Direct Recycling of Mixed-Oxide Cathodes: Balancing Cost, Performance and Environmental Trade-Offs

We compare solid-state relithiation (SSR), hydrothermal relithiation (Hydro), molten salt thermochemistry (MST), electrochemical (EC), and chemical (Chem) methods using harmonized techno-economic (Group I), electrochemical (Group II), and environmental/toxicological (Group III) metrics. SSR/Hydro occupies a leading position in Group I. EC combines low energy (143.0 kJ·g⁻¹) with higher material cost (147.7$·kg⁻¹) at the laboratory scale, yielding 71.9 pts, while Chem remains competitive (77.8 pts) despite elevated 201.4$·kg⁻¹ and moderate energy consumption of 333.7 kJ·g⁻¹. In Group II, MST and SSR lead (64.0 and 61.1 pts), followed by Chem, Hydro, and EC. In Group II, Chem/MST shows the best rate capability recovery, EC—cycling stability recovery, MST—capacity recovery. Group III follows the energy consumption track. The CO₂ emission declines as follows: EC < Chem < MST < Hydro < SSR, with method toxicity near moderate hazard for SSR/MST/Hydro/EC and highly reactive / highly toxic for Chem. Integrated performance for Groups I–III is close for methods with energy control in the range of 60–65 points (SSR, Hydro, MST, EC), while Chem leads (72.3 points). For Ni-rich cathodes, transferable methods should include a brief high-temperature step. EC/Chem can only be used for mild regeneration.