Theory and Simulations of Ionic Liquids in Nanoconfinement

Svyatoslav Kondrat*, Guang Feng*, Fernando Bresme*, Michael Urbakh*, Alexei A. Kornyshev*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

35 Scopus citations

Abstract

Room-temperature ionic liquids (RTILs) have exciting properties such as nonvolatility, large electrochemical windows, and remarkable variety, drawing much interest in energy storage, gating, electrocatalysis, tunable lubrication, and other applications. Confined RTILs appear in various situations, for instance, in pores of nanostructured electrodes of supercapacitors and batteries, as such electrodes increase the contact area with RTILs and enhance the total capacitance and stored energy, between crossed cylinders in surface force balance experiments, between a tip and a sample in atomic force microscopy, and between sliding surfaces in tribology experiments, where RTILs act as lubricants. The properties and functioning of RTILs in confinement, especially nanoconfinement, result in fascinating structural and dynamic phenomena, including layering, overscreening and crowding, nanoscale capillary freezing, quantized and electrotunable friction, and superionic state. This review offers a comprehensive analysis of the fundamental physical phenomena controlling the properties of such systems and the current state-of-the-art theoretical and simulation approaches developed for their description. We discuss these approaches sequentially by increasing atomistic complexity, paying particular attention to new physical phenomena emerging in nanoscale confinement. This review covers theoretical models, most of which are based on mapping the problems on pertinent statistical mechanics models with exact analytical solutions, allowing systematic analysis and new physical insights to develop more easily. We also describe a classical density functional theory, which offers a reliable and computationally inexpensive tool to account for some microscopic details and correlations that simplified models often fail to consider. Molecular simulations play a vital role in studying confined ionic liquids, enabling deep microscopic insights otherwise unavailable to researchers. We describe the basics of various simulation approaches and discuss their challenges and applicability to specific problems, focusing on RTIL structure in cylindrical and slit confinement and how it relates to friction and capacitive and dynamic properties of confined ions.

Original languageEnglish
Pages (from-to)6668-6715
Number of pages48
JournalChemical Reviews
Volume123
Issue number10
DOIs
StatePublished - 24 May 2023

Funding

FundersFunder number
Engineering and Physical Sciences Research CouncilEP/P020194/1, EP/H004319/1, EP/T022213/1
Leverhulme TrustRPG-2016-223
National Natural Science Foundation of China52161135104
Huazhong University of Science and Technology
Natural Science Foundation of Hubei Province2020CFA093
Israel Science Foundation1141/18
Narodowe Centrum Nauki2020/39/I/ST3/02199, 2021/40/Q/ST4/00160

    Fingerprint

    Dive into the research topics of 'Theory and Simulations of Ionic Liquids in Nanoconfinement'. Together they form a unique fingerprint.

    Cite this