Adhesive Molecular Protective Layer of a Zincophilic Ionic Liquid for Durable High-Energy Zn-Ion Batteries

The lifespan of Zn-ion batteries (ZIBs) is severely hindered by dendritic Zn growth and side reactions. These drawbacks are exacerbated under practical conditions, such as high current density. Herein, an adhesive ionic liquid electrolyte additive with a zincophilic side chain is introduced to achieve a stable electrode/electrolyte interface and efficient mass transport via a modulated electrical double layer and zincophilic molecular channels. The additives anchor to the Zn anode, forming a robust molecular layer that modulates local electric field distribution and serves as a tip-shielding barrier. Ether-hydroxyl-functionalized side chains with lone pairs of electrons facilitate selective Zn²⁺ ion conduction, promoting Zn-rich layer formation. Stable battery operation is achieved under fast-charging conditions along with suppressed dendritic Zn growth and side reactions. Zn//Zn cell with the additives exhibits a long cycle life of 1100 h at 10 mA cm⁻² and 10 mAh cm⁻². The superior reversibility is further validated in a practical Zn–I₂ system, demonstrating stable capacity retention over 10 000 cycles and a high reversible capacity of 2.3 mAh cm⁻² at a current density of 20 mA cm⁻², outperforming state-of-the-art ZIBs. This study provides novel insights into the design of bifunctional additives and demonstrates a pathway for durable and high-energy ZIBs.