铸态及退火态La0.8-xNdxMg0.2Ni3.15Co0.2Al0.1Si0.05(x=0～0.4)合金的电化学贮氢性能

摘要

The La-Mg-Ni-based A2B7-type La0.8-xNdxMg0.2Ni3.15Co0.2Al0.15 (x=0,0.1,0.2,0.3,0.4) electrode alloys were prepared by casting and annealing.The influences of partial substitution of Nd for La on the structure and electrochemical performance of the as-cast and annealed alloys were investigated.It was found that the experimental alloys consist of two major phases,(La,Mg)2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure,as well as some residual phase LaNi3 and NdNi5.The discharge capacity and high rate discharge ability (HRD) of the as-cast and annealed alloys first increase and then decrease with Nd content growing.The as-cast and annealed alloys (x=0.3) yield the largest discharge capacities of 380.3 and 384.3 mA·h/g,respectively.The electrochemical cycle stability of the as-cast and annealed alloys markedly grows with Nd content rising.As the Nd content increase from 0 to 0.4.The capacity retaining rate (S100) at the 100th charging and discharging cycle increases from 64.98％ to 85.17％ for the as-cast alloy,and from 76.60％ to 96.84％ for the as-annealed alloy.%通过铸造及退火处理制备La-Mg-Ni基A2B7型La0.8-xNdxMg0.2Ni3.15Co0.2Al0.15 (x=0,0.1,0.2,0.3,0.4)电极合金,并研究Nd部分替代La对合金结构及电化学性能的影响.结果表明,所有合金样品的主相均为六方结构的Ce2Ni7型(La,Mg)2Ni7及六方结构的CaCu5型LaNi5,同时还有部分LaNi3和NdNi5残余相.铸态及退火态合金的放电容量及高倍率放电性能随着Nd含量的增加先增加后减小.当x=0.3时,铸态及退火态合金的放电容量达到最大值,分别为380.3 mA·h/g和384.3 mA·h/g.合金的电化学循环稳定性随着Nd含量的增加而持续增加.当Nd含量从0增加至0.4％时,铸态合金在第100次充放电循环时的容量保持率(S100)从64.98％增加至85.17％,而退火态合金的S100值从76.60％增加至96.84％.