Hydrophilicity Engineering of Cathodes for High-Performance Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) have emerged as a promising alternative or complement to lithium-ion batteries (LIBs) owing to their low cost, intrinsic safety, and high theoretical capacity. However, the instability and hydrophobic nature of common cathode materials, such as vanadium pentoxide (V2O5), remain major obstacles to their practical commercialization. In contrast to conventional strategies that rely on complex surface modifications of V2O5 powders, this work proposes a simple and cost-effective post-treatment approach. Specifically, an organic–inorganic hybrid film composed of polyethylene glycol (PEG) and graphene oxide (GO) is directly drop-cast onto the surface of the as-prepared cathode. The amphiphilic PEG component markedly enhances the surface wettability, even in the presence of the hydrophobic polyvinylidene fluoride binder (PVDF), thereby promoting efficient contact with aqueous electrolytes. Concurrently, the incorporation of the PEG-GO layer facilitates both ionic and electronic transport, contributing to an improved electrochemical performance. As a result, the full cell employing a commercial Zn foil anode and a PEG–GO-coated cathode delivers an outstanding discharge capacity of 159.3 mAh·g–1 over 2500 cycles at a high current density of 5 A·g–1, demonstrating remarkable long-term stability. Compared with the intricate surface engineering methods at the synthesis stage, this straightforward post-treatment strategy provides an attractive and practical route for developing high-performance AZIB cathodes.