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

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. •3D hierarchical porous framework of carbon nanocages are derived from biomass.•Simultaneous templating, activation, and catalysis induce favorable hollow structure, interlayer spacing and graphitization.•The product demonstrates high performance for both supercapacitors and sodium-ion batteries.•490.7 F·g−1 at 1.0 A·g−1 and 92.0 Wh·kg−1 at 1800 W·kg−1 applied in supercapacitors.•318.2 mAh·g−1 at 50 mA·g−1 and retention rate of 92% after 1000 cycles at 10 A·g−1 in batteries.