The synergistic effect induced by "Z-bond" between cations and anions achieving a highly reversible zinc anode

Due to their high energy density, low cost, and environmental friendliness, aqueous zinc-ion batteries are considered a potential alternative to Li-ion batteries. However, dendrite growth and parasitic reactions of water molecules limit their practical applications. Herein, an ionic liquid additive, 1-butyl-3-methylimidazolium Bis(fluorosulfonyl)imide (BMImFSI), is introduced to regulate the electrical double layer (EDL). Both BMIm⁺ and FSI^- can preferentially adsorb on the Zn anode, constructing a water-poor EDL and thus effectively suppressing side reactions. Additionally, under the synergistic effect of the mineralized solid-electrolyte interphase (SEI) formed by the decomposition of FSI^- and the ion dispersion layer constructed by BMIm⁺ on the mineralized SEI, the deposition of zinc ions is effectively dispersed, preventing excessive aggregation of zinc ions and thus dendrite formation. The Zn‖Zn symmetric cells using the BMImFSI/ZnSO₄ electrolyte operate stably for 1060 h and 560 h at 10 mA cm^-2-10 mAh cm^-2 and 20 mA cm^-2-20 mAh cm^-2, respectively. The Zn‖Cu asymmetric cell maintains an average Coulombic efficiency of 99.4 % after 1000 cycles. The capacity retention of a full cell using α-MnO₂ as the cathode is significantly improved at 1 A g^-1.