Synthesis and soft-chemical reactivity of layered potassium cobalt oxide

A layered potassium cobalt oxide of KxCoO2 (x = 0.55) was prepared by solid-state reaction between KO2 and Co3O4. We explored soft-chemical reactivities of this material in treatments with acid or bromine solutions by following compositional and structural changes by X-ray diffraction and chemical analysis. The acid treatment promoted K+/H3O+ exchange but concurrently induced the formation of CoOOH as a side product. The compound underwent oxidative deintercalation of K+ upon the action of Br2, which was accompanied by hydration. Reinsertion of alkali metal ions into the resulting Br2-treated sample could be attained by the treatment with corresponding hydroxide solutions.