Phonon transport in lithiated graphene–copper heterostructures: Intertwined thermal and electrochemical properties

Effective thermal management is crucial for maintaining the efficiency and reliability of lithium-ion batteries (LIBs), which requires a comprehensive understanding of the intertwined phonon thermal transport and electrochemical processes occurring in the battery electrode materials. This work leverages density functional theory and machine-learning interatomic potentials to investigate and compare the phonon thermal transport and electrochemical properties of lithiated graphene monolayers and graphene–copper (Cu) heterostructures. The graphene–Cu heterostructure exhibits significantly reduced thermal conductivity compared to the graphene monolayer, originating from decreased phonon group velocities, shortened phonon lifetimes, increased anharmonicity as well as scattering phase space due to interlayer coupling. However, the diffusion energy barrier of Li ions over the graphene monolayer (0.3 eV) drops to 0.24 eV on the graphene top surface of the heterostructure and the Cu bottom surface has a substantially lower barrier of 0.04 eV, indicating enhanced electrochemical performance facilitated by strengthened adsorption energies. Additionally, lithiation further suppresses the thermal conductivity of the graphene monolayers and the graphene–Cu heterostructures with the top surface of the lithiated heterostructure depicts higher thermal conductivity than the bottom surface. These results reveal a fundamental trade-off between electrochemical enhancement and phonon-mediated heat transport, providing atomistic insights and design guidelines for optimizing graphene-based anodes and current–collector interfaces in next-generation LIBs.