Structure and electrochemical hydrogen storage properties of Ti2Ni alloy synthesized by ball milling

Abstract

The structure and the electrochemical hydrogen storage properties of amorphous Ti2Ni alloy synthesized by ball milling and used as an anode in nickel–metal hydride batteries were studied. Nominal Ti2Ni was synthesized under argon atmosphere at room temperature using a planetary high-energy ball mill. The structural and morphological characterization of the amorphous Ti2Ni alloy is carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical characterization of the Ti2Ni electrodes is carried out by the galvanostatic charging and discharging, the constant potential discharge, the open circuit potential and the potentiodynamic polarization techniques.The Ti2Ni alloy activation requires only one cycle of charge and discharge, regardless of the temperature.The electrochemical discharge capacity of the Ti2Ni alloy, during the first eight cycles, and at a temperature of 30°C, remained practically unchanged and a good held cycling is observed. By increasing the temperature, the electrochemical discharge capacity loss after eight cycles undergoes an increase and it is more pronounced for the temperature 60°C.At 30°C, the anodic corrosion current density is 1mAcm−2 and then it undergoes a rapid drop, remaining substantially constant (0.06mAcm−2) in the range 40–60°C, before undergoing a slight increase to 70°C (0.3mAcm−2). This variation is in good agreement with the maximum electrochemical discharge capacity values found for the different temperatures.By increasing the temperature, the difference between the OCP curves corresponding to C/10 and C/30 regimes undergoes significant growth, reaching a maximum value (ΔEOCV=10.3mV) at 60°C before undergoing a decrease at 70°C.A good correlation is found between the evolutions of the corrosion current density with the maximum discharge capacity on one hand and on the other hand with the ΔEOCV, according to the temperature. The effect of temperature on the different electrochemical parameters (Icorr, Cmax, ΔEOCV) and the various correlations found between them allows us to optimize the performance of the battery and provide proper operation under the good experimental conditions.