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

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous zinc-ion batteries (AZIBs) are promising for large-scale energy storage.
• Cathode performance is a key limitation in AZIBs.
• Sodium vanadium oxyfluoride (Na3V2O2(PO4)2F) offers high voltage and structural stability but suffers from poor electronic conductivity.

Purpose of the Study:

• To enhance the electrochemical performance of Na3V2O2(PO4)2F for AZIB cathodes.
• To address the low electronic conductivity and rate capability issues.

Main Methods:

• Microwave hydrothermal-assisted high-temperature calcination was used.
• Synthesis of Li-doped Na3V2O2(PO4)2F coated with N-doped carbon (N2.85L0.15VOPF@NC).
• Characterization using theoretical calculations, electrochemical tests, in situ/ex situ spectroscopy, and microscopy.

Main Results:

• Co-modification with Li doping and N-doped carbon coating improved electronic conductivity and Zn2+ diffusion.
• N2.85L0.15VOPF@NC achieved high reversible capacities (151.9 mAh g-1 at 0.5 A g-1) and excellent long-term cycling stability (47.2 mAh g-1 at 5 A g-1 after 4,000 cycles).
• Soft package batteries demonstrated stable performance (56.4 mAh g-1 after 700 cycles).
• Quasi-zero-strain behavior (1.04% volume change) and reversible Zn2+ insertion/extraction mechanism were confirmed.

Conclusions:

• Li-doped and N-doped carbon-coated Na3V2O2(PO4)2F is a superior cathode material for AZIBs.
• The enhanced conductivity and reduced Zn2+ migration barrier are crucial for improved electrochemical properties.
• Lattice strain release contributes to capacity enhancement and facilitates ion diffusion.