Improvement by heating of the electronic conductivity of cobalt spinel phases, electrochemically synthesized in various electrolytes

Myriam Douin (1, 2) , Liliane Guerlou-Demourgues (1) , Michel Ménétrier (1) , Emilie Bekaert (1) , Lionel Goubault (2) , Patrick Bernard (2) , Claude Delmas (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 Direction de la recherche

The nature of the alkaline electrolyte (based on KOH, NaOH, LiOH), in which Co₃O₄ spinel type phases are synthesized by electrooxidation of CoO, is shown to play a key role on the composition, the structure and the electronic conductivity of the materials. In the materials, prepared in pure LiOH electrolyte or in mixed ternary electrolyte (KOH, NaOH, LiOH), Co⁴⁺ ions are present in the octahedral framework, which entails electronic delocalization in the cobalt T_2g band and a high conductivity. The structure of the sample, synthesized in KOH, is on the opposite closer to that of ideal Co₃O₄, with only Co³⁺ in the octahedral sublattice, which leads to a semi-conducting behavior. Whatever the initial material, a thermal treatment induces an increase of the Co⁴⁺/Co³⁺ ratio in the octahedral network, resulting in a significant increase of the electronic conductivity.

Mots clés: Spinel; Cobalt oxide; Electronic conductivity; Alkaline battery

Domaines: Matériaux

Myriam Douin, Liliane Guerlou-Demourgues, Michel Ménétrier, Emilie Bekaert, Lionel Goubault, et al.. Improvement by heating of the electronic conductivity of cobalt spinel phases, electrochemically synthesized in various electrolytes. Journal of Solid State Chemistry, 2009, 182 (5), pp.1273-1280. ⟨10.1016/j.jssc.2009.02.018⟩. ⟨hal-00382826⟩