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

摘要:

为了改善La-Mg-Ni系A2B7型电极合金的电化学循环稳定性，用Pr部分替代合金中的La，并用熔体快淬工艺制备了La0.75-xPrxMg0.25Ni3.2Co0.2Al0.1 (x = 0, 0.1, 0.2, 0.3, 0.4)电极合金。用XRD、SEM、TEM分析了铸态及快淬态合金的微观结构。结果表明，铸态及快淬态合金均具有多相结构，包括2个主相(La,Mg)Ni3及LaNi5和1个残余相LaNi2。熔体快淬导致LaNi5相增加而(La,Mg)Ni3相减少。电化学测试结果表明，熔体快淬显著地提高合金的电化学循环稳定性。当淬速从0 m/s (铸态被定义为淬速0 m/s)增加到20 m/s时，x=0合金100次充放循环后的容量保持率从65.32%增加到73.97%，x=0.4合金的容量保持率从79.36%增加到93.08%。

Abstract:

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.