title: Enhancing Cation Diffusion and Suppressing Anion Diffusion via Lewis-Acidic Polymer Electrolytes.
abstract: Solid polymer electrolytes (SPEs) have the potential to increase both the energy density and stability of lithium-based batteries, but low Li+conductivity remains a barrier to technological viability. SPEs are designed to maximize Li+diffusivity relative to the anion while maintaining sufficient salt solubility. It is thus remarkable that poly(ethylene oxide) (PEO), the most widely used SPE, exhibits Li+diffusivity that is an order of magnitude smaller than that of typical counterions at moderate salt concentrations. We show that Lewis-basic polymers like PEO favor slow cation and rapid anion diffusion, while this relationship can be reversed in Lewis-acidic polymers. Using molecular dynamics, polyboranes are identified that achieve up to 10-fold increases in Li+diffusivities and significant decreases in anion diffusivities, relative to PEO in the dilute-ion regime. These results illustrate a general principle for increasing Li+diffusivity and transference number with chemistries that exhibit weaker cation and stronger anion coordination.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology Pasadena , California 91125, United States.
authors.forename: Brett M
authors.initials: BM
authors.lastname: Savoie
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology Pasadena , California 91125, United States.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Webb
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology Pasadena , California 91125, United States.
authors.forename: Thomas F
authors.identifier: http://orcid.org/0000-0002-1882-5380
authors.initials: TF
authors.lastname: Miller