Superionic Solid Electrolyte Li7 La3 Zr2 O12 Synthesis and Thermodynamics for Application in All-Solid-State Lithium-Ion Batteries

Abstract

Solid-state reaction was used for Li7 La3 Zr2 O12 material synthesis from Li2 CO3, La2 O3 and ZrO2 powders. Phase investigation of Li7 La3 Zr2 O12 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 (Cp,m), the standard enthalpy of formation from binary compounds (∆ox HLLZO) and from elements (∆f HLLZO), entropy (S0 298), the Gibbs free energy of the Li7 La3 Zr2 O12 formation (∆f G0 298) and the Gibbs free energy of the LLZO reaction with metallic Li (∆r GLLZO/Li) were determined. The corresponding values are Cp,m = 518.135 + 0.599 × T − 8.339 × T−2, (temperature range is 298–800 K), ∆ox HLLZO = −186.4 kJ·mol−1, ∆f HLLZO = −9327.65 ± 7.9 kJ·mol−1, S0 298 = 362.3 J·mol−1·K−1, ∆f G0 298 = −9435.6 kJ·mol−1, and ∆r GLLZO/Li = 8.2 kJ·mol−1, respectively. Thermodynamic performance shows the possibility of Li7 La3 Zr2 O12 usage in lithium-ion batteries.