【摘要】 为了改善La-Mg-Ni系合金电极的循环稳定性,对铸态合金La0.75Mg0.25Ni3.5Co0.2在0.3 MPa压力氩气保护下进行不同温度的退火(1123,1223和1323 K),保温时间均为10 h。系统研究了退火温度对合金的微观结构及电化学性能的影响。X射线衍射(XRD)和扫描电镜(SEM)研究结果表明,合金具有多相结构,当铸态及1123 K温度退火后合金主要由LaNi5,(La,Mg)2(Ni,Co)7相以及少量的LaNi2相组成。当退火温度为1223和1323 K时,合金中LaNi2相消失,合金主要由LaNi5,(La,Mg)2(Ni,Co)7及(La,Mg)(Ni,Co)3相组成。随退火温度提高,合金最大放电容量单调下降,但合金的循环稳定性得到改善。退火处理改善合金循环稳定性的原因在于退火后合金组织均匀,晶粒增大,在KOH电解质溶液中增强合金电极抗氧化腐蚀能力,抑制合金颗粒粉化。更多还原

【Abstract】 In order to improve the cyclic stability of La-Mg-Ni system,as-cast La0.75Mg0.25Ni3.5Co0.2 alloy was annealed at 1123,1223 and 1323 K for 10 h in 0.3 MPa argon.The microstructure and electrochemical performance of different annealed alloys were investigated systematically by X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS) and electrochemical experiments.The results obtained by XRD and SEM showed that the as-cast and annealed(1123 K) alloys had multiphase structure containing LaNi5,(La,Mg)2(Ni,Co)7 and few LaNi2 phases.When annealing temperatures approached to 1223 and 1323 K,LaNi2 phase disappeared.When alloys annealed at 1223 and 1323 K multiphase are composed of LaNi5,(La,Mg)2(Ni,Co)7 and(La,Mg)(Ni,Co)3 phases were obtained.With increasing annealing temperature,the maximum discharge capacity of the alloy decreased monotonously,but the cyclic stability was improved owing to structure homogeneity and grain growth after annealing,and the enhancement of anti-oxidation/corrosion ability as well as the suppression of pulverization during cycling in KOH electrolyte were enhan ced.更多还原