A rechargeable non-aqueous secondary cell comprising a negative electrode; a positive electrode comprising a lithium containing manganese oxide as its active material, wherein the positive electrode has a specific surface area measured by the BET method of 9.0 m.sup.2 /g to 67.5 m.sup.2 /g; and a separator interposed between the positive and the negative electrodes which is impregnated with a non-aqueous electrolyte. A recharageable non-aqueous secondary cell comprising a negative electrode; a positive electrode comprising a lithium containing manganese oxide as its active material, which has grain sizes of substantially 20 .mu.m or less, when observed by a scanning electron microscope; and a separator interposed between the positive and said negative electrodes impregnated with a non-aqueous electrolyte.