ANN ARBOR, MI
Polyhedral boron cluster salts, known for their high ionic conductivity and electrochemical stability, are emerging as promising candidates for solid-state battery electrolytes. However, their mechanical properties—key to maintaining contact and structural integrity during battery operation—have remained largely unexplored. This study addresses that gap by directly measuring the elastic modulus and hardness of four carbaborate-based electrolytes: LiCB₁₁H₁₂, LiCB₉H₁₀, NaCB₁₁H₁₂, and NaCB₉H₁₀.
Using nanoindentation under inert conditions, Dr. Oscar Tutusaus and Dr. Rana Mohtadi, and collaborators from the University of Kentucky and from Lawrence Livermore National Laboratory, report elastic moduli ranging from 8.8 to 12.3 GPa and hardness values from 0.15 to 0.38 GPa. These values are considerably lower than those of oxide- and sulfide-based solid electrolytes, indicating a softer, more deformable material that may better support stable interfacial contact during battery cycling. Supporting calculations from density functional theory (DFT) confirm the experimental trends and provide additional insight into bonding strength and predicted ductility based on cohesive energy and coordination structure.
Notably, three of the four compounds are predicted to be ductile—an uncommon trait among solid electrolytes—based on both experimental plasticity data and DFT analysis. With their low stiffness, high plasticity, and ability to form dense pellets at room temperature, these materials offer a unique mechanical profile. This work fills a key data gap and shows that boron cluster salts combine mechanical compliance with favorable processing characteristics, emphasizing their distinct mechanical behavior compared to more commonly studied solid electrolytes.
For detailed information, please refer to the published paper in Journal of Power Sources.
