Lithiation-Assisted Strengthening Effect and Reactive Flow in Bulk and Nanoconfined Sulfur Cathodes of Lithium–Sulfur Batteries

Abstract

Lithiation of electrode materials can lead to significant microstructural evolution and changes in their mechanical behaviors in lithium batteries. Lithium–sulfur (Li–S) batteries have recently attracted extensive attention, where carbon matrices have been utilized to retain S content by restricting the dissolution of polysulfide into electrolytes. Here we systematically investigate S cathode upon unconfined and nanoconfined lithiation using reactive molecular dynamics simulations. We demonstrate the great ductility of lithiated amorphous S cathode (a-LixS) governed by overcoordination sites, as well as the resulting strengthening effect of a-LixS due to the formation of stronger Li–S bonds upon lithiation. Fracture and cavitation studies also indicate the dominant role of shear banding, which is facilitated by overcoordinated S “plastic carriers”, in accommodating the plastic deformation of a-LixS under tensile loading. Based on a chemo-mechanical yield function, we confirm two-dimensionally nanoconfined...