Fe(CN)₆^3- ion-modified MnO₂/graphene nanoribbons enabling high energy density asymmetric supercapacitors

Due to its high theoretical specific capacitance and high oxygen evolution potential, MnO₂ has been considered as a promising positive electrode material for high-energy asymmetric supercapacitors (ASCs). However, the search for MnO₂ positive electrodes with high specific capacitance and excellent rate performance for ASCs remains challenging. Herein, for the first time we report a novel strategy for the synthesis of Fe(CN)₆^3- ion-modified MnO₂/graphene ribbons (m-MnO₂/GRs) as the positive electrode for high energy density ASCs. Benefiting from vertically aligned MnO₂ grown on the interconnected graphene ribbon and Fe(CN)₆^3- ion modification, the m-MnO₂/GR exhibits a high specific capacitance of 435 F g^-1, excellent rate capability and cycling stability. More importantly, the assembled m-MnO₂/GR//GR ASC exhibits a high energy density of 57.8 W h kg^-1 at a power density of 1.2 kW kg^-1, as well as outstanding cycling stability with 100% capacitance retention after 10000 cycles. More importantly, such a device can be charged/discharged within 0.79 s in an ultrafast manner to deliver a high specific energy of 10.5 W h kg^-1 at an ultrahigh specific power of 48 kW kg^-1. Thus, our strategy could be possibly used for the design and fabrication of new energy storage devices with high energy and power densities for future applications.