polyurethane protective layer disposed on the surface of the lithium manganese iron phosphate.

[0008] In an optional embodiment, the mass fraction of the polyurethane protective layer in the lithium manganese iron phosphate material is 0.008%-0.5%.

[0009] In a second aspect, the present invention provides a lithium manganese iron phosphate material, the method comprising: mixing polyurethane, solvent and lithium manganese iron phosphate powder to obtain a mixture, and then removing the solvent from the mixture to obtain the lithium manganese iron phosphate material.

[0010] In an optional embodiment, the average particle size of the lithium manganese iron phosphate is 0.8 μm-1.2 μm;

[0011] And / or, the polyurethane protective layer is a nano-polyurethane protective layer.

[0012] And / or, before the lithium manganese iron phosphate powder is mixed with the polyurethane solution, surface free carbon is removed.

[0013] In an optional embodiment, the mass fraction of polyurethane in the mixture is 2%-8%.

[0014] And / or, the solvent is N-dimethylformamide;

[0015] And / or, removing the solvent from the mixture includes: first pre-drying the mixture, and then vacuum drying it at 100℃-120℃ for 10h-12h to obtain the lithium manganese iron phosphate material;

[0016] And / or, before the lithium manganese iron phosphate powder is mixed with polyurethane and solvent, surface free carbon is removed.

[0017] In an optional embodiment, the method further includes the synthesis of polyurethane:

[0018] Prepolymerization is carried out by reacting polypropylene glycol and 2,4-toluene diisocyanate under an inert atmosphere to obtain a polyurethane prepolymer;

[0019] Polymerization is carried out by mixing the polyurethane prepolymer with diethylene glycol to obtain a mixture, and then reacting the mixture under vacuum conditions to obtain polyurethane.

[0020] In an optional embodiment, the mass ratio of the polypropylene glycol to 2,4-toluene diisocyanate is 1:(2-2.5);

[0021] And / or, the molecular weight of the polypropylene glycol is 1500-2500;

[0022] And / or, the temperature of the prepolymerization reaction is 80℃-100℃, and the time is 2h-4h.

[0023] In an optional embodiment, the mass ratio of diethylene glycol to polypropylene glycol is 1:(0.9-1.1);

[0024] And / or, the polymerization reaction is carried out at a temperature of 100℃-120℃ for a time of 10h-12h.

[0025] Thirdly, the present invention provides a positive electrode sheet comprising the lithium manganese iron phosphate material described in the foregoing embodiments.

[0026] Fourthly, the present invention provides a lithium-ion battery, including the positive electrode sheet described in the foregoing embodiments.

[0027] The present invention has the following beneficial effects:

[0028] In this invention, polyurethane polymer is introduced into the coating layer of lithium manganese iron phosphate. On the one hand, this can reduce the contact between the material and the electrolyte, thereby reducing the occurrence of side reactions and reducing the dissolution of manganese in the lithium manganese iron phosphate material, thus helping to extend the cycle stability and cycle life of the material. On the other hand, polyurethane has certain deformability and toughness, and its application in the coating layer helps to improve the stability of the lithium manganese iron phosphate structure. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The following describes the manganese leaching of the cathode materials prepared in some embodiments and comparative examples of the present invention;

[0031] Figure 2 The cycling curves of the cathode materials prepared in some embodiments and comparative examples of the present invention are shown. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] This invention provides a lithium manganese iron phosphate material, comprising lithium manganese iron phosphate and a polyurethane protective layer disposed on the surface of the lithium manganese iron phosphate, wherein the mass fraction of the polyurethane protective layer in the lithium manganese iron phosphate material is 0.008%-0.5%.

[0034] In this embodiment of the invention, polyurethane polymer is introduced into the coating layer of lithium manganese iron phosphate. On the one hand, this can reduce the contact between the material and the electrolyte, thereby reducing the occurrence of side reactions and reducing the dissolution of manganese in the lithium manganese iron phosphate material, thus helping to extend the cycle stability and cycle life of the material. On the other hand, polyurethane has certain deformability and toughness, and its application in the coating layer is beneficial to improving the stability of the lithium manganese iron phosphate structure.

[0035] In this embodiment of the invention, the mass fraction of the polyurethane protective layer in the lithium manganese iron phosphate material is 0.008%-0.5%, specifically, it can be any value between 0.01%, 0.03%, 0.05%, 0.1%, 0.01%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.01%-0.5%. Excessive polyurethane usage gradually reduces its effect on improving the cycle stability and cycle life of the lithium manganese iron phosphate material.

[0036] The present invention also provides a method for preparing lithium manganese iron phosphate material, the method comprising: mixing polyurethane, solvent and lithium manganese iron phosphate powder to obtain a mixture, and then removing the solvent from the mixture to obtain the lithium manganese iron phosphate material.

[0037] When polyurethane is prepared into a solution and then mixed with lithium manganese iron phosphate powder, the presence of the solvent makes it easier for polyurethane to form a uniform film on the surface of lithium manganese iron phosphate.

[0038] In an optional embodiment, the mass fraction of polyurethane in the mixture is 2%-8%, specifically any value between 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 2%-8%. The concentration of the polyurethane solution is related to its viscosity. If the polyurethane concentration is too high, it is not conducive to the uniform film formation of polyurethane on the lithium manganese iron phosphate surface; if the polyurethane concentration is too low, the energy required for subsequent solvent removal will be too high.

[0039] In an optional embodiment, the average particle size of the lithium manganese iron phosphate is 0.8 μm-1.2 μm;

[0040] In an optional embodiment, the polyurethane protective layer is a nano-polyurethane protective layer with a thinner thickness, which can improve cycle performance while reducing the impact on capacity and lithium-ion migration.

[0041] In an optional embodiment, the solvent is N-dimethylformamide.

[0042] In an optional embodiment, removing the solvent from the mixture includes: first pre-drying the mixture, and then vacuum drying it at 100℃-120℃ for 10h-12h to obtain the lithium manganese iron phosphate material.

[0043] The purpose of preliminary drying is to remove most of the solvent. In some embodiments, preliminary drying is accompanied by stirring, which helps to improve the uniformity of the polyurethane protective layer. The temperature of preliminary drying only needs to be sufficient to evaporate the solvent, for example, 60-80°C. Vacuum drying is beneficial to improve drying efficiency, and the vacuum environment can also avoid the influence of water and oxygen on lithium manganese iron phosphate.

[0044] It should be noted that because lithium manganese iron phosphate readily reacts with water and oxygen, the introduction or contact of water and oxygen should be avoided as much as possible throughout the process. Therefore, in some embodiments, before vacuum drying the dried material, the vacuum oven is purged with nitrogen to minimize the impact of residual water or oxygen in the oven on the material.

[0045] In an optional embodiment, the surface free carbon of the lithium manganese iron phosphate powder is removed before mixing it with polyurethane and solvent. The presence of free carbon facilitates side reactions in the material, thereby affecting its cycle performance; therefore, free carbon is removed before coating.

[0046] In an optional embodiment, the method further includes the synthesis of polyurethane:

[0047] Prepolymerization involves reacting polypropylene glycol (PPG) and 2,4-toluene diisocyanate (2,4-TDI) under an inert atmosphere to obtain a polyurethane prepolymer.

[0048] Polymerization is carried out by mixing the polyurethane prepolymer with diethylene glycol (DEG) to obtain a mixture, and then reacting the mixture under vacuum conditions to obtain polyurethane.

[0049] In an optional embodiment, the mass ratio of the polypropylene glycol to 2,4-toluene diisocyanate is 1:(2-2.5).

[0050] In an optional embodiment, the molecular weight of the polypropylene glycol is 1500-2500.

[0051] In an optional embodiment, the temperature of the prepolymerization reaction is 80℃-100℃ and the time is 2h-4h.

[0052] In an optional embodiment, the mass ratio of diethylene glycol to polypropylene glycol is 1:(0.9-1.1).

[0053] In an optional embodiment, the polymerization reaction is carried out at a temperature of 100°C-120°C for 10-12 hours.

[0054] During the polyurethane synthesis process, the degree of polymerization of polyurethane has a significant impact on the cycle performance of lithium manganese iron phosphate materials. In this application, in order to improve the cycle performance of the material, the polymerization time and temperature are appropriately adjusted to increase the degree of polymerization.

[0055] The present invention also provides a positive electrode sheet comprising the lithium manganese iron phosphate material described in the foregoing embodiments.

[0056] This invention also provides a lithium-ion battery, including the positive electrode sheet described in the foregoing embodiments.

[0057] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0058] Example 1:

[0059] This embodiment provides a method for preparing lithium manganese iron phosphate material, specifically including the following steps:

[0060] 1. LiMn 0.6 Fe 0.4 PO4 particles were added to anhydrous ethanol solution and ultrasonically cleaned for 2 hours to remove uncoated free carbon. The powder was then baked in a vacuum drying oven at 120°C for 12 hours and then ground in a ball mill for 6 hours to obtain lithium manganese iron phosphate material.

[0061] 2. PPG-2K (average molecular weight 2000) and 2,4-TDI were added to a reaction vessel, filled with nitrogen, sealed, heated, and magnetically stirred (80℃, 2h). After the reaction was completed, a polyurethane prepolymer was obtained.

[0062] 3. Add diethylene glycol to the polyurethane prepolymer obtained in step 2, stir evenly, pour into a mold, and react (100℃, 10h) to obtain polyurethane (PU), wherein the molar ratio of PPG-2K, 2,4-TDI and diethylene glycol is 1:2.2:1.

[0063] 4. Dissolve 0.5 mg of PU in 25 mL of N-dimethylformamide and stir to obtain a homogeneous PU solution. Then, disperse 1000 mg of LMFP powder from step 1 into the PU solution to obtain LMFP-PU with a PU nanolayer. Stir the mixture at 20 °C for 2 hours. Finally, collect the LMFP-PU powder by evaporation and vacuum dry it at 100 °C for 10 hours to obtain the PU-coated LMFP material. Labeled as LMFP-PU1.

[0064] Example 2:

[0065] This embodiment provides a method for preparing lithium manganese iron phosphate material, which differs from Embodiment 1 only in that the PU content in step 4 is different. Specifically, it includes the following steps:

[0066] 1. LiMn 0.6 Fe 0.4 PO4 particles were added to anhydrous ethanol solution and ultrasonically cleaned for 2 hours to remove uncoated free carbon. The particles were then baked in a vacuum drying oven at 100°C for 12 hours. The resulting powder was then ground in a ball mill for 6 hours to obtain lithium manganese iron phosphate material.

[0067] 2. PPG-2K and 2,4-TDI were added to a reaction vessel, filled with nitrogen, sealed, heated, and magnetically stirred (80℃, 2h). After the reaction was completed, a polyurethane prepolymer was obtained.

[0068] 3. Add diethylene glycol to the polyurethane prepolymer obtained in step 2, stir evenly, pour into a mold, and react (100℃, 10h) to obtain polyurethane (PU), wherein the molar ratio of PPG-2K, 2,4-TDI and diethylene glycol is 1:2.2:1.

[0069] 4. Dissolve 1 mg of PU in 25 mL of N-dimethylformamide and stir to obtain a homogeneous PU solution. Then, disperse 1000 mg of LMFP powder from step 1 into the PU solution to obtain LMFP-PU with a PU nanolayer. Stir the mixture at 20 °C for 2 hours. Finally, collect the LMFP-PU powder by evaporation and vacuum dry it at 100 °C for 10 hours to obtain the PU-coated LMFP material, labeled as LMFP-PU2.

[0070] Example 3:

[0071] This embodiment provides a method for preparing lithium manganese iron phosphate material, which differs from Embodiment 1 only in that the PU content in step 4 is different. Specifically, it includes the following steps:

[0072] 1. LiMn 0.6 Fe 0.4 PO4 particles were added to anhydrous ethanol solution and ultrasonically cleaned for 2 hours to remove uncoated free carbon. The particles were then baked in a vacuum drying oven at 100°C for 12 hours. The resulting powder was then ground in a ball mill for 6 hours to obtain lithium manganese iron phosphate material.

[0073] 2. PPG-2K and 2,4-TDI were added to a reaction vessel, filled with nitrogen, sealed, heated, and magnetically stirred (80℃, 2h). After the reaction was completed, a polyurethane prepolymer was obtained.

[0074] 3. Add diethylene glycol to the polyurethane prepolymer obtained in step 2, stir evenly, pour into a mold, and react (100℃, 10h) to obtain polyurethane (PU), wherein the molar ratio of PPG-2K, 2,4-TDI and diethylene glycol is 1:2.2:1.

[0075] 4. Dissolve 2 mg of PU in 25 mL of N-dimethylformamide and stir to obtain a homogeneous PU solution. Then, disperse 1000 mg of LMFP powder from step 1 into the PU solution to obtain LMFP-PU with a PU nanolayer. Stir the mixture at 20 °C for 2 hours. Finally, collect the LMFP-PU powder by evaporation and vacuum dry it at 100 °C for 10 hours to obtain the PU-coated LMFP material. Labeled as LMFP-PU3.

[0076] Example 4

[0077] This embodiment provides a method for preparing lithium manganese iron phosphate material, which differs from Example 1 only in the degree of polymerization of PU. The method specifically includes the following steps:

[0078] 1. LiMn 0.6 Fe 0.4 PO4 particles were added to anhydrous ethanol solution and ultrasonically cleaned for 2 hours to remove uncoated free carbon. The particles were then baked in a vacuum drying oven at 100°C for 12 hours. The resulting powder was then ground in a ball mill for 6 hours to obtain lithium manganese iron phosphate material.

[0079] 2. PPG-2K (average molecular weight 2000) and 2,4-TDI were added to a reaction vessel, filled with nitrogen, sealed, heated, and magnetically stirred (60℃, 1h). After the reaction was completed, a polyurethane prepolymer was obtained.

[0080] 3. Add diethylene glycol to the polyurethane prepolymer obtained in step 2, stir evenly, pour into a mold, and react (80℃, 8h) to obtain polyurethane (PU), wherein the molar ratio of PPG-2K, 2,4-TDI and diethylene glycol is 1:2.2:1.

[0081] 4. Dissolve 0.5 mg of PU in 25 mL of N-dimethylformamide and stir to obtain a homogeneous PU solution. Then, disperse 1000 mg of LMFP powder from step 1 into the PU solution to obtain LMFP-PU with a PU nanolayer. Stir the mixture at 20 °C for 2 hours. Finally, collect the LMFP-PU powder by evaporation and vacuum dry it at 100 °C for 10 hours to obtain the PU-coated LMFP material. Labeled as LMFP-PU4.

[0082] Example 5

[0083] This embodiment provides a method for preparing lithium manganese iron phosphate material, which differs from Example 1 only in the degree of polymerization of PU. The method specifically includes the following steps:

[0084] 1. LiMn 0.6 Fe 0.4PO4 particles were added to anhydrous ethanol solution and ultrasonically cleaned for 2-4 hours to remove uncoated free carbon. The powder was then baked in a vacuum drying oven at 100°C for 12 hours and then ground in a ball mill for 6 hours to obtain lithium manganese iron phosphate material.

[0085] 2. PPG-2K (average molecular weight 2000) and 2,4-TDI were added to a reaction vessel, filled with nitrogen, sealed, heated, and magnetically stirred (120℃, 1h). After the reaction was completed, a polyurethane prepolymer was obtained.

[0086] 3. Add diethylene glycol to the polyurethane prepolymer obtained in step 2, stir evenly, pour into a mold, and react (150℃, 14h) to obtain polyurethane (PU), wherein the molar ratio of PPG-2K, 2,4-TDI and diethylene glycol is 1:2.2:1.

[0087] 4. Dissolve 0.5 mg of PU in 25 mL of N-dimethylformamide and stir to obtain a homogeneous PU solution. Then, disperse 1000 mg of LMFP powder from step 1 into the PU solution to obtain LMFP-PU with a PU nanolayer. Stir the mixture at 20 °C for 2 hours. Finally, collect the LMFP-PU powder by evaporation and vacuum dry it at 100 °C for 10 hours to obtain the PU-coated LMFP material. Labeled as LMFP-PU5.

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing lithium manganese iron phosphate material, which differs from Example 1 only in that it is not coated with PU. The method specifically includes the following steps:

[0090] 1. LiMn 0.6 Fe 0.4 PO4 particles were added to anhydrous ethanol solution and ultrasonically cleaned for 2 hours to remove uncoated free carbon.

[0091] 2. The solution obtained in step 1 is baked in a vacuum drying oven at 100℃ for 12 hours, and the resulting powder is ground in a ball mill for 6-8 hours to obtain lithium manganese iron phosphate material.

[0092] Comparative Example 2

[0093] This comparative example provides a method for preparing lithium manganese iron phosphate material, which differs from Example 1 only in that it is not coated with PU but coated with PVA. The method specifically includes the following steps:

[0094] 1. LiMn 0.6 Fe 0.4 PO4 particles were added to anhydrous ethanol solution and ultrasonically cleaned for 2 hours to remove uncoated free carbon.

[0095] 2. Dissolve 0.5 mg of polyvinyl alcohol in 25 mL of N-dimethylformamide and stir to obtain a homogeneous PVA solution. Then, disperse 1000 mg of LMFP powder from step 1 into the PVA solution to obtain LMFP-PVA with a PVA nanolayer. Stir the mixture at 20 °C for 2 hours. Finally, collect the LMFP-PVA powder by evaporation and vacuum dry it at 100 °C for 10 hours to obtain the PVA-coated LMFP material, labeled as LMFP-PVA.

[0096] The above materials were subjected to manganese leaching tests and 45-degree coin cell cycle tests.

[0097] Manganese leaching tests were performed on the materials obtained in the examples and comparative examples. The powders obtained in Examples 1, 2, and 3 and Comparative Example 1 were soaked in a 0.008 mol / L dilute hydrochloric acid solution for 4 hours, filtered through 1 μm pore size filter paper, and the filtered solution was incubated in a 25°C water bath for 2 hours. The Mn leaching amount was then tested on an ICP-based assay. The test results are shown below. Figure 1 See Table 1.

[0098] The materials obtained from the examples and comparative examples were assembled into batteries, and the initial discharge capacity and cycle performance were tested. The test results are shown in [Figure Number]. Figure 2 See Table 1.

[0099] Battery assembly: Positive electrode case - Positive electrode sheet - Electrolyte - Separator - Electrolyte - Lithium sheet - Gasket - Negative electrode case.

[0100] The positive electrode coating surface density is 8 mg / cm2, and the electrolyte solvent is ethylene carbonate: methyl ethyl carbonate = 1:1.

[0101] Cyclic performance test: At 45℃, charge to 4.35V with a constant current of 0.5C, charge to 0.05C with a constant voltage of 4.35V, let stand for 10 minutes, discharge to 2.0V with a current of 0.5C, and let stand for 10 minutes.

[0102] Perform cyclic testing according to the above steps.

[0103] Table 1

[0104]

[0105]

[0106] According to Table 1, the examples and comparative examples show that PU-coated LMFP improves the dissolution of Mn from LMFP materials in dilute acid solutions.

[0107] According to Table 1, the comparison between the examples and comparative examples shows that PU-coated LMFP of a certain thickness can reduce manganese leaching from lithium manganese iron phosphate at 45 degrees Celsius and improve cycle performance. However, excessive thickness can affect the material's specific capacity. Comparative Example 2 shows another polymer-coated LMFP material, whose performance is significantly worse than that of PU-coated LMFP.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing lithium manganese iron phosphate material, characterized in that, include: Polyurethane, solvent and lithium manganese iron phosphate powder are mixed to obtain a mixture, and then the solvent in the mixture is removed to obtain the lithium manganese iron phosphate material; The mass fraction of polyurethane in the mixture is 2%-8%; The solvent is N-dimethylformamide; The solvent removal process in the mixture includes: first, pre-drying the mixture, and then vacuum drying it at 100°C-120°C for 10-12 hours to obtain the lithium manganese iron phosphate material. Before mixing the lithium manganese iron phosphate powder with polyurethane and solvent, the free carbon on the surface is removed. The method also includes the synthesis of polyurethane: Prepolymerization is carried out by reacting polypropylene glycol and 2,4-toluene diisocyanate under an inert atmosphere to obtain a polyurethane prepolymer; Polymerization: The polyurethane prepolymer is mixed with diethylene glycol to obtain a mixture, and the mixture is reacted under vacuum conditions to obtain polyurethane; The lithium manganese iron phosphate material includes lithium manganese iron phosphate and a polyurethane protective layer disposed on the surface of the lithium manganese iron phosphate; the polyurethane protective layer is a nano-polyurethane protective layer, and the mass fraction of the polyurethane protective layer in the lithium manganese iron phosphate material is 0.008wt%-0.2%.

2. The method for preparing lithium manganese iron phosphate material according to claim 1, characterized in that, The mass ratio of polypropylene glycol to 2,4-toluene diisocyanate is 1:(2-2.5). And / or, the molecular weight of the polypropylene glycol is 1500-2500; And / or, the temperature of the prepolymerization reaction is 80℃-100℃, and the time is 2h-4h.

3. The method for preparing lithium manganese iron phosphate material according to claim 1, characterized in that, The mass ratio of diethylene glycol to polypropylene glycol is 1:(0.9-1.1). And / or, the polymerization reaction is carried out at a temperature of 100℃-120℃ for a time of 10h-12h.

4. A lithium manganese iron phosphate material, characterized in that, It is obtained by the preparation method of lithium manganese iron phosphate material according to any one of claims 1-3.

5. The lithium manganese iron phosphate material according to claim 4, characterized in that, The average particle size of the lithium manganese iron phosphate is 0.8 μm-1.2 μm.

6. A positive electrode plate, characterized in that, Including the lithium manganese iron phosphate material as described in claim 4 or 5.

7. A lithium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 6.

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