Metal–organic framework@SiO2 as permselective separator for lithium–sulfur batteries

Abstract

The shuttling of polysulfides between the electrodes in a lithium–sulfur battery (Li–S) system remains a challenge to be addressed in order to realize the full potential of this promising technology. In order to overcome this issue several strategies have been adopted. In the present work, UiO-66-NH₂@SiO₂ was successfully synthesized and coated on a commercial Celgard 2320 membrane. The coating of UiO-66-NH₂@SiO₂ on a Celgard 2320 membrane has not only enhanced the thermal stability and wettability but also other electrochemical properties such as ionic conductivity, compatibility and charge–discharge behavior. The Li–S cell with the UiO-66-NH₂@SiO₂-coated membrane delivered higher discharge capacity than the Li–S cell with SiO₂-coated and uncoated membranes. The enhanced discharge capacity was attributed to the electrostatic and/or H-bonding interactions between the polysulfide and UiO-66-NH₂@SiO₂ as evidenced by its positive zeta potential (+56.42 mV). More importantly, the permselective properties of the membrane significantly play against the self-discharge of Li–S cells in which 98.5% of its capacity was retained even after 40 h which is superior to earlier reports.