Lithium-sulfur (Li-S) battery is a promising energy storage system due to its high energy density [1-6]. A typical Li-S battery operation includes multi-step electrochemical reactions and transport phenomena relevant to the “internal shuttle effect”. The insoluble final product, such as Li₂S, can passivate the active cathode surface, block mass transfer channels and induce mechanical degradation, all of which negatively impact the cell performance. Each of these phenomena takes place at different spatial and temporal scales which necessitates a mesoscale approach to understand the implications of physicochemical coupling.

In this regard, a coupled mesoscale model has been developed in order to study physicochemical interactions in the cathode microstructure. At the interface level, the mechanism of chemical interactions between discharge products and cathode surface is fundamentally investigated. The growth rates of precipitation thickness and coverage are predicted. At the cathode microstructure level, the surface passivation and pore blockage induced by Li₂S precipitation are systematically studied. At the cell level, the mechanisms of discharge capacity loss are revealed.

In summary, this mesoscale modeling framework can be employed to quantify the capacity loss due to the internal shuttle effect and other electrochemical degradation mechanisms and understand the effect of cathode microstructure (i. e. sulfur loading, specific surface area, pore size distribution) on the electrochemical performance.

Acknowledgement:

Financial support from the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, grant DE-EE0006832 (Program manager: Tien Duong) is gratefully acknowledged.

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