Na3Zr2Si2PO12 solid electrolyte with Bi2O3 as sintering aid for solid-state sodium batteries

Improving the density of Na 3 Zr 2 Si 2 PO 12 (NZSP) solid electrolyte is crucial for its application in solid-state sodium batteries. Here, bismuth oxide with low melting point has been evaluated as a sintering aid for NZSP solid electrolytes. Research has found that NZSP doped with 5 mass% Bi 2 O 3 increases grain boundary mobility by 3.1 times and has an ionic conductivity of 4.78 × 10 −3 S cm −1 , with a minimum activation energy of 0.30 eV, approximately 5 times that of undoped Bi 2 O 3 . This is because the electrolyte density increased from 77.3 to 93.7%. Compared with the region III process of NZSP without Bi 2 O 3 , Bi 2 O 3 promotes the densification process of Bi 2 O 3 dopant coarsening in region III. The constant current cycle of Na | NZSP-5 mass% Bi 2 O 3 | Na symmetric battery indicates that no short circuit will occur within 1200 h. The discharge capacity of solid-state batteries at 0.2 C is 98.5 mAh g −1 . This indicates that NZSP doped with 5% Bi 2 O 3 is a good electrolyte choice for sodium-ion batteries.