Amorphous manganese oxide remains amorphous upon lithium intercalation and cycling

Lithium intercalation in amorphous manganese oxide, synthesized by a room temperature aqueous oxidation route, is analyzed. As reported before, the material yields a very high intercalation capacity and also shows promising rate capability as cathode for rechargeable lithium batteries. The present study investigates the structure of the material using X-ray powder diffraction conducted on composite cathode pellets at different stages of discharge and after discharge/charge cycling. Contrary to the behavior of many crystalline manganese oxides that exhibit a tendency to undergo a transformation to a spinel-like phase, the amorphous manganese oxide does not show such a tendency and remains X-ray amorphous upon lithium intercalation and cycling. In fact, the material appears to become even more disordered upon repeated cycling. The results indicate the kinetic stability of the amorphous structure in allowing high-capacity, single-phase and reversible lithium intercalation and suggest the potential of far-from-equilibrium structures as promising intercalation hosts. (C) 2004 Elsevier B.V. All rights reserved.