来源：ACS Publications
Solid-state sodium batteries operating at ambient temperatures are promising alternatives to liquid electrolyte batteries, offering improved safety and higher energy density. Among solid-state electrolytes, the ceramic Na-conducting electrolyte Na5YSi4O12 (N5) stands out due to its high Na-ion conductivity, wide electrochemical stability window, and compatibility with high-energy-density cathodes. However, achieving high ionic conductivity at room temperature remains a challenge. In this study, the effect of La doping on the electrochemical properties of an N5 ceramic electrolyte is systematically investigated. By optimizing the molar ratio of La2O3, La is successfully doped at the Y-site, leading to lattice parameter expansion, as confirmed by Rietveld refinement of the XRD data. Scanning electron microscopy analysis reveals significant changes in grain boundary morphology in La-doped Na5YSi4O12, resulting in an increase in grain boundary ionic conductivity from 1.6 × 10–4 S cm–1 of the pristine one to 4.3 × 10–4 S cm–1. Additionally, La doping preserves the low activation energy (0.19 eV) and high electrochemical stability window (up to 8 V vs Na/Na+). La-doped N5 demonstrates superior cycling stability for Na deposition/stripping, maintaining performance for over 1000 h at 15 μA cm–2, compared to only 118 h for the pristine one. This study indicates that La-doped N5 is a promising solid electrolyte for all-solid-state Na batteries.
In this work, La2O3 was used for dual purposes as a sintering aid and dopant in the Y site in N5. Sinterability of the N5 pellet was improved by La2O3 addition, leading to higher ionic conductivity. Additionally, the La-doped N5 provided stable Na stripping/deposition behavior compared with pristine N5.