A solvation-driven reevaluation of organic electrolytes for zinc batteries

Abstract

Zinc batteries promise low-cost energy storage for grids but are limited by poor negative electrode reversibility. Thermodynamically stable organic electrolytes can theoretically enhance said reversibility but present high raw material costs and sluggish electrochemical kinetics. Herein, we demonstrate that abandoning the state-of-the-art chemistries based on fluorinated zinc salts and specialty solvents for those based on ZnCl₂ and mass-produced organic solvents can simultaneously remedy both issues. The Zn²⁺ solvation structure of these electrolytes substantially reduces the Zn deposition overpotential relative to conventional organic systems and generates polyhedral Zn with preferential Zn(002) texturing. Optimized electrolytes based on ZnCl₂ and ethyl acetate (EA) demonstrate Coulombic efficiencies (CE) of >99.9% without any discernible losses during 24 hour calendar aging. Economic projections indicate that these systems present a more than 80% reduction in the levelized electrolyte cost relative to aqueous systems when 24 hours of corrosion losses are considered. Lastly, we demonstrate a hybrid Zn/Na full cell, in which the designed electrolyte is projected to contribute only 5.0% of the material cost. This work offers a route to scalable, low-cost organic electrolytes for Zn batteries.