Understanding the electrochemical processes of SeS ₂ positive electrodes for developing high-performance non-aqueous lithium sulfur batteries

Abstract

SeS ₂ positive electrodes are promising components for the development of high-energy, non-aqueous lithium sulfur batteries. However, the (electro)chemical and structural evolution of this class of positive electrodes is not yet fully understood. Here, we use operando physicochemical measurements to elucidate the dissolution and deposition processes in the SeS ₂ positive electrodes during lithium sulfur cell charge and discharge. Our analysis of real-time imaging reveals the pivotal role of Se in the SeS ₂ nucleation process, while S enables selective depositions. During the initial discharge, SeS ₂ converts into Se and S separately, with the dissolved Se acting as nucleation sites due to their lower nucleation potential. The Se effectively catalyzes the growth of S particles, resulting in improved lithium sulfur battery performance compared to cells using positive electrodes containing only Se or S as active materials. By adjusting the Se-to-S ratio, we demonstrate that a low concentration of Se enables uniform catalytic sites, promotes the homogeneous distribution of S and favours improved lithium sulfur battery performance.

Abstract

SexSy is a promising positive electrode material for non-aqueous Li||chalcogen batteries. However, the behaviour of S and Se in the electrode is unclear. Here, the authors investigate the physicochemical phenomena of SexSy and the catalytic role of Se during battery testing.