A Self-Mediating Redox Flow Battery: High-Capacity Polychalcogenide-Based Redox Flow Battery Mediated by Inherently Present Redox Shuttles

We propose and demonstrate the concept of a selfmediating redox flow battery that employs inherently present redox shuttles to access charges stored in solid electrode materials without circulating solids. Soluble and inherently present polychalcogenides shuffle electrons between the stack and the tank without circulating sulfur/selenium particles. This strategy promises a high energy density provided by solid materials without circulating solids or using foreign redox mediators, which directly addresses the most critical challenges facing "semisolid" and "redox-targeting" approaches. The full electrochemical reactions are completed via combinations of electrochemical, comproportionation, and disproportionation reactions of inherently present polychalcogenides without circulating solids. A high degree of material utilization (<= 99%) and high volumetric capacities (1096-1268 Ah L-catholyte(-1)) are achieved. This concept can be widely applied to solid redox active materials that naturally exhibit soluble reaction intermediates such as sulfur, selenium, iodine, etc., demonstrating the promising potential of using selfmediation for efficient, high-energy, and low-cost energy storage applications.