Efficient, Selective Sodium and Lithium Removal by Faradaic Deionization Using Symmetric Sodium Titanium Vanadium...

Area of Science:

• Materials Science
• Electrochemistry
• Separation Science

Background:

• NASICON materials are effective for sodium ion capture, applicable in batteries.
• Faradaic deionization (FDI) leverages ion intercalation for selective removal.

Purpose of the Study:

• Investigate the selective removal of sodium ions using a NASICON-based mixed Ti-V phase (NTVP).
• Evaluate NTVP's performance in separating sodium from other alkali and alkaline-earth metal cations via FDI.

Main Methods:

• Galvanostatic cycling experiments in three-electrode cells with various cations (Na+, K+, Mg2+, Ca2+, Li+).
• Electrochemical titration and modeling to understand intercalation mechanisms.
• Incorporation of NTVP electrodes into an FDI cell with automated fluid recirculation.

Main Results:

• NTVP exhibits intrinsic selectivity for Na+ over K+, Mg2+, and Ca2+ (selectivity factor of 56).
• Only Na+ and Li+ intercalate into NTVP; other cations show capacitive response.
• FDI cell achieved up to 94% sodium removal with high selectivity (3-6) over competing ions.
• Optimizing current density improved selectivity and reduced energy consumption by ~50%.

Conclusions:

• NTVP is a highly selective electrode material for sodium removal via FDI.
• The intercalation mechanism in NTVP mitigates gradient issues in flow systems.
• NTVP shows potential for selective lithium recovery and efficient ion separation processes.