Heteroatom Doping Strategy for Enhanced Sodium-Ion Storage in Na₂Fe_1.5Mn_1.5(PO₄)₃

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) are a cost-effective alternative to lithium-ion batteries for grid-scale energy storage.
• Developing advanced anode materials is critical for enhancing SIB performance and sustainability.
• Alluaudite Na2Fe1.5Mn1.5(PO4)3 (NFMP) is a potential SIB anode material, but its electrochemical properties require optimization.

Purpose of the Study:

• To synthesize and characterize a novel nitrogen and sulfur co-doped carbon layer wrapped alluaudite Na2Fe1.5Mn1.5(PO4)3 (NFMP@SNC) with a 3D urchin-like morphology.
• To investigate the electrochemical properties of NFMP@SNC as an anode material for SIBs.
• To provide fundamental insights into the electrochemical behavior of NFMP using density functional theory (DFT) calculations.

Main Methods:

• Hydrothermal synthesis technique for NFMP@SNC.
• Electrochemical performance testing (capacity, rate capability, cycling stability) for SIB anodes.
• Density functional theory (DFT) calculations to analyze electronic structure and Na+ diffusion barriers.

Main Results:

• NFMP@SNC exhibits a high reversible capacity of 253.40 mAh g-1 at 0.05C, retaining 61.2% of its theoretical capacity.
• The material demonstrates excellent rate capability, maintaining 71.76% at 0.1C (25 cycles) and 48.49% at 0.2C (100 cycles).
• DFT calculations reveal insights into the electronic band structure and Na+ diffusion pathways, supporting the experimental observations.

Conclusions:

• The N, S-doped carbon layer enhances electron transport, Na+ diffusion, and structural stability, preventing aggregation and side reactions.
• NFMP@SNC, with its 3D architecture and N,S co-doping, is a promising intercalation-type anode material for high-performance SIBs.
• This study highlights the potential of co-doped carbon coatings on alluaudite materials for advanced sodium-ion battery applications.