It is shown that ionic conductivity of polymeric electrolytes based on low molecular weight amorphous
polyglycols can be modified by the addition of α-Al2O3 fillers containing surface groups of the Lewis acid
type. An enhancement of conductivity over pure PEG−LiClO4 electrolyte is observed for PEG−α-Al2O3−LiClO4 composite electrolytes containing from 0.5 to 3 mol/kg of the lithium salt. This increase in conductivity
is coupled with the lowering of the viscosity of composite electrolytes and increasing chain flexibility when
compared to the PEG−LiClO4 system as shown by rheological and DSC experiments. A decrease in the
fraction of ionic aggregates is also seen from the FT-IR experiments for composite electrolyte in this salt
concentration range. FT-IR studies of the C−O−C stretching mode has shown reduction in the transient
cross-link density obtained after the addition of α-Al2O3 in the salt concentration range corresponding to the
conductivity enhancement. The phenomena observed are explained in view of ion−ion and ion-polymer
interactions, involving dispersed filler particles, which are of the Lewis acid−base origin.
The effect of filler surface group on the conductivity, ion−ion, ion−polymer interactions, and microstructure
of PEG−LiClO4−Al2O3 composite polymer electrolytes is studied. It is shown that the addition of fillers
results in an increase in ionic conductivity of polyether electrolytes observed in the narrow lithium salt
concentration range. The position of conductivity maximum depends on the type of the surface groups of the
filler and results from the Lewis acid−base type interactions between filler surface centers, ions, and ether
oxygen base groups. These interactions are reflected by changes in the polymer chain flexibility observed by
DSC and rheological experiments as well as microstructural changes due to polymer−filler−Li+ interactions
as revealed by FT-IR experiments. Finally, the addition of the filler results in the changes in ionic associations
as studied by FT-IR and by applying the Fuoss−Kraus formalism to the salt concentration dependence of the
molar conductivity of the composite electrolytes studied.
In this paper, we present complementary series of crystal structures of lithium salts containing 4,5-dicyanoimidazolato anions substituted with perfluoroalkyl groups. Singlecrystal X-ray analysis of ten adducts with aprotic solvents: glymes -dimethyl ethers of poly(ethylene glycols) -and crown ethers have been performed to correlate their molecular structures and properties with spectroscopic and thermal data. Comprehensive structure analysis of crystalline materials reveals valuable information about coordination ability of substituted 4,5-dicyanoimidazolato anions and provides the basis to develop the model of poly(ethylene oxide) electrolytes and liquid systems. Presented results reveal new aggregation modes at high concentrations of lithium salts involving releasing cations by self-assembly of anionic subnetwork and shed some light on electrochemical performance of TDI anions.
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