Realizing continuous recycling of wasted LCO based on extractants functioning as H+ diffusion pump

Abstract

The recycling of spent lithium-ion batteries (LIBs) has significant importance, yet the efficiency in conventional hydro-extraction metallurgy is limited by the batch-to-batch production with the additional use of strong acid and alkali. Herein, we report the successful realization of continuous recycling of wasted lithium cobalt oxide (LCO) with high efficiency in an innovative leaching solution||extractant||stripping solution system, featuring the use of extractant as the H⁺ ion diffusion pump. This system integrates ascorbic acid (VC) as the leaching agent, Di-(2-ethylhexyl) phosphoric acid (P204) as the extractant, and oxalic acid (OA) as the stripping and precipitation agent, working synergistically to achieve cobalt leaching, transfer, and precipitation. Unlike conventional protocols, the leaching region could self-regulate its pH value because the H⁺ consumed/generated is simultaneously compensated, thus enabling high efficiency (complete leaching was achieved in 7 min at 80 °C, with 85 % extraction efficiency reached in 10 min) due to the Le Chatelier principle and avoiding the need for additional acid or alkali, thus enabling continuous production. Additionally, the extractant remains stable and perfectly isolates the leaching and stripping phases or agents to prevent non-selective compounds migration, enabling long-term recovery operations. Our strategy, which utilizes the extractant as an H⁺ diffusion pump, is expected to be generally applicable for realizing continuous and efficient production in various hydrometallurgical processes.