Effect of dehydrogenation depth on cyclic hydrogen desorption properties of V40Ti25.5Cr26.5Fe8 alloy.

The cyclic stability of hydrogen absorption and desorption is an important indicator of hydrogen storage alloy. The decay mechanism was roundly investigated by controlling the depth of dehydrogenation (DOD) of the V 40 Ti 25.5 Cr 26.5 Fe 8 alloy during the process of hydrogen ab/desorption cycles. The V 40 Ti 25.5 Cr 26.5 Fe 8 alloy exhibits the hydrogen desorption capacity of 2.36 wt% at 323 K in the first cycle. After 30 cycles, the decay rate of the hydrogen desorption capacity is only 4.37 % at 40 % DOD, but rises to 8.74 % at 100 % DOD. The hydrogen desorption capacity (C), plateau pressure (P) and micro-strains (S) all show an "acceleration followed by slowing" exponential variation trend with the increase of cycle number (x). Additionally, any two of C , P and S show linear correlation. It is considered that the micro-strains in the crystal lattice is the main factor for the decay of the hydrogen desorption capacity and the plateau pressure. On the premise of ensuring the valid hydrogen storage capacity to meet the requirements of the application, properly reducing DOD per cycle can effectively reduce the micro-strains accumulation and cell volume expansion, thus improving the cyclic stability of the alloy. Moreover, the application of this alloy in a fuel cell bicycle was investigated, and the total range and mileage per unit weight of the alloy are up to 100.8 km and 15.7 km/kg, respectively. Compared with the lead-acid battery, lithium-ion battery and LaNi 5 -based hydrogen fuel cell, the V-Ti-Cr-Fe-based fuel cell shows significant advantages. ● A bran-new method was proposed to slow down the decay of the dehydrogenation capacity of the V 40 Ti 25.5 Cr 26.5 Fe 8 alloy. ● The alloy decay rate of the dehydrogenation capacity is only 4.37% after 30 cycles at 40% DOD, only half that at 100% DOD. ● Six functions were proposed to explain the influences of the micro-strains in the lattice. ● This alloy fuel cell shows significant advantages compared with other batteries through application in a fuel cell bicycle. [ABSTRACT FROM AUTHOR]