Micron-sized H₂MoO₃/PANI for superfast proton batteries in frozen electrolyte through Grotthuss mechanism

Aqueous proton battery is considered as a promising candidate for the electrochemical energy storage system with the merits of safety, environmental benignity, fast kinetics and low cost. The realization of these advantages relies on the development of suitable and easy-access electrode materials. Herein, micron-sized H₂MoO₃/Polyaniline (PANI) is developed as a high-rate and stable anode material in proton battery. Contrary to the pseudocapacitive nature of most anode materials, the H₂MoO₃/PANI presents diffusion-controlled charge storage mechanism with both high capacity and high rate-capability. The H₂MoO₃/PANI electrode shows a rather high capacity of 268.2 mAh g^-1 at 1.0 A g^-1, and a surprisingly high rate-capability with ∼50% capacity retention even at an extremely high current density of 200.0 A g^-1. Detailed analyses demonstrate the Grotthuss mechanism of ultrafast proton conduction in H₂MoO₃/PANI. The constructed proton full cell based on H₂MoO₃/PANI delivers a high energy density of 42.1 Wh kg^-1 at 800.0 W kg^-1. Impressively, the proton full cell shows fast proton transportation even in the frozen electrolyte, and ∼70% of the room temperature capacity is retained at -20 °C. These excellent proton storage behaviors provide insights into the practical applications of micron-sized electrode materials in proton batteries at low temperatures.