Lattice-Interface Dual Engineering Unlocking Quasi-Zero-Strain and High-Rate Zinc-Ion Storage in Polyanionic Cathode

The advancement of aqueous zinc-ion batteries is hindered by the performance of cathode. Na₃V₂O₂(PO₄)₂F has attracted increasing attention for its advantages, including a high voltage plateau, large ion diffusion channels, and outstanding structural stability. However, its inadequate electronic conductivity causes undesired cycling performance and rate capability. In this work, a microwave hydrothermal-assisted high-temperature calcination has been utilized to obtain Li-doped Na₃V₂O₂(PO₄)₂F coated with N-doped carbon (N_2.85L_0.15VOPF@NC). Theoretical calculations and experimental data demonstrate that the co-modification of Li doping and carbon coating results in favorable morphological integrity, increased electronic conductivity, reduced Zn²⁺ migration barrier, and high average Zn²⁺ diffusion coefficient, contributing to superior electrochemical properties. N_2.85L_0.15VOPF@NC exhibits a significantly enhanced performance with reversible capacities of 151.9 and 47.2 mAh g^-1 at 0.5 and 5 A g^-1 over 80 and 4,000 cycles, respectively. The soft package batteries also exhibit a stable reversible capacity of 56.4 mAh g^-1 after 700 cycles. In situ electrochemical impedance spectroscopy uncovers the lattice strain release as an intrinsic factor in capacity enhancement, facilitating the ionic and electrical diffusion processes. In situ X-ray diffraction, ex situ X-ray photoelectron spectroscopy, and transmission electron microscopy account for the quasi-zero-strain behavior (volume change rate of 1.04%) and the reversible Zn²⁺ insertion/extraction mechanism.