Facile Synthesis of P-Doped Carbon Nanosheets as Janus Electrodes of Advanced Potassium-Ion Hybrid Capacitor

Potassium-ion hybrid capacitors (PIHCs) shrewdly integrate the merits of the high energy density of battery-type anode and the high power density of capacitor-type cathode, promising prospects for potential application in a diversity of fields. Here, we report the synthesis of P-doped porous carbon nanosheets (P-PCNs) with favorable features as electrochemical storage materials, including ultrahigh specific surface area and rich activity sites. The P-PCN as Janus electrodes show highly attractive electrochemical properties of high capacity and remarkable stability for fast K+ storage and manifest high capacitance for PF6– adsorption. The P-PCNs are applied as both anode and cathode materials to set up dual-carbon PIHCs, which show the capability to deliver a high energy/power density (165.2 Wh kg–1 and 5934.4 W kg–1) as well as remarkable long-life capability.