New concepts in Redox Flow: “Impact of Redox-Active Polymer Molecular Weight on the Electrochemical Properties and Transport Across Porous Separators in Nonaqueous Solvents”

Simple porous Celgard separators allow ionic transport while rejecting redox-active polymer (RAP), thus avoiding crossover. Stirred flow cell demonstrates overall feasibility of approach using viologen RAP anolyte.

Scientific Achievement

  • Sized-based selective transport of supporting electrolyte across commercial Celgard porous separators is attainable by controlling the size of highly soluble (>2M) redox active polymers (RAPs) as storage material
  • Up to ~70x selectivity of transfer of supporting electrolyte vs RAPs achieved, with 93% RAP rejection by Celgard
  • Facile, quantitative electron transfer to viologen RAPs in solution; Cycling shows chemical stability
  • Stirred flow cell shows feasibility of overall approach

Significance and Impact

  • Strategy opens a new avenue for replacing the use of ionic-selective membranes for simpler and less expensive commercial off-the-shelf separators
  • Ionic conductivity could be significantly improved without sacrificing active component solubility or reactivity.
  • Fundamental understanding for “All-RAP” cell

Research Details

  • Synthesis and detailed electrochemical and transport characterization of viologen-based redox active polymers in LiBF4/acetonitrile electrolyte
  • Crossover and selectivity measurements of RAP vs. electrolyte
  • Stirred flow cell assembled and tested – active component cycled

Work performed at the University of Illinois at Urbana-Champaign (JCESR partner) by Gavvalapalli, N.; Hui, J.; Cheng, K.J.; Lichtenstein, T.; Shen, M.; Moore, J.S.; Rodriguez-Lopez, J. J. Am. Chem. Soc., 2014.

DOI: 10.1021/ja508482e

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