Improved Cycle Stability of La0.75-xPrxMg0.25Ni3.2Co0.2Al0.1 (x=0-0.4) Electrode Alloys by Melt Spinning

In order to improve the electrochemical cycle stability of the La-Mg-Ni system A2B7-type electrode alloys, La in the alloy was partially substituted by Pr. The melt-spinning technology was used for preparing La0.75-xPrxMg0.25Ni3.2Co0.2Al0.1 (x = 0, 0.1, 0.2, 0.3, 0.4) electrode alloys. The microstructures of the as-cast and spun alloys were investigated by XRD, SEM and TEM. The results show that the as-cast and spun alloys have a multiphase structure, consisting of two main phases (La,Mg)Ni3 and LaNi5 as well as a residual phase LaNi2. The melt spinning leads to an obvious increase of the LaNi5 phase and a decrease of the (La,Mg)Ni3 phase in the alloys. The melt spinning significantly improves the cycle stability of the alloys. The capacity retaining rate at 100th charging and discharging cycle (S100) is enhanced from 65.32% to 73.97% for the x = 0 alloy and from 79.36% to 93.08% for the x = 0.4 alloy with increasing of spinning rate from 0 m/s (as-cast was defined as spinning rate of 0 m/s) to 20 m/s.