Lithium-sulfur batteries are a promising new battery technology because of the high theoretical capacity and low cost of sulfur. The discharged product of the sulfur cathode, Li2S, is insoluble in typical battery electrolyte and is electronically insulating. Because of this, deposition of conformal coatings of Li2S onto the current collector hinders electron transport and prematurely ends discharge before complete utilization of sulfur’s capacity. Aided by a high-throughput computational platform, we have developed the first redox mediator for Li-S batteries. The redox mediator promotes the deposition of Li2S in a porous 3-dimensional morphology during cell discharge. With the redox mediator present, cell capacity is increased substantially due to increased in Li2S deposition, compared to cells without redox mediator. Kinetics of Li2S formation were studied under potentiostatic conditions and modeled with a modified Avrami equation, showing that the redox mediator delays impingement of Li2S islands on the current collector.

Redox mediators control electrodeposition of Li2S in lithium-sulfur batteries

251st National Meeting (2016)

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