A Permselective Coating Protects Lithium Anode toward a Practical Lithium–Sulfur Battery

Lithium metal is a desirable anode for high-energy density lithium-sulfur (Li-S) batteries. However, its reliability is severely limited by dendrite growth and side reactions with polysulfides, which are yet challenging to solve simultaneously. Herein, we report a protective layer that works the same way as the ion-permselective cell membrane, yielding a corrosion-resistant and dendrite-free Li metal anode specially for Li-S batteries. A self-limited assembly of octadecylamine together with Al3+ ions on a Li metal anode surface produces a dense, stable yet thin layer with ionic conductive Al-Li alloy uniformly embedded in it, which prevents the passage of polysulfides but regulates the penetrated Li ion flux for uniform Li deposition. As a result, the assembled batteries show excellent cycling stability even with a high sulfur-loaded cathode, suggesting a straightforward but promising strategy to stabilize highly active anodes for practical applications.