Theoretical Analysis of Carrier Ion Diffusion in Superconcentrated Electrolyte Solutions for Sodium-Ion Batteries

Superconcentrated
electrolyte solutions are receiving increasing
attention as a novel class of liquid electrolyte for secondary batteries
because of their unusual and favorable characteristics, which arise
from a unique solution structure with a very small number of free
solvent molecules. The present theoretical study investigates the
concentration dependence of the structural and dynamical properties
of these electrolyte solutions for Na-ion batteries using large-scale
quantum molecular dynamics simulations. Microscopic analysis of the
dynamical properties of Na+ ions reveals that ligand (solvent/anion)
exchange reactions, an alternative diffusion pathway for Na+ ions, are responsible for carrier ion diffusion in the superconcentrated
conditions.