Multifunctional Polypyrrole Interphase Actively Manages Anion Transport for Stable, High-Rate Zinc Anodes

Zinc-nickel batteries (ZNBs) are a promising energy storage technology owing to their high output voltage, inherent safety, and cost-effectiveness. However, their practical application is limited by zinc-anode instability in alkaline electrolyte, which leads to performance-degrading dendrite growth and passivation. To address this issue, we introduce an electropolymerized polypyrrole (PPy) film as a multifunctional artificial solid electrolyte interphase to stabilize the anode. The PPy layer facilitates the desolvation of OH^- ions during discharge, enhancing reaction kinetics, while simultaneously restricting the diffusion of Zn(OH)₄ ^2- ions into the bulk electrolyte, thereby mitigating dendrite growth and anode passivation. Consequently, a full battery incorporating the protected anode with a Ni(OH)₂ cathode (ZnO@PPy||Ni(OH)₂) exhibits exceptional performance. Operating with a low electrolyte-to-capacity (E/DC) ratio of 0.05 mL mAh^-1 and a high depth of discharge of 100%, the battery delivers 565 mAh g^-1 after 245 stable cycles at 1 C. Moreover, when charged at 1 C and discharged at 10 C, it maintains 620 mAh g^-1 over 340 cycles, with capacity retention of 94%. This work presents a simple and effective strategy for developing protective layers for Zn-based anodes, offering a new design paradigm for engineering active electrode-electrolyte interphases to enable high-performance ZNBs.