Anisotropic Tuning of Graphite Thermal Conductivity by Lithium Intercalation.
Understanding thermal transport in lithium intercalated layered materials is not only important for managing heat generation and dissipation in lithium ion batteries but also the understanding potentially provides a novel way to design materials with reversibly tunable thermal conductivity. In this work, the thermal conductivity of lithium-graphite intercalation compounds (LixC6) is calculated using molecular dynamics simulations as a function of the amount of lithium intercalated. We found that intercalation of lithium has an anisotropic effect on tuning the thermal conductivity: the thermal conductivity in the basal plane decreases monotonically from 1232 W/m·K of pristine graphite to 444 W/m·K of the fully lithiated LiC6, while the thermal conductivity along the c-axis decreases first from 6.5 W/m·K for graphite to 1.3 W/m·K for LiC18and then increases to 5.0 W/m·K for LiC6as the lithium composition increases. More importantly, we provide the very first atomic-scale insight into the effect of lithium intercalation on the spectral phonon properties of graphite. The intercalated lithium ions are found to suppress the phonon lifetime and to reduce the group velocity of phonons parallel to the basal plane but significantly to increase the phonon group velocity along the c-axis, which anisotropically tunes the thermal conductivity of lithiated graphite compounds. This work could shed some light on the search for tunable thermal conductivity materials and might have strong impacts on the thermal management of lithium ion batteries.
Department of Mechanical Engineering & Materials Science and Engineering Program, University of Colorado , Boulder, Colorado 80309-0427, United States.
Xin
X
Qian
Department of Mechanical Engineering & Materials Science and Engineering Program, University of Colorado , Boulder, Colorado 80309-0427, United States.
Xiaokun
X
Gu
Department of Electrical Engineering and Computer Science and Department of Physics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
Mildred S
MS
Dresselhaus
Department of Mechanical Engineering & Materials Science and Engineering Program, University of Colorado , Boulder, Colorado 80309-0427, United States.
Ronggui
R
Yang