Free-standing N-self-doped carbon nanofiber aerogels for high-performance all-solid-state supercapacitors

Abstract N-self-doped carbon nanofiber (NCNF) aerogels with lightweight, porosity, three dimensional (3D) interconnected network structure, and silk cocoon-like node morphology have been successfully fabricated via growth in situ of the zeolitic imidazolate frameworks (ZIF8) nanocrystals on bacterial cellulose (BC) in an aqueous system, subsequent dry-freezing, and then a thermal treatment process. Benefiting from the unique shape and structural characteristics, and fascinating properties of NCNF aerogels, the optimal aerogel (NCNF2-900) exhibits remarkable capacitances of ∼224 F/g at 0.5 A/g, and ∼612 mF/cm 2 at 1.37 mA/cm 2 , respectively, superior energy density of 31.04 Wh/kg (13.19 Wh/L) at a power density of 250 W/kg, and long-term durability (retention ∼97%, at 5 A/g after 10 000 cycles). Further, an all-solid-state symmetric supercapacitor (SSC) based on two same NCNF2-900 aerogels is constructed and delivers significantly improved electrochemical performances of 41.1 F/g at 0.25 A/g based on total mass of electrodes, and 2.5 F/cm 3 at 1.37 mA/cm 2 respectively, as well as 5.7 Wh/kg (0.34 Wh/L) at power density of 125 W/kg, and retained 2.5 Wh/kg (0.15 Wh/L) at 1250 W/kg, while excellent stability with a capacitance retention of 91% over 5000 cycles, at 2.5 A/g. Moreover, such a facile yet effective, green and scalable approach for construction of free-standing porous carbon aerogels can be applicable to other advanced functional materials for a wide range of applications.