Year: 2026
Type: preprint
Abstract: Sodium closo-hydridoborates have emerged as promising solid-state electrolytes for Na-ion batteries because of their high ionic conductivity and electrochemical stability. However, their sensitivity to water makes them challenging to scale-up. In this work, we systematically investigate the impact of controlled hydration on the structure, ion transport, and interfacial stability of an anion-mixed hydridoborate, Na4(B10H10)0.5(B12H12)0.5. By exposing the hydridoborate to varying degrees of relative humidity (RH) of 30-70%, we find that hydration at 30% enables retention of its moderate Na-ion conductivity (∼0.7 mS/cm) while higher hydration levels lead to the separation of the two anions ([B10H10] 2− and [B12H12] 2−), resulting in significant disruption in the Na ion conduction pathways. X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (NMR) measurements indicate that hydration leads to the formation of distinct crystalline phases and alters the local ion coordination environments. The hydrated phase at 30% RH reversibly returns the original structure, restoring its ionic conductivity and compatibility with Na metal anodes. These findings provide insights into the role of structural water in Na-ion transport and a practical strategy for the use of moisturesensitive closo-hydridoborates solid state electrolytes.
Source: ChemRxiv
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
Awards: G102163711, G107546177, G1285306620, G1286251239, G1313983767, G1664757510, G171842289, G1847291448, G2287611682, G241279073, G262962599, G3075337988, G3262563802, G357145406, G426311843, G4562702224, G498139845, G5387317844, G5535608740, G5632581352, G5765906131, G6330817128, G6918803902, G6965541988, G7463374569, G7583137537, G993149817
OpenAlex ID: W7214888794