Enhancement of Interfacial Thermal Conductance in PEO/LiCoO₂ Solid-State Battery Interfaces via an Al₂O₃ Interlayer:...

Interfacial thermal resistance at the cathode-electrolyte contact constitutes a major limitation for thermal management in solid-state lithium batteries. In this work, reverse nonequilibrium molecular dynamics (RNEMD) simulations are employed to quantify heat transport across the interface between a lithium cobalt oxide (LiCoO₂) cathode and a poly(ethylene oxide) (PEO) solid electrolyte. For the direct PEO/LiCoO₂ interface, a pronounced temperature discontinuity is observed, corresponding to an interfacial thermal conductance of 164 MW m^-2 K^-1. Upon insertion of an amorphous Al₂O₃ interlayer, the effective interfacial thermal conductance increases to a lower-bound value of approximately 401 MW m^-2 K^-1. This behavior reflects a significant thermal resistance that arises from the mismatch of phonons and weak interfacial coupling. To mitigate this limitation, a thin amorphous alumina (Al₂O₃) interlayer is introduced at the interface. The presence of the alumina interlayer results in a nearly continuous temperature profile across the interface and leads to a substantial enhancement of interfacial heat transport, indicating a near elimination of the interfacial thermal resistance. The interfacial thermal conductance in the presence of the alumina interlayer remains high over the investigated temperature range of 250-400 K. Analysis of the vibrational density of states and radial distribution functions reveals that the alumina interlayer improves phonon spectral overlap and strengthens interfacial bonding, thereby facilitating more efficient energy transmission across the interface. These results demonstrate that ceramic interlayer engineering provides an effective strategy for improving interfacial thermal transport in solid-state battery architectures.