Effect of annealing on the structure and electrochemical properties of La_(1.8)Ti_(0.2)MgNi_(8.9)Al_(0.1) hydrogen storage alloy

摘要

La_(1.8)Ti_(0.2)MgNi_(8.9)Al_(0.1) alloys have been prepared by magnetic levitation melting followed by annealing treatment. The effects of annealing on the structure and electrochemical properties of the alloys are investigated by XRD, SEM-EDS and electrochemical measurement. For as-cast and annealed La_(1.8)Ti_(0.2)MgNi_(8.9)Al_(0.1) alloys, La(Ni,Al)s and LaMg_2Nig are the main phases. Annealing not only causes LaNi_2 phase to disappear, but also brings higher compositional homogeneity, which contributes to the improvement of cycling stability. At 60% discharge capacity retention, the maximum charge-discharge cycles, 160 cycles (at 900 ℃), is more than three times the minimum, 51 cycles (as-cast). The positive impact of annealing (at 800 ℃ and 900 ℃) on the charge transfer rate at the surface and the hydrogen diffusion rate in the bulk enhances the HRD. The optimum annealing temperature is found to be 900 ℃.