Investigation of Electrochemical and Mechanical Properties of Li garnets for Solid-State Batteries
Research Poster Engineering 2025 Graduate ExhibitionPresentation by Nava Giri
Exhibition Number 193
Abstract
Solid-state electrolytes are pivotal in overcoming the safety and energy density limitations of traditional Li-ion batteries. This study investigates the electrochemical and mechanical properties of garnet-type electrolytes; Li.LaZrTaO (LLZT), Li.LaZr.Ta.O (LLZT.25), and high-entropy Li.LaZr.Nb.Ta.Hf.O (LLZNTH)) to assess their viability in suppressing Li dendrite growth, a critical barrier to their development. Dendrite formation arises from electrochemical factors (e.g., uneven Li deposition during cycling) and mechanical weaknesses (e.g., electrolyte fracture under stress). Thus, we evaluate how enhanced mechanical robustness and electrochemical stability synergistically improve critical current density (CCD), the threshold current beyond which dendrites cause short circuits. Samples were synthesized via solid-state reaction. Electrochemical impedance spectroscopy (EIS) measured ionic conductivity, while Li symmetric cells tested CCD. Mechanical properties; hardness, fracture toughness, and flexural strength (with Weibull modulus) were assessed via Vickers hardness and three-point bending. Microstructure was analyzed using SEM. LLZT exhibited the highest fracture toughness compared to LLZNTH and LLZT.25. However, LLZNTH achieved the highest CCD despite its lower fracture toughness. LLZT and LLZT.25 also displayed higher ionic conductivity than LLZNTH. These results suggest that while mechanical resilience (e.g., fracture toughness) is critical for resisting dendrite penetration, LLZNTH’s high-entropy composition (Nb, Ta, Hf substitution) may enhance interfacial stability or homogenize Li deposition, improving CCD despite its marginally lower mechanical performance. This study highlights the need to balance electrochemical and mechanical properties in solid electrolytes.
Importance
Solid-state batteries could revolutionize energy storage by replacing flammable liquid electrolytes, but lithium dendrite growth remains a major safety and reliability challenge. This work addresses a critical gap by revealing how both mechanical strength and electrochemical/structural design in garnet electrolytes influence dendrite suppression. While LLZT’s high fracture toughness enhances mechanical resistance to dendrites, the high-entropy LLZNTH achieves superior dendrite-blocking performance despite moderate toughness; likely due to its multi-cation structure homogenizing lithium deposition. This paradox highlights that dendrite resistance requires balancing bulk mechanical properties with atomic-scale interfacial stability. By clarifying this interplay, our findings guide the design of next-generation electrolytes that combine durability with electrochemical precision. Such advancements accelerate safer, high-energy batteries for commercial use, directly addressing global needs for sustainable energy technologies.