New Mg and Ca exchanged derivatives of Li1.1V3O8: Synthesis, characterization and lithium insertion behavior

This is the first report of Li+ ion exchange by a divalent cation in the inter-layer space of the Li1.1V3O8 structure. New Mg and Ca partially substituted materials were prepared from two Li1.1V3O8 precursors annealed at 350degreesC or at 650degreesC. The materials obtained have the same structure and the same morphology (no crystal shape or well formed crystals, respectively) as the precursors, but their inter-layer spacing is slightly less and their surface area is larger The Li insertion behavior of the substituted materials shows two main kinds of behavior depending on the precursor used for the synthesis. The ion-exchange leads to both enhanced cycling capacity and decreased relative capacity loss on cycling for the 350degreesC derivatives. The diminution of relative capacity loss on cycling is believed to come from a structural stabilization by the divalent cation pillars, which better pin the layers together The 650degreesC derivatives keep the excellent cyclability of the precursor as a consequence of the preservation of the initial morphology, and exhibit an enhanced cycling capacity due to the increase in surface area.