Lithium–Organic Nanocomposite Suspension for High-Energy-Density Redox Flow Batteries

Organic redox-active materials are promising for redox flow batteries (RFBs) owing to their inherent low-cost, vast abundance, and high structure tunability. However, many organic RFBs suffer from low energy density owing to low solubility. We demonstrate a facile lithium–organic nanocomposite suspension (LIONS) by melting solid organic materials into the void of carbon networks in the semisolid posolyte to achieve high-energy-density Li-RFBs. We demonstrate the first organic-based semisolid Li-RFBs using 10-methylphenothiazine (MPT), delivering a high volumetric capacity (55 Ah L–1) and energy density (190 Wh L–1) with high Coulombic efficiency (>98%) and cycling stability (>100 cycles). The demonstrated volumetric capacity is 8 fold that of the liquid-MPT RFB, achieving the highest energy density among Li–organic-based RFBs. LIONS is a universal approach to enable the use of low-solubility organic materials in RFBs, providing a new direction for all insoluble organic active material to achieve low-cost and high-energy-density RFBs.