Wesley M. Dose

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

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-Mn02 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.

Thermal expansion of manganese dioxide using high-temperature in situ X-ray diffraction

High-temperature in situ X-ray diffraction is used to determine the thermal expansion behaviour of manganese dioxide in air at temperatures between 298 and 673 K, the range accessible prior to material decomposition. Two manganese dioxide samples of different origins are investigated to observe the effect of synthesis conditions and resultant material properties on the thermal response. β-MnO2 prepared by a chemical pathway is found to expand linearly over the temperature window with thermal expansion coefficients (in units of K−1) of αa = 9.3 (4) × 10−6, αc = 7.0 (2) × 10−6 and β = 25.6 (8) × 10−6. Conversely, the thermal expansion of heat-treated electrolytic manganese dioxide is disjointed about 473 K in the a direction and for the overall unit-cell volume, and about 523 K in the c direction. Coefficients are therefore given (in units of K−1) as αa = 23 (4) × 10−6 (298–473 K), 10 (3) × 10−6 (473–673 K); αc = 0.2 (9) × 10−6 (298–523 K), 10 (1) × 10−6 (523–673 K); and β = 49 (9) × 10−6 (298–473 K), 26 (5) × 10−6 (473–673 K).

Monitoring the Effects of Thermal Treatment on Properties and Performance During Battery Material Synthesis

© 2012 Dose and Donne, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Monitoring the Effects of Thermal Treatment on Properties and Performance During Battery Material Synthesis