Self-discharge of the nickel electrode in presence of hydrogen : II. Electrochemical approach

• Published in: Journal of the Electrochemical Society 1999-07, Vol.146 (7), p.2382-2386
• Main Authors: PRALONG, V, SAC EPEE, N, TAUNIER, S, BEAUDOIN, B, JAMIN, T, DELAHAYE-VIDAL, A, TARASCON, J-M
• Format: Article
• Language: English
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.1391945

The Ni/H sub 2 self-discharge kinetics were studied by means of Ni /H sub 2 cells equipped with a pressure sensor to determine the time-dependence of cell pressure. The cell pressure variation was found to depend strongly upon cell state of charge (e.g., whether the nickel oxyhydroxide was of beta - or gamma -type). For overcharged Ni/H sub 2 cells (e.g., having a mixture of beta - and gamma -NiOOH as the nickel electrode) two different rate processes were observed for the self-discharge rate as a function of time. For longer times the curve could be well fitted by assuming a single self-discharge mechanism corresponding to the direct reduction of beta (III) by hydrogen. In contrast, for shorter times the first part of the P(H sub 2 ) = f(t) experimental curve exhibited a higher tangential slope, suggesting most likely a combination of two self-discharge mechanisms, (i) the direct reduction of gamma -phase by hydrogen and (ii) electro-chemical reduction involving the catalytic oxidation of hydrogen at the sintered matrix.