Stepwise Recovery of Valuable Metals from Spent Lithium Ion Batteries by Controllable Reduction and Selective Leaching and Precipitation

The remarkably increasing consumption of lithium ion batteries (LIBs) has been an issue worldwide for the contained valuable metals and intrinsic toxicity in spent LIBs. Here, a novel process including selective leaching and precipitation has been developed for recovery of spent LIBs. The carbothermic reduction of spent LiNixCoyMn1–x–yO2 was applied to control the reduction degree of target metallic elements. Afterward, H3PO4 solution was utilized to selectively leach 99.1% of Li and 96.3% of Mn, and excellent leaching selectivity was achieved for that merely 4.5% of Co and 1.2% of Ni were dissolved. After increasing the concentrations of Li and Mn to 23.14 and 53.03 g/L by two-stage cross-current leaching, Li and Mn were precipitated and recovered in sequence by simply adjusting pH of the leaching lixivium, and compounds of Mn3(PO4)2·3H2O and MnHPO4·3H2O as well as Li3PO4 were obtained. The Ni–Co alloy contained in the filtration residue could be separated by wet magnetic separation and further recovered. It was the first time to synchronously leach Li and Mn while Co and Ni were separated simultaneously in a single leaching operation, which could greatly benefit the subsequent separation and recovery. The selective leaching and precipitation are efficient and facile and enjoy superiority over conventional processes of recycling spent LIBs.