A Highly Reversible Low-Cost Aqueous Sulfur–Manganese Redox Flow Battery

Redox flow batteries are promising energy storage technologies. Low-cost electrolytes are the prerequisites for large-scale energy storage applications. Herein, we describe an ultra-low-cost sulfur–manganese (S–Mn) redox flow battery coupling a Mn2+/MnO2(s) posolyte and polysulfide negolyte. In addition to the intrinsically low cost active materials, the polysulfide negolyte removes the long-unresolved metal dendrite issue of metal–Mn batteries (e.g., Zn–Mn2+/MnO2(s) batteries), enabling substantially improved cycling stability at a high areal capacity (50–100 mAh cm–2). Due to the low cost of both sulfur and manganese species, this system promises an ultralow electrolyte cost of $11.00 kWh–1 (based on achieved capacity). This work broadens the horizons of aqueous manganese-based batteries beyond metal–manganese chemistry and offers a practical route for low-cost and long-duration energy storage applications.