Ion-ion, short-range interactions in PEO-LiX rubbery electrolytes containing LiSCN, LiN(CF3SO2)2 or Li[CF3SO2N(CH2)3OCH3] as deduced from studies performed on PEO-LiX-KX ternary systems

Conductivity and dc polarization studies performed on poly(ethylene oxide) PEO-LiX-KX amorphous electrolytes, containing LiSCN, LiN(CF3SO2)(2) (LiTFSI) or Li[CF3SO2N(CH2)(3)OCH3] (LiMPSA) and their potassium counterparts, yield data-composition relationships that can be fitted by means of classical models assuming ideality. Though this approach is not rigorous, it provides information about the nature and strength of the ion-ion, short-range interactions in the PEO-LiX corresponding systems. At the global concentration chosen for these studies, C similar to 0.8 mol dm(-3) (EO/salt=30), evidence is brought that stronger two-body interactions (ion pairing) lake place in the PEO-LiMPSA system than in the PEO-LiSCN system, and these interactions are much stronger than in the PEO-LiTFSI system. Another feature of these three systems lies in their three-body interactions, which appear to mainly consist of LiX2- triplets. Though their strength is not as great as that of the two-body interactions, it increases in the order LiTFSI < LiMPSA < LiSCN. (C) 2001 Elsevier Science Ltd. All rights reserved.