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

Area of Science:

• Materials Science
• Solid-State Chemistry
• Electrochemistry

Background:

• Lithium-ion batteries require advanced solid electrolytes for improved safety and performance.
• Lithium lanthanum zirconium oxide (LLZO) is a promising candidate due to its high ionic conductivity and stability.

Purpose of the Study:

• To synthesize Li7La3Zr2O12 (LLZO) material via solid-state reaction.
• To comprehensively investigate the thermodynamic characteristics of LLZO.
• To evaluate the potential of LLZO for use in lithium-ion batteries.

Main Methods:

• Solid-state reaction using Li2CO3, La2O3, and ZrO2 precursors.
• Phase analysis using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS).
• Thermodynamic property determination via calorimetry measurements, including heat capacity, enthalpy of formation, entropy, and Gibbs free energy.

Main Results:

• Successfully synthesized LLZO material.
• Determined molar heat capacity (C = 518.135 + 0.599 × T - 8.339 × T^-2 J·mol^-1·K^-1) over 298-800 K.
• Calculated standard enthalpy of formation (ΔHf = -186.4 kJ·mol^-1), enthalpy from elements (ΔHf = -9327.65 ± 7.9 kJ·mol^-1), entropy (S°298 = 362.3 J·mol^-1·K^-1), Gibbs free energy of formation (ΔGf°298 = -9435.6 kJ·mol^-1), and Gibbs free energy of reaction with Li (ΔG = 8.2 kJ·mol^-1).

Conclusions:

• The thermodynamic data supports the feasibility of using Li7La3Zr2O12 as a solid electrolyte in lithium-ion batteries.
• The determined thermodynamic properties provide crucial information for further development and optimization of LLZO-based batteries.