Superionic Solid Electrolyte Li(7)La(3)Zr(2)O(12) Synthesis and Thermodynamics for Application in All-Solid-State Lithium-Ion Batteries

Solid-state reaction was used for Li(7)La(3)Zr(2)O(12) material synthesis from Li(2)CO(3), La(2)O(3) and ZrO(2) powders. Phase investigation of Li(7)La(3)Zr(2)O(12) 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(p,m)), the standard enthalpy of formation from binary compounds (Δ(ox)H(LLZO)) and from elements (Δ(f)H(LLZO)), entropy (S(0)(298)), the Gibbs free energy of the Li(7)La(3)Zr(2)O(12) formation (∆(f) G(0)(298)) and the Gibbs free energy of the LLZO reaction with metallic Li (∆(r)G(LLZO/Li)) were determined. The corresponding values are C(p,m) = 518.135 + 0.599 × T − 8.339 × T(−2), (temperature range is 298–800 K), Δ(ox)H(LLZO) = −186.4 kJ·mol(−1), Δ(f)H(LLZO) = −9327.65 ± 7.9 kJ·mol(−1), S(0)(298) = 362.3 J·mol(−1)·K(−1), ∆(f) G(0)(298) = −9435.6 kJ·mol(−1), and ∆(r)G(LLZO/Li) = 8.2 kJ·mol(−1), respectively. Thermodynamic performance shows the possibility of Li(7)La(3)Zr(2)O(12) usage in lithium-ion batteries.