Abstract: MXenes have attracted increasing attention because of their rich surface functional groups, high electrical conductivity, and outstanding dispersibility in many solvents, and have demonstrated competitive efficiency in energy storage and conversion applications. However, the restacking nature of MXene nanosheets like other two-dimensional (2D) materials through van der Waals forces results in sluggish ionic kinetics, restricted number of active sites, and ultimate deterioration of MXene material/device performance. The strategy of raising 2D MXenes into three-dimensional (3D) structures has been considered an efficient way for reducing restacking, providing greater porosity, higher surface area, and shorter distances for mass transport of ions, surpassing standard one-dimensional (1D) and 2D structures. In multivalent ion batteries, the positive multivalent ions combine with two or more electrons at the same time, so their capacities are two or three times that of lithium-ion batteries (LIBs) under the same conditions, e.g., a magnesium ion battery has a high theoretical specific capacity of 2 205 mAh g^-1 and a high volumetric capacity of 3 833 mAh cm^-3. In this review, we summarize the most recent strategies for fabricating 3D MXene architectures, such as assembly, template, 3D printing, electrospinning, aerogel, and gas foaming methods. Special consideration has been given to the applications of highly porous 3D MXenes in energy storage devices beyond LIBs, such as sodium ion batteries (SIBs), potassium ion batteries (KIBs), magnesium ion batteries (MIBs), zinc ion batteries (ZIBs), and aluminum ion batteries (AIBs). Finally, the authors provide a summary of the future opportunities and challenges for the construction of 3D MXenes and MXene-based electrodes for applications beyond LIBs.

Key words: 3D MXene, Fabrication methods, Multivalent ion batteries, Beyond LIBs