Electrochemical characteristics of the ball-milled LaMg10-xTixNi2LaMg10-xTixNi2 alloys with Ni powders (x=1x=1 and 2)

The electrochemical hydrogen storage properties of the ball-milled LaMg10-xTixNi2LaMg10-xTixNi2 alloys with Ni powders (x=1x=1 and 2) were investigated. It was found that the first discharge capacity of the ball-milled LaMg9TiNi2+150wt% Ni composite was 909.5 mAh/g, but the value of the ball-milled LaMg8Ti2Ni2+150wt% Ni composite was only 750.2 mAh/g. By EIS analysis, it is shown that the existence of a small quantity of TiNi phase in LaMg9TiNi2LaMg9TiNi2 alloy increased the electro-catalytic activity and reduced the electrochemical reaction resistance. This probably played an important role in the increase of discharge capacity of the ball-milled LaMg9TiNi2–NiLaMg9TiNi2–Ni composite. The presence of LaMg2LaMg2 phase and excessive TiNi phase resulted in the lower discharge capacity of the ball-milled LaMg8Ti2Ni2–NiLaMg8Ti2Ni2–Ni composite. Besides the higher discharge capacity, the ball-milled LaMg9TiNi2–NiLaMg9TiNi2–Ni composite exhibited the better cycle performance. The main reason for the better cycle performance was analyzed by X-ray diffraction (XRD), electrochemical impedance spectra (EIS) and steady-state polarization (SSP) experiments. It is verified that the main reason is that the electrochemical reaction resistance of the ball-milled LaMg9TiNi2–NiLaMg9TiNi2–Ni composite is always lower than that of the ball-milled LaMg10Ni2–NiLaMg10Ni2–Ni composite because the former one contains a small quantity of TiNi phase which has high electro-catalytic activity.