Fine structure and property of two-dimensional energy storage materials

<p indent="0mm">Two-dimensional materials possess unique atomic structures and electronic structures, rendering them significant in various fields. In the field of energy storage, two-dimensional materials have garnered considerable attention due to their interlayer and intralayer physical properties. The van der Waals interaction interlayer position is considered to be an ideal channel for ion transport. As for electrons, both interlayer and intralayer structural changes of two-dimensional materials can adjust its transport properties. However, in actual research and applications, it is found that two-dimensional materials have not fully shown their capabilities. The essence is derived from the complexity of the actual system, which leads to the fact that two-dimensional materials cannot store energy like a perfect model, but stack up during the working process, resulting in various defects and novel structures. Therefore, the research on the real structure of energy storage two-dimensional materials is very important, but there are many difficulties and deficiencies in the process of exploring and establishing its structure-property relationship, so the current knowledge of energy storage two-dimensional materials is still limited. The reasons for this situation lie in the limitations of structural analysis methods and the physical properties of 2D materials themselves. Transmission electron microscopy is one of the important methods to explore the local fine structure, but it is still difficult to analyze the fine structure at the picometer scale in the field of energy storage two-dimensional materials. Two-dimensional materials for energy storage have complex structures and are generally sensitive to high energy electron beams, which has caused many difficulties in sample preparation and characterization. Based on these problems, this review discusses the relationship between structures and properties of graphene and graphene-like materials, transition metal dichalcogenides and TMDs-like materials and MXene materials. By summarizing research of two-dimensional energy storage materials, we find great potential lies in the van der Waals interaction interlayers. However, in reality their performance is not as good as predicted in terms of cyclability, electron conductivity and mechanical properties. To solve these problems, structure-property relationship must be clarified which means not only macro-scale structures but also micro-scale structures and their structure evolution process in real time. Under this circumstance, we summarize the<italic> in-situ</italic> methods including biasing, heating, gas, liquid and stress; low dose and low damage methods including low-voltage STEM, cryo-EM method and iDPC. These methods have great potential to be used in two-dimensional materials research for acquiring fine structures. Furthermore, as for the characterization of high spatial resolution electronic structures, we look into the future of the orbital and spin structure characterization methods in the field of transmission electron microscopy. Convergent beam electron diffraction is a powerful method to map space charge distribution at nanometer scale, and spin polarized electron source together with magnetic field free objective lens could possibly be the solution for the characterization of high spatial resolution spin structures. At last, based on the semiconduction properties and energy storage abilities of two-dimensional materials, we provide a broad picture for future research of two-dimensional materials in terms of fine structure characterization and property control.