Mixed-alkali effect and short-range interactions in amorphous poly(ethylene oxide) electrolytes

摘要: Abstract When dissolved in polyethylene oxide) (PEO), the alkali metal imides LiN(CF 3 SO 2 ) (LiTFSI), NaN(CF (NaTFSI) and KN(CF (KTFSI) yield rubbery electrolytes over a wide range of concentrations at T > 50 °C. Both glass transition temperature ( g dc bulk conductivity these exhibit weak dependence on cation size. Although similar involving less delocalized anions eg , thiocyanate triflate anions) also exhibits size, their decreases markedly with increasing charge density. To clarify this point, study was performed PEO amorphous containing binary salt mixtures (KTFSI-LiTFSI KSCN-LiSCN) various molar ratios. Over examined (0.6–1.6mol/kg), data PEO-KTFSI-LiTFSI are comparable to those one-salt electrolytes. In turn, PEO-KSCN-LiSCN strong, negative deviation from additivity. By analogy molten mixtures, it is proposed that both cation-size effect PEO-MSCN caused by low-energy, short-range interactions associated anion polarization.