ReaxFF: Teflon coating reduces Li-S battery electrolyte decomposition

Lithium released from the anode is a highly exothermic process in lithium-sulfur batteries, and as such can lead to reactions with the electrolyte. In a recent ReaxFF study, the lithium discharge from a single-walled carbon nanotube (SWCNT) composite electrode was studied, and indeed the hot lithium ions lead to many dissociation events, resulting in unwanted build up of ethylene. Coating the Li/SWCNT anode with a layer of porous Teflon, acting as a unreactive thermal buffer, leaves the electrolyte mainly intact and reduces the amount of ethylene formation by 90%.

These ReaxFF simulations give precious atomic-level insight in the fundamental processes at the electrode-electrolyte interface, which are necessary for further designing safer and longer-lived Li-S batteries.

ReaxFF simulation of anodic Li discharge

ReaxFF simulation results for Li-S battery cell with TEGDME electrolyte, with bare Li/SWCNT anode (top) and Teflon-coated Li/SWCNT anode (bottom). Left: snapshots at 10ps during the atomic discharge, right: local temperature profile at 1ps, just after discharge (blue 60 K, red >1000 K).

Links: ADF/ReaxFF overview, ReaxFF tutorials, Advanced 2-day ReaxFF workshop

Look at the web presentation to learn how to parametrize ReaxFF force fields with the MMC-SA optimizer.

ReaxFF, reactive dynamics, anodic discharge, dissociation

M. M. Islam, V. S. Bryantsev, and A. C. T. van Duin, ReaxFF Reactive Force Field Simulations on the Influence of Teflon on Electrolyte Decomposition during Li/SWCNT Anode Discharge in Lithium-Sulfur Batteries, J. Electrochem. Soc. 161, E3009-E3014 (2014).

Key concepts