N/O/P Co-Doped Highly Microporous Carbons with Optimized Volumetric and Gravimetric Supercapacitive Performance

The practical application of supercapacitors necessitates both high volumetric and gravimetric performance. However, carbon materials with high gravimetric performance often contain significant meso- and macropores, which detrimentally affect their volumetric performance. Herein, we developed a facile homogeneous activation technique for the preparation of N/O/P co-doped highly microporous carbons (P@CSX). Utilizing P 2 O 5 as a homogeneous activator, we simultaneously achieved micropore construction and uniform N/O/P co-doping. The optimized material, P@CS7, demonstrated an impressive micropore ratio of 85.5%, a high specific surface area of up to 918 m 2 g –1, and a notable compaction density of 1.34 g cm –3 . These attributes facilitated a balance between the gravimetric capacitance (210 F g –1 ) and volumetric capacitance (281 F cm –3 ) at 0.2 A g –1 . The assembled symmetrical supercapacitor device exhibited a remarkable energy density of 21.2 W h L –1 at a power density of 361.8 W L –1 (15.8 W h kg –1 at 270 W kg –1 ) and maintained 13.53 W h L –1 at 7.24 kW L –1 (10.1 W h kg –1 at 5.4 kW kg –1 ). This work offers a promising strategy for designing carbon materials that achieve high gravimetric and volumetric supercapacitive performance.