Structural Characterization of Heat‐treated Electrolytic Manganese Dioxide and Topotactic Transformation of Discharge Products in the Li ‐ MnO2 Cells

Abstract

The crystal structures of heat-treated electrolytic manganese dioxide (HEMD) and the discharge products are characterized by high-spatial-resolution convergent-beam electron diffraction (CBED) and lattice imaging. In this paper, CBED results are used to clarify the ambiguity in the x-ray diffraction (XRD) patterns of these materials. The CBED results of HEMD used as the positive electrode material confirms that the major phase has the pyrolusite space group, P4,/mnm, but with a range of c/a ratios. The experimentally observed variability of the lattice parameters from grain to grain is found to coincide with broadening on the low-angle sides of the XRD peaks. Both XRD and CBED analyses indicate that the unit cell volume of the pyrolusite-type phase increases during discharge, which is consistent with previous work by Ohzuku et al. CBED patterns of the discharge products suggest that a second discharge phase is formed by a topotactic phase transformation during discharge and has a specific orientation relationship with the expanded pyrolusite-type phase. The symmetry and lattice parameters obtained from the single-crystal diffraction patterns of the second discharge phase are consistent with an intermediate structure in the mechanism proposed by David et al.' for the formation of the spinel structure upon chemical lithiation of j-MnO 2 .

The tunable electrochemical performances of carbon fluorides/manganese dioxide hybrid cathodes by their arrangements

“…14e0644). Based on the XRD pattern, after the heat treatment, gMnO 2 is converted towards g/b-MnO 2 , which is in agreement with previous reports and g/b-MnO 2 is proposed as the favorable type for Li/MnO 2 primary battery [20,21].…”

Kinetic Behavior of Manganese Dioxide in Li/MnO2Primary Batteries Investigated Using Electrochemical Impedance Spectroscopy under Nonequilibrium State

“…In addition, these XRD results are consistent with the observations reported in the literatures. 1,13 This is characteristic of a solid-solution reaction, indicating the incorporation of lithium ions into the lithiated Li x MnO 2 (0 < x < 0.03) phase, as was reported in the literature. 4 The discharge curve shows a plateau at 0.03 < x < 0.2, in agreement with theories presented in the literature, 14 which demonstrates the existence of a first-order phase-transformation reaction.…”

Study of the local structure of LiNi0.33+δMn0.33+δCo0.33−2δO2 (0.025≤δ≤0.075) oxides

“…These results are thus consistent with the conclusion that the sample with the smallest value of ı has the best crystallinity and the smallest strain field. High-resolution transmission electron microscopy (HRTEM) is a powerful analytical technique that can be used to identify components and unravel the complex features of intergrown electrode structures, for example, ␣-MnO 2 with interconnected hexagonally close-packed ␤-MnO 2 and ramsdellite-MnO 2 domains [21,22]. The HRTEM image of a LNMCO particle was taken from the surface of the particle indicated by the rectangle (Fig.…”