ANALYSIS OF ACTIVE MATERIAL AND ADDITIVE DISTRIBUTIONS IN A NICKEL-HYDROXIDE ELECTRODE BY SEM EDX TECHNIQUES

Cobalt and cadmium additive distributions in the active material acros s the thickness of a nickel electrode were determined by using scannin g electron microscopy and energy dispersive X-ray analysis techniques. The nickel oxide/hydroxide active material is impregnated in small po res (10 to 15 mum) of the nickel substrate of the electrode. To avoid possible interference by the nickel metal substrate, the additives and ionic nickel were analyzed interference by the nickel metal substrate , the additives and ionic nickel were analyzed on micro-spots in the a ctive material on a cross section of the electrode. The atomic ratio o f nickel to oxygen at each analytical point was used to confirm that t he analyses were carried out at spots constituting pure active materia ls only, without any contamination from the nickel substrate/metal. Re sults showed that cobalt and cadmium additives were more concentrated at the surface than the bulk for electrodes prepared by the electroche mical impregnation technique. Trends in the distributions of the indiv idual elements (additives) did not change after cycling of the electro des (up to about 50 cycles) in flooded cell configurations.