Understanding glass fiber membrane used as a novel separator for lithium-sulfur batteries

Glass fiber (GF) membrane is evaluated as a potential separator for lithium-sulfur batteries. It is found that GF membrane has a highly porous structure with superior thermal stability, resulting in high liquid electrolyte uptake and enhanced electrochemical performance. Li-S cells using GF membrane as the separator can retain a capacity of 617 mA h g^-1 after 100 cycles at a current density of 0.2 C, which is 42% higher than that of cells using commercial microporous polypropylene separator. During rate capability tests, the capacity of Li-S cells using GF membrane decreases slowly from the reversible capacity of 616 mA h g^-1 at 0.2C to 505, 394 and 262 mA h g^-1 at 0.5C, 1C, and 2C, respectively. It should be noted that these cells can still deliver a high capacity of 587 mA h g^-1 with a high retention of 95% when the current density is lowered back to 0.2 C. The improved cycling and rate performance are ascribed to the fact that the highly porous GF membrane can increase the intake of soluble polysulfide intermediates and slow down their rapid diffusion to the Li anode side, which can not only improve the utilization of active material, but help protect the Li anode surface as well.