Solid electrolytes with high lithium-ion conductivity and excellent stability are essential for advancing next-generation energy storage devices, such as solid-state lithium-ion batteries and sensor technologies. In this study, pure LLTO (Li0.5La0.5TiO3) and Sr and Zr-co-doped LLSZTO samples with the general formula (Li0.5La0.5)1−xSr0.5xZr0.05Ti0.95O3 were synthesized. The Zr doping concentration was fixed at 5%, while the Sr content was varied at 2%, 5%, 8%, and 12% in the samples designated as 2LLSZTO, 5LLSZTO, 8LLSZTO, and 12LLSZTO, respectively. The structural properties of all synthesized samples were characterized using X-ray diffraction (XRD) and further confirmed by Rietveld refinement, which revealed a tetragonal perovskite crystal structure belonging to the space group P4/mmm. In addition to the primary phase, phase analysis also identified the presence of secondary phases, specifically ZrO2 and Sr(ZrO3). Raman and FTIR analyses were carried out at room temperature for detecting active modes of vibrations for peak shift and stretching and vibrational modes of crystal structure, respectively. Field emission scanning electron microscopy (FESEM) revealed randomly distributed grains across all synthesized samples, with the average grain size increasing as Sr doping concentration increased. Notably, 8LLSZTO composition exhibited the largest grain size of approximately 1.320 µm, indicating enhanced grain growth. Complementary energy-dispersive spectroscopy (EDS) confirmed the presence of La, Sr, Zr, Ti, and O elements without any detectable impurities, ensuring compositional purity. UV–visible spectroscopy measurements indicated an optical band gap ranging from 1.83 to 1.94 eV, highlighting the material’s potential suitability for solid electrolyte applications in advanced energy storage systems. Impedance spectroscopy revealed that ionic conductivity increased with increasing Sr doping concentration. Among all compositions, the 5LLSZTO sample exhibited the highest electrical conductivity of 5.4 × 10-4 S/cm, while the 2LLSZTO sample showed the lowest conductivity at 2.3 × 10-4 S/cm. Furthermore, the 5LLSZTO composition demonstrated the highest dielectric constant and dielectric loss, measured at 85 and 0.90, respectively. These findings indicate that optimal Sr doping significantly enhances the electrical and dielectric properties of LLTO-based solid electrolytes, making them promising candidates for application in advanced energy storage devices. This study systematically investigates the influence of Sr and Zr co-doping on the electrical properties of LLTO-based perovskite solid electrolytes. The results provide valuable insights for optimizing the design of high-performance solid electrolytes for next-generation lithium-ion batteries and advanced sensor technologies.

Optimization of Sr and Zr Co-doping in lithium lanthanum titanate perovskite electrolytes for high-performance solid-state battery applications

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发表日期：

2025年9月5日

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Juel Rana,
Md. Rakibul Islam Bilash,
Md. Khairul Islam,
Md. Lutfor Rahman

摘要

Solid electrolytes with high lithium-ion conductivity and excellent stability are essential for advancing next-generation energy storage devices, such as solid-state lithium-ion batteries and sensor technologies. In this study, pure LLTO (Li_0.5La_0.5TiO₃) and Sr and Zr-co-doped LLSZTO samples with the general formula (Li_0.5La_0.5)_1−xSr_0.5xZr_0.05Ti_0.95O₃ were synthesized. The Zr doping concentration was fixed at 5%, while the Sr content was varied at 2%, 5%, 8%, and 12% in the samples designated as 2LLSZTO, 5LLSZTO, 8LLSZTO, and 12LLSZTO, respectively. The structural properties of all synthesized samples were characterized using X-ray diffraction (XRD) and further confirmed by Rietveld refinement, which revealed a tetragonal perovskite crystal structure belonging to the space group P4/mmm. In addition to the primary phase, phase analysis also identified the presence of secondary phases, specifically ZrO₂ and Sr(ZrO₃). Raman and FTIR analyses were carried out at room temperature for detecting active modes of vibrations for peak shift and stretching and vibrational modes of crystal structure, respectively. Field emission scanning electron microscopy (FESEM) revealed randomly distributed grains across all synthesized samples, with the average grain size increasing as Sr doping concentration increased. Notably, 8LLSZTO composition exhibited the largest grain size of approximately 1.320 µm, indicating enhanced grain growth. Complementary energy-dispersive spectroscopy (EDS) confirmed the presence of La, Sr, Zr, Ti, and O elements without any detectable impurities, ensuring compositional purity. UV–visible spectroscopy measurements indicated an optical band gap ranging from 1.83 to 1.94 eV, highlighting the material’s potential suitability for solid electrolyte applications in advanced energy storage systems. Impedance spectroscopy revealed that ionic conductivity increased with increasing Sr doping concentration. Among all compositions, the 5LLSZTO sample exhibited the highest electrical conductivity of 5.4 × 10^-4 S/cm, while the 2LLSZTO sample showed the lowest conductivity at 2.3 × 10^-4 S/cm. Furthermore, the 5LLSZTO composition demonstrated the highest dielectric constant and dielectric loss, measured at 85 and 0.90, respectively. These findings indicate that optimal Sr doping significantly enhances the electrical and dielectric properties of LLTO-based solid electrolytes, making them promising candidates for application in advanced energy storage devices. This study systematically investigates the influence of Sr and Zr co-doping on the electrical properties of LLTO-based perovskite solid electrolytes. The results provide valuable insights for optimizing the design of high-performance solid electrolytes for next-generation lithium-ion batteries and advanced sensor technologies.