Catalytic oxidation of Li2S on the surface of metal sulfides for Li-S batteries.

Zhou, Guangmin; Tian, Hongzhen; Jin, Yang; Tao, Xinyong; Liu, Bofei; Zhang, Rufan; Seh, Zhi Wei; Zhuo, Denys et al. · Proc Natl Acad Sci U S A · 2017

basic_science · Level V

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Abstract

Polysulfide binding and trapping to prevent dissolution into the electrolyte by a variety of materials has been well studied in Li-S batteries. Here we discover that some of those materials can play an important role as an activation catalyst to facilitate oxidation of the discharge product, Li<sub>2</sub>S, back to the charge product, sulfur. Combining theoretical calculations and experimental design, we select a series of metal sulfides as a model system to identify the key parameters in determining the energy barrier for Li<sub>2</sub>S oxidation and polysulfide adsorption. We demonstrate that the Li<sub>2</sub>S decomposition energy barrier is associated with the binding between isolated Li ions and the sulfur in sulfides; this is the main reason that sulfide materials can induce lower overpotential compared with commonly used carbon materials. Fundamental understanding of this reaction process is a crucial step toward rational design and screening of materials to achieve high reversible capacity and long cycle life in Li-S batteries.