Abstract
The effects of the intercalated ion concentration on the cross-plane thermal conductivity and the thermal boundary conductance in the graphite/lithiated graphite interface are investigated from molecular dynamics simulations. At low ion concentration, the cross-plane thermal conductivity of the lithiated graphite is lower than that of the pristine graphite. However, as the intercalated ion concentration increases, the cross-plane thermal conductivity increases rapidly, even exceeding that of the pristine graphite at high ion concentration. By analyzing the variations of the cross-plane elastic constants and phonon dispersion relation with the intercalated ion concentration, it is found that the intercalated ions significantly increase the phonon irradiation heat flux along the cross-plane direction. Our study further shows that the variation of the intercalated ion concentrations can also modulate the thermal boundary conductance in the graphite/lithiated graphite interface. The non-equilibrium molecular dynamics simulations show that the thermal boundary conductance between graphite and lithiated graphite decreases as the lithiation level increases, which would worsen the thermal performance of Li-ion batteries. A one-dimensional atomic chain model is proposed to elaborate on how the effective spring stiffness of material influences the interfacial transmission of phonons with different frequencies. This work provides a quantitative calculation of the cross-plane thermal conductivity and thermal boundary conductance in intercalated graphite samples and is also extremely important for the thermal management and structural design of lithium-ion batteries.
Highlights
Graphite is a common engineering material, which is widely used in thermal management,1 battery,2 catalysis,3 and many other fields
Since graphite is formed by single graphene layers in the AB stacking mode, the thermal boundary conductance (TBC) between graphite and typical metals such as copper (Cu) and aluminum (Al) is only about 50 MW/m2 K at room temperature
When the concentration of the Li ion reaches x = 0.167, i.e., LiC6 sample, the cross-plane thermal conductivity even exceeds that of the pristine graphite
Summary
Graphite is a common engineering material, which is widely used in thermal management, battery, catalysis, and many other fields. In these applications, the thermal transport properties of graphite are extremely important. The graphite has a high thermal conductivity of ∼2000 W/m K along the in-plane direction, the weak van der Waals interactions between the layers limit its cross-plane thermal conductivity to only about 5.7 W/m K.5. Since graphite is formed by single graphene layers in the AB stacking mode, the thermal boundary conductance (TBC) between graphite and typical metals such as copper (Cu) and aluminum (Al) is only about 50 MW/m2 K at room temperature.. The low cross-plane thermal transport properties of graphite severely limit many practice applications The graphite has a high thermal conductivity of ∼2000 W/m K along the in-plane direction, the weak van der Waals interactions between the layers limit its cross-plane thermal conductivity to only about 5.7 W/m K.5 Since graphite is formed by single graphene layers in the AB stacking mode, the thermal boundary conductance (TBC) between graphite and typical metals such as copper (Cu) and aluminum (Al) is only about 50 MW/m2 K at room temperature. The low cross-plane thermal transport properties of graphite severely limit many practice applications
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