Synthesis, characterization and application of doped electrolytic manganese dioxides

Electrolytic manganese dioxides (EMDs) were prepared on the 100 g scale by anodic deposition from acidic aqueous solutions of manganese sulfate. In si tu doping with titanium ions was achieved by addition of tetra-n-butoxytita nium to the electrolytic bath. Samples were also doped ex situ by washing t he products with aqueous barium hydroxide solution. The EMDs were character ized by electron microscopy studies and BET surface area determinations. Cy clic abrasive stripping voltammetry was successfully applied to evaluate th e rechargeability of the newly synthesized undoped and doped EMDs in 9 M KO H. Relative discharge capacities at different depths of discharge (DOD) wit h respect to the first one-electron reduction of gamma-MnO2 are compared fo r different EMDs. At about 30% DOD, resulting relative discharge capacities show essentially the same trend as those measured in AA cells from about 1 0 to 20 discharge/charge cycles onwards. Accordingly, titanium-doped EMD wa s shown to exhibit superior charge retention and rechargeability when compa red to the titanium-free samples. (C) 1999 Elsevier Science S.A. All rights reserved.