On the incorporation of extra Li in lithium cobaltate Li1 + xCo1 − xO2
Abstract Novel Li 1 +  x Co 1 −  x O 2 compositions were prepared by two synthesis methods: solid-state reaction between Li 2 O 2 and Co 3 O 4 under high pressure and mechanochemically assisted reaction between CoOOH and LiOH.H 2 O. Variation of the Li-to-Co ratio in the precursor mixture from 1.0 to 1.5 resulted in the formation of Li 1 +  x Co 1 −  x O 2 compositions with x  ~ 0.12. The structure and cationic distribution in Li 1 +  x Co 1 −  x O 2 were monitored by XRD powder analysis, TEM analysis and 6 Li MAS NMR spectroscopy. Pure Li 1 +  x Co 1 −  x O 2 with Li 2 Ti 2 O 4 -type spinel structure was obtained under high pressure only. Mechanochemically assisted synthesis at 400 °C yielded layered LiCoO 2 with a small amount of spinel-type Li 1 +  x Co 1 −  x O 2 . The spinel modification of LiCoO 2 is able to accommodate extra Li, so that the Li-to-Co ratio is higher than 1. The layered modification of LiCoO 2 is more rigid with respect to the accommodation of more than one lithium atom.