The π-electron delocalization strategy enables balanced interface for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are regarded as promising next-generation solution for large-scale energy storage due to their advantages such as high safety, low cost, and environmental friendliness. However, under high-rate and long-cycling conditions, Zn anodes suffer from challenges including hydrogen evolution, self-corrosion, and dendrite growth, which affects the performance and life of the batteries.

In a study published in Angewandte Chemie International Edition, Prof. CHEN Zhongwei's team from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences proposed a novel π-electron delocalization-based strategy for additive molecule screening, and established a clear structure–function relationship between additive molecular design and interfacial behavior, providing a new way to optimize AZIB performance.

By leveraging the self-assembly behavior of trace functional organic molecules at the electrode interface, the researchers constructed a flexible hydrophilic–hydrophobic interfacial layer (HHIL) on the Zn anode surface. This HHIL enhanced the interfacial stability and electrochemical reversibility.

Then, N-hydroxyphthalimide (NHPI) was identified as a functional additive, featuring a rigid quasi-planar structure, strong π-electron delocalization, and a high positive electrostatic potential. Through π–π stacking and ion–dipole interactions, NHPI spontaneously self-assembled on the Zn surface to form a robust HHIL. During cycling, this HHIL further promoted the formation of an inorganic sublayer rich in ZnF₂ and ZnS, resulting in a dual-layer structure that combines flexible organic and rigid inorganic interfaces.

This cooperative interface effectively regulated Zn²⁺ deposition, suppressed parasitic reactions and dendrite growth, and enhanced interfacial stability. As a result, Zn//Zn symmetric cells achieved stable cycling over 900 hours at a high current density of 20 mA cm^-2 with a capacity of 10 mAh cm^-2. Full Zn//NaV₃O₈·1.5H₂O cells delivered more than 25,000 cycles at 10 A g^-1 with 85% capacity retention, outperforming baseline systems. Also, high rate performance and practical applicability in soft-pack pouch cells were demonstrated.

"Our study establishes a full-link mechanism from molecular design to interfacial construction to performance enhancement. It provides both theoretical insights and experimental evidence for additive molecule design and interface regulation in AZIBs, promoting their development for long-life, high-energy-density energy storage applications," said Prof. CHEN.