One-Pot Tandem Conversion Strategy Enables Atom-Economical Recovery of Spent Layered Oxide Cathodes

The efficient and sustainable recycling of valuable metals from spent lithium-ion batteries (LIBs) presents a significant challenge, as conventional hydrometallurgical methods often suffer from harsh operational conditions and inefficient reagent utilization. Herein, we report an atom-economical one-pot tandem conversion (OTC) strategy for the rapid recovery of critical metals from spent layered oxide cathodes (i.e., LiNi_0.5Co_0.2Mn_0.3O₂). This approach completely converts cathode powder into transition metal oxalates and a lithium-rich solution in a single reactor at 80 °C within 20 min, achieving > 98% recovery for Ni/Co/Mn and 99.4% for Li. Crucially, near-quantitative (≈100%) utilization of stoichiometrically dosed K₂SO₃, ascorbic acid (AA), and oxalic acid (Ox) is confirmed by ion chromatography and pH tracking, leaving negligible reagent waste. Mechanistic investigations combining experimental evidence and theoretical calculations reveal that the OTC strategy proceeds through a uniquely orchestrated, pH-modulated sequence, where the reductive activation, coordinative dissolution, and spontaneous precipitation are decoupled and activated in a sequential manner to avoid the competitive interactions that plague conventional one-pot systems. The OTC strategy demonstrates broad applicability across various layered oxide cathodes, establishing a green and efficient paradigm for spent LIB recycling that significantly enhances both leaching kinetics and atom economy compared to existing hydrometallurgical routes.