Electrostatic-Interaction-Assisted Construction of 3D Networks of Manganese Dioxide Nanosheets for Flexible High-Performance Solid-State Asymmetric Supercapacitors.

Abstract

A three-dimensional (3D) macroscopic network of manganese oxide (MnO₂) sheets was synthesized by an easily scalable solution approach, grafting the negatively charged surfaces of the MnO₂ sheets with an aniline monomer by electrostatic interactions followed by a quick chemical oxidizing polymerization reaction. The obtained structure possessed MnO₂ sheets interconnected with polyaniline chains, producing a 3D monolith rich in mesopores. The MnO₂ sheets had almost all their reactive centers exposed on the electrode surface, and combined with the electron transport highways provided by polyaniline and the shortened diffusion paths provided by the porous structure, the deliberately designed electrode achieved an excellent capacitance of 762 F g^-1 at a current of 1 A g^-1 and cycling performance with a capacity retention of 90% over 8000 cycles. Furthermore, a flexible asymmetric supercapacitor based on the constructed electrode and activated carbon serving as the positive and negative electrodes, respectively, was successfully fabricated, delivering a maximum energy density of 40.2 Wh kg^-1 (0.113 Wh cm^-2) and power density of 6227.0 W kg^-1 (17.44 W cm^-2) in a potential window of 0-1.7 V in a PVA/Na₂SO₄ gel electrolyte.