Sodium-ion batteries (NIBs) are considered as promising alternatives to lithium-ion batteries (LIBs) especially in large-scale energy storage systems of renewable energy owing to their potentially low production cost. In view of the larger ionic size of Na ions than Li ions, the commercial graphite anode in LIBs is not suitable for NIBs. To achieve NIBs with a high energy density, various anode materials have been studied in recent years. Among these, two-dimensional (2D) materials have attracted considerable attention on account of their unique 2D-layered structure with infinite planar lengths; these materials provide short paths for sodium-ion transportation and large surface areas for sodium ion adsorption. Furthermore, some 2D materials exhibit a high electronic conductivity (e.g. graphene and metal selenide), which also aids in increasing the capacity and enhancing the rate performance. This review provides an insight into the recent progress in 2D anode materials in NIBs, including graphene and its derivatives, transition metal sulfides/selenides, phosphorene/metal phosphides, transition metal carbides/nitrides (MXene), and other graphene-like elemental analogs (silicene, germanene, stanene, and borophene). Moreover, a series of in situ characterization techniques, which have been utilized to investigate the fundamental sodium storage mechanism of the aforementioned 2D anode materials, are explained in-depth in this paper. This review is focused on providing a pathway for comprehending the electrochemical properties and methods to study the sodium storage mechanism of 2D anode materials for further research.

钠离子电池（NIB）被认为是锂离子电池（LIB）的有前途的替代品，特别是在可再生能源的大规模储能系统中，由于其潜在的低生产成本。鉴于Na离子的离子尺寸大于Li离子，LIB中的商用石墨阳极不适用于NIB。为了获得具有高能量密度的NIB，近年来已经研究了各种阳极材料。其中，二维（2D）材料因其具有无限平面长度的独特2D层结构而备受关注。这些材料为钠离子的运输提供了短路径，为钠离子的吸附提供了较大的表面积。此外，某些2D材料具有较高的电子电导率（例如石墨烯和金属硒化物），这也有助于增加容量并提高费率性能。这篇综述提供了关于NIB中2D阳极材料的最新进展的见识，包括石墨烯及其衍生物，过渡金属硫化物/硒化物，磷/金属磷化物，过渡金属碳化物/氮化物（MXene）和其他类似石墨烯的元素类似物（硅烯，锗烯，锡烯和硼烷）。而且，一系列本文深入解释了原位表征技术，该技术已用于研究上述二维阳极材料的基本钠存储机理。这篇综述的重点是提供理解电化学性质的途径和研究二维阳极材料的钠存储机制的方法，以供进一步研究。