Microstructure and high-temperature electrochemical characteristics of Zr0.9Ti0.1Ni1.0Mn0.7V0.3Six (x = 0.05, 0.10, 0.15, 0.20) alloy

The crystal structure, the phase composition and electrochemical characteristics of non-stoichiometric Zr0.9Ti0.1Ni1.0Mn0.7V0.3Six (x=0.05, 0.10, 0.15, 0.20) alloys under high temperature were investigated by means of XRD, SEM, EDS and electrochemical measurements. It was shown that Si addition greatly improved high-temperature electrochemical characteristics of the AB2 Laves phase alloys. At 338 K, the discharge capacity of Zr0.9Ti0.1Ni1.0Mn0.7V0.3Si0.10 alloy reached 249 mAh g−1, and the charge retention was 94.20% for 24 h, and the capacity retention for 300 charge/discharge cycles was 45.17%. The improvement in the high-temperature electrochemical characteristics of the alloy was attributed to the formation of the Zr-rich second phase in the matrix and the increasing stability of AB2-type Laves phase alloy hydride due to Si addition in alloy. They seem to be also related with the formation of a compact silicon oxide film on the alloy surface, which increases the corrosion resistance performance of the alloy in KOH solution. At high temperature, the main cause of further decreasing of alloy cycle stability may be due to the corrosion and the oxidising deteriorate on alloy surface, and the expansion ratio of crystal cell volume probably is not a critical effect on the cycle stability of alloy.