Engineering surface wettability of LiMn2O4 via β-cyclodextrin-derived porous carbon for efficient electrochemical lithium extraction from high Na/Li ratio brines.

Electrochemical methods enable energy-efficient Li extraction from salt-lake brines with low environmental impact. Nevertheless, the performance of LiMn2O4 (LMO) electrodes in practical systems is restricted by insufficient surface wettability, limited Li+ transport kinetics, and dissolution of Mn, especially in high Na/Li ratio brines. Herein, a hydrophilic porous carbon layer derived from β-cyclodextrin and chitosan (PCM) was constructed on the surface of LMO to engineer the electrode/electrolyte interface. At the optimal PCM loading of 3 wt% (LMO-3PCM), the water contact angle decreased from 70.9° to 34.8°, the charge-transfer resistance decreased from 4.65 to 4.10 Ω, and the average Li+ diffusion coefficient increased from 1.33 × 10-10 to 2.20 × 10-10 cm2/s, demonstrating improved wettability and interfacial Li+ transport. In simulated brine, LMO-3PCM achieved Li+ extraction and release capacities of 20.11 and 18.98 mg/g/h, respectively, with a recovered Li+ purity of 95.96% and an energy consumption of only 2.35 Wh/mol. LMO-3PCM enhanced the Li/Na separation factor from 25.92 to 56.98 in highly alkaline lithium precipitation mother liquor. Meanwhile, the PCM layer reduced Mn dissolution and improved the structural durability of LMO during repeated extraction/release cycles. These results demonstrate that regulating surface wettability through cyclodextrin-derived porous carbon provides an effective strategy for improving interfacial ion transport and electrochemical lithium extraction from complex brines.