An analytical study of LiMn2O4 electrode stability under state-of-charge control during rocking-chair electrochemical lithium recovery from spent Li-ion battery wastewater

초록

Electrochemical lithium recovery from spent battery wastewater is a promising route for securing secondary lithium resources, but LiMn2O4 (LMO) electrode degradation remains a key limitation under practical wastewater conditions. In this study, a state-of-charge (SoC) controlled rocking-chair electrochemical lithium recovery (RCELR) system was investigated for Li+ recovery from actual spent battery wastewater. The LMO electrode maintained its characteristic Li+ insertion/extraction behavior in wastewater electrolytes. Limiting the operation to 60% SoC improved the capacity retention after 50 cycles from 45.9% to 70.2% and suppressed the increase in charge-transfer resistance compared to 100% SoC operation. XRD, XPS, and SEM-EDS analyses showed that partial SoC operation reduced lattice distortion, Mn surface chemical changes, carbon accumulation, and Mn loss. Moreover, 60% SoC operation maintained comparable Li+ recovery while decreasing the cycle-level electrochemical energy consumption from 9.95 to 8.52 Wh/mol Li. These findings indicate that SoC controlled operation can enhance the stability and energy efficiency of LMO-based RCELR systems for real spent battery wastewater treatments.

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