Effective resistance to dendrite growth of NASICON solid electrolyte with lower electronic conductivity

The interface resistance, relative density and electronic conductivity of ceramic electrolytes show great influences on the formation of dendrites, which is the dominant challenge of solid-state lithium/sodium batteries in the practical application. In this work, NASICON electrolytes (Na3Zr2Si2PO12) with enhanced ionic conductivity, improved relative density and lowered electronic conductivity were demonstrated through doping lanthanide ions (Pr3+, Eu3+ and Lu3+). The influences of lanthanide ions doping on the crystalline structure, density, ionic/electronic conductivity and the application performances especially for the resistance to dendrite growth were investigated in detail. The ionic conductivity and relative density were promoted whereas the electronic conductivity was reduced obviously for the Na3Zr2Si2PO12 electrolyte with the presence of lanthanide ions with low electronegativity, resulting in the promoted resistance to dendrite growth. Among the three types of rare earth ions, highest critical current density (CCD) of 0.9 mA/cm2 at RT was recorded for the Pr3+ doped Na3Zr2Si2PO12 electrolyte due to its compact microstructure and low electronic conductivity, owing to the substitution of Zr4+ ions by the Pr3+ ions with smallest electronegativity and largest ion radius. The presented results proved that the doping of appropriate rare earth ions can significantly decrease the electronic conductivity, resulting in the resistance to sodium dendrite for NASICON solid electrolyte.