Stacking faults in the structure of nickel hydroxide: a rationale of its high electrochemical activity

The usually observed broadening of some lines in the X-ray diffraction pattern of Ni(OH) 2 is shown to result from the presence of stacking faults leading to the existence of some fcc domains within the hexagonal compact oxygen packing. Simulation of the X-ray diffraction pattern with the DIFFaX program allowed us to propose a structural model and to estimate the amount of defects. The existence of these stacking faults explains in a very convenient way the relation between the line broadening and both the electrochemical behaviour and the presence of unexpected bands in the Raman spectra.