Alumina Nanofilms As Active Barriers for Polysulfides in High-Performance All-Solid-State Lithium–Sulfur Batteries

Often considered one of the most promising approaches for the next generation beyond Li-ion technologies, all-solid-state lithium–sulfur batteries are, however, still far from competitive practical performance. Among the multiple intrinsic issues that this technology currently faces, the suppression of the polysulfides shuttle effect, where sulfur-based compounds migrate from the positive electrode to the surface of the negative electrode and undergo chemical reduction, is without a doubt one of the most challenging ones. A way of tackling this effect is proposed in this work by using alumina nanocoatings in the electrode–electrolyte interface, with a thickness in the 10 nm range and grown by means of magnetron sputtering, which may act as impermeable layers to polysulfides between the electrodes and the solid polymer electrolyte membrane. The best configuration for the nanocoating has been systematically studied in terms of position of the coating within the different electrode–electrolyte interfaces in the cell and, as shown in this work, growing a thin alumina coating over the positive electrode on the cathode–electrolyte interface effectively increases the performance of all-solid-state lithium–sulfur batteries, especially in terms of cycle life.