Competing Heat Carriers Leading to Distinctive Cation Concentration Dependent Thermal Conductivity of Amorphous Li_xS (x=0-2) Batteries

YF Gao and HZ Fan and YG Zhou and M Hu, ADVANCED FUNCTIONAL MATERIALS, 33 (2023).

DOI: 10.1002/adfm.202214501

Thermal transport in amorphous lithium-sulfur (a-LixS) is systematically investigated using molecular dynamics and the contributions from different types of heat carriers are quantitatively evaluated. In general, the thermal conductivity (TC) of a-LixS changes largely by varying the concentration (x) of Li ions in a-LixS. Interestingly, the TC of a-LixS shows three distinct regimes of dependence on Li concentration. For low Li concentration (x = 0.4-1.2), the TC grows slowly, followed by a rapid increase in TC for medium Li concentration (x = 1.2-1.6), where the growth rate is three times that of the first regime, and finally, the TC is independent of Li concentration (x = 1.6-2.0). The TC enhancement in the first and second regimes is mainly attributed to propagating and non-propagating vibrational modes in a-LixS, respectively. In contrast, the stable thermal transport regime is governed by the competition between propagating and non-propagating phonons. These investigations provide quantitative TC data of various polysulfides for shuttling analysis, and a fundamental understanding of the thermal transport mechanism of complex a-LixS structures, which is beneficial for the rational design of thermal management of Li-S batteries.

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