Lithium manganese iron phosphate positive electrode material and preparation method thereof
Through the binary conjugated acid and alkali of oxalate oxalate binary conjugated acid and alkali, the pH self-regulation of lithium manganese phosphate material and uniform deposition of ferromanganese at room temperature, the problems of complex preparation process, long cycle, high energy consumption and uneven distribution of ferromanganese in the existing technology are solved, and the rapid continuous production of materials and the improvement of electrochemical performance are achieved.
Patent Information
- Application Number
- CN202510312848.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-17
- Publication Date
- 2025-06-13
AI Technical Summary
The existing preparation methods for lithium manganese ferrophosphate materials have problems such as complex preparation process, long cycle, high energy consumption and uneven distribution of ferromanganese, resulting in poor electrochemical performance.
The pH of the reaction system is self-regulated by the binary conjugated acid and base of oxalate oxalate, and the uniform deposition of ferrous manganese manganese is achieved through the similar solubility product constants of ferrous oxalate and manganese oxalate at room temperature, simplifying the process flow and reducing equipment requirements.
The rapid and continuous production of lithium manganese iron phosphate materials is achieved, which improves the circulation and rate performance of the materials, reduces energy consumption, and simplifies the process flow.
Smart Images
Figure CN120149397A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a lithium iron manganese phosphate cathode material and a preparation method thereof. Background Art
[0002] At present, new energy vehicles in China mainly use ternary lithium batteries and lithium iron phosphate batteries as power sources. The market share of ternary lithium batteries has gradually decreased due to safety hazards; lithium iron phosphate batteries have attracted much attention due to their stable structure, long life, low cost, and high safety. However, the voltage platform of lithium iron phosphate batteries is only 3.4V, and the low energy density restricts their further development. The lithium iron manganese phosphate material with the same crystal structure as it has all the advantages of the lithium iron phosphate material. In addition, since the voltage platform of manganese in this material reaches about 4.1V, its theoretical energy density is about 15% higher than that of lithium iron phosphate. However, its own ionic and electronic conductivities are relatively low, and the Jahn-Teller effect of manganese during the cycling process results in a relatively low actual capacity and poor cycling performance of the material. The uniform distribution of manganese and iron in the material is crucial for the formation of the solid solution of the lithium iron manganese phosphate material and the suppression of the Jahn-Teller effect.
[0003] The distribution of manganese and iron in the lithium iron manganese phosphate material is related to the preparation process. At present, the main methods for synthesizing lithium iron manganese phosphate are the solid-phase method and the liquid-phase method. Due to the limitation of the mixing process, the solid-phase method cannot achieve atomic-level uniform distribution of manganese and iron. Although the lithium iron manganese phosphate prepared by the liquid-phase method can achieve a high degree of uniformity of Mn and Fe at the atomic level, the hydrothermal / solvothermal method is not conducive to large-scale production due to process problems, while the co-precipitation method has attracted much attention because it is easy to achieve large-scale industrial production. At present, the mainstream preparation route of commercial lithium iron phosphate materials is to prepare lithium iron phosphate precursors by the precipitation method and then obtain lithium iron phosphate materials through a solid-phase process. The lithium iron phosphate materials obtained by this preparation route are well recognized by the market due to their high specific capacity, long cycle life, and good rate performance. However, the corresponding precursors of lithium iron manganese phosphate and iron manganese phosphate due to the poor stability of Mn 3+ in aqueous solution and Mn 3 (PO 4 ) 2 and Fe 3 (PO 4 ) 2 have a huge difference in solubility in aqueous solution and it is difficult to achieve co-deposition, which becomes a major difficulty in preparing lithium iron manganese phosphate materials by the co-precipitation method. In addition, most of the co-precipitation methods currently used in the industry need to heat the solution and adjust the pH. The reaction time often reaches more than 12h, and heat preservation operation is required after the reaction is completed. This will greatly increase the production cost, improve the equipment requirements, and hinder the efficiency of industrial production. The use of pH regulators also has the risks of difficult precise control and introducing new impurities.
[0004] Therefore, the development of a coprecipitation method for preparing lithium iron manganese phosphate materials with uniform manganese and iron distribution, fast preparation speed, simple operation, low equipment requirements, and low energy consumption is of great significance for realizing the industrial production of this material and improving its electrochemical performance. Summary of the Invention
[0005] The object of the present invention is to solve the problems existing in the current preparation methods of lithium iron manganese phosphate materials, such as complex preparation processes, long preparation cycles, high energy consumption, and poor electrochemical performance caused by uneven manganese and iron distribution, and to provide a lithium iron manganese phosphate cathode material and its preparation method.
[0006] To achieve the above object, the technical solutions adopted by the present invention are as follows:
[0007] A lithium iron manganese phosphate cathode material, the chemical general formula of the lithium iron manganese phosphate cathode material is LiMn x Fe (1-x) PO 4 , where 0.5 ≤ x ≤ 0.8.
[0008] A preparation method of the above lithium iron manganese phosphate cathode material, the method is as follows:
[0009] S1: At room temperature, dissolve the manganese source and the iron source in deionized water in the presence of an antioxidant or under the protection of an inert gas according to the molar ratio to form a first solution;
[0010] S2: At room temperature, dissolve oxalic acid and oxalate in deionized water according to a certain molar ratio as a pH buffer and a precipitant;
[0011] S3: At room temperature, stir the first solution, and when the rotation speed is stable, instantaneously mix the pH buffer (precipitant) with the first solution to form a second solution;
[0012] S4: At room temperature, continue to stir the second solution for 10 minutes, then perform solid-liquid separation, wash multiple times with water, and vacuum dry to obtain a lithium iron manganese phosphate precursor material;
[0013] S5: Weigh the lithium iron manganese phosphate precursor, lithium source, and phosphorus source according to the molar ratio range of 1:1:1 to 1:1.1:1.05, and weigh the carbon source according to the mass ratio of carbon in the carbon source of 1% - 8%, and perform mixing;
[0014] S6: After the mixing is completed, sinter the mixture at high temperature in an inert gas or a reducing atmosphere to obtain a lithium iron manganese phosphate cathode material.
[0015] Further, in S1, the manganese source is one or more of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; the manganese sulfate may or may not have crystal water; the iron source is one or more of ferrous sulfate, ferrous nitrate, ferrous acetate, and ferrous chloride; the ferrous sulfate may or may not have crystal water; the antioxidant is one or two of ascorbic acid or citric acid; the inert gas is one or more of argon, helium, or nitrogen.
[0016] Further, in S1, the molar ratio of the manganese source to the iron source is 1-4:1, and the total concentration of Fe 2+ , Mn 2+ in the first solution is 0.1-1 mol / L; the concentration of the antioxidant is 0.01-0.1 mol / L.
[0017] Further, in S2, the oxalate is one or more of ammonium oxalate, sodium oxalate, and potassium oxalate.
[0018] Further, in S2, the concentration of the oxalate is 0.01-0.5 mol / L, and the molar ratio of oxalic acid to the oxalate is 2:1-1:5, which can be determined according to the required pH of the solution.
[0019] Further, in S3, the stirring speed is 500-1500 r / min.
[0020] Further, in S3, the ratio of the total concentration of Fe 2+ , Mn 2+ to the total concentration of oxalic acid and the oxalate is 1:1-1.5.
[0021] Further, in S4, the temperature of the vacuum drying is 60-120 °C, and the time is 6-48 h.
[0022] Further, in S5, the lithium source is one or more of lithium carbonate, lithium phosphate, and lithium dihydrogen phosphate; the phosphorus source is one or more of ammonium dihydrogen phosphate, lithium dihydrogen phosphate, and lithium phosphate; the carbon source is one or more of glucose, sucrose, PEG, starch, citric acid, and phenolic resin.
[0023] Further, in S5, the mixing is carried out by dry grinding or ball milling in a solvent. The ball milling speed is 500-1000 r / min, and the ball milling duration is 5-15 h; the solvent is one or more of ethanol, ethylene glycol, and acetone. After the ball milling is completed, the materials mixed in the solvent are vacuum dried. The drying temperature is 60-120 °C, and the drying duration is 6-12 h.
[0024] Further, in S6, the inert gas is one of argon, nitrogen, and helium, and the reducing gas is a hydrogen-argon mixture; the calcination temperature is 600-750°C, the reaction time is 5-15 h, and the heating rate is 2-5°C / min.
[0025] Compared with the prior art, the present invention has the following beneficial effects: The preparation method of the lithium iron manganese phosphate cathode material provided by the present invention realizes the pH self-regulation of the reaction system within a certain range by using an oxalic acid-oxalate binary conjugate acid-base pair at room temperature, without detecting and regulating the solution pH, laying a foundation for rapid continuous production; by utilizing the very similar solubility product constants of ferrous oxalate and manganese oxalate at room temperature, uniform deposition of manganese and iron is achieved through rapid coprecipitation. This method greatly simplifies the process flow, reduces the equipment requirements, and improves the cycle and rate performance; moreover, the synthesis process can be carried out at room temperature without additional heating, greatly reducing energy consumption and being conducive to energy conservation and emission reduction; the reaction can be completed only by stirring for ten minutes without a heat preservation time, greatly shortening the production time of the lithium iron manganese phosphate precursor prepared by the coprecipitation method, which is of great significance for the industrial large-scale production of the lithium iron manganese phosphate cathode material. Brief Description of the Drawings
[0026] Figure 1 It is the cycle performance diagram of the lithium iron manganese phosphate material obtained in Example 1.
[0027] Figure 2 It is the SEM diagram of the lithium iron manganese phosphate precursor material obtained in Example 1.
[0028] Figure 3 It is the EDS diagram of the lithium iron manganese phosphate precursor material obtained in Example 2.
[0029] Figure 4 It is the rate diagram of the lithium iron manganese phosphate material obtained in Example 2.
[0030] Figure 5 It is the SEM diagram of the lithium iron manganese phosphate material obtained in Example 3.
[0031] Figure 6 It is the EDS diagram of the lithium iron manganese phosphate material obtained in Example 3.
[0032] Figure 7 It is the XRD diagram of the lithium iron manganese phosphate material obtained in Example 3.
[0033] Figure 8 It is the process flow diagram of the present invention. Detailed Embodiments
[0034] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.
[0035] The present invention benefits from the fact that oxalic acid and oxalates form two pairs of conjugate acid-base relationships in aqueous solution to achieve relative stability of the pH of the reaction system within an effective range, without the need to additionally add a pH regulator and monitoring equipment to control the solution pH, which lays a solid foundation for realizing rapid continuous production. By adjusting the ratio of oxalic acid and oxalates, diverse regulation of the pH of the reaction system can be achieved to meet impurity removal and the production of precursors with different physicochemical properties; in addition, due to the very similar solubility product constants of Mn 2+ and Fe 2+ in a buffer solution at room temperature, when Mn 2+ and Fe 2+ and C 2 O 4 2- reach the deposition conditions, Mn and Fe have similar nucleation and growth rates, thus achieving the purpose of uniform distribution of Mn and Fe in the precursor.
[0036] Example 1
[0037] A lithium manganese iron phosphate material prepared by a pH self-regulating rapid controllable coprecipitation method at room temperature, with the chemical formula LiMn 0.5 Fe 0.5 PO 4 , and the preparation process includes the following steps:
[0038] Step 1: Weigh 6.76 g of manganese sulfate monohydrate and 11.12 g of ferrous sulfate heptahydrate according to the stoichiometric ratio of 1:1, and then weigh 0.88 g of ascorbic acid. Dissolve manganese sulfate monohydrate, ferrous sulfate heptahydrate and ascorbic acid in 200 mL of deionized water by sufficient stirring to form a mixed transition metal salt solution.
[0039] Step 2: Weigh 12.18 g of ammonium oxalate and 2.57 g of oxalic acid according to the stoichiometric ratio of 3:1. Dissolve oxalic acid and ammonium oxalate in 210 mL of deionized water at room temperature by sufficient stirring as a pH buffer and precipitant.
[0040] Step 3: Rapidly add the solution prepared in Step 2 to the mixed transition metal salt solution under the condition of stirring the mixed transition metal salt solution, and continue to stir for 10 min to form a turbid liquid.
[0041] Step 4: Perform vacuum filtration under reduced pressure on the turbid liquid formed in Step 3, wash it several times with water, and then dry it in vacuum at 80 °C for 24 h to obtain a lithium manganese iron phosphate precursor material. Attached Figure 2This is a SEM image of the prepared lithium manganese iron phosphate material precursor. It can be seen from the image that the precursor's microscopic morphology is a block structure formed by the accumulation of flake structures, with a particle size of approximately 5-15 microns and a uniform particle size distribution.
[0042] Step 5: Weigh the lithium manganese iron phosphate precursor, lithium carbonate and ammonium dihydrogen phosphate according to the stoichiometric ratio of (Mn+Fe):P:Li=1:1.01:1.05, add 5% glucose as a carbon source and perform ball milling at a ball milling speed of 500 r / min for 9 h.
[0043] Step 6: The mixture obtained in step 5 is sintered in an argon atmosphere at a heating rate of 2°C / min. After pre-sintering at 350°C for 3 hours, it is reacted at 650°C for 10 hours. After natural cooling, the lithium manganese iron phosphate positive electrode material is obtained. The cycle performance diagram of the prepared lithium manganese iron phosphate material is shown in the attached figure. Figure 1 As shown, the discharge specific capacity at 0.1C rate reaches 156mAh / g, the discharge specific capacity at 1C rate reaches 141mAh / g, and the capacity retention rate is close to 100% after 390 cycles, indicating that the material has excellent electrochemical properties and super structural stability.
[0044] Example 2
[0045] A lithium manganese iron phosphate material prepared by a pH self-regulating rapid controllable co-precipitation method at room temperature, the chemical formula of which is LiMn 0.5 Fe 0.5 PO 4 The preparation process includes the following steps:
[0046] Step 1: 37.752 g of manganese chloride and 83.415 g of ferrous sulfate heptahydrate were weighed according to a stoichiometric ratio of 1:1, and the manganese chloride and ferrous sulfate heptahydrate were completely dissolved in 1000 mL of deionized water by sufficient stirring under a nitrogen atmosphere to form a mixed transition metal salt solution.
[0047] Step 2: Weigh 26.8 g of sodium oxalate and 36.012 g of oxalic acid according to the stoichiometric ratio of 1:2, and dissolve the oxalic acid and sodium oxalate in 800 mL of deionized water by sufficient stirring at room temperature as a pH buffer and precipitant.
[0048] Step 3: While stirring the mixed transition metal salt solution, quickly add the solution prepared in step 2 to the mixed metal salt solution, and continue stirring for 10 minutes to form a turbid solution.
[0049] Step 4: The turbid liquid formed in step 3 is filtered under reduced pressure, washed with water for multiple times, and then dried in vacuum at 100°C for 12 hours to obtain a lithium manganese iron phosphate precursor material. Figure 3As shown, EDS test shows that manganese and iron elements in the prepared lithium iron manganese phosphate precursor material are completely uniformly distributed, which is of great significance for the formation of solid solution and the inhibition of the Jahn-Teller effect of Mn 3+ and has very important significance for the suppression of the Jahn-Teller effect.
[0050] Step 5: Weigh lithium iron manganese phosphate precursor, lithium carbonate, and ammonium dihydrogen phosphate according to the stoichiometric ratio (Mn + Fe):P:Li = 1:1.02:1.08, then add 5% glucose as a carbon source and carry out ball milling. The ball milling speed is 800 r / min, and the ball milling time is 9 h.
[0051] Step 6: Sinter the mixed material obtained in Step 5 under an argon atmosphere. The heating rate is 5 °C / min. After pre-sintering at 400 °C for 3 h, react at 650 °C for 10 h, and obtain the lithium iron manganese phosphate cathode material after natural cooling. As shown in the appendix Figure 4 As shown, the prepared lithium iron manganese phosphate material has a discharge specific capacity of 114 mAh / g under the condition of 5C rate, a discharge specific capacity of 96 mAh / g under the condition of 10C rate, and still has a discharge specific capacity of 72 mAh / g at a super high rate of 20C. This result shows that the lithium iron manganese phosphate material prepared by this method has excellent rate performance.
[0052] Example 3
[0053] A lithium iron manganese phosphate material prepared by a pH self-adjusting rapid and controllable coprecipitation method at room temperature, with the chemical formula LiMn 0.6 Fe 0.4 PO 4 , and the preparation process includes the following steps:
[0054] Step 1: Weigh 202.8 g of manganese sulfate monohydrate and 121.528 g of ferrous sulfate according to the stoichiometric ratio of 1:1. The reaction is carried out in a nitrogen environment. Dissolve manganese sulfate monohydrate and ferrous sulfate in 4000 mL of deionized water through sufficient stirring to form a mixed transition metal salt solution.
[0055] Step 2: Weigh 227.376 g of ammonium oxalate and 72.024 g of oxalic acid according to the stoichiometric ratio of 2:1. Dissolve oxalic acid and ammonium oxalate in 4000 mL of deionized water through sufficient stirring at room temperature as a pH buffer and precipitant.
[0056] Step 3: Rapidly add the solution prepared in Step 2 to the mixed metal salt solution under the condition of stirring the mixed metal salt solution, and continue to stir for 10 min to form a turbid liquid.
[0057] Step 4: Carry out vacuum filtration under reduced pressure on the turbid liquid formed in Step 3, wash it several times with water, and then dry it in vacuum at 100 °C for 24 h to obtain the lithium iron manganese phosphate precursor material.
[0058] Step 5: Weigh lithium iron manganese phosphate precursor, lithium carbonate, and ammonium dihydrogen phosphate according to the stoichiometric ratio (Mn + Fe):P:Li = 1:1.03:1.05. Then add 5% glucose as a carbon source and conduct ball milling in an ethanol solvent with a mass ratio of 1:1 to the total material. The ball milling speed is 1000 r / min, and the ball milling time is 9 h.
[0059] Step 6: Vacuum dry the mixture obtained in Step 5 at 60 °C for 12 h and then grind it to obtain the sintering precursor material.
[0060] Step 7: Sinter the sintering precursor material obtained in Step 6 in an atmosphere of a hydrogen-argon mixed reducing gas. The heating rate is 2 °C / min. Pre-sinter at 400 °C for 3 h and then react at 650 °C for 10 h. After natural cooling, the lithium iron manganese phosphate cathode material is obtained. As shown in the Figure 5 SEM images, the microstructure of the lithium iron manganese phosphate material prepared by this method is formed by the agglomeration of sub-micron primary particles into secondary particles, and the particle size distribution is uniform; as shown in the Figure 6 EDS test results, in the lithium iron manganese phosphate material prepared by this method, manganese and iron are completely uniformly distributed, which is beneficial to the improvement of the electrochemical performance of this material. As shown in the Figure 7 XRD test results show that the lithium iron manganese phosphate material prepared by this method belongs to the typical orthorhombic olivine structure, indicating the successful synthesis of this material.
[0061] In summary, the method for preparing lithium iron manganese phosphate provided by the present invention benefits from the existence of the oxalic acid - oxalate binary acid-base conjugate pair to achieve self-regulation of the pH of the reaction system; there is no need for additional monitoring and adjustment of the system pH, and large-scale continuous production can be realized; the very similar solubility product constants of manganese oxalate and iron oxalate in the buffer solution at room temperature make it possible to rapidly prepare and simultaneously and uniformly precipitate manganese and iron, which can greatly improve the cycle and rate performance of the prepared lithium iron manganese phosphate material. The preparation method based on the above principle has the characteristics of fast preparation speed, simple operation, low equipment requirements, and low manufacturing cost. It can greatly shorten the reaction time and aging time for preparing the precursor, solve the problems of precise pH regulation and the need for additional heating during the reaction process in the current co-precipitation process for preparing the precursor, and can effectively improve the shortcoming of uneven manganese and iron distribution in the lithium iron manganese phosphate material. As shown in the Figure 3 and Figure 6 EDS test results, the lithium iron manganese phosphate material prepared by this method and its precursor achieve uniform distribution of manganese and iron elements in the material; the lithium iron manganese phosphate material prepared by it has a high energy density, excellent high-rate discharge ability, and high cycle stability. As shown in the Figure 1 and Figure 4As shown, the discharge specific capacity of the lithium iron manganese phosphate material prepared by this method reaches 156 mAh / g at a 0.1C rate; the discharge specific capacity reaches 141 mAh / g at a 1C rate, and the capacity retention rate is close to 100% after 390 cycles; it has a discharge specific capacity of 114 mAh / g under 5C rate conditions; it has a discharge specific capacity of 96 mAh / g under 10C rate conditions; it still has a discharge specific capacity of 72 mAh / g at a 20C ultra-high rate, making it a very competitive cathode material for the next generation of lithium-ion power batteries.
Claims
1. A lithium manganese iron phosphate positive electrode material, characterized in that: The chemical formula of the lithium manganese iron phosphate positive electrode material is LiMn x Fe (1-x) PO4, where 0.5≤x≤0.
8.
2. A method for preparing the lithium iron manganese phosphate positive electrode material as claimed in claim 1, characterized in that: The method is: S1: at room temperature, completely dissolving a manganese source and an iron source in a molar ratio in deionized water in the presence of an antioxidant or under the protection of an inert gas to form a first solution; S2: At room temperature, oxalic acid and oxalate are completely dissolved in deionized water at a certain molar ratio as a pH buffer and precipitant; S3: stirring the first solution at room temperature, and after the rotation speed is stabilized, instantaneously mixing the pH buffer solution (precipitant) with the first solution to form a second solution; S4: at room temperature, stirring the second solution for 10 minutes, then performing solid-liquid separation, washing with water for multiple times, and vacuum drying the solution to obtain a lithium manganese iron phosphate precursor material; S5: weighing a lithium iron manganese phosphate precursor, a lithium source, and a phosphorus source according to a molar ratio ranging from 1:1:1 to 1:1.1:1.05, and weighing a carbon source with a mass ratio of carbon in the carbon source of 1%-8%, and mixing; S6: After the mixing is completed, the mixture is sintered at a high temperature in an inert gas or a reducing atmosphere to obtain a lithium manganese iron phosphate positive electrode material.
3. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 2, characterized in that: In S1, the manganese source is one or more of manganous sulfate, manganous nitrate, manganous acetate, and manganous chloride; the iron source is one or more of ferrous sulfate, ferrous nitrate, ferrous acetate, and ferrous chloride; the antioxidant is one or both of ascorbic acid or citric acid; the inert gas is one or more of argon, helium, or nitrogen; in S2, the oxalate is one or more of ammonium oxalate, sodium oxalate, and potassium oxalate; in S5, the lithium source is one or more of lithium carbonate, lithium phosphate, and lithium dihydrogen phosphate; the phosphorus source is one or more of ammonium dihydrogen phosphate, lithium dihydrogen phosphate, and lithium phosphate; the carbon source is one or more of glucose, sucrose, PEG, starch, citric acid, and phenolic resin.
4. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 2, characterized in that: In S1, the molar ratio of the manganese source to the iron source is 1-4:1, and the Fe 2+ , Mn 2+ The total concentration is 0.1-1 mol / L; the concentration of the antioxidant is 0.01-0.1 mol / L.
5. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 2, characterized in that: In S2, the oxalate concentration is 0.01-0.5 mol / L, and the molar ratio of oxalic acid to oxalate is 2:1-1:
5.
6. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 2, characterized in that: In S3, the stirring speed is 500-1500 r / min.
7. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 2, characterized in that: In S3, Fe 2+ , Mn 2+ The ratio of the total concentration to the total concentration of oxalic acid and oxalate is 1:1 to 1.
5.
8. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 2, characterized in that: In S4, the vacuum drying is carried out at a temperature of 60-120° C. and for a time of 6-48 hours.
9. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 2, characterized in that: In S5, the mixed material is dry-milled or ball-milled in a solvent, the ball-milling speed is 500-1000 r / min, and the ball-milling time is 5-15 h; the solvent is one or more of ethanol, ethylene glycol, and acetone.
10. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 2, characterized in that: In S6, the inert gas is one of argon, nitrogen and helium, and the reducing gas is a hydrogen-argon mixture; the calcination temperature is 600-750°C, the reaction time is 5-15h, and the heating rate is 2-5°C / min.