Two-dimensional MXenes for sustainable energy storage: Synthesis, properties, and applications

Two-dimensional transition metal carbides/nitrides, known as MXene, with the chemical formula M n+1 X n T x , where M is a transition metal, X is carbon or nitrogen, and T x represents surface functional groups, have attracted considerable attention across a range of fields. Their appealing characteristics, such as superior hydrophilicity, excellent electrical conductivity, high specific surface area, and unique layered structure, make them highly promising for a wide range of applications. Meanwhile, MXene also serves as an excellent template for growing other materials with tunable properties, which makes it a very promising choice for a range of energy storage applications, including rechargeable batteries, supercapacitors, fuel cells, solar cells, and so on. This article provides a comprehensive review of recent advancements in two-dimensional (2D) MXene materials for energy storage applications. We first discuss the synthesis strategies of MXene, including both top-down approaches, such as HF and non-HF-assisted exfoliation of MAX phases, and bottom-up methods, including vapor phase deposition and templating methods. Subsequently, we examine the fundamental properties of MXene, encompassing their thermal, mechanical, and optical characteristics. Compared to other 2D materials like graphene and MoS 2 , MXene stands out due to its high metallic conductivity (>1500 S/cm), tunable surface chemistry, low ion diffusion barrier (<0.3 eV), and mechanical robustness (Young's modulus >300 GPa). These properties enable a threefold increase in volumetric capacity (up to 1500 F/cm 3 ) and over 90 % lithium dendrite suppression, offering a key material solution to overcome the energy density-power density-cycle life trade-off in modern energy storage systems. The review then focuses on the application of MXene in energy storage devices, particularly in metal-ion batteries and supercapacitors, highlighting their electrochemical performance and storage mechanisms. Furthermore, we analyze the key challenges associated with MXene-based energy storage systems and discuss potential strategies to overcome these limitations. Finally, we explore the future prospects of MXene-integrated devices in sustainable energy technologies, emphasizing their potential for next-generation energy storage solutions.