Artificial Protective Interfacial Layer Functionalized by In Situ Constructed Hydrophobic Polyphosphonitrile-Containing Polymer for Dendrite-Free Zinc Metal Anodes

Aqueous zinc-ion batteries (AZIBs) demonstrate considerable promise for large-scale energy storage applications. However, their practical implementation faces substantial challenges stemming from persistent dendrite formation and detrimental interfacial side reactions, both originating from the thermodynamically unstable nature of the Zn-electrolyte interphase. Herein, we engineer a robust solid electrolyte interphase via rational molecular design by in situ grafting of poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) on Zn surfaces through polycondensation reactions. The multifunctional architecture of PZS, consisting of a phosphazene-rich inorganic domain and sulfonyl-containing organic moiety, not only holds appropriate mechanical strength but also reinforces interfacial adhesion through coordination of sulfonyl groups with Zn²⁺, facilitating to establish a robust protective layer. Concurrently, the intrinsic hydrophobicity of PZS creates an electrolyte-blocking barrier, effectively suppressing parasitic reactions related to water and favoring fast desolvation. Meanwhile, abundant zincophilic sites (sulfonyl and phenolic hydroxyl groups) are conducive to forming three-dimensional Zn²⁺ transport patterns and homogenizing interfacial electric/concentration fields, ultimately achieving uniform Zn deposition. Consequently, the as-constructed PZS-based multidefense interphase demonstrates exceptional cycling stability, sustaining over 2800 h in symmetrical cells at 2 mA cm^-2 (1 mA h cm^-2) while maintaining a high average Coulombic efficiency of 99.66% through 430 cycles in asymmetrical cells. The assembled Zn//MnO₂ full cell achieves high capacity retention of 92.9% after 1200 cycles at 1 A g^-1, demonstrating enhanced cycle durability. This interfacial engineering strategy provides an alternative paradigm for constructing robust electrode-electrolyte interphases to address the challenges of dendrite growth and side reactions in AZIBs.