Suppressed Mn dissolution behavior to improve cycling performance of Cr-modified Li1-xMn2O4 electrodes

Abstract

Stably and efficiently extracting lithium from brine sources is critical for addressing pressing energy and environmental challenges. LiMn₂O₄ electrodes are widely used in electrochemical lithium recovery systems due to their effectiveness in lithium extraction. However, their limited extraction capacity and insufficient stability hinder their practical application. To overcome these challenges, we synthesized a series of Cr-modified LiMn₂O₄ (111) crystal plane materials, driven by the understanding that the multi-electron nature of Cr could improve stability without compromising lithium adsorption capacity. Indeed, the Cr-modified LiMn₂O₄ showed significantly enhanced performance, including reduced Mn dissolution (3.73 %), lower resistance, and better stability compared to the unmodified LiMn₂O₄ (1.38 %). The experimental results demonstrated that Cr doping successfully enhanced the material's stability, and theoretical calculations further confirmed that Cr incorporation enhances the electrode's lithium adsorption ability, as evidenced by the more negative adsorption energy for Li(H₂O)₄⁺ (–3.52 eV for Mn₂O₄ vs. –4.09 eV for Cr_1.0Mn_1.0O₄), thereby improving its overall adsorption performance. LiCr_1.0Mn_1.0O₄, with an expanded lattice constant, demonstrated a higher Li⁺ diffusion coefficient (6.90*10⁻¹¹) and lower intercalation energy, as verified by cyclic voltammetry. In hybrid capacitive deionization (CDI) experiments, LiCr_1.0Mn_1.0O₄ showed a minimal Mn dissolution loss of only 1.37 %, while maintaining a Li⁺ intercalation capacity of 21.51 mg/g. These findings highlight the potential of Cr modification on the (111) facets of LiMn₂O₄ as an effective strategy to enhance electrochemical lithium extraction performance, providing a promising approach for efficient lithium recovery in practical applications.