Tunable Anisotropic Thermal Conductivity and Elastic Properties in Intercalated Graphite via Lithium Ions

Abstract

The electrochemical intercalation of metal ions into layered materials is a useful strategy to reversibly tune thermal-transport properties, but the fundamental mechanisms are not well understood. In this study, we systematically investigated the effects of lithium-ion concentrations on the anisotropic thermal conductivity of intercalated graphite by molecular-dynamics simulations and a continuum-mechanics method. It was found that the in-plane thermal conductivity rapidly decreased to 34.3% of that of graphite in the same direction when the lithium-ion concentration increases to 0.1667. However, the cross-plane thermal conductivity first decreased to 23.7% of that of the graphite. Then, it surprisingly recovered to a thermal conductivity even higher than that of graphite when the lithium-ion concentration increased further. These two different trends and thermal-conductivity anisotropies were explained by extracting the phonon lifetimes and elastic constants of intercalated graphites with various lithium-ion concentrations. At lithium-ion concentrations lower than 0.05, the reduction of both the in-plane and cross-plane thermal conductivities in the intercalated graphite was attributed to the increased phonon scattering owing to the interactions between the lattices and ions. However, at lithium concentrations higher than 0.05, the thermal transport of the intercalated graphite was mainly influenced by anisotropic elastic constants. The rapidly increasing cross-plane elastic constants increased the cross-plane thermal conductivity, while simultaneously weakening the phonon-focusing effects along the in-plane direction, which resulted in the opposite tendencies of the in-plane and cross-plane thermal conductivities with increasing lithium-ion concentrations. This study provides important guidance in the active regulation of the anisotropic thermal conductivities of layered materials for thermal management in energy storage and conversion.

Symmetry-driven phonon chirality and transport in one-dimensional and bulk Ba3N -derived materials

“…Similarly, the in-plane κ for bulk MoS 2 ranges from 85-112 Wm -1 K -1 [9,10], [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] times higher than the cross-plane values [11]. These weakly bonded structures provide avenues for tuning κ by varying layer number [9], applying strain [12,13] and intercalating atoms between layers [14][15][16].…”

Operando spatial mapping of lithium concentration using thermal-wave sensing

“…This phenomenon has been theoretically and experimentally investigated in various materials for the purpose of tuning thermal conductivity. [21][22][23][24][25][26] Here, focus will be given to previous studies of common electrode materials used in LIBs, i.e., lithium-intercalated graphite (Li x C 6 ) 21,22 and lithium-intercalated layered transition-metal oxides (Li x TMO 2 ), 23 especially Li x CoO 2 . 26 Prior molecular dynamics (MD) simulations predicted an anisotropic effect of lithium intercalation on the thermal conductivity of Li x C 6 , i.e., the in-plane k decreases monotonically with the degree of lithiation, whereas the through-plane k decreases first and then increases with the amount of intercalated Li + ions.…”

“…Another signal not exploited by the electrochemical community is the variation of thermal conductivity related to electrochemically induced structure/phase transitions. [21][22][23][24][25][26][27] Specifically, previous studies of lithium cobalt oxide 23,26 and graphite 21,22 demonstrated the dependence of the thermal conductivity of electrode materials on the degree of lithiation/delithiation. This suggests the possibility of determining the lithium concentration distribution in battery electrodes by spatially mapping their thermal conductivity.…”

Electrochemical Intercalation in Atomically Thin van der Waals Materials for Structural Phase Transition and Device Applications

“…Intercalation offers an effective methodology to tailor the thermal conductivity of 2D materials by changing the structural and compositional disorder, including changes in layer spacing, interaction strengths between adjacent layers and phase transitions. [ 78–83 ] Experimentally, there are a number of studies to reveal the effect of intercalation on thermal conductivity of 2D layered materials. As described above, the amounts of intercalated ions can be exactly controlled via electrochemical method, enabling the investigations of how disorder affects their thermal conductivity.…”