Tuning Solvation Structure and Interfacial Chemistry through High Polarity Additive toward Highly Stable Zn Anode ^†

Comprehensive Summary Aqueous Zn ion capacitors (AZICs) have the features of low‐cost, safety, sustainability and high energy density compared to other mainstream energy storage devices. However, the inevitable dendrite growth and side reactions severely limit the cycle life. Herein, the highly polar organic molecule triethylamine (TEA) is employed as a multifunctional electrolyte additive to enhance the stability of the Zn anode. The highly electronegative tertiary amine nitrogen within the TEA molecule preferentially coordinates with Zn ions (Zn 2+ ), reorganizing the solvated sheath structure and reconfiguring the hydrogen bonding network. In addition, theoretical calculations and experimental results show that TEA can effectively mitigate the parasitic reaction triggered by water activity by spontaneously adsorbing on the Zn surface to form a self‐assembled interfacial shielding layer, which inhibits the construction of micro electric field and the evolution of Zn dendrites. The Zn//Zn cell based on ZnSO 4 +TEA electrolyte achieves 3,900 h of stable cycling at 2 mA·cm –2 , a more than 19‐fold improvement over the ZnSO 4 electrolyte (less than 200 h). Moreover, AZIC assembled with the ZnSO 4 +TEA electrolyte maintains 80% capacity retention and nearly 100% Coulombic efficiency after 30,000 cycles at a high current density of 4 A·g –1 .