Structural evolution and electrochemical hydrogenation behavior of Ti₂Ni alloy

The structure, morphology, and electrochemical hydrogenation behavior of Ti₂Ni alloy, prepared by an induction melting method, have been systematically investigated. The results of X-ray diffraction showed that hydrogen absorption led to a significant inelastic lattice expansion of the alloy. The alloy had a maximum discharge capacity of 235.5 mAh/g at a current density of 60 mA/g and a high rate dischargeability of 73.3% at 300 mA/g. The increase in the electrolyte temperature induced a decrease in discharge capacity, a decay of cycle life, an increase and subsequently a decrease in exchange current density, and an enhancement of hydrogen diffusion. Moreover, the alloy with a smaller particle size showed a higher discharge capacity. The mechanism for the capacity loss of the alloy during charge and discharge cycling was studied. The apparent activation energy for hydrogen diffusion within the bulk alloy was 10.7 kJ/mol.