Entropy-Enhanced Multi-Doping Strategy to Promote the Electrochemical Performance of Na₄Fe₃(PO₄)₂P₂O₇

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) are promising for large-scale energy storage.
• Polyanion-type cathode Na4Fe3(PO4)2P2O7 (NFPP) shows potential but needs improved cycle stability and rate capability.

Purpose of the Study:

• To enhance the electrochemical performance of NFPP cathodes.
• To improve the cycle stability and rate capability of NFPP for SIB applications.

Main Methods:

• Synthesized an entropy-enhanced multi-doped NFPP cathode (HE-NFPP) using Na4Fe2.95(NiCoMnMgZn)0.01(PO4)2P2O7.
• Investigated sodium storage mechanism using in-situ X-ray Diffraction (XRD).
• Fabricated a pouch cell using HE-NFPP and hard carbon (HC).

Main Results:

• HE-NFPP cathode demonstrated improved rate performance (67.1 mAh g-1 at 50 C) and cycle performance (92.0% retention after 1000 cycles at 1 C).
• Enhanced configuration entropy improved thermodynamic structural stability.
• In-situ XRD revealed an imperfect solid solution reaction with low volume change (4.0%).
• Pouch cell achieved an average working voltage of 3.0 V and energy density of 165 Wh kg-1.

Conclusions:

• Entropy-enhanced multi-doping strategy significantly improves NFPP cathode performance for SIBs.
• HE-NFPP exhibits high-rate and long-cycle performance, highlighting its potential for practical SIB applications.
• The study provides a pathway for developing advanced cathode materials for efficient energy storage.