Thermal Stability, Complexing Behavior, and Ionic Transport of Polymeric Gel Membranes Based on Polymer PVdF-HFP and Ionic Liquid, [BMIM][BF₄]

Abstract

PVdF-HFP + IL(1-butyl-3-methylimidazolium tetrafluoroborate; [BMIM][BF(4)]) polymeric gel membranes containing different amounts of ionic liquid have been synthesized and characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared (FTIR), differential scanning calorimetry, thermogravimetric analysis (TGA), and complex impedance spectroscopic techniques. Incorporation of IL in PVdF-HFP polymer changes different physicochemical properties such as melting temperature (T(m)), thermal stability, structural morphology, amorphicity, and ionic transport. It is shown by FTIR, TGA (also first derivative of TGA, "DTGA") that IL partly complexes with the polymer PVdF-HFP and partly remains dispersed in the matrix. The ionic conductivity of polymeric gel membranes has been found to increase with increasing concentration of IL and attains a maximum value of 1.6 × 10(-2) S·cm(-1) for polymer gel membrane containing 90 wt % IL at room temperature. Interestingly, the values of conductivity of membranes with 80 and 90 wt % of IL were higher than that of pure IL (100 wt %). The polymer chain breathing model has been suggested to explain it. The variation of ionic conductivity with temperature of these gel polymeric membranes follows Arrhenius type thermally activated behavior.

Safer Electrolytes for Lithium‐Ion Batteries: State of the Art and Perspectives

“…[255][256][257][258][259] Concerning the utilization of "inactive" polymerm atrices, such as PVdF-HFP, the enhanced conductivity for ac ontrolled amount of added IL was assigned to the increased number of chargec arriers, as supported by the presence of strong electron-withdrawing functionalg roups,s uch as ÀCÀF( and their high dielectric constant, e = 8.4);t his leads to extendedl ithium salt dissolution, and thus, compensates for decreased ion mobility due to increased viscosity. [260] Nevertheless,d espite their highly favorable electrochemical and, in particular,s afety characteristics, such IL-SPE electrolyte systemss uffer two major issues:1 )a relatively low ionic conductivitya ta na mbient temperature of around 10 À4 Scm À1 , which is commonly not sufficientf or practical applications (ionic conductivities comparable to those of liquid,c arbonatebased electrolytes mayb ea chieved at 70 8C); [169,232] and 2) incompatibility with state-of-the-art cathode materials, which reversibly (de-)insertingl ithiumi ons at potentials highert han 4V ,f or instance, Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 , [261] limiting their utilization so far to active materials such as LiFePO 4 [258,[262][263][264] LiFe 1Àx Mn x PO 4 , [265] LiMnPO 4 , [266] or vanadium oxides [267,268] .…”

Electrode–Electrolyte Interfacial Processes in Ionic Liquids and Sensor Applications

“…Those conformation differences are present in the fingerprint region of IR (under 1,000 cm ) [112][113][114][115]. B-F of BF 4 is located at 924 cm −1 and 1,312 cm −1 , and P-F of PF 6 is about 843 cm −1 [116][117][118][119]. For cations, the bands are located in the rest of the regions and address the IL structure, such as C-C (around 1,450 cm ).…”

Ionic Liquid Enhancement of Polymer Electrolyte Conductivity and their Effects on the Performance of Electrochemical Devices

“…The electrolyte displayed ionic conductivity of the order 10 The BMImBF 4 ionic liquid [7] conductivity was expected to decrease on addition of PVdF-HFP to the IL. This is because, on adding polymer to the IL will increase the IL viscosity.…”