A self-preserving pitted texture enables reversible topographic evolution and cycling on Zn metal anodes

Abstract

We identify that the irreversible evolution of flat to non-uniform topography on a pristine Zn anode surface during repeated stripping/plating cycles triggers fatal dendrite growth. Given this, a self-preserving pitted surface prepared by a facile anisotropic etching method is introduced for Zn metal anodes. The self-preservation of the pitted texture is realized due to the high depth-to-width ratio of the micro-pits, which not only protects them from being electropolished during stripping but also avoids Zn deposits filling the pits as the electric field and drift flux are largely shielded deep in the pits. The numerous micro-pits can serve as nucleation sites and enable Zn (101) to dominate the rugged surface to strengthen Zn affinity and nucleation, resulting in favorable electrode kinetics and homogeneous deposition. More importantly, the self-preserving pitted structure allows the electrode surface to recover its pitted topography with uniform roughness after cycles, promising excellent cyclic reversibility for Zn anodes. Therefore, a prolonged lifespan in symmetric cells of >1000 h at 1.0 mA cm⁻²/1.0 mA h cm⁻² can be achieved and stable Zn‖MnO₂ cells with 87.5% capacity retention after 900 cycles and high coulombic efficiency of 99.88% are obtained.