Influence of Salt Anions on the Reactivity of Polymer Electrolytes in All-Solid-State Sodium Batteries

• Published in: Journal of the Electrochemical Society 2022-07, Vol.169 (7), p.70530
• Main Authors: Peta, Gayathri, Alon-Yehezkel, Hadas, Bublil, Shaul, Penki, Tirupathi Rao, Breuer, Ortal, Elias, Yuval, Fayena-Greenstein, Miryam, Aurbach, Doron
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1945-7111/ac8241

Solid-state batteries have received renewed attention in recent years. The present study compares all-solid-state sodium batteries containing sodium metal anodes, NaTi 2 (PO 4 ) 3 (NTP) cathodes and PEO polymer electrolyte (PE) with two salts—NaPF 6 and NaClO 4 . Electrochemical properties were determined by means of both AC and DC measurements. For fresh symmetric cells, it seems like using NaClO 4 as the salt leads to a lower interfacial resistance, but during contact with Na anodes, PEO:NaClO 4 PE produces an unstable interface whereas PEO-NaPF 6 forms a stable interface upon contact with sodium anodes. Battery prototypes with PEO:NaClO 4 showed a better performance than those using PEO:NaPF 6 in terms of specific capacity and energy content, as NaPF 6 produces HF by-product which impairs the performance of full cells. However, the use of composite solid electrolyte containing PEO:NaPF 6 and TiO 2 nanotubes alleviates detrimental effects of HF and thus enables a better performance of SS Na battery prototypes. This is probably due to the titania particles acting as a scavenger of HF, an inevitable contaminant in electrolyte systems containing PF 6 − anions. On adding TiO 2 to polymer electrolytes, of both salts, the performance improves, what means that the TiO 2 has several positive effects in these systems.