One-Step Synthesis of Nitrogen/Sulfur Codoped Graphene/MnO2 Film as a High-Performance Supercapacitor

Supercapacitors have attracted tremendous attention in recent years, but the simultaneous achievement of a high volumetric energy density as well as a simple and scalable synthesis process remains challenging. Herein, a one-step electrochemical exfoliation method is utilized to prepare flexible freestanding graphene films doped and functionalized with nitrogen, sulfur, phosphor, α-MnO2, and δ-MnO2. A solid-state asymmetric supercapacitor is fabricated based on a MnO2 functionalized graphene film as the positive electrode and a nitrogen- and phosphor-codoped graphene film as the negative electrode, with a wide operating potential window of 1.6 V. The assembled asymmetric supercapacitor achieved volumetric energy and power densities of 17.4 mWh cm–3 and 4.8 W cm–3, respectively, and stable cycling, retaining 98.4% of its capacitance after 10,000 cycles. Our research reveals an approach that paves the way for a straightforward and scalable synthesis process, leading to the production of low-cost asymmetric solid-state supercapacitors.