Stepwise recovery of critical metals from spent NCM lithium-ion battery via calcium hydroxide assisted pyrolysis and leaching

The stepwise extraction of critical metals from spent LiNixCoyMnzO2 lithium-ion batteries (NCM LIBs) has received particular attention for efficient resource recycling. In present paper, Ca(OH)2 was used as an additive in the pyrolysis process to realize the stepwise recovery of critical metals from spent NCM LIBs. During the Ca(OH)2 assisted pyrolysis, lithium in the NCM was converted into LiOH, Li2O, Li2CO3 and LiF. Under optimal conditions, exceeded 93 % of lithium can be extracted preferentially by water leaching without additional additives and the recovery efficiencies of nickel, cobalt and manganese reached 99 % by subsequent acid leaching. Furthermore, LiOH·H2O was successfully prepared by evaporation and crystallization of lithium leachate. The addition of Ca(OH)2 could achieve the in-situ fixation of harmful pyrolytic gas, the transformation of lithium phase and reduction of cathode materials, which promoted the lithium leaching. This study provides an environmentally-friendly and competitive process for recycling spent NCM LIBs by pyrolysis.