Thianthrene polymers as 4 V-class organic mediators for redox targeting reaction with LiMn2O4 in flow batteries

Kan Hatakeyama-Sato; Karin Sadakuni; Kan Kitagawa; Kenichi Oyaizu

doi:10.1038/s41598-023-32506-7

Thianthrene polymers as 4 V-class organic mediators for redox targeting reaction with LiMn₂O₄ in flow batteries

Sci Rep. 2023 Apr 7;13(1):5711. doi: 10.1038/s41598-023-32506-7.

Authors

Kan Hatakeyama-Sato¹, Karin Sadakuni², Kan Kitagawa³, Kenichi Oyaizu⁴

Affiliations

¹ Department of Applied Chemistry, Waseda University, Tokyo, 169-8555, Japan. satokan@toki.waseda.jp.
² Department of Applied Chemistry, Waseda University, Tokyo, 169-8555, Japan.
³ Advanced Research and Innovation Center, DENSO CORPORATION, Aichi, 470-0111, Japan.
⁴ Department of Applied Chemistry, Waseda University, Tokyo, 169-8555, Japan. oyaizu@waseda.jp.

Abstract

Redox targeting reaction is an emerging idea for boosting the energy density of redox-flow batteries: mobile redox mediators transport electrical charges in the cells, whereas large-density electrode-active materials are fixed in tanks. This study reports 4 V-class organic polymer mediators using thianthrene derivatives as redox units. The higher potentials than conventional organic mediators (up to 3.8 V) enable charging LiMn₂O₄ as an inorganic cathode offering a large theoretical volumetric capacity of 500 Ah/L. Soluble or nanoparticle polymer design is beneficial for suppressing crossover reactions (ca. 3% after 300 h), simultaneously contributing to mediation reactions. The successful mediation cycles observed by repeated charging/discharging steps indicate the future capability of designing particle-based redox targeting systems with porous separators, benefiting from higher energy density and lower cost.