Li+ Extraction/Insertion Reactions with LiAlMnO4 and LiFeMnO4 Spinels in the Aqueous Phase

Spinel-type metal oxides, lithium-aluminum-manganese oxide (LiAlMnO4) and lithium-iron-manganese oxide (LiFeMnO4), were prepared by a coprecipitation/thermal crystallization method. The Li+ extraction/insertion reactions with these materials were investigated by X-ray, DTA-TG analyses, FT-IR spectroscopy, pH titration, and Kd measurement. The acid treatments of LiAlMnO4 and LiFeMnO4 caused Li+ extractions of more than 80% and 60%, respectively, while the dissolutions of Al, Fe, and Mn were less than 10%. The acid-treated samples had lithium ion-sieve properties from a microamount to a macroamount of metal ion loading in aqueous solutions. The chemical analysis showed that the Li+ extraction/insertion progressed mainly by an ion-exchange mechanism. The X-ray analyses showed that the spinel structure held during the Li+ extraction/insertion, indicating the topotactic reaction.