Mesoscale Elucidation of Self-Discharge-Induced Performance Decay in Lithium-Sulfur Batteries

The polysulfide shuttle phenomenon substantially deteriorates the electrochemical performance of lithium-sulfur (Li-S) batteries, resulting in continued self-discharge and capacity fade during cycling. In this study, a mesoscale analysis is presented to explore the mechanisms of self-discharge behavior in the Li-S battery during the resting state. It is found that the self-discharge rate is determined by the sulfur solubility, desorption capability, diffusion kinetics, and reaction rate on the anode surface. Three regimes have been identified: desorption control, diffusion control, and charge transfer control. Correspondingly, strategies are suggested to increase the capacity retention, such as enhancing the binding of sulfur molecules to the host, reducing dissolved sulfur diffusivity, and improving the chemical stability of active materials with a Li metal anode. Furthermore, the use of an interlayer with high diffusion barriers can effectively suppress the self-discharge rate due to the confinement effect.