Reducing Li2CO3 formation and enhancing ionic conductivity in garnet electrolytes via molten salt synthesis for lithium metal batteries

초록

Molten Salt Synthesis (MSS) emerges as an advanced and highly effective method for the fabrication of high-performance solid electrolytes, overcoming key challenges associated with conventional solid-state synthesis (SS). MSS utilizes a molten salt medium, such as LiCl-KCl eutectic, to significantly enhance lithium-ion diffusion, reduce lithium loss, and suppress the formation of detrimental surface impurities like Li2CO3. The process facilitates efficient lithium replenishment, stabilizing the cubic phase of LLZTAO and ensuring superior structural integrity. Thermodynamic and kinetic analyses reveal that MSS-LLZTAO exhibits a higher activation energy (E-a) for Li2CO3 decomposition (17.92 kJ<middle dot>mol(-1)) compared to SS-LLZTAO (10.25 kJ<middle dot>mol(-1)), reflecting enhanced thermal stability and resistance to structural degradation. The superior ionic conductivity of MSS-LLZTAO (8.83 x 10(-4) S<middle dot>cm(-1), similar to 20% higher than SS-LLZTAO) is attributed to reduced grain boundary resistance and optimized lithium-ion transport pathways, enabled by uniform particle morphology and connectivity. The molten salt medium promotes Ostwald ripening, facilitating homogeneous particle growth and dense microstructures while minimizing defects. Additionally, the improved thermodynamic parameters, including higher enthalpy (Delta H) and Gibbs free energy (Delta G), further underscore the stability and efficiency of MSS-LLZTAO. This study establishes MSS as a transformative approach in solid electrolyte synthesis, capable of addressing the limitations of SS by enabling faster reaction kinetics, enhanced structural stability, and superior electrochemical properties. MSS-LLZTAO demonstrates remarkable promise as a solid electrolyte for next-generation all-solid-state batteries (ASSBs), offering enhanced ionic conductivity, thermal stability, and impurity-free grain boundaries critical for high-performance energy storage applications.

키워드