The influence of bismuth oxide doping on the rechargeability of aqueous cells using MnO2 cathode and LiOH electrolyte

Bi-doped manganese dioxide (Mn02) has been prepared from -y-Mn02 by physical admixture of bismuth oxide (1303). The doping improved the cycling ability of the aqueous cell. These results are discussed and compared with the electrochemical behavior of bismuth-free Mn02. Batteries using the traditional potassium hydroxide (KOH) electrolyte are non-rechargeable. However, with lithium hydroxide (LiOH) as an electrolyte, the cell becomes rechargeable. Furthermore, the incorporation of bismuth into Mn02 in the LiOH cell was found to result in significantly longer cycle life, compared with cells using uncloped Mn02, The Bi-cloped cell exhibited a greater capacity after 100 discharge cycles, than the uncloped cell afterjust 40 cycles. X-ray diffraction and the microscopic analysis suggest that the presence of Bil' ions reduces the magnitude of structural changes occurring in Mn02 during cycling. Comparison with additives assessed in our previous studies (titanium disulfide (TiS2); titanium boride (TiB2)) shows that the best rechargeability behavior is obtained for the current Bi-cloped Mn02. As the size of Bil' ions (0.96 A) is much larger than Mn31 (0.73 A) or Mn2' (0.67 A) they have effectively prevented the formation of non-rechargeable products. (c) 2008 Elsevier Ltd. All rights reserved.