Multi-cation doped NASICON solid electrolytes with ITO interface layer for high performance all-solid-state sodium batteries

Sodium-based all-solid-state batteries are considered as promising alternatives to lithium-ion batteries, benefiting from the improved safety and lower cost. However, low ionic conductivity of solid electrolytes as well as poor interfacial contacts among electrodes and solid electrolyte are still the main challenges limiting their practical applications. Herein, a Zn, Mg, and Sc co-doped NASICON-type solid electrolyte Na 3.45 Zr 1.85 (ZnMgSc) 0.05 Si 2.2 P 0.8 O 12 is designed and exhibits a significantly enhanced ionic conductivity of 4.24 mS cm −1 , which is one order of magnitude higher than that of the undoped Na 3 Zr 2 Si 2 PO 12 . Meanwhile, a thin indium tin oxide layer is applied onto the solid electrolyte surface using magnetron sputtering, thereby enhancing stability and wettability at the interface between solid electrolyte and sodium metal anode. This surface treatment strategy significantly raises the critical current density from 0.59 mA cm −2 to 9.95 mA cm −2 while effectively preventing the formation of sodium dendrite. As a result, Na|ITO@Na 3.45 Zr 1.85 (ZnMgSc) 0.05 Si 2.2 P 0.8 O 12 @ITO|Na symmetric battery maintains excellent cycling stability for 1700 h at 60 °C under 6 mA cm −2 , and exhibits stable performance over 2000 h at 2 mA cm −2 under room temperature. In addition, Na 3 V 2 (PO 4 ) 3 |Na 3.45 Zr 1.85 (ZnMgSc) 0.05 Si 2.2 P 0.8 O 12 @ITO|Na battery delivers an initial discharge capacity of 114.6 mAh g −1 with a Coulombic efficiency of 96.36 % at 0.1C and maintains 89.2 % capacity after 1000 cycles at 2C-rate.