Chemical and morphological analyses of zinc powders for alkaline batteries

Zinc powders containing Bi, In and either Mg or Al were analyzed to determine chemical and morphological differences. Morphology and chemistry may influence the reactivity of Zn powders in the basic environment found inside alkaline batteries. Increased reactivity leads to increased Zn corrosion, increased hydrogen gas evolution, and possibly leakage of the battery electrolyte. The surface chemistry of the powders was examined using Auger electron spectroscopy, X-ray photoelectron spectroscopy, and atomic absorption spectroscopy to check for surface ZnO. Powder chemistry was measured using an electron probe micro analyzer equipped with an energy dispersive X-ray analyzer. Inert gas fusion determined the bulk oxygen content. Morphology studies included powder sieving for size determination, examining loose powders with a scanning electron microscope (SEM), and determining surface areas via Brunauer, Emmet, and Teller (BET) analyses. SEM images showed differences in powder shapes and surface conditions between passed and failed powders. Powders exhibiting smooth surfaces and regular shapes were more likely to pass gas testing. However, pass/fail gas test results could not be correlated to powder chemistry, powder size, or surface area. Powder roughness and irregularity may indicate an increase in the number of active sites such as peaks and barbs versus particles with smooth surfaces.