Multifunctional Zwitterionic Additive Enables Stable Zn Anodes through Interfacial Regulation and Crystallographic Orientation

The practical deployment of aqueous zinc–metal batteries (AZMBs) is hindered by Zn anodes, such as uncontrolled dendrite growth and water-induced side reactions. While monofunctional additives have achieved some successes, they ultimately fail to provide the long-term stability of Zn anodes. Herein, we introduce a zwitterionic 3-morpholinopropanesulfonic acid (3-Mor) molecule as a multifunctional electrolyte additive. First, instead of entering the Zn2+ solvation shell directly, 3-Mor operates by reconstructing the hydrogen-bond network within the bulk H2O, reducing the activity of H2O. Second, the sulfonate group and morpholine ring of 3-Mor enable specific adsorption onto the Zn surface, forming a water-deficient electric double layer (EDL) that guides Zn2+ deposition onto the (002) plane to suppress dendrite growth. Third, the intrinsic zwitterionic character of 3-Mor enables dynamic buffering of interfacial pH fluctuations, maintaining a stable interfacial microenvironment. As a result, Zn//Zn symmetric cells achieve an extended cycling lifetime of 3000 h at 1 mA cm–2, and the Zn//Ca0.24V2O5·0.83H2O full cell retains a capacity of 63.0 mAh g–1 after 7000 cycles. This work demonstrates a holistic interfacial molecular engineering strategy for achieving highly reversible Zn anodes through multifunctional modulation.