past few decades. [2] In spite of the great success of the LIBs in consumer electronics and electric vehicles, their gridscale implementation is hindered by the limited lithium resources (only 20 ppm in the earth's crust) as well as the safety concerns. [3] In this regard, many other EES systems based on more abundant and less active elements, such as sodium (2.3%), potassium (2.1%), magnesium (2.3%), aluminum (8.2%), and zinc (75 ppm), have been developed and have already achieved significant progress. [1d,4] Historically, 2D layered materials have been employed as electrodes for batteries (e.g., graphite, [5] LiCoO 2 , [6] and TiS 2 [7]). Since the discovery of monolayer graphene in 2004, [8] more and more emerging 2D materials have quickly become popular electrode materials for various EES devices. This is not surprising given the unique structure and property of 2D materials. Their relatively large interlayer space allows fast ion (de)intercalation, whereas the highly anisotropic 2D structure enables fast charge transfer. Recently, a new class of 2D transition metal carbides, nitrides, and carbonitrides, known as MXenes, [9] was discovered and has attracted increasing research interest. Up to date, more than 30 MXenes have been successfully synthesized. [10] Similar to other 2D layered materials, MXenes also possess large/tunable interlayer spaces and high aspect ratios. In addition, MXenes show excellent hydrophilicity (contact angle is ≈21.5°-35°) [11] and extraordinary conductivity (e.g., ≈9880 S cm −1 for Ti 3 C 2 T x , 3250 ± 100 S cm −1 for V 2 CT x). [12] Further, MXenes are coupled with various terminations (e.g., OH, O, and F), which endow rich surface chemistries. These unique properties make them appealing in various applications, especially for energy storage devices such as batteries and supercapacitors. [1d,4i,13] We noted that there have already been several excellent reviews on the application of MXenes for energy storage and conversion, which cover a wide range of topics including for LIBs, supercapacitors, electrocatalysis, photocatalysis, electromagnetic interference, and so on. [10a,14] However, a more specific summary focuses on the rechargeable batteries is required and beneficial for the researchers working on nextgeneration batteries. Moreover, the study and investigation on MXenes for other EES systems beyond LIB are rapidly developing and have achieved great progress very recently. For example, great research efforts have been invested in exploring the application of MXenes in Li-sulfur batteries Research on next-generation battery technologies (beyond Li-ion batteries, or LIBs) has been accelerating over the past few years. A key challenge for these emerging batteries has been the lack of suitable electrode materials, which severely limits their further developments. MXenes, a new class of 2D transition metal carbides, carbonitrides, and nitrides, are proposed as electrode materials for these emerging batteries due to several desirable attributes. These attributes include large a...