Fabrication And Electrochemical Properties Of Ti-based Hydrogen Storagre Alloys

Titanium-based hydrogen storage alloys have good corrosion resistance and anti-chalking performance so that they are chosen as one of potential hydrogen storage alloys. It is well known that titanium-based nonequilibrium state hydrogen storage alloys have good discharge capacity in theory. But in many papers, they don’t show good electrochemical properties such as discharge capacity, cycling ability and electric charge conservation rate. Therefore, recent works are focusing on improving discharge capacity and cycling ability of titanium-based nonequilibrium state hydrogen storage alloys, which work as electrode material.In this paper, two kind of titanium-based hydrogen storage alloys were investigated as comparison. Ti50Ni15Cu25Sn5Zr5amorphous alloy was fabricated by suction cast and Ti45Zr38Ni17quasicrystal alloy was melt-spun directly. The microscopic structure and electrochemical characteristics of these two composites were then studied in this work by XRD, SEM, TEM and Land battery test system. Upon that, Ti45Zr38Ni17quasicrystal alloy was improved by Cu addition and heat treatment, which may bring good electrochemical properties. The conclusions sum up as followsX-ray diffraction analysis of Ti50Ni15Cu25Sn5Zr5amorphous alloy shows it consists of mainly amorphous structure, some crystal phase of Ti2Ni. During the charging/discharging test, Ti50Ni15Cu25Sn5Zr5alloy is fully activated at the5th cycle and its highest discharge capacity is24.3mAh/g. However, the plateau decreases quickly when discharging. The cycling stability is good.Ti45Zr38Ni17quasicrystal alloy has a fcc lattice. And the atomic accumulation type is Samson-Pauling-Bergmann diamond triacontahedron.Ti45Zr38Ni17quasicrystal alloy is fully activated at the33rd cycle and its highest discharge capacity is28.8mAh/g.With the increasing of Cu content, the microscopic structure is changing from icosahedral quasicrystalline phase (x=0,3)to nano icosahedral quasicrystalline phase and amorphous phase (x=5,7). Ti45Zr38Ni17+7wt.%Cu has amorphous phase and medium-range-order zone, which lead to the decreasing of vacancies where hydrogen atoms can exist. The maximum discharge capacity of the alloy electrodes decreases with increasing x value, and Ti45Zr38N17exhibits the highest discharge capacity of28.8mAh/g while Ti45Zr38Ni17+5wt.%Cu makes the worst value,22.05mAh/g.Ti45Zr38Ni17quasicrystal alloy is partly transformed into C14Laves phase and a-Ti(Zr) phase when the parameters of heat treatment are500℃and1hour. The difference is it changes completely at600℃and700℃. The electrochemical properties of double phases alloy are better than Ti45Zr38Ni17quasicrystal alloy’s. The highest discharge capacity increases from28.8mAh/g to60.9mAh/g(600℃). Because of phase decomposition, the numbers of both grain and grain boundary increase, that makes diffuse path of H increase. There are38figures,14tables and84references.