Superhalogen-Based Layered Hybrid Superlattices with High Ion Conductivity and Exceptional Mechanical Robustness

Layered hybrid superlattices are of current interest for functional materials [ Nature 635 (2024) 49]. To further expand their energy applications, we propose the first layered hybrid superlattice electrolyte, NaBH 4 -hBN, by uniquely integrating superhalogen [BH 4 ] − clusters into a hexagonal boron nitride (hBN) framework. This design leverages synergistic mechanisms: the weakened interlayer van der Waals interactions liberate Na + confinement, hBN-mediated lattice flexibility dynamically adjusts ion pathways, and the rotational motion from [BH 4 ] − rotation transiently lowers migration barriers. First-principles calculations, combined with machine learning-driven molecular dynamics, reveal a high room-temperature Na + conductivity of 16 mS/cm, surpassing that of state-of-the-art solid-state electrolytes (SSEs), such as NASICON and layered P2-type oxides. Moreover, this material exhibits an ultralow density of 1.60 g/cm 3, significantly lighter than conventional SSEs, while achieving exceptional mechanical robustness (bulk modulus = 115 GPa) and moderate electrochemical stability (1.89 V), with low interfacial reactivity (Δ E D,min,mutual = 73 meV/atom) toward layered oxide cathodes. By bridging cluster dynamics with structural coherence, this work establishes a promising strategy for engineering next-generation SSEs, offering merits for overcoming long-standing trade-offs in solid-state energy storage.