Phosphonitrile-based Porous Polymer Interfaces for Coupled Homogenization of Zn2+ Flux and Interfacial Electric Field Distribution Enabling Dendrite-free Zinc Anodes

Abstract

Aqueous zinc-ion batteries (AZIBs) are promising energy storage devices owing to their high theoretical capacity, low redox potential and cost-effectiveness. However, the interfacial instability between the zinc anode and the aqueous electrolyte caused by the uneven Zn2+ flux and the local electric field concentration, resulting in capacity decay and battery short circuit. Herein, a phosphonitrile-based porous organic polymers (PPOP) with a cyclophosphazene backbone is constructed via a Schiff-base condensation reaction to regulate the interfacial stability between the Zn anode and electrolyte. The abundant zincophilic sites provide continuous ion transport channels to ensure a homogeneous Zn2+ flux across the interface. Meanwhile, the extended π-conjugated framework of PPOP skeleton facilitates electron delocalization and suppresses local electric field concentration, thus realizing uniform Zn deposition. As a result, the PPOP@Zn anode delivers long cycling stability of 2500 h at 2 mA cm-2 and high reversibility with an average coulombic efficiency exceeding 99.6%. Furthermore, the PPOP@Zn||NVO full battery exhibits a high specific capacity of 196.7 mAh g-1 after 2000 cycles at 5 A g-1, far surpassing than bare Zn||NVO (87.1 mAh g-1). This work demonstrates a rational design of phosphonitrile-based porous polymers that regulate Zn2+ flux and homogenize the interfacial electric field distribution. It offers an effective strategy for constructing stable interfacial layers for dendrite-free Zn anodes.