An Ultrastable RA-LiMn₂O₄ Lithium-Ion Sieve for Lithium Extraction from Brine

The surging demand for lithium, driven by the expanding market for electric vehicles and electronic devices, necessitates efficient lithium extraction methods. A reverse lithium-ion battery (RLiB) method, utilizing a lithium-ion sieve to directly extract Li + from brine, offers the advantages of high selectivity and environmental friendliness. However, implementation of RLiB systems has been hindered by the limited cycling stability of the LiMn 2 O 4 material. This study addresses this challenge by introducing a novel RA-LiMn 2 O 4 material with a core–shell structure, incorporating rutile-anatase (RA) as the shell and spinel LiMn 2 O 4 as the core to enhance stability. Remarkably, the RA-LiMn 2 O 4 material demonstrates exceptional cycling stability, maintaining full capacity even after 100 cycles of charging–discharging in an aqueous LiCl electrolyte. Moreover, concentration polarization during lithium extraction is alleviated, and Li + is successfully extracted from real brine (309 ppm of Li + ) using RA-LiMn 2 O 4 as the working electrode. This work presents an ultrastable RA-LiMn 2 O 4 material for lithium extraction from real brine.