Trace Amounts of Multifunctional Electrolyte Additives Enhance Cyclic Stability of High‐Rate Aqueous Zinc‐Ion Batteries

Abstract Aqueous zinc ion batteries (AZIBs) are renowned for their exceptional safety and eco‐friendliness. However, they face cycling stability and reversibility challenges, particularly under high‐rate conditions due to corrosion and harmful side reactions. This work introduces fumaric acid (FA) as a trace amount, suitable high‐rate, multifunctional, low‐cost, and environmentally friendly electrolyte additive to address these issues. FA additives serve as prioritized anchors to form water‐poor Inner Helmholtz Plane on Zn anodes and adsorb chemically on Zn anode surfaces to establish a unique in situ solid‐electrolyte interface. The combined mechanisms effectively inhibit dendrite growth and suppress interfacial side reactions, resulting in excellent stability of Zn anodes. Consequently, with just tiny quantities of FA, Zn anodes achieve a high Coulombic efficiency (CE) of 99.55 % and exhibit a remarkable lifespan over 2580 hours at 5 mA cm −2 , 1 mAh cm −2 in Zn//Zn cells. Even under high‐rate conditions (10 mA cm −2 , 1 mAh cm −2 ), it can still run almost for 2020 hours. Additionally, the Zn//V 2 O 5 full cell with FA retains a high specific capacity of 106.95 mAh g −1 after 2000 cycles at 5 A g −1 . This work provides a novel additive for the design of electrolytes for high‐rate AZIBs.