Main content area

Thermodynamic and Mechanical Stability of Crystalline Phases of Li₂S₂

Guo, Qing, Lau, Kah Chun, Pandey, Ravindra
Journal of physical chemistry 2019 v.123 no.8 pp. 4674-4681
anisotropy, batteries, cathodes, chemical bonding, density functional theory, modulus of elasticity, thermodynamics, van der Waals forces
In lithium–sulfur (Li–S) battery, Li₂S₂ is one of the key intermediate products which may exist as an insoluble solid in a battery system. In this article, the low-energy crystalline phases of Li₂S₂ are investigated using density functional theory coupled with the van der Waals correction terms. The calculated results find that the tetragonal, triclinic, and hexagonal phases of Li₂S₂ phases are thermodynamically stable with the preference for the hexagonal phase to be the ground state. The low-energy Li₂S₂ phases also exhibit highly anisotropic elastic properties which can be attributed to the unique S–S bond orientations in their lattices. We believe that the elastic modulus in Li–S solids can be properly tuned if the S–S bonds orientation and distribution can be controlled during the synthesis process, which may be helpful for the development of functionalized cathode in the Li–S battery.