  Lithium-intercalated layered 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, are poorly managed or even understood yet. Here, for the first
time, we employ quantum calculations including high-order lattice anharmonicity
and find that the thermal conductivity k of LixTMO2 materials is significantly
lower than hitherto believed. More specifically, the theoretical upper limit of
k of LiCoO2 is 6 W/m-K, 2-6 times lower than the prior theoretical predictions.
Delithiation further reduces k by 40-70% for LiCoO2 and LiNbO2. Grain
boundaries, strains, and porosity are yet additional causes of
thermal-conductivity reduction, while Li-ion diffusion and electrical transport
are found to have only a minor effect on phonon thermal transport. 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.
