Boosting the Ionic Conductivity of Non‐Aqueous Proton Electrolyte for Hybrid Capacitors

Abstract

Proton batteries have emerged as promising alternatives for energy storage owing to their rapid H⁺ transport kinetics and environmental sustainability. However, state‐of‐art proton batteries using aqueous acid electrolytes suffer from severe hydrogen evolution, electrode dissolution, and narrow electrochemical windows. Non‐aqueous electrolytes could obviate these challenges, while they are typically limited by low ionic conductivity. In this work, a hydrogen‐bond‐mediated proton transport mechanism is revealed in the phosphoric acid/ethyl acetate (H3PO4/EA) electrolytes with various concentrations. The optimized non‐aqueous H3PO4/EA electrolyte (80 m) simultaneously achieves high ionic conductivity (21.8 mS cm−1), wide electrochemical stability window (2.5 V), wide operational temperature range (−80 to 200 °C), and minimal corrosiveness. Using this electrolyte, the MoO3//AC hybrid capacitor demonstrates ultrahigh power density (13292 W kg−1), extended cycling stability (10 000 cycles), and unprecedented temperature adaptability (−50 to 60 °C). Our findings provide fundamental insights into non‐aqueous proton conduction mechanisms and establish new design principles for practical proton energy storage systems.