Metastable sodium closo-hydridoborates for all-solid-state batteries with thick cathodes

JAS Oh and ZH Yu and CJ Huang and P Ridley and A Liu and TR Zhang and BJ Hwang and KJ Griffith and SP Ong and YS Meng, JOULE, 9, 102130 (2025).

DOI: 10.1016/j.joule.2025.102130

All-solid-state batteries (ASSBs) featuring a thick cathode layer paired with a high-capacity alloy anode offer enhanced energy density and reliable performance, even at subzero temperatures, and can outperform their liquid-based counterparts. Enabling such technology requires a solid electrolyte with high ionic conductivity, mechanical formability, and excellent electrochemical stability. Here, we demonstrate that a kinetically stable orthorhombic Na3(B12H12)(BH4) phase exhibits a superionic conductivity of 4.6 mS cm-1 at 30 degrees C alongside excellent reduction stability. High-throughput molecular dynamic simulations reveal that the propensity for anion motion significantly enhances the population of highly mobile Na+ without affecting the activation energy. By leveraging its high conductivity across a wide temperature range, this material enables the development of all-solid- state sodium-ion batteries with ultra-thick cathodes, delivering reliable functionality at room temperature and in subzero environments. This study expands our understanding of hydridoborate-based solid electrolytes, highlighting their potential in next-generation energy storage systems.

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