Fast Ion Transport Interphase Constructed by Hollow Mesoporous Na₃V₂(PO₄)₃ for Stable Zinc Anode

Abstract The main challenges in aqueous Zn metal batteries (AZMBs) are enhancing energy density and cycling life, which require low Zn deposition/stripping overpotential and a stable anode/electrolyte interface. Herein, a hollow mesoporous Na₃V₂(PO₄)₃ coated with carbon (HMNVP/C) is designed as the Zn anode protective layer (HMNVP/C@Zn). The zincophilic Na₃V₂(PO₄)₃ with numerous ion channels accelerates Zn²⁺ desolvation, while the hollow mesoporous structure promotes rapid Zn²⁺ migration through the artificial solid electrolyte interface (ASEI). Diffusion rate differences between the external wall and hollow core lead to Zn²⁺ enrichment and flux homogenization at the anode interface. Consequently, the HMNVP/C@Zn symmetric cell achieves an ultralow overpotential of 13.0 mV at 1 mA cm⁻², with stable cycling for over 1200 h at 0.2 mA cm⁻² and 0.2 mAh cm⁻² without dendrite growth. Additionally, for the first time, the electrochemical process of the zinc anode is decomposed into seven steps, and determine the relaxation time range of Zn²⁺ migration in ASEI by in situ electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis. It is noted that the rapid Zn²⁺ migration within the stable HMNVP/C layer significantly reduces the impedance of subsequent zinc crystal growth. This novel design and characterization technique offer valuable insights for preparing advanced ASEI in AZMBs.