Achieving reversible Zn chemistry by constructing a built-in internal electric field to dynamically eliminate local charge accumulation

Abstract

The irreversible chemistry of the Zn anode, attributed to dendrite growth and parasitic side reactions, is a major constraint on the practical application of aqueous zinc-ion batteries. Herein, polyelectrolyte complexes (CPs) containing rich quaternary ammonium and carboxylate groups were developed as artificial protective layers to systematically and efficiently regulate Zn plating/stripping. By virtue of their unique amphoteric characteristic, a self-adaptive built-in electric field could be generated at the interface. Comprehensive experimental and computational analyses demonstrated that the as-generated built-in internal electric field caused prominent divergence of surface properties. The enriched Zn²⁺ flux and homogenized charge distribution could dynamically eliminate local charge accumulation at the interface and offer highly oriented, dendrite-free Zn deposition. Owing to the intrinsic self-healing feature of the CPs, the as-proposed electric field modulation strategy presents long-term effectiveness. Correspondingly, the cycling durability of the Zn anode was prolonged from 91 to 6330 h at 0.5 mA cm⁻² (∼70-fold enhancement). A promoted electrochemical performance of full cells was also demonstrated by coupling the CP-protected Zn anode with I₂ or NH₄V₄O₁₀ cathodes. In particular, a remarkable capacity maintenance was observed with Zn‖I₂ cells, with an ultraslow decay rate of 0.005‰ per cycle after 30000 cycles (over 290 days).