One-step constant current electrolysis for selective lithium separation from spent lithium-ion batteries

The separation of lithium from spent lithium-ion batteries (LIBs) is a critical challenge for sustainable energy development and resource conservation. In this study, we proposed a novel one-step constant current electrolysis (CCE) process for selective separation and recovery of lithium from spent ternary cathode materials, specifically LiNi_0.76Co_0.22Al_0.02O₂ (NCA). The developed process achieved a selective lithium separation of 99.4 % under the optimized conditions (with the current density of 20 A·m⁻² and electrolyte concentration of 0.05 mol·L^-1 Na₂SO₄ for an electrochemical separation duration of 120 min). Meanwhile, the high current efficiency (94.7 %) and low energy consumption (39.1 Wh·mol⁻¹) highlight the economic and environmental advantages of the process. This approach can also be successfully extended to other cathode materials, such as LiNi_0.5Co_0.3Mn_0.2O₂ (NCM), with a high selective separation rate of lithium ions (Li⁺). The effectiveness of the CCE process is attributed to an orderly opened ternary layered structure of the cathode materials, which can facilitate the release of Li⁺ under appropriate electrolysis conditions. Crucially, the transition metal elements, nickel and cobyalt, were minimally leached during the electrolysis process. Nickel (Ni³⁺) was transformed into Ni(OH)₂, and cobalt (Co²⁺) was oxidized to Co³⁺, maintaining the charge balance after the release of Li⁺. This streamlined and scalable approach represents a significant advancement in separation and purification technology, offering a sustainable solution for lithium recovery from spent LIBs.