Preparation method of ferrous lithium phosphate material

Abstract

The present invention discloses a preparation method for a lithium iron phosphate material. The preparation method comprises the following steps: (1) mixing a zinc source, a copper source and a comple

Description

Tr^ij \rir A t iriiri n ri 1 1* Jr IILJLM The present invention belongs to the technical field of lithium-ion battery materials, in particular 5 to a preparation method of a ferrous lithium phosphate material. BACKGROUND In the latest ten years, the technology of new energy industry supported by lithium-ion batteries has developed rapidly and achieved great commercial success. Among various lithium-ion battery 10 technologies, ferrous lithium phosphate (LiFePO4, LFP) battery plays a key role in electric energy storage and electric transportation because of its excellent safety performance, long cycle stability and economy. The ferrous lithium phosphate material accounts for more than 40% of the cost of the ferrous lithium phosphate battery, which plays an important role. It is undeniable that the ferrous lithium phosphate material is one of the core materials of lithium-ion batteries at present. In 2021, the output and installed capacity of the ferrous lithium phosphate batteries in China reached more than 50% in the middle of the year. It is expected that from 2022 to 2023, the ferrous lithium phosphate batteries for passenger cars are expected to account for more than half of the battery types for passenger cars. In 2024, the global shipment of the ferrous lithium phosphate batteries will exceed 550 GWh, and the demand for ferrous lithium phosphate materials 20 can break through 120 wt, reaching an average annual growth rate of more than 60%. In order to meet the current and future consumption demand of the ferrous lithium phosphate materials and solve the contradiction between upstream and downstream supply and demand of the ferrous lithium phosphate batteries, the current main methods are as follows: on the one hand, through the new strategy of efficient recycling of waste ferrous lithium phosphate batteries and obtaining excellent phosphoric 25 acid and lithium resources, the purposes of low pollution to the environment and high returns on resources are achieved; on the other hand, we should give full play to the abundant phosphorus and lithium resources in China and other parts of the world, expand from the source of the required material resources and improve production. Therefore, it is particularly important to research and develop phosphorus and lithium resources, especially to study and synthesize ferrous lithium 30 phosphate precursors and ferrous lithium phosphate materials based on China's rich phosphorus resources. 20 03 25 The existing preparation methods of the ferrous lithium phosphate materials are mostly dry mixing process. Although this process is simple, the prepared ferrous lithium phosphate materials have poor electrochemical performance and cannot meet the increasingly high quality requirements for electrode materials in the market. 5 SUMMARY The present invention aims to solve at least one of the technical problems existing in the existing technology. To this end, the present invention provides a preparation method of a ferrous lithium phosphate material. The ferrous lithium phosphate material prepared by this method has good 10 electrochemical performance and can meet the increasingly high quality requirements for electrode materials in the market. The above technical object of the present invention is realized through the following technical solution: a preparation method of a ferrous lithium phosphate material, including the following steps: (1) mixing the zinc source, copper source and complexing agent solution, then mixing with iron source and phosphoric acid source, evaporating and dehydrating to obtain a jelly, and then primary sintering the jelly under a protective atmosphere to obtain a solid-phase material; and (2) mixing the solidphase material prepared in step (1) with a lithium source, grinding and secondary sintering under a protective atmosphere to obtain the ferrous lithium phosphate material; 20 wherein the complexing agent solution is obtained by mixing a citric acid solution and acetyl acetone, the concentration of the citric acid in the citric acid solution is 1 to 20 w / w%, and the acetylacetone accounts for 1 to 12v / v% of the citric acid solution; wherein the zinc source is at least one of zinc oxide, zinc hydroxide, zinc chloride or zinc sulfate; wherein the copper source is at least one of copper oxide, copper hydroxide, copper chloride or 25 copper sulfate; wherein the iron source is at least one of ferrous chloride, ferrous sulfate or ferrous hydroxide; wherein the phosphoric acid source is at least one of phosphoric acid, ammonium phosphate, potassium phosphate, lithium phosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate or potassium dihydrogen phosphate; 30 wherein the lithium source is at least one of lithium hydroxide, lithium carbonate, lithium nitrate or lithium chloride. Preferably, the mass of the zinc source accounts for 0.1 to 5 w / w% of the citric acid solution, 20 03 25 and the mass of the copper source accounts for 0.1 to 5 w / w% of the citric acid solution. Preferably, the molar ratio of the phosphoric acid, the iron and the lithium in the phosphoric acid source, iron source and lithium source is (1.0-1.2): (1.0-1.05): (1.0-1.01). Preferably, the sintering temperature of the primary sintering and the secondary sintering is 600 5 to 950°C, and the sintering time is 6 to 15 hours. Preferably, the particle size of the material after grinding in step (2) is less than 80 pm. Preferably, the protective atmosphere described in step 1 is at least one of Ne, Ar, Kr or He. Preferably, the phosphoric acid source is phosphoric acid, which is prepared from phosphorus concentrate. 10 Further preferably, the preparation method of the phosphoric acid includes the following steps: Al: preparation of crude phosphoric acid: adding a first acid to the phosphorus concentrate for activation reaction, then adding a second acid, leaching and press filtering to obtain the filtrate, and then adding water to adjust the concentration to obtain the crude phosphoric acid. A2: preparation of phosphoric acid: adding an extractant into the crude phosphoric acid, mixing and extracting, oscillation separating to obtain a primary extraction solution and an impurity solution, acid washing the primary extraction solution to obtain a primary phosphoric acid, secondary extracting and oscillation separating the primary phosphoric acid to obtain a secondary extraction solution, acid washing the secondary extraction solution to obtain a secondary phosphoric acid, and then repeatedly extracting and acid leaching the secondary phosphoric acid (3 to 8 times) to obtain 20 the required phosphoric acid. Preferably, the mass proportion of P2O5 in the phosphorus concentrate in step Al is great than or equal to 24%. Preferably, the first acid in step Al is at least one of formic acid, acetic acid or phosphoric acid. Preferably, the stoichiometric ratio (kg / L) of phosphorus concentrate to the first acid used in the 25 activation reaction in step Al is (0.1-15): (0.2-30). Preferably, the second acid in step Al is hydrochloric acid with a concentration of 5.0 to 37.5 w / w%. Preferably, the stoichiometric ratio (kg / L) of phosphorus concentrate to the second acid in step Al is (0.1-15): (0.2-100). 30 Preferably, the leaching temperature in step Al is 35 to 70°C. Preferably, after adjusting the concentration with water in step Al, the concentration of the phosphoric acid in the obtained crude phosphoric acid is 1 to 30%. Preferably, the extractant in step A2 is obtained by mixing propyl acetate / propyl formate and diisopropyl ether according to a volume ratio of (0.5-5): (0.5-3). Preferably, the extraction in step A2 is to extract by mixing the crude phosphoric acid with the extractant according to a volume ratio of (1-2): (3-20). Preferably, the acid washing in step A2 is to mix the deionized water with the extraction solution according to a volume ratio of 1: (1-5), then oscillating for 1 to 10 minutes and standing still for 5 to 30 minutes, and the lower liquid being the phosphoric acid solution. Preferably, the impurity content in the phosphoric acid prepared in step A2: Ca <0.01%, Mg <0.02%, Al <0.02%. The beneficial effects of the present invention are as follows: (1) According to the preparation method of the ferrous lithium phosphate material of the present invention, a specific complexing agent is used to mix the zinc source, copper source, phosphoric acid and iron source, which is then sintered into a solid-phase material, and then it is mixed with a lithium source and sintered to prepare a zinc / copper doped bark porous ferrous lithium phosphate material, so that it has a larger surface area and richer lithium-ion binding sites, so that the chemical reaction sites of the electrochemical reaction are increased, the structure is stable, the contact range between ferrous lithium phosphate and electrolyte can be enlarged, and the lithium storage sites of the synthesized ferrous lithium phosphate are correspondingly increased. At the same time, the diffusion path of the lithium-ions is shortened, and the de-intercalation rate of the lithium-ions during charge and discharge is improved, so that it has better electrochemical performance, and can meet the increasingly high quality requirements for electrode materials in the market; (2) The phosphorus source used in the preparation method of the ferrous lithium phosphate material of the present invention is prepared from phosphorus concentrate. By using a specific extractant to extract the phosphoric acid in the crude phosphoric acid, the prepared phosphoric acid has less impurities, high purity and good separation effect. At the same time, the extraction of phosphoric acid only needs extractant and deionized water, the production process and equipment are relatively simple and can be operated continuously with large production capacity, and is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a SEM diagram of the ferrous lithium phosphate material of Embodiment 2; and 20 03 25 Figure 2 is a SEM diagram of the ferrous lithium phosphate material of Embodiment 5. DETAILED DESCRIPTION The present invention will be further described below in combination with specific 5 Embodiments. Embodiment 1: A preparation method of a ferrous lithium phosphate material including the following steps: (1) Preparation of crude phosphoric acid: weighing 0.5 kg of phosphorus concentrate (the mass proportion of P2O5 in the phosphorus concentrate being 27.3%), and mixing the same with 1.2 L of 10 acetic acid (14.7 w / w%) for activation reaction, adding 6.2 L of hydrochloric acid (26.5w / w%) for leaching at a leaching temperature of 39°C and filter-pressing to obtain a filtrate, adding 2.1 L of water to adjust the concentration to obtain 8.3 L of crude phosphoric acid solution. (2) Preparation of phosphoric acid: taking 8.3 L of crude phosphoric acid solution prepared in step (1) and mixing with 12 L of extractant (in a volume ratio of propyl acetate to diisopropyl ether of 2:0.5), extracting and sending to the oscillator, oscillating for 15 minutes, standing still and separating to obtain about 12.4 L of upper primary extraction solution and 7.9 L of lower impurity solution, mixing the primary extraction solution with 3 L of deionized water, sending the same to the oscillator, acid washing to obtain the lower primary phosphoric acid, repeating the above extractant extraction, acid washing with deionized water for 6 times for the primary phosphoric acid to obtain 20 7-time phosphoric acid, and then evaporating and dehydrating at IO7°C to obtain about 91 mL of phosphoric acid. (3) Adding 1 mL of acetyl acetone, 0.05 g of copper chloride and 0.35 g of zinc chloride to 20 mL of citric acid (17.3 w / w%), mixing the same to obtain a citric acid solution, and then adding 5.5 mL of phosphoric acid prepared in step (2) and 50 mL of ferrous sulfate solution (1.45 mol / L), mixing 25 evenly, then evaporating and dehydrating to obtain a jelly, sintering the jelly under Ar in a tubular furnace at 640°C for 12 hours, and then cooling to obtain the solid-phase material. (4) Mixing the solid-phase material prepared in step (3) with 110 mL of lithium hydroxide solution (0.708 mol / L) evenly and sending the same to a drying oven for dehydration to obtain the solid-phase material, then grinding, sintering under Ar in a tubular furnace at 710°C for 7 hours, and 30 annealing to obtain the ferrous lithium phosphate material. A ferrous lithium phosphate material was prepared by the preparation method as described above. 20 03 25 Embodiment 2: A preparation method of a ferrous lithium phosphate material including the following steps: (1) Preparation of crude phosphoric acid: weighing 0.5 kg of phosphorus concentrate (the mass proportion of P2O5 in the phosphorus concentrate being 27.2%), and mixing the same with 1.3 L of 5 acetic acid (14.7 w / w%) for activation reaction, adding 6.3 L of hydrochloric acid (26.5w / w%) for leaching at a leaching temperature of 52°C and filter-pressing to obtain a filtrate, adding 2.5 L of water to adjust the concentration to obtain 8.4 L of crude phosphoric acid solution. (2) Preparation of phosphoric acid: taking 8.4 L of crude phosphoric acid solution prepared in step (1) and mixing with 12.5 L of extractant (in a volume ratio of propyl acetate to diisopropyl ether 10 of 2:0.8), extracting and sending to the oscillator, oscillating for 15 minutes, standing still and separating to obtain about 12.8 L of upper primary extraction solution and 8.1 L of lower impurity solution, mixing the primary extraction solution with 3.5 L of deionized water, sending the same to the oscillator, acid washing to obtain the lower primary phosphoric acid, repeating the above extractant extraction, acid washing with deionized water for 5 times for the primary phosphoric acid to obtain 7-time phosphoric acid, and then evaporating and dehydrating at 107°C to obtain about 91 mL of phosphoric acid. (3) Adding 2 mL of acetylacetone, 0.15g of copper chloride and 0.1g of zinc chloride to 20 mL of citric acid (17.3 w / w%), mixing the same to obtain a citric acid solution, and then adding 5.5 mL of phosphoric acid prepared in step (2) and 50 mL of ferrous sulfate solution (1.45 mol / L), mixing 20 evenly, then evaporating and dehydrating to obtain a jelly, sintering the jelly under Ar in a tubular furnace at 640°C for 8 hours, and then cooling to obtain the solid-phase material. (4) Mixing the solid-phase material prepared in step (3) with 1 L of lithium hydroxide solution (0.708 mol / L) evenly and sending the same to a drying oven for dehydration to obtain the solid-phase material, then grinding, sintering under Ar in a tubular furnace at 710°C for 7 hours, and annealing to 25 obtain the ferrous lithium phosphate material. A ferrous lithium phosphate material was prepared by the preparation method as described above. Embodiment 3: A preparation method of a ferrous lithium phosphate material including the following steps: 30 (1) Preparation of crude phosphoric acid: weighing 0.5 kg of phosphorus concentrate (the mass proportion of P2O5 in the phosphorus concentrate being 27.4%), and mixing the same with 1.4 L of acetic acid (14.7 w / w%) for activation reaction, adding 6.8 L of hydrochloric acid (26.5w / w%) for leaching at a leaching temperature of 54°C and filter-pressing to obtain a filtrate, adding 2.8 L of water to adjust the concentration to obtain 9.4 L of crude phosphoric acid solution. (2) Preparation of phosphoric acid: taking 9.4 L of crude phosphoric acid solution prepared in step (1) and mixing with 15 L of extractant (in a volume ratio of propyl acetate to diisopropyl ether of 2.2:1.0), extracting and sending to the oscillator, oscillating for 15 minutes, standing still and 5 separating to obtain about 15.3 L of upper primary extraction solution and 9 L of lower impurity solution, mixing the primary extraction solution with 3.6 L of deionized water, sending the same to the oscillator, acid washing to obtain the lower primary phosphoric acid, repeating the above extractant extraction, acid washing with deionized water for 4 times for the primary phosphoric acid to obtain 5-time phosphoric acid, and then evaporating and dehydrating at 107°C to obtain about 90 10 mL of phosphoric acid. (3) Adding 2 mL of acetyl acetone, 0.1g of copper chloride and 0.25g of zinc chloride to 25 mL of citric acid (17.3 w / w%), mixing the same to obtain a citric acid solution, and then adding 5 mL of phosphoric acid prepared in step (2) and 50 mL of ferrous sulfate solution (1.45 mol / L), mixing evenly, then evaporating and dehydrating to obtain a jelly, sintering the jelly under Ar in a tubular furnace at 670°C for 6 hours, and then cooling to obtain the solid-phase material. (4) Mixing the solid-phase material prepared in step (3) with 105 mL of lithium hydroxide solution (0.708 mol / L) evenly and sending the same to a drying oven for dehydration to obtain the solid-phase material, then grinding, sintering under Ar in a tubular furnace at 710°C for 7 hours, and annealing to obtain the ferrous lithium phosphate material. 20 A ferrous lithium phosphate material was prepared by the preparation method as described above. Embodiment 4: A preparation method of a ferrous lithium phosphate material including the following steps: (1) Preparation of crude phosphoric acid: weighing 0.5 kg of phosphorus concentrate (the mass 25 proportion of P2O5 in the phosphorus concentrate being 27.3%), and mixing the same with 1.5 L of acetic acid (14.7 w / w%) for activation reaction, adding 7.3 L of hydrochloric acid (26.5w / w%) for leaching at a leaching temperature of 65°C and filter-pressing to obtain a filtrate, adding 2.4 L of water to adjust the concentration to obtain 9.6 L of crude phosphoric acid solution. (2) Preparation of phosphoric acid: taking 9.6 L of crude phosphoric acid solution prepared in 30 step (1) and mixing with 16 L of extractant (in a volume ratio of propyl acetate to diisopropyl ether of 2.4:1.0), extracting and sending to the oscillator, oscillating for 15 minutes, standing still and separating to obtain about 16.2 L of upper primary extraction solution and 9.4 L of lower impurity solution, mixing the primary extraction solution with 3.8 L of deionized water, sending the same to 20 03 25 the oscillator, acid washing to obtain the lower primary phosphoric acid, repeating the above extractant extraction, acid washing with deionized water for 7 times for the primary phosphoric acid to obtain 8-time phosphoric acid, and then evaporating and dehydrating at 107°C to obtain about 89 mL of phosphoric acid. 5 (3) Adding 3 mL of acetyl acetone, 0.1 g of copper sulfate and 0.2 g of zinc sulfate to 25 mL of citric acid (17.3 w / w%), mixing the same to obtain a citric acid solution, and then adding 5 mL of phosphoric acid prepared in step (2) and 50 mL of ferrous sulfate solution (1.45 mol / L), mixing evenly, then evaporating and dehydrating to obtain a jelly, sintering the jelly under Ar in a tubular furnace at 650°C for 7.5 hours, and then cooling to obtain the solid-phase material. 10 (4) Mixing the solid-phase material prepared in step (3) with 110 mL of lithium hydroxide solution (0.708 mol / L) evenly and sending the same to a drying oven for dehydration to obtain the solid-phase material, then grinding, sintering under Ar in a tubular furnace at 630 °C for 8 hours, and annealing to obtain the ferrous lithium phosphate material. A ferrous lithium phosphate material was prepared by the preparation method as described L0 above. C\J Embodiment 5: A preparation method of a ferrous lithium phosphate material including the following steps: (1) Preparation of crude phosphoric acid: weighing 0.5 kg of phosphorus concentrate (the mass CM proportion of P2O5 in the phosphorus concentrate being 27.3%), and mixing the same with 1.0 L of 20 acetic acid (14.7 w / w%) for activation reaction, adding 7.6 L of hydrochloric acid (26.5w / w%) for leaching at a leaching temperature of 68°C and filter-pressing to obtain a filtrate, adding 2.5 L of water to adjust the concentration to obtain 9.9 L of crude phosphoric acid solution. (2) Preparation of phosphoric acid: taking 9.9 L of crude phosphoric acid solution prepared in step (1) and mixing with 18 L of extractant (in a volume ratio of propyl acetate to diisopropyl ether 25 of 2.5:1.3), extracting and sending to the oscillator, oscillating for 15 minutes, standing still and separating to obtain about 18.2 L of upper primary extraction solution and 9.7 L of lower impurity solution, mixing the primary extraction solution with 3.5 L of deionized water, sending the same to the oscillator, acid washing to obtain the lower primary phosphoric acid, repeating the above extractant extraction, acid washing with deionized water for 5 times for the primary phosphoric acid 30 to obtain 6-time phosphoric acid, and then evaporating and dehydrating at 107°C to obtain about 86 mL of phosphoric acid. (3) Adding 3 mL of acetyl acetone, 0.1 g of copper sulfate and 0.3g of zinc sulfate to 30 mL of citric acid (17.3 w / w%), mixing the same to obtain a citric acid solution, and then adding 5.5 mL of phosphoric acid prepared in step (2) and 52 mL of ferrous sulfate solution (1.45 mol / L), mixing evenly, then evaporating and dehydrating to obtain a jelly, sintering the jelly under Ar in a tubular furnace at 650°C for 7.5 hours, and then cooling to obtain the solid-phase material. (4) Mixing the solid-phase material prepared in step (3) with 115 mL of lithium hydroxide solution (0.708 mol / L) evenly and sending the same to a drying oven for dehydration to obtain the solid-phase material, then grinding, sintering under Ar in a tubular furnace at 630 °C for 8 hours, and annealing to obtain the ferrous lithium phosphate material. A ferrous lithium phosphate material was prepared by the preparation method as described above. Comparative example 1: A preparation method of a ferrous lithium phosphate material including the following steps: (1) Preparation of crude phosphoric acid: weighing 0.5 kg of phosphorus concentrate (the mass proportion of P2O5 in the phosphorus concentrate being 27.3%), and mixing the same with 1.2 L of acetic acid (14.7 w / w%) for activation reaction, adding 7.3 L of hydrochloric acid (26.5w / w%) for leaching at a leaching temperature of 45°C and filter-pressing to obtain a filtrate, adding 2.5 L of water to adjust the concentration to obtain 9.2 L of crude phosphoric acid solution. (2) Preparation of phosphoric acid: taking 9.2 L of crude phosphoric acid solution prepared in step (1) and mixing with 14 L of extractant (in a volume ratio of propyl acetate to diisopropyl ether of 2:0.6), extracting and sending to the oscillator, oscillating for 15 minutes, standing still and separating to obtain about 14.2 L of upper primary extraction solution and 9.1 L of lower impurity solution, mixing the primary extraction solution with 3.5 L of deionized water, sending the same to the oscillator, acid washing to obtain the lower primary phosphoric acid, repeating the above extractant extraction, acid washing with deionized water for 5 times for the primary phosphoric acid to obtain 6-time phosphoric acid, and then evaporating and dehydrating at 107°C to obtain about 91 mL of phosphoric acid. (3) Mixing 5 mL of the phosphoric acid solution prepared in step (2) with 50 mL of ferrous sulfate solution (1.45 mol / L) evenly, evaporating and dehydrating to obtain a solid substance, sintering the solid substance under Ar in a tubular furnace at 740°C for 7.5 hours, and then cooling to obtain the solid-phase material. (4) Mixing the solid-phase material prepared in step (3) with 110 mL of lithium hydroxide (0.708 mol / L) evenly and sending the same to a drying oven for dehydration to obtain the solid-phase material, then grinding, sintering under Ar in a tubular furnace at 680°C for 10 hours, and annealing to obtain the ferrous lithium phosphate material. 20 03 25 A ferrous lithium phosphate material was prepared by the preparation method as described above. Comparative example 2: A preparation method of a ferrous lithium phosphate material including the following steps: 5 (1) Preparation of crude phosphoric acid: weighing 0.5 kg of phosphorus concentrate (the mass proportion of P2O5 in the phosphorus concentrate being 27.3%), and mixing the same with 1.2 L of acetic acid (14.7 w / w%) for activation reaction, adding 7.3 L of hydrochloric acid (26.5w / w%) for leaching at a leaching temperature of 45°C and filter-pressing to obtain a filtrate, adding 2.5 L of water to adjust the concentration to obtain 9.2 L of crude phosphoric acid solution. 10 (2) Preparation of phosphoric acid: taking 9.2 L of crude phosphoric acid solution prepared in step (1) and mixing with 14 L of propyl acetate, extracting and sending to the oscillator, oscillating for 15 minutes, standing still and separating to obtain about 14.3 L of upper primary extraction solution and 8.9 L of lower impurity solution, mixing the primary extraction solution with 3.2 L of deionized water, sending the same to the oscillator, acid washing to obtain the lower primary phosphoric acid, repeating the above extractant extraction, acid washing with deionized water for 5 times for the primary phosphoric acid to obtain 6-time phosphoric acid, and then evaporating and dehydrating at 107°C to obtain about 88 mL of phosphoric acid. (3) Adding 5 mL of phosphoric acid prepared in step (2) and 50 mL of ferrous sulfate solution (1.45 mol / L) to 30 mL of citric acid (17.3 w / w%), and mixing evenly, then evaporating and 20 dehydrating to obtain a jelly, sintering the jelly under Ar in a tubular furnace at 650°C for 7.5 hours, and then cooling to obtain the solid-phase material. (4) Mixing the solid-phase material prepared in step (3) with 110 mL of lithium hydroxide solution (0.708 mol / L) evenly and sending the same to a drying oven to obtain the solid-phase material, then grinding, sintering under Ar in a tubular furnace at 680°C for 10 hours, and annealing 25 to obtain the ferrous lithium phosphate material. A ferrous lithium phosphate material was prepared by the preparation method as described above. Experiment The contents of impurities in the crude phosphoric acid and the phosphoric acid prepared in 30 Embodiments 1-5 and Comparative Examples 1-2 were tested. The test results are shown in Table 1. At the same time, the ferrous lithium phosphate materials prepared in Embodiments 1-5 and Comparative Examples 1-2 were used as the anode material of the battery to make a button battery, and then the chemical performances of the button battery were tested, and the test results are shown 20 03 25 in Table 2. Table 1: Contents of impurities in the crude phosphoric acid and the phosphoric acid prepared in Embodiments 1-5 and Comparative Examples 1-2 Group Crude phosphoric acid (%) Phosphoric acid (%) Ca Mg Al Ca Mg Al Embodi ment 1 5.52 1.47 0.34 0.0034 0.0014 0.0007 Embodi ment 2 5.74 1.54 0.47 0.0028 0.0012 0.0005 Embodi ment 3 5.63 1.58 0.42 0.0031 0.0013 0.0007 Embodi ment 4 6.14 1.63 0.48 0.0038 0.0017 0.0004 Embodi ment 5 6.07 1.56 0.50 0.0040 0.0014 0.0004 Compara tive Example 1 6.16 1.57 0.46 0.0031 0.0018 0.0006 Compara tive Example 2 6.23 1.67 0.55 0.0172 0.0066 0.0084 Table 2: Electrochemical performance data of ferrous lithium phosphate material prepared in Embodiments 1-5 and Comparative Examples 1-2 Samples Discharge specific capacity (mAh-g4) / Circle times Coulomb efficiency (%) / Circle times BET ( m2 / g) 1 20 50 100 1 20 50 100 Embodi ment 1 148.8 139.4 131.5 124.6 83.4 88.1 91.5 97.3 1.38 Embodi ment 2 146.9 137.9 132.2 125.7 82.3 87.9 91 95.9 1.2 Embodi ment 3 154.3 153.6 131.3 127.8 81.3 86.5 92.8 95.8 1.65 Embodi ment 4 151.2 146.1 132.8 128.3 80.4 88.3 92.3 96.9 1.31 Embodi ment 5 150.3 146.7 133.6 128.6 81.9 90.7 94.5 96.3 1.47 Compara tive Example 1 140.8 137.6 130.7 127.6 80.1 84.7 89.5 93.3 1.07 Compara tive 143.6 138.3 131.2 126.1 79.6 86.8 88.2 95.0 0.92 Example 2 20 03^25 Meanwhile, the ferrous lithium phosphate material of Embodiment 2 was tested by SEM, and the test results are shown in Figure 1. The ferrous lithium phosphate material of Embodiment 5 was tested by SEM, and the test results are shown in Figure 2. 5 It can be seen from Table 2 that the specific surface area of the ferrous lithium phosphate material prepared by the preparation method of the ferrous lithium phosphate material of the present application can reach 1.2 m2 / g or more. At the same time, after the ferrous lithium phosphate material prepared by the preparation method of the ferrous lithium phosphate material of the present application is assembled into a battery, the first discharge specific capacity of the battery can reach 10 146.9 mAhg'1 or more. After 100 cycles, its specific discharge capacity is still 124.6 mAh g'1 or more, and its first coulomb efficiency is 80.4% or more. After 100 cycles, its coulomb efficiency can still reach 95.8% or more. In addition, comparing Embodiment 1 and Comparative Examples 1-2, it can be seen that when the zinc source and copper source are not mixed through the specific complexing agent of the present invention in the preparation process of the ferrous lithium phosphate material, the specific surface area of the prepared ferrous lithium phosphate material will be significantly reduced, and the performance of the battery will also be significantly reduced after the ferrous lithium phosphate material is assembled into a battery. Compared with Comparative Example 1 and Comparative Example 2, it can be seen that when 20 the crude phosphoric acid solution is obtained by leaching with hydrochloric acid from the phosphorus concentrate, and when the specific extractant in the description of the present invention is used, the impurities such as calcium, magnesium and aluminum, etc., in the phosphoric acid prepared after evaporation and dehydration will be significantly reduced. In addition, it can be seen from Figure 1 and Figure 2 that the ferrous lithium phosphate materials 25 of Embodiments 2 and 5 exhibit a bark like loose and porous structure, and at the same time Figure 2 shows the inclusion of parts of 20-50 pm spherical particles in the ferrous lithium phosphate material of Embodiment 5. 20 03 25

Claims

1. A preparation method of a ferrous lithium phosphate material, comprising the following steps:(1) mixing zinc source, copper source and complexing agent solution, then mixing with iron source and phosphoric acid source, evaporating and dehydrating to obtain a jelly, and then primary sintering the jelly under a protective atmosphere to obtain a solid-phase material;(2) mixing the solid-phase material prepared in step (1) with a lithium source, grinding and secondary sintering under a protective atmosphere to obtain the ferrous lithium phosphate material;wherein the complexing agent solution is obtained by mixing a citric acid solution and acetyl acetone, the concentration of the citric acid in the citric acid solution is 1 to 20 w / w%, and the acetylacetone accounts for 1 to 12v / v% of the citric acid solution;wherein the zinc source is at least one of zinc oxide, zinc hydroxide, zinc chloride or zinc sulfate;wherein the copper source is at least one of copper oxide, copper hydroxide, copper chloride or copper sulfate;wherein the iron source is at least one of ferrous chloride, ferrous sulfate or ferrous hydroxide;wherein the phosphoric acid source is at least one of phosphoric acid, ammonium phosphate, potassium phosphate, lithium phosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate or potassium dihydrogen phosphate;wherein the lithium source is at least one of lithium hydroxide, lithium carbonate, lithium nitrate or lithium chloride.

2. The preparation method of a ferrous lithium phosphate material of claim 1, wherein the mass of the zinc source accounts for 0.1 to 5 w / w% of the citric acid solution, and the mass of the copper source accounts for 0.1 to 5 w / w% of the citric acid solution.

3. The preparation method of a ferrous lithium phosphate material of claim 1, wherein the molar ratio of the phosphoric acid, the iron and the lithium in the phosphoric acid source, iron source and lithium source is (1.0-1.2): (1.0-1.05): (1.0-1.01).

4. The preparation method of a ferrous lithium phosphate material of claim 1, wherein the sintering temperature of the primary sintering and the secondary sintering is 600 to 950°C, and the sintering time is 6 to 15 hours.

5. The preparation method of a ferrous lithium phosphate material of claim 1, wherein the particle size of the material after grinding in step (2) is less than 80 pm.

6. The preparation method of a ferrous lithium phosphate material of claim 1, wherein the phosphoric acid source is phosphoric acid, which is prepared from phosphorus concentrate.20 03 25

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