Unlocking the potential of multifunctional carbon nanomaterials for zinc-ion hybrid capacitors: Mechanisms, applications, and challenges

Zinc-ion hybrid capacitors (ZIHCs) combine the high energy density of zinc-ion batteries with the power density of supercapacitors, offering great promise for advanced energy storage. However, their development is hindered by challenges including suitable cathode materials and zinc anode instability (dendrites, parasitic reactions). Carbon nanomaterials, with their tunable structures, superior conductivity, stability, and low cost, are pivotal multifunctional components in ZIHCs. This review comprehensively surveys recent advances in their dual roles: directly as high-performance cathodes and as critical modifiers for stabilizing zinc anodes, starting with an analysis of current challenges faced by each electrode and the underlying mechanisms. Firstly, an in-depth examination of structural engineering and electrochemical behavior of carbon cathodes is provided, alongside strategies to overcome capacity and kinetic limitations. Furthermore, utilizations of carbon-modified materials as interfacial layers, three-dimensional scaffolds and electrolyte additives for zinc anodes are highlighted. Finally, existing challenges and possible future research directions for application of carbon nanomaterials are outlined, providing useful insights for further development and innovation of ZIHCs as a promising advanced energy storage technology.