An Engineering Porous Spherical Carbon Cathode for High-Energy Sodium-Ion Capacitor

Sodium-ion hybrid capacitors (SICs) are emerging as promising devices that can balance energy and power output. However, the lack of a high-capacity cathode that can match the anode has limited its further application. In this work, we develop an efficient method to prepare spherical porous carbons (SPCs) with great specific surface area and narrow pore size distribution from coal-based humic acid via spray drying and a subsequent chemical activation process. Thanks to this unique porous structure, the SPC cathode has a superb capacity of 223 F g^-1 at 0.05 A g^-1, as well as splendid rate performance and cycling stability. SICs constructed by an SPC cathode and hard carbon anode can exhibit a high energy density of 179.8 Wh kg^-1 at 155 W kg^-1 and achieved 89.4% capacity retention after 10 000 cycles at 0.5 A g^-1. This outcome presents a viable approach to attaining high-capacity cathodes for constructing outstanding performance hybrid capacitors.