Investigation Of LiFePO4-based Spent Lithium-ion Battery For The Recovery Of Valuable Metals

With the rapid development of electric vehicles?EVs?and hybrid electric vehicles?HEVs?,in recent years,the LiFePO4-based lithium-ion battery has been applied widely.But it has also brought the severe shortage of the supply of lithium resource and rising price of lithium salt.In order to relieve the degree of monopoly of lithium resource in the world,the huge demand of lithium salt during the development of EVs/HEVs in China and the massive spent LiFePO4-based lithium-ion batteries that should be disposed when the vehicles become scrap in the future,recycling and recovering the spent LiFePO4-based lithium-ion battery will accordingly be very important.This paper focus on the recovery of valuble metals from spent LiFePO4-based lithium-ion batteries.Firstly,the battery was pre-treatmented and recycled preliminarily.Then,the cathode material obtained from the pre-treatment were leached by oxalic acid and sulfuric acid respectively.At last,using chemical precipitation to separate the Li and Fe from the leaching solution was investigated in detail.In the process of leaching cathode material by oxalic acid,using the principle that Fe²⁺ can easily form the precipitate of FeC₂O₄·2H₂O with C₂O₄^2-,therefore,the primary separation of Li and Fe can be achieved.Maximum leaching of Li?100%?and minimum leaching of Fe?10.3%?were recorded at mass ratio of cathode material/oxalic acid of 2:3,leaching time of 120 min,leaching temperature of 25 ?,L/S ratio of 6 mL/g and stirring speed of 250 rpm.89.7%Fe were recycled in the form of FeC₂O₄·2H₂O during the leaching process.The XRD,SEM and chemical analysis tests of the FeC₂O₄·2H₂O product also were conducted respectively.In the end,two flow charts of following deeply impurity removal and recycle were proposed.In the process of leaching cathode material by sulfuric acid,the maximum leaching of Li?100%?and Fe?99.1%?were recorded at H₂SO4 concentration of 2 mol/L,H₂O2 concentration of 6 vol.%,leaching temperature of 60 ?,leaching time of 120 min,L/S ratio of 7 mL/g and stiring speed of 250 rpm.The XRD and SEM tests were conducted to assure the leaching effect.In addition,the Li and Fe in Li-Fe-P solution were separated by chemical precipitation.According to the reaction principle,chemical and TG analysis,when the pH value was less than 4.93,Fe was precipitated in the form of FePO4·2H₂0 and did not find obvious Li loss?less than 2%?;when the pH value was more than 5.57,the FePO4·2H₂O began to convert into Fe?OH?3,meanwhile,Li loss was obvious as it coprecipitated in the form of Li3PO4.The Fe precipitation of above 99.98%and Li loss of less than 2%were recorded under the conditions of reaction temperature 25?,using NaOH as precipitant,reaction time of 30 min and pH value of 3.05-4.90.Finally,the Li was recoveried by introducing Na3PO4 into the solution as Li3PO4 product,the precipitation of Li in the first cycle could achieve 87.3%.This paper presented the feasible processes of leaching by oxalic acid and sulfuric acid leaching-chemical precipitation to recovery valuble metals from spent LiFeP04-based lithium-ion batteries,it can be valuble reference and guidance for the research and industrial application of disposing spent battry.