“…In the past, a number of Na + ion conducting PEO x ‐NaX polymer electrolytes has been investigated, where NaX is an inorganic salt and X stands for an anion such as I, SCN, Br, ClO 4 , NO 3 , PF 6 , PO 3 , BF 4 , YF 4 , CF 3 SO 3 , (CF 3 SO 2 ) 2 N, and (FSO 2 ) 2 N . The abbreviation, PEO corresponds to a high‐molecular‐weight poly(ethylene oxide) and x is the [O]/[Na + ] molar ratio.…”