Robust fluorine-rich YF3 artificial interfacial layer for providing uniform Zn2+ flux and enhancing cycling stability of Zn anodes.

Zn metal anodes have emerged as promising candidates for aqueous Zn-based energy storage devices owing to their high theoretical specific capacity, low redox potential, and abundance of raw materials. However, sluggish Zn2+ kinetics and uneven electric-field distribution at the interface between the Zn anode and electrolyte can lead to the formation of harmful Zn dendrites, reducing the cycle life of both the Zn anode and Zn-based devices. Here, a structurally stable rare-earth compound, yttrium fluoride (YF3), is introduced as an artificial interfacial layer for Zn anodes to facilitate Zn2+ migration and nucleation. This modification results in a uniform Zn2+ flux and deposition environment, effectively reducing the nucleation overpotential of Zn2+ and enhancing the cyclic lifespan of Zn anodes. By varying the fluorine source, two different morphologies, i.e., YF3 nanorods (CYF3) and fluorine-rich YF3 nanospheres (SYF3) are synthesized. The non-stoichiometric SYF3 nanospheres, characterized by abundant fluorine-containing zincophilic sites, demonstrate superior performance in optimizing the Zn2+ migration and deposition behaviors. The SYF3@Zn-based symmetric cell exhibits stable cycling for over 1000 h at 5 mA cm-2 while maintaining a low and stable polarization voltage. The SYF3@Zn//Cu half-cell demonstrates stable cycling performance over 6000 cycles, with a total operating time exceeding 2400 h at 5 mA cm-2. Furthermore, a Zn-ion capacitor based on SYF3@Zn and activated carbon exhibits a high-capacity retention of 74% after 40 000 cycles at 1 A g-1, demonstrating excellent cycling stability. The excellent electrochemical performance of SYF3@Zn is attributable to accelerated interfacial Zn2+ migration, uniform Zn2+ flux, and reversible Zn plating/stripping. These findings provide valuable insights for the development of advanced dendrite-free reversible Zn anodes and Zn-based energy storage devices.