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

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.