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Runt, James

Publications and source records attributed to Runt, James.

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Conduction Mechanisms and Structure of Ionomeric Single-Ion Conductors

Our team has designed using DFT (Gaussian) and synthesized low glass transition temperature single-ion conductors that are either polyanions that conduct small cations Li + , Na + , Cs + or polycations that conduct small anions F - , OH - , Br - . We utilize a wide range of complimentary experimental materials characterization tools to understand ion transport; differential scanning calorimetry, dielectric relaxation spectroscopy, infrared spectroscopy, nuclear magnetic resonance spectroscopy, linear viscoelasticity, X-ray scattering and molecular dynamics simulations. The glass transition temperature T g needs to be as low as possible to facilitate ion transport, so the nonionic parts of the polymer need to be polar, flexible and have strong solvation interactions with the ions. The lowest T g we have managed for polyanions conducting Li + is -60 °C. In contrast, polysiloxanes with PEO side chains and tetrabutylphosphonium cationic side groups have T g ≈ -75 °C that barely increases with ion content, as anticipated by DFT. A survey of all polyanions in the literature suggests that T g < -80 °C is needed to achieve the 10 -4 S/cm conductivity needed for battery separators.

36 MATERIALS SCIENCE↗