Breaking the trade-off between capacity, stability, and selectivity for electrochemical lithium extraction via a dual-ion doping strategy

Abstract

With the rapid expansion of electric vehicle markets, the efficient selective extraction of lithium from salt lakes is critical to addressing the supply-demand gap. Against this backdrop, hybrid capacitive deionization (HCDI) technology has drawn tremendous interest in lithium extraction owing to superior selectivity and low pollution. However, conventional Li+-extraction electrodes still face significant challenges in balancing electrosorption capacity, stability, and selectivity. This work proposed a dual-ion doping strategy to achieve Fe3+ and Cl− co-doped Li3V2(PO4)3 (FC-LVP), aimed at enhancing the electrochemical lithium extraction performance of LVP electrode. The 0.15FC-LVP electrode exhibited an ultra-high specific capacity of 415.5 F g−1, a maximum electrosorption capacity of 19.1 mg g−1, and an electrosorption capacity retention of 79 % after 100 cycles. Furthermore, exceptional Li+ selectivity coefficients of 610.6 and 343 are achieved in simulated salt solutions with Mg/Li and Na/Li molar ratios of 60:1 and 45:1, respectively. The electrochemical behavior, in-situ X-ray diffraction (XRD) analysis, and an evaluation of actual brine sourced from Xizang, China, collectively demonstrate the feasibility of the 0.15FC-LVP for lithium extraction. Theoretical calculations reveal that the Fe and Cl co-doping improves the structural stability and electrochemical activity of LVP by lowering the formation energy and band gap. This work presents a novel approach for designing HCDI electrodes with high stability, capacity, and selectivity in extracting lithium from salt lake.