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 α-RuCl3, which hole-dopes the graphene, 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 α-RuCl3. Confocal Raman spectroscopy and electronic transport measurements are used to monitor electrochemical intercalation, and density functional theory computations help quantify charge transfer to both α-RuCl3 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.
Keywords: 2D materials; electrochemistry; graphene; intercalation; α-RuCl3.