Abstract: The hybrid Zn battery is a promising electrochemical system integrating the redox reactions of transition metal oxides and oxygen in a single cell, through which high energy efficiency and energy density can be achieved simultaneously. However, the positive electrode usually suffers from unsatisfactory capacity utilization of the active material and poor oxygen reduction and evolution reaction activity. Here, a novel nano-structured Co₃O₄ electrode with the decoration of Ag nanoparticles is developed. Benefiting from the synergistic function between Ag nanoparticles and Co₃O₄ nanowires, the electric conductivity is improved and the morphology is optimized effectively. With this electrode, a hybrid Zn battery delivers five-step discharge voltage plateaus from 1.85 to 1.75, 1.6, 1.55, and 1.3 V, a high active material utilization ratio of 18%, and a low voltage gap of 0.69 V at 1 mA·cm^-2. Moreover, it can operate stably for 500 cycles with a voltage gap increase of only 0.03 V at 10 mA·cm^-2. This work brings up a novel electrode for an ultra-high performance hybrid Zn battery with both high active material utilization and outstanding oxygen electrocatalytic activity.

Key words: hybrid Zn battery, cobalt oxide, Ag nanoparticles, active material utilization, voltage gap