Superionic Solid Electrolyte Li₇La₃Zr₂O₁₂ Synthesis and Thermodynamics for Application in All-Solid-State Lithium-Ion...

Solid-state reaction was used for Li₇La₃Zr₂O₁₂ material synthesis from Li₂CO₃, La₂O₃ and ZrO₂ powders. Phase investigation of Li₇La₃Zr₂O₁₂ was carried out by x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) methods. The thermodynamic characteristics were investigated by calorimetry measurements. The molar heat capacity (C), the standard enthalpy of formation from binary compounds (Δ) and from elements (Δ), entropy (S⁰₂₉₈), the Gibbs free energy of the Li₇La₃Zr₂O₁₂ formation (∆ G⁰₂₉₈) and the Gibbs free energy of the LLZO reaction with metallic Li (∆) were determined. The corresponding values are C = 518.135 + 0.599 × T - 8.339 × T^-2, (temperature range is 298-800 K), Δ = -186.4 kJ·mol^-1, Δ = -9327.65 ± 7.9 kJ·mol^-1, S⁰₂₉₈ = 362.3 J·mol^-1·K^-1, ∆ G⁰₂₉₈ = -9435.6 kJ·mol^-1, and ∆ = 8.2 kJ·mol^-1, respectively. Thermodynamic performance shows the possibility of Li₇La₃Zr₂O₁₂ usage in lithium-ion batteries.