Intercalation of Layered Materials from Bulk to 2D

Abstract

Intercalation in few‐layer (2D) materials is a rapidly growing area of research to develop next‐generation energy‐storage and optoelectronic devices, including batteries, sensors, transistors, and electrically tunable displays. Identifying fundamental differences between intercalation in bulk and 2D materials will play a key role in developing functional devices. Herein, advances in few‐layer intercalation are addressed in the historical context of bulk intercalation. First, synthesis methods and structural properties are discussed, emphasizing electrochemical techniques, the mechanism of intercalation, and the formation of a solid‐electrolyte interphase. To address fundamental differences between bulk and 2D materials, scaling relationships describe how intercalation kinetics, structure, and electronic and optical properties depend on material thickness and lateral dimension. Here, diffusion rates, pseudocapacity, limits of staging, and electronic structure are compared for bulk and 2D materials. Next, the optoelectronic properties are summarized, focusing on charge transfer, conductivity, and electronic structure. For energy devices, opportunities also emerge to design van der Waals heterostructures with high capacities and excellent cycling performance. Initial studies of heterostructured electrodes are compared to state‐of‐the‐art battery materials. Finally, challenges and opportunities are presented for 2D materials in energy and optoelectronic applications, along with promising research directions in synthesis and characterization to engineer 2D materials for superior devices.

High-performance ultra-violet phototransistors based on CVT-grown high quality SnS2flakes

“…have been identied in the ultrathin limit, but most attention so far has been paid to layered transition metal dichalcogenides (TMDs). [4][5][6][7] Furthermore, graphene shows a zero-band gap which traditionally has limited its application in optoelectronic devices. 8 In addition, layered semiconducting TMDs with a general description of MX 2 (a metal atom, M ¼ Mo, W, Sn, etc.…”

Dimensionality Concept in Solid‐State Reactions: A Way to Control Synthesis of Functional Materials at the Nanoscale

“…Formation of MAl 2 X 2 out of MX 2 results in the 1D expansion of the solid‐state host in the direction normal to the layered structure. This mechanism is quite common for guest‐host systems [ 8 ] and highlights the importance of material edges in the process. In contrast, the edges are likely to play very little or no role in the co‐deposition process.…”

“…The concepts are related—transformations of low‐dimensional (and layered) compounds often being low‐dimensional chemical processes. We are particularly interested in 1D reactions, which are fairly ubiquitous—they can be highly useful with applications from batteries to superconductors to drug delivery [ 8 ] but also highly detrimental as in shrink‐swell processes in clay. The reactions proposed and implemented in the present work—leading from elemental X to binary MX 2 to ternary MA 2 X 2 —hold promise for synthesis of oriented nanomaterials with tailored functionalities; monolayer structures of MA 2 X 2 are particularly enticing, by analogy with their MX 2 counterparts.…”

“…[ 7 ] Numerous topotactic reactions exhibit a peculiar property—changes of different lattice parameters are of different orders of magnitude. [ 8–17 ] In physics, such a distinction between physical parameters would warrant new theoretical models and interpretations; in chemistry, we show that it leads to a novel way to control chemical reactivity.…”

“…[ 18 ] 1D reactions, conserving a face of the unit cell, are ubiquitous because this category embraces numerous intercalation processes [ 8 ] which are currently being explored for energy‐dense batteries, [ 19 ] production of nanoribbons, [ 20 ] synthesis of compounds with unusual stoichiometry, [ 21 ] etc. In 1D reactions of graphite, the increase of the interlayer distance serves as a key parameter in predicting the cyclability of the process [ 8 ] and controls the insertion of larger species such as Na + in Na‐ion batteries. [ 9 ] 1D lattice expansion promotes exfoliation of 2D layers.…”