Structural stabilization of Cr-doped spinel LiMn₂O₄ for long-term cyclability towards electrochemical lithium recovery in original brine

Current explosive demand in raw lithium greatly boosts lithium mining, and electrochemical Li-extraction using spinel LiMn2O4 (LMO) from original brine has gained much attentions. In this study, Cr-doped LMO is prepared via a facile precipitation-calcination to elucidate the structural alterations and suppress Jahn-Teller distortion, and a novel hybrid capacitive deionization (HCDI) system of "Li-poor LiMn1.8Cr0.2O4||brine (recovery liquid)|| activated carbon" is constructed for electrochemical Li-extraction. The results prove that Cr-doping effectively suppresses Mn3+ disproportionation induced by Jahn-Teller distortion, leading to a stabilized spinel framework for long lifespan. Importantly, the Cr-doping LMO realizes a stable (de)lithiation over 500 cycles with low manganese dissolution rate of 0.027 % per cycle. Meanwhile, the Li-extraction capacity can reach 22 mg g(-1) in 1.0 M LiCl electrolyte with retention rate of 86.05 % after 500 cycles. In the assembled HCDI system, average Li-extraction capacity in brine reaches -15 mg g(- 1) after 15 cycles. Therefore, the HCDI system using Cr-doping LMO could introduce a new perspective for the industrial Li-extraction facing original brine.