A STUDY OF THE ELECTROCHEMISTRY OF NICKEL-HYDROXIDE ELECTRODES WITH VARIOUS ADDITIVES

Nickel composite electrodes (NCE) with various additives are prepared by a chemical impregnation method from nitrate solutions on sintered p orous plaques. The electrochemical properties, such as utilization of active material, swelling and the discharge potential of the nickel ox ide electrode (NOE) are determined mainly through the composition of t he active material and the characteristics of nickel plaques. Most add itives (Mg, Ca, Sr, Ba, Zn, Cd, Co, Li and Al hydroxide) exert effects on the discharge potential and swelling of the NOE. Chemical co-preci pitation with the addition of calcium, zinc, magnesium and barium hydr oxide increases the discharge potential by more than 20 mV, but that w ith zinc hydroxide results in an obvious decrease of active-material u tilization and that with calcium and magnesium hydroxide produces a la rger increase of electrode thickness. The effects of anion additives a re also examined. Less than 1% mol of NiS in the active material incre ases the discharge potential, Cadmium, cobalt and zinc hydroxide are e xcellent additives for preventing swelling of the NCE. Slow voltammetr y (0.2 mV s(-1)) in 6 M KOH is applied to characterize the oxygen-evol ving potential of the NCE. The difference between the oxygen-evolution potential and the potential of the oxidation peak for the NCE with ad ditives of calcium, lithium, barium and aluminium hydroxide is at leas t + 60 mV.