Effect of AB5 alloy on Ti0.10Zr0.15V0.35Cr0.10Ni0.30 hydrogen storage alloy

Abstract

The structure and electrochemical characteristics of melted composite Ti 0.10 Zr 0.15 V 0.35 Cr 0.10 Ni 0.30 ? x% LaNi 4 Al 0.4 Mn 0.3 Co 0.3 (x = 0, 1, 5) hydrogen storage alloys have been investigated systematically. XRD shows that though the main phase of the matrix alloy remains unchanged after LaNi 4 Al 0.4 Mn 0.3 Co 0.3 alloy is added, a new specimen is formed. The amount of the new specimen increases with increasing x. SEM-EDS analysis indicates that the V-based solid solution phase is mainly composed of V, Cr and Ni; C14 Laves phase is mainly composed of Ni, Zr and V; the new specimen containing La is mainly composed of Zr, V and Ni. The electrochemical measurements suggest that the activation performance, the low temperature discharge ability, the high rate discharge ability and the cyclic stability of composite alloy electrodes increase greatly with the growth of x. The HRD is controlled by the charge-transfer reaction of hydrogen and the hydrogen diffusion in the bulk of the alloy under the present experimental conditions. Keywords Composite alloy Á Hydrogen storage alloys Á V-based solid solution alloy Á Metal hydride electrode Á Electrochemical characteristicsList of symbols XRD X-ray diffraction SEM Scanning electron microscopy EDS Energy-dispersive spectrometer C max Maximum discharge capacity (mAh g -1 ) C n Discharge capacity at cycle number n (mAh g -1 ) S n Capacity retention at cycle number n C T Discharge capacity at certain temperature (mAh g -1 ) C 303 Discharge capacity at 303 K (mAh g -1 ) LTD Low temperature discharge ability HTD High temperature discharge ability HRD High-rate dischargeability C i Discharge capacity at different discharge rate (mAh g -1 ) C 60 Discharge capacity at both the charge/discharge current density of 60 mA g -1 (mAh g -1 ) DOD Depth of discharge (%) EIS Electrochemical impedance spectroscopy R ct Charge-transfer resistance (mX) I 0 Exchange current density (mA g -1 ) R Gas constant (J mol -1 K -1 ) T Absolute temperature (K) FFaraday constant (C mol -1 ) D Hydrogen diffusion coefficient (cm 2 s -1 )