A simple approach for superior performance of lithium/sulphur batteries modified with a gel polymer electrolyte

Abstract

A gel polymer electrolyte (GPE) is superior to a liquid electrolyte in reducing electrolyte leakage and flammability for the safety of rechargeable batteries. However, using GPE in lithium/sulphur (Li/S) batteries reduces the capacity because the highly viscous GPE traps lithium polysulfide (PS) within the electrolyte and makes the PS electrochemically inactive. In order to compensate for the loss of capacity, a porous poly(ethylene oxide)–sulphur composite has been selected to modify the commercial separator. It is shown that elemental sulphur in the composite layer not only serves as the pore-making agent (or called wetting agent) to facilitate filling of the liquid electrolyte in the cell assembly, but also provides additional sulphur to increase the cell's capacity. As a result, the Li/S cell with a GPE-modified separator has even higher capacity than the liquid electrolyte cell while still retaining the advantages of GPE. In this paper we discuss the effect of the composite's composition on the morphology, electrolyte wettability and cell's performance.