Abstract. LaNi4,3–xCoxMn0,4Al0,3 materials (x=0, 0.25, 0.5, 0.75, 1.0) were prepared and examined using XRD technique. Ingot electrodes were formed from these materials for electrochemical studies, namely cyclic voltammetry with different scanning rates n (mV/s). A determination of surface capacity QS of the ingot electrodes was carried out with an extrapolation to infinite scan rate, taking into account the polarisation direction as charging or discharging. The thickness of superficial active layer dS was calculated from QS values. Based on the variation of QS and dS according to variation of Co ratio x, it is found that there are two suitable Co ratios corresponding to two opposite processes: charging and discharging.