Cobalt(II) complexes with azole-pyridine type ligands for non-aqueous redox-flow batteries:tunable electrochemistry via structural modification

Armstrong, Craig G. and Toghill, Kathryn E. (2017) Cobalt(II) complexes with azole-pyridine type ligands for non-aqueous redox-flow batteries:tunable electrochemistry via structural modification. Journal of Power Sources, 349. pp. 121-129. ISSN 0378-7753

[img]
Preview
PDF (Armstrong and Toghill 2017 - JPS Manuscript first submission)
Armstrong_and_Toghill_2017_JPS_Manuscript_first_submission.pdf - Submitted Version
Available under License Creative Commons Attribution-NonCommercial-NoDerivs.

Download (1MB)
[img]
Preview
PDF (Armstrong and Toghill 2017 - JPS Manuscript with revisions)
Armstrong_and_Toghill_2017_JPS_Manuscript_with_revisions.pdf - Accepted Version
Available under License Creative Commons Attribution-NonCommercial-NoDerivs.

Download (2MB)

Abstract

Abstract A single species redox flow battery employing a new class of cobalt(II) complexes with ‘tunable’ tridentate azole-pyridine type ligands is reported. Four structures were synthesised and their electrochemical, physical and battery characteristics were investigated as a function of successive substitution of the ligand terminal pyridyl donors. The Co(II/I) and Co(III/II) couples are stable and quasi-reversible on gold and glassy carbon electrodes, however redox potentials are tunable allowing the cobalt potential difference to be preferentially increased from 1.07 to 1.91 V via pyridine substitution with weaker σ-donating/π-accepting 3,5-dimethylpyrazole groups. The charge-discharge properties of the system were evaluated using an H-type glass cell and graphite rod electrodes. The complexes delivered high Coulombic efficiencies of 89.7–99.8% and very good voltaic efficiencies of 70.3–81.0%. Consequently, energy efficiencies are high at 63.1–80.8%, marking an improvement on other similar non-aqueous systems. Modification of the ligands also improved solubility from 0.18 M to 0.50 M via pyridyl substitution with 3,5-dimethylpyrazole, though the low solubility of the complexes limits the overall energy capacity to between 2.58 and 12.80 W h L−1. Preliminary flow cell studies in a prototype flow cell are also demonstrated.

Item Type:
Journal Article
Journal or Publication Title:
Journal of Power Sources
Additional Information:
This is the author’s version of a work that was accepted for publication in Journal of Power Sources. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Power Sources, 349, 2017 DOI: 10.1016/j.jpowsour.2017.03.034
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2100/2105
Subjects:
ID Code:
85531
Deposited By:
Deposited On:
22 Mar 2017 09:18
Refereed?:
Yes
Published?:
Published
Last Modified:
22 Oct 2020 04:15