Gas expansion-assisted preparation of 3D porous carbon nanosheet for high-performance sodium ion hybrid capacitor

Sodium ion hybrid capacitors (SIHCs) have attracted considerable attentions due to their high-energy density of batteries and high-power output of supercapacitors. However, the slow intercalation kinetics of anode and low specific capacity of cathode greatly hinder the high-performance output of the SIHCs. Herein, we develop a facile chemical gas expansion method with chemical etching to prepare 3D nitrogen and sulfur co-doped porous carbon nanosheet (PCNS). As an anode material of SIBs, the PCNS displays a high reversible capacity of 205 mAh g⁻¹ at 0.5 A g⁻¹, outstanding rate capability of 96 mAh g⁻¹ at 20 A g⁻¹, and excellent cycle performance of 180 mAh g⁻¹ at 7 A g⁻¹ after 10 000 cycles. Based on this good performance, a dual-carbon SIHC is assembled by battery-type anode material (PCNS) and capacitive-type cathode material (hierarchically porous carbon). This device exhibits high energy densities of 119 Wh kg⁻¹ and 53 Wh kg⁻¹ at power densities of 200 W kg⁻¹ and 20 kW kg⁻¹, respectively. Besides, it possesses a superior cycle life of 82% capacity retention after 8000 cycles. Moreover, this work provides a new idea for the synthesis of carbon materials as high-performance SIBs and SIHCs electrode materials.