Playing with Water Molecules: “Repulsing” or “Trapping” to Exclude Water-Induced Side Reactions on Zn Metal Anode

Abstract

Aqueous Zn ion batteries (AZIBs) have attracted considerable research interest because they offer potential solutions for battery safety concerns, enable long-duration energy storage, maintain cost-effectiveness, and support diverse application scenarios. However, the electrochemical performance of AZIBs is hampered by inherent issues arising from water molecules present in water-based electrolytes. Water molecules are a double-edged sword in AZIBs, which could serve not only as the rapid transporter of Zn²⁺ ions but also as the instigator of anode corrosion, passivation, hydrogen precipitation, narrow electrochemical window, cathode dissolution, and exacerbation of zinc dendrite growth in aqueous environments. In light of these challenges, this review analyzes the fundamental principles underlying water molecules’ role in triggering water-related problems. It then innovatively summarizes methods to mitigate water activity and alleviate interface issues from the perspective of “water repulsing” and “water trapping” including approaches such as interface protection, electrolyte engineering, separator modification, and so on, hoping to stimulate the imagination of researchers playing with water molecules. It should be clarified that the “water repulsing” and “water trapping” modification strategies do not exist independently, but are complementary with intersections. Finally, optimization strategies for mitigating water-induced issues to realize high-efficiency and commercially viable AZIBs are proposed, aiming to offer fresh perspectives and insights to advance AZIB technology.