Recycling method of waste lithium iron phosphate battery

Abstract

The invention relates to a method for recycling waste lithium iron phosphate batteries. The method comprises the following steps: pretreating the waste lithium iron phosphate batteries to obtain electrode active material powder; carrying out ball-milling mixing on the obtained material and sodium salt; roasting the mixture in a muffle furnace to obtain a roasted material; the roasted material is subjected to low-temperature water leaching, and phosphorus enrichment liquid and leaching residues are obtained through filtering; evaporating and concentrating the phosphorus-enriched liquid to obtain industrial-grade sodium phosphate, and leaching the leaching slag by adopting dilute acid under oxygen pressure to obtain lithium-enriched liquid and iron-enriched slag; and after purifying and removing impurities from the lithium-enriched liquid, adding a saturated sodium carbonate solution to prepare the battery-grade lithium carbonate. According to the method, the sodium salt auxiliary agent is adopted for assisting roasting to promote the waste lithium iron phosphate battery powder to be subjected to crystal transformation to separate out phosphorus, then iron and lithium are separated in a dilute acid oxygen pressure leaching mode, and extraction and separation of iron, phosphorus and lithium in the waste lithium iron phosphate battery powder are synchronously achieved.

Description

technical field [0001] The invention relates to the technical field of recycling waste batteries, in particular to a method for recycling waste lithium iron phosphate batteries. Background technique [0002] With the rapid development of modern science and technology, the problem of social energy and environmental ecological pollution has become increasingly prominent, and the environmental and ecological pollution of various waste batteries has become the focus of social attention. Lithium-ion batteries are widely used in power batteries and energy storage batteries due to their high capacity, stable cycle performance, and high working platform voltage. Power and energy storage batteries usually require more battery materials than conventional small batteries. Therefore, in the next 3-5 years, a large number of lithium-ion batteries will be scrapped, and their recycling has high social value. [0003] However, at present, there are still defects in the domestic technical r...

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Problems solved by technology

[0003] However, at present, there are still defects in the domestic technical route of recycling waste lithium iron phosphate. The mainstream way to deal with the electrode active materials of waste lithium iron phosphate batteries is acidic reduction leaching to obtain Li + , Fe 2+ 、PO 4 3- , F - 、Al 3+ and Fe 3+ Plasma leaching solution, precipitation to remove aluminum, adsorption to remove fluorine, then adjust the pH value and add oxidant to precipitate to obtain FePO 4 , and finally adjust the pH and add Na 2 CO 3 get Li 2 CO 3

For example, "A Method for Preparing Lithium Iron Phosphate Cathode Material from Waste Lithium Iron Phosphate Batteries" announced by Chinese patent CN111009660B uses acid leaching-precipitation method to recover valuable metals in waste Lithium iron phosphate batteries, and first uses inorganic acid to leach electrode active materials Obtain the leaching solution, iron powder is replaced to remove copper, precipitate and remove aluminum, then add alkali and oxidant to control the pH value to obtain iron phosphate, and finally recover lithium. This method realizes the recovery of waste lithium iron phosphate, but the purity of the recovered product is not high , The problem of low lithium recovery rate

Another example is the "Comprehensive Recovery Method for Waste Lithium Iron Phosphate Battery Positive Electrode Materials" published by Chinese patent CN110459828A. Dilute acid and oxidant are used to leach waste lithium iron phosphate battery pole powder to obtain lithium enrichment solution, which is then purified and removed by precipitation to obtain lithium carbonate. ; FePO is obtained after acid leaching purification and impurity removal on the leaching slag 4 , this method realizes the recycling of waste lithium iron phosphate batteries, but the acid leaching of the pre-extracted lithium leaching residue must strictly control the reduction conditions to prevent Fe 3+ generation, and in Fe 2+ It is difficult to remove impurities from the solution under existing conditions

[0004] There is also a method to peel off the positive electrode sheet to obtain the positive electrode material, and then carry out acid leaching or pre-extraction of lithium to obtain a leaching solution containing Li, Fe and P or to obtain a Li-rich leaching solution and leaching residue, and pre-extract Fe from the leaching solution. , P and then extract Li or directly extract Li, this method has the difficulty of thoroughly removing impurities and purifying the leaching solution, the purity of the recovered product is not ideal, and the Fe and P in the pre-extracted lithium leaching slag all enter the solution, which will lead to purification difficulties

[0005] The existing conventional positive electrode material recovery method is easy to cause lithium loss, and the lithium recovery rate is not high. In addition, it is difficult to remove impurities in the iron-containing leachate during the recovery process, and it is difficult to obtain battery-grade iron phosphate that meets industry standards.

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