Abstract

Owing to high lithium-ion conductivity and good stability with lithium metal, Li7La3Zr2O12 (LLZO – a solid electrolyte) has emerged as a viable candidate for solid-state battery applications. In the current study, Al substituted LLZO (Al-LLZO) powder is synthesized using a typical solid-state reaction. The pellets are made with the synthesized powder and are subjected to annealing for different durations and its effect on the structural properties of the Al-LLZO is investigated in detail. Reitveld refinement of powder X-ray diffraction pattern reveals that the sintered Al-LLZO belong to cubic system with Ia -3d space group at room temperature. Morphology and microstructural properties of sintered powder is analyzed using FESEM and HRTEM/SAED, respectively. FESEM image of LLZO pellets shows well-structured cubic grains spread evenly over on the surface after sintering. The chemical compositions of the sample are identified using EDAX. The surface chemistry of the prepared samples is examined by X-ray photoelectron spectroscopy (XPS), which states that the observed photoelectron signals from O1s at about 531 eV and Li1s at 54.52 eV corresponds to Li-O bond in Al-LLZO. Raman spectra have been analyzed and the observed Raman peaks appeared at 299 cm-1, 393 cm-1, 492 cm-1, 514 cm-1 were assigned to Eg, F2g, A1g and F2g respectively. Phase transformation from C-LLZO to pyrochore LZO phase is noticed when the sample is sintered for 12 hr at 1100 °C. The impedance analysis is carried out to measure the conductivity of the Al-LLZO pellet and is found to be 0.3 X 10-5 S/cm, which is suitable for solid electrolyte applications in LIBs.

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