CNT-threaded N-doped porous carbon film as binder-free electrode for high-capacity supercapacitor and Li–S battery

Abstract

A novel lightweight, free-standing, CNT-threaded nitrogen-doped porous carbon film (CNCF) has been synthesized as a binder-free electrode for supercapacitor and Li–S battery. The meticulous structural design of using CNT to thread the ZIF-8-derived porous carbon polyhedrons together endows the porous carbon thin film with nice flexibility, high surface area (645.2 m² g⁻¹), and hierarchical pore structure as well as good nitrogen doping (2.8 at%) and overall electrical conductivity. When used as binder-free electrode for a supercapacitor, the CNCF delivers a high specific capacitance of 340 F g⁻¹ at 2 A g⁻¹, long-term stability with a coulombic efficiency of 97.7% after 10 000 cycles at 20 A g⁻¹, and high energy density of 21.1 W h kg⁻¹ with a power density of 5000 W kg⁻¹. It can also serve as an efficient sulfur host for the Li–S battery. The S@CNCF electrode exhibits a high discharge capacity of 926 mA h g⁻¹ after 200 cycles at 1C, and 614 mA h g⁻¹ after 1800 cycles with an ultra-low overall capacity decay of 0.02%/cycle with sulfur loading of 3 mg cm⁻². Moreover, when the sulfur loading is increased to 6.9 mg cm⁻², the electrode shows a high initial areal capacity of 7.3 mA h cm⁻² and a volumetric capacity of 0.94 A h cm⁻³. This film holds promising potential for flexible or film-like high-energy storage systems.