Maximizing energy utilization and lithium leaching efficiency via sequential electrochemical dual-oxidation and soaking-relaxation

Given the escalating global demand for lithium resources, optimizing electric energy consumption in the electrochemical dual-oxidation (EDO) process, which includes both electrode oxidation and electrocatalytic oxidation, for lithium leaching from spent lithium-ion cathodes, is imperative. Herein, we propose an energy-effective two-stage continuous oxidation method for lithium leaching from various composition spent ternary lithium-ion batteries (NCM) cathodes. Coupling EDO (stage I) with soaking relaxation (stage II) enables both commercial and spent LiNi_1/3Co_1/3Mn_1/3O₂ (NCM111) cathodes to achieve optimal electric energy efficiencies, with lithium leaching efficiencies of 99.87% and 98.12%, respectively. A comprehensive mechanism study reveals that the EDO not only drives lithium leaching from NCM111 lattice at stage I, but also effectively induces the transformation of lattice oxygen (O^2-) into oxidized lattice oxygen (O^n-, n < 2), thus driving the continuous lithium leaching at stage II with 49.78% reduction in electric energy consumption. This work unravels the electrical energy profile and structural dynamics during the EDO lithium leaching process, which paves the way for implementing the EDO method for the industrial sustainable recovery of critical metals.