The Forming Process in Nickel Positive Electrodes

Abstract

A detailed study has been made of the phases produced and their geometric distribution during formation of Edison-type tubular positive nickel electrodes. The initial charging in lithiated KOH electrolytes converts the Ni(OH)~ to a beta phase having a solid solution range for di-and tetravalent nickel. The beta crystalline structure is related to LiNiO2. This phase can be further oxidized to alpha phase, a tetravalent nickelate having appreciable trivalent nickel solid solubility. Alpha phase is most readily formed during Ni (OH)2 oxidation in concentrated KOH or NaOH electrolytes, but does not form in LiOH elec-trolytes. The addition of LiOH to the battery electrolyte contributes to alpha phase discharge and limits alpha phase reformation. The contribution of alpha phase to electrochemical capacity is limited by a low effective exchange current as compared to the beta phase.