Electrochemistry of Manganese Dioxide in Lithium Nonaqueous Cell: II . X‐Ray Diffractional and Electrochemical Characterization on Deep Discharge Products of Electrolytic Manganese Dioxide

Abstract

X-ray diffractional and electrochemical characterization of deep discharge products (Li=MnO2s) of heat-treated electrolytic MnO2s (HEMDs) from 200 ~ to 450~ at 50~ intervals were carried out. XRD examinations of the discharged Li=MnO2s 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 • 1]-, [1 z 2]-, and [1 • 3]-tunnel structures. Electrochemical tests of discharge products indicated the Li=MnO2s were rechargeable in lithium nonaqueous cell, i.e., 150-180 mAh -g-1 of rechargeable capacity. The reaction mechanism of LixMnO~ in the rechargeable region was also examined and shown to be a homogeneous-phase reaction in a Li=MnO2 matrix, which anisotropically shrank and expanded within ca. 10% in unit cell volume during the oxidation and reduction, respectively. These XRD and electrochemi-) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-08 to IP ABSTRACTThe hot corrosion of preoxidized 99% and 99.99% pure Ni covered with a thin Na2SO4 film in a SO2-O2 gas atmosphere was investigated at 900~ by an electrochemical method using a sodium sensor and an oxygen probe. The preoxidation conditions were varied in order to affect the sulfidation of Ni, which resulted in an increase in salt basicity and thereafter catastrophic corrosion. The basicity gradient generated across the thin salt film supported a self-sustaining basic fluxing and reprecipitation of the protective NiO scale.

Characterizations on the structural and electronic properties of thermal lithiated Li0.33MnO2

“…It is shown that the Even though the crystal structure of Li 0.33 MnO 2 has been well established, it is still ambiguous on the structural changes of this material during electrochemical process. Ohzuku et al [16] assumed that the material's structure was practically unchanged during Li intercalation. However, the voltage plateau near 2.9 V on the discharge potential profile clearly indicates a phase transition and the coexistence of two phases.…”

Preparation, characterization and electrochemical performance of γ-MnO2 and LiMn2O4 as cathodes for lithium batteries

“…In the anodic scan there is an oxidation peak at about 3.25 V, this peak is attributed to the removal of lithium from the structure. There is a significant decrease in the reduction peak on the second cycle of a cyclic vol- Both R-MnO2 [10] and EMD [11] show a large drop after the first discharge capacity, but deliver steady capacities starting from the second cycle when they cycled in the potential range 3.8 -2 V.…”

Cathodes for lithium ion batteries: the benefits of using nanostructured materials

“…128,129 In the composition range, 0<x<1, at 4 V, the structure of Li x Mn 2 O 4 remains cubic. At 3 V, in the composition range 1.0<x<2.0 the cubic spinel phase transforms into an ordered tetragonal rock-salt phase, NaCl-type structure.…”