Abstract
Electrochemical reduction of synthetic was examined in nonaqueous lithium cells. Synthetic containing (empirical formula , ), K+(, ), and Rb+ ions (,) having tetragonal lattices (, ) were examined. These three exhibited distorted S‐shaped discharge curves in the voltage range of 2.0–3.5V. Discharge capacities of these were observed to be 170–220 mAh · g−1. Utilization was 70–80% based on available Mn4+ ions for and 80–90% for both and . X‐ray diffractional examinations indicated that the a‐axis expanded almost linearly as a function of degree of reduction and the c‐axis remained almost constant. From these experimental results we have concluded that the reduction of proceeded topotactically in one phase in nonaqueous lithium cells, i.e., octahedral Mn4+ ions were reduced to Mn3+ ions in a solid matrix and Li+ ions inserted into tunnel cavities due to the charge compensation without destruction of the framework structure.
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