Engineered Grain Boundary Enables the Room Temperature Solid-State Sodium Metal Batteries

The NASICON-type (Sodium Super Ionic Conductor) Na3Zr2Si2PO12 solid electrolyte is one of the most promising electrolytes for solid-state sodium metal batteries. When preparing ceramic using a traditional high-temperature reaction, high-densification temperature would result in volatilization certain elements and consequent generation impurity phase, worsening functional mechanical performance NASICON electrolyte. We rationally introduced sintering additive B2O3 to matrix systemically investigated influence on crystal structure, microstructure, electrical performance, electrochemical electrolytes. results reveal that can effectively reduce densification promote Na3Zr2Si2PO12-2%B2O3-1150 ℃ achieves highest ionic conductivity 4.7 × 10−4 S cm−1 (at 25 °C) with an activation energy 0.33 eV. Furthermore, grain boundary phase formed during process could improve behavior inhibit propagation metallic dendrite within assembled Na/Na3Zr2Si2PO12-2%B2O3/Na3V1.5Cr0.5(PO4)3 cell reveals initial discharge capacity 98.5 mAh g−1 Coulombic efficiency 84.14% shows retention 70.3% at 30 mA over 200 cycles.