New models in the nickel hydroxide electrode: from the real material structure to the second discharge plateau

摘要

The X-ray diffraction spectrum of an electrochemically active nickel hydroxide has been simulated by the DIFFaX program, which evidences the presence of two types of stacking faults, providing a very good match of the abnormal width of the (10l)diffraction lines. The empirical correlation between such an abnormal width and a good electrochemical activity could thus be rationalized, since the presence of stacking faults should facilitate the transformation into theγ phase, and lead to anincrease in conductivity in the reduced state.Besides, a new model is described, which explains the second plateau that occurs during the discharge of the nickel hydroxide electrode. Contrary to other models, ours is based on the existence of a well-defined composition, very close to Ni(OH){sub}2.The length of the first plateau is controlled by the appearance of this phase, which is indeed governed by kinetics.It is suggested that the presence of stacking faults should delay the appearance of the second plateau.