AbstractElectrochemical studies performed by linear potential scan voltamperometry on the monosubstituted intermetallic hydrides LaNi4.5M0.5, with M=AI, Mn or Co, confirm previous observations [ 14, 16, 20] of the influence of the nickel substitute on the rate of hydrogen insertion/desinsertion in solid gaz : the rate of discharge is faster for the Co and Mn substituted hydrides than for the Al one : during a controled discharge process by potential step of 20mV during 10 hours, hydrogen full capacity is desinserted over a potential range of 200mV in 80 hours for LaNi4.5AI0.5, over 130mV in 40 hours for LaNi4.5Mn0.5 and over 50mV in 30 hours for LaNi4.5Co0.5Coupled techniques of real time neutron diffraction and linear potential scan voltammetry applied to the in situ study of the charge/discharge of a LaNi4.5A10.5Dx electrode in a KOD 7N electrolyte gives account for the respective variation of the cell parameters of the α and β phases[ 11] and provides access to the hydogen desinsertion kinetics from both phases. The decrease rate of the unit cell volume of the α phase is found to be 4.8 10−3 A3/hour whereas that of the β phase is 61 10−3 A3/hour. At the end of the discharge process occurence of isolated 13ph ase domains is attributed to the faster rate of hydrogen desinsertion in the β phase than in the (β phase, which is in all likelihood at the origin of the loss of capacity observed during cycling for this electrode.