Calcium Doped NASICON Electrolyte with Graphite Coating for Stable All-solid-state Sodium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state sodium metal batteries are promising for energy storage but face challenges with low ionic conductivity in solid electrolytes and poor interfacial contact with sodium anodes.
• These limitations hinder efficient ion transport and can lead to dendrite formation, compromising battery safety and performance.

Purpose of the Study:

• To enhance the ionic conductivity and interfacial properties of Na3Zr2Si2PO12 solid electrolytes for all-solid-state sodium metal batteries.
• To improve the solid-solid contact between the solid electrolyte and the metallic sodium anode to enable uniform plating/stripping and suppress dendrite growth.

Main Methods:

• Doping Na3Zr2Si2PO12 solid electrolyte with Ca2+ to improve ionic conductivity.
• Coating a graphite-based interface layer on the Ca2+-doped electrolyte (Na3.4Zr1.8Ca0.2Si2PO12-G) to enhance interfacial contact with the sodium anode.
• Assembling a full battery using Na3V2(PO4)3 as the cathode and evaluating electrochemical performance.

Main Results:

• Ca2+-doped Na3Zr2Si2PO12 achieved a high ionic conductivity of 2.09×10-3 S cm-1 at room temperature.
• The graphite interface layer significantly improved critical current density to 3.5 mA cm-2, triple that of the undoped electrolyte.
• The assembled Na3V2(PO4)3/Na3.4Zr1.8Ca0.2Si2PO12-G/Na battery showed a reversible capacity of 81.47 mAh g-1 at 1C and 97.75% capacity retention after 500 cycles.

Conclusions:

• Ca2+ doping and graphite interface engineering are effective strategies to overcome limitations in all-solid-state sodium metal batteries.
• The developed solid electrolyte and interface enable stable and efficient sodium metal anode operation, paving the way for safer, high-performance sodium batteries.