Polyether, Poly(N,N-dimethylacrylamide), and LiClO₄ Composite Polymeric Electrolytes

Abstract

The results of detailed studies of the ionic conductivity, ultrastructure, and morpholgy of polyether-poly(N,N-dimethylacrylamide)-LiClO4 electrolytes are presented and discussed. These composite electrolytes have been studied using differential scanning calorimetry (-110-150 °C), with FT-IR spectroscopy (20-85 °C) and impedance analysis (-20-100 °C). Room temperature FT-Raman spectroscopy, SEM, and X-ray energy dispersive studies have also been performed. Highly crystalline poly(ethylene oxide) and amorphous or low-crystalline oxymethylene-linked poly(ethylene oxide) are used as polyether matrices for composite electrolytes. It is shown that interactions of lithium cations with polyether oxygens and the carbonyl oxygens of the "filler" poly(N,N-dimethylacrylamide) lead to the formation of various types of complexes. These interactions can be classified as Lewis acid-base reactions. The formation of different types of complexes modifies the ultrastructure and enhances the subambient and ambient temperature ionic conductivity of these electrolytes in comparison to the pure polyether-LiClO4 electrolyte. The increase in the conductivity is attributed to the presence of a highly flexible uncomplexed polyether phase surrounding filler particles. The temperature dependence of ionic conductivity is Arrhenius at ambient and subambient temperatures and VTF at higher temperatures. The order-disorder transition temperature calculated on the basis of a semiempirical model is found to be equal to the onset temperature of the melting peak of the crystalline poly(ethylene oxide) for these semicrystalline electrolytes or equal to 1.2 times the glass transition temperature of the polyether-LiClO4 electrolyte for the corresponding amorphous systems. Assuming that the enhanced conductivity of these composite polymer electrolytes is associated with interphase phenomena, the conductivity results were analyzed in terms of a model based on effective medium theory.

Sol–gel preparation of a di-ureasil electrolyte doped with lithium perchlorate

“…1(b) and Table 2). The 930-931 cm -1 band, which remains at the same position in all the FT-Raman spectra irrespective of the salt concentration, is assigned to "free" ions [23][24][25][26][27][28][29][30]. The shoulder at 924-926 cm -1 , present in the FT-Raman spectra of all the samples analyzed, has only been reported in the literature by Brooker et al [30] who assigned it to a 2ν 2 ClO 4 mode.…”

“…This anion has a tetrahedral symmetry and the nine vibrational degrees freedoms are distributed into four normal modes: Upon coordination, the ν 1 (A 1 ) band was found to shift to higher wavenumbers [23][24][25][26][27][28][29][30].…”

Ionically conducting polyether composites

“…The overall objective has been to understand the role of the filler additives (organic and inorganic powders and high molecular weight polymers with special properties) in ionic conduction in these composite PEO-based electrolytes. Various aspects of this work have been reported previously in different publications (8)(9)(10)(11)(12). This paper assembles all of the relevant results from these publications for the purpose of discussing and comparing physical and chemical properties.…”

“…Despite the ease of preparation of composite systems such as those discussed in this report, the problem of the mechanism of ionic conduction in such systems is even more acute. The best that we have been able to do is to use an "effective medium" theory (EMT) approach (7,(9)(10)(11)18). This approach has had some success and has been applied assuming that the PEO-polyacrylamide (PAAM or NNPAAM) composites contain three components with different electrical properties.…”

“…For these composites the order-disorder temperature (TD) is the temperature at which a change in the conduction mechanism is expected. TD can be calculated using a semiempirical approach (11,19), which yields a linear relationship between the natural logarithm of the conductivity preexponential factor (In a,) and the Arrhenius activation energy for conduction (E,), and which includes such parameters as TD, the theoretical cation and anion concentrations, and the frequency of oscillation of the ions as they await the next activated step, For example, for the PEO-PAAM-NH,SCN composite a linear relation between In uo and E, has been found for both the experimentally determined dc conductivity and the value of conductivity obtained from the EMT model. The characteristic temperatures TD calculated from both data sets agree and are equal to 71°C.…”