Aqueous hybrid battery with Prussian blue analogue cathode and activated carbon anode in heptyl viologen dibromide electrolyte for enhanced performance and suppressed self-discharge

초록

Hybrid energy storage devices can simultaneously enhance energy and power density through faradaic and capacitive charging. However, power density is limited by the kinetic imbalance between electrodes due to the slow kinetics of battery-type electrode. In this study, small-sized cobalt hexacyanoferrate (CoHCF) particles with a three-dimensional open framework structure were employed as the cathode to enable fast ion transport. In addition, the anode used activated carbon with lower charge storage capacity than the cathode by increasing its mass and simultaneously adding redox-active heptyl viologen dibromide (HVBr2) to the electrolyte to minimize electrode thickness. The CoHCF//activated carbon hybrid battery achieved a maximum energy density of 44 Wh kg-1 and a maximum power density of 516 W kg-1, utilizing an anode/cathode mass ratio of 2 and HVBr2 electrolyte. These values represent a six-fold increase in energy density and a two-fold increase in power density compared to hybrid battery using inert Na2SO4 electrolyte with the same mass ratio. Furthermore, the adsorption of HV center dot+ and HVBr2-film on the anode surface suppressed self-discharge and retained 78% of capacity after 72 h. This study developed an aqueous hybrid battery with improved energy and power density by addressing charge storage imbalance between electrodes using mass balance and HVBr2 electrolyte.

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