Hydrated Eutectic Electrolytes with Ligand-Oriented Solvation Shells for Long-Cycling Zinc-Organic Batteries

Despite their intrinsic safety and cost-effectiveness, aqueous zinc (Zn)-organic batteries have been struggling with the rapid performance degradation arising from the poor reversibility of Zn anodes and the dissolution of cathodes. Here, we present a new aqueous eutectic electrolyte by coupling a hydrated Zn salt (Zn(ClO 4 ) 2 ·6H 2 O) exclusively with a neutral ligand (succinonitrile) to mitigate these issues. The unique aqua Zn 2+ solvates with a succinonitrile-assisted solvation shell enable an unusual Zn/Zn 2+ reversibility of 98.4% Coulombic efficiency along with smooth Zn deposition. Moreover, all water molecules contribute to the formation of the eutectic network, resulting in a delayed oxidation and suppressed solvating ability. When a quinone-based polymer material (38 wt % sulfur content) is utilized as a cathode, the Zn-organic battery with this aqueous eutectic electrolyte exhibits an unprecedented cyclability with a low capacity decay rate (0.004% per cycle over 3,500 cycles) and superior low-temperature performance.