Heterointerface effects in the electro-intercalation of van der Waals heterostructures

摘要

Molecular-scale manipulation of electronic/ionic charge accumulation inmaterials is a preeminent challenge, particularly in electrochemical energystorage. Layered van der Waals (vdW) crystals exemplify a diverse family ofmaterials that permit ions to reversibly associate with a host atomic latticeby intercalation into interlamellar gaps. Motivated principally by the searchfor high-capacity battery anodes, ion intercalation in composites of vdWmaterials is a subject of intense study. Yet the precise role and ability ofheterolayers to modify intercalation reactions remains elusive. Previousstudies of vdW hybrids represented ensemble measurements at macroscopic filmsor powders, which do not permit the isolation and investigation of thechemistry at 2-dimensional (2D) interfaces individually. Here, we demonstratethe electro-intercalation of lithium at the level of individual atomicinterfaces of dissimilar vdW layers. Electrochemical devices based on vdWheterostructures comprised of deterministically stacked hexagonal boronnitride, graphene (G) and molybdenum dichalcogenide (MoCh2; Ch = S, Se) layersare fabricated, enabling the direct resolution of intermediate stages in theintercalation of discrete heterointerfaces and the extent of charge transfer toindividual layers. Operando magnetoresistance and optical spectroscopy coupledwith low-temperature quantum magneto-oscillation measurements show that thecreation of intimate vdW heterointerfaces between G and MoCh2 engenders over10-fold accumulation of charge in MoCh2 compared to MoCh2/MoCh2 homointerfaces,while enforcing a ca. 0.5 V more negative intercalation potential than that ofbulk MoCh2. Beyond energy storage, our new experimental methodology tomanipulate and characterize the electrochemical behavior of layered systemsopens up novel approaches to controlling the charge density in 2D(opto)electronic devices.