Intercalation of atoms, ions and molecules is a powerful tool for altering or tuning the properties — interlayer interactions, in-plane bonding configurations, Fermi-level energies, electronic band structures and spin–orbit coupling — of 2D materials. Intercalation can induce property changes in materials related to photonics, electronics, optoelectronics, thermoelectricity, magnetism, catalysis and energy storage, unlocking or improving the potential of 2D materials in present and future applications. In situ imaging and spectroscopy technologies are used to visualize and trace intercalation processes. These techniques provide the opportunity for deciphering important and often elusive intercalation dynamics, chemomechanics and mechanisms, such as the intercalation pathways, reversibility, uniformity and speed. In this Review, we discuss intercalation in 2D materials, beginning with a brief introduction of the intercalation strategies, then we look into the atomic and intrinsic effects of intercalation, followed by an overview of their in situ studies, and finally provide our outlook.

原子、离子和分子的插层是改变或调整二维材料特性（层间相互作用、面内键合构型、费米能级能量、电子能带结构和自旋轨道耦合）的强大工具。插层可以引起与光子学、电子学、光电子学、热电学、磁性、催化和能量存储相关的材料的性质变化，释放或提高二维材料在当前和未来应用中的潜力。原位成像和光谱技术用于可视化和追踪插层过程。这些技术为破译重要且往往难以捉摸的插层动力学、化学力学和机制提供了机会，例如插层路径、可逆性、均匀性和速度。在这篇综述中，我们讨论了二维材料中的插层，首先简要介绍了插层策略，然后研究了插层的原子效应和内在效应，随后概述了它们的原位研究，最后提出了我们的展望。