A Highly Reversible Zinc Anode for Rechargeable Aqueous Batteries

Zinc metal holds a great potential as an anode material for next-generation aqueous batteries due to its suitable redox potential, high specific capacity, and low cost. However, the uncontrollable dendrite growth and detrimental side reactions with electrolytes hinder the practical application of this type of electrodes. To tackle the issues, an ultrathin (∼1 μm) sulfonated poly(ether ether ketone) (SPEEK) solid-electrolyte interphase (SEI) is constructed onto the Zn anode surface by a facile spin-coating method. We demonstrate that the polymeric SEI simultaneously blocks the water molecules and anions, uniformizes the ion flux, and facilitates the desolvation process of Zn²⁺ ions, thus effectively suppressing the side reactions and Zn dendrite formation. As a result, the newly developed Zn@SPEEK anode enables a symmetric cell to stably operate over 1000 cycles at 5 mA cm^-2 without degradation. Moreover, with the Zn anode paired with a MnO₂ cathode, the full cell exhibits an improved Coulombic efficiency (over 99% at 0.1 A g^-1), a superior rate capability (127 mA h g^-1 at 2 A g^-1), and excellent cycling stability (capacity retention of 70% over 1000 cycles at 1 A g^-1). This work provides a facile yet effective strategy to address the critical challenges in Zn anodes, paving the way for the development of high-performance rechargeable aqueous batteries.