B/N/O-Codoped 2D Porous Carbon Nanosheets for High-Performance Dual-Carbon Lithium-Ion Capacitors

The development of dual-carbon lithium-ion capacitors(DC-LICs)with high energy at high power density is still a challenge due tothe mismatch of capacity and dynamics of battery-type anodes/capacitor-typecathodes. Two-dimensional porous carbon nanosheets (2D-PCS) possessa large open flat layer with nanoscale thickness, exposing more activesites and shortening the ion diffusion route, which can effectivelyresolve the mismatch issue in DC-LICs. However, developing an easy-to-manipulateand widely available method to prepare 2D-PCS is still a challenge.Herein, using borax as the pore-forming agent and heteroatom dopants,an electrode with a 2D-PCS structure is obtained (noted as C-B-2).Benefiting from the open structure and doping effect, C-B-2 showsa satisfactory rate ability and high capacity both as a cathode andan anode. Besides, a symmetric "dual-carbon" deviceC-B-2//C-B-2 LIC working in the 0.01-4.5 V range was successfullyfabricated, demonstrating a high energy density of 173.1 Wh kg(-1) at a power density of 225.5 W kg(-1) and a superior cycling stability of 10,000 cycles at 2 A g(-1). Furthermore, the C-B-2//C-B-2 LICs demonstrate their practicalapplication potential in successfully powering color LEDs. This workprovides an efficient method for developing highly efficient DC-LICdevices.