An Inverse Vulcanized Polymer Cathode Functionalized with Quaternary Ammonium Salt for Enhanced Performance in Lithium–Sulfur Batteries

Abstract

Lithium–sulfur (Li–S) batteries are present as a promising energy storage system. Inhibiting the polysulfide shuttle effect is one of the most important research goals for the practical application of Li–S batteries. The introduction of organic functional groups to the sulfur cathode via inverse vulcanization has been an effective strategy to improve its properties and, in turn, the performance in Li–S batteries. In this report, an inverse vulcanized polymer (IVP) containing a tailor-designed quaternary ammonium salt named poly(S-r-TAEAB) was synthesized and integrated into the cathode of Li–S batteries. Systematic studies were conducted with the poly(S-r-TAEAB) cathode as well as the traditional sulfur and the IVP cathode, which only possess tertiary amine functional groups. Poly(S-r-TAEAB) reduces lithium polysulfide dissolution through the covalent bonding of sulfur atoms to the carbon framework. Importantly, the poly(S-r-TAEAB) cathode was demonstrated to adsorb lithium polysulfides, further suppressing the shuttle effect. The presence of the quaternary ammonium salt in the poly(S-r-TAEAB) was found to be critical for the acceleration of sulfur redox kinetics, fast Li-ion diffusion, favorable electrode/electrolyte interface, and improved mechanical properties. Due to these features, the poly(S-r-TAEAB) cathode exhibited significantly higher capacity retention over 100 cycles and enhanced rate performance compared with the traditional sulfur cathode.