Sustainable recovery of key metals from spent zinc-manganese batteries enabled by recyclable deep eutectic solvent

As the most widely consumed type of batteries, zinc-manganese batteries (ZMBs) pose significant environmental risks due to the migration of hazardous components through ecological chains. Addressing this issue aligns with the urban mining paradigm, which seeks to unlock resource potential for green, low-carbon societies. Here, we propose a precipitant-free strategy for the selective recovery of Mn and Zn from spent ZMBs utilizing a recyclable choline chloride-oxalic acid dihydrate deep eutectic solvent (ChCl-OAD DES). The designed DES achieves high leaching efficiency of the battery powders, with leaching efficiencies of 99.57 % for Mn and 99.85 % for Zn within just 10 min at 80 ℃. A unique coordination mechanism enables the selective recovery of Mn and Zn successively without additional chemical additives. Specifically, 97.5 % of Mn is recovered as MnC 2 O 4 ·2H 2 O with a purity of 99.7 % after the leachate is left to stand at 25 ℃ for 12 h. Subsequently, Zn 2+ combines with C 2 O 4 2- to form ZnC 2 O 4 ·2H 2 O by adjusting the water content, achieving a recovery efficiency of 99.2 % and a purity of 98.9 %. Importantly, the ChCl-OAD DES maintains its structural integrity and performance across three regeneration cycles through the evaporation of water and replenishment of oxalic acid dihydrate. This closed-loop methodology establishes a sustainable hydrometallurgical paradigm, offering dual advantages in preventing secondary pollution and maximizing resource efficiency in battery recycling technologies.