Polyether Single and Double Crystalline Blends and the Effect of Lithium Salt on Their Crystallinity and Ionic Conductivity

Abstract

In this work, blends of Poly(ethylene oxide), PEO, and poly(1,6-hexanediol), PHD, were prepared in a wide composition range. They were examined by Differential Scanning Calorimetry (DSC), Polarized Light Optical Microscopy (PLOM) and Wide Angle X-ray Scattering (WAXS). Based on the results obtained, the blends were partially miscible in the melt and their crystallization was a function of miscibility and composition. Crystallization triggered phase separation. In blends with higher PEO contents both phases were able to crystallize due to the limited miscibility in this composition range. On the other hand, the blends with higher PHD contents display higher miscibility and therefore, only the PHD phase could crystallize in them. A nucleation effect of the PHD phase on the PEO phase was detected, probably caused by a transference of impurities mechanism. Since PEO is widely used as electrolyte in lithium batteries, the PEO/PHD blends were studied with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), and the effect of Li-salt concentration was studied. We found that the lithium salt preferentially dissolves in the PEO phase without significantly affecting the PHD component. While the Li-salt reduced the spherulite growth rate of the PEO phase within the blends, the overall crystallization rate was enhanced because of the strong nucleating effect of the PHD component. The ionic conductivity was also determined for the blends with Li-salt. At high temperatures (>70 °C), the conductivity is in the order of ~10−3 S cm−1, and as the temperature decreases, the crystallization of PHD was detected. This improved the self-standing character of the blend films at high temperatures as compared to the one of neat PEO.

Biopolymeric hydrogel electrolytes obtained by using natural polysaccharide–poly(itaconic acid-co-2-hydroxyethyl methacrylate) in deep eutectic solvents for rechargeable Zn–air batteries

“…This is because the little crystalline order exhibited by the amorphous phase facilitates the movement of the ions. 45,46 Therefore, the results suggest that the biohydrogel with inulin will be the most conductive, followed by PIA-DEX, and the least conductive would be PIA-ALG, as was predicted by the thermogravimetric study. Finally, all the PIA biohydrogels were tested at pH 4, 7, and 10 to verify their water retention capability.…”

In‐situ Polymerized Single Lithium‐ion Conducting Binder as an Integrated Strategy for High Voltage LNMO Electrodes

“…The characteristic BO 4 − band exhibits a slight shift towards higher wavenumbers as the amount of LNMO increased, confirming the presence of two distinct chemical environments of BO 4 − , consistent with the findings from ss‐NMR analysis. Furthermore, the ionic conductivity of SLICPB is similar and in some cases superior to that of other polymer electrolytes (table S1), [35–38] with the advantage to having the transport number close to unity at all temperatures, confirming its single‐ion conducting capability (Figure 1c and d). [39] …”

Investigating the Physical State of Polymer Electrolyte: Influence of Temperature and LiTFSI Concentration on the Phase of the Different States of the Polymer Electrolyte PEO-LiTFSI

“…Note that larger endothermic peaks mean the crystallite fusion starts at a "low" temperature (∼66 °C), even if the peak temperature reaches higher values (∼90 °C). J. Olmedo-Martinez et al have reported that the increase in w e induces the decrease of the mechanical properties of the polymer 75 because the LiTFSI acts as a plasticizer. 76 Therefore, the melting temperature of the crystallites of the electrolyte should continuously decrease if the lithium salt is completely dissociated, which is not true experimentally at high w e .…”