Rational design of d-glucose derived nitrogen-doped hierarchical porous activated carbon: an ultra-performance cathode for zinc-ion hybrid supercapacitors†

In the development of high-performance carbon cathode materials for sustainable and advanced zinc-ion hybrid supercapacitor (Zn-HSC) applications, a comprehensive understanding of the design principles for carbon-based cathodes, as well as the impact of zinc anode configuration and electrolyte on the overall supercapacitor performance, remains unclear. Herein, acetylene black carbon (C_AB) and a series of D-glucose-derived carbon materials, such as carbonaceous microspheres (C_ms), nitrogen-doped carbonaceous microspheres (N-C_ms), and different N-doped hierarchical porous activated carbons (N-hpaC-X, where X = 600, 700, and 800, corresponding to the pyrolysis temperature in °C), were selected to investigate the influence of carbon structures on the electrochemical performance of Zn-HSCs. The specific capacitance values obtained for the aqueous Zn-HSCs with different carbon cathodes at a current density of 0.5 A g⁻¹ followed the order of C_AB (23 F g⁻¹) < C_ms (142 F g⁻¹) < (N-C_ms (152 F g⁻¹) < N-hpaC-800 (200 F g⁻¹) < N-hpaC-600 (222 F g⁻¹) < N-hpaC-700 (342 F g⁻¹). These results demonstrated the synergistic effects of the carbon microsphere structure, N-doping and high-temperature activation processes in enhancing the energy storage performance of Zn-HSCs. Notably, N-hpaC-700 exhibited exceptional electrochemical performance, delivering specific capacitances of 342 and 285 F g⁻¹ in aqueous and gel electrolytes at 0.5 A g⁻¹, respectively, corresponding to energy densities of 190 and 159 W h kg⁻¹, and power densities of 500 and 455 W kg⁻¹. Furthermore, N-hpaC-700-based aq. Zn-HSC demonstrated appreciable cycling stability, retaining 72% of its initial capacity and 99% of its coulombic efficiency after 5000 cycles at 5 A g⁻¹. The N-hpaC-700-based all-solid-state (ASS) Zn-HSC device displayed a low self-discharge rate, maintaining 95% of its open-circuit potential for 12 h, and also maintained good stability under flexible conditions. In real-time applications, the N-hpaC-700-based ASS-Zn-HSC successfully powered a green LED for 1 h and 7 min. The outstanding performance of the N-hpaC-700 cathode could be ascribed to its glucose-derived carbon structure, N-doping and optimal thermal activation processes, which collectively enhanced the electrode's structural integrity, electrical conductivity, and wettability, leading to improved charge storage capabilities. These findings highlight the potential of glucose-derived N-hpaC-700 as an ultra-efficient cathode material for Zn-HSC devices, offering exceptional performance, cost-effective synthesis, and environmental sustainability.