Design of an intermediate carbon layer between bimetallic sulfide and a carbon-based substrate for high-performance asymmetric supercapacitors

The design of a flexible electrode based on carbon cloth (CC) which can solve the problem of the weak coupling effect and binding force between the substrate and active materials has stimulated intensive research on configuring supercapacitors with these materials to achieve high energy and power densities. In this paper, a N,P-doped carbon (NPC) layer as an intermediate layer is sandwiched between the active materials and carbon cloth, which can not only enable the stable and homogeneous growth of active materials on the carbon fiber but also maintain the long cycle life of the flexible electrode in supercapacitors owing to its rich structural defects, excellent hydrophilic characteristics and mechanism of heteroatom doping. Such a sandwiched flexible electrode consisting of bimetallic sulfide (BS), an N,P-doped carbon layer and carbon cloth (denoted as CC-NPC-BS) is assembled as a positive electrode in a solid-state asymmetric supercapacitor (ASC) device, which delivers a high energy density of 56.7 W h kg(-1) at a power density of 1.5 kW kg(-1) and has outstanding long cycling stability with 85% capacitance retention after 15000 cycles.