Medium-entropy engineering of spinel LiMn2O4 for boosted stability and selectivity in lithium extraction from brine via capacitive deionization

Medium-entropy doping strategy is introduced to stabilize spinel LMO for electrochemical lithium extraction. • Medium-entropy regulation effectively suppresses Jahn–Teller distortion and stabilizes the spinel framework. • Optimized Li + migration pathways significantly enhance Li + diffusion kinetics and intercalation reversibility. • The ME-LMO electrode delivers high Li + adsorption capacity with low energy consumption. • Superior Li + selectivity is achieved in both binary systems and simulated salt lake brines. Selective lithium extraction from salt lake brines is critical for sustainable lithium supply under the global energy transition. LiMn 2 O 4 (LMO) is a promising electrode material for lithium extraction via capacitive deionization (CDI), yet its practical application is crippled by Jahn–Teller distortion and subsequent Mn dissolution. Herein, a multicomponent-doped LMO (ME-LMO, LiMn 1.98 Mg 0.005 Al 0.005 Co 0.005 Ni 0.005 O 4 ) was synthesized via a one-step solid-state sintering method using a medium-entropy configuration strategy to regulate lattice stability and Li + migration behavior. The synergistic interplay of multiple cations not only regulates local lattice strain and redistributes the Mn 3+ /Mn 4+ ratio to suppress the Jahn–Teller distortion and inhibit Mn leaching, but also induces lattice contraction and electronic modulation that collectively expedite Li + diffusion and enhance intercalation reversibility. Theoretical calculations further reveal that the multi-element doping configuration reconstructs the local Mn O electronic structure and provides more favorable thermodynamic conditions for Li + insertion. Benefiting from these synergistic effects, ME-LMO achieves a high Li + adsorption capacity of 24.23 mg g −1 , low energy consumption of 2.07 Wh mol −1 , and outstanding cycling stability with 86.6% retention after 100 cycles. More importantly, it exhibits extraordinary Li + selectivity, with separation factors of 78.98 (Li + /Na + ) and 91.19 (Li + /Mg 2+ ) in binary systems, and remarkably 994.28 (Li + /Na + ) and 289.62 (Li + /Mg 2+ ) in simulated brines. This work demonstrates the potential of a medium-entropy configuration strategy for stabilizing spinel frameworks and improving the performance of LMO-based electrodes for energy-efficient lithium extraction from complex brines. Download: Download high-res image (226KB) Download: Download full-size image