Ionically cross-linked PEDOT:PSS as a multi-functional conductive binder for high-performance lithium–sulfur batteries

Abstract

Despite their very high theoretical specific capacity, lithium–sulfur (Li–S) batteries still face issues such as low sulfur utilization and poor long-term cycling stability due to the low conductivity of sulfur, lithium polysulfide shuttle effect and large volume change during discharge–charge processes. This work uses a novel multi-functional polymer binder, PEDOT:PSS-Mg²⁺, to address the above issues. First, PEDOT:PSS is a highly conductive polymer, which improves the conductivity of the cathode composite. Second, cross-linking of PEDOT:PSS with Mg²⁺ forms a robust network that is able to endure the drastic volume change of the cathode during discharge/charge. Third, the abundant oxygen atoms present in PEDOT:PSS strongly interact with lithium polysulfides to suppress the shuttle effect. Li–S batteries with this new binder showed high initial specific capacity of up to 1097 mA h g⁻¹ and high capacity retention of up to 74% after 250 cycles at 0.5C with a sulfur content of 70 wt% in the cathode, which are significant improvements compared with the corresponding Li–S batteries with a conventional PVDF binder. Additionally, preparation of the cathode material with this new binder uses water as the solvent, avoiding the use of toxic organic solvents such as N-methylpyrrolidone (NMP).