Electrochemical characteristics of rancieite-type manganese oxide by mechanochemical synthesis

Rancieite-type manganese oxide is synthesized by a mechanochemical method and its electrochemical characteristics as a cathode material for lithium secondary batteries are examined. The discharge capacity increases with milling time up to 45 h with a maximum of 274 mAh g−1. Further increase in milling time causes a decrease in capacity due to a phase transformation. Lithium insertion into the rancieite-type manganese cathode is composed of two processes, one between 2.0 and 4.0 V and the other between 1.5 and 2.0 V. The former is due to the reduction of Mn4+ to Mn3+, while the latter is due to the reduction of Mn3+ to Mn2+. These processes are identified by X-ray absorption spectra. The specific capacity of the rancieite-type manganese oxide shows good cycleability without transition to a spinel-like structure.