Influence of temperature on electrochemical performances of rare earth based hydrogen storage material

In view of the higher temperature of large-size Ni/MH battery in electric vehicle, the effect of temperature on electrochemical performances of hydrogen storage alloy Ml(NiCoMnTi)5 was investigated systematically. The results show that the electrochemical performances of alloy vary drastically with temperature changing. As temperature rises, the hydrogen equilibrium pressure increases, the width of hydrogen desorption plateau decreases and the gradient increases, leading to a decline of capacity. When temperature rises from 20°C to 80°C, the discharge capacity of the alloy decreases from 309.11 mA · h · g-1 to 227.64 mA · h · g-1, but the high rate dischargeability is improved markedly. Higher temperatures also bring about a significant decrease in the cycling stability and self-discharge property. X-ray diffraction analysis indicates that the alloy has a single phase with CaCu5-type LaNi5 structure.