One-step production of carbon nanocages for supercapacitors and sodium-ion batteries

Abstract

Abstract Utilizing biomass to produce high-performance energy-storage materials has been the focus of increasing attention, thanks to the low cost, renewability, environmental friendliness, and inherent nature of certain biomass. However, the applications of biomass-derived carbons are commonly confined by their low electrical conductivity and ion diffusion kinetics. In this work, we report one-step strategy of synchronous activation and graphitization, using a new activating agent, i.e. KMnO4, to produce three-dimensional (3D) hierarchical porous framework of carbon nanocages (FCNC) from biomass for both supercapacitors and sodium-ion batteries (SIBs) applications. As a result, high specific capacitances (490.7 F·g−1 at a charge density of 1.0 A·g−1 in a three-electrode system using 6 mol·L−1 KOH aqueous as electrolyte) and high energy density (92.0 Wh kg−1 at power density of 1800 W·kg−1 using EMIMBF4 electrolyte) have been demonstrated when applying FCNC in supercapacitors, and high reversible capacity of 318.2 mAh·g−1 at 50 mA·g−1 has been achieved in SIBs. Although the rate performance is one of the primary concerns of SIBs, a high retention rate of 92% is realized in the present case after 1000 cycles at 10 A·g−1. Excitingly, even at 10 A·g−1, the reversible capacity delivered by FCNC maintains to be as high as 81.6 mAh·g−1.