Fe-Doped LiMn2O4 Hollow Nanofibers: Ultrafast Ion-Transfer for Lithium Extraction from Brines with Cycle Stability

The escalating global demand for lithium, driven by the green energy transition, necessitates efficient lithium extraction strategies from salt-lake brine and seawater. This study introduces a porous LiFexMn2–xO4 hollow nanofibers (LFMO-h), synthesized by electrospinning and calcination. This material features a well-defined one-dimensional (1D) hollow architecture composed of interconnected spinel nanocrystals (∼80 nm), which establishes ultrashort ion diffusion pathways and abundant active surfaces, enabling ultrafast Li+ transport and rapid adsorption kinetics. The ion diffusion coefficient of LFMO-h is as high as ∼6.6 × 10–10 cm2 s–1, ten times faster than bulky LMO (LMO-s). As a cathode in a hybrid capacitive deionization system, LFMO-h achieves a high Li+ adsorption capacity of ∼1.4 mmol g–1 with an energy consumption of ∼4.7 Wh mol–1. Remarkably, LFMO-h presents a super Mg2+/Li+ selectivity (αMg2+Li+ = 180 at CMg2+/CLi+ = 60), while maintaining structural integrity and negligible Mn dissolution during prolonged cycling, attributed to synergistic Fe-doping and dense arrangement of nanocrystals. Even in the simulated high Mg2+ salt-lake brine, LFMO-h retains its high adsorption capacity and selectivity, demonstrating robustness under practical conditions. This work pioneers an accelerated diffusion-adsorption strategy through 1D hollow nanofiber engineering for energy-efficient lithium recovery technologies.