Abstract
The study of the interplay between structure and conductivity in lithium-conducting electrolytes is a pivotal point for the development of future secondary batteries [1]. The use of Glycerol as a low molecular weight component in electrolytes is particularly interesting due to its glass-forming behavior and low glass transition temperature (-78.5°C). In addition, a high flexibility of the alkyl backbone chain and the well-known capability of oxygen functionalities to coordinate lithium cations make Glycerol very appealing as ion-conducting media as well as building block to obtain hybrid polymer electrolytes [2].On this basis a family of eleven electrolytes based on Lithium Glycerolate with general formula C3H8-xO3Lix, where 0 ≤ x ≤ 1, is prepared and investigated [3]. In these electrolytes the Glycerolate (C3H8-xO3 x-) component acts as a large and flexible macro-anion which is able to provide a high single-ion conductivity to the material (8.36∙10-5 S∙cm-1 at 20°C and 1.55∙10-2 S∙cm-1 at 150°C for x = 0.25).Finally, the Glycerol∙∙∙Li+ interactions in these electrolytes are studied on T and x, with a particular reference to the detection of: a) macro-anion coordination sites; and b) the secondary structure of Glycerol chains. Insights on the long-range charge transfer mechanism and Glycerol relaxation events are also discussed.These studies are carried out by Inductively-Coupled Plasma Atomic Emission Spectroscopy, IR and Raman spectroscopies, DSC, TGA, and Broadband Electrical Spectroscopy.
Highlights
The major challenge for the improvement of lithium secondary batteries is the development of stable electrolytes capable of efficiently transferring Li ions in a wide range of temperatures.Polymer Electrolytes (PEs) seem to be the right answer thanks to their mechanical, thermal, chemical, and electrochemical stability, and good conductivity at room temperature [1,2]
0 ◦ C, even if modulated differential scanning calorimetry (MDSC) measurements do not reveal any thermal transition. This phenomenon temperature range (Tg ≤ T ≤ 0 °C), the structure assumed by the glycerol molecules facilitates the can be explained by considering that, at these concentrations of Li+ and in this particular σIP,1 polarization, making it the component providing the highest contribution to the overall temperature range (Tg ≤ T ≤ 0 ◦ C), the structure assumed by the glycerol molecules facilitates conductivity (Figure 9) and perturbing the log σT vs T−1 curve behavior
Vibrational spectroscopies (i.e., FT-IR and micro-Raman) allow for the interpretation of the coordination geometry assumed by glycerol molecules as a function of lithium concentration
Summary
Centro Studi di Economia e Tecnica dell’Energia Giorgio Levi Cases, Via Marzolo 9, I-35131 Padova (PD), Italy. Material Science and Engineering Department, Universidad Carlos III de Madrid, Escuela Politécnica Superior, Av.de la Universidad, 30, 28911 Leganes, Spain
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