N/S co-doped interconnected hierarchical porous carbon cathode for zinc-ion hybrid capacitors with high energy density

Porous carbon materials (PCMs) are regarded as one of the most promising cathode materials for zinc-ion hybrid capacitors (ZIHCs) because of their low cost and abundant resource. Nevertheless, it is still a major challenge to enhance the energy density of PCMs-based ZIHCs. Herein, N/S co-doped interconnected hierarchical porous carbons (NS–IHPCs) are prepared from coal tar pitch (CTP) via a MgO@ZIF-8 double-template, in situ activation and N/S doping strategy to tune the microstructure and chemical composition . The as-prepared NS-IHPC 1.5 features high specific surface area of 1273 m 2 g −1 , hierarchical pore structure and suitable heteroatom doping. Consequently, as a cathode, the NS-IHPC 1.5 -based ZIHC exhibits a high energy density of 125.3 Wh kg −1 at 134.5 W kg −1 and still remains 85.3 Wh kg −1 at 14096.1 W kg −1 . The calculation results of density functional theory (DFT) demonstrate that the combination of pyrrole nitrogen and ortho-oxidized sulfur in samples achieves more negative Zn 2+ adsorption energy . Correspondingly, the high capacity (166.5 mAh g −1 at 0.2 A g −1 ) and long cycle stability (94.0 % capacitance retention at 5 A g −1 after 20,000 cycles) are achieved for NS-IHPC 1.5 . This work offers a reliable way for synthesizing remarkable cathode materials from coal chemical by-products for energy storage. • N/S co-doped interconnect hierarchical porous carbons (NS–IHPCs) are obtained. • NS-IHPCs are synthesized by double-template coupled with in situ activation strategy. • NS-IHPCs feature 3D architecture with hierarchical pores and tunable N/S species. • DFT results show N-6 and S–O render NS-HIPC more negative Zn 2+ adsorption energy. • NS-HIPC 1.5 capacitor achieves high energy density of 125.3 Wh kg −1 at 134.5 W kg −1 .