Enhanced stability and efficiency of 2-MAQ|Fc redox flow battery with a microemulsion electrolyte

Microemulsion-based redox flow batteries (RFBs) are gaining popularity due to the characteristics of microemulsions that decouple the solubility of redox species and ionic conductivity, affording a fantastic opportunity to simultaneously extend the electrochemical window and increase the ionic conductivity of electrolytes. In this work, we report a novel microemulsion-based RFB employing with 2-methylanthraquinone and ferrocene as anolyte and catholyte, respectively. Molecular dynamics and density function theory analysis investigated the electrochemical mechanism of redox species, including the intricate process of interface mass transport. The redox flow chemistry exhibits outstanding charge transfer rates and mass diffusion as well as good cycling stability under both cyclic voltammetry and linear sweep voltammetry. The flow cell demonstrated a coulombic efficiency of 96 %, voltage efficiency of 80 % and energy efficiency of 76.6 % after 300 cycles, making it one of the most stable and high-efficiency microemulsion-based RFBs reported so far. Although more advancement is still required to spark practical interest, this study opens a promising pathway to raise the energy density for redox flow batteries and is anticipated to inspire more in-depth studies of stable and high-efficient microemulsion-based RFBs.