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 LiMn2O4 material. This study addresses this challenge by introducing a novel RA-LiMn2O4 material with a core–shell structure, incorporating rutile-anatase (RA) as the shell and spinel LiMn2O4 as the core to enhance stability. Remarkably, the RA-LiMn2O4 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-LiMn2O4 as the working electrode. This work presents an ultrastable RA-LiMn2O4 material for lithium extraction from real brine.