A comparative study on the solubility and stability of p-phenylenediamine-based organic redox couples for non-aqueous flow batteries

Hyun seung Kim, Keon Joon Lee, Young Kyu Han, Ji Heon Ryu, Seung M. Oh

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

A methyl-substituted p-phenylenediamine (PD), N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), is examined as a positive redox couple with high energy density for non-aqueous Li-flow batteries. Methyl substitution affects the solubility of the redox couple, as the solubility is increased by a factor of ten, to a maximum solubility of 5.0 M in 1.0 M lithium tetrafluoroborate-propylene carbonate supporting electrolyte due to elimination of the hydrogen bonding between the solute molecules. The methyl substitution also enhances the chemical stability of the cation radical and di-cation being generated from PD, as the redox center is shielded by the methyl groups. Furthermore, this organic redox couple demonstrate two-electron redox reactions at 3.2 and 3.8 V (vs. Li/Li+); therefore, the volumetric capacity is twice higher compared to conventional one-electron involved redox couples. In a non-flowing Li/TMPD coin-cell, this organic redox couple demonstrates very stable cycleability as a positive redox couple for non-aqueous flow batteries.

Original languageEnglish
Pages (from-to)264-269
Number of pages6
JournalJournal of Power Sources
Volume348
DOIs
StatePublished - 2017

Keywords

  • Chemical stability
  • Li-flow batteries
  • Non-aqueous electrolytes
  • Organic redox couples
  • Solubility

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