Electrochemistry of the Layered Manganese Dioxides: A-xMn_(1-y)(Co,Ni,Fe)_yO_2 (A = Li, K) Rate Effects

摘要

Cobalt, iron, and nickel can be doped into the layered alkali manganese dioxides, A_xMn_(1-y)M_yO_2 for A = K, Na, or Li and M = Co, Fe, or Ni, during the hydrothermal synthesis from the alkali permanganates. A single phase is obtained. The transition metal doping enhanced the electrochemical behavior in lithium cells. The manganese phases formed during cycling appear to depend on the rate of reaction; a spinel-like phase was formed at 1 mA/cm~2 whereas the layered phase is maintained at 0.1 mA/cm~2 independent of whether potassium or lithium ions reside between the MnO_2 layers of the structure. Polarization is significantly less in the spinel-like regime.