Abstract: A positive electrode for Li/MnO.sub.2 batteries uses as its active material .gamma.-MnO.sub.2, which differs from the structurally similar electrolytic or synthetic manganese dioxide through the absence of water and from its dehydration product, which is .beta.-MnO.sub.2, through better electrochemical utilization capability. The modified .gamma.-MnO.sub.2 is obtained by reduction of electrolytic manganese dioxide by means of hydrazine into .alpha.-MnO(OH) and by oxidation of the latter through tempering in an oxygen stream at about 280.degree. C.