ELECTROCHEMICAL-BEHAVIOR OF ALPHA-COBALTED NICKEL-HYDROXIDE ELECTRODES

Cobalt substituted alpha-nickel hydroxides obtained by precipitation techniques have been used as positive electrodes of Ni-Cd batteries. As these materials are indefinitely stable in KOH solution, the electrochemical cycling between alpha and gamma-phases allows up to 1.3 e- per (Ni + Co) atom to be reversibly exchanged at the C/5 rate. Nevertheless, during long-range cycling, a slow evolution from the gamma/alpha-couple to the beta(III)/beta(II) couple occurs. It has been assigned to a partial reduction of Co3+ ions to Co2+ ions at the end of the discharge process. The evolution of the number of exchanged electrons (NEE) versus the cobalt amount is discussed.