ELECTROCHEMISTRY OF MANGANESE-DIOXIDE IN LITHIUM NONAQUEOUS CELL .2. X-RAY DIFFRACTIONAL AND ELECTROCHEMICAL CHARACTERIZATION ON DEEP DISCHARGE PRODUCTS OF ELECTROLYTIC MANGANESE-DIOXIDE

X-ray diffractional and electrochemical characterization of deep discharge products (LixMnO2s) of heat-treated electrolytic MnO2s (HEMDs) from 200° to 450°C at 50°C intervals were carried out. XRD examinations of the discharged LixMnO2s indicate the core structures were the same regardless of startingoHEMDs used. All LixMnO2 XRD patterns were indexed and explained using an orthorhombic unit cell having a = ca. 10A, b = ca. 5A, and c = ca. 2.85A. Possible structures having such a unit cell were discussed based on models which consisted of [1 x 1]-, [1 x 2]-, and [1 x 3]-tunnel structures. Electrochemical tests of discharge products indicated the LixMnO2s were rechargeable in lithium nonaqueous cell, i.e., 150–180 mAh - g-1 of rechargeable capacity. The reaction mechanism of LixMnO2 in the rechargeable region was also examined and shown to be a homogeneous-phase reaction in a LixMnO2 matrix, which anisotropically shrank and expanded within ca. 10% in unit cell volume during the oxidation and reduction, respectively. These XRD and electrochemical studies showed the possibility of rechargeable lithium/manganese dioxide cells. © 1990, The Electrochemical Society, Inc. All rights reserved.