Scaled-up fabrication of porous-graphene-modified separators for high-capacity lithium–sulfur batteries

Lithium–sulfur battery is regarded as one of the most promising post-LIB technologies owing to its overwhelming advantage in energy density. However, the dissolution and diffusion of polysulfide intermediates induce undesirable shuttle effect and passivate separator/electrode interfaces. Herein we reported a facile, scalable, and green process to fabricate porous graphene (PG) modified separators for commercially viable lithium–sulfur batteries. PG, in combination with an amphiphilic polymer binder, rendered the engineered functional layer with extraordinary electrical conductivity, high surface area, large pore volume, and appropriate strength of chemisorption to polysulfides. Therefore, lithium–sulfur cells with sulfur loading of 1.8–2.0 mg cm−2 and PG separators exhibited a very high sulfur utilization of 86.5% (vs. 55.6% on cell with routine separators) at 0.05 C, a very low self-discharge rate of 90% retention (vs. 65% retention on routine separators), and enhanced rate capability. In addition, the fabrication of both PG and PG-modified separators was readily scaled-up for assembling and evaluating lithium–sulfur pouch cells with a large areal sulfur loading of 7.8 mg cm−2 and the initial discharge capacity was 1135 mA h g−1 at current density of 0.1 C. This was ascribed to the statically and dynamically suppressed shuttle effects through both the physical trapping of polysulfides into porous graphene and chemical binding of intermediates on poly(vinyl pyrrolidone) binder in a working cell.