Thermal Treatment Effects on Manganese Dioxide Structure, Morphology and Electrochemical Performance

Abstract

Kinetic analysis is used to determine the required isothermal heating time at various temperatures to theoretically completely remove water from an electrolytic manganese dioxide (EMD) sample. The effect of the heat treatment regime on material structure, morphology and composition is investigated using various physical techniques, including X-ray diffraction and gas adsorption. Further, the electrochemical performance of heat treated• EMD (HEMD) samples at a range of discharge rates finds that material properties such as retention of the y-Mn0 2 structure and high surface area for the sample heat treated at 250°C, and extensive structural conversion and micro-pore closure in the case of the 350°C material, lead to higher capacity and power output. Conversely, significant amounts of structural water in the 200°C sample, and the compromise in structural rearrangement and surface area loss for the material prepared at 300°C, result in poor electrochemical behaviour, especially at high discharge rates. Particularly evident from this study is the complex interplay between the heat treatment regime, resulting HEMD properties and electrochemical performance.

Electrolytic manganese dioxide (EMD): a perspective on worldwide production, reserves and its role in electrochemistry

“…The investigation lead to a better understanding in this crucial area of battery material preparation and will aid in optimising the heat treatment processes that in turn can improve the overall performance of manganese dioxide as a cathode material in Li/MnO 2 primary cells. 158 Dose et al 48 discussed the post effect of heat treated manganese dioxide when it undergoes reduction in nonaqueous media. 156 and 157) showed that synthetic g-MnO 2 /EMD includes structural domains of ramsdellite and pyrolusite varieties, and that heat-treatment up to 400 C or elevated temperature lead to the progressive transformation of ramsdellite domains into pyrolusite domain, or with g-MnO 2 (orthorhombic unit cell) to b-MnO 2 (tetragonal unit cell).…”

Electrochemical Oxidation of Carboxylic Acids in the Presence of Manganese Chloride

“…34,35 Current reports have suggested that EMD essentially consisted of epsilon-manganese dioxide (ε-MnO 2 ) or a mixture of γ-MnO 2 and ε-MnO 2 . [36][37][38] Mn 2+ + 2H 2 O → 2e − + 4H + + MnO 2 (Anode) [10] 2H + + 2e − → H 2 (Cathode) [11] …”

Electrolytic Manganese Dioxide Coatings on High Aspect Ratio Micro-Pillar Arrays for 3D Thin Film Lithium Ion Batteries

“…γ-MnO 2 is described as an intergrowth between Pyrolusite and ramsdellite-forms of MnO 2 [ 27 ]. The as-prepared EMD contains water in its film structure [ 48 ]. In order to enable reversibility and avoid lithium hydroxide formation upon Li-ion intercalation tests, removal of water from EMD thin films is necessary.…”