High-compacted lithium iron phosphate material regenerated from waste battery phosphorus iron slag and preparation method thereof
Patent Information
- Application Number
- CN202610916368.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-24
- Publication Date
- 2026-09-22
AI Technical Summary
针对磷铁渣再生材料中缺陷修复、均匀碳层构建以及颗粒级配协同优化等方面，尚缺乏系统且有效的技术方案
（1）以废旧磷酸铁锂电池回收过程中产生的磷铁渣为原料，通过补锂、补铁及固相修复再生，实现了资源高值化利用，降低了磷酸铁锂正极材料的生产成本。
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Figure CN122789360A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of resource recycling and electrode material preparation technology of waste lithium-ion batteries, specifically involving high-pressure lithium iron phosphate material and its preparation method for the regeneration of waste battery phosphorus iron slag. Background Technology
[0002] Lithium iron phosphate (LFP) batteries possess advantages such as high safety, long cycle life, low cost, and environmental friendliness, and have been widely used in new energy vehicles and energy storage. As a large number of LFP power batteries gradually enter their retirement period, the recycling and high-value reuse of spent LFP batteries has become an important direction for the green development of the new energy industry. Existing wet recycling processes can typically achieve efficient leaching and recovery of lithium elements, but the leaching process generates solid residues containing iron and phosphorus, namely iron-phosphorus slag. This type of iron-phosphorus slag still retains the iron and phosphorus framework required for the regeneration and synthesis of lithium iron phosphate, and has high reuse value. However, directly using iron-phosphorus slag to regenerate lithium iron phosphate cathode materials usually results in problems such as uneven particle size distribution, low compaction density, and poor electrochemical performance.
[0003] Currently, high-density lithium iron phosphate (LFP) cathode materials are typically prepared using high-purity raw materials or precursors. Utilizing the iron phosphate slag generated during the recycling of spent LFP batteries to prepare high-density cathode materials for high-value reuse is of great significance. However, systematic and effective technical solutions are still lacking regarding defect repair, uniform carbon layer construction, and synergistic optimization of particle size distribution in the recycled iron phosphate slag materials. Therefore, using iron phosphate slag generated during the recycling of spent LFP batteries as raw material to prepare recycled LFP cathode materials with high compaction density and excellent electrochemical performance has significant engineering application value and industrialization prospects. Summary of the Invention
[0004] To address the aforementioned problems in existing technologies, this invention provides a low-cost and simple method for preparing high-compact-density regenerated lithium iron phosphate cathode materials from the phosphorus-iron slag generated during the recycling of spent lithium iron phosphate batteries. This method optimizes the carbon layer structure on the material surface and constructs a multi-dimensional conductive network by employing multiple carbon sources for synergistic coating. Simultaneously, it utilizes different processes to prepare lithium iron phosphate materials with different particle size characteristics and performs particle gradation, thereby significantly improving the compaction density and electrochemical performance of the material.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing high-pressure lithium iron phosphate material from recycled waste battery slag, comprising the following steps: Step 1: Treat the ferrophosphate slag with an acid of a certain concentration for a certain period of time, then separate the solid and liquid, and calcine the solid in an air atmosphere to obtain purified ferrophosphate slag. Step 2: The purified phosphorus iron slag, lithium source, iron / phosphorus source and mixed carbon source are mixed in a certain proportion and added to a certain amount of solvent. The mixture is then ground. After the ground material is dried in an oven, it is sintered under an argon-hydrogen atmosphere to obtain the first sintered material A. Step 3: Take purified phosphorus iron slag, lithium source, iron / phosphorus source and mixed carbon source, mix them in a certain proportion and add them to the solvent, grind them, spray dry the ground material to obtain the precursor; then sinter the obtained precursor under an argon-hydrogen atmosphere to obtain the second sintering material B; Step 4: Mix the first sintered material A and the second sintered material B in a certain mass ratio to obtain high-density lithium iron phosphate cathode material.
[0006] Preferably, in step one, the acid used for acid leaching of the phosphorus iron slag to remove impurities is one or more of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid, and oxalic acid, with an acid concentration of 0.05-2 mol / L, a reaction temperature of 20-100 ℃, a reaction time of 10-180 min, and a solid-liquid ratio of 10-300 g / L; the conditions for air calcination to remove graphite are: heating from room temperature to 300-800 ℃ at a heating rate of 1-10 ℃ / min, holding at that temperature for 1-15 h, and then cooling back to room temperature at a cooling rate of 1-20 ℃ / min.
[0007] Preferably, in steps two and three, the lithium source is one or more of lithium carbonate, lithium phosphate, lithium dihydrogen phosphate, lithium dihydrogen phosphate, and lithium hydroxide; the iron / phosphorus source is one or more of ferrous sulfate, ferric sulfate, ferric oxide, ferric tetroxide, ferrous oxalate, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, pyrophosphate, and phosphorus pentoxide; the carbon source is one or more of glucose, sucrose, polyvinyl alcohol, polyethylene glycol, carbon nanotubes, and graphene; and the solvent is one or more of water, ethanol, methanol, and acetone.
[0008] Preferably, in steps two and three, with a molar amount of purified phosphorus-iron slag of 100 parts, the total molar amount of iron / phosphorus source is 0.1-10 parts, and the total molar amount of lithium source is 100-110 parts.
[0009] Preferably, in steps two and three, the mass ratio of glucose, sucrose, polyvinyl alcohol, polyethylene glycol, carbon nanotubes, and graphene in the mixed carbon source is (0-1): (0-1): (0-1): (0-1): (0-0.3): (0-0.3), and the total mass of the added carbon source is 5-20% of the total mass of phosphorus-iron slag, lithium source, and iron / phosphorus source.
[0010] Preferably, in steps two and three, grinding is carried out by ball milling or sand milling at a speed of 300-3000 r / min. Based on 100 parts of the above mixture, the mass of solvent added is 50-500 parts, the ball-to-material mass ratio is 1-15:1, and the time is 1-15 h. In step two, the oven drying temperature is 60-100 ℃, and the time is 4-12 h. In step three, the inlet temperature of spray drying is 110-320 ℃, and the outlet temperature is 60-160 ℃.
[0011] Preferably, in steps two and three, the sintering conditions are as follows: heating from room temperature to 200-500 ℃ at a heating rate of 1-10 ℃ / min and holding for 1-8 h; then heating to 650-850 ℃ at a heating rate of 1-10 ℃ / min and holding for 3-15 h; and finally cooling to room temperature at a cooling rate of 1-20 ℃ / min.
[0012] Preferably, in step four, the mass ratio of the first sintering material A to the second sintering material B is (1-5): (9-5).
[0013] Secondly, the present invention provides a high-pressure lithium iron phosphate material for the regeneration of waste battery phosphorus slag, wherein the cathode material is prepared by the method described in the first aspect.
[0014] Preferably, it is used in the positive electrode of a lithium-ion battery.
[0015] The beneficial effects of this invention over the prior art are as follows: (1) Using phosphorus iron slag generated during the recycling of waste lithium iron phosphate batteries as raw material, high-value utilization of resources is achieved through lithium replenishment, iron replenishment and solid phase repair and regeneration, thereby reducing the production cost of lithium iron phosphate cathode materials.
[0016] (2) By using mixed carbon sources for synergistic coating, the carbon layer structure on the material surface can be optimized, a multidimensional conductive network can be constructed, electron transport can be promoted and lithium ion diffusion kinetics can be improved, thereby improving the electrochemical performance of the material.
[0017] (3) By preparing sintered materials with different particle sizes through different processes and grading them, small particles can fill the pores between large particles, thereby effectively improving the compaction density and energy density of the material. Attached Figure Description
[0018] The accompanying drawings are only used to illustrate the technical solutions of the present invention and do not constitute a limitation on the scope of protection of the present invention.
[0019] Figure 1 This is a SEM image of the lithium iron phosphate cathode material prepared in Example 1 of this invention; Figure 2This is the XRD pattern of the lithium iron phosphate cathode material prepared in Example 1 of this invention; Figure 3 These are charge-discharge curves at 0.1 C for the coin cells assembled from the materials prepared in Examples 1-4 and Comparative Examples 1-2 of this invention. Figure 4 These are the 1C cycle performance diagrams of the coin cells assembled from the materials prepared in Examples 1-4 and Comparative Examples 1-2 of this invention. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0021] Example 1 A certain mass of ferrophosphate slag was dispersed in 0.2 mol / L sulfuric acid at a solid-liquid ratio of 30 g / L and acid-leached at 50 °C for 30 min, followed by solid-liquid separation. The obtained solid was heated in air at a heating rate of 5 °C / min from room temperature to 600 °C and held at that temperature for 6 h, then cooled to room temperature at a cooling rate of 10 °C / min to obtain purified ferrophosphate slag. The purified ferrophosphate slag, lithium carbonate, and ferric sulfate were mixed, and glucose, polyethylene glycol, and carbon nanotubes were added at 15% of the total mass of the mixture, while water was added at 115% of the total mass of the mixture. The mixture was then ball-milled at a ball-to-material mass ratio of 5:1 at 400 r / min for 6 h, and the slurry was dried in an oven at 80 °C for 6 h. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 350 ℃ at a heating rate of 5 ℃ / min, held for 4 h, then heated to 700 ℃ at a heating rate of 5 ℃ / min, held for 10 h, and then cooled to room temperature at a cooling rate of 10 ℃ / min to obtain the first calcined material A.
[0022] Purified iron phosphate slag, lithium carbonate, and ferric sulfate were mixed. Glucose, polyethylene glycol, and carbon nanotubes were added at 15% of the total mass of the mixture, and water was added at 115% of the total mass of the mixture. The mixture was then ball-milled at a ball-to-material mass ratio of 5:1 at 400 r / min for 6 h. The slurry was then spray-dried at an inlet temperature of 140 ℃ and an outlet temperature of 70 ℃. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 350 ℃ at a heating rate of 5 ℃ / min, held for 4 h, then heated to 700 ℃ at a heating rate of 5 ℃ / min, held for 10 h, and then cooled to room temperature at a cooling rate of 10 ℃ / min to obtain the second calcined material B. The first calcined material A and the second calcined material B were mixed at a mass ratio of 3:7 to obtain high-density lithium iron phosphate coated with a mixed carbon source.
[0023] Example 2 A certain mass of ferrophosphate slag was dispersed in 0.3 mol / L hydrochloric acid at a solid-liquid ratio of 45 g / L and acid-leached at 55 °C for 45 min, followed by solid-liquid separation. The obtained solid was heated in air from room temperature to 550 °C at a heating rate of 3 °C / min and held at that temperature for 5 h, then cooled to room temperature at a cooling rate of 12 °C / min to obtain purified ferrophosphate slag. The purified ferrophosphate slag, lithium dihydrogen phosphate, and ferrous oxalate were mixed, and glucose, polyethylene glycol, and carbon nanotubes were added at 12% of the total mass of the mixture, and water was added at 130% of the total mass of the mixture. The mixture was then ball-milled at a ball-to-material mass ratio of 10:1 at 450 r / min for 8 h, and the slurry was dried in an oven at 80 °C for 6 h. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 400 ℃ at a heating rate of 3 ℃ / min, held for 5 h, then heated to 650 ℃ at a heating rate of 3 ℃ / min, held for 8 h, and then cooled to room temperature at a cooling rate of 8 ℃ / min to obtain the first calcined material A.
[0024] Purified iron phosphate slag, lithium dihydrogen phosphate, and ferrous oxalate were mixed. Glucose, polyethylene glycol, and carbon nanotubes were added at 12% of the total mass of the mixture, and water was added at 130% of the total mass of the mixture. The mixture was then ball-milled at a ball-to-material mass ratio of 10:1 at 450 r / min for 8 h. The slurry was then spray-dried at an inlet temperature of 150 ℃ and an outlet temperature of 80 ℃. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 400 ℃ at a heating rate of 3 ℃ / min, held for 5 h, then heated to 650 ℃ at a heating rate of 3 ℃ / min, held for 8 h, and then cooled to room temperature at a cooling rate of 8 ℃ / min to obtain the second calcined material B. The first calcined material A and the second calcined material B were mixed at a mass ratio of 2:8 to obtain high-density lithium iron phosphate coated with a mixed carbon source.
[0025] Example 3 A certain mass of ferrophosphate slag was dispersed in 0.4 mol / L phosphoric acid at a solid-liquid ratio of 50 g / L. The mixture was then acid-leached at 60 °C for 60 min, followed by solid-liquid separation. The resulting solid was heated in air at a rate of 7 °C / min from room temperature to 575 °C, held at that temperature for 4 h, and then cooled to room temperature at a rate of 15 °C / min to obtain purified ferrophosphate slag. The purified ferrophosphate slag, lithium phosphate, and ferric oxide were mixed. Glucose, polyethylene glycol, and carbon nanotubes were added at 17% of the total mass of the mixture, and water was added at 145% of the total mass of the mixture. The mixture was then ball-milled at a ball-to-material mass ratio of 15:1 at 500 r / min for 9 h. The slurry was then dried in an oven at 80 °C for 6 h. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 450 ℃ at a heating rate of 6 ℃ / min, held for 6 h, then heated to 750 ℃ at a heating rate of 6 ℃ / min, held for 9 h, and then cooled to room temperature at a cooling rate of 12 ℃ / min to obtain the first calcined material A.
[0026] Purified iron phosphate slag, lithium phosphate, and ferric oxide were mixed. Glucose, polyethylene glycol, and carbon nanotubes were added at 17% of the mixture's mass, and water was added at 145% of the total mass. The mixture was then ball-milled at a mass ratio of 15:1 at 500 r / min for 9 h. The slurry was then spray-dried at an inlet temperature of 170 ℃ and an outlet temperature of 90 ℃. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 450 ℃ at a heating rate of 6 ℃ / min, held for 6 h, then heated to 750 ℃ at a heating rate of 6 ℃ / min, held for 9 h, and then cooled to room temperature at a cooling rate of 12 ℃ / min to obtain the second calcined material B. The first calcined material A and the second calcined material B were mixed at a mass ratio of 4:6 to obtain high-density lithium iron phosphate coated with a mixed carbon source.
[0027] Example 4 A certain mass of ferrophosphate slag was dispersed in 0.5 mol / L phosphoric acid at a solid-liquid ratio of 100 g / L. The mixture was then acid-leached at 80 °C for 80 min, followed by solid-liquid separation. The resulting solid was heated in air at a rate of 10 °C / min from room temperature to 500 °C, held at that temperature for 8 h, and then cooled to room temperature at a rate of 20 °C / min to obtain purified ferrophosphate slag. The purified ferrophosphate slag, lithium phosphate, and iron oxide were mixed. Glucose, polyethylene glycol, and carbon nanotubes were added at 20% of the total mass of the mixture, and water was added at 150% of the total mass of the mixture. The mixture was then ball-milled at a ball-to-material mass ratio of 12:1 at 600 r / min for 10 h. The slurry was then dried in an oven at 80 °C for 6 h. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 500 °C at a heating rate of 10 °C / min, held for 7 h, then heated to 800 °C at a heating rate of 7 °C / min, held for 8 h, and then cooled to room temperature at a cooling rate of 15 °C / min to obtain the first calcined material A.
[0028] Purified iron phosphate slag, lithium phosphate, and iron oxide were mixed. Glucose, polyethylene glycol, and carbon nanotubes were added at 20% of the mixture's mass, and water was added at 150% of the total mass. The mixture was then ball-milled at a ball-to-material mass ratio of 15:1 at 600 r / min for 10 h. The slurry was then spray-dried at an inlet temperature of 180 ℃ and an outlet temperature of 100 ℃. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 500 ℃ at a heating rate of 10 ℃ / min, held for 7 h, then heated to 800 ℃ at a heating rate of 7 ℃ / min, held for 8 h, and finally cooled to room temperature at a cooling rate of 15 ℃ / min to obtain the second calcined material B. The first calcined material A and the second calcined material B were mixed at a mass ratio of 5:5 to obtain high-density lithium iron phosphate coated with a mixed carbon source.
[0029] Comparative Example 1 A certain mass of ferrophosphate slag was dispersed in 0.2 mol / L sulfuric acid at a solid-liquid ratio of 30 g / L and acid-leached at 50 °C for 30 min, followed by solid-liquid separation. The obtained solid was heated in air at a heating rate of 5 °C / min from room temperature to 600 °C and held at that temperature for 6 h, then cooled to room temperature at a cooling rate of 10 °C / min to obtain purified ferrophosphate slag. The purified ferrophosphate slag, lithium carbonate, and ferric sulfate were mixed, and glucose was added at 15% of the total mass of the mixture, and water was added at 115% of the total mass of the mixture. The mixture was then ball-milled at a ball-to-material mass ratio of 5:1 at 400 r / min for 6 h. The slurry was then dried in an oven at 80 °C for 6 h. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 350 °C at a heating rate of 5 °C / min, held for 4 h, then heated to 700 °C at a heating rate of 5 °C / min, held for 10 h, and then cooled to room temperature at a cooling rate of 10 °C / min to obtain lithium iron phosphate cathode material.
[0030] Comparative Example 2 A certain mass of ferrophosphate slag was dispersed in 0.2 mol / L sulfuric acid at a solid-liquid ratio of 30 g / L and acid-leached at 50 °C for 30 min, followed by solid-liquid separation. The obtained solid was heated in air at a heating rate of 5 °C / min from room temperature to 600 °C and held at that temperature for 6 h, then cooled to room temperature at a cooling rate of 10 °C / min to obtain purified ferrophosphate slag. The purified ferrophosphate slag, lithium carbonate, and ferric sulfate were mixed, and glucose was added at 15% of the total mass of the mixture, and water was added at 115% of the total mass of the mixture. The mixture was then ball-milled at a ball-to-material mass ratio of 5:1 at 400 r / min for 6 h. The slurry was then spray-dried at an inlet temperature of 140 °C and an outlet temperature of 70 °C. The dried material was placed in an argon-hydrogen atmosphere furnace and heated to 350 °C at a heating rate of 5 °C / min, held for 4 h, then heated to 700 °C at a heating rate of 5 °C / min, held for 10 h, and then cooled to room temperature at a cooling rate of 10 °C / min to obtain lithium iron phosphate cathode material.
[0031] Compaction density comparison: The compaction density of the cathode materials prepared by the examples and comparative examples was tested, and the results are shown in Table 1.
[0032] Table 1
[0033] As shown in Table 1, the electrode compaction density of the lithium iron phosphate materials prepared in Examples 1-4 is higher than that of the lithium iron phosphate materials prepared in Comparative Examples 1-2, indicating superior processing performance. This application obtained lithium iron phosphate materials with high compaction density through mixed carbon source coating and particle gradation.
[0034] SEM images of the graded high-density lithium iron phosphate cathode material prepared in Example 1 are shown below. Figure 1 As shown, the sample contains particles of different sizes. This particle size distribution forms a gradation of large and small particles, which increases the compaction density of the material. The spray-dried sample exhibits a regular spherical morphology. This morphology is conducive to the rearrangement and slippage of particles during the electrode rolling process, thereby increasing the compaction density of the electrode.
[0035] The XRD pattern of the lithium iron phosphate cathode material prepared in Example 1 is shown below. Figure 2 As shown, the characteristic diffraction peaks of the sample match the standard card of olivine structure LiFePO4, indicating that a well-crystallized lithium iron phosphate material was successfully synthesized.
[0036] The following describes the preparation process of coin cells based on the lithium iron phosphate cathode material prepared in the aforementioned embodiments, and compares the electrochemical performance of coin cells prepared based on different lithium iron phosphate cathode materials.
[0037] Active material, PVDF, and conductive carbon black were mixed in a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone (NMP) to form a slurry. The slurry was then stirred on a stirring table for 8 hours to ensure uniform mixing. The slurry was then uniformly coated onto aluminum foil and dried in a vacuum oven at 80 °C for 12 hours. The electrode sheet was then removed, compacted on a tablet press, and finally cut into 14 mm diameter electrode discs using a slicing machine. Using the electrode sheet prepared based on lithium iron phosphate cathode material as the positive electrode, lithium foil as the negative electrode, a 1.0 M LiPF6 solution dissolved in EC: EMC: DMC = 1:1:1 (v:v:v) as the electrolyte, and a Celgard 2500 polypropylene organic microporous membrane as the separator, a coin cell was assembled in a glove box filled with high-purity argon.
[0038] After assembling the button cell, the battery was charged and discharged using a NEWARE BTS (range: 0-5 V, 0-50 mA) charge and discharge tester at rates of 0.1 C and 1 C.
[0039] A comparison of the charge-discharge curves at 0.1 C rate of lithium-ion batteries (i.e., the aforementioned coin cells) assembled with lithium iron phosphate cathode materials prepared in Examples 1-4 and those prepared in Comparative Examples 1-2. Figure 3 As shown. From Figure 3 As can be seen from this, the battery exhibits the typical charge-discharge plateau of lithium iron phosphate materials, corresponding to Fe 2+ / Fe 3+Redox reactions and the lithium-ion insertion / extraction process. The battery assembled from the materials prepared in Example 1 has a 0.1 C discharge capacity of 162.59 mAh / g and a 1C discharge capacity of 140.83 mAh / g. Figure 4 The comparison of the 1C charge-discharge cycle curves of Examples 1-4 and Comparative Examples 1-2 shows that the lithium-ion battery prepared in Example 1 has the best electrochemical performance.
[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the scope of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing high-pressure lithium iron phosphate material from recycled waste battery slag, characterized in that, Includes the following steps: Step 1: Treat the ferrophosphate slag with an acid of a certain concentration for a certain period of time, then separate the solid and liquid, and calcine the solid in an air atmosphere to obtain purified ferrophosphate slag. Step 2: The purified phosphorus iron slag, lithium source, iron / phosphorus source and mixed carbon source are mixed in a certain proportion and added to a certain amount of solvent. The mixture is then ground. After the ground material is dried in an oven, it is sintered under an argon-hydrogen atmosphere to obtain the first sintered material A. Step 3: Take purified phosphorus iron slag, lithium source, iron / phosphorus source and mixed carbon source, mix them in a certain proportion and add them to the solvent, grind them, spray dry the ground material to obtain the precursor; then sinter the obtained precursor under an argon-hydrogen atmosphere to obtain the second sintering material B; Step 4: Mix the first sintered material A and the second sintered material B in a certain mass ratio to obtain high-density lithium iron phosphate cathode material.
2. The method as described in claim 1, characterized in that, In step one, the acid used for acid leaching of the phosphorus iron slag to remove impurities is one or more of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid, and oxalic acid, with an acid concentration of 0.05-2 mol / L, a reaction temperature of 20-100℃, a reaction time of 10-180 min, and a solid-liquid ratio of 10-300 g / L. The conditions for air calcination to remove graphite are as follows: heating from room temperature to 300-800℃ at a heating rate of 1-10℃ / min, holding at that temperature for 1-15 h, and then cooling back to room temperature at a cooling rate of 1-20℃ / min.
3. The preparation method according to claim 1, characterized in that, In steps two and three, the lithium source is one or more of lithium carbonate, lithium phosphate, lithium dihydrogen phosphate, lithium dihydrogen phosphate, and lithium hydroxide; the iron / phosphorus source is one or more of ferrous sulfate, ferric sulfate, ferric oxide, ferric tetroxide, ferrous oxalate, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, pyrophosphate, and phosphorus pentoxide; the carbon source is one or more of glucose, sucrose, polyvinyl alcohol, polyethylene glycol, carbon nanotubes, and graphene; and the solvent is one or more of water, ethanol, methanol, and acetone.
4. The method as described in claim 1, characterized in that, In steps two and three, with 100 parts of purified phosphorus-iron slag, the total molar amount of iron / phosphorus source is 0.1-10 parts, and the total molar amount of lithium source is 100-110 parts.
5. The method as described in claim 1, characterized in that, In steps two and three, the mass ratio of glucose, sucrose, polyvinyl alcohol, polyethylene glycol, carbon nanotubes, and graphene in the mixed carbon source is (0-1): (0-1): (0-1): (0-1): (0-0.3): (0-0.3), and the total mass of the added carbon source is 5-20% of the total mass of phosphorus iron slag, lithium source, and iron / phosphorus source.
6. The preparation method according to claim 1, characterized in that, In steps two and three, grinding is carried out using ball milling or sand milling at a speed of 300-3000 r / min. Based on 100 parts of the above mixture, the mass of solvent added is 50-500 parts, the ball-to-material mass ratio is 1-15:1, and the time is 1-15 h. In step two, the oven drying temperature is 60-100 ℃, and the time is 4-12 h. In step three, the inlet temperature of the spray drying process is 110-320 ℃, and the outlet temperature is 60-160 ℃.
7. The preparation method according to claim 1, characterized in that, In steps two and three, the sintering conditions are as follows: heat from room temperature to 200-500 ℃ at a heating rate of 1-10 ℃ / min and hold for 1-8 h; then heat to 650-850 ℃ at a heating rate of 1-10 ℃ / min and hold for 3-15 h; finally cool to room temperature at a cooling rate of 1-20 ℃ / min.
8. The preparation method according to claim 1, characterized in that, In step four, the mass ratio of the first calcined material A to the second calcined material B is (1-5): (9-5).
9. A high-pressure lithium iron phosphate material recycled from waste battery phosphorus slag, characterized in that, The cathode material is prepared by the method described in any one of claims 1-8.
10. The application of the high-pressure lithium iron phosphate material as described in claim 9 in the cathode of a lithium-ion battery.