Sulfur-Carbon Positive Electrode With Metal Oxide for Polysulfide Shuttling

The patent introduces a redox mediator (such as iron fluoride, cobalt fluoride, or their compounds) as an intermediary substance in the electrolyte. This mediator facilitates electron transfer between the positive and negative electrodes, enabling the sulfur-based positive electrode to function effectively while preventing polysulfide shuttling. The mediator acts as a bridge that allows the high-energy-density sulfur material to be used without suffering from the polysulfide dissolution problem, thus resolving the contradiction between energy density and lifetime characteristics.

The patent extracts the problematic polysulfide shuttling mechanism from the system by using a redox mediator that operates through a different chemical pathway. Instead of relying on direct sulfur-redox reactions that produce soluble polysulfides, the system uses the mediator's redox couple (e.g., Fe2+/Fe3+ or Co2+/Co3+) to transfer electrons, thereby eliminating the harmful polysulfide intermediate while maintaining the high energy density benefits of sulfur.

The redox mediator serves as an intermediary that enables electron transfer without requiring polysulfide adsorption. This eliminates the need for adsorbent materials that would otherwise be needed to suppress shuttling, but which would block active sites and reduce capacity. The mediator provides a alternative electron transfer pathway that maintains both high capacity and long lifetime.

The patent changes the fundamental reaction mechanism parameter from direct sulfur redox (producing polysulfides) to mediator-based redox (using soluble redox couples). This parameter change allows the system to achieve lifetime improvement through a different chemical pathway that does not consume active material, thereby maintaining high discharging capacity while extending battery lifetime.

The redox mediator is dissolved in the electrolyte rather than being incorporated into the solid positive electrode structure. This approach achieves lifetime improvement without complicating the electrode manufacturing process, as the mediator is simply added to the electrolyte solution during battery assembly, avoiding complex multi-step electrode fabrication procedures.

The patent extracts the functional additive from the solid electrode structure and places it in the liquid electrolyte phase. This extraction simplifies electrode manufacturing while achieving the same lifetime improvement effect, as the mediator in the electrolyte can freely access both electrodes without requiring complex electrode porosity or multi-layer structures.