Porosity Engineering of MXene Architectures: Toward High-Performance Aqueous Electrochemical Energy Storage

Aqueous electrochemical energy storage systems (EESs) have garnered growing attention due to their inherent safety, environmental friendliness, and rapid charge-discharge capabilities, positioning them as promising candidates for next-generation sustainable energy technologies. Among various electrode materials, MXenes are particularly appealing owing to their excellent electrical conductivity, layered structure, and tunable surface functionalities. However, their practical application is still hindered by issues such as nanosheet restacking, limited ion accessibility, and structural instability. Porosity engineering has emerged as a key strategy to mitigate these issues by expanding ion diffusion pathways, increasing the exposure of electroactive sites, and enhancing structural robustness. This review first outlines the structural features, porosity characteristics, and charge storage mechanisms of MXenes in aqueous EESs. It then provides a systematic overview of porosity engineering strategies, including chemically engineered porosification, functionalization-induced porosification, energy field-assisted porosification, template-assisted porosification, integration with porous functional components, self-assembly/self-supporting-driven porosification, and advanced manufacturing techniques. Furthermore, the impact of porosity modulation on the redox electrochemistry of MXenes is critically discussed to elucidate structure-property relationships across diverse aqueous EESs (including alkali-metal-ion batteries, multivalent-metal-ion batteries, and supercapacitors). Finally, existing contradictions, challenges, and future directions for designing porous MXene architectures are presented to accelerate their practical development in aqueous EESs.