Effects of boron addition on microstructures and electrochemical properties of (Ti_0.65Zr_0.35)_1.10 (V_0.5Mn_0.3Cr_0.4Ni_0.8) B_x hydrogen storage alloys

Microstructures and electrochemical properties of the as-cast (Ti_0.65Zr_0.35)_1.10 (V_0.5Mn_0.3Cr_0.4Ni_0.8) B_x (x=0, 0.01, 0.05, 0.1, 0.2) alloys were analyzed by X-ray diffraction, scanning electron microscope, X-ray energy dispersive spectrum and electrochemical testing. The results show that VB phase appeared in the as-cast alloys when boron was added. Claviform VB phase is not an absorption phase. With the increase of boron addition, the activation property, the cycle stability and the high rate discharging performance are improved, and the reversible discharge capacity is decreased. Analyses show that the claviform VB phase increases the diffusion channels of hydrogen ion in the alloys. Furthermore, it increases the phase interface, and decreases the grain stress in the process of charging and discharging in alloy electrodes. Reaction resistance of the alloy electrode is decreased with boron addition increasing, and the rate property and cycle stability are optimized obviously.