Flexible Solid‐State Asymmetric Supercapacitors Based on Nitrogen‐Doped Graphene Encapsulated Ternary Metal‐Nitrides with Ultralong Cycle Life

Abstract

AbstractTo meet a fast‐emerging demand, flexible energy storage applications have a great interest in the development of highly flexible hierarchical nanoarchitectures. Metal nitrides have recently been paid a significant interest as a promising electrode material for supercapacitors (SCs) owing to their high electrical conductivity, excellent redox properties, and outstanding mechanical strength. However, poor electrochemical stability seriously limits the commercialization possibilities. Herein, a novel strategy is presented for the synthesis of nitrogen‐doped graphene encapsulated with ultrasmall nickel–cobalt nitride (NiCo2N) and nickel–iron nitride (NiFeN) core–shell architectures that are explored as advanced electrodes for flexible solid‐state SC. The flexible NiCo2N@NG//NiFeN@NG asymmetric SC delivers an ultrahigh energy density of ≈94.93 Wh kg−1 at 0.79 kW kg−1, exceptional power density (≈74.67 Wh kg−1 at 39.53 kW kg−1), and ultralong cycle life (≈5.07% drop in initial capacity after 25 000 cycles). These results promote the core–shell hybrids that can be served as advanced supercapacitor materials for flexible energy storage applications.