Optimizing the microstructure of carbon nano-honeycombs for high-energy sodium-ion capacitor

Abstract

Carbon materials have received a great assiduity as anode for sodium ion storage, however, the sluggish kinetics of Na+ ions limit their development, suffering from low specific capacity and poor cycling stability. Herein, an eco-friendly biomass carbonization strategy is utilized to synthesize porous carbon nano-honeycombs (CNs) with hierarchical microstructures. Inspiringly, graphitic domains in the CNs can endow conductivity way for electron/charge transport, simultaneously, disordered domains with dilated lattice spacing (0.4 nm) are beneficial for Na+ storage. Both of the merits synergically make the CNs boost superior sodium storage performance with high reversible capacity (322 mAh g‒1 at 50 mA g‒1), superb rate capability (91 mAh g‒1 at 5.0 A g‒1), and cycling stability (99.8% retention over 10,000 cycles at 2.5 A g‒1). Moreover, the CNs-based sodium-ion capacitor (SIC) device achieves high energy/power densities (122 Wh kg‒1 at 112.5 W kg‒1 and 17,619 W kg‒1 at 34.6 Wh kg‒1) with an outstanding cycle stability (95.7% retention over 10,000 cycles at 1.0 A g‒1). Our findings provide insights into optimizing the microstructure of carbon for boosting sodium storage.