Advances in MXene-based composites for next-generation flexible supercapacitors: From design and development to applications

Flexible supercapacitors (FSCs) are ubiquitously integrated into advancing miniaturized gadgets, wearables and portable electronic technologies. The allure of FSCs lies in their flexibility, compact size, and lightweight, which has compelled extensive investigation in the domain of FSCs. The performance of supercapacitor devices is largely determined by the choice of electrode material and the interaction at the electrode-electrolyte interface. In this context, MXene, an expeditiously expanding class of 2D materials, have garnered significant attention in the exciting field of flexible devices, owing to their high electrical conductivity, distinctive layered structure, substantial surface area, excellent hydrophilicity, and abundant surface terminal groups. These interesting attributes of MXene critically influence interfacial charge storage and transport mechanisms. This review strives to discuss the latest developments in MXene and MXene-based electrode materials for flexible supercapacitors. The review thoughtfully presents the aspects of flexibility, followed by discussions on device designing and fabrication. The role of substrate in fostering flexibility, requisite for solid-state electrolyte, and the influence of diverse device architecture on interfacial stability are closely scrutinized. The review incorporates a comprehensive discussion of the factors impacting the performance of MXene materials, with a particular focus on the features including composition, structure, electrode-electrolyte interaction, electrode morphology and device architecture. Besides, this review extensively investigates fabrication routes, electrochemical performance and mechanical resilience of MXene and MXene-based composites for FSCs. Armed with these insights, the review proposes a prospective roadmap delineating the challenges and opportunities in the advancement of MXene-based electrode materials for flexible supercapacitors.