The development of Zn–air batteries with a high energy density of 1350 W h kg−1 is one of the breakthroughs required to achieve a low carbon society.

The Influence of alkyl chain length in quaternary ammonium cations on electrochemical Zn growth morphology in alkaline-based electrolytes was systematically investigated under constant current density. Mossy structures that typically developed at low current density were mitigated in an electrolyte with 1 mM octyltrimethylammonium chloride. By changing from octyl to decyl group in the surfactant, completely smooth deposition morphology was achieved.Electrochemical impedance spectroscopic analysis revealed that charge transfer resistance associated with Zn deposition increased with alkyl chain length. The obtained results indicate that bulky ammonium cations suppress excess electrodeposition due to the steric hindrance effect and thereby result in smooth morphology.