Stable zinc anode solid electrolyte interphase via inner Helmholtz plane engineering

Abstract

The inner Helmholtz plane and thus derived solid-electrolyte interphase (SEI) are crucial interfacial structure to determine the electrochemical stability of Zn-ion battery (ZIB). In this work, we demonstrate that introducing β-cyclodextrins (CD) as anion-receptors into Zn(OTf)₂ aqueous electrolyte could significantly optimize the Zn anode SEI structure for achieving stable ZIB. Specifically, β-CD with macrocyclic structure holds appropriate cavity size and charge distribution to encase OTf^- anions at the Zn metal surface to form β-CD@OTf^- dominated inner Helmholtz structure. Meanwhile, the electrochemically triggered β-CD@OTf^- decomposition could in situ convert to the organic-inorganic hybrid SEI (ZnF₂/ZnCO₃/ZnS‒(C-O-C/^*CF/^*CF₃)), which could efficiently hinder the Zn dendrite growth with maintain the proper SEI mechanical strength stability to guarantee the long-term stability. The thus-derived Zn | |Zn pouch cell (21 cm² size) with β-CD-containing electrolyte exhibits a cumulative capacity of 6450 mAh^-2 cm^-2 at conditions of 10 mAh cm^-2 high areal capacity. This work gives insights for reaching stable ZIB via electrolyte additive triggered SEI structure regulation.