US-12626965-B2 - Preparation method of heterosite iron phosphate and application thereof

US12626965B2US 12626965 B2US12626965 B2US 12626965B2US-12626965-B2

Abstract

The invention belongs to the field of battery material recovery, and discloses a preparation method and application of heterosite phosphate. The method comprises the following steps: mixing lithium iron phosphate with a solvent, adding an acid solution, and adjusting the pH to obtain an acidic lithium iron phosphate liquid; adding a transition metal additive to the acidic lithium iron phosphate liquid, and performing leaching in an intensifying micro-environment, followed by filtrating to obtain heterosite iron phosphate and a lithium-rich solution. The leaching rate of lithium in the leaching solution reaches 90.5-99.9%, and both of the iron and phosphorus content in the leaching solution are less than 0.1 ppm; the recovered heterosite iron phosphate has a purity of 99.9%, and the recovery rate of the heterosite iron phosphate is 99.3%.

Inventors

Shili Zheng
Dingshan RUAN
Changdong LI
Ying Zhang
Zhi Sun
Yang Zhang
Xiaojian Wang

Assignees

GUANGDONG BRUNP RECYCLING TECHNOLOGY CO., LTD.
Hunan Brunp Recycling Technology Co., Ltd.
HUNAN BRUNP EV RECYCLING CO., LTD.

Dates

Publication Date: 20260512
Application Date: 20211013
Priority Date: 20201203

Claims (15)

1 . A preparation method of heterosite iron phosphate, comprising the following steps: (1) mixing lithium iron phosphate with a solvent to obtain a slurry, adjusting the slurry to an acidic pH to obtain an acidic lithium iron phosphate liquid; (2) adding a transition metal additive to the acidic lithium iron phosphate liquid to obtain a mixture, performing leaching in an intensifying micro-environment to the mixture, followed by filtration to obtain the heterosite iron phosphate and a lithium-rich solution; the leaching in the intensifying micro-environment is to leach iron phosphate out of the acidic lithium iron phosphate liquid with microbubbles or under controlled pressure; wherein the microbubbles are produced by introducing a gas into the acidic lithium iron phosphate liquid; the controlled pressure increases the oxygen oxidation potential by changing the partial pressure of oxygen in the leaching environment; the microbubbles, or oxygen microbubbles/dissolved oxygen produced by the controlled pressure generate hydroxyl radicals under surface catalysis of the transition metal additive, used for improving the oxidation capacity and oxidation reaction rate of ferrous iron in the lithium iron phosphate liquid.
2 . The preparation method according to claim 1 , wherein in step (1), adjusting the slurry to the acidic pH is carried out by adding a liquid acid into the slurry, wherein the liquid acid is at least one selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid; and the liquid acid has a concentration of 0.5-5 mol/L.
3 . The preparation method according to claim 1 , wherein in step (1), the lithium iron phosphate is recovered from a waste lithium iron phosphate cathode material.
4 . The preparation method according to claim 1 , wherein the microbubbles are generated by introducing a gas into the acidic lithium iron phosphate liquid, wherein the gas is air or oxygen; the microbubbles generated by introducing the gas into the acidic lithium iron phosphate liquid have diameters of 10-50 μm.
5 . The preparation method according to claim 1 , wherein the controlled pressure is 0.05-1 Mpa.
6 . The preparation method according to claim 1 , wherein in step (2), the transition metal additive is at least one selected from the group consisting of nickel oxide, cobalt tetroxide, manganese dioxide, lithium cobaltate, lithium nickelate, lithium manganate, and lithium-nickel-cobalt manganate.
7 . The preparation method according to claim 1 , wherein in step (2), the acidic lithium iron phosphate liquid and the transition metal additive are in a mass-volume ratio of 50-400 g/L.
8 . The preparation method according to claim 1 , wherein in step (2), the lithium-rich solution is subjected to a purification process comprising the following steps: adjusting the lithium-rich solution to an alkaline pH; removing impurities to obtain a purified solution; then adding sodium carbonate to the purified solution to react; filtering and drying a resulting precipitate to obtain lithium carbonate.
9 . Battery cathode material prepared by of the preparation method of claim 1 .
10 . Battery cathode material prepared by the preparation method of claim 2 .
11 . Battery cathode material prepared by the preparation method of claim 3 .
12 . Battery cathode material prepared by the preparation method of claim 4 .
13 . Battery cathode material prepared by the preparation method of claim 5 .
14 . Battery cathode material prepared by the preparation method of claim 6 .
15 . Battery cathode material prepared by the preparation method of claim 7 .

Description

TECHNICAL FIELD The invention relates to the technical field of battery recycle, and in particular to a preparation method of heterosite iron phosphate and application thereof. BACKGROUND In recent years, with rapidly increasing electronic and electrical equipment output, the demand for lithium-ion batteries has also continued to rise. However, lithium-ion batteries have a limited service life, thereby a large number of waste lithium-ion batteries are produced every year. If these lithium ion batteries cannot be properly recycled, serious resource and environmental problems will arise. On the one hand, lithium ion batteries contain high levels of valuable metals, such as lithium, nickel, cobalt, and manganese, the contents of which in lithium ion batteries are much higher than their average contents in ores. If the metals cannot be properly recycled, it will cause a huge waste of resources; on the other hand, the heavy metals and harmful electrolytes in the waste lithium ion battery will also cause potential harm to natural environment and human health. If these lithium-ion batteries can be effectively recycled, not only a large amount of valuable metals can be recovered, and resource waste can be reduced, but also the pressure on ecological and environmental protection can be reduced. Among the cathode materials for lithium ion batteries, ternary cathode materials and LiFePO4 cathode materials occupy a considerable market share due to their excellent performance. Among the ternary cathode materials, lithium, nickel, cobalt, and manganese are valuable metals with high recovery value, while in LiFePO4 cathode materials, lithium has a high recovery value. Therefore, the recovery of LiFePO4 cathode mainly focuses on the recovery of lithium. At present, the recovery of lithium iron phosphate cathode materials is mainly through wet technology, comprising the following ways: (1) Excess acid+excess oxidant completely leaches the lithium iron phosphate to obtain a mixture, and then adjusts the pH of the mixture to precipitate FePO4·2H2O though binding of Fe3+ and PO43−, and then a lithium-containing solution is obtained; (2) The stoichiometric ratio of acid and oxidant selectively leaches lithium to obtain a lithium-containing solution and iron phosphate. The iron phosphate recovered by these two methods is mainly precipitated in the form of FePO4·2H2O, which is difficult to dissolve in acid. To further recover the iron and phosphorus resources, a calcination is needed before FePO4·2H2O can be dissolved, which makes the recovery of iron and phosphorus resources difficult. At the same time, the oxidants used in the leaching process of the above methods are mainly chemical reagents such as hydrogen peroxide, persulfate, sodium hypochlorite, etc., and the leaching cost is high. Therefore, there is an urgent need to develop a lithium iron phosphate recovery process with high leaching selectivity, low leaching cost, and short recovery process. SUMMARY OF THE INVENTION An objective of the present invention is to provide a preparation method and application of heterosite iron phosphate, addressing the problems in the prior art of the iron phosphate recovery such as poor selectivity for lithium extraction, high consumption of agents, long recovery process, and low product value. By providing an improved process, direct preparation of heterosite lithium phosphate is achieved while possessing the advantages of low impurity content in the leaching solution, high lithium concentration, low agent's consumption, and high lithium recovery rate. In order to achieve the aforementioned objective, the following technical solution is adopted in the invention. A preparation method of heterosite iron phosphate comprises the following steps: (1) Mixing lithium iron phosphate with a solvent to obtain a slurry, adding an acid solution and adjusting the slurry to acidic pH to obtain an acidic lithium iron phosphate liquid;(2) Adding a transition metal additive to the acidic lithium iron phosphate liquid to obtain a mixture, performing leaching in an intensifying micro-environment to the mixture, followed by filtrating to obtain a heterosite iron phosphate and a lithium-rich solution; the leaching in an intensifying micro-environment is to leach iron phosphate out of the acidic lithium iron phosphate liquid with microbubbles or under controlled pressure; The heterosite iron phosphate is a product obtained by delithiation of an olivine-type lithium iron phosphate. At present, there are many crystal phases of iron phosphate reported in literatures: the orthorhombic heterosite iron phosphate formed by delithiation of the lithium iron phosphate, monoclinic iron phosphate, orthorhombic iron phosphate, or α-quartz crystal iron phosphate; its aqueous phase comprises monoclinic iron phosphate dihydrate and orthorhombic iron phosphate dihydrate. Preferably, in step (1), the lithium iron phosphate is recovered from waste lithium iron phosphate cathode