Enhanced H-storage property in Li–Co–N–H system by promoting ion migration

Motivated by the ion migration mechanism proposed by David et al. [J. Am. Chem. Soc. 129 (2007) 1594–1601], we mechanically mill the Li3N/Co powder mixture to obtain defective Li3N-type structure with enhanced Li+ mobility. Compared with Li3N, the hydrogen storage property of such defective phase is markedly improved, presumably due to the ion-migration-enhancing effect from the incorporation of Co and Fe (from milling utensils). During subsequent cycling, however, this effect cannot persist due to the precipitation of Co–Fe alloy upon hydrogenation. The close correlation between Co–Fe incorporation/precipitation and property variation of Li3N hydrogen storage material provides a preliminary evidence to support the ion migration mechanism.