High-performance flexible supercapacitor enabled by Polypyrrole-coated NiCoP@CNT electrode for wearable devices.

As a pseudocapacitive electrode material, nickel-cobalt bimetallic phosphide has attracted wide attention with its advantage in capacitance and chemical activity. While, like Ni-Co oxides or sulfides, the application of nickel-cobalt bimetallic phosphide is generally hampered by its confined conductivity, low chemical stability and unsatisfactory cycle durability. Herein, this work demonstrates a NiCoP@CNT@PPy (NCP@CNT@PPy) composite that is obtained by polymerizing pyrrole monomer on the surface of NiCoP@CNT complex. According to density functional theory (DFT), it is theoretically demonstrated that the bimetallic Ni-Co phosphide (NiCoP) can exhibit more electrons near the Fermi level than single Ni or Co phosphide. Under the combined effects of carboxylic carbon nanotubes (c-CNTs) and polypyrrole (PPy), the NCP@CNT@PPy electrode exhibits excellent electrochemical performance. In addition, a flexible asymmetric supercapacitor (ASC) is prepared, which demonstrated high energy density and admirable heat-resistance and flexibility performance, showing huge potential in the application of heat-resistant storage energy systems and portable wearable devices.