High-Performance Sodium-Ion Capacitor Constructed by Well-Matched Dual-Carbon Electrodes from a Single Biomass

The concept of combining the advantages of batteries and supercapacitors to obtain hybrid capacitors with both high energy and high power is considered to be promising. However, development of hybrid capacitors is still hindered by the matching problem between the cathode and the anode. Here, we report a Na-ion capacitor with well-matched carbon anode and cathode originated from the same precursor: garlic, which is a green and abundantly presented biomass in the world. The hard carbon (GDHC) anode based on ion intercalation is prepared by simple pyrolysis at high temperature, which demonstrates a high reversible capacity of 260 mA h g(-1) at 0.05 A g(-1) with an intercalating capacity of 148 mA h g(-1), a high initial Coulombic efficiency of 50.7%, and an excellent cycling stability of 80% after 10 000 cycles at 2 A The porous carbon (GDPC) cathode based on ion adsorption is prepared by a simple carbonization activation method. GDPC with developed porous architecture and high surface area (1682 m(2) g(-1)) provides a superior capacity of 152 mA h g(-1) at 0.05 A(-1). By tuning the electrode potential for the balancing of anode and cathode, the assembled sodium-ion capacitor displays highly favorable performance, i.e., 156 and 31 W h kg(-1) at 355 and 38910 W kg(-1), and retains 73% of its initial capacity after 10 000 cycles at 1.5-4.2 V. We firmly believe that this work provides a practical strategy for designing advanced sodium-ion capacitors with both the anode and the cathode prepared by a facile process.