Binder-Free Sodium Zinc Phosphate Protection Layer Enabled Dendrite-Free Zn Metal Anode

Aqueous Zn battery has been a promising alternative battery in large-scale energy storage systems due to its cost-effectiveness, sustainability, and intrinsic safety. However, its cycle life is impeded by the dendrite formation, severe corrosion, and side reactions on the zinc metal anode. Most ex situ coatings on the zinc surface extend the life span of zinc anodes but have drawbacks in Zn2+ ion conductivity. Herein, a robust sodium zinc phosphate layer was in situ built on zinc metal foil anode (Zn@NZP) via facile electrodeposition. The Zn2+ ion conducting protection layer alleviates corrosion, suppresses zinc dendrites, and lowers the energy barrier of Zn2+ plating and stripping. As a result, the Zn@NZP anode renders dendrite-free plating/stripping with a small overpotential of about 44 mV and a 12-fold enhancement long-life span compared to the bare zinc. Furthermore, a full cell using the Zn@NZP anode shows much improved capacity and cycling stability. This work provides a promising anode candidate for dendrite-free aqueous zinc ion batteries.