A Heteroanionic Zinc Ion Conductor for Dendrite-Free Zn Metal Anodes

Abstract

Although zinc-based batteries are promising candidates for eco-friendly and cost-effective energy storage devices, their performance is severely retarded by dendrite formation. As the simplest zinc compounds, zinc chalcogenides, and halides are individually applied as a Zn protection layer due to high zinc ion conductivity. However, the mixed-anion compounds are not studied, which constrains the Zn2+ diffusion in single-anion lattices to their own limits. A heteroanionic zinc ion conductor (ZnyO1−xFx) coating layer is designed by in situ growth method with tunable F content and thickness. Strengthened by F aliovalent doping, the Zn2+ conductivity is enhanced within the wurtzite motif for rapid lattice Zn migration. ZnyO1−xFx also affords zincophilic sites for oriented superficial Zn plating to suppress dendrite growth. Therefore, ZnyO1−xFx-coated anode exhibits a low overpotential of 20.4 mV for 1000 h cycle life at a plating capacity of 1.0 mA h cm−2 during symmetrical cell test. The MnO2//Zn full battery further proves high stability of 169.7 mA h g−1 for 1000 cycles. This work may enlighten the mixed-anion tuning for high-performance Zn-based energy storage devices.