A low-cost intermediate temperature Fe/Graphite battery for grid-scale energy storage

Due to their compactness, storage/supply flexibility, modularity and factory manufacturability, batteries are excellent candidates for large scale energy storage applications . However, the widespread application of most batteries hitherto developed is hindered by their high cost. Here, an intermediate temperature molten salt battery is developed that emphatically resolves this issue by using all earth-abundant and cheap elements. Operated at 170 °C, the cell comprises of an Fe metal anode, NaCl saturated NaAlCl 4 electrolyte and an AlCl 4 − intercalated graphite cathode in the fully charged state. It has a capacity retention of 85% after nearly 10,000 cycles. After characterizing the anode, it was determined that the high reversibility of the Fe to FeCl 2 solid state transformation are responsible for the absence of dendritic growth on such a metal anode. Different electrode capacity matching strategies are discussed in the context of ensuring safe operation during overcharging. Finally, the overall material cost of the Fe/Graphite cell is estimated to be 33.9 $ kWh −1 , which can potentially meet the demands of the commercial energy storage market.