N/P co-doped hierarchical porous carbon materials for superior performance supercapacitors

The N/P co-doped hierarchical porous carbon materials are synthesized by SiO2-template approach following potassium phosphate activation. Polyvinylidene fluoride is used as the carbon source, melamine as the nitrogen source and potassium phosphate as the phosphorus source and activator. The obtained porous carbon materials exhibit a hierarchical pore structure (∼0.6 and ∼4 nm), a large specific surface area (1431 m2 g−1) and a high nitrogen and phosphorus content. These predominant characteristics enable the CNP-5-800 sample to exhibit a superior specific capacitance of 337 F g-1 at 0.5 A g−1 and outstanding cycling stability of 97.8% retention after 10000 cycles in a three-electrode system. Even in the two-electrode system (an all-solid-state symmetric capacitor), this kind of materials still can deliver an energy density of 23.1 W h kg−1 to 12.4 W h kg−1 at power densities of 720.4 W kg−1 to 13950 W kg−1, respectively, and a cycling property of 98.7% maintenance after 5000 cycles. Therefore, the practicable synthetic method and excellent electrochemical performance make CNP-x-y materials a potential candidate in supercapacitor application.