A Planar Zebra Battery Based on Low Cost Intermediate-Temperature Na-FeCl2 Redox Chemistry

A novel intermediate-temperature (IT) planar ZEBRA battery using a molten sodium anode and Fe cathode has been demonstrated in this work.  Because of unique sulfur-based additives in the cathode, this Na-FeCl₂ battery was able to be assembled in the discharged state and then activated at intermediate-temperature (<200°C).  Initial testing of the battery shows excellent cycling capability with superior energy density (discharge) of 135 Wh/kg (60% depth of discharge) and high energy efficiency exceeding 92% at an intermediate operating temperature of 190°C.  The long term cell cycle tests of IT planar Na-FeCl₂ battery show a minimal capacity fade and well-defined charge-discharge profiles. Our results demonstrate that the IT planar Na-FeCl₂ battery technology developed could be a promising alternative to the traditional Na-NiCl₂ chemistry by substantially lowering the material cost, thus helping to deploy ZEBRA battery technologies in stationary energy-storage and micro-grid applications.