Ferromanganese phosphate precursor as well as preparation method and application thereof

Abstract

The invention provides a ferromanganese phosphate precursor and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries, the preparation method of the ferromanganese phosphate precursor comprises the following steps: S1, uniformly mixing a manganese source, an iron source, a phosphorus source, a complexing agent, an oxidizing agent and water, and regulating the pH value to 2-3 to obtain an electrolyte solution; s2, the electrolyte solution is placed in a microwave transmission type reaction tank, pulse potential and microwave radiation are applied, and an electro-deposition reaction is carried out; a working electrode, a platinum counter electrode and a saturated calomel reference electrode are arranged in the permeation type reaction tank; the working electrode comprises a titanium-based current collector and a conductive MOF film coated on the titanium-based current collector; and S3, after deposition is completed, the working electrode is taken out and washed, roasting treatment is conducted in the nitrogen atmosphere, and the ferromanganese phosphate precursor is obtained through air jet pulverization. According to the method, uniform codeposition of the ferromanganese phosphate is realized, and the prepared ferromanganese phosphate precursor is uniform in element distribution, high in tap density and low in impurity content.

Description

Technical Field

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

[0002] Lithium manganese iron phosphate (LiMn) x Fe 1-x Manganese iron phosphate (MnPO4), as an upgraded material for lithium iron phosphate, has become a research hotspot for next-generation lithium-ion battery cathode materials due to its high voltage platform (approximately 4.1V) and improved energy density (theoretical specific capacity close to 170mAh / g). However, its precursor, manganese iron phosphate (MnPO4), remains a challenge. x Fe 1-x The preparation of manganese (Mn) and iron (Fe) faces severe technical challenges. Due to the significant difference in precipitation kinetics between manganese (Mn) and iron (Fe) (the solubility product constants Ksp of iron phosphate and manganese phosphate differ by 2 to 3 orders of magnitude), traditional co-precipitation methods cannot achieve atomic-level homogeneous mixing, resulting in component segregation in the final product and affecting electrochemical performance.

[0003] Existing technologies attempt to address this challenge through various means: Ousai Energy improved the chemical coprecipitation method by employing a segmented pH control and oxidant addition strategy (publication number CN117342534A). This approach aims to optimize the manganese-iron ratio by maintaining the reaction solution temperature at 40.0-110.0℃, controlling the pH within the range of 1.0-8.0, and adding an alkaline neutralizing agent. However, this method has a narrow process parameter window (±0.2 pH units) and struggles to completely suppress the disproportionation reaction of divalent manganese, often leaving approximately 5% Mn residue in the product. 2+ Impurities lead to decreased cycling stability of the final material (capacity retention less than 90% after 100 cycles). Hunan Yuneng (publication number CN118754088A) developed a spray roasting technology based on a vertical high-temperature roasting furnace, which controls the precursor particle size distribution by adjusting the suspension time of droplets in the heating zone (0.5-5 seconds). Although this method achieves precise particle size control (achieving a bimodal distribution), it has extremely high energy consumption (reaction temperature > 600℃) and low product tap density (< 1.2 g / cm³). 3 This limitation restricts the improvement of battery volumetric energy density. Another patent from Hunan Yuneng (CN119349540A) improves the hydrothermal synthesis method by introducing a metal-organic framework (MOF) as a template to prepare a high-tap-density precursor in a secondary hydrothermal reaction. This method improves the material's packing density (tap density reaches 1.8 g / cm³). 3However, incomplete decomposition of MOFs leads to carbon residue (>3wt%), reducing the proportion of active materials, and the process cycle is over 48 hours, making industrialization difficult. Hubei Xingfa (publication number CN118702084A) uses electrodeposition to directly deposit manganese iron phosphate on the working electrode. Theoretically, this method can achieve atomic-level mixing, but in practice, the deposited layer has uneven thickness (edge ​​effect causes ±15% thickness deviation), and the deposition rate is slow (about 0.1 μm / h), making it difficult to meet the needs of large-scale production.

[0004] Existing technologies for preparing manganese iron phosphate generally face two common challenges: one is controlling the valence state of manganese, specifically divalent manganese (Mn). 2+ It is not easily and completely oxidized to trivalent manganese (Mn). 3+ ), while unoxidized Mn 2+ First, it can lead to an imbalance in the phosphorus source ratio; second, it introduces impurities, such as sodium and sulfur, which are difficult to remove completely (Na content is often >0.025wt%), affecting battery cycle life. Therefore, there is an urgent need to develop a new preparation method that can achieve atomic-level uniform mixing of elements, is highly efficient, and is easy to industrialize. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a manganese iron phosphate precursor, its preparation method and application, aiming to solve the technical problems of uneven element distribution, difficulty in controlling manganese valence state and low tap density in the preparation of existing manganese iron phosphate precursors.

[0006] In a first aspect, the present invention provides a method for preparing a manganese iron phosphate precursor, comprising the following steps: S1. Preparation of electrolyte solution: Mix manganese source, iron source, phosphorus source, complexing agent, oxidant and water evenly, adjust the pH to 2~3 to obtain electrolyte solution; S2. Microwave-assisted electrodeposition: An electrolyte solution is placed in a microwave-transparent reaction tank, and a pulsed potential and microwave radiation are applied to carry out the electrodeposition reaction; the transparent reaction tank is equipped with a working electrode, a platinum counter electrode and a saturated calomel reference electrode; the working electrode includes a titanium-based current collector and a conductive MOF film coated on the titanium-based current collector; S3. Post-treatment and crystallization transformation: After deposition, the working electrode is removed and washed, then calcined under a nitrogen atmosphere, and finally pulverized by air jet to obtain the manganese iron phosphate precursor.

[0007] Preferably, in step S1, the manganese source includes at least one of manganese sulfate, manganese nitrate, and manganese chloride, and the concentration of the manganese source is 0.5~1.5 mol / L; The iron source includes at least one of ferric sulfate, ferric chloride, and ferric nitrate, and the concentration of the iron source is 0.5~1.5 mol / L; The phosphorus source includes at least one of phosphoric acid, sodium phosphate, potassium phosphate, ammonium phosphate, diammonium dihydrogen phosphate, and diammonium hydrogen phosphate; the complexing agent includes at least one of citric acid, oxalic acid, tartaric acid, EDTA, malic acid, and gluconic acid. The molar ratio of phosphorus source to complexing agent is 1:0.5~1.2, and the total concentration of phosphorus source and complexing agent is 1.0~2.0 mol / L; The oxidant includes at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate, and the concentration of the oxidant is 0.1~0.5 mol / L.

[0008] Preferably, in step S2, the pulse potential is specifically: cathode pulse -0.8~-1.2V (vs. SCE), duration 50~100ms; anode pulse +0.2~+0.5V (vs. SCE), duration 10~20ms.

[0009] Preferably, in step S2, the power of the microwave radiation is 300~800W and the frequency is 2.45GHz.

[0010] Preferably, in step S2, the electrodeposition reaction temperature is controlled at 40~60℃ and the time is 1~3 hours.

[0011] Preferably, in step S2, the method for preparing the working electrode includes the following steps: uniformly dispersing conductive MOF material in an N-methylpyrrolidone solution containing polyvinylidene fluoride to form a slurry, coating the slurry onto a titanium-based current collector, controlling the dry film thickness to be 20~50μm, and obtaining the working electrode after vacuum drying.

[0012] Preferably, the conductive MOF material is a conductive MOF material obtained by in-situ carbonization and reduction or by loading and modification with metal nanoparticles.

[0013] Preferably, the calcination conditions in step S3 are: calcination at 400~600℃ for 2~4 hours.

[0014] In a second aspect, the present invention provides a manganese iron phosphate precursor, which is prepared by the method for preparing the manganese iron phosphate precursor described in the first aspect.

[0015] Thirdly, the present invention provides a lithium manganese iron phosphate cathode material, which is prepared by sintering a lithium source and the iron manganese phosphate precursor described in the second aspect.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing a manganese-iron phosphate precursor. Through the confinement effect of a conductive MOF template, microwave-electrochemical synergistic enhancement, and precise pulse potential control, atomically uniform co-deposition of manganese-iron phosphate is achieved, resulting in an improved deposition rate and high raw material utilization. The physical properties of the manganese-iron phosphate precursor prepared by this method are optimized, exhibiting a high tap density (1.8-2.2 g / cm³). 3 It has low impurity content (S<50ppm) and a more concentrated particle size distribution (span<0.8).

[0017] The lithium manganese iron phosphate prepared from the manganese iron phosphate precursor described in this invention exhibits excellent electrochemical performance. In half-cell testing, the specific capacity at 0.1C discharge exceeds 155 mAh / g, the capacity retention at 4C rate is higher than 85%, and the capacity decay after 500 cycles is less than 8%. This invention provides a material basis for the development of high-performance lithium manganese iron phosphate batteries. Attached Figure Description

[0018] Figure 1 This is a SEM image of the manganese iron phosphate material obtained in Example 1 of the present invention. Detailed Implementation

[0019] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0020] To address the technical challenges of uneven element distribution, difficulty in controlling manganese valence state, and low tap density in the preparation of existing manganese iron phosphate precursors, this invention provides a manganese iron phosphate precursor, its preparation method, and its applications. By employing a conductive metal-organic framework (MOF) as a template and combining microwave-assisted and electrochemical deposition techniques, uniform co-deposition of manganese iron phosphate is achieved. The resulting manganese iron phosphate precursor exhibits highly uniform element distribution, excellent tap density, and extremely low impurity content, laying a solid foundation for the subsequent preparation of lithium manganese iron phosphate cathode materials.

[0021] In a first aspect, embodiments of the present invention provide a method for preparing a manganese iron phosphate precursor, comprising the following steps: S1. Preparation of electrolyte solution: Mix manganese source, iron source, phosphorus source, complexing agent, oxidant and water evenly, adjust the pH to 2~3 to obtain electrolyte solution; S2. Microwave-assisted electrodeposition: An electrolyte solution is placed in a microwave-transparent reaction tank, and a pulsed potential and microwave radiation are applied to carry out the electrodeposition reaction; the transparent reaction tank is equipped with a working electrode, a platinum counter electrode and a saturated calomel reference electrode; the working electrode includes a titanium-based current collector and a conductive MOF film coated on the titanium-based current collector; S3. Post-treatment and crystallization transformation: After deposition, the working electrode is removed and washed, then calcined under a nitrogen atmosphere, and finally pulverized by air jet to obtain the manganese iron phosphate precursor.

[0022] In the technical solution of this invention embodiment, the porous structure of the conductive MOF film provides a confined deposition space, suppresses dendrite formation, and ensures the uniformity of the deposition layer; microwave-assisted electrodeposition enhances ion mobility through dielectric heating, significantly improving the deposition rate; the oxidant in the electrolyte (taking H2O2 as an example) is reduced to ·OH free radicals in the cathode region, instantly reducing Mn 2+ Oxidized to Mn 3+ (Oxidation efficiency > 99.5%); The manganese iron phosphate precursor prepared by the above method forms a tight interface between the MOF core (size 1~3 μm) and the deposited manganese iron phosphate shell (thickness 0.2~0.5 μm). The MOF-derived carbon coating layer (thickness 2~5 nm) significantly improves the electronic conductivity of the product during subsequent calcination. In practical implementation, the morphology and particle size distribution of the precursor can be flexibly adjusted by precisely controlling the concentration of each component in the electrolyte solution and optimizing the microwave power and pulse potential parameters.

[0023] Furthermore, in some embodiments, in step S1, the manganese source includes at least one of manganese sulfate, manganese nitrate, and manganese chloride; the concentration of the manganese source is 0.5~1.5 mol / L.

[0024] Furthermore, in some embodiments, in step S1, the iron source includes at least one of ferric sulfate, ferric chloride, and ferric nitrate; the concentration of the iron source is 0.5~1.5 mol / L.

[0025] Furthermore, in some embodiments, in step S1, the phosphorus source includes at least one of phosphoric acid, sodium phosphate, potassium phosphate, ammonium phosphate, diammonium dihydrogen phosphate, and diammonium hydrogen phosphate; the complexing agent includes at least one of citric acid, oxalic acid, tartaric acid, EDTA, malic acid, and gluconic acid.

[0026] Furthermore, in some embodiments, in step S1, the molar ratio of phosphorus source to complexing agent is 1:0.5~1.2; the total concentration of phosphorus source and complexing agent is 1.0~2.0 mol / L.

[0027] Furthermore, in some embodiments, in step S1, the oxidant includes at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate; the concentration of the oxidant is 0.1~0.5 mol / L.

[0028] In the technical solution of this invention embodiment, the addition of an oxidant is to ensure that manganese iron maintains its trivalent state.

[0029] Furthermore, in some embodiments, in step S1, the pH adjuster used to adjust the pH to 2-3 includes ammonia.

[0030] In the technical solution of this invention embodiment, adjusting the pH of the electrolyte solution to 2.0-3.0 is to prevent precipitation.

[0031] Furthermore, in some embodiments, in step S2, the pulse potential is specifically: cathode pulse -0.8~-1.2V (vs. SCE), duration 50~100ms; anode pulse +0.2~+0.5V (vs. SCE), duration 10~20ms.

[0032] In the technical solution of this invention embodiment, applying a cathode pulse potential induces Mn 3+ Fe 3+ Migration into MOF channels and application of anodic pulse potential promote phosphate release and deposition.

[0033] Furthermore, in some embodiments, in step S2, the power of the microwave radiation is 300~800W and the frequency is 2.45GHz.

[0034] In the technical solution of this invention embodiment, ion diffusion is enhanced by microwave thermal effect and non-thermal effect (molecular polarization), while concentration polarization is suppressed.

[0035] Furthermore, in some embodiments, in step S2, the electrodeposition reaction temperature is controlled at 40~60°C, and the time is 1~3 hours.

[0036] Furthermore, in some embodiments, step S2, the method for preparing the working electrode includes the following steps: uniformly dispersing conductive MOF material in an N-methylpyrrolidone solution containing polyvinylidene fluoride to form a slurry, coating the slurry onto a titanium-based current collector, controlling the dry film thickness to be 20~50μm, and obtaining the working electrode after vacuum drying.

[0037] Furthermore, in some embodiments, the vacuum drying temperature is 100~120°C.

[0038] Furthermore, in some embodiments, the mass ratio of conductive MOF material to polyvinylidene fluoride is (90~97):(10~3); the concentration of polyvinylidene fluoride in the N-methylpyrrolidone solution containing polyvinylidene fluoride is 3wt%~5wt%.

[0039] Furthermore, in some embodiments, the solid content of the slurry is 45% to 55%.

[0040] Furthermore, in some embodiments, the conductive MOF material is a conductive MOF material obtained by in-situ carbonization reduction or metal nanoparticle loading modification of MOF material.

[0041] Furthermore, in some embodiments, the MOF material includes any one of zinc-based MOF materials, iron-based MOF materials, and cobalt-based MOF materials.

[0042] In the technical solution of this invention embodiment, Fe-based, Zn-based, or Co-based MOFs with open pore structures are used. The conductivity is improved by loading 5-10 nm silver particles or surface carbonization (carbon layer thickness <2 nm). Its porous structure provides confined deposition space, suppresses dendrite formation, and ensures the uniformity of the deposition layer.

[0043] Furthermore, in some embodiments, the calcination conditions in step S3 are: calcination at 400~600℃ for 2~4 hours.

[0044] In the technical solution of this invention embodiment, the calcination treatment transforms the amorphous deposited layer into crystalline Mn. x Fe 1- x PO4, while the MOF template is partially carbonized to form a conductive network.

[0045] Secondly, embodiments of the present invention provide a manganese iron phosphate precursor, which is prepared by the method for preparing the manganese iron phosphate precursor described in the first aspect.

[0046] Thirdly, embodiments of the present invention provide a lithium manganese iron phosphate cathode material, which is prepared by sintering a lithium source and the iron manganese phosphate precursor described in the second aspect.

[0047] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0048] Example 1 A method for preparing a manganese iron phosphate precursor includes the following steps: (1) Preparation of conductive MOF template: 5g of MIL-100(Fe) was dispersed in 0.1mol / L silver nitrate solution and reduced by ultraviolet light for 30 minutes, so that Ag nanoparticles were deposited on the MOF surface with a loading of 5wt%. After filtration and drying, conductive MOF template material MIL-100(Fe)@Ag was obtained.

[0049] (2) Preparation of working electrode: MIL-100(Fe)@Ag was uniformly dispersed in an N-methylpyrrolidone (NMP) solution containing polyvinylidene fluoride (PVDF, 5wt%) to form a slurry with a solid content of 50%, wherein the mass ratio of MIL-100(Fe)@Ag to PVDF was 95:5. The slurry was coated on a titanium mesh (100mm×100mm, thickness 0.1mm), and the dry film thickness was controlled to be 30μm. The slurry was vacuum dried at 120℃ for 12 hours to form the working electrode.

[0050] (3) Preparation of electrolyte solution: Dissolve manganese sulfate and ferric sulfate in deionized water, add phosphoric acid, citric acid and hydrogen peroxide, stir evenly, add ammonia water to adjust the pH to 2.5, and prepare electrolyte solution, which contains 1.0 mol / L MnSO4, 1.0 mol / L Fe2(SO4)3, 2.0 mol / L H3PO4, 1.0 mol / L citric acid and 0.3 mol / L H2O2.

[0051] (4) Microwave-assisted electrodeposition: The above-mentioned working electrode, platinum counter electrode, and saturated calomel reference electrode form a three-electrode system, which is placed in a specially designed microwave-transmitting reaction tank. An electrolyte solution is added to the reaction tank, and a pulsed electrodeposition potential and microwave radiation are applied to carry out the electrodeposition reaction. The deposition temperature is controlled at 45℃, and the deposition time is 2 hours. Among them, the cathode pulse is -1.0V (vs. SCE) with a duration of 80ms; the anode pulse is +0.3V (vs. SCE) with a duration of 15ms; the microwave radiation frequency is 2.45GHz, and the power is 500W.

[0052] (5) Post-treatment and crystallization transformation: After deposition, the working electrode is removed, rinsed with deionized water to remove loose deposits, and calcined at 550℃ for 3 hours under nitrogen protection at a rate of 5℃ / min to transform the amorphous deposited layer into crystalline manganese iron phosphate (Mn). x Fe 1-x PO4, while the MOF template is partially carbonized to form a conductive network, and finally manganese iron phosphate precursor powder is obtained by air jet milling.

[0053] Example 2 A method for preparing a manganese iron phosphate precursor includes the following steps: (1) Preparation of conductive MOF template: 5g of ZIF-8 was carbonized in situ at 700℃ for 2h to obtain a porous carbon skeleton, which was used as conductive MOF template material.

[0054] (2) Preparation of working electrode: The carbonized ZIF-8 is uniformly dispersed in an N-methylpyrrolidone (NMP) solution containing polyvinylidene fluoride (PVDF, 5wt%) to form a slurry with a solid content of 50%. The mass ratio of carbonized ZIF-8 to PVDF is 95:5. The slurry is coated on a titanium mesh (100mm×100mm, thickness 0.1mm), and the dry film thickness is controlled to be 30μm. The slurry is vacuum dried at 120℃ for 12 hours to form the working electrode.

[0055] (3) Preparation of electrolyte solution: Dissolve manganese nitrate and ferric chloride in deionized water, add phosphoric acid, citric acid and hydrogen peroxide, stir evenly, add ammonia water to adjust the pH to 2.0, and prepare electrolyte solution, which contains 0.8 mol / L Mn(NO3)2, 0.8 mol / L FeCl3, 1.5 mol / L H3PO4, 1.2 mol / L citric acid and 0.4 mol / L H2O2.

[0056] (4) Microwave-assisted electrodeposition: The above-mentioned working electrode, platinum counter electrode, and saturated calomel reference electrode form a three-electrode system, which is placed in a specially designed microwave-transmitting reaction tank. An electrolyte solution is added to the reaction tank, and pulsed electrodeposition potential and microwave radiation are applied to carry out the electrodeposition reaction. The deposition temperature is controlled at 40℃, and the deposition time is 3 hours. Among them, the cathode pulse is -0.8V (vs. SCE) and the duration is 100ms; the anode pulse is +0.2V (vs. SCE) and the duration is 20ms; the microwave radiation frequency is 2.45GHz and the power is 300W.

[0057] (5) Post-treatment and crystallization transformation: After deposition, the working electrode is removed, rinsed with deionized water to remove loose deposits, and calcined at 400℃ for 4 hours under nitrogen protection at a rate of 5℃ / min to transform the amorphous deposited layer into crystalline manganese iron phosphate (Mn). x Fe 1-x PO4, while the MOF template is partially carbonized to form a conductive network, and finally manganese iron phosphate precursor powder is obtained by air jet milling.

[0058] Example 3 A method for preparing a manganese iron phosphate precursor includes the following steps: (1) Preparation of conductive MOF template: 5g of ZIF-67 was carbonized in situ at 700℃ for 2h to obtain a porous carbon framework. The carbonized ZIF-67 was dispersed in 0.1mol / L copper nitrate solution and reduced by ultraviolet light for 30 minutes to deposit Cu nanoparticles on the MOF surface with a loading of 8wt%. After filtration and drying, conductive MOF template material ZIF-67@Cu was obtained.

[0059] (2) Preparation of working electrode: ZIF-67@Cu was uniformly dispersed in N-methylpyrrolidone (NMP) solution containing polyvinylidene fluoride (PVDF, 5wt%) to form a slurry with a solid content of 50%. The mass ratio of ZIF-8 to PVDF after carbonization was 95:5. The slurry was coated on a titanium mesh (100mm×100mm, thickness 0.1mm), and the dry film thickness was controlled to be 30μm. The slurry was vacuum dried at 120℃ for 12 hours to form the working electrode.

[0060] (3) Preparation of electrolyte solution: Dissolve manganese sulfate and ferric sulfate in deionized water, add phosphoric acid, citric acid and hydrogen peroxide, stir evenly, add ammonia water to adjust the pH to 3.0, and prepare electrolyte solution, which contains 1.2 mol / L MnSO4, 0.8 mol / L Fe2(SO4)3, 2.5 mol / L H3PO4, 0.8 mol / L citric acid and 0.5 mol / L H2O2.

[0061] (4) Microwave-assisted electrodeposition: The above-mentioned working electrode, platinum counter electrode, and saturated calomel reference electrode form a three-electrode system, which is placed in a specially designed microwave-transmitting reaction tank. An electrolyte solution is added to the reaction tank, and a pulsed electrodeposition potential and microwave radiation are applied to carry out the electrodeposition reaction. The deposition temperature is controlled at 60℃, and the deposition time is 1.5 hours. Among them, the cathode pulse is -1.2V (vs. SCE) with a duration of 50ms; the anode pulse is +0.5V (vs. SCE) with a duration of 10ms; the microwave radiation frequency is 2.45GHz, and the power is 800W.

[0062] (5) Post-treatment and crystallization transformation: After deposition, the working electrode is removed, rinsed with deionized water to remove loose deposits, and calcined at 600℃ for 2 hours under nitrogen protection at a rate of 5℃ / min to transform the amorphous deposited layer into crystalline manganese iron phosphate (Mn). x Fe 1-x PO4, while the MOF template is partially carbonized to form a conductive network, and finally manganese iron phosphate precursor powder is obtained by air jet milling.

[0063] Example 4 A method for preparing a manganese iron phosphate precursor includes the following steps: (1) Preparation of conductive MOF template: Same as in Example 1; (2) Preparation of working electrode: Same as in Example 1; (3) Preparation of electrolyte solution: Dissolve manganese sulfate and ferric sulfate in deionized water, add phosphoric acid, citric acid and hydrogen peroxide, stir evenly, add ammonia water to adjust the pH to 2.5, and prepare electrolyte solution, which contains 1.5 mol / L MnSO4, 0.5 mol / L Fe2(SO4)3, 2.0 mol / L H3PO4, 1.0 mol / L citric acid and 0.3 mol / L H2O2.

[0064] (4) Microwave-assisted electrodeposition: The deposition parameters are the same as in Example 1.

[0065] (5) Post-processing and crystallization transformation: Same as in Example 1.

[0066] Example 5 A method for preparing a manganese iron phosphate precursor includes the following steps: (1) Preparation of conductive MOF template: Same as in Example 1; (2) Preparation of working electrode: Same as in Example 1; (3) Preparation of electrolyte solution: Dissolve manganese sulfate and ferric sulfate in deionized water, add phosphoric acid, citric acid and hydrogen peroxide, stir evenly, add ammonia water to adjust the pH to 2.5, and prepare electrolyte solution, which contains 1 mol / L MnSO4, 1.0 mol / L Fe2(SO4)3, 1.8 mol / L H3PO4, 1.0 mol / L citric acid and 0.3 mol / L H2O2.

[0067] (4) Microwave-assisted electrodeposition: The deposition parameters are the same as in Example 1.

[0068] (5) Post-processing and crystallization transformation: Same as in Example 1.

[0069] Comparative Example 1 The preparation of manganese iron phosphate precursor using the traditional co-precipitation method is referenced in the Osai Energy patent (CN117342534A): Manganese sulfate and ferric sulfate were mixed in a ratio of Mn:Fe = 1:1 to form a solution (total metal 1.0 mol / L). This solution was added to a reactor in parallel with 1.0 mol / L phosphoric acid. Then, 0.3 mol / L hydrogen peroxide was added to the solvent to obtain the first reaction solution. The pH was adjusted to 2.0, the temperature was 60℃, and the reaction was carried out for 4 hours. Solid-liquid separation was performed, and the solid material was dried at 130.0℃ for 1.0 hour. The dried solid material was then subjected to crystal transformation treatment at 500.0℃ for 7.0 hours. After the crystal transformation treatment was completed, manganese iron phosphate precursor material was obtained.

[0070] Comparative Example 2 The difference between this comparative example and Example 1 is that microwave radiation is turned off, and only pulse electrodeposition (with the same parameters) is performed.

[0071] Performance testing 1. Physicochemical index testing The physicochemical properties of the manganese iron phosphate precursor materials prepared in Examples 1-5 and Comparative Examples 1-2 were tested. The elemental content was analyzed by ICP, and the particle size distribution range was (D90-D10) / D50. The test results are shown in Table 1.

[0072] Table 1

[0073] Table 1 shows that the manganese iron phosphate precursor materials prepared in Examples 1 to 5 exhibit significant advantages in key physicochemical indicators, especially in the precise control of elemental ratios and the uniformity of particle size distribution. The comparison demonstrates that microwave-assisted electrodeposition technology effectively improves the deposition rate and tap density of the material, while reducing the residue of impurity elements. This is crucial for improving the purity and performance of the final product.

[0074] The sample prepared using the traditional co-precipitation method in Comparative Example 1 showed poor performance in terms of particle size distribution range and tap density. In contrast, Comparative Example 2, after microwave radiation was turned off, retained the advantages of pulsed electrodeposition, but the deposition rate decreased significantly, indicating that the microwave field plays an irreplaceable role in promoting reaction kinetics and crystal quality.

[0075] 2. Performance Testing of Lithium Manganese Iron Phosphate Batteries Prepared with Different Precursors The precursors of Examples 1-5 and Comparative Examples 1-2 were mixed with lithium carbonate at a ratio of Li:(Mn+Fe)=1.05:1 and sintered at 750°C under nitrogen for 12 hours to prepare lithium manganese iron phosphate cathode material. The mixture was then coated to form 18650 batteries (nominal capacity 2000mAh). The electrochemical performance was tested, and the test results are shown in Table 2.

[0076] Table 2. Performance comparison of lithium manganese iron phosphate batteries prepared with different precursors

[0077] Test results show that the manganese iron phosphate precursor prepared by this invention is significantly superior to traditional methods in terms of specific capacity, rate performance, cycle stability, and electrode tap density, especially in terms of high tap density (>1.9 g / cm³). 3 The resulting high compaction density (>2.48 g / cm³) 3 This laid the foundation for improving the volumetric energy density of batteries.

[0078] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for preparing a manganese iron phosphate precursor, characterized in that, Includes the following steps: S1. Preparation of electrolyte solution: Mix manganese source, iron source, phosphorus source, complexing agent, oxidant and water evenly, adjust the pH to 2~3 to obtain electrolyte solution; S2. Microwave-assisted electrodeposition: The electrolyte solution is placed in a microwave-transparent reaction tank, and a pulsed potential and microwave radiation are applied to perform an electrodeposition reaction; the transparent reaction tank is provided with a working electrode, a platinum counter electrode and a saturated calomel reference electrode; the working electrode includes a titanium-based current collector and a conductive MOF film coated on the titanium-based current collector; S3. Post-treatment and crystallization transformation: After deposition, the working electrode is removed and washed, calcined in a nitrogen atmosphere, and then pulverized by airflow to obtain the manganese iron phosphate precursor.

2. The method for preparing a manganese iron phosphate precursor according to claim 1, characterized in that, In step S1, the manganese source includes at least one of manganese sulfate, manganese nitrate, and manganese chloride, and the concentration of the manganese source is 0.5~1.5 mol / L. And / or, the iron source includes at least one of ferric sulfate, ferric chloride, and ferric nitrate, and the concentration of the iron source is 0.5~1.5 mol / L; And / or, the phosphorus source includes at least one of phosphoric acid, sodium phosphate, potassium phosphate, ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; And / or, the complexing agent includes at least one of citric acid, oxalic acid, tartaric acid, EDTA, malic acid, and gluconic acid; And / or, the molar ratio of the phosphorus source to the complexing agent is 1:(0.5~1.2), and the total concentration of the phosphorus source and the complexing agent is 1.0~2.0 mol / L; And / or, the oxidant includes at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate, and the concentration of the oxidant is 0.1~0.5 mol / L.

3. The method for preparing a manganese iron phosphate precursor according to claim 1, characterized in that, In step S2, the pulse potential is specifically: the cathode pulse is -0.8~-1.2V (vs. SCE) with a duration of 50~100ms, and the anode pulse is +0.2~+0.5V (vs. SCE) with a duration of 10~20ms.

4. The method for preparing a manganese iron phosphate precursor according to claim 1, characterized in that, In step S2, the power of the microwave radiation is 300~800W and the frequency is 2.45GHz.

5. The method for preparing a manganese iron phosphate precursor according to claim 1, characterized in that, In step S2, the electrodeposition reaction temperature is controlled at 40~60℃ and the time is 1~3 hours.

6. The method for preparing a manganese iron phosphate precursor according to claim 1, characterized in that, In step S2, the method for preparing the working electrode includes the following steps: uniformly dispersing conductive MOF material in an N-methylpyrrolidone solution containing polyvinylidene fluoride to form a slurry, coating the slurry onto a titanium-based current collector, controlling the dry film thickness to be 20~50μm, and obtaining the working electrode after vacuum drying.

7. The method for preparing a manganese iron phosphate precursor according to claim 6, characterized in that, The conductive MOF material is a conductive MOF material obtained by in-situ carbonization and reduction or metal nanoparticle loading modification of MOF material.

8. The method for preparing a manganese iron phosphate precursor according to claim 1, characterized in that, In step S3, the calcination conditions are: calcination at 400~600℃ for 2~4 hours.

9. The manganese iron phosphate precursor prepared by the method for preparing the manganese iron phosphate precursor according to any one of claims 1 to 8.

10. A lithium manganese iron phosphate cathode material, characterized in that, The lithium manganese iron phosphate cathode material is prepared by sintering a lithium source and the iron manganese phosphate precursor as described in claim 8.

Images