Study on the surfaces of LaNiAl alloy modified by Cu plating and SiO2 coating

LaNiAl hydrogen storage alloys were prepared by arc melting method. The effects of annealing-treatment, Cu plating and SiO2 coating on the surfaces of annealing-treatment alloys were investigated. The results show the intensities of diffraction peaks increase after the alloy was annealed, revealing that the alloy was re crystallized and dendritic segregation was eliminated during the annealing process. the result that the surface compositions changed from the enrichment of La, Ni and Al to that of Si and O indicates that Si was coated on the powder surfaces in the form of SiO2. Electrochemical study indicates that the alloys treated show excellent performance. The discharge voltage increases and discharge curves become smooth. It is found that the annealed alloy coated with Cu shows the best performance with high discharge voltage and long discharge platform. The annealed alloy coated with SiO2 shows low discharge voltage, and longest discharge platform. The capacity losses of the alloys annealed, plating with Cu, and coated with SiO2 over 25 cycles are 7%, 4% and 5.5%, respectively. However, capacity loss of the alloys without modification is 21.8%.