(25b) Invited: Exploring Electrochemical Reaction Dynamics of Li+-Solvation Structures with Large-Scale Quantum Mechanical Simulations

An intrinsic materials challenge in lithium–sulfur (Li-S) batteries is the dissolution of intermediate lithium polysulfides during lithiation and delithiation reactions of sulfur. The presence of polysulfides in the electrolyte leads to numerous problems including the loss of active species, redistribution of sulfur in the cathode, passivation/consumption of the lithium anode, and the notorious shuttling effect during delithiation. In this talk, I will present a variety of theoretical approaches that complement experimental findings for understanding the solvation properties of Li⁺ ions in a series of ether solvents (dimethoxyethane, diglyme, triglyme, tetraglyme, and 15-crown-5). Large-scale ab initio and classical molecular dynamics (MD) simulations predict Li⁺ ion solvation structures in excellent agreement with experimental evidence from electrospray ionization-mass spectroscopy. An excellent correlation is also established between the Li⁺-solvation binding energies from the ab initio MD simulations and the lithiation overpotentials obtained from galvanostatic intermittent titration techniques (GITT).¹ These findings convincingly indicate that a stronger solvation binding energy imposes a higher lithiation overpotential of sulfur in subnano confinement. Finally, I will present a new large-scale quantum mechanical simulation tool that will enable future calculations and a detailed understanding of solvated chemical systems. The mechanistic understanding enabled by these large-scale simulations provides invaluable guidance in designing future electrolytes and electrodes for controlling complex electrochemical reactions.

¹Chengyin Fu, Lihua Xu, Fredy W. Aquino, Arthur v. Cresce, Mallory Gobet, Steven G. Greenbaum, Kang Xu, Bryan M. Wong, and Juchen Guo
“Correlating Li+-Solvation Structure and Its Electrochemical Reaction Kinetics with Sulfur in Subnano Confinement.”
Journal of Physical Chemistry Letters, 9, 1739 (2018)