A lithium iron manganese phosphate precursor, lithium iron manganese phosphate and preparation method and application thereof

Abstract

The present application relates to a kind of lithium manganese iron phosphate precursor and lithium manganese iron phosphate and its preparation method and application, the lithium manganese iron phosphate precursor includes manganese iron hydrotalcite and metal hydroxide, its expression is:[MnFe-Ldhs] a / [M(OH)2] b Wherein, M is Mn and / or Fe, 0

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a lithium manganese iron phosphate precursor, lithium manganese iron phosphate, its preparation method, and its application. Background Technology

[0002] Lithium iron phosphate (LiFePO4, LFP) has an olivine structure. Due to the high bond energy of the PO bonds in its structure, it avoids the breakage of PO bonds during use, thus preventing the release of oxygen. Even under extreme conditions such as short circuits and overheating, the material itself will not decompose and pose an explosion hazard. During charge and discharge, lithium iron phosphate exhibits characteristics such as small volume change and structural stability, providing excellent cycle performance and lifespan for LFP cathode materials. Therefore, it has become a widely used cathode material for lithium-ion batteries, playing a crucial role in electric vehicles, portable mobile device power supplies, and energy storage power supplies.

[0003] Lithium manganese iron phosphate (LiMn) x Fe 1-x LiFePO4 is a novel phosphate-based lithium-ion battery cathode material formed by doping lithium iron phosphate (LiFePO4) with a certain proportion of manganese (Mn). By doping with manganese, the advantageous characteristics of both iron and manganese can be effectively combined. Furthermore, manganese and iron are both located in the fourth period of the periodic table and are adjacent to each other, possessing similar ionic radii and some chemical properties. Therefore, doping does not significantly affect the original structure, and lithium manganese iron phosphate maintains the stable olivine-type structure of lithium iron phosphate.

[0004] Compared to lithium iron phosphate (LFP), the high voltage characteristic of manganese gives lithium manganese iron phosphate (LMP) a higher voltage platform, resulting in a higher energy density at the same specific capacity—10-20% higher under the same conditions. However, the introduction of manganese significantly reduces the material's conductivity. To address this, nano-sizing is typically used to reduce the lithium-ion diffusion path and improve material performance. The current mainstream method involves grinding raw materials (iron phosphate, manganese tetroxide, lithium carbonate, lithium dihydrogen phosphate, and glucose) using a sand mill to achieve nano-sizing, followed by high-temperature solid-state calcination to produce carbon-coated LMP. However, grinding iron phosphate, manganese tetroxide, and lithium carbonate is difficult to achieve high nano-sizing levels, or high nano-sizing requires long grinding times and is prone to sticking to the spray drying tower. This leads to difficulties in the industrial production of LMP, resulting in low equipment utilization, high material costs, and hindering the material's promotion and application. Summary of the Invention

[0005] Based on this, and addressing the problems existing in current technologies, the purpose of this invention is to provide a lithium manganese iron phosphate precursor, lithium manganese iron phosphate, its preparation method, and its applications. The lithium manganese iron phosphate precursor contains two components: manganese iron hydrotalcite and metal hydroxide. The manganese iron hydrotalcite has a layered structure, and its layered structure can slide relative to each other, thus possessing the characteristic of being easily broken and ground. The metal hydroxide can undergo a neutralization reaction with the weakly acidic LiH2PO4, preventing the adhesion phenomenon of subsequent spraying. While reducing the acidity of LiH2PO4, its own structure is also destroyed. Both the manganese iron hydrotalcite and the metal hydroxide can be rapidly nanoscaled under the action of a sand mill, and the particle size can be easily controlled within a small range, thereby further obtaining a high-performance lithium manganese iron phosphate electrode material.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a lithium manganese iron phosphate precursor, comprising manganese iron hydrotalcite and a metal hydroxide, with the formula: [MnFe-Ldhs]. a / [M(OH)2] b Where M is Mn and / or Fe, 0 <a<1,0<b≤1.8。

[0008] The lithium manganese iron phosphate precursor of the present invention contains two components: manganese iron hydrotalcite and metal hydroxide. The manganese iron hydrotalcite has a layered structure, and its layered structure can slide relative to each other, thus possessing the characteristic of being easily broken and ground. The metal hydroxide can undergo a neutralization reaction with the weakly acidic LiH2PO4, preventing the adhesion phenomenon of subsequent spraying. While reducing the acidity of LiH2PO4, its own structure is also destroyed. Both the manganese iron hydrotalcite and the metal hydroxide can be rapidly saturated to a high degree of nano-sizedness under the action of a sand mill, and the particle size can be easily controlled within a small range, thereby further obtaining a high-performance lithium manganese iron phosphate electrode material.

[0009] As a further improvement to the above-mentioned solution of the present invention, the iron element in the manganese-iron hydrotalcite is trivalent, and the iron and manganese elements in the metal hydroxide are both divalent.

[0010] This invention also provides a method for preparing a lithium manganese iron phosphate precursor, comprising the following steps:

[0011] S1. Add soluble salts containing iron and soluble salts containing manganese to a solvent and dissolve to obtain solution A;

[0012] S2. Add an oxidizing agent to solution A to adjust the Fe... 2+ Fe 3+ The proportions were used to obtain solution B;

[0013] S3. Add a solution containing carbonate to solution B, then add an alkaline solution to adjust the pH to 7.5-10.5 to obtain suspension C;

[0014] S4. The suspension C is subjected to a hydrothermal reaction, and then filtered to separate the precursor of lithium manganese iron phosphate.

[0015] As a further improvement to the above-mentioned solution of the present invention, in step S1, the total ion concentration of iron and manganese in solution A is 2-6 mol / L;

[0016] And / or, in step S1, the soluble salt containing iron is ferrous sulfate, ferric sulfate, or ferrous chloride;

[0017] And / or, in step S1, the soluble salt containing manganese is manganese sulfate or manganese chloride;

[0018] And / or, in step S1, the solvent is pure water, a mixture of pure water and ethanol, or a mixture of pure water and ethylene glycol.

[0019] As a further improvement to the above-described solution of the present invention, in step S2, in solution B, Fe 2+ Fe 3+ The ratio is 1-2:1-3;

[0020] And / or, in step S2, the oxidizing substance is at least one of peroxide, oxygen, metal halide, persulfate, perborate, hypohalate, halide, quinone compound, and perbenzoic acid compound, preferably H2O2, air, or oxygen. The oxidizing substance is used to oxidize Fe in the solution. 2+ It plays a role in regulating Fe 2 + Fe 3+ The role of proportion, usually Fe 3+ The content of MnFe-Ldhs in the composite precursor is determined by the content of the oxidizing substance, which is H2O2, compressed air or compressed oxygen. The oxidation of these three substances produces no byproducts and does not introduce impurities.

[0021] As a further improvement to the above-described solution of the present invention, in step S3, the solution containing carbonate ions is urea or sodium carbonate.

[0022] And / or, in step S3, the amount of carbonate added, by molar amount, is Fe 3+ 1.1-1.5 times;

[0023] And / or, in step S3, the alkaline solution is ammonia or sodium hydroxide.

[0024] As a further improvement to the above-mentioned scheme of the present invention, in step S4, the temperature of the hydrothermal reaction is 120-220℃ and the reaction time is 6-12h.

[0025] The present invention also provides a method for preparing lithium manganese iron phosphate, comprising the following steps: grinding and mixing the lithium manganese iron phosphate precursor and the lithium source as described above to obtain a mixed slurry D; then adding a carbon source to the mixed slurry D and mixing to obtain a mixed slurry E; spray drying the mixed slurry E to obtain powder; and calcining the powder under a protective atmosphere to obtain carbon-coated lithium manganese iron phosphate.

[0026] As a further improvement to the above-described solution of the present invention, the lithium manganese iron phosphate has the following general formula: LiMn x Fe 1- X PO4@C, where 0.1≤x≤0.9;

[0027] And / or, by molar amount, in the mixed slurry D, Li:(Mn+Fe):PO4=1.01-1.03:0.95-1.0:1.0;

[0028] And / or, the grinding and mixing time is 1-4 hours, and the particle size of the mixed slurry D is D50: 200-300 nm;

[0029] And / or, the lithium source is LiH2PO4;

[0030] And / or, the carbon source is glucose, sucrose or starch;

[0031] And / or, by mass, the amount of carbon source added is LiMn x Fe 1-X 8-20% of the theoretical mass of PO4;

[0032] And / or, the calcination temperature is 600-800℃, the time is 3-10 hours, and the heating rate is 3-5℃ / min.

[0033] The present invention also proposes a lithium manganese iron phosphate, which is prepared by the lithium manganese iron phosphate preparation method described above.

[0034] This invention also proposes an application of lithium manganese iron phosphate as a positive electrode active material as described above.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The lithium manganese iron phosphate precursor of the present invention contains two components: manganese iron hydrotalcite and metal hydroxide. The manganese iron hydrotalcite has a layered structure and its layered structure can slide relative to each other, thus possessing the characteristic of being easily broken and ground. The metal hydroxide can undergo a neutralization reaction with the weakly acidic LiH2PO4, preventing the adhesion phenomenon of subsequent spraying. While reducing the acidity of LiH2PO4, its own structure is also destroyed. Both the manganese iron hydrotalcite and the metal hydroxide can be rapidly nanoscaled under the action of a sand mill, and the particle size can be easily controlled within a small range, thereby further obtaining a high-performance lithium manganese iron phosphate electrode material.

[0037] 2. In the lithium manganese iron phosphate precursor of the present invention, the chemical formula of the manganese iron hydrocyclohexane is MnFe(OH)3CO3, wherein the iron ion is trivalent, and the chemical formula of the metal hydroxide is M(OH)2, wherein M is divalent and M is Mn and / or Fe.

[0038] 3. The preparation method of lithium manganese iron phosphate of the present invention, compared with the existing lithium iron phosphate production process, makes the processing of lithium iron phosphate cathode material simple and easy because the lithium manganese iron phosphate precursor contains two components: manganese iron hydrotalcite and metal hydroxide. The phenomenon of particles being difficult to grind will not occur. At the same time, after the metal hydroxide neutralizes the weak acidity of LiH2PO4, it will not adhere to the tower wall during spray drying. Furthermore, due to its small basic particles, it has excellent rate performance and excellent cycle performance. Its charge and discharge voltage platform is stable and has a high specific capacity. Attached Figure Description

[0039] Figure 1 The image shows the SEM image of the carbon-coated lithium manganese iron phosphate material prepared in Example 1 of this invention.

[0040] Figure 2 The XRD patterns of the carbon-coated lithium manganese iron phosphate material prepared in Example 1 of this invention and lithium iron phosphate are shown in comparison.

[0041] Figure 3 The XRD patterns of the carbon-coated lithium manganese iron phosphate material prepared in Example 1 of this invention are compared with those of lithium manganese phosphate. Detailed Implementation

[0042] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0044] Example 1

[0045] This embodiment provides a lithium manganese iron phosphate preparation method including the following steps:

[0046] S1. Solution preparation: Dissolve ferrous sulfate heptahydrate and manganese sulfate in pure water to obtain solution A; in solution A, the molar ratio of iron to manganese is 5:5, and the total concentration of iron and manganese metal ions is 4 mol / L.

[0047] S2. Valence Adjustment: Adding H2O2 to solution A changes the valence state of Fe in the solution. 2+ Fe 3+ The molar ratio of the substances is 2:3, resulting in solution B;

[0048] S3. Addition of precipitant: Add urea to solution B, wherein the amount of urea added is such that the amount of carbonate ions is Fe. 3+ The amount of substance should be 1.2 times the standard amount; then add ammonia water to adjust the pH of the solution to 9, stir well to obtain suspension C;

[0049] S4. Hydrothermal Reaction: The suspension C was transferred into a hydrothermal reactor and subjected to a hydrothermal reaction at 180°C for 8 hours. After filtration, separation, and drying, the lithium manganese iron phosphate precursor powder [MnFe-Ldhs] was obtained. 0.3 / [MnFe(OH)2] 0.2 ;

[0050] S5. Material Preparation: Lithium manganese iron phosphate precursor powder was ground and mixed with a specified amount of LiH2PO4 for 3 hours until D50: 200 nm, yielding a mixed slurry D. The molar ratio of Li:(Mn+Fe):PO4 in mixed slurry D was 1.02:0.975:1.0. Glucose was then added, with the amount of glucose added being equal to the mass of LiMn... 0.5 Fe 0.5 10.5% of the theoretical mass of PO4 was mixed to obtain a mixed slurry E; the mixed slurry E was spray-dried, and the resulting powder was calcined and pulverized under a protective atmosphere at a temperature of 700℃ for 5 hours at a heating rate of 5℃ / min to obtain carbon-coated lithium manganese iron phosphate material LiMn. 0.5 Fe 0.5 PO4@C.

[0051] Combination Figure 1 , Figure 1 The image shows the SEM image of the carbon-coated lithium manganese iron phosphate material prepared in this embodiment. Figure 1 The results show that the final lithium manganese iron phosphate particles are uniform nanoparticles. It is evident that due to the easy grinding characteristics of the precursor, the D50 of the slurry can be ground to 200 nm during the grinding process, which is a very high degree of nano-sizing. The highly nano-sized product is only possible thanks to the nano-sizing of the precursor. Figure 2 , Figure 3 , Figure 2 The XRD patterns of the carbon-coated lithium manganese iron phosphate material prepared in this embodiment are compared with those of lithium iron phosphate. Figure 3 The XRD patterns of the carbon-coated lithium manganese iron phosphate material prepared in this embodiment and lithium manganese phosphate show that the carbon-coated lithium manganese iron phosphate material in this embodiment has a spectrum between that of lithium iron phosphate and lithium manganese phosphate. Therefore, it can be determined that the sample is lithium manganese iron phosphate, rather than a single phase.

[0052] Example 2

[0053] This embodiment provides a lithium manganese iron phosphate preparation method including the following steps:

[0054] S1. Solution preparation: Dissolve ferrous sulfate heptahydrate and manganese chloride in pure water to obtain solution A; in solution A, the molar ratio of iron to manganese is 4:6, and the total concentration of iron and manganese metal ions is 4 mol / L.

[0055] S2. Valence Adjustment: Compressed oxygen is introduced into solution A, causing the Fe in the solution to... 2+ Fe 3+ The molar ratio of the substances is 1:1, resulting in solution B;

[0056] S3. Addition of precipitant: Add sodium carbonate to solution B, wherein the amount of sodium carbonate added is such that the amount of carbonate ions is Fe. 3+ The amount of substance should be 1.2 times the standard amount; then add sodium hydroxide to adjust the pH of the solution to 8, stir well to obtain suspension C;

[0057] S4. Hydrothermal Reaction: The suspension C was transferred into a hydrothermal reactor and subjected to a hydrothermal reaction at 120°C for 12 hours. After filtration and drying, the lithium manganese iron phosphate precursor powder [MnFe-Ldhs] was obtained. 0.2 / [MnFe(OH)2] 0.2 [Mn(OH)2] 0.2 ;

[0058] S5. Material Preparation: Lithium manganese iron phosphate precursor powder was ground and mixed with a specified amount of LiH2PO4 for 4 hours until D50: 250 nm, yielding a mixed slurry D. The molar ratio of Li:(Mn+Fe):PO4 in mixed slurry D was 1.03:0.98:1.0. Glucose was then added, with the amount of glucose added being equal to the mass of LiMn... 0.6 Fe 0.4 11% of the theoretical mass of PO4 was mixed to obtain a mixed slurry E; the mixed slurry E was spray-dried, and the resulting powder was calcined and pulverized under a protective atmosphere at a temperature of 750℃ for 8 hours at a heating rate of 4℃ / min to obtain carbon-coated lithium manganese iron phosphate material LiMn. 0.6 Fe 0.4 PO4@C.

[0059] Example 3

[0060] This embodiment provides a lithium manganese iron phosphate preparation method including the following steps:

[0061] S1. Solution preparation: Dissolve ferrous chloride and manganese chloride in pure water to obtain solution A; in solution A, the molar ratio of iron to manganese is 3:7, and the total concentration of iron and manganese metal ions is 4 mol / L.

[0062] S2. Valence Adjustment: Compressed oxygen is introduced into solution A, causing the Fe in the solution to... 2+ Fe 3+ The molar ratio of the substances is 1:2, resulting in solution B;

[0063] S3. Addition of precipitant: Add sodium carbonate to solution B, wherein the amount of sodium carbonate added is such that the amount of carbonate ions is Fe. 3+ The amount of substance should be 1.3 times the amount of substance; then add sodium hydroxide to adjust the pH of the solution to 10, stir well to obtain suspension C;

[0064] S4. Hydrothermal Reaction: The suspension C was transferred into a hydrothermal reactor and subjected to a hydrothermal reaction at 200°C for 6 hours. After filtration and drying, the lithium manganese iron phosphate precursor powder [MnFe-Ldhs] was obtained. 0.2 / [MnFe(OH)2] 0.1 [Mn(OH)2] 0.4 ;

[0065] S5. Material Preparation: Lithium manganese iron phosphate precursor powder was ground and mixed with a specified amount of LiH2PO4 for 1 hour, and then ground until D50: 300 nm was obtained to obtain a mixed slurry D. The ratio of Li:(Mn+Fe):PO4 in mixed slurry D was 1.01:1:1.0 by molar amount. Glucose was then added, with the amount of glucose added being equal to the mass of LiMn... 0.7 Fe 0.3 13% of the theoretical mass of PO4 was mixed to obtain a mixed slurry E; the mixed slurry E was spray-dried, and the resulting powder was calcined and pulverized under a protective atmosphere at a temperature of 800℃ for 10 hours at a heating rate of 5℃ / min to obtain carbon-coated lithium manganese iron phosphate material LiMn. 0.7 Fe 0.3 PO4@C.

[0066] Comparative Example

[0067] This comparative example provides a lithium manganese iron phosphate preparation method including the following steps:

[0068] Manganese tetroxide, iron phosphate, and a specific ratio of LiH2PO4 and lithium carbonate were ground and mixed for 1 hour to obtain a mixed slurry D, wherein, by molar amount, the ratio of Li:(Mn+Fe):PO4 in mixed slurry D was 1.01:1:1.0, and the ratio of Mn:Fe was 5:5. Glucose was then added, and by mass, the amount of glucose added was 13% of the theoretical mass of LiMnFePO4. The mixture was then mixed to obtain mixed slurry E. Mixed slurry E was spray-dried, and the resulting powder was calcined and pulverized under a protective atmosphere at a temperature of 800℃ for 10 hours at a heating rate of 5℃ / min to obtain carbon-coated lithium manganese iron phosphate material.

[0069] Test case

[0070] The carbon-coated lithium manganese iron phosphate materials prepared in Examples 1-3 and the comparative examples were used to prepare coin cells, including the following steps: (1) The carbon-coated lithium manganese iron phosphate material and conductive carbon black were ground and mixed evenly to obtain a mixed powder. The binder PVDF was dissolved in NMP to form a colloid. The mixed powder was then added to the colloid and stirred evenly to form a slurry with good flowability. The mass ratio of carbon-coated lithium manganese iron phosphate material: conductive carbon black: PVDF = 8:1:1; (2) The slurry was coated on aluminum foil to form a positive electrode sheet; (3) The positive electrode sheet was dried to remove the solvent in the slurry and then punched to obtain a circular sheet required for coin cell testing; (4) The positive electrode sheet, separator, and lithium metal negative electrode were assembled into a coin cell.

[0071] The prepared coin cells were subjected to a coin cell test: The coin cells were charged and discharged once at a 0.2C rate to obtain the initial charge / discharge capacity and the initial discharge capacity. The initial discharge capacity divided by the initial charge / discharge capacity gave the initial efficiency. The coin cells prepared in Examples 1-3 and the comparative examples were then charged and discharged once at a 1C rate to obtain the 1C capacity. The test results are shown in Table 1.

[0072] Table 1

[0073]

[0074] As shown in Table 1, compared with the comparative example, the coin cells made from carbon-coated lithium manganese iron phosphate materials prepared in Examples 1-3 have higher capacity and first-time efficiency. This is because the lithium manganese iron phosphate precursors prepared in Examples 1-3 have better grindability and are easier to nanoscale, and the products can be better nanoscaled and form phases. The high degree of nanoscale formation can reduce the diffusion path of lithium ions and solve the problem of low capacity caused by the low conductivity of lithium iron manganese.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing lithium manganese iron phosphate, characterized in that, The process includes the following steps: grinding and mixing the lithium manganese iron phosphate precursor and the lithium source to obtain a mixed slurry D; then adding a carbon source to the mixed slurry D and mixing to obtain a mixed slurry E; spray drying the mixed slurry E to obtain powder; and calcining the powder under a protective atmosphere to obtain carbon-coated lithium manganese iron phosphate. The lithium iron manganese phosphate precursor contains manganese iron hydrotalcite and metal hydroxide, and its expression is: [MnFe-Ldhs] a / [M(OH)2] b , where M is Mn and / or Fe, 0 < a < 1, 0 < b ≤ 1.8; the lithium source is LiH2PO4.

2. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that, The iron in the manganese-iron hydrotalcite is trivalent, while both iron and manganese in the metal hydroxide are divalent.

3. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that, The preparation method of the lithium manganese iron phosphate precursor includes the following steps: S1. Add soluble salts containing iron and soluble salts containing manganese to a solvent and dissolve to obtain solution A; S2. Add an oxidizing agent to solution A to adjust the Fe... 2+ Fe 3+ The proportions were used to obtain solution B; S3. Add a solution containing carbonate to solution B, then add an alkaline solution to adjust the pH to 7.5-10.5 to obtain suspension C; S4. The suspension C is subjected to a hydrothermal reaction, and then filtered to separate the precursor of lithium manganese iron phosphate.

4. The method for preparing lithium manganese iron phosphate according to claim 3, characterized in that, In step S1, the total concentration of iron and manganese ions in solution A is 2-6 mol / L; And / or, in step S1, the soluble salt containing iron is ferrous sulfate, ferric sulfate, or ferrous chloride; And / or, in step S1, the soluble salt containing manganese is manganese sulfate or manganese chloride; And / or, in step S1, the solvent is pure water, a mixture of pure water and ethanol, or a mixture of pure water and ethylene glycol.

5. The method for preparing lithium manganese iron phosphate according to claim 3, characterized in that, In step S2, in solution B, Fe 2+ Fe 3+ The ratio is 1-2:1-3; And / or, in step S2, the oxidizing substance is at least one of peroxide, oxygen, metal halide, persulfate, perborate, hypohalate, halide, quinone compound, and perbenzoic acid compound.

6. The method for preparing lithium manganese iron phosphate according to claim 3, characterized in that, In step S3, the solution containing carbonate ions is urea or sodium carbonate; And / or, in step S3, the amount of carbonate added, by molar amount, is Fe 3+ 1.1-1.5 times; And / or, in step S3, the alkaline solution is ammonia or sodium hydroxide; And / or, in step S4, the temperature of the hydrothermal reaction is 120-220°C, and the reaction time is 6-12 hours.

7. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that, The lithium manganese iron phosphate has the following general formula: LiMn x Fe 1-X PO4@C, where 0.1≤x≤0.9; And / or, by molar amount, in the mixed slurry D, Li:(Mn+Fe):PO4=1.01-1.03:0.95-1.0:1.0; And / or, the grinding and mixing time is 1-4 hours, and the particle size of the mixed slurry D is D50: 200-300 nm; And / or, the carbon source is glucose, sucrose or starch; And / or, by mass, the amount of carbon source added is LiMn x Fe 1-X PO4 accounts for 8-20% of the theoretical mass; And / or, the calcination temperature is 600-800℃, the time is 3-10 hours, and the heating rate is 3-5℃ / min.

8. A lithium manganese iron phosphate, characterized in that, It is prepared using the method for preparing lithium manganese iron phosphate as described in any one of claims 1-7.

9. An application of lithium manganese iron phosphate as described in claim 8 as a positive electrode active material.

Images