Strategies for Synthesizing Conductive Spinel Cobalt Oxide Nanoparticles for Energy Storage Applications

Co 3 O 4 spinel type nanoparticles (5–10 nm) were synthesized by oxidizing precipitation in various basic solutions. The materials prepared in lithium-containing hydroxide solutions exhibit high electronic conductivity (higher than 10 −2 S.cm −1 at room temperature), which can be increased (up to 3 S.cm −1 ) by electrochemical oxidation. This high conductivity is due to the presence of Co 4+ ions in the octahedral framework of the spinel structure, which entails electronic delocalization. In addition to high conductivity, the obtained powder exhibits a high surface area (around 200 m 2 .g −1 ), which should be suitable for applications in electrodes: as conductive additive in the positive electrode of alkaline Ni-MH cells, or directly as electrode material in hybrid C/metal oxide supercapacitors.