A Multifunctional Zwitterion Electrolyte Additive for Highly Reversible Zinc Metal Anode

Abstract Although zinc metal anode is promising for zinc‐ion batteries (ZIBs) owing to high energy density, its reversibility is significantly obstructed by uncontrolled dendrite growth and parasitic reactions. Optimizing electrolytes is a facile yet effective method to simultaneously address these issues. Herein, 2‐(N‐morpholino)ethanesulfonic acid (MES), a pH buffer as novel additive, is initially introduced into conventional ZnSO 4 electrolyte to ensure a dendrite‐free zinc anode surface, enabling a stable Zn/electrolyte interface, which is achieved by controlling the solvated sheath through H 2 O poor electric double layer (EDL) derived from zwitterionic groups. Moreover, this zwitterionic additive can balance localized H + concentration of the electrolyte system, thus preventing parasitic reactions in damaging electrodes. DFT calculation proves that the MES additive has a strong affinity with Zn 2+ and induces uniform deposition along (002) orientation. As a result, the Zn anode in MES‐based electrolyte exhibits exceptional plating/stripping lifespan with 1600 h at 0.5 mA cm −2 (0.5 mAh cm −2 ) and 430 h at 5.0 mA cm −2 (5.0 mAh cm −2 ) while it maintains high coulombic efficiency of 99.8%. This work proposes an effective and facile approach for designing dendrite‐free anode for future aqueous Zn‐based storage devices.