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Manganese Dioxides: Structural Model and In-Situ Neutron Powder Diffraction Investigation of Thermal Annealing and Electrochemical Reduction

  • M. Ripert (a1) (a2), J. Pannetier (a1), Y. Chabre (a3) and C. Poinsignon (a2)

Abstract

Starting from the seminal work of De Wolff [1], we have developed a structural description, based on two kinds of defects, which accounts for the scattering function of all γand ε-MnO2. Using numerical simulation results, we propose simple methods to estimate the parameters which characterize real manganese dioxide samples. Real time neutron powder diffraction has been used to investigate in situ the transformations undergone by γ-MnO2 during thermal annealing and electrochemical reduction in alkaline solutions. We have found that thermally induced transformation from MnO2 to ∝-Mn2O3 can involve up to seven different steps and that electrochemical reduction of γ-MnO2 in KOD electrolyte proceeds through three stages, the final one leading in most cases to a breakdown of the initial crystal lattice.

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Work supported by the PIRSEM/CNRS (ARC-IPROM)

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1- Wolff, P.M. De, Acta Cryst. 12, 341345 (1959)
2- Ruetschi, P., J. Electrochem. Soc. 131, 27372744 (1984); 135, 2657-2662 (1988)
3- Ripert, M., Thesis, INPG, Grenoble (1990)
4- Pannetier, J., Chabre, Y. & Poinsignon, C., ISSI Lett. 1, 57 (1990)
5- Klinsberg, C. & Roy, R., Am. Miner. 44, 819838 (1959)
6- Maskell, W.C., Shaw, J.A.E. & Tye, F.L., J. Applied Electrochem. 12, 101108 (1982)
7- Glasser, L.S.D. & Ingram, L., Acta Cryst. B24, 12331236 (1968)
8- Chabre, Y. & Ripert, M., this MRS meeting
9- Chabre, Y., J. Electrochem. Soc., in press

Manganese Dioxides: Structural Model and In-Situ Neutron Powder Diffraction Investigation of Thermal Annealing and Electrochemical Reduction

  • M. Ripert (a1) (a2), J. Pannetier (a1), Y. Chabre (a3) and C. Poinsignon (a2)

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