Effect of Li3AlF6 as sintering-aids on the structure and conductivity of Li0.25La0.25NbO3 ceramic solid electrolytes

Yuxin Wang, Weiwei Hu, Yazhou Kong, Jie Chang, Guang Hu, Kailong Zhang, Yifei Chen, Mengyao Lu

Abstract


With the growing demand for high-safety and high-energy-density energy storage systems, all-solid-state lithium batteries (ASSLBs) have attracted extensive attention due to their excellent safety and potential high performance. Among them, the solid electrolyte is a key component. This study systematically investigates the effects of Li3AlF6 as a sintering aid on the sintering behavior, crystal structure, microstructure, and electrochemical performance of LLNO (Li0.25La0.25NbO3) ceramics. LLNO ceramic samples with different Li3AlF6 doping levels (0-8 wt.%) were prepared via a solid-state reaction method and sintered at 1050 °C and 1100 °C. The samples were characterized by XRD, SEM, AC impedance spectroscopy, and DC polarization testing. The results indicate that Li3AlF6 significantly reduces the sintering temperature of LLNO and promotes the densification process. However, excessive doping (8 wt.%) leads to the formation of impurity phases such as AlF3, increases grain boundary resistance, and reduces ionic conductivity. The sample with 5 wt.% Li3AlF6 sintered at 1050 °C exhibits the best overall performance: an ionic conductivity of 2.08 × 10-6 S·cm-1 and an activation energy of 0.340 eV. Although its conductivity is slightly lower than that of pure LLNO (4.12 × 10-6 S·cm-1) sintered at 1100 °C, the introduction of Li3AlF6 provides a feasible route for low-temperature sintering, which is beneficial for future co-sintering integration with electrode materials.


Keywords


Li0.25La0.25NbO3, Li3AlF6, Sintering aids, Ceramic

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DOI: https://doi.org/10.33180/InfMIDEM2026.104

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