Cathodic behavior of alkali manganese oxides from permanganate

The reaction of potassium, sodium, and lithium permanganate in water al 170 degrees C leads directly to potassium, sodium, and lithium manganese dioxides, A(y)MnO . nH(2)O, with a R(3) over barm$ 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.