Abstract：The influences of different temperatures of annealing treatment on the phase structure and electrochemical properties of La4MgNi17. 5Co1. 5 hydrogen storage alloy were investigated. The XRD analysis reveals that the alloys consist of LaNi5 phase and La4MgNi19 phase. With the increase of the temperature of annealing, the cell volume and the abundance of La4MgNi19 phase increases. While the temperature is up to 1 173 K, the abundance of La4MgNi19 phase decreases and the Ni- riched phase appears. The electrochemical measurement shows that the maximum discharge capacity increases obviously when the temperature is up to 1 123 K. The high- rate discharge ability(HRD) and cyclic stability(S100) are also improved. But when the temperature is up to 1 173 K, the electrochemical properties above are all decreased. For example, Cmax and S100 are increased from (369. 66 mA·h/g, 59. 96%)(as- cast) to (375. 33 mA·h/g, 65. 52%)(1 123 K) and then decreased to (312. 44 mA·h/g, 62. 82%)(1 173 K). It is found that the increase of the temperatures of annealing treatment can improve the uniformity of the phase structure. But when the temperature increases further, it will increase the volatilization of Mg and lead to the decomposing of La4MgNi19 phase.
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2015, Vol. 22 
