Bilayer separator enabling dendrite-free zinc anode with ultralong lifespan >5000 h

Aqueous zinc (Zn) batteries with Zn metal anodes are promising clean energy storage devices with intrinsic safety and low cost. However, Zn dendrite growth severely restricts the use of Zn anodes. To effectively suppress Zn dendrite growth, we propose a bilayer separator consisting of commercial butter paper and glass fiber membrane. The dense cellulose-based butter paper (BP) with low zincophilicity and high mechanical properties prevents the pore-filling behavior of deposited Zn and related separator piercing, effectively suppressing the Zn dendrite growth. As a result, the bilayer separators endow the Zn||Zn symmetrical batteries with a superlong cycling life of Zn anodes (over 5000 h) at 0.5 mA cm−2 and the full batteries enhanced capacity retention, demonstrating the advancement of the bilayer separator to afford excellent cyclability of aqueous metal batteries.