Ion-selective PEDOT:PSS-decorated separator as a potential polysulfide immobilizer for lithium-sulfur batteries

Abstract

PEDOT:PSS is one of the most investigated and broadly exploited conducting polymers with extensive applications. In this work, we present lithiated PEDOT:PSS-coated Celgard (Li+-PEDOT:PSS@CG) separator for Li-S battery to alleviate the so-called shuttle effect, which is alleged to be a major bottleneck in Li-S chemistry. The Li+-PEDOT:PSS@CG separator possesses a dual role, concurrently inhibit polysulfide shuttling and promote Li+ selective diffusion. The negatively charged sulfonic acid groups present in PSS function as an electrostatic screen towards the soluble higher order polysulfides via coulombic repulsion, whereas the strong electronegative atoms (O and S) present in PEDOT render chemical interactions and form a chelated coordination structure with insoluble lithium sulfides. The dual shielding effect proffered by Li+-PEDOT:PSS@CG effectively suppresses the polysulfide shuttling process by arresting the migrating polysulfides within the cathode compartment of the cell. Furthermore, the Li+-PEDOT:PSS@CG membrane holds excellent electrolyte wettability, ionic conductivity and interfacial properties. The Li-S cell containing Li+-PEDOT:PSS@CG separator unveiled substantial improvement in the electrochemical performance, suppressed polysulfide shuttling and anti-self-discharge properties. The cell displays an initial discharge capacity of 1096 mAh g−1 at 0.5C, and a capacity retention of 911 mAh g−1 over 500 cycles with an areal sulfur loading of 4.1 mg cm−2.