Aqueous hybrid battery with dual mechanisms of NH4+ (de)intercalation and I−/I2 redox

The development of high-performance anode materials is crucial for aqueous ammonium ion batteries. In the meanwhile, adding an additional redox pair is thought to be a good way to raise the overall electrochemical performance of the system. In this study, a hybrid battery composed of active carbon and BiOI is developed using an NH 4 AC + NH 4 I electrolyte. Electrochemical tests and ex-situ characterization validate the dual processes of NH 4 + (de)intercalation and I − /I 2 redox. Moreover, the NH 4 I additive enhances the charge transfer of the whole battery and changes the phase transition of BiOI in the charge-discharge process. Consequently, this hybrid battery exhibits a long-term cyclic stability (70 % capacity retention after 2300 cycles at 0.2 A g −1 ) and a high specific capacity (196 mA h g −1 at 0.2 A g −1 ). The cell with a high-loading BiOI electrode (12 mg cm −2 ) also exhibits satisfactory performances, reflecting its application potential. This work provides a reference for designing aqueous hybrid battery.