Effects of Heat Treatment on Electrochemical Properties of V_3TiNi_(0.56)Al_(0.2) Hydrogen Storage Alloy

The hydrogen storage alloy V3TiNi0.56Al0.2 was prepared by self-propagation at high temperature and its structure was characterized by X-ray diffraction.Its electrochemical properties including the activation property,maximum discharge capacity and high rate discharge ability were evaluated after annealed at 1173K and 1573K by model cell and cycling voltammetry.The results show that after annealing,the diffraction intensities for TiNi in the alloy are weaken with the structure distribution of the alloy being more even and the grains of the alloy being bigger.The charge and discharge cycling stability and the high rate discharge of the alloys are improved by annealing.The maximum discharging capacity of the annealed alloy is not lower than that of the as-cast alloy(350mAh/g),while their cycling stability is improved markedly.The hydrogen diffusion coefficient of the alloy is increased as the annealing temperature increasing.