Unlocking the effect of alkyl chain length and hydroxyl group of electrolyte additives enabling stabilization of zinc anodes

For the development of electrolyte additives as an effective strategy to boost the reversibility of Zn anodes, most researchers focus on the functional groups but overlook the crucial molecular structure. Herein, ethylene glycol (EG), erythritol (Eryt) and hexanehexol (Hex) featuring with different molecular length and varied amounts of hydroxyl groups were introduced into 2 M ZnSO 4 electrolyte system as additives. Based on the theoretical computations and experimental analysis, the differences of three additives in tailoring the Zn anode/electrolyte interface were studied at the molecular level. Among these additives, EG additive with short molecular length and less hydroxyl groups delivers suitable interfacial adsorption energy and slightly stronger than that of water molecule, which could stabilize the anode/electrolyte interface most effectively. Therefore, with the EG additive in ZnSO 4 electrolyte, the undesired Zn dendrite growth and parasitic reactions including hydrogen evolution reaction, corrosion and passivation are significantly limited during the Zn plating/stripping process. As a result, employing EG as the electrolyte additive could greatly extend the cycling stability of Zn/Zn, Zn/Cu and Zn/V 2 O 5 batteries. This work proposes a new insight toward the optimal molecular configuration of additive design for electrolyte engineering in high-performance aqueous Zn batteries.