Optimizing structural and cycling stability in sodium-ion batteries using tailored glass fiber separators

In sodium-ion battery technology, glass fiber separators, known for their porous structure, are widely used due to their reduced capacity degradation, contrasting with commercial polyolefins which often face liquid absorption issues. To augment structural stability, we have engineered a commercial glass fiber separator, integrating an optimal quantity of oxide nanoparticles, such as silica with poly (vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP, wherein PVDF-HFP serves as a binding agent. In pursuit of making solid-state, we additionally layered the composite separator with 4 wt.% PVDF-HFP polymer coating and suffused it with a polydopamine solution to reduce the hydrophobicity of the PVDF-HFP polymer. The sodium vanadium phosphate (Na||NVP) cell, equipped with the as developed solid-state composite glass fiber separator with carbonate-based conventional electrolyte, has exhibited a commendable capacity of 73.4 mAh/g, maintaining 90.5% of this capacity after 200 cycles at a 1C rate. This impressive cycling performance is attributed to the forming of a stable cathode-electrolyte interphase (CEI) layer, as elucidated through X-ray photoelectron spectroscopy (XPS) analysis.