High-uniformity lithium manganese iron phosphate precursor and microwave-rheological phase coupling preparation method thereof
By using microwave-assisted coprecipitation and rheological phase coupling to prepare lithium manganese iron phosphate materials, the problems of manganese iron segregation and morphology loss of control were solved, and atomic-level uniform distribution of Mn2+/Fe2+ and improved structural stability were achieved.
Patent Information
- Application Number
- CN202511345201.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-19
- Publication Date
- 2025-12-23
AI Technical Summary
In the existing technology, lithium manganese iron phosphate materials have problems such as manganese iron segregation, uncontrolled morphology and uneven doping, including the problem of uneven manganese iron. The existing technology has not solved the problems of manganese iron segregation, uncontrolled morphology and uneven doping in lithium manganese iron phosphate materials.
A uniformly nucleated Mn2+/Fe2+ precursor was prepared by microwave-assisted co-precipitation and reacted with lithium dihydrogen phosphate and a doping system in a rheological medium to form a paste-like reactant. The reactant was then simultaneously coated with carbon by low-temperature crystallization to obtain a highly uniform lithium manganese iron phosphate precursor.
Atomic-level uniform distribution of Mn2+/Fe2+ was achieved, which improved the electronic and ionic conductivity of the material, solved the problems of manganese-iron segregation and morphology loss control, and improved the structural stability of the material.
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Figure CN121180968A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of electrode material preparation technology, specifically relating to highly uniform manganese iron phosphate materials and their microwave-rheological phase coupling preparation method. Background Technology
[0002] Lithium iron phosphate (LFP) combines the advantages of lithium iron phosphate (LFP) and lithium manganese phosphate (LMP). By partially replacing Fe and Mn, it achieves performance optimization. Due to its high energy density, high safety and low cost, it is considered an important development direction in the fields of power batteries and energy storage.
[0003] Lithium manganese iron phosphate precursor is a pretreatment material for the preparation of lithium manganese iron phosphate (LFMP) materials.
[0004] Existing technologies mainly face three major bottlenecks:
[0005] 1. Manganese and iron segregation: The large pH difference in Mn2+ / Fe2+ precipitation (ΔpH>1.5) leads to fluctuations in composition.
[0006] 2. Uncontrolled morphology: Traditional coprecipitates are prone to agglomeration, with a tap density <1.5 g / cm³. 3
[0007] 3. Uneven doping: Post-treatment doping only modifies the surface and cannot suppress the bulk Jahn-Teller effect.
[0008] In view of the above, this application is hereby submitted. Summary of the Invention
[0009] To address one of the aforementioned technical deficiencies, this application provides a highly uniform lithium manganese iron phosphate precursor and its microwave-rheological phase coupling preparation method.
[0010] The technical solution of this application provides a microwave-rheological phase coupling preparation method for a highly uniform lithium manganese iron phosphate precursor, comprising the following steps:
[0011] (1) Prepare uniformly nucleated Mn using microwave-assisted coprecipitation method 2+ / Fe 2+ Precursor;
[0012] (2) Mn 2+ / Fe 2+ The precursor, lithium dihydrogen phosphate, and doping system were added to a rheological medium in proportion to construct a non-Newtonian fluid reaction environment for phosphating and multi-component doping in the rheological phase medium, resulting in a paste-like precursor complex.
[0013] (3) The paste-like precursor complex is placed under the first preset conditions for low-temperature crystallization and simultaneous carbon coating to obtain carbon-coated lithium manganese iron phosphate precursor.
[0014] Preferably, step (1) specifically includes the following steps:
[0015] (1.1) Prepare Mn using MnSO4·H2O and FeSO4·7H2O 2+ / Fe 2+ Mix the solutions and add ascorbic acid to prevent oxidation to obtain a mixed solution of metal salts;
[0016] (1.2) Prepare a precipitant solution by mixing ammonium oxalate and ammonia water;
[0017] (1.3) Inject the metal salt solution into the reaction chamber of the microwave reactor; simultaneously inject the precipitant at a preset flow rate and control the pH at a preset value, setting the microwave reaction program in stages to obtain a uniformly nucleated Mn. 2+ / Fe 2+ Precursor;
[0018] (1.4) The Mn core is homogeneous 2+ / Fe 2+ The precursor is post-processed to obtain (Mn) 0.7 Fe 0.3 C2O4 precursor.
[0019] Preferably, in step (1.1), Mn 2+ / Fe 2+ The concentration of the mixed solution is 0.5-1.0 mol / L, wherein the molar ratio of Mn:Fe is 7:3;
[0020] In step (1.2), the pH of the prepared precipitant solution is 4.0-6.5.
[0021] Preferably, the microwave reaction procedure in step (1.3) specifically includes a microwave-initiated nucleation stage and a microwave power-reducing growth stage;
[0022] The microwave-initiated nucleation stage is as follows: under 800W microwave power, the reaction is carried out at a working time of 5s and an intermittent time of 2s, the precipitant is injected at a flow rate of 8mL / min, and the pH is controlled to increase from 4.8 to 5.6 at a gradient of 0.5 / min until the solution changes from clear to milky white;
[0023] During the microwave power reduction growth stage, when the solution changes from clear to milky white, the microwave power is reduced to 300W for continuous irradiation, the pH is raised to the target value of 6, sodium polyacrylate dispersant is added, and the reaction time is 38-42 minutes.
[0024] Preferred post-processing conditions are:
[0025] Centrifuge at 3000 rpm for 5 min; then wash three times with ethanol, and dry under vacuum at 60 °C for 4 h to obtain (Mn)0.7 Fe 0.3 C2O4 precursor.
[0026] Preferably, step (2) specifically includes:
[0027] At room temperature, the rheological medium is injected into the reactor, and lithium dihydrogen phosphate is added in batches while stirring at 500 rpm. After forming a transparent gel, an ethanol solution of the doped system is added to obtain a premixed solution.
[0028] Heat to 88-92℃, reduce rotation speed to 300rpm, and slowly add the (Mn) obtained in step (1). 0.7 Fe 0.3 The C2O4 precursor undergoes a mesophilic shear reaction;
[0029] Continue heating to 113-117℃, reduce the rotation speed to 150rpm, and carry out a high-temperature activated rheological phase reaction for 3 hours to form a paste-like precursor complex.
[0030] Preferably, in the medium-temperature shear reaction process, the viscosity change rate is monitored in real time to be ≤5% / min;
[0031] During the high-temperature activated rheophase reaction, the pH value was maintained at 3.8-4.2;
[0032] The conductivity is stable at 25±2 mS / cm.
[0033] Preferably, the rheological medium is a mixture of polyethylene glycol 200 and glycerol in a mass ratio of 3:1 to 5:1;
[0034] The molar ratio of Li:Fe+Mn is 1.05:1;
[0035] The doping system includes: a mixed lattice stabilizing system of NbCl5 and Mg(CH3COO)2, and an oxygen vacancy inducer NH4VO3; wherein the total doping amount of the mixed lattice stabilizing system is 1-3 at, and the total doping amount of the oxygen vacancy inducer NH4VO3 is 0.5-1.5 at.
[0036] Preferably, step (3) specifically includes:
[0037] The paste-like precursor composite was heated to 350-450℃ at 5℃ / min under nitrogen protection and held for 2 hours to complete the crystal phase transformation, thus obtaining the carbon-coated lithium manganese iron phosphate precursor.
[0038] This application also provides a highly uniform lithium manganese iron phosphate precursor, which is prepared using any of the above-described microwave-rheological phase coupling preparation methods for highly uniform lithium manganese iron phosphate precursors.
[0039] The highly uniform lithium manganese iron phosphate precursor is a near-spherical single crystal particle with D50 = 1.5 ± 0.2 μm;
[0040] The precursors Mn2+, Fe2+, and multi-element dopants are atomically uniformly distributed in the olivine lattice; the presence of a certain concentration of oxygen vacancies and a high proportion of (010) crystal planes in the material significantly improves the lithium-ion diffusion coefficient.
[0041] The beneficial effects of this application are:
[0042] 1. This application innovatively employs a stepwise preparation method combining microwave-assisted nucleation, rheological phase reaction, and defect engineering in-situ doping to prepare a highly uniform, near-spherical single-crystal lithium manganese iron phosphate precursor. First, microwave field-induced instantaneous uniform ion nucleation solves the stepwise precipitation problem of Mn / Fe. Then, a non-Newtonian fluid reaction environment is constructed to achieve atomic-level mixing and morphology-oriented control. Simultaneously, lattice stabilizers and oxygen vacancy modifiers are introduced to enhance structural stability.
[0043] 2. The highly uniform precursor prepared by microwave-assisted coprecipitation, combined with the rheological phase reaction medium, provides a synergistic reaction environment for the atomic-level uniform introduction of multi-dopants. The microwave field-induced instantaneous nucleation effect, the rheological phase nano-microreactor effect, and the lattice regulation effect of multi-dopants work together to achieve a simultaneous improvement in the electronic conductivity, ionic conductivity, and structural stability of lithium manganese iron phosphate materials. Attached Figure Description
[0044] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:
[0045] Figure 1 Scanning electron microscope image of the precursor prepared for the embodiments of this application;
[0046] Figure 2 Scanning electron microscope image of the precursor prepared by conventional methods;
[0047] Figure 3 EDS diagram of the precursor prepared for the embodiments of this application;
[0048] Figure 4 XRD patterns of the precursors prepared for the embodiments of this application and the precursors prepared by conventional methods;
[0049] Figure 5 Performance tables of precursors prepared for the embodiments of this application and precursors prepared by conventional methods. Detailed Implementation
[0050] To make the technical solutions and advantages of the embodiments of this application clearer, the exemplary embodiments of this application will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.
[0051] Embodiments of this application provide a microwave-rheological phase coupling preparation method for a highly uniform lithium manganese iron phosphate precursor, comprising the following steps:
[0052] (1) Prepare uniformly nucleated Mn using microwave-assisted coprecipitation method 2+ / Fe 2+ Precursor;
[0053] (2) Mn 2+ / Fe 2+ The precursor, lithium dihydrogen phosphate, and doping system were added to a rheological medium in proportion to construct a non-Newtonian fluid reaction environment for phosphating and multi-component doping in the rheological phase medium, resulting in a paste-like precursor complex.
[0054] (3) The paste-like precursor complex is placed under the first preset conditions for low-temperature crystallization and simultaneous carbon coating to obtain carbon-coated lithium manganese iron phosphate precursor.
[0055] Based on the above scheme, step (1) specifically includes the following steps:
[0056] (1.1) Prepare Mn using MnSO4·H2O and FeSO4·7H2O 2+ / Fe 2+ Mix the solutions and add ascorbic acid to prevent oxidation to obtain a mixed solution of metal salts;
[0057] (1.2) Prepare a precipitant solution by mixing ammonium oxalate and ammonia water;
[0058] (1.3) Inject the metal salt solution into the reaction chamber of the microwave reactor; simultaneously inject the precipitant at a preset flow rate and control the pH at a preset value, setting the microwave reaction program in stages to obtain a uniformly nucleated Mn. 2+ / Fe 2+ Precursor;
[0059] (1.4) The Mn core is homogeneous 2+ / Fe 2+ The precursor is post-processed to obtain (Mn) 0.7 Fe 0.3 C2O4 precursor.
[0060] Based on the above scheme, in step (1.1), Mn 2+ / Fe2+ The concentration of the mixed solution is 0.5-1.0 mol / L, wherein the molar ratio of Mn:Fe is 7:3;
[0061] In step (1.2), the pH of the prepared precipitant solution is 4.0-6.5.
[0062] Based on the above scheme, the microwave reaction procedure in step (1.3) specifically includes a microwave-initiated nucleation stage and a microwave power-reducing growth stage;
[0063] The microwave-initiated nucleation stage is as follows: under 800W microwave power, the reaction is carried out at a working time of 5s and an intermittent time of 2s, the precipitant is injected at a flow rate of 8mL / min, and the pH is controlled to increase from 4.8 to 5.6 at a gradient of 0.5 / min until the solution changes from clear to milky white;
[0064] During the microwave power reduction growth stage, when the solution changes from clear to milky white, the microwave power is reduced to 300W for continuous irradiation, the pH is raised to the target value of 6, sodium polyacrylate dispersant is added, and the reaction time is 38-42 minutes.
[0065] Based on the above scheme, the post-processing conditions are as follows:
[0066] Centrifuge at 3000 rpm for 5 min; then wash three times with ethanol, and dry under vacuum at 60 °C for 4 h to obtain (Mn) 0.7 Fe 0.3 C2O4 precursor.
[0067] Based on the above scheme, step (2) specifically includes:
[0068] At room temperature, the rheological medium is injected into the reactor, and lithium dihydrogen phosphate is added in batches while stirring at 500 rpm. After forming a transparent gel, an ethanol solution of the doped system is added to obtain a premixed solution.
[0069] Heat to 88-92℃, reduce rotation speed to 300rpm, and slowly add the (Mn) obtained in step (1). 0.7 Fe 0.3 The C2O4 precursor undergoes a mesophilic shear reaction;
[0070] Continue heating to 113-117℃, reduce the rotation speed to 150rpm, and carry out a high-temperature activated rheological phase reaction for 3 hours to form a paste-like precursor complex.
[0071] Based on the above scheme, during the medium-temperature shear reaction process, the viscosity change rate is monitored in real time to be ≤5% / min;
[0072] During the high-temperature activated rheophase reaction, the pH value was maintained at 3.8-4.2;
[0073] The conductivity is stable at 25±2 mS / cm.
[0074] Based on the above scheme, the rheological medium is a mixture of polyethylene glycol 200 and glycerol in a mass ratio of 3:1 to 5:1;
[0075] The molar ratio of Li:Fe+Mn is 1.05:1;
[0076] The doping system includes: a mixed lattice stabilizing system of NbCl5 and Mg(CH3COO)2, and an oxygen vacancy inducer NH4VO3; wherein the total doping amount of the mixed lattice stabilizing system is 1-3 at, and the total doping amount of the oxygen vacancy inducer NH4VO3 is 0.5-1.5 at.
[0077] Based on the above scheme, step (3) is as follows:
[0078] The paste-like precursor composite was heated to 350-450℃ at 5℃ / min under nitrogen protection and held for 2 hours to complete the crystal phase transformation, thus obtaining the carbon-coated lithium manganese iron phosphate precursor.
[0079] A highly uniform lithium manganese iron phosphate precursor, characterized in that it is prepared by a microwave-rheological phase coupling preparation method for highly uniform lithium manganese iron phosphate precursor as described in any one of claims 1-9;
[0080] The highly uniform lithium manganese iron phosphate precursor is a near-spherical single crystal particle with D50 = 1.5 ± 0.2 μm;
[0081] The precursors Mn2+, Fe2+, and multi-component dopants are atomically statistically uniformly distributed in the olivine lattice; the presence of a certain concentration of oxygen vacancies and a high proportion of (010) crystal planes in the material significantly improves the lithium-ion diffusion coefficient.
[0082] Example 1
[0083] Step 1: Rheological phase phosphating and doping
[0084] A mixed solution containing 1.0 mol / L Mn2+ and Fe2+ (molar ratio Mn:Fe = 7:3) was prepared using MnSO4·H2O and FeSO4·7H2O, with 0.2 mol / L ascorbic acid added to prevent oxidation; the precipitant was a mixture of ammonium oxalate ((NH4)2C2O4) 1.2 mol / L + ammonia water (NH3·H2O) 2.0 mol / L (pH=4.0), with a flow rate of 5 mL / min.
[0085] The metal salt solution was injected into the reaction chamber of the microwave reactor, and the microwave was turned on (pulse mode: 800W for 5 seconds followed by a 2-second interval); simultaneously, the precipitant was injected at a flow rate of 8 mL / min, and the pH was controlled to increase from 4.8 to 5.6 at a gradient of 0.5 / min; key phenomenon: the solution changed from clear to milky white within 20±3 seconds (proof of transient nucleation).
[0086] Reduce continuous radiation to 300W, raise pH to target value of 6.0; add 0.1wt% sodium polyacrylate (dispersant), reaction time 40 minutes; terminate reaction when slurry solid content reaches 35wt%;
[0087] Quickly transfer to a centrifuge (nitrogen protection), centrifuge at 3000 rpm for 5 min; wash three times with ethanol, and vacuum dry at 60℃ for 4 h to obtain (Mn) 0.7 Fe 0.3 C2O4 precursor.
[0088] Key innovation: Reacting in an 800W microwave field reduces crystal nucleation time to <30 seconds (compared to >5 minutes with conventional stirring).
[0089] Step 2: Rheological phase phosphating and doping
[0090] The precursor, lithium dihydrogen phosphate (Li:Fe+Mn=1.05:1), and dopant were added in proportion to a polyethylene glycol 200 / glycerol (mass ratio 4:1) rheology medium (solid content 60wt%).
[0091] The doped system includes:
[0092] Lattice stabilizer: NbCl5 + Mg(CH3COO)2 (total doping amount 1 at%)
[0093] Oxygen vacancy inducer: NH4VO3 (1.5 at%)
[0094] The mixture was stirred at 100°C for 2 hours to form a paste-like precursor complex.
[0095] ① Premixing stage (room temperature):
[0096] PEG-200 / glycerol was injected into the reactor, and LiH2PO4 was added in batches while stirring at 500 rpm. After forming a transparent gel, an ethanol solution of the dopant was added. The viscosity was controlled at 8000±500 cP (measured at 25℃).
[0097] ② Precursor compounding (intermediate-temperature shear):
[0098] Heat to 90℃, reduce rotation speed to 300 rpm, and slowly add the (Mn0.7Fe0.3)C2O4 precursor obtained in step 1 (feeding rate 20 g / min).
[0099] Key control point: Real-time monitoring of viscosity change rate ≤ 5% / min (to prevent localized solidification)
[0100] ③ Rheological phase reaction (high temperature activation):
[0101] Heat to 115℃, reduce rotation speed to 150 rpm, maintain constant temperature for 3 hours, and take samples for testing every 30 minutes during this period.
[0102] Maintain pH between 3.8 and 4.2 (phosphate buffer).
[0103] The conductivity remained stable at 25 mS / cm (a marker of ion diffusion equilibrium).
[0104] After the reaction is complete, a paste-like precursor complex is formed.
[0105] Step 3: Low-temperature crystallization treatment
[0106] The composite was heated to 450℃ at a rate of 5℃ / min under nitrogen protection.
[0107] The crystal phase transformation is completed after 2 hours of heat treatment, directly obtaining carbon-coated lithium manganese iron phosphate precursor (carbon source from rheological medium pyrolysis).
[0108] Comparative Example 1
[0109] A mixed solution containing 1.0 mol / L Mn²⁺ and Fe²⁺ (molar ratio Mn:Fe = 7:3, x = 0.7) was prepared using MnSO₄·H₂O and FeSO₄·7H₂O, with 0.2 mol / L ascorbic acid added for oxidation prevention. The precipitant was 1.2 mol / L dihydrogen phosphate (NH₄H₂PO), and the complexing agent was 2.0 mol / L ammonia solution (NH₃·H₂O). The metal salt mixed solution, precipitant solution, and ammonia solution were added to the reactor in a co-current drip manner using a peristaltic pump. The pH of the reaction system was stabilized at 6.0-6.5 by adjusting the dropping rate of the ammonia solution in real time, and the reaction temperature was 60℃. The reaction was stopped when the D50 reached 5.0 ± 1 μm. The precursor, manganese iron phosphate, was obtained by filtration and drying. The precursor, lithium dihydrogen phosphate (Li:Fe+Mn=1.05:1), dopant, and glucose (to provide a carbon source) were added to a sand mill in a certain proportion and sand milled (D50<0.3um). The mixture was then spray-dried (inlet air 250℃, outlet air 95℃) to obtain a precursor mixture. The mixture was then sintered at 680℃ under a nitrogen atmosphere to obtain carbon-coated lithium manganese iron phosphate.
[0110] Data Analysis
[0111] ① The content of manganese iron lithium was measured by ICP-OES;
[0112] Coefficient of variation of manganese iron: the average value of (measured manganese content - theoretical manganese content) / theoretical manganese content and (measured iron content - theoretical iron content) / theoretical iron content
[0113] ② The tap density is tested by a tap density tester;
[0114] ③ The proportion of (010) crystal plane is calculated by XRD combined with the Lotgering factor method:
[0115] F(010) = (P - P0) / (1 - P0);
[0116] [[ID=As shown, ICP-OES testing revealed that the iron manganese content in Example 1 was 25.4% and 11.5% (theoretically 25.61% and 11.15%), with a coefficient of variation of 2.57%; the coefficient of variation for iron manganese lithium prepared by the conventional method was 16.05%. This is significantly lower than that of the comparative example prepared by the conventional co-precipitation method.
[0125] like Figure 4 As shown, the XRD test of Example 1 of this application shows that the material has an ideal crystal structure. According to the Lotgering factor method, the (010) crystal plane ratio of the precursor prepared by this method is 82%, which is higher than that of the traditional method. The higher the proportion of this crystal plane, the better the rate performance of the material. Through electronic conductivity test comparison, the sample prepared by this method is 3 orders of magnitude higher than that of the traditional method.
[0126] It is worth noting that the innovative details of this application, including but not limited to the above parameters, such as technical steps and material ratios, are protected by patent.
[0127] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.
[0128] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.
Claims
1. A microwave-rheological phase coupling method for preparing a highly uniform lithium manganese iron phosphate precursor, characterized in that, Includes the following steps: (1) Prepare uniformly nucleated Mn using microwave-assisted coprecipitation method 2+ / Fe 2+ Precursor; (2) Mn 2+ / Fe 2+ The precursor, lithium dihydrogen phosphate, and doping system were added to a rheological medium in proportion to construct a non-Newtonian fluid reaction environment for phosphating and multi-component doping in the rheological phase medium, resulting in a paste-like precursor complex. (3) The paste-like precursor complex is placed under the first preset conditions for low-temperature crystallization and simultaneous carbon coating to obtain carbon-coated lithium manganese iron phosphate precursor.
2. The microwave-rheological phase coupling preparation method for highly uniform lithium manganese iron phosphate precursor according to claim 1, characterized in that, Step (1) specifically includes the following steps: (1.1) Prepare Mn using MnSO4·H2O and FeSO4·7H2O 2+ / Fe 2+ Mix the solutions and add ascorbic acid to prevent oxidation to obtain a mixed solution of metal salts; (1.2) Prepare a precipitant solution by mixing ammonium oxalate and ammonia water; (1.3) Inject the metal salt solution into the reaction chamber of the microwave reactor; simultaneously inject the precipitant at a preset flow rate and control the pH at a preset value, setting the microwave reaction program in stages to obtain uniformly nucleated Mn. 2+ / Fe 2+ Precursor; (1.4) The Mn core is homogeneous 2+ / Fe 2+ The precursor is post-processed to obtain (Mn) 0.7 Fe 0.3 C2O4 precursor.
3. The microwave-rheological phase coupling preparation method for the highly uniform lithium manganese iron phosphate precursor as described in claim 2, characterized in that, In step (1.1), Mn 2+ / Fe 2+ The concentration of the mixed solution is 0.5-1.0 mol / L, wherein the molar ratio of Mn:Fe is 7:3; In step (1.2), the pH of the prepared precipitant solution is 4.0-6.
5.
4. The microwave-rheological phase coupling preparation method for the highly uniform lithium manganese iron phosphate precursor as described in claim 2, characterized in that, The microwave reaction procedure in step (1.3) specifically includes a microwave-initiated nucleation stage and a microwave-power-reduced growth stage. The microwave-initiated nucleation stage is as follows: under 800W microwave power, the reaction is carried out at a working time of 5s and an intermittent time of 2s, the precipitant is injected at a flow rate of 8mL / min, and the pH is controlled to increase from 4.8 to 5.6 at a gradient of 0.5 / min until the solution changes from clear to milky white; During the microwave power reduction growth stage, when the solution changes from clear to milky white, the microwave power is reduced to 300W for continuous irradiation, the pH is raised to the target value of 6, sodium polyacrylate dispersant is added, and the reaction time is 38-42 minutes.
5. The microwave-rheological phase coupling preparation method for the highly uniform lithium manganese iron phosphate precursor as described in claim 2, characterized in that, Post-processing conditions are: Centrifuge at 3000 rpm for 5 min; then wash three times with ethanol, and dry under vacuum at 60 °C for 4 h to obtain (Mn) 0.7 Fe 0.3 C2O4 precursor.
6. The microwave-rheological phase coupling preparation method for the highly uniform lithium manganese iron phosphate precursor as described in claim 1, characterized in that, Step (2) specifically involves: At room temperature, the rheological medium is injected into the reactor, and lithium dihydrogen phosphate is added in batches while stirring at 500 rpm. After forming a transparent gel, an ethanol solution of the doped system is added to obtain a premixed solution. Heat to 88-92℃, reduce rotation speed to 300rpm, and slowly add the (Mn) obtained in step (1). 0.7 Fe 0.3 The C2O4 precursor undergoes a mesophilic shear reaction; Continue heating to 113-117℃, reduce the rotation speed to 150rpm, and carry out a high-temperature activated rheological phase reaction for 3 hours to form a paste-like precursor complex.
7. The microwave-rheological phase coupling preparation method for a highly uniform lithium manganese iron phosphate precursor as described in claim 6, characterized in that, During the intermediate-temperature shear reaction process, the viscosity change rate was monitored in real time to be ≤5% / min; During the high-temperature activated rheophase reaction, the pH value was maintained at 3.8-4.2; The conductivity is stable at 25±2 mS / cm.
8. The microwave-rheological phase coupling preparation method for the highly uniform lithium manganese iron phosphate precursor as described in claim 6, characterized in that, The rheological medium is a mixture of polyethylene glycol 200 and glycerol in a mass ratio of 3:1 to 5:
1. The molar ratio of Li:Fe+Mn is 1.05:1; The doping system includes: a mixed lattice stabilizing system of NbCl5 and Mg(CH3COO)2, and an oxygen vacancy inducer NH4VO3; wherein the total doping amount of the mixed lattice stabilizing system is 1-3 at, and the total doping amount of the oxygen vacancy inducer NH4VO3 is 0.5-1.5 at.
9. The microwave-rheological phase coupling preparation method for the highly uniform lithium manganese iron phosphate precursor as described in claim 1, characterized in that, Step (3) specifically involves: The paste-like precursor composite was heated to 350-450℃ at 5℃ / min under nitrogen protection and held for 2 hours to complete the crystal phase transformation, thus obtaining the carbon-coated lithium manganese iron phosphate precursor.
10. A highly uniform lithium manganese iron phosphate precursor, characterized in that, The precursor of high-uniformity lithium manganese iron phosphate was prepared by microwave-rheological phase coupling method as described in any one of claims 1-9; The highly uniform lithium manganese iron phosphate precursor is a near-spherical single crystal particle with D50 = 1.5 ± 0.2 μm.