Investigation of Solvent Type and Salt Addition in High Transference Number Nonaqueous Polyelectrolyte Solutions for Lithium Ion Batteries

Abstract

High Li+ transference number electrolytes have attracted recent interest as a means to improve the energy density and rate capabilities of current lithium ion batteries. Here the viscosity and transport properties of a sulfonated polysulfone/poly(ethylene glycol) copolymer that displays both high transference number and high conductivity when dissolved in dimethyl sulfoxide (DMSO) are investigated for the first time in a battery-relevant solvent of nearly equivalent dielectric constant: mixed ethylene carbonate (EC)/dimethyl carbonate (DMC). The addition of a binary salt to each solution is investigated as a means to improve conductivity, and the diffusion coefficient of each species is tracked by pulse field gradient nuclear magnetic resonance (PFG-NMR). Through the 7Li NMR peak width and quantum chemistry calculations of the dissociation constant, it is shown that although the two solvent systems have nearly equivalent dielectric constants, the conductivity and transference number of the EC/DMC solution...