Three Birds with One Stone: Tetramethylurea as Electrolyte Additive for Highly Reversible Zn‐Metal Anode

Abstract Aqueous Zn‐metal batteries are the most promising system for large‐scale energy storage due to their high capacity, high safety, and low cost. The Zn‐metal anode, however, suffers from continuous parasitic reactions, random dendrite growth, and sluggish kinetics in aqueous electrolytes. Herein, a high donor number solvent, tetramethylurea (TMU), is introduced as electrolyte additive to enable highly reversible Zn‐metal anode, where the TMU can 1) preferentially adsorb on the Zn surface to inhibit Zn corrosion and suppress parasitic reaction, 2) solvate with Zn 2+ and exclude the H 2 O from Zn 2+ solvation sheath to weaken water activity significantly, and 3) contribute to form an inorganic‐organic bilayer solid electrolyte interphase to enable homogeneous and rapid Zn 2+ transport kinetic for dendrite‐free Zn deposition. Benefiting from these three merits, the resulting aqueous electrolyte demonstrates a highly reversible Zn plating/stripping cycling in a Zn||Ti asymmetric cell for over 1200 cycles and in a Zn||Zn symmetric cell for over 4000 h. As a proof‐of‐concept, the aqueous Zn‐metal full cells assembled with various state‐of‐the‐art cathodes also deliver excellent cycling performance even with a 10 µm thin Zn anode, favoring the practical application.