Template-free synthesis of hierarchical porous carbon via biomass upcycling: A boost for zinc-ion hybrid capacitor energy storage

Zinc-ion hybrid capacitors (ZIHCs) have emerged as a promising energy storage technology, integrating the merits of high-power supercapacitors and high-energy batteries while offering cost-effectiveness and safety. However, their commercialization is hampered by challenges such as limited energy density, low power output, and poor cycling stability. Herein, we report a sustainable strategy to fabricate heteroatom-doped coral-like hierarchical porous carbon (LCK-800) as an advanced cathode for ZIHCs. The synthesis of LCK-800 synergistically utilizes industrial sodium lignosulfonate and chitosan through hydrogen-bond-directed self-assembly. This approach generates a 3D interconnected meso/microporous architecture and large surface area measuring 2227.32 m2 g−1 along with adjustable heteroatom doping capabilities. Assembled as a ZIHC with a Zn anode in 2 M ZnSO4 electrolyte, LCK-800 exhibits remarkable performance: a gravimetric capacitance reaching 202 mA h g−1 under 0.1 A g−1 current density, an energy density of 189 W h kg−1 at a power density of 97 W kg−1, and preserving 97.5 % of its original capacity through 10,000 operational cycles under 5 A g−1. This study not only provides a green, template-free approach for synthesizing high-performance heteroatom-doped carbons but also offers insights into the structure-property relationships of ZIHCs, facilitating the advancement of novel eco-friendly energy storage systems for future applications.