Development of High Area Loading and Stable Sulfur Electrode through Interface Functionality and Electrode Design for Lithium Sulfur Battery

Abstract

High area loading of sulfur is a critical parameter to achieve high energy-density Li-S battery. Interface properties between electrode and electrolyte play an important role in these batteries. Sulfur species dissolution, precipitation and phase transformation during the charge and discharge process strongly affect the performance of lithium sulfur (Li-S) batteries. In this work, we examine the chemical functionalities and electrode structures that are important to stabilize sulfur electrode. As an example, binders with different functionalities, which differs both in chemical and electrical properties, are employed to modify the interface between the conductive matrix and electrolyte. The phase transformation of sulfur species at this interface is studied in detail. Remarkable differences are observed among sulfur cathodes with different binders modified interface. More solid-phase sulfur species precipitation is observed with binders that have strong affiliate functional groups, like poly(9, 9-dioctylfluorene-co-fluorenone-co-methylbenzoic ester) (PFM) and poly(vinylpyrrolidone) (PVP), in both fully charged and discharged states. Also, the improved conductivity from introducing conductive binders greatly promotes sulfur species precipitation. These findings suggest that the contributions from functional groups affinity and binder conductivity lead to more sulfur transformation into the solid phase, so the shuttle effect can be greatly reduced, and higher sulfur area loading and better cycling stability can be obtained.