After the 1st cycle, the Ni(OH)(2)/NiOOH-based Ni electrodes contg. 0.5-3% Ca(OH)(2) showed increasingly better charge acceptance, higher (by 20-40 mV) final charging potentials, and a higher charge/discharge efficiency. In the 0.5-2% Ca(OH)(2) electrodes, the mass specific capacity was 10% higher in the 1st charge/discharge cycle and 5% higher in the subsequent cycles.