Ti-V-Cr-Ni alloys as high capacity negative electrode active materials for use in nickel-metal hydride batteries

TiV2.1-xCrxNi0.3 (x = 0.1-0.6 and 1.0), TiyV1.7Cr0.4Ni0.3 (y = 0.9-1.1) and TiV1.7Cr0.4Niz (z = 0.3-0.5) alloys were prepared by arc-melting, and their negative electrode properties such as the maximum discharge capacity (C-dis), charge-discharge cycle performance and high-rate dischargeability (HRD) were evaluated. All the alloys consisted of two phases. The V and Cr constituents were mainly distributed in the primary phase, whereas the Ti and Ni constituents were mainly distributed in the secondary phase. The C-max was dependent on the lattice volume of the primary phase, mole fraction of the primary phase and the plateau potential in charging. The average decrement of discharge capacity (Delta C-dis) from C-max to the discharge capacity at 30th cycle was used as an indicator of charge-discharge cycle performance. The Delta C-dis was decreased or cycle performance was improved with the Cr content in the primary phase. The discharge potential at DOD = 50% (Delta E-50) was linearly changed with specific discharge current (i(dis)), and the Delta E-50/Delta i(dis) and charge transfer resistance (R-ct) as indicators of HRD were decreased with an increase in the Ni content in the secondary phase. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.