Improved electrochemical behavior of Li–S battery with functional WS2@PB–PPy–modified separator

Abstract

The Li–S battery is extremely attractive in electric vehicles and portable electronics owing to the ultrahigh theoretical energy density and reduced cost. Nevertheless, sulfur dissolves into polysulfide in the electrolyte and shuttles between the electrodes results in rapid capacity decay, thereby limits practical applications in energy storage. Herein, a simple coating method was proposed to introduce a WS2@PB11 Prussian blue (PB)–PPy22 Polypyrrole (PPy)–modified coating on the surface of the conventional polymer separator. The unparalleled composition of the WS2@PB–PPy layer can adequately inhibit the back and forth of polysulfides and the formation of inactive sulfur–related substances. Therefore, lithium ions can be transferred homogeneously inside the battery. Compared with those of batteries with pristine PP separators, the specific capacity and cycle stability are remarkably ameliorated for lithium-sulfur battery. This modified separator battery exhibits a raised specific capacity (1050 mAh g−1) and promoted capacity retention (650 mAh g−1 after 300 cycles) with coulombic efficiency more than 99.5% and capacity retention rate reaching 62%. It demonstrates that the three-layer porous as ions sieve structure indeed prevents the transfer of polysulfides through electrolyte to the anode and allows lithium-ion to pass through the separator. The rational design for the modified separator provides a trendy method to realize high-performance Li–S batteries.

Keywords

• Electrolyte separator
• Prussian blue
• WS2@PB–PPy layer
• Ionic selectivity
• Electrochemical properties
• Li–S battery