Bond-Defect Synergy Enabled Ultrastable and High-Rate Sodium Iron Phosphate Cathode through Zn/F Co Substitution

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) face challenges in balancing cathode stability and rate capability.
• Na4Fe3(PO4)2P2O7 (NFPP) cathodes exhibit potential but struggle with this trade-off.

Purpose of the Study:

• To develop a novel strategy to overcome the stability-rate capability limitations in NFPP cathodes.
• To enhance the electrochemical performance of sodium-ion battery cathodes.

Main Methods:

• A synergistic bond-defect strategy utilizing Zn and F co-doping was employed.
• Material characterization and electrochemical testing were performed on the optimized NFPP cathode (NFZPPF).
• Full cell testing was conducted with a hard carbon anode.

Main Results:

• The synergistic bond-defect strategy successfully mitigated charge localization and narrowed the bandgap.
• Optimized NFZPPF cathodes demonstrated excellent cycling stability (76.25% retention after 16,000 cycles at 20 C) and rate performance (68.6 mAh g-1 at 50 C).
• The full cell achieved 88.8% capacity retention after 200 cycles at 2 C.

Conclusions:

• The synergistic bond-defect strategy is effective in enhancing NFPP cathode performance for SIBs.
• The optimized NFZPPF cathode shows significant promise for practical and high-performance sodium-ion energy storage applications.