Copper nickel substitution type hydrogen storage alloys AB_5 impact
|School||Central South University|
|Keywords||Hydrogen storage alloy Phase structure Copper Heat treatment Electrochemical properties|
Based on the comprehensive review of domestic and foreign AB 5 -type rare earth based hydrogen storage alloys on the basis of research, to determine the MlNi 4.0-x Co 0.4 Mn 0.3 Al 0.3 Cu x -type hydrogen storage alloy as the research object. Using XRD, SEM and other analytical methods, and constant current discharge, electrochemical impedance, linear polarization, anodic polarization and potentiostatic electrochemical measurement techniques such as step, analyzing changes in the content of Cu alloy and heat treatment on the phase structure and electrochemical properties effect, revealing the alloy composition, structure and electrochemical properties of the relationship, and strive to develop a low-cost, long-lived rare earth based hydrogen storage alloys. This paper studied the substitution of Ni on Cu MlNi 4.0-x Co 0.4 Mn 0.3 Al 0.3 Cu x (x = 0.0,0.1,0.2,0.3,0.4) alloy phase structure and electrochemical properties, studies show: All alloy hexagonal crystal structure are LaNi 5 structure, with the the Cu content increases, c / a axial ratio increases, the unit cell parameters and cell volume increases gradually absorbing alloy electrode platform with the Cu content increases gradually. As the content of Cu increases, the maximum discharge capacity of the electrode alloy decreased gradually, from x = 0 the 330.6 mAh / g and gradually decreased to x = 0.4 the 290.7mAh / g. However, the cyclic properties of alloy with the increase of the Cu content was significantly increased after 100 charge-discharge cycles, when x = 0.4 when the capacity retention rate of 86.5%. Tests show that Cu can be reduced by adding alloy hardness, resulting in improved stability of the cyclic alloy. The high rate of the alloy electrode discharge capacity of the electrochemical reaction resistance, the exchange current density, maximum current density studies showed that with the increase of the Cu content, the high rate performance decreases, the electrochemical reaction resistance gradually increases the current density and the limit switch the current density decreases. Effect of heat treatment (t = 4.5 h, T = 1123 K) for MlNi 4.0-x Co 0.4 Mn 0.3 Al 0.3 < / sub> Cu x (x = 0.0,0.1,0.2,0.3,0.4) alloy electrochemical overall performance were investigated. The results show that with the increase of the copper content, PCT curve platform increased. Compared with the untreated alloy, heat treatment may reduce the hydrogen absorption alloy PCT curve platform, reducing the inclination of the platform to flatten. After heat treatment, the maximum discharge capacity of the alloy electrodes decreased activation performance. When x = 0.4 when, C max = 282.6 mAh / g. However, heat treatment significantly improves the stability of the cyclic alloy, the capacity retention rate with the increase of the Cu content, the cycle efficiency is much higher than the untreated alloy. After 100 charge-discharge cycles, when x = 0.4 when the capacity retention rate R 100 = 94.3%.