Preparation process of high-cycle vanadium phosphate manganese lithium iron electrode material

Abstract

The application relates to the technical field of electrode materials, in particular to a preparation process of a high-cycle vanadium-manganese-lithium-iron phosphate electrode material, which comprises the following steps: preparing a premixed slurry containing lithium, iron, manganese, vanadium and the like raw materials, a carbon source and a nitrogen dopant; obtaining a primary precursor through pre-crystallization and suction filtration drying; preparing a core phase hierarchical structure precursor through a step-by-step hydrothermal reaction to realize fluorine-nitrogen-phosphorus ternary doping; adding a composite coating agent and a secondary carbon source to obtain a mixture; obtaining a primary product by gradient calcining the mixture in a dynamic atmosphere; and obtaining a finished product by ball milling and low-temperature annealing after adding a passivator. The electrode material prepared by the method has excellent electrochemical performance and structural stability, high cycle retention rate, strong electron and ion transmission capacity, can inhibit ion elution, and has low interface impedance; the process has good synergism, overcomes the limitations of traditional methods, improves the practicability of the material, and can be widely applied to the field of energy storage batteries.

Description

Technical Field

[0001] This invention relates to the field of electrode material technology, specifically to a process for preparing high-cycle lithium vanadium manganese iron phosphate electrode material. Background Technology

[0002] As a core component of clean energy storage, the performance of electrode materials directly determines the overall quality of lithium-ion batteries. Lithium iron phosphate (LFP) electrode materials combine the structural stability of lithium iron phosphate with the high voltage platform of lithium manganese phosphate. Furthermore, the introduction of vanadium broadens the ion transport channels, making it a preferred cathode material that combines high energy density and high safety, with broad application prospects in power batteries and energy storage batteries. However, the industrial application of this material is still limited by many technical bottlenecks, and existing preparation processes cannot meet the actual requirements for high cycle performance.

[0003] In existing technologies, the preparation of lithium vanadium manganese iron phosphate (LiFePO4) mainly employs conventional processes such as solid-state methods and hydrothermal methods. The raw material mixing stage often involves only dry or wet grinding, making it difficult to achieve atomically uniform distribution of elements such as lithium, iron, manganese, and vanadium. The complex raw material composition also easily triggers side reactions, leading to poor batch-to-batch consistency. Furthermore, the material's inherent low electronic conductivity and slow lithium-ion diffusion rate remain unresolved. Conventional modification methods such as nano-sizing, single carbon coating, or binary doping can only improve material performance in one aspect and cannot achieve synergistic effects. During cycling, the Jahn-Teller effect of manganese easily induces crystal structure distortion, and the significant manganese ion dissolution problem leads to lattice collapse and accelerated capacity decay.

[0004] In terms of process details, existing hydrothermal reactions mostly employ isothermal modes, resulting in a lack of controlled grain growth and the formation of unevenly sized particles, affecting compaction density and energy density. Coating modification often involves single-substrate coating, leading to weak adhesion between the coating layer and the matrix, making it prone to detachment during cycling and failing to effectively suppress manganese dissolution and electrolyte side reactions. The calcination stage often uses a fixed atmosphere, making it difficult to simultaneously optimize crystal structure and achieve solid solution effects for dopants, and lacks subsequent surface passivation treatment, resulting in poor interfacial stability between the material and the electrolyte. Furthermore, existing processes lack sufficient diffusion control of dopants, making it difficult for dopant ions to uniformly enter the crystal lattice, significantly reducing the modification effect. In summary, existing preparation processes cannot address the performance shortcomings of lithium vanadium manganese iron phosphate from multiple dimensions, including raw material mixing, crystal structure control, structural modification, and interface optimization. Developing a multi-faceted, synergistic modification process for high-cycle lithium vanadium manganese iron phosphate electrode materials has become a pressing technical challenge for the industry. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a process for preparing high-cycle lithium iron phosphate vanadium manganese iron electrode materials.

[0007] (II) Technical Solution

[0008] A process for preparing a high-cycle lithium iron phosphate vanadium manganese phosphate electrode material includes the following steps:

[0009] S1. Weigh the lithium source, phosphoric acid source, iron source, manganese source, vanadium source, fluorine source, and phosphorus dopant. Mix the above raw materials with the composite carbon source and nitrogen dopant. First, dry grind them in a planetary ball mill, then add anhydrous ethanol to adjust the material-liquid ratio and wet grind them. The ball milling medium is zirconium oxide balls to obtain a premixed slurry with uniform particle size.

[0010] S2. Transfer the premixed slurry to a three-necked flask and stir. Heat the mixture to carry out a water bath precrystallization reaction. After the reaction is complete, filter the mixture and dry the filter cake by blowing air to obtain the primary vanadium manganese iron lithium phosphate precursor.

[0011] S3. After mixing the primary precursor with deionized water, transfer it to a hydrothermal reactor. After purging the air in the reactor with argon gas, seal it and use a step-by-step heating mode. After the reaction is completed, allow it to cool naturally to room temperature. After centrifugation and washing, vacuum dry to obtain a fluorine-nitrogen-phosphorus ternary doped nucleophase hierarchical lithium phosphate vanadium manganese iron precursor.

[0012] S4. Mix the nucleus phase fractionation precursor with the composite coating agent and the secondary carbon source, place it in a planetary ball mill for ball milling, and after ball milling, transfer it to a vacuum drying oven for diffusion treatment of doped elements under vacuum conditions to obtain the coated and modified precursor mixture.

[0013] S5. Place the precursor mixture in a tube furnace and pre-calcine it at 350-400℃ in an atmosphere with a nitrogen-argon volume ratio of 7:3. Then switch to an atmosphere with a nitrogen-argon volume ratio of 1:1 and calcine it at a heating rate of 2-3℃ / min to 650-750℃ to obtain the calcined initial product.

[0014] S6. After mixing the initial product with the surface passivating agent, the mixture is ball-milled again and then placed in a tube furnace. Under a pure argon atmosphere, the temperature is raised to 200-300℃ for low-temperature annealing. After annealing, the mixture is naturally cooled to room temperature to obtain a high-cycle lithium vanadium manganese iron phosphate electrode material.

[0015] Preferably, in S1, the molar ratio of lithium source, phosphoric acid source, iron source, manganese source, vanadium source, fluorine source, and phosphorus dopant is Li:(Fe+Mn+V):PO4:F:P=1.02-1.08:0.4-0.6:1:0.01-0.05:0.005-0.02, wherein the molar ratio of iron source, manganese source, and vanadium source is Fe:Mn:V=0.5-0.7:0.2-0.3:0.1-0.2; the dry grinding speed is 400-600 rpm, the dry grinding time is 1-2 h, the wet grinding material-liquid ratio is 1:4-1:6, the wet grinding speed is 300-500 rpm, the wet grinding time is 2-3 h, the ball milling material-ball ratio is 1:8-1:12, the mass fraction of composite carbon source is 5%-10%, and the mass fraction of nitrogen dopant is 0.5%-2%.

[0016] Preferably, the molar ratio of lithium source, phosphoric acid source, iron source, manganese source, vanadium source, fluorine source and phosphorus dopant in S1 is Li:(Fe+Mn+V):PO4:F:P=1.05:0.5:1:0.03:0.01, and the molar ratio of iron source, manganese source and vanadium source is Fe:Mn:V=0.6:0.25:0.15.

[0017] Preferably, in S2, the mechanical stirring rate is 300-500 rpm, the water bath pre-crystallization temperature is 80-100℃, the pre-crystallization reaction time is 4-6 h, the forced-air drying temperature is 80-90℃, and the forced-air drying time is 6-8 h.

[0018] Preferably, the specific parameters for the stepped heating in S3 are as follows: first, the temperature is increased to 120-150℃ at a rate of 2-3℃ / min, and the reaction is held at this temperature for 2-4 hours; then, the temperature is increased to 180-220℃ at a rate of 1-2℃ / min, and the reaction is held at this temperature for 6-10 hours; the vacuum drying temperature is 80-100℃, the vacuum drying time is 10-14 hours, and the vacuum degree of vacuum drying is -0.08 to -0.1 MPa.

[0019] Preferably, in S4, the mass fraction of the composite coating agent is 1%-3%, the mass fraction of the secondary carbon source is 2%-5%, the ball milling speed is 350 rpm, the ball milling time is 1-2 h, the diffusion treatment temperature is 100-120℃, and the diffusion treatment time is 3-5 h.

[0020] Preferably, in step S5, the pre-calcination heating rate is 5-8℃ / min, the pre-calcination time is 2-3h, the high-temperature calcination heating rate is 2-3℃ / min, the high-temperature calcination time is 6-8h, and the gas flow rate inside the tubular furnace is 0.5-1L / min.

[0021] Preferably, the surface passivating agent in S6 has a mass fraction of 0.1%-0.5%, a ball milling time of 0.5-1h, an annealing heating rate of 1-2℃ / min, and an annealing time of 2-4h.

[0022] Preferably, the lithium source is one or more of lithium carbonate, lithium hydroxide, and lithium nitrate; the phosphoric acid source is one or more of ammonium dihydrogen phosphate, phosphoric acid, and diammonium hydrogen phosphate; the iron source is one or more of ferrous oxalate, ferrous sulfate, and ferrous chloride; the manganese source is one or more of manganese carbonate, manganese oxalate, and manganese acetate; the vanadium source is one or more of vanadyl oxalate, ammonium metavanadate, and vanadyl sulfate; the fluorine source is one or more of ammonium fluoride, lithium fluoride, and sodium fluoride; and the phosphorus dopant is one or more of ammonium phosphite and lithium hypophosphite.

[0023] Preferably, the composite carbon source is a mixture of glucose, carbon black, and carboxymethyl cellulose in a mass ratio of 2:1:1 to 3:1:1; the nitrogen dopant is one or more of urea, melamine, and dicyandiamide; the composite coating agent is a mixture of nano-alumina, graphene, and carbon nanotubes in a mass ratio of 3:1:1 to 5:1:1; the secondary carbon source is one or more of citric acid, sucrose, and ascorbic acid; and the surface passivating agent is one or more of lithium borate and ammonium metaborate.

[0024] (iii) Beneficial technical effects

[0025] Compared with existing technologies, the beneficial effects of this invention are:

[0026] 1. The raw material pretreatment stage employs a dry-wet graded ball milling process, which significantly improves the uniformity of raw material mixing compared to conventional single ball milling. This achieves atomic-level uniform distribution of elements such as lithium, iron, manganese, and vanadium, reducing side reactions from the source and improving batch-to-batch consistency. The graded crystallization process, combining pre-crystallization and stepped hydrothermal crystallization, allows for precise control of grain growth, forming a graded structure with reasonable dimensions. This shortens the lithium-ion migration path, increases material compaction density, and improves energy density performance. The combination of fluorine, nitrogen, and phosphorus ternary doping with dopant element diffusion treatment effectively broadens lithium-ion transport channels, improves electronic conductivity and ion diffusion rate, and fundamentally improves the material's rate performance.

[0027] 2. The composite coating layer formed by the dual-phase coating process is firmly bonded to the substrate, is not easily detached, and effectively inhibits manganese ion dissolution and crystal structure distortion, thereby enhancing the material's structural stability. Dynamic atmosphere gradient calcination, through precise control of the atmosphere ratio, heating rate, and calcination temperature, achieves optimized crystal growth, further stabilizing the crystal lattice structure and reducing structural damage during cycling. Surface passivation and low-temperature annealing effectively improve the interfacial characteristics between the material and the electrolyte, forming a dense passivation film, reducing electrolyte side reactions, and enhancing interfacial stability. Attached Figure Description

[0028] Figure 1This is a process flow diagram of a high-cycle lithium iron phosphate vanadium manganese phosphate electrode material disclosed in this invention;

[0029] Figure 2 This is a line graph comparing the capacity retention rates of the embodiment and the comparative example after 1000 cycles;

[0030] Figure 3 This is a bar chart comparing the first discharge specific capacity of the embodiments and the comparative examples;

[0031] Figure 4 This is a radar comparison chart created by standardizing the dimensions of the performance comparison data of the examples and comparative examples. Detailed Implementation

[0032] according to Figures 1 to 4 The specific embodiments of the present invention are as follows:

[0033] Example 1

[0034] S1 Premixed Slurry Preparation

[0035] The molar ratio of Li:(Fe+Mn+V):PO4:F:P = 1.05:0.5:1:0.03:0.01 was used to select lithium, phosphoric acid, iron, manganese, vanadium, fluorine, and phosphorus dopant. The molar ratio of iron, manganese, and vanadium sources was Fe:Mn:V = 0.6:0.25:0.15. The lithium source was lithium carbonate with a purity of 99.9%; the phosphoric acid source was ammonium dihydrogen phosphate with a purity of 99.5%; the iron source was ferrous oxalate with a purity of 99.0%; the manganese source was manganese carbonate with a purity of 99.0%; the vanadium source was vanadium oxyoxalate with a purity of 98.5%; the fluorine source was ammonium fluoride with a purity of 99.0%; and the phosphorus dopant was ammonium phosphite with a purity of 98.0%.

[0036] The composite carbon source is composed of glucose, carbon black, and carboxymethyl cellulose in a mass ratio of 2:1:1, with a mass fraction of 5% of the total mass of the raw materials; the nitrogen dopant is urea with a purity of 99.5%, with a mass fraction of 0.5% of the total mass of the raw materials.

[0037] All the above raw materials were added to a planetary ball mill using zirconia balls with a diameter of 5 mm as the milling media, at a material-to-ball ratio of 1:10. Dry milling was performed first at 500 rpm for 1.5 hours, with a 5-minute stop every 30 minutes to prevent overheating and material agglomeration. After dry milling, 99.7% anhydrous ethanol was added to adjust the material-to-liquid ratio (total raw material mass to anhydrous ethanol volume ratio) to 1:5. Wet milling was then performed at 400 rpm for 2.5 hours, with a 5-minute stop every 30 minutes, ultimately yielding a premixed slurry with uniform particle size (D90) of approximately 5 μm.

[0038] S2 Primary Precursor Preparation

[0039] The premixed slurry was transferred to a three-necked flask, and a double-bladed mechanical stirrer was installed. The stirring speed was set to 400 rpm, and a constant-temperature water bath was turned on. The temperature was slowly increased to 90°C for the pre-crystallization reaction, which lasted for 5 hours. During this period, the slurry was observed every hour to ensure that there was no local clumping. After the reaction, the slurry was filtered using a 0.45 μm ceramic filter membrane. The filter cake was collected and spread evenly in a forced-air drying oven. The drying temperature was set to 85°C, the air velocity to 1.5 m / s, and the drying time to 7 hours. During this period, the filter cake was manually turned every 2 hours to ensure uniform drying, resulting in a loose and porous primary lithium vanadium manganese iron phosphate precursor.

[0040] Preparation of S3 nucleophase hierarchical structure precursor

[0041] Take an appropriate amount of primary precursor and mix it with deionized water with a conductivity ≤10μS / cm. The mixing ratio is 1:4 (g / mL) of primary precursor to deionized water by mass volume. After stirring evenly, transfer the mixture to a high-pressure hydrothermal reactor made of titanium alloy. Introduce 99.99% pure argon gas into the reactor at a flow rate of 1L / min for 30 minutes to completely purge the air from the reactor. Then seal the reactor. Start the reactor heating program using a stepped heating mode: first, heat to 135℃ at a rate of 2.5℃ / min and hold for 3 hours; then heat to 200℃ at a rate of 1.5℃ / min and hold for 8 hours.

[0042] After the reaction was completed, the heating device was turned off, and the reactor was allowed to cool naturally to room temperature. The reactor was opened, and the reaction solution was transferred to a high-speed centrifuge and centrifuged at 8000 rpm for 15 min to collect the precipitate. The precipitate was washed three times with deionized water, adding an equal mass of deionized water to the precipitate each time, stirring thoroughly, and then centrifuged. The precipitate was then washed once with anhydrous ethanol to remove residual water. Subsequently, the precipitate was transferred to a vacuum drying oven, and the vacuum degree was set to -0.09 MPa, the drying temperature to 90℃, and the drying time to 12 h. Finally, a fluorine-nitrogen-phosphorus ternary doped nucleo-phase hierarchical structure vanadium manganese iron lithium phosphate precursor was obtained with a particle size D50 of approximately 2 μm.

[0043] Preparation of S4 coated modified precursor mixture

[0044] Take an appropriate amount of nucleophase fractionation precursor. The composite coating agent is a mixture of nano-alumina, graphene, and carbon nanotubes in a mass ratio of 4:1:1, and its mass fraction is 2% of the mass of the nucleophase fractionation precursor. Citric acid with a purity of 99.5% is selected as the secondary carbon source, and its mass fraction is 3% of the mass of the nucleophase fractionation precursor.

[0045] The nucleus-phase fractionation precursor, composite coating agent, and secondary carbon source were added together into a planetary ball mill. The milling media were zirconia balls with a diameter of 3 mm, a material-to-ball ratio of 1:10, a rotation speed of 350 rpm, and a milling time of 1.5 h. After milling, the mixture was transferred to a vacuum drying oven, where a vacuum degree of -0.08 MPa, a diffusion treatment temperature of 110 °C, and a diffusion treatment time of 4 h were set. During the diffusion treatment, the mixture was manually stirred every 1 h to ensure uniform diffusion of the dopant elements, ultimately yielding a coated and modified precursor mixture.

[0046] Preparation of S5 calcined primary product

[0047] The precursor mixture was transferred to a quartz boat and placed in a tube furnace. A mixture of nitrogen and argon gas, both with a purity of 99.99%, was first introduced into the tube furnace at a volume ratio of 7:3 and a gas flow rate of 0.8 L / min. The temperature was then increased to 380 °C at a heating rate of 6 °C / min for pre-calcination treatment for 2.5 h.

[0048] After pre-calcination, while maintaining a constant gas flow rate, the volume ratio of the mixed gas was switched to 1:1, and the temperature was increased to 700℃ at a rate of 2.5℃ / min for high-temperature calcination for 7 hours. During calcination, the gas flow rate was monitored and adjusted in real time using a gas flow meter to ensure a stable atmosphere. After calcination, the heating device was turned off, and the tube furnace was allowed to cool naturally to room temperature to obtain the initial calcined product.

[0049] S6 High Cycling Electrode Material Preparation

[0050] Take an appropriate amount of the initial product. The surface passivating agent is lithium borate with a purity of 99.0%, and its mass fraction is 0.3% of the initial product mass. Add the initial product and lithium borate together into a planetary ball mill. The ball milling media is zirconia balls with a diameter of 2 mm. The material-to-ball ratio is 1:8. Set the rotation speed to 300 rpm and the ball milling time to 0.8 h.

[0051] After ball milling, the material was transferred to a tube furnace, and 99.99% pure argon gas was introduced at a flow rate of 0.6 L / min. The temperature was increased to 250°C at a rate of 1.5°C / min for low-temperature annealing for 3 hours. After annealing, the material was allowed to cool naturally to room temperature, resulting in a high-cycle lithium vanadium manganese iron phosphate electrode material.

[0052] Example 2

[0053] S1 Premixed Slurry Preparation

[0054] The molar ratio of Li:(Fe+Mn+V):PO4:F:P = 1.06:0.55:1:0.04:0.015 was used to select lithium, phosphoric acid, iron, manganese, vanadium, fluorine, and phosphorus dopant. The molar ratio of iron, manganese, and vanadium sources was Fe:Mn:V = 0.65:0.28:0.17. The lithium source was lithium hydroxide with a purity of 99.8%; the phosphoric acid source was phosphoric acid with a concentration of 85%; the iron source was ferrous sulfate with a purity of 99.0%; the manganese source was manganese oxalate with a purity of 98.5%; the vanadium source was ammonium metavanadate with a purity of 99.0%; the fluorine source was lithium fluoride with a purity of 99.0%; and the phosphorus dopant was lithium hypophosphite with a purity of 98.0%.

[0055] The composite carbon source is composed of glucose, carbon black, and carboxymethyl cellulose in a mass ratio of 3:1:1, with a mass fraction of 8% of the total mass of the raw materials; the nitrogen dopant is melamine with a purity of 99.0%, with a mass fraction of 1.2% of the total mass of the raw materials.

[0056] All the above raw materials were added to a planetary ball mill using zirconia balls with a diameter of 6 mm as the milling media, at a material-to-ball ratio of 1:11. Dry milling was performed first at 550 rpm for 1.8 hours, with a 5-minute stop every 25 minutes. After dry milling, 99.7% anhydrous ethanol was added to adjust the material-to-liquid ratio to 1:5.5, followed by wet milling at 450 rpm for 2.8 hours, with a 5-minute stop every 25 minutes. The final product was a premixed slurry with uniform particle size, with a particle size D90 of approximately 4.5 μm.

[0057] S2 Primary Precursor Preparation

[0058] The premixed slurry was transferred to a three-necked flask, and a three-layer impeller mechanical stirrer was installed. The stirring speed was set to 450 rpm, and a constant temperature water bath was turned on. The temperature was slowly increased to 95°C for the pre-crystallization reaction, which lasted for 5.5 hours. The slurry state was observed every hour during the reaction. After the reaction, the slurry was filtered through a 0.5 μm ceramic filter membrane. The filter cake was collected and spread evenly in a forced-air drying oven. The drying temperature was set to 88°C, the air velocity to 1.8 m / s, and the drying time to 7.5 hours. The filter cake was manually turned every 1.5 hours during the drying process to obtain a loose and porous primary lithium vanadium manganese iron phosphate precursor.

[0059] Preparation of S3 nucleophase hierarchical structure precursor

[0060] Take an appropriate amount of primary precursor and mix it with deionized water with a conductivity ≤10μS / cm. The mixing ratio is 1:4.5 (g / mL) of primary precursor to deionized water. After stirring evenly, transfer the mixture to a high-pressure hydrothermal reactor made of titanium alloy. Introduce 99.995% pure argon gas into the reactor at a flow rate of 1.1L / min for 35 minutes to purge the air from the reactor. Then seal the reactor. Start the heating program using a stepped heating mode: first, heat to 140℃ at a rate of 2.8℃ / min and hold for 3.5 hours; then heat to 210℃ at a rate of 1.8℃ / min and hold for 9 hours.

[0061] After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The reaction solution was then transferred to a high-speed centrifuge and centrifuged at 8500 rpm for 18 min. The precipitate was collected. The precipitate was washed four times with deionized water, with an equal mass of deionized water added each time and the mixture stirred thoroughly before centrifugation. The precipitate was then washed once with anhydrous ethanol. The precipitate was transferred to a vacuum drying oven and dried at a vacuum of -0.095 MPa, a drying temperature of 95 °C, and a drying time of 13 h to obtain a fluorine-nitrogen-phosphorus ternary doped nucleo-phase hierarchical lithium vanadium manganese iron phosphate precursor with a particle size D50 of approximately 1.9 μm.

[0062] Preparation of S4 coated modified precursor mixture

[0063] Take an appropriate amount of nucleophase fractionation precursor. The composite coating agent is a mixture of nano-alumina, graphene, and carbon nanotubes in a mass ratio of 4.5:1:1, and its mass fraction is 2.5% of the mass of the nucleophase fractionation precursor. The secondary carbon source is sucrose with a purity of 99.5% and a mass fraction of 4% of the mass of the nucleophase fractionation precursor.

[0064] The nucleus-phase fractionation precursor, composite coating agent, and secondary carbon source were added together into a planetary ball mill. The milling media were zirconia balls with a diameter of 4 mm, a material-to-ball ratio of 1:11, and the milling speed was set at 350 rpm for 1.8 h. After milling, the mixture was transferred to a vacuum drying oven, where the vacuum degree was set to -0.085 MPa, the diffusion treatment temperature to 115℃, and the diffusion treatment time to 4.5 h. The mixture was manually stirred every 1 h during the process to obtain the coated and modified precursor mixture.

[0065] Preparation of S5 calcined primary product

[0066] The precursor mixture was transferred to a quartz boat and placed in a tube furnace. A mixture of nitrogen and argon gas, both with a purity of 99.99%, at a volume ratio of 7:3 and a gas flow rate of 0.9 L / min, was first introduced. The temperature was then increased to 390 °C at a heating rate of 7 °C / min, and the pre-calcination time was 2.8 h.

[0067] After pre-calcination, while maintaining a constant gas flow rate, the volume ratio of the mixed gas was switched to 1:1, and the temperature was increased to 720℃ at a heating rate of 2.8℃ / min for 7.5 hours. The gas flow rate was monitored in real time during calcination to ensure stability. After calcination, the mixture was allowed to cool naturally to room temperature to obtain the initial calcined product.

[0068] S6 High Cycling Electrode Material Preparation

[0069] Take an appropriate amount of the initial product. The surface passivating agent is ammonium metaborate with a purity of 98.5%, and its mass fraction is 0.4% of the initial product mass. Add the initial product and ammonium metaborate together into a planetary ball mill. The ball milling media are zirconia balls with a diameter of 2 mm, the material-to-ball ratio is 1:9, the speed is set to 320 rpm, and the ball milling time is 0.9 h.

[0070] After ball milling, the material was transferred to a tube furnace, and 99.99% pure argon gas was introduced at a flow rate of 0.7 L / min. The temperature was increased to 280°C at a rate of 1.8°C / min for low-temperature annealing for 3.5 hours. After annealing, the material was allowed to cool naturally to room temperature to obtain a high-cycle lithium vanadium manganese iron phosphate electrode material.

[0071] Example 3

[0072] S1 Premixed Slurry Preparation

[0073] The molar ratio of Li:(Fe+Mn+V):PO4:F:P = 1.03:0.45:1:0.02:0.008 was used to select lithium, phosphoric acid, iron, manganese, vanadium, fluorine, and phosphorus dopant. The molar ratio of iron, manganese, and vanadium sources was Fe:Mn:V = 0.55:0.22:0.13. The lithium source was lithium nitrate with a purity of 99.5%; the phosphoric acid source was diammonium hydrogen phosphate with a purity of 99.5%; the iron source was ferrous chloride with a purity of 98.5%; the manganese source was manganese acetate with a purity of 99.0%; the vanadium source was vanadium oxysulfate with a purity of 98.0%; the fluorine source was sodium fluoride with a purity of 99.0%; and the phosphorus dopant was ammonium phosphite with a purity of 98.0%.

[0074] The composite carbon source is composed of glucose, carbon black, and carboxymethyl cellulose mixed in a mass ratio of 2.5:1:1, with a mass fraction of 6% of the total mass of the raw materials; the nitrogen dopant is dicyandiamide with a purity of 99.0%, and a mass fraction of 0.8% of the total mass of the raw materials.

[0075] All the above raw materials were added to a planetary ball mill using zirconia balls with a diameter of 4 mm as the milling media, at a material-to-ball ratio of 1:9. Dry milling was performed first at 450 rpm for 1.2 hours, with a 5-minute stop every 30 minutes. After dry milling, 99.7% anhydrous ethanol was added to adjust the material-to-liquid ratio to 1:4.5, followed by wet milling at 350 rpm for 2.2 hours, with a 5-minute stop every 30 minutes. The final product was a premixed slurry with uniform particle size, with a particle size D90 of approximately 5.5 μm.

[0076] S2 Primary Precursor Preparation

[0077] The premixed slurry was transferred to a three-necked flask, and a double-bladed mechanical stirrer was installed. The stirring speed was set to 350 rpm, and a constant-temperature water bath was turned on. The temperature was slowly increased to 85°C for the pre-crystallization reaction, which lasted for 4.5 hours. The slurry state was observed every hour during the reaction. After the reaction, the slurry was filtered through a 0.4 μm ceramic membrane. The filter cake was collected and spread evenly in a forced-air drying oven. The drying temperature was set to 82°C, the air velocity to 1.2 m / s, and the drying time to 6.5 hours. The filter cake was manually turned every 2 hours during the drying process to obtain a loose and porous primary lithium vanadium manganese iron phosphate precursor.

[0078] Preparation of S3 nucleophase hierarchical structure precursor

[0079] Take an appropriate amount of primary precursor and mix it with deionized water with a conductivity ≤10μS / cm. The mixing ratio is 1:3.5 (g / mL) of primary precursor to deionized water. After stirring evenly, transfer the mixture to a high-pressure hydrothermal reactor made of titanium alloy. Introduce 99.99% pure argon gas into the reactor at a flow rate of 0.9L / min for 28 minutes to purge the air from the reactor. Then seal the reactor. Start the heating program using a stepped heating mode: first, heat to 130℃ at a rate of 2.2℃ / min and hold for 2.5 hours; then heat to 190℃ at a rate of 1.2℃ / min and hold for 7 hours.

[0080] After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The reaction solution was then transferred to a high-speed centrifuge and centrifuged at 7500 rpm for 12 min. The precipitate was collected. The precipitate was washed three times with deionized water, with an equal mass of deionized water added each time and the mixture stirred thoroughly before centrifugation. The precipitate was then washed once with anhydrous ethanol. The precipitate was transferred to a vacuum drying oven and dried at a vacuum of -0.085 MPa, a drying temperature of 85 °C, and a drying time of 11 h to obtain a fluorine-nitrogen-phosphorus ternary doped nucleo-hierarchical vanadium manganese iron lithium phosphate precursor with a particle size D50 of approximately 2.1 μm.

[0081] Preparation of S4 coated modified precursor mixture

[0082] Take an appropriate amount of nucleophase fractionation precursor. The composite coating agent is a mixture of nano-alumina, graphene, and carbon nanotubes in a mass ratio of 3.5:1:1, and its mass fraction is 1.5% of the mass of the nucleophase fractionation precursor. The secondary carbon source is ascorbic acid with a purity of 99.0% and a mass fraction of 2.5% of the mass of the nucleophase fractionation precursor.

[0083] The nucleus-phase fractionation precursor, composite coating agent, and secondary carbon source were added together into a planetary ball mill. The milling media were zirconia balls with a diameter of 3 mm, a material-to-ball ratio of 1:9, a rotation speed of 350 rpm, and a milling time of 1.2 h. After milling, the mixture was transferred to a vacuum drying oven, where a vacuum degree of -0.08 MPa, a diffusion treatment temperature of 105 °C, and a diffusion treatment time of 3.5 h were set. The mixture was manually stirred every 1 h during the process to obtain the coated and modified precursor mixture.

[0084] Preparation of S5 calcined primary product

[0085] The precursor mixture was transferred to a quartz boat and placed in a tube furnace. A mixture of nitrogen and argon gas, both with a purity of 99.99%, at a volume ratio of 7:3 and a gas flow rate of 0.6 L / min, was introduced. The temperature was increased to 360 °C at a heating rate of 5.5 °C / min, and the pre-calcination time was 2.2 h.

[0086] After pre-calcination, while maintaining a constant gas flow rate, the volume ratio of the mixed gas was switched to 1:1, and the temperature was increased to 680℃ at a heating rate of 2.2℃ / min for 6.5 hours. The gas flow rate was monitored in real time during calcination to ensure stability. After calcination, the mixture was allowed to cool naturally to room temperature to obtain the initial calcined product.

[0087] S6 High Cycling Electrode Material Preparation

[0088] Take an appropriate amount of the initial product. The surface passivating agent is lithium borate with a purity of 99.0%, and its mass fraction is 0.2% of the initial product mass. Add the initial product and lithium borate together into a planetary ball mill. The ball milling media is zirconia balls with a diameter of 2 mm. The material-to-ball ratio is 1:8. Set the rotation speed to 280 rpm and the ball milling time to 0.6 h.

[0089] After ball milling, the material was transferred to a tube furnace, and 99.99% pure argon gas was introduced at a flow rate of 0.5 L / min. The temperature was increased to 220°C at a rate of 1.2°C / min for low-temperature annealing for 2.5 hours. After annealing, the material was allowed to cool naturally to room temperature to obtain a high-cycle lithium vanadium manganese iron phosphate electrode material.

[0090] Example 4

[0091] S1 Premixed Slurry Preparation

[0092] The molar ratio of Li:(Fe+Mn+V):PO4:F:P = 1.07:0.58:1:0.045:0.018 was used to select lithium, phosphoric acid, iron, manganese, vanadium, fluorine, and phosphorus dopant. The molar ratio of iron, manganese, and vanadium sources was Fe:Mn:V = 0.68:0.29:0.19. The lithium source was a 1:1 mass mixture of lithium carbonate and lithium hydroxide, both with a purity of 99.8%. The phosphoric acid source was ammonium dihydrogen phosphate with a purity of 99.5%. The iron source was ferrous oxalate with a purity of 99.0%. The manganese source was manganese carbonate with a purity of 99.0%. The vanadium source was vanadium oxalate with a purity of 98.5%. The fluorine source was ammonium fluoride with a purity of 99.0%. The phosphorus dopant was lithium hypophosphite with a purity of 98.0%.

[0093] The composite carbon source is composed of glucose, carbon black, and carboxymethyl cellulose in a mass ratio of 2.8:1:1, and its mass fraction is 9% of the total mass of the raw materials. The nitrogen dopant is a mixture of urea and melamine in a mass ratio of 1:1, both with a purity of 99.0%, and its mass fraction is 1.8% of the total mass of the raw materials.

[0094] All the above raw materials were added to a planetary ball mill using zirconia balls with a diameter of 5 mm as the milling media, at a material-to-ball ratio of 1:12. Dry milling was performed first at 580 rpm for 1.9 hours, with a 5-minute stop every 25 minutes. After dry milling, 99.7% anhydrous ethanol was added to adjust the material-to-liquid ratio to 1:5.8, followed by wet milling at 480 rpm for 2.9 hours, with a 5-minute stop every 25 minutes. The final product was a premixed slurry with uniform particle size, with a particle size D90 of approximately 4.2 μm.

[0095] S2 Primary Precursor Preparation

[0096] The premixed slurry was transferred to a three-necked flask, and a three-layer paddle mechanical stirrer was installed. The stirring speed was set to 480 rpm, and a constant temperature water bath was turned on. The temperature was slowly increased to 98°C for the pre-crystallization reaction, which lasted for 5.8 hours. The slurry state was observed every hour during the reaction. After the reaction, the slurry was filtered using a 0.55 μm ceramic filter membrane. The filter cake was collected and spread evenly in a forced-air drying oven. The drying temperature was set to 89°C, the air velocity to 1.9 m / s, and the drying time to 7.8 hours. The filter cake was manually turned every 1.5 hours during the drying process to obtain a loose and porous primary lithium vanadium manganese iron phosphate precursor.

[0097] Preparation of S3 nucleophase hierarchical structure precursor

[0098] Take an appropriate amount of primary precursor and mix it with deionized water with a conductivity ≤10μS / cm. The mixing ratio is 1:4.8 (g / mL) of primary precursor to deionized water. After stirring evenly, transfer the mixture to a high-pressure hydrothermal reactor made of titanium alloy. Introduce 99.995% pure argon gas into the reactor at a flow rate of 1.2L / min for 38 minutes to purge the air from the reactor. Then seal the reactor. Start the heating program in a stepped heating mode: first, heat to 145℃ at a rate of 2.9℃ / min and hold for 3.8h; then heat to 215℃ at a rate of 1.9℃ / min and hold for 9.5h.

[0099] After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The reaction solution was then transferred to a high-speed centrifuge and centrifuged at 8800 rpm for 19 min. The precipitate was collected. The precipitate was washed four times with deionized water, with an equal mass of deionized water added each time and the mixture stirred thoroughly before centrifugation. The precipitate was then washed once with anhydrous ethanol. The precipitate was transferred to a vacuum drying oven and dried at a vacuum of -0.098 MPa, a drying temperature of 98 °C, and a drying time of 13.5 h to obtain a fluorine-nitrogen-phosphorus ternary doped nucleo-phase hierarchical lithium vanadium manganese iron phosphate precursor with a particle size D50 of approximately 1.7 μm.

[0100] Preparation of S4 coated modified precursor mixture

[0101] Take an appropriate amount of nucleophase fractionation precursor. The composite coating agent is a mixture of nano-alumina, graphene, and carbon nanotubes in a mass ratio of 4.8:1:1, and its mass fraction is 2.8% of the mass of the nucleophase fractionation precursor. The secondary carbon source is a mixture of citric acid and sucrose in a mass ratio of 1:1, both with a purity of 99.5%, and a mass fraction of 4.5% of the mass of the nucleophase fractionation precursor.

[0102] The nucleus-phase fractionation precursor, composite coating agent, and secondary carbon source were added together into a planetary ball mill. The milling media were zirconia balls with a diameter of 4 mm, a material-to-ball ratio of 1:12, a rotation speed of 350 rpm, and a milling time of 1.9 h. After milling, the mixture was transferred to a vacuum drying oven, where a vacuum degree of -0.088 MPa, a diffusion treatment temperature of 118 °C, and a diffusion treatment time of 4.8 h were set. The mixture was manually stirred once every 1 h during the process to obtain the coated and modified precursor mixture.

[0103] Preparation of S5 calcined primary product

[0104] The precursor mixture was transferred to a quartz boat and placed in a tube furnace. A mixture of nitrogen and argon gas, both with a purity of 99.99%, at a volume ratio of 7:3 and a gas flow rate of 0.95 L / min was introduced. The temperature was increased to 395 °C at a heating rate of 7.5 °C / min, and the pre-calcination time was 2.9 h.

[0105] After pre-calcination, while maintaining a constant gas flow rate, the volume ratio of the mixed gas was switched to 1:1, and the temperature was increased to 740℃ at a heating rate of 2.9℃ / min for 7.8 hours. The gas flow rate was monitored in real time during calcination to ensure stability. After calcination, the mixture was allowed to cool naturally to room temperature to obtain the initial calcined product.

[0106] S6 High Cycling Electrode Material Preparation

[0107] Take an appropriate amount of the initial product. The surface passivating agent is ammonium metaborate with a purity of 98.5%, and its mass fraction is 0.45% of the initial product mass. Add the initial product and ammonium metaborate together into a planetary ball mill. The ball milling media are zirconia balls with a diameter of 2 mm. The material-to-ball ratio is 1:9.5. Set the rotation speed to 340 rpm and the ball milling time to 0.95 h.

[0108] After ball milling, the material was transferred to a tube furnace, and 99.99% pure argon gas was introduced at a flow rate of 0.75 L / min. The temperature was increased to 290°C at a rate of 1.9°C / min for low-temperature annealing for 3.8 hours. After annealing, the material was allowed to cool naturally to room temperature to obtain a high-cycle lithium vanadium manganese iron phosphate electrode material.

[0109] Comparative Example 1: Traditional Solid-State Method

[0110] S1 Raw Material Mixing

[0111] The following sources were selected based on a molar ratio of Li:(Fe+Mn+V):PO4 = 1.05:0.5:1: lithium, phosphoric acid, iron, manganese, and vanadium sources, with the molar ratio of iron, manganese, and vanadium sources being Fe:Mn:V = 0.6:0.25:0.15. The lithium source was lithium carbonate with a purity of 99.9%; the phosphoric acid source was ammonium dihydrogen phosphate with a purity of 99.5%; the iron source was ferrous oxalate with a purity of 99.0%; the manganese source was manganese carbonate with a purity of 99.0%; and the vanadium source was vanadium oxyoxalate with a purity of 98.5%.

[0112] The carbon source used was single carbon black, with a mass fraction of 5% of the total raw material mass. All raw materials were added to a planetary ball mill, with zirconia balls of 5 mm diameter as the milling media and a material-to-ball ratio of 1:10. A single dry grinding process was adopted, with a dry grinding speed of 500 rpm and a dry grinding time of 4 hours, during which the mill was stopped for 5 minutes every 30 minutes to obtain a mixed powder with a particle size D90 of approximately 12 μm.

[0113] S2 calcination treatment

[0114] The mixed powder was transferred to a quartz boat and placed in a tube furnace. Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 0.8 L / min, and the temperature was increased to 700℃ at a heating rate of 5℃ / min. The furnace was then calcined at this temperature for 10 hours. The atmosphere was kept stable during the calcination process, and the furnace was allowed to cool naturally to room temperature after the calcination to obtain the calcined product.

[0115] S3 coating treatment

[0116] Take an appropriate amount of calcined product, add single carbon nanotubes as a coating agent, with a mass fraction of 2% of the calcined product mass, and add them together into a planetary ball mill. The ball milling media are zirconia balls with a diameter of 3 mm, a material-to-ball ratio of 1:10, a rotation speed of 350 rpm, and a ball milling time of 1.5 h to obtain the coated modified product.

[0117] S4 Post-processing

[0118] The coated and modified product was placed in a forced-air drying oven at 85°C for 7 hours and then naturally cooled to room temperature to obtain the lithium iron phosphate vanadium manganese phosphate electrode material prepared by the traditional solid-state method.

[0119] Comparative Example 2: Surface passivation and low-temperature annealing

[0120] S1 Premixed Slurry Preparation

[0121] Consistent with Example 1, the raw materials were selected with a molar ratio of Li:(Fe+Mn+V):PO4:F:P = 1.05:0.5:1:0.03:0.01. The types and proportions of composite carbon source and nitrogen dopant were the same, and the dry grinding and wet grinding parameters were the same to obtain premixed slurry with the same particle size.

[0122] S2 Primary Precursor Preparation

[0123] Consistent with Example 1, the stirring rate, pre-crystallization temperature and time, filtration and drying parameters were the same, resulting in primary vanadium manganese iron phosphate precursors in the same state.

[0124] Preparation of S3 nucleophase hierarchical structure precursor

[0125] Consistent with Example 1, the stepped heating parameters, centrifugal washing, and vacuum drying conditions of the hydrothermal reaction were the same, resulting in a fluorine-nitrogen-phosphorus ternary doped nucleophase hierarchical lithium vanadium manganese iron phosphate precursor.

[0126] Preparation of S4 coated modified precursor mixture

[0127] Consistent with Example 1, the composite coating agent, secondary carbon source types and proportions are the same, and the ball milling and diffusion treatment parameters are the same, resulting in a coated and modified precursor mixture.

[0128] Preparation of S5 calcined primary product

[0129] Consistent with Example 1, the atmosphere, heating rate, temperature, and time parameters for pre-calcination and high-temperature calcination were the same, resulting in the initial product after calcination.

[0130] S6 electrode material preparation

[0131] A suitable amount of the initial product was taken and added directly into a planetary ball mill without adding any surface passivating agent. The milling media were zirconia balls with a diameter of 2 mm, a material-to-ball ratio of 1:8, a set rotation speed of 300 rpm, and a milling time of 0.8 h. After milling, the mixture was allowed to cool naturally to room temperature without undergoing low-temperature annealing, resulting in lithium vanadium manganese iron phosphate electrode material.

[0132] The core electrochemical performance of the examples and comparative examples is compared in the table below:

[0133] Table 1

[0134]

[0135] The following table compares the interface and structural stability of the examples and comparative examples:

[0136] Table 2

[0137]

[0138] The performance data from both tables show that the high-cycle vanadium manganese iron lithium phosphate electrode materials prepared in Examples 1-4 exhibit excellent core electrochemical performance and interfacial structural stability. Not only do they generally achieve an initial discharge specific capacity exceeding 163 mAh / g and a capacity retention rate exceeding 90% after 1000 cycles, but their electronic conductivity and lithium-ion diffusion rate are significantly better than the comparative examples. Furthermore, they effectively suppress manganese ion dissolution, reduce interfacial charge transfer impedance, and maintain grain integrity and coating stability after cycling. In contrast, Comparative Example 1 suffers from a simple process, and Comparative Example 2 lacks the crucial steps of surface passivation and low-temperature annealing, resulting in significant shortcomings in various performance aspects. This further confirms that the dry-wet graded ball milling, step-by-step hydrothermal crystallization, fluorine-nitrogen-phosphorus ternary doping, composite coating, and passivation annealing synergistic process employed in this invention can comprehensively improve the overall performance of electrode materials and solve the core bottlenecks of traditional preparation processes.

[0139] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for preparing high-cycle lithium iron phosphate vanadium manganese phosphate electrode material, characterized in that, Includes the following steps: S1. Weigh the lithium source, phosphoric acid source, iron source, manganese source, vanadium source, fluorine source, and phosphorus dopant. Mix the above raw materials with the composite carbon source and nitrogen dopant. First, dry grind them in a planetary ball mill, then add anhydrous ethanol to adjust the material-liquid ratio and wet grind them. The ball milling medium is zirconium oxide balls to obtain a premixed slurry with uniform particle size. In S1, the molar ratio of lithium source, phosphoric acid source, iron source, manganese source, vanadium source, fluorine source, and phosphorus dopant is Li:(Fe+Mn+V):PO4:F:P=1.02-1.08:0.4-0.6:1:0.01-0.05:0.005-0.02, where the molar ratio of iron source, manganese source, and vanadium source is Fe:Mn:V=0.5-0.7:0.2-0.3:0.1-0.2; the dry grinding speed is 400-600 rpm, the dry grinding time is 1-2 h; the wet grinding material-liquid ratio is 1:4-1:6, the wet grinding speed is 300-500 rpm, the wet grinding time is 2-3 h; the ball milling material-ball ratio is 1:8-1:12; the mass fraction of composite carbon source is 5%-10%; and the mass fraction of nitrogen dopant is 0.5%-2%. S2. Transfer the premixed slurry to a three-necked flask and stir. Heat the mixture to carry out a water bath precrystallization reaction. After the reaction is complete, filter the mixture and dry the filter cake by blowing air to obtain the primary vanadium manganese iron lithium phosphate precursor. S3. After mixing the primary precursor with deionized water, transfer it to a hydrothermal reactor. After purging the air in the reactor with argon gas, seal it and use a step-by-step heating mode. After the reaction is completed, allow it to cool naturally to room temperature. After centrifugation and washing, vacuum dry to obtain a fluorine-nitrogen-phosphorus ternary doped nucleophase hierarchical lithium phosphate vanadium manganese iron precursor. The specific parameters for the stepped heating in S3 are as follows: first, heat to 120-150℃ at a rate of 2-3℃ / min, hold for 2-4 hours, then heat to 180-220℃ at a rate of 1-2℃ / min, hold for 6-10 hours; the vacuum drying temperature is 80-100℃, the vacuum drying time is 10-14 hours, and the vacuum degree is -0.08 to -0.1 MPa. S4. Mix the nucleus phase fractionation precursor with the composite coating agent and the secondary carbon source, place it in a planetary ball mill for ball milling, and after ball milling, transfer it to a vacuum drying oven for diffusion treatment of doped elements under vacuum conditions to obtain the coated and modified precursor mixture. In S4, the mass fraction of the composite coating agent is 1%-3%, the mass fraction of the secondary carbon source is 2%-5%, the ball milling speed is 350 rpm, the ball milling time is 1-2 h, the diffusion treatment temperature is 100-120℃, and the diffusion treatment time is 3-5 h. S5. Place the precursor mixture in a tube furnace and pre-calcine it at 350-400℃ in an atmosphere with a nitrogen-argon volume ratio of 7:

3. Then switch to an atmosphere with a nitrogen-argon volume ratio of 1:1 and calcine it at a heating rate of 2-3℃ / min to 650-750℃ to obtain the calcined initial product. In S5, the pre-calcination heating rate is 5-8℃ / min, the pre-calcination time is 2-3h, the high-temperature calcination heating rate is 2-3℃ / min, the high-temperature calcination time is 6-8h, and the gas flow rate inside the tube furnace is 0.5-1L / min. S6. After mixing the initial product with the surface passivating agent, the mixture is ball-milled again. Then, it is placed in a tube furnace and heated to 200-300℃ in a pure argon atmosphere for low-temperature annealing. After annealing, it is naturally cooled to room temperature to obtain high-cycle lithium vanadium manganese iron phosphate electrode material. The lithium source is one or more of lithium carbonate, lithium hydroxide, and lithium nitrate; the phosphoric acid source is one or more of ammonium dihydrogen phosphate, phosphoric acid, and diammonium hydrogen phosphate; the iron source is one or more of ferrous oxalate, ferrous sulfate, and ferrous chloride; the manganese source is one or more of manganese carbonate, manganese oxalate, and manganese acetate; the vanadium source is one or more of vanadium oxyoxalate, ammonium metavanadate, and vanadium oxysulfate; the fluorine source is one or more of ammonium fluoride, lithium fluoride, and sodium fluoride; and the phosphorus dopant is one or more of ammonium phosphite and lithium hypophosphite. The composite carbon source is a mixture of glucose, carbon black, and carboxymethyl cellulose in a mass ratio of 2:1:1 to 3:1:1; the nitrogen dopant is one or more of urea, melamine, and dicyandiamide; the composite coating agent is a mixture of nano-alumina, graphene, and carbon nanotubes in a mass ratio of 3:1:1 to 5:1:1; the secondary carbon source is one or more of citric acid, sucrose, and ascorbic acid; and the surface passivating agent is one or more of lithium borate and ammonium metaborate.

2. The preparation process of the high-cycle vanadium manganese iron lithium phosphate electrode material according to claim 1, characterized in that, The molar ratio of lithium source, phosphoric acid source, iron source, manganese source, vanadium source, fluorine source, and phosphorus dopant in S1 is Li:(Fe+Mn+V):PO4:F:P=1.05:0.5:1:0.03:0.01, and the molar ratio of iron source, manganese source, and vanadium source is Fe:Mn:V=0.6:0.25:0.

15.

3. The preparation process of the high-cycle vanadium manganese iron lithium phosphate electrode material according to claim 1, characterized in that, In S2, the mechanical stirring rate is 300-500 rpm, the water bath pre-crystallization temperature is 80-100℃, the pre-crystallization reaction time is 4-6 h, the forced-air drying temperature is 80-90℃, and the forced-air drying time is 6-8 h.

4. The preparation process of the high-cycle vanadium manganese iron lithium phosphate electrode material according to claim 1, characterized in that, In S6, the surface passivating agent has a mass fraction of 0.1%-0.5%, the ball milling time is 0.5-1h, the annealing heating rate is 1-2℃ / min, and the annealing time is 2-4h.

Images