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Title: 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 Tg 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 Tg we have managed for polyanions conducting Li+ is -60 °C. In contrast, polysiloxanes with PEO side chains and tetrabutylphosphonium cationic side groups have Tg ≈ -75 °C that barely increases with ion content, as anticipated by DFT. A survey of all polyanions in the literature suggests that Tg < -80 °C is needed to achieve the 10-4 S/cm conductivity needed for battery separators.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2]
  1. Pennsylvania State Univ., University Park, PA (United States)
  2. Univ. of Pennsylvania, Philadelphia, PA (United States)
Publication Date:
OSTI Identifier:
1171798
Report Number(s):
DE--FG02-07ER46409
DOE Contract Number:
FG02-07ER46409
Resource Type:
Technical Report
Research Org:
Pennsylvania State Univ., University Park, PA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE conduction mechanisms; ionomeric single-ion conductors