Suppression of polysulfide shuttling with a separator modified using spontaneously polarized bismuth ferrite for high performance lithium-sulfur batteries

To effectively prevent polysulfides from transporting from the cathode to the anode is one of the critical prerequisites for the successful commercialization of lithium-sulfur batteries. Unfortunately, conventional commercially available polypropylene separators find it hard to meet this requirement due to their incapability of blocking polysulfide shuttling. Therefore, the development of a facile and scalable production of a new modified separator that can effectively regulate the shuttling of polysulfides will be very beneficial for the practical application of lithium-sulfur batteries. In this work, bismuth ferrite powder with spontaneous polarization is adopted to modify the separator owing to its special interaction with polysulfides. We develop a facile hydrothermal method to synthesize cubic-like bismuth ferrite particles of high purity, and apply them on the surface of the commercial separator with graphene oxide and a conductive agent. Our results show that the so-modified separator can effectively suppress the shuttling of polysulfides and then greatly improve the electrochemical properties of the lithium-sulfur battery in terms of cycle stability, rate performance, reaction kinetics, self-discharge behaviour and anode corrosion. Remarkably, our cell exhibits a high capacity density of 5.1 mA h cm(-2)at an ultra-high sulfur loading of 5.6 mg cm(-2), which is higher than that of known commercial lithium ion batteries.