Electrochemistry of Manganese Dioxide in Lithium Nonaqueous Cell: III . X‐Ray Diffractional Study on the Reduction of Spinel‐Related Manganese Dioxide

Abstract

X‐ray diffractional and electrochemical studies of the reduction of a spinel‐related manganese dioxide, , were carried out in lithium nonaqueous cells. The reduction of this oxide proceeded topotactically in three steps; a reduction in two phases was characterized by a constant open‐circuit voltage (OCV) of 4.110(5)V for in , a reduction in one phase characterized by an S‐shaped OCV curve [mid‐point, 3.94(1)V] for , and a reduction in two phases of cubic and tetragonal characterized by an L‐shapedOCV curve at 2.957(5)V for . An observed voltage separation of ca. 1V, which begins at a critical composition of , was considered from the structural data of to be a difference in a solid‐state redox reaction of a , i.e., the vs. redox reactions, and an effect of deformation of a from to (Jahn‐Teller distortion) upon an electrode potential of was discussed.