Rocking-chair electrochemical lithium recovery system with enhanced cycling stability via state-of-charge (SoC) control

초록

This study presents a rocking-chair electrochemical lithium recovery (RCELR) system that uses lambda-MnO2and LiMn2O4 electrodes, optimized for high-salinity brine conditions. A partial state-of-charge (SoC) control strategy was introduced to address the structural degradation and capacity fading of LiMn2O4 electrodes during deep cycling. Electrochemical tests confirmed that LiMn2O4 exhibits high selectivity for Li* over Na*, with minimal Na* intercalation. Compared to full charge/discharge operation (100 % SoC), partial (60 %) SoC control significantly enhanced the cycling stability (78.1 % vs. 55.1 % capacity retention after 100 cycles) while maintaining comparable lithium recovery rates. An X-ray diffraction analysis revealed reduced lattice distortion under SoC control operation, indicating improved structural integrity. Additionally, the results of lithium recovery tests show that 60 % SoC operation lowered energy consumption by 24 % and improved Li*/Na* selectivity. In conclusion, the SoC control operation in RCELR is an effective and practical design strategy to enhance the durability, energy efficiency, and separation performance of systems operating in high-Na* environments.

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