Crystalline Hydrogen Enhanced Dual-Acid Quasi-Solid-State Proton Battery

Proton batteries are considered promising due to their high-power output, cost-effectiveness, and safety. However, they also face challenges such as low voltage, limited capacity, and poor cycle stability. To address these challenges, a dual-acid quasi-solid-state electrolyte (SSAE) is developed by combining H 2 SiO 3 with H 2 SO 4 . This electrolyte has the decomposition voltage of 2.15 V and ultra-high conductivity of 95 mS cm⁻¹ (1.5 mS cm⁻¹ at −70 °C). Leveraging this high decomposition voltage, the specific capacity of MoO 3 is successfully enhanced to 1.74 times than its original value at a current density of 5 A g −1 by harnessing the hydrogen evolution/oxidation reaction (HER/HOR) of lattice hydrogen (H· ad,s ) in MoO 3 at low potentials, which is typically regarded as a significant factor to suppress the gas evolution. Notably, the voltage achieved a record-breaking 1.8 V in the Prussian Blue Analog //MoO 3 system at room temperature. The full cell consisting of HVFe-PBA (pre-protonated vanadium hexacyanoferrate)//SSAE//MoO 3 exhibited outstanding electrochemical performance at both room temperature and low temperatures. As a proof-of-concept, a pouch cell is assembled with an energy density of 72.3 Wh kg −1 , and even it maintained an energy density of 40.7 Wh kg −1 at −60 °C.