Regulating the Electrical Double Layer with Supramolecular Cyclodextrin Anions for Dendrite-Free Zinc Electrodeposition.

Abstract

The interfacial stability of a Zn battery is dependent on the electrical double layer (EDL) that forms at the interface between the electrolyte and the Zn metal anode. A fundamental understanding of the regulation of the EDL structure and stability on the Zn surface is highly desirable for practical applications of aqueous batteries. Herein, the interfacial chemistry of the EDL is regulated by the adsorption of supramolecular cyclodextrin anions in the inner Helmholtz plane (IHP). The nucleation overpotential and the charge transfer activation energy for Zn2+ to go through the OHP (Ea1) and IHP (Ea2) are increased, leading to slower Zn2+ transfer kinetics. The electric field distribution and Zn2+ flux in the proximity of the Zn metal surface are homogenized, thus suppressing the growth of dendrites. The mechanism is supported with theoretical and experimental analyses. Consequently, a Zn||Zn symmetric cell achieves an ultrahigh cumulative capacity of 10000 and 4250 mAh cm-2 at a respective current density of 10 and 50 mA cm-2, and an average Coulombic efficiency of 99.5% over 1000 cycles under harsh conditions (at a high current density of 10 mA cm-2 with a high capacity of 10 mAh cm-2). This work provides insight into the introduction of supramolecular anions to regulate the electrical double layer EDL structure and improve the interfacial stability.