Ultra-long cycling stability of aqueous zinc-ion batteries via self-assembled folic acid forming protective interface layer at zinc anodes

Aqueous zinc-ion batteries (AZIBs) are recognized as one of the most promising battery technologies, but dendrite growth and persistent parasitic reactions at the Zn anode hinder their practical use. This study employs cost-effective and source-abundant folic acid (FA) as a multifunctional electrolyte additive, which is self-assembled at the Zn anode, forming an effective layer improving the reversibility and stability of the zinc anode/electrolyte interface. In-situ Raman reveals the electrostatic shielding effect of the layer against SO 4 2− anions. In-situ scanning vibrating electrode technique (SVET) further verifies the superior inhibitory effect of the interface layer on Zn anode corrosion. Practically, Zn//Zn symmetric battery filled with ZnSO 4 /0.1 FA electrolyte achieves a prominent cycling stability of 9500 h at 0.2 mA cm −2 and 0.2 mAh cm −2 , and the constructed Zn//Cu half battery exhibits a high reversibility (99.69 %) after 1045 cycles. Strikingly, Zn//MnO 2 full battery also demonstrates outstanding charge/discharge durability for at least 900 cycles with a high reversibility of >99.94 % at 5 C. This study provides a novel paradigm for the development of environmentally benign and cost-efficient electrolyte, pivotal in realizing exceptionally reversible AZIBs.