Lithium recovery from spent lithium-ion batteries (LIBs) becomes increasingly important due to the shortage of lithium resources. The difference in the stability for metal sulfates enlightened us to preferentially extract lithium from spent Ni− Co−Mn ternary (NCM) material through selective sulfation and simple water leaching. The effect of important variables on the metals' leaching efficiency was systematically investigated. Additionally, combined thermodynamic analysis and characterizations were used to investigate the conversion mechanism in the sulfation roasting process. After roasting with (NH 4 ) 2 SO 4 at 650 °C, LiNi x Co y Mn z O 2 is completely decomposed and converted into Li 2 SO 4 , NiO, Co 3 O 4 , and LiMn 2 O 4 . Over 90% of lithium can be selectively water leached at ambient temperature in only 0.5 h, and then battery-grade Li 2 CO 3 (purity>99.90%) can be successfully prepared without prior concentration and purification processes. Furthermore, sulfation roasting also promotes the extraction of Co and Ni in the following acid leaching process. Finally, a closedloop and green process was presented for recycling spent NCM materials. Our work represents an environmentally friendly and economically feasible approach, which has great prospect for the industrial-scale recycling of spent LIBs. The finding may also have general implications in the recycling of multiple metals containing hazardous materials.

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