Selective Electrochemical Recovery of Valuable Metals from Spent Lithium-Ion Batteries Using a Betaine-Based Deep Eutectic Solvent

Abstract

The rapid growth in lithium-ion battery (LIB) deployment has led to increasing volumes of end-of-life batteries, creating an urgent need for sustainable recycling technologies capable of recovering critical metals from complex waste streams. Although leaching has been successfully shown in various DES systems, selective recovery of metals/metal oxides still remain a challenge. In this study, a deep eutectic solvent (DES) of betaine hydrochloride and ethylene glycol is employed as a green medium for both dissolution of valuable metals and selective electrochemical recovery from LIB black mass. Rapid dissolution of Li, Ni, Co, and Mn together with 86% Cu was achieved within 30 min at 100 °C. Based on electrochemical studies, it was observed that temperature and potential/ current can be adjusted for selective metal recovery. Copper was selectively deposited at 40 °C, while increasing the deposition temperature to 60 and 80 °C enabled deposition of Ni–Co alloys. Manganese was recovered from the remaining electrolyte via carbonate precipitation. The integrated process achieved overall recovery efficiencies of approximately 98% for Cu, ∼90% for Ni and Co, and ∼80% for Mn. Thus, this work demonstrates a selective and environmentally benign strategy for recovering valuable metals from complex LIB waste streams, providing a promising pathway toward circular battery recycling.