Cathodic behavior of alkali manganese oxides from permanganate

The reaction of potassium, sodium, and lithium permanganate in water at 170°C leads directly to potassium, sodium, and lithium manganese dioxides, A_yMnO · nH₂O, with a R3m rhombohedral structure. These crystalline layered structures after dehydration readily and reversibly react with lithium through an intercalation mechanism. The capacity for lithium is a function of the alkali ion present, and the larger potassium ion maintains the capacity best. For lithium there is a tendency to convert to the spinel structure which leads to loss of capacity.