Functional separators for the batteries of the future

Lithium/sulfur batteries are one of the most promising technologies for the next-generation batteries. However, this technology suffers from several problems mainly related to the instability of metallic lithium and to the polysulfides (PS) shuttle. An approach to address such issues is the design of new separators or the modification of existing commercial ones. The use of hybrid membranes is here proposed to improve the performance of Li metal anode and sulfur cathode. Composite separators are obtained by electrospinning or drop-casting a polymer solution of polyvinylidenefluoride (PVdF) containing graphene oxide (GO) on a polyolefin commercial Celgard 2300 separator. This is the first time that a thin layer of electrospun PVdF/GO composite is applied to a polyolefin separator for the use in Li metal-based batteries. We demonstrate that electrospinning is an effective method to obtain a thin polymer layer of PVdF/GO. The electrospun layer improves the wettability of the separator; it is beneficial to the growth of “soft” dendrite on Li anode and has a positive effect on the PS shuttle process. The casted layer featuring a higher GO content is also effective in increasing the separator wettability, although with a minor effect on Li interphase.