CNT threading N-doped porous carbon film as binder-free electrode for high-capacity supercapacitor and Li-S battery
A novel light-weight free-standing CNT threading nitrogen-doped porous carbon film (CNCF) has been synthesized as 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), hierarchical pore structure, good nitrogen doping (2.8 at%) and overall electrical conductivity. When used as binder-free electrode for 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 10000 cycles at 20 A g-1, and high energy density of 21.1 Wh kg-1 with a power density of 5000 W kg-1. It can also serve as efficient sulfur host for Li-S battery. The S@CNCF electrode exhibits a high discharge capacity of 926 mAh g-1 after 200 cycles at 1 C, and 614 mAh 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 was increased to 6.9 mg cm-2, it shows a high initial areal capacity of 7.3 mAh cm-2 and a volumetric capacity of 0.94 Ah cm-3. This will hold a promising potential for flexible or film-like high energy storage system.