Effect of small amounts of Li on microstructures and electrochemical properties of non-stoichiometric low-Co AB5AB5-type alloys

The structure and electrochemical properties of low cobalt AB5AB5-type hydrogen storage electrode alloys with a small amount of Li in the A site have been investigated. With the increase of Li contents, the discharge capacity increases firstly from 240mAh/g(x=0)(x=0) to 328mAh/g(x=0.1)(x=0.1) and then decreases to 320mAh/g(x=0.2)(x=0.2). The cycle stability is improved slightly and the electrochemical capacity can remain 71.4% (x=0.2)(x=0.2) after 230 charge/discharge cycles. The alloy (x⩽0.1)(x⩽0.1) showed the best rate discharge ability under the discharge current density of 1200mA/g. It is found that as-prepared alloys are basically composed of LaNi55 as the matrix phase and LaNi3LaNi3 as the second phase (x⩽0.1)(x⩽0.1). But the abundance of LaNi3LaNi3 phase dramatically decreases with increasing xx. When x=0.2x=0.2, a new phase having a chemical composition of Al(NiCo)3Al(NiCo)3 was observed.