Dynamic manipulation of thermal & structural properties using electrochemical & electrical stimuli

Beyond energy storage, ion insertion has emerged as an powerful method to dynamically tune the physical properties of materials[1]. While there have been numerous examples of electrochemical tuning of optical and electronic properties, the dynamic manipulation of thermal and structural properties is relatively less explored. I will first describe our efforts to create “thermal switches” – materials whose thermal conductivity can be tuned in real-time – using ion insertion. We show that the reversible intercalation of Li+ into the van der Waals gaps in MoS2 induces a ~8-10x modulation in the cross-plane thermal conductance[2], opening avenues for dynamic thermal management. Interestingly, we find that micron-scale heterogeneities in ion concentration can be imaged using spatially-resolved measurements of thermal conductance, suggesting that heat current measurements could enable operando microscopy in<br/>electrochemical systems. Next, I will briefly discuss how ion insertion can change the crystal structure and symmetry in layered crystals; in particular, we discover intriguing uniaxial in-plane lattice expansion caused by Li+ intercalation in WTe2, a finding that has potential applications in electrochemical actuators[3]. Finally, I will describe our recent efforts to visualize nanosecond-timescale and picometer-lengthscale structural dynamics in materials driven electrically[4]. Such ultrafast operando techniques could provide fundamental insights into field-induced intermediate states, metastable phases, and transport pathways in ionic systems.<br/><br/>[1] Nature Reviews Materials 6, 847 (2021), [2] Nature Communications 9, 4510 (2018), [3] Advanced Materials, 33, 2101875 (2021), [4] Science 373, 352 (2021)