The impact of polymeric binder on the morphology and performances of sulfur electrodes in lithium-sulfur batteries

Abstract In this research work, three different polymers LiPAA, PVDF, and PEO were used as polymeric binders for the sulfur electrodes in Li-S cells. All electrodes had a high sulfur, loading ∼ 4.0 mg per cm2. The coin-cells were characterized by EIS and tested by constant current cycling and cyclic voltammetry using a standard electrolytic solution of LiTFSI in an ether mixture with LiNO3 as additive. The cycled sulfur electrodes were characterized by post-mortem SEM and N2 -sorption and compared to the pristine states. LiPAA-based cells showed the highest reproducibility of the electrochemical performances, the most limited specific capacity fading (at least twice smaller), and the better rate capability compared to PVDF- and PEO-based cells. The electrochemical data agreed with the post-mortem analyses of the different electrodes. The pristine electrodes showed similar morphologies and porosities independent of the polymeric binder used. Dramatic changes were observed for the PEO- and PVDF-based sulfur electrodes, in which a new dense morphology appeared after two and thirty cycles, respectively. Both PEO- and PVDF-based cycled electrodes were prone to delaminate from the current collector. In comparison, the morphology of the LiPAA-based sulfur electrodes remained mostly unchanged even after thirty cycles and no delamination behavior could be observed.