Influence of binding materials for shaping alloy electrodes on the performance of a Ni/metal hydride battery

Abstract

With increasing binder content in a metal hydride (MH) electrode the cycle number for activation became shorter, the rate capability was lowered and sheeting character was improved, showing that a most suitable binder content exists. The prepared MH electrode showed excellent durability with only 5% capacity decay after 1000 cycles at 100% depth of discharge. The discharge capability of the electrode was tested in various types of Ni-MH batteries to find that it greatly depended on the MH/Ni capacity ratio and the types of battery. Discharge capacity at the 5 C rate was 50% of the value at the 0.2 C rate for the non-stacked prismatic cell (0.35 A h), 80% for the cylindrical cell (0.9 A h) and 80% for the stacked prismatic cell (30 A h) with an MH/Ni capacity ratio of 2. Self-discharge was 15% after storage for 30 days at 20°C. Scale-up of the Ni-MH battery was conducted to get a performance almost comparable with that of the same type of Ni−Cd cell (30 A h).