Coupled Regulation of Solvation Structure and Interfacial Engineering by Acetaminophen for Ultralong-Life Aqueous Zn-Ion Hybrid Capacitors

Abstract Aqueous zinc-ion hybrid capacitors (AZICs) offer the advantages of safety, low cost, and environmental friendliness, but the poor interfacial stability of the Zn anode remains a bottleneck for their large-scale energy storage applications. Certain electrolyte additives can only provide one-dimensional regulation, which is insufficient to synergistically suppress multiple failure mechanisms. This study reports a “multifunctional single-molecule” additive strategy utilizing acetaminophen (AP) to achieve ultralong-term stability of the zinc anodes. The synergistic interaction between the phenolic hydroxyl (−OH) and amide (−NHCOCH3) functional groups in AP creates a stable Zn2+ solvation environment, effectively suppressing the hydrogen evolution reaction. Concurrently, the electron-rich aromatic rings form a hydrophobic dynamic passivation interface protective layer, facilitating the reversible deposition and stripping of Zn. Consequently, the introduction of AP significantly enhances electrochemical performance, such as the Zn//Zn symmetric cell exhibits a lifespan extended to 1000 h at 1 mA cm−2 and 1 mAh cm−2, while the AZICs maintains a high specific capacity of 49.8 mAh g−1 and a Coulombic efficiency close to 100% after 60,000 cycles at a high current density of 7 A g−1. This study confirms the immense application potential of AP as an eco-friendly, multifunctional additive platform in high-performance aqueous zinc-based energy storage devices.