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

5 years ago

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

Shangchao Lin, Jingui Yu, Mingchao Wang

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-Li_xS) governed by overcoordination sites, as well as the resulting strengthening effect of a-Li_xS 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-Li_xS under tensile loading. Based on a chemo-mechanical yield function, we confirm two-dimensionally nanoconfined lithiation reaction can facilitate the out-of-plane inelastic deformation (“reactive flow”) of a-Li_xS at a much lower level of biaxial stress. The atomistic understanding of lithiation behaviors of S cathodes provides fundamental insight into the optimal design of carbon-based S composite cathode with outstanding mechanical integrity, as well as the prediction of lithiation behavior of other electrode materials, such as silicon, metal oxides, and graphite.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b05446

DOI: 10.1021/acs.jpcc.7b05446