Reduced Lattice Constant in Al-Doped LiMn₂O₄ Nanoparticles for Boosted Electrochemical Lithium Extraction.

Abstract

Extracting lithium selectively and efficiently from brine sources is crucial for addressing energy and environmental challenges. The electrochemical system employing LiMn₂O₄ (LMO) electrodes has been recognized as an effective method for lithium recovery. However, the lithium selectivity and stability of LMO need further enhancement for its practical applications. Herein, the Al-doped LMO with reduced lattice constant is successfully fabricated through a facile one-step solid-state sintering method, leading to enhanced lithium selectivity. The reduced lattice constant in Al-doped LMO is proved through spectroscopic analyses and theoretic calculations. Compared to the original LMO, the Al-doped LMO (LiAl_0.05Mn_1.95O₄, LMO-Al0.05) exhibits highercapacitance, lower resistance, and improved stability. Moreover, the LMO-Al0.05 with reduced lattice constant can offer higher Li⁺ diffusion coefficient and lower intercalation energy revealed by cyclic voltammetry and multiscale simulations. When employed in hybrid capacitive deionization (CDI), the LMO-Al0.05 obtains a Li⁺ intercalation capacity of 21.7 mg g^-1 and low energy consumption of 2.6 Wh mol^-1 Li⁺. Importantly, the LMO-Al0.05 achieves a high Li⁺ extraction percentage (≈86%) with Li⁺/Na⁺ and Li⁺/Mg²⁺ selectivity of 1653.8 and 434.9, respectively, in synthetic brine. The results demonstrate that the Al-doped LMO with reduced lattice constant could be a sustainable solution for electrochemical lithium extraction.