Metal-Free Eutectic Electrolyte with Weak Hydrogen Bonds for High-Rate and Ultra-Stable Ammonium-Ion Batteries.

As the need for sustainable battery chemistry grows, non-metallic ammonium ion (NH ) batteries are receiving considerable attention because of their unique properties, such as low cost, nontoxicity, and environmental sustainability. In this study, the solvation interactions between NH and solvents are elucidated and design principles for NH weakly solvated electrolytes are proposed. Given that hydrogen bond interactions dominate the solvation of NH and solvents, the strength of the solvent's electrostatic potential directly determines the strength of its solvating power. As a proof of concept, succinonitrile with relatively weak electronegativity is selected to construct a metal-free eutectic electrolyte (MEE). As expected, this MEE is able to significantly broaden the electrochemical stability window and reduce the solvent binding energy in the solvation shell, which leads to a lower desolvation energy barrier and a fast charge transfer process. As a result, the as-constructed NH -ion batteries exhibit superior reversible rate capability (energy density of 65 Wh kg at 600 W kg ) and unprecedent long-term cycling performance (retention of 90.2% after 1000 cycles at 1.0 A g ). The proposed methodology for constructing weakly hydrogen bonded electrolytes will provide guidelines for implementing high-rate and ultra-stable NH -based energy storage systems.