Design and charge storage mechanisms in MXene composite-based supercapacitors

Abstract 2D MXenes have emerged as a cutting-edge family of materials for next-generation supercapacitors, distinguished by their metallic conductivity, adaptive surface chemistry, and precisely tunable layered architecture. These materials have emerged as promising materials for energy storage in supercapacitors; however, challenges such as restacking and structural degradation have motivated the development of composites, which can synergistically enhance electrochemical performance and stability. This review elucidates the charge storage mechanisms in MXene-based composites, including the formation of electric double layers, pseudocapacitance, and ion intercalation. It also highlights the charge storage mechanisms involved in MXene-based composites, mainly including carbon nanostructures, inorganic materials, and organic matrices. MXene–carbon hybrids with graphene, carbon nanotubes (CNTs), carbon nanodots enhance ion/electron transport and prevent restacking; MXene–inorganic hybrids with metal oxides, metal-organic frameworks (MOFs), etc., provide abundant redox sites and structural stability; and MXene–organic composites with polymers or cellulose offer mechanical flexibility, processability, and environmental compatibility while maintaining excellent electrical performance. The review also discusses current challenges such as oxidation, aggregation, and interface instability, proposing strategies such as interfacial engineering, surface functionalization, and 3D structural design. By bridging compositional innovation with electrochemical insight, this article presents a holistic framework for the development of next-generation MXene-based supercapacitors that combine high energy density, long-term durability, and mechanical adaptability.