Raman spectral observation of a 'new phase' observed in nickel electrodes cycled to failure

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A 'new phase' is reported in nickel electrodes from NiH2 boilerplate cells which were cycled to failure in electrolyte of variable KOH concentration (21-36%). Raman spectra clearly show the presence of this phase, and these spectra have been used to estimate the amounts present on these electrodes. Ten of twelve electrodes examined contain this new phase. The cycle life at higher KOH concentrations (31 and 36%) was greatly reduced, and nickel electrodes from these cells exhibited extensive amounts of this new phase. The presence of this 'new phase' correlates with cell failure defined by low end of discharge voltages. It is proposed that the lowered capacity and failure of these electrodes was caused by loss of active mass and formation of a phase with reduced electrochemical activity. These results indicate that formation of this new phase is accelerated at higher KOH concentrations. © 1991.

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Journal of Power Sources