Improvement of lithium-containing manganese dioxide (composite dimensional manganese oxide: CDMO) as positive material for lithium secondary batteries

Abstract Lithium-containing manganese dioxide (CDMO) has been developed as the positive material for lithium secondary batteries. CDMO is prepared from lithium salt and manganese dioxide by heat treatment. The material is a composite oxide of γ/β-MnO 2 and Li 2 MnO 3 . The charge condition has been investigated in order to develop an improved CDMO that will exhibit a higher discharge voltage and a larger capacity. CDMO charged to a high potential (i.e., 3.6 V versus LiAl electrode) displays higher discharge voltage and larger capacity than CDMO subjected to normal charge (i.e., 3.3 V versus LiAl). It is concluded that when CDMO is charged to a high potential, lithium inserted not only by electrochemical reaction but also by heat treatment are removed from the γ/β-MnO 2 phase. The optimum conditions for preparing improved CDMO is to heat treat LiOH and electrolytic manganese dioxide (EMD) at a Li/Li+Mn atomic ratio of 0.3 at ∼250 °C. The improved CDMO delivers a discharge capacity of over 200 mA h g −1 . Also, excellent rechargeability is experienced, even when CDMO is charged to a high potential.