Recent Advances in Carbon Cathode Materials toward High-Performing Zinc-Ion Hybrid Supercapacitors

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) have emerged as promising next-generation electrochemical energy-storage devices due to their intrinsic safety, low cost, and ability to combine the high energy density of batteries with the high power density and long lifespan of supercapacitors. However, development is still in its infancy, and challenges include the limited performance of the capacitive/pseudocapacitive cathode material, whose structure and chemistry largely determine the device's energy-storage capabilities. Carbon materials, particularly porous carbons, have been extensively studied as cathode materials in ZHSCs. Recent advancements-including activated carbons, template-assisted carbons, metal-organic-framework-derived carbons, and biomass-derived carbons-have enabled significant progress in tailoring pore structures, chemical functionalities, and electronic properties to enhance zinc-ion energy storage. This review summarizes these developments, examining their synthesis methods and the design principles shaping their electrochemical behavior. Additionally, strategies of heteroatom doping and hybridization were critically evaluated, highlighting pathways to enhance electronic/ionic conductivities and pseudocapacitance. Finally, remaining challenges-including limited tunability of pore structures, incomplete mechanistic understanding, and restricted performance-were outlined, along with future directions for rational design and scalable synthesis. This review offers an updated perspective on engineering carbon cathode materials for high-performing ZHSCs and their potential in advancing safe, sustainable electrochemical energy storage.