Here we report a new redox-active
perylene bisimide (PBI)-polysulfide
(PS) gel that overcomes electronic charge-transport bottlenecks common
to lithium–sulfur (Li–S) hybrid redox flow batteries
designed for long-duration grid-scale energy storage applications.
PBI was identified as a supramolecular redox mediator for soluble
lithium polysulfides from a library of 85 polycyclic aromatic hydrocarbons
by using a high-throughput computational platform; furthermore, these
theoretical predictions were validated electrochemically. Challenging
conventional wisdom, we found that π-stacked PBI assemblies
were stable even in their reduced state through secondary interactions
between PBI nanofibers and Li<sub>2</sub>S<sub><i>n</i></sub>, which resulted in a redox-active, flowable 3-D gel network. The
influence of supramolecular charge-transporting PBI-PS gel networks
on Li–S battery performance was investigated in depth and revealed
enhanced sulfur utilization and rate performance (C/4 and C/8) at
a sulfur loading of 4 mg cm<sup>–2</sup> and energy density
of 44 Wh L<sup>–1</sup> in the absence of conductive carbon
additives
