Electromechanical Origin of Phonon Dynamics Exhibiting Tunable Anisotropic Heat Transport in Layered Nanostructures

Abstract

Owing to the structural characteristics of 2D layered nanomaterials, anisotropic thermal conductivity is considered an attractive design factor for constructing efficient heat-transfer pathways. In this study, the electromechanical origin of anisotropic thermal conduction in Ti3C2O2M (M = Li, Na, K) is investigated at the atomic scale using theoretical multiscale analysis. The results demonstrate that the acoustic and optical phonon modes drive interlayer and intralayer heat conduction, respectively. Further, the lower the atomic number of the alkali ions intercalated in the Ti3C2O2 layer, the more immediately it responds to externally applied oscillations owing to its low inertia and high electrostatic force. The Li-ion layer exhibits an instantaneous response to vibrational excitations from an external source, making it transparent to higher phonon modes under interlayer and intralayer thermal conduction. The electromechanical modulation properties of the ion layer are further elucidated, providing practical insights into the design of anisotropic thermal paths. Activation of phonon modes allowed by the ion layer is explored to understand the tunable anisotropic thermal transportation of layered MXene. Interlayer and intralayer phonon transport characteristics of MXene are corrected by electromechanical perturbation of the alkali ion layer. The results provide a theoretical foundation for maximizing the potential of MXene layered materials in the thermal pathway design.image