Effects of rapid quenching on structure and cycle stability of La-Mg-Ni-Co type hydrogen storage alloy

In order to improve the cycle stability of La-Mg-Ni-Co type alloy electrode, rapid quenching technology was employed. The effects of rapid quenching on the microstructure and cycle stability of the alloy were investigated. The obtained results show that the La2Mg(Ni0.85Co0.15)9M0.1(M = B, Cr) alloy electrodes are composed of (La, Mg)Ni3 phase, LaNi5 phase and a small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast MB alloy, and the Ni2B phase in the alloy nearly disappears after rapid quenching. Rapid quenching technology can slightly improve the cycling life of the alloy. When the quenching rate increases from 0 m·s−1 (As-cast is defined as quenching rate of 0 m·s−1) to 30 m·s−1, the cycle lives of the MB, MCr alloys enhance from 86 and 87 cycles to 106 and 119 cycles, respectively. On the other hand, the average capacity decay rates of the MB, Mcr alloys decrease from 1.7172 and 1.7178 mAh·g−1 cycle−1 to 1.5751 and 1.3060 mAh·g−1·cycle−1 after 86 charge-discharges cycling, respectively.