The high-temperature performance of low-cost La[sbnd]Ni[sbnd]Fe based hydrogen storage alloys with Si substituting

Abstract

Various properties of La0.78Ce0.22Ni3.73Co0.30Mn0.30Al0.17Fe0.5−xSix (x = 0, 0.05, 0.075 and 0.1) hydrogen storage alloys at 20–80 °C have been investigated systematically. With the increase of Si content, the hydrogen storage capacity increases and the equilibrium pressure decreases, thus the improved thermodynamic stability of the metal hydrides makes the Si-containing alloys more suitable for working at higher temperatures. Appropriate addition of Si (x = 0–0.075) improves the anti-corrosion capability of the alloy, as a result, the temperature insensitivity, high-temperature dischargeability and high-temperature recoverability increase accordingly, particularly the cycling stability (S150) increases from 43.7% to 71.8%. In addition, the charge-transfer process is suppressed gradually by Si substituting (x = 0–0.075) at 20 °C, but gets promoted due to the improved surface catalytic ability when that at 60 °C, consequently the high-rate dischargeability and high-power delivery deteriorate at room temperature, but increase gradually at higher temperature. Therefore, an optimum alloy electrode is got when x = 0.075, the deterioration of x = 0.1 alloy on high-temperature performance is attributed to the appearance of the second A2B7 phase.