Fluorine and Nitrogen Co-Doped Carbon Nanosheets In-Situ Loaded Cofe2o4 Particles as High-Performance Anode Materials for Sodium Ion Hybrid Capacitors

Abstract

Sodium ion hybrid capacitors (SIHCs) are recognized to be promising electrochemical energy storage devices due to their high energy/power density and ultra-long cycle life. Nevertheless, the imbalance between the rapid capacitive reaction of the cathode and the slow Faraday reaction of the anode leads to a kinetic imbalance of the electrochemical reaction between two electrodes, thus restricting the overall energy density and power density improvement of SIHCs. Herein, CoFe2O4 nanoparticles were grown in situ on the surface of nitrogen-fluorine atoms co-doped ultra-thin porous carbon nanosheets (NF-CNs) as anode electrode materials of SIHCs by simple high-temperature pyrolysis and subsequent one-step hydrothermal method. The excellent electrical conductivity and abundant mesopores of the carbon matrix not only accelerate the electron transport rate, but also realize the ultra-fast Na+ migration kinetics, thus contributing significantly to expediting the reaction kinetics of the anode in SIHCs. Systematic experiments demonstrate that CoFe2O4@NF-CNs provides SIHCs with excellent energy and power density (maximum 96 Wh kg-1 and 4 kW kg-1) while maintaining excellent cyclic stability (capacitance retention≈60.7% after 3000 cycles).

Keywords: Sodium ion hybrid capacitors, bimetallic oxides, heteroatom-doped carbon, anode