Origins of the Ultra-Low Thermal Conductivity of Lithium Intercalation Materials

Lithium-intercalated transition-metal oxides, LixTMO2, brought about a paradigm change in rechargeable batteries in recent decades and show promise for use in memristors, a type of device for future neural computing and on-chip storage. Thermal transport properties, although being a crucial element in limiting the charging/discharging rate, package density, energy efficiency, and safety of batteries as well as the controllability and energy consumption of memristors, pose serious challenges to theoretical understanding because of the limited capabilities of first-principles simulations. Here, for the first time, we accurately quantify the ultra-low thermal conductivity k of LixTMO2 materials and its physical origins, by including high-order anharmonicity. We find remarkably strong impact on k reduction by four-phonon scattering, delithiation (charging), grain boundaries, and strain. The results elucidate several long-standing issues regarding the thermal transport in lithium-intercalated materials and provide guidance toward designing high-energy-density batteries and controllable memristors.