Modulating the electrochemical intercalation of graphene interfaces with $\alpha$-RuCl$_3$ as a solid-state electron acceptor

TL;DR

This study shows how the charge transfer between graphene and $$-RuCl$_3$ can be used to control lithium ion intercalation in graphene-based heterostructures, with potential applications in tuning electrochemical properties of 2D materials.

Contribution

It introduces a method to modulate electrochemical intercalation in 2D heterostructures using charge transfer effects from $$-RuCl$_3$, tunable by spacer layer thickness.

Findings

Charge transfer from $$-RuCl$_3$ enhances Li intercalation in graphene.

Intercalation potential can be tuned by varying hBN spacer thickness.

Charge transfer effects are supported by Raman spectroscopy, transport measurements, and DFT calculations.

Abstract

Intercalation reactions modify the charge density in van der Waals (vdW) materials through coupled electronic-ionic charge accumulation, and are susceptible to modulation by interlayer hybridization in vdW heterostructures. Here, we demonstrate that charge transfer between graphene and $\alpha$-RuCl$_3$, which dopes the graphene positively, greatly favors the intercalation of lithium ions into graphene-based vdW heterostructures. We systematically tune this effect on Li$^+$ ion intercalation, modulating the intercalation potential, by using varying thicknesses of hexagonal boron nitride (hBN) as spacer layers between graphene and $\alpha$-RuCl$_3$. Confocal Raman spectroscopy and electronic transport measurements are used to monitor electrochemical intercalation and density functional theory computations help quantify charge transfer to both $\alpha$-RuCl$_3$ and graphene upon Li intercalation. This work demonstrates a versatile approach for systematically modulating the electrochemical intercalation behavior of two-dimensional layers akin to electron donating/withdrawing substituent effects used to tune molecular redox potentials.