Projecting the Specific Energy of Rechargeable Zinc–Air Batteries

Commercial primary zinc–air batteries provide 450 Wh kgcell–1 (at the cell level), but the practical specific energy of secondary zinc–air batteries remains unclear. Using a specific-energy model and data from reported zinc–air cells, we show that some rechargeable zinc–air electrode materials may already be capable of enabling system-level specific energies between 200 and 450 Wh kgsys–1. These values rival best-case projections for battery packs using lithium–sulfur, lithium metal paired with layered metal oxides, or open lithium–air. By performing a sensitivity analysis on the reported specific-energy model, we show that depth of discharge, areal discharge capacity, and solid-volume fraction of the porous Zn electrode are the most important parameters for increasing specific energy, rather than discharge voltage. To achieve a high specific energy, bipolar zinc–air cells need to cycle above 40% depth of discharge with areal discharge energies >100 mWh cmgeo–2.