Effect of high and low temperature on the electrochemical performance of LaNi_4.4?xCo_0.3Mn_0.3Al_x hydrogen storage alloys

详细信息    查看全文

• 作者：Muhammad-Sadeeq Balogun ; Zhongmin Wang ; Huaigang Zhang ; Qingrong Yao ; Jianqiu Deng ; Huaiying Zhou
• 关键词：Electrochemical measurements ; LaNi4.4&minus ; xCo0.3Mn0.3Alx ; Hydrogen storage alloy ; High and low temperature ; High-rate dischargeability (HRD)
• 刊名：Journal of Alloys and Compounds
• 出版年：2013
• 出版时间：5 December, 2013
• 年：2013
• 卷：579
• 期：Complete
• 页码：438-443
• 全文大小：1759 K

文摘

Different electrochemical measurements such as activation and maximum capacity, cyclic stability, self-discharge property, high-rate dischargeability and electrochemical impedance spectroscopy have been carried out to investigate the electrochemical performances of LaNi_4.4?xCo_0.3Mn_0.3Al_x hydrogen storage alloys at low and high temperatures. We have selected 273 K and 323 K as low and high temperatures respectively. Samples W, X, Y and Z were used to represent alloys LaNi_4.4Co_0.3Mn_0.3, LaNi_4.3Co_0.3Mn_0.3Al_0.1, LaNi_4.2Co_0.3Mn_0.3Al_0.2 and LaNi_4.1Co_0.3Mn_0.3Al_0.3. XRD patterns show the alloys are all single-phase alloys with hexagonal CaCu5 type structure. The highest maximum discharge capacity is 340.3 mA h/g for alloy X, which is higher than other alloys at same temperature and high temperature. After 50 charge/discharge cycles, capacity retention of 93.6 % has been observed at low temperature for alloy Z. The least capacity loss was 13.3 % at 273 K during the self-discharge test. At both studied temperatures, alloy Z has the highest high-rate dischargeability (HRD) of 56.6 % and 44.9 % respectively at a discharge current density of 1800 mA/g. The electrochemical impedance spectroscopy (EIS) analysis was carried out to determine the charge-transfer resistance (R_ct) which was further used in the analysis of the HRD. Alloy Z with the highest HRD at 273 K has a lower R_ct of 0.9272 m¦¸ due to the dissolution or presence of Al into the electrolyte which can effectively reduce the total resistance of alloys. Apparently, at the two different testing temperatures, all the alloys possess better electrochemical properties at 273 K than 323 K.