Improved rechargeability of manganese oxide cathodes in alkaline cells in the presence of TiB2 and TiS2

The rechargeability of electrolytic manganese dioxide (EMD) cathodes in the presence of small amounts (<5 wt.%) of TiB2 and TiS2 additives has been investigated in alkaline cells in the one electron regime and the data are compared with those obtained with the already known Bi2O3 additive. Both the TiB2 and TiS2 additives are found to offer slightly better cyclability at higher number of cycles compared to the Bi2O3 additive. However, the incorporation of small amounts of TiB2 or TiS2 into the Bi2O3 additive leads to a significant improvement in the cyclability compared to the Bi2O3 additive, possibly due to a synergistic effect. X-ray diffraction patterns recorded before and after 30 cycles as well as cyclic voltammograms recorded after 3 and 30 cycles reveal that the better cyclability in the presence of TiB2 and TiS2 additives is due to the suppression of the formation of unwanted, electrochemically inactive birnessite and hausmannite phases and a shifting of the second electron capacity of Mn to higher potentials.