Structure and electrochemical properties of low-cobalt La_1-xLi_xNi_3.2 Co_0.3Al_0.3 (0≤x≤0.2) hydrogen storage electrode alloys

The structure and electrochemical properties of a new low cobalt hydrogen storage electrode alloys La_1-xLi_xNi_3.2 Co_0.3Al_0.3 (0≤x≤0.2) were investigated with a different additions of Li in replacement of La. With the increase of Li contents the maximum discharge capacity increases from 240 mAh·g^-1 (x = 0) to 328.4 mAh·g^-1 (x = 0.1) and the cycle stability is improved correspondingly. The capacity decay can remain 28.6% (x = 0.2) after 230 charge/discharge cycles. The high rate discharge (HRD) ability of the alloys (x≤0.1) is improved and the best HRD is 34.1% (x =0.1) under the discharge current density 1200 mA·g^-1. It is found that the prepared alloys are basically composed of LaNis as matrix phase and La-Ni₃ as second phase (x≤0.1). But the abundance of LaNi₃ phase dramatically decreases with increasing x. When x = 0.2, a new phase Al(NiCo)₃ is formed.