Development of a nickel electrode having stable performance at various charge and discharge rates over a wide temperature range

Studies were made of improvements to be obtained in Ni electrodes by increasing charge acceptance and stabilising capacity at various charge and discharge rates over a wide temperature range. The charge acceptance of Ni electrodes is generally related to the oxygen evolution overvoltage: the addition of Co(OH) 2 to Ni(OH) 2 crystals has been found to lower the oxidation potential of Ni(OH) 2, while coating the electrode surface with Cd(OH) 2 has been found to increase the oxygen evolution potential. Capacity stabilization of Ni electrodes can be basically achieved by preventing the formation of a higher oxide, γ-NiOOH, and the addition of Cd(OH) 2 to Ni(OH) 2 crystals has been found to be effective for this purpose. Thus, a Ni electrode has been developed consisting of a solid-solution of Ni(OH) 2 and an adequate amount of Co(OH) 2 and Cd(OH) 2 and where the content of the latter is relatively high at the electrode surface. This electrode exhibits a stable capacity over wide operating conditions throughout cycling.