Regulating Surface Overpotential for Uniform Zinc Stripping/Plating Morphology Toward Ultra-Stable Aqueous Zinc-Ion...

Aqueous zinc-ion batteries (AZIBs) are promising for grid energy storage owing to their low cost and high safety. However, the reversibility of the zinc anode is compromised by the uneven stripping/plating morphology and detrimental side reactions. Therefore, regulating zinc stripping/plating behavior and suppressing side reactions are pivotal for the development of AZIBs. Thermodynamic and classical nucleation theory predict that increasing the surface overpotential (|η_s|) can reduce the critical nucleation atom number (N_crit) and critical nucleation energy barrier (ΔG_crit), thereby optimizing zinc stripping/deposition morphology. Herein, a trace amount of zwitterion, [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) (SBMA), is introduced into 1 m ZnSO₄ as a surface overpotential regulator. SBMA molecules uniformly adsorb onto the zinc anode surface, forming an adsorption layer. This layer not only increases |η_s|, but also markedly suppresses side reactions. Consequently, the stripping/deposition morphology of the zinc anode during the first cycle is significantly optimized, ensuring long-term cycling stability. Ultimately, the Zn||Zn symmetric cell with only 1 wt.% SBMA achieves a long lifespan for over 800 h even at a high depth of discharge of 88.0%. Furthermore, the Zn||PANI (polyaniline) full cell exhibits negligible capacity decay after 1200 cycles at 1 A g^-1. This work provides valuable insights into the design of ultra-stable AZIBs.