Unusually High Ion Conductivity in Large-Scale Patternable Two-Dimensional MoS₂ Film

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Advancing ion transport applications necessitates functional materials with high, stable, scalable, and micro-patternable ionic conductivity.
• Conventional solid ionic materials often exhibit limited conductivity, hindering device performance.

Purpose of the Study:

• To investigate the ionic conductivity of two-dimensional (2D) molybdenum disulfide (MoS2) nanofilms for various cations.
• To elucidate the ion transport mechanisms within these 2D materials.
• To explore the potential for fabricating scalable ionic devices using MoS2.

Main Methods:

• Fabrication of 2D MoS2 nanofilms with tunable thickness, down to a single atomic layer.
• Measurement of ionic conductivity for lithium (Li+), sodium (Na+), and potassium (K+) ions.
• Field-effect measurements to modulate ion transport.
• Modeling and analysis to understand ion transport mechanisms, including percolative ion channels.

Main Results:

• Achieved exceptionally high ionic conductivity exceeding 1 S/cm for Li+, Na+, and K+ in 2D MoS2 nanofilms, over two orders of magnitude higher than conventional materials.
• Identified mitigated activation energy via percolative ion channels, including 1D channels at grain boundaries, as the mechanism for high conductivity.
• Demonstrated field-effect modulation of ion transport with a high on/off ratio.
• Confirmed large-scale patternability of the ion channel using conventional lithography.

Conclusions:

• 2D MoS2 nanofilms exhibit superionic conductivity, offering a promising platform for next-generation ionic devices.
• The findings provide crucial insights into ion transport mechanisms in van der Waals materials.
• Facile and scalable device fabrication combined with superionic conductivity paves the way for practical applications.