Tailoring Interfacial Dynamic Adsorption to Achieve Highly-Reversible Zinc Metal Batteries with Zwitterion Additives

Abstract

Aqueous zinc metal batteries are promising for grid energy storage; however, their application is hindered by the irreversibility of Zn chemistry. Electrolyte additives have demonstrated effective in improving Coulombic efficiency (CE), yet the incomplete understanding of the interplay between additives and Zn metal anode (ZMA) is an obstacle to advancing electrolytes. Herein, we propose and validate a molecular design strategy based on two critical factors, dipole moment and isotropic polarizability, which characterize the dynamic nature of additive molecules at the charged interface between ZMA and electrolyte. This design guideline inspires an exemplar molecule, choline glycerophosphate (GPC), to be used as an additive in aqueous ZnCl2electrolyte. The ZnCl2+GPC electrolyte achieves a high CE of 99.9% for Zn plating/stripping. The comprehensive analysis of ZMA/electrolyte interface reveals a dynamic interplay mode that is responsible for the excellent reversibility. The high dipole moment and isotropic polarizability of GPC enable it to adsorb on ZMA surface during both charge and discharge processes, while the water reduction is greatly inhibited. The application of ZnCl2+GPC electrolyte is demonstrated in Zn||NH4V4O10 cells at room and sub-zero temperatures. This molecular engineering strategy facilitates the ration design of electrolytes and can be extended to other aggressive alkali-metal batteries.

Keywords: zinc metal, dipole moment, isotropic polarizability, dynamic interplay mode, solid electrolyte interphase