Ionic transport in NASICON-polymer hybrids: An assessment using X-ray photoelectron spectroscopy

Highlights: • XPS investigations on NASICON-polymer hybrids have been reported. • Cation interaction with ether oxygen of polymer has been studied. • XPS provides evidence for cations coupling/decoupling with polymer chains. X-ray photoelectron spectroscopy (XPS) has been used to assess the ion transport mechanism in Li⁺ and Na⁺ ion based solid polymer electrolytes. For this, NASICON dispersed polymer films of the type 5LiCF₃SO₃-95[PEO_1-xLATP_x] where 0 ≤ x ≤ 0.7, and pellets of 63NZSP-37[PEO_1yNaI_y] for y = 0.03–0.13 have been synthesized. It has been observed that the O 1s spectra corresponding to ether oxygen of PEO provides an evidence of cation-polymer chain interaction. The trends of the binding energy of O 1s for ether oxygen of PEO suggest decoupling of cations from polymer chain for large NASICON content in the matrix. Such evidence readily provides an understanding of ionic transport mechanism in these Na⁺/Li⁺ ion based hybrid polymer-NASICON composites. It is suggested that during electrical transport, cations couple with the polymer chains for low NASICON content in the matrix. Whereas, for higher content, they decouple from ether oxygen and prefer NASICON surface/bulk states for electrical transport. The ionic transport number measurements and electrical transport studies (233–300 K) on these composites compliment the proposed decoupling for high NASICON content samples.