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

The structure and electrochemical properties of low cobalt AB 5 -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 240 mAh / g ( x = 0 ) to 328 mAh / g ( x = 0.1 ) and then decreases to 320 mAh / g ( x = 0.2 ) . The cycle stability is improved slightly and the electrochemical capacity can remain 71.4% ( x = 0.2 ) after 230 charge/discharge cycles. The alloy ( x ⩽ 0.1 ) showed the best rate discharge ability under the discharge current density of 1200 mA / g . It is found that as-prepared alloys are basically composed of LaNi 5 as the matrix phase and LaNi 3 as the second phase ( x ⩽ 0.1 ) . But the abundance of LaNi 3 phase dramatically decreases with increasing x . When x = 0.2 , a new phase having a chemical composition of Al ( NiCo ) 3 was observed.