Boron and Nitrogen Co‐Doped Porous Carbon with Ultrahigh Volumetric Performance for Zinc‐Ion Hybrid Supercapacitors

Abstract It is a huge challenge for carbon materials to obtain high volumetric capacitance without sacrificing gravimetric capacitance for supercapacitors with limited space. Herein, B/N/O co‐doped porous carbon materials are prepared by one‐step carbonization method using boric acid as the template and boron source, polyacrylamide as the carbon and nitrogen sources. Boric acid and polyacrylamide can be closely combined by hydrogen bond, so as to not only give full play to the role of boric acid template, but also to achieve high content of nitrogen and boron functional groups. Benefiting from the high bulk density (1.51 g cm⁻³), suitable specific surface area (243.2 m² g⁻¹) and numerous B (7.55 at.%), N (14.38 at.%), O (8.89 at.%) functional groups, the prepared BNPC‐700 electrode shows an ultrahigh volumetric specific capacitance of 545.6 F cm⁻³ at 0.5 A g⁻¹, excellent rate characteristic and superior electrochemical performance. Furthermore, the assembled BNPC‐700 symmetric supercapacitor achieves a high volumetric energy density of 31.1 Wh L⁻¹ (20.6 Wh kg⁻¹) in ZnSO₄ aqueous electrolyte. More importantly, the assembled Zn//ZnSO₄//BNPC‐700 hybrid supercapacitor delivers a high volumetric capacity of 210.8 mAh cm⁻³ and a high volumetric energy density of 147.7 Wh L⁻¹(97.8 Wh kg⁻¹).