Interconnected N/P co-doped carbon nanocage as high capacitance electrode material for energy storage devices

Heteroatom doping carbon materials exhibit a huge application potential for energy storage devices (ESDs). Herein, interconnected N/P co-doped carbon nanocage (NP-CNC) was synthesized from pyrene molecules by using nano-MgO as template and melamine-phytic acid supramolecular aggregate as dopant coupled with KOH activation. The as-prepared NP-CNC possesses interconnected nanocages for electron transportation and abundant micropores for ion adsorption. Moreover, co-doped N/P species in NP-CNC provide active sites and additional pseudocapacitance. Consequently, NP-CNC as electrode material for symmetric supercapacitor exhibits a high gravimetric capacitance of 435 F·g⁻¹ at 0.05 A·g⁻¹, high volumetric capacitance of 274 F·cm⁻³ at 0.032 A·cm⁻³, and long cycle lifespan with 96.1% capacitance retention after 50,000 cycles. Furthermore, NP-CNC as cathode for zinc-ion hybrid supercapacitor delivers satisfactory energy and power densities of 130.6 Wh·kg⁻¹ (82.3 Wh·L⁻¹) and 14.4 kW·kg⁻¹ (9.1 kW·L⁻¹). This work paves a promising approach to the preparation of high capacitance NP-CNC for ESDs.