TY  - JOUR
AU  - Wettstein, Alina
AU  - Diddens, Diddo
AU  - Heuer, Andreas
TI  - Controlling Li + transport in ionic liquid electrolytes through salt content and anion asymmetry: a mechanistic understanding gained from molecular dynamics simulations
JO  - Physical chemistry, chemical physics
VL  - 24
IS  - 10
SN  - 1463-9076
CY  - Cambridge
PB  - RSC Publ.
M1  - FZJ-2024-02266
SP  - 6072 - 6086
PY  - 2022
N1  - Unterstützt durch den MWIDE Grant: “GrEEn” project (funding code: 313-W044A)
AB  - In this work, we report the results from molecular dynamics simulations of lithium salt-ionic liquid electrolytes (ILEs) based either on the symmetric bis[(trifluoromethyl)sulfonyl]imide (TFSI−) anion or its asymmetric analogue 2,2,2-(trifluoromethyl)sulfonyl-N-cyanoamide (TFSAM−). Relating lithium's coordination environment to anion mean residence times and diffusion constants confirms the remarkable transport behaviour of the TFSAM−-based ILEs that has been observed in recent experiments: for increased salt doping, the lithium ions must compete for the more attractive cyano over oxygen coordination and a fragmented landscape of solvation geometries emerges, in which lithium appears to be less strongly bound. We present a novel, yet statistically straightforward methodology to quantify the extent to which lithium and its solvation shell are dynamically coupled. By means of a Lithium Coupling Factor (LCF) we demonstrate that the shell anions do not constitute a stable lithium vehicle, which suggests for this electrolyte material the commonly termed “vehicular” lithium transport mechanism could be more aptly pictured as a correlated, flow-like motion of lithium and its neighbourhood. Our analysis elucidates two separate causes why lithium and shell dynamics progressively decouple with higher salt content: on the one hand, an increased sharing of anions between lithium limits the achievable LCF of individual lithium-anion pairs. On the other hand, weaker binding configurations naturally entail a lower dynamic stability of the lithium-anion complex, which is particularly relevant for the TFSAM−-containing ILEs.
LB  - PUB:(DE-HGF)16
C6  - 35212346
UR  - <Go to ISI:>//WOS:000760909900001
DO  - DOI:10.1039/D1CP04830A
UR  - https://juser.fz-juelich.de/record/1024592
ER  -