  Aqueous zinc-air batteries (ZABs) are a low-cost, safe, and sustainable
technology for stationary energy storage. ZABs with pH-buffered near-neutral
electrolytes have the potential for longer lifetime compared to traditional
alkaline ZABs due to the slower absorption of carbonates at non-alkaline pH
values. However, existing near-neutral electrolytes often contain halide salts,
which are corrosive and threaten the precipitation of ZnO as the dominant
discharge product. This paper presents a method for designing halide-free
aqueous ZAB electrolytes using thermodynamic descriptors to computationally
screen components. The dynamic performance of a ZAB with one possible
halide-free aqueous electrolyte based on organic salts is simulated using an
advanced method of continuum modeling, and the results are validated by
experiments. XRD, SEM, and EDS measurements of Zn electrodes show that ZnO is
the dominant discharge product, and operando pH measurements confirm the
stability of the electrolyte pH during cell cycling. Long-term full cell
cycling tests are performed, and RRDE measurements elucidate the mechanism of
ORR and OER. Our analysis shows that aqueous electrolytes containing organic
salts could be a promising field of research for zinc-based batteries, due to
their Zn$^{2+}$ chelating and pH buffering properties. We discuss the remaining
challenges including the electrochemical stability of the electrolyte
components.
