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

Abstract

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.