Phosphonitrile-based porous polymer interfaces for coupled homogenization of Zn2+ flux and interfacial electric field distribution enabling the development of dendrite-free zinc anodes

Abstract

Anode–electrolyte interfacial instability caused by the uneven Zn²⁺ ion flux and local electric field concentration leads to rapid capacity fading and dendrite formation (in turn short circuiting), thereby making the high theoretical capacity and cost-effectiveness of aqueous zinc-ion batteries impractical. To address the issue, we engineered a phosphonitrile-based porous organic polymer (PPOP) with a cyclophosphazene backbone via a Schiff-base condensation reaction. The chemistry produced abundant zincophilic sites that facilitated continuous ion transport and ensured a uniform Zn²⁺ flux across the interface. More specifically, the extended π-conjugated framework of the PPOP skeleton enabled electron delocalization and suppression of the local electric field concentration that resulted in homogeneous Zn deposition. The PPOP@Zn anodes therefore exhibited long-term stability for over 2500 h at 2 mA cm⁻² and high reversibility where the average efficiency exceeded 99.6%. Remarkably, the PPOP@Zn‖NVO full-cell configuration displayed a superior specific capacity of 196.7 mAh g⁻¹ over 2000 cycles at a high current density of 5 A g⁻¹, far surpassing bare Zn‖NVO (87.1 mAh g⁻¹). This work offers an effective strategy for achieving dendrite-free interfacial layers that regulate Zn²⁺ ion flux and homogenize the interfacial electric field distribution.