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.