Enhancement of the electrochemical performance of CoB amorphous alloy through the addition of A2B7-type alloy

The CoB-xA(2)B(7) composites (x = 0-30 wt.%) were prepared by ball milling the powdery mixture of both pristine alloys. As negative electrodes in nickel-metal hydride (Ni/MH) rechargeable batteries, the CoB-xA(2)B(7) composites exhibit a superior electrochemical performance. It has a maximum discharge capacity (C-max) of up to 730 mAh/g and its high-rate dischargeability (HRD) is significantly increased to 82.5% for x = 30 wt.% at a discharge density of 900 mA/g. The capacity retention rate (C-100/C-max) is increased firstly from 37.1% (x = 0 wt.%) to 45.6% (x = 5 wt.%), then decreased to 42.4% (x = 30 wt.%). The anodic polarization (AP) and potential-step measurements indicate that the diffusion ability of hydrogen atoms in the composite electrodes is distinctly improved by doping with A(2)B(7)-type alloy. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.