From the vanadates to 3d-metal oxides negative electrodes

With respect to lithium batteries, vanadate-based electrodes display large electrochemical capacities that rapidly decay during the cycling. A full study of the 3d-metal(M)-based vanadates performed using in situ DRX, XAS and TEM has enabled to pinpoint the important role of the 3d-metal cations, and has motivated the study of simple metal oxides MO, (M=Co, Ni, Cu, Fe) in rechargeable Li cells. We found that these materials could reversibly react with a large amount of lithium leading to capacities as high as 800 mAh/g. The reactivity mechanism totally differs from the well established one based on Li insertion-deinsertion or Li alloying reactions but mainly involves the formation of highly reactive metallic nanoparticles that favor Li₂O formation-decomposition. Besides, we gave experimental evidence of an electrochemically driven polymerization-dissolution process at low potential, which is highly reversible, and emphasized the importance of the role of the electrolyte on such a process. Finally, the universality of this mechanism to account for the large Li reactivity at low voltage in many 3d-metal (Co, Ni, Fe, Cu, Mn)-based oxides is discusséd together with the urgent issues to be solved for such oxide anodes to stand as serious alternative candidates for today’s carbon anodes in Li-ion cells. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.