Exploring Water Restriction in the Inner Helmholtz Plane for Enhanced Zinc Anode Protection through Fast Scan Voltammetry with Ultramicroelectrodes

Controlling the electric double layer (EDL), especially at the inner Helmholtz plane (IHP) of the zinc anode, is an effective method to limit dendrite formation and unwanted side reactions in aqueous zinc ion batteries (AZIBs). In this study, we utilized 1,3-bis(1,3-dicarboxypropyl)-1H-imidazole-3-ium chloride (BDIM) as an additive rich in donor sites that selectively adsorbs onto the Zn anode. This results in a water-deficient IHP, which improves the electrochemical stability. BDIM successfully inhibits the hydrogen evolution reaction (HER) by elevating its overpotential, thereby minimizing parasitic reactions. Using a specialized ultramicroelectrode (UME) and fast scan cyclic voltammetry, we confirm the presence of the BDIM molecules in the EDL and assess their impact on interfacial properties. Consequently, a symmetric Zn//Zn cell demonstrates an exceptional lifespan of over 1400 h with a current density of 1 mA cm –2 and a capacity of 1 mAh cm –2 . The Zn//Cu half-cell also achieved a high Coulombic efficiency of 99.35% for over 700 cycles. Furthermore, a full cell with a V 2 O 5 cathode achieved a specific capacity of 217.5 mAh g –1, maintaining 70% of its capacity after 700 cycles. These findings offer valuable insights into the development of IHP-modulating additives for stabilizing Zn anodes, paving the way for high-performance and long-lasting AZIBs.