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

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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 LiFe x Mn 2– x O 4 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 cm 2 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 Mg 2+ /Li + selectivity ( α M g 2 + L i + = 180 at C Mg 2+ / C Li + = 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 Mg 2+ 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.