Anodized Aluminum Oxide Separators with Aligned Channels for High-Performance Li-S Batteries

Lithium-sulfur (Li-S) batteries are promising to enable high-energy-density storage systems; however, their commercialization is hampered by several technical challenges such as polysulfide shuttle and safety issues related to the lithium metal anode. Herein, we use anodized aluminum oxide (AAO) membranes as separators in Li-S batteries for the first time. AAO membranes are rigid and nonflammable, which is helpful for improving battery safety. The aligned and uniform channels within AAO membranes provide fast pathways for lithium ion transport, leading to low areal specific resistance due to the electroosmotic flow of lithium ions in nanoscaled channels. In addition, the AAO separator leads to low overpotential during lithium deposition/stripping in lithium symmetric cells. The Li-S cells with AAO separators show better cycling performance than those with Celgard ones, in particular, at high C rates. At the 2 C rate, the cell shows a battery performance of 480 cycles with a capacity degradation rate of 0.105%, which is much better than that when the Celgard separator is used. This work demonstrates that AAO membranes are promising separators with unique properties for improving the performance of Li-S batteries.