Nonequilibrium molecular dynamics study of thermal conductivity and interfacial thermal resistance in Li(Ni,Mn,Co)O2 cathodes and Li7La3Zr2O12 solid electrolytes

Thermal transport across cathode–electrolyte stacks critically affects temperature rise and thermal safety in all-solid-state lithium-ion batteries, but quantitative benchmarks for Li(Ni,Mn,Co)O2 (NMC)/Li7La3Zr2O12 (LLZO) remain scarce. Here, we perform nonequilibrium molecular dynamics simulations to evaluate the lattice thermal conductivity of layered NMC with varying transition-metal ratios and random cation distributions, compare representative NMC polymorphs (R3m, C2/m, and Fm-3m), and quantify grain-boundary as well as NMC/LLZO interfacial thermal resistance. At 300 K, the thermal conductivity of NMC ranges from 1.3 to 7.5 W·m−1·K−1 depending on composition and phase, whereas tetragonal LLZO and cubic doped LLZO exhibit weak temperature dependence, ∼1.3–1.5 W·m−1·K−1. Layered NMC phases are strongly anisotropic, while the rock-salt phase is nearly isotropic. The interfacial thermal resistance between different NMC phases is 1.3–17.6 × 10−11 m2·K·W−1, and the NMC/LLZO interfacial resistance is ∼3.05 × 10−10 m2·K·W−1. Analysis of the overlap of phonon density-of-states indicates that improved vibrational matching reduces the interfacial resistance. These results provide atomistic inputs for continuum thermal models and guide interface engineering for solid-state batteries.