A Recyclable Cooperative Approach for Selective Lithium Recovery from Industrial-Grade Spent Lithium-Ion Battery Black Mass via Oxidative Delithiation and Complexation Mechanism

Extracting lithium selectively from an industrial-grade lithium-ion battery (LIB) black mass having multiple metal ions is challenging but crucial from an industrial standpoint. However, most of the methods involve harsh conditions and sacrificial reagents, are energy-intensive and time-consuming, and generate secondary pollution. This study presents a lithium selective, ligand-assisted cooperative approach for the selective leaching of lithium under mild conditions. It is revealed that the synergistic actions of anthraquinone salt (Na2AQAc) and H2O2 generate highly reactive oxygen species (ROS) such as center dot OH, center dot O2-, and 1O2 that facilitate oxidative delithiation supported by spin trapping EPR and quenching experiments. As a result, a phase transition of cathode material and concurrent lithium abstraction by the ligand, forming an octanuclear lithium complex ([Li8(AQAc2-)2(mu-OH2)2(H2O)12]4+) in the leachate was observed. Consequently, a leaching efficiency of 97% with over 99% selectivity was achieved under the optimized conditions of 3.5% H2O2 (v/v), 30 degrees C, 72 mM Na2AQAc, 40 g L-1 pulp density, and a reaction time of 1 h. A recycling strategy was demonstrated to recover anthraquinone acid, and lithium was separated as high-purity Li2CO3. This method offers the advantages of room-temperature operation, neutral pH conditions, shorter time duration, minimal reagent usage, and the ability to recycle the reagents.