High energy density aqueous asymmetric supercapacitors based on MnO2@C branch dendrite nanoarchitectures

The flourishing development of the asymmetric supercapacitor (ASC) device has improved the energy density of supercapacitor in some extent. However, the energy density of the present ASC device is too low to meet the requirement of daily life. The two principal factors determining the energy density are the specific capacitance and the voltage window of the ASC device, which are closely related with the kinds of the electrode materials and the electrolytes. In this work, a new MnO2@C branch-dendrite (MnO2@C-BD) nanoarchitectures as a whole have been triumphantly in-situ prepared and acted as the cathode materials of the ASC device. Moreover, the MnO2@C-BD materials are assembled by innumerable MnO2 nanoparticles coated by the thin carbon layer which provides porous texture and benefits the transportation of ions and electrons. The electrochemical performances of the MnO2@C-BD electrode were assessed in 5 M lithium bistrifluoromethanesulfonimide (LiTFSI) electrolyte with the purpose of broaden voltage window aqueous electrolyte. Subsequently, the nanoporous carbon (NPC) materials have been acted as the anode for the MnO2@C-BD//NPC ASC device. As we expected that the MnO2@C-BD//NPC ASC device can offer 3 V voltage window and exhibit the maximum energy density of 88.7 Wh kg−1 at 103 W kg−1 power density.