A high over-potential binder-free electrode constructed of Prussian blue and MnO₂ for high performance aqueous supercapacitors

Extending the potential window of aqueous supercapacitors (SCs) up to 2.0 V is still a great challenge. Based on their good dynamic structural reversibility and open framework structure, the coordination superamolecular networks (CSNs) exhibit rapid charge/discharge ability and excellent cycle stability. As a typical coordination superamolecular network (CSN), Prussian blue (denoted as CSN-PB), which self-assembled by the CN^- ligand and iron ions is firstly in-situ grown on carbon cloth, followed by electro-deposition of MnO₂ to form CSN-PB/MnO₂ composite electrode. Benefiting from synergistic effect of the constituent components, as well as the open framework structure of CSN-PB, this composite electrode reaches a high potential window of 1.4 V (vs. Ag/AgCl) and delivers a good specific capacitance of 315.3 F·g^-1 in aqueous electrolyte. An aqueous asymmetric device, constructed with CSN-PB/MnO₂ composite as cathode and activated carbon as anode, can work in a stable potential window of 2.4 V, exhibits a high energy density of 46.13 Wh·kg^-1 and excellent cycling stability with 85.5% capacitance retention after 20, 000 cycles. This work provides a new concept of high dynamic structural reversibility from CSNs to increase the cell voltage of asymmetric SCs for further boosting energy density.