退火温度对La_3MgNi_(14)电极合金电化学行为的影响

Effect of annealing temperature on electrochemical behavior of the La_3MgNi_(14) electrode alloy

为了改善La3MgNi14合金的循环寿命,在0.3 MPa氩气气氛及1123、1223、1323 K温度下分别对合金进行了退火处理,处理时间为10 h,同时研究了退火温度对La3MgNi14电极合金的相结构、显微组织及电化学行为的影响。结果表明,退火温度影响合金的相结构,铸态及1123 K温度退火后合金包含LaNi5、(La,Mg)2Ni7主相和少量的LaNi2相,1223 K温度退火有利于合金中(La,Mg)Ni3相的形成,1323 K温度退火后合金主相为LaNi5和(La,Mg)Ni3相。退火后合金的显微组织比铸态合金更加均匀,晶粒尺寸增大。随着退火温度升高,合金的最大放电容量和循环寿命单调增加,高倍率放电性能、损耗角以及极限电流密度增大,充放电电位差和电荷迁移电阻减小。

In order to improve electrochemical performance of as-cast La3MgNi14alloy,the alloy was annealed at 1123,1223 and 1323 K under 0.3 MPa argon atmosphere for 10 hours.The effects of annealing temperature on phase structure,microstructure and electrochemical properties of the annealed alloy were investigated.The results show that annealing temperature influences phase structure of the alloy.The as-cast alloy and alloy annealed at 1123 K are composed of LaNi5,（La,Mg）2 Ni7 and a small amount of LaNi2 phases.（La,Mg）Ni3 phase forms in the alloy annealed at 1223 K.However,the alloy annealed at 1323 K mainly consists of LaNi5 and（La,Mg）Ni3 phases.Compared with the as-cast alloy,the microstructure of the annealed alloys is more homogeneous,and its grains are coarsened.With increasing annealing temperature,the maximum discharge capacity and cycling life of the alloy monotonously increase,and the high-rate discharge ability（HRD）,the loss angle and the limiting current density of the alloy all increase,however,the potential difference and charge-transfer reaction resistance of the alloy decrease.