Exploring Multi-Transition-Metal NASICON Frameworks as High-Performance Cathodes for Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Sodium-ion batteries (SIBs) require sustainable, high-performance cathode materials.
• NASICON-type phosphates are promising candidates due to their earth-abundant transition metals (TMs).

Purpose of the Study:

• To investigate NASICON compositions with Mn, Cr, and/or Fe for SIB cathodes.
• To understand the impact of multiple TMs on cathode properties.
• To identify optimal compositions for enhanced battery performance.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• Nine NASICON compositions (unary, binary, ternary) with Mn, Cr, and/or Fe were studied.
• Phase behavior, intercalation voltages, electronic structure, and Na+ mobility were analyzed.

Main Results:

• Unary NASICONs show stabilization at intermediate Na content; binary/ternary systems exhibit complex phase behavior.
• Fe4+/Fe3+ redox activity significantly increases voltage (~4.0 V); Mn and Cr contribute to lower voltages.
• Mixed-TM frameworks enhance Na+ mobility with low migration barriers (0.3-0.4 eV).

Conclusions:

• NaxMnFe0.5Cr0.5(PO4)3 demonstrates a favorable balance of phase stability, voltage, and ion transport.
• DFT provides fundamental insights into TM interplay in NASICON cathodes.
• This work offers design principles for multi-TM NASICONs in SIBs.