Can–Cathode Interface in Alkaline Zn ∕ Mno2 Batteries: Optimization of Can Plating Composition

Abstract

One of the prerequisites of efficient battery performance is maintenance of a good electrical contact between electrodes and current collectors. Can-to-cathode contact resistance (CTCR) of various plating compositions was evaluated on the bench using accelerated aging test. Composition of Ni(Co)-plated steel strips was characterized by X-ray photoelectron spectroscopy and correlated to contact resistance. The underlying cause behind the CTCR differences of various plating compositions was investigated by a combination of focused ion beam and transmission electron microscopy. High contact resistance of the plain carbon steel current collectors is reduced when the steel surface is electroplated with thin Ni and/or Co layers. Relatively high CTCR of Ni-rich surfaces is due to the formation of uniform, highly resistive NiOx films that grow on the can surface upon exposure to KOH and . Fe–Ni mixed compositions display CTCR minimum at ca. 70% Ni, 30% Fe content. Resistivity of Fe–Ni oxides is high but the oxide films are thinner. The presence of surface cobalt greatly reduces CTCR. CoOx and NiCoOx oxide are more conductive than oxides on Ni and Ni–Fe surfaces. Excess of iron on the surface is detrimental and leads to high CTCR values, even in the presence of cobalt.