Query: PVDF-HEP Ionic Liquid

title: Effect of Na+ MMT ionic liquid synergy on electroactive, mechanical, dielectric and energy storage properties of transparent PVDF based nanocomposites
abstract: Transparent dielectric composites with high electroactive, low dielectric loss and high energy density are highly desirable due to the potential applications in electronic and electric industry. In this work, simultaneously achieving excellent electroactive, high dielectric and energy storage performance in a transparent dielectric composite is proposed by compounding nano montmorillonite (Na+ MMT) and ionic liquid (IL) with poly (vinylidene fluoride) (PVDF) through one step melt blending technique. The microstructure, crystal forms, transparency, mechanical, dielectric and energy storage performances of PVDF/MMT/IL nanocomposites were systematically investigated. The existence of IL and shearing force contributes to the effective exfoliation of MMT in the PVDF matrix. Based on the synergy of Na+ MMT and IL, the PVDF/IL/MMT composites not only exhibited almost 100% polar phase PVDF but also the optical transmittance was significantly enhanced. The improved dielectric constant and reduced dielectric loss were successfully achieved in the PVDF/IL/MMT nanocomposites due to the inhibition of ion migration by exfoliated silicate layers. Moreover, the PVDF/IL/MMT nanocomposite exhibited improved energy storage performance compared with the nanocomposites containing IL or Na+ MMT independently. Therefore, the PVDF/IL/MMT nanocomposite with high electroactive, excellent transparency, high dielectric and energy storage performance shows potential applications in microelectronic device.

title: Conduction mechanism in polymeric membranes based on PEO or PVdF HFP and containing a piperidinium ionic liquid
abstract: Two types of polymer electrolyte membranes were prepared using poly(ethylene oxide) (PEO) and poly(vinylidene difluoride co hexafluoropropylene) (PVdF HFP) with different amounts of the ionic liquid N methyl N propylpiperidinium bis(trifluoromethane sulfonyl) imide [PP13][TFSI] added. The results from differential scanning calorimetry and conductivity measurements show that in the case of PVdF HFP membranes the glass transition temperature T g decreases and the room temperature ionic conductivity increases with increasing content of the ionic liquid (up to 60 wt. However, in the case of PEO based membranes Tg is less significantly affected and the room temperature ionic conductivity increases only up to 30 wt. of ionic liquid, beyond which a steady value of about 5.10( 5) S/cm is reached. The results from Raman spectroscopy show that the characteristic vibrational mode of the TFSI anion at similar to 742 cm( 1) is weakly affected in the membranes prepared from PVdF HFP, whereas for those based on PEO it has a clearer composition dependence. These results suggest ion ion and ion polymer interactions of different nature, which together with the different nanomorphologies adopted by PEO and PVdF HFP, as revealed by X ray scattering, give rise to different composition dependences of the macroscopically measured ionic conductivity.

title: Development of strain sensor using conductive poly(vinylidene fluoride) (PVDF) nanocomposite membrane reinforced with ionic liquid (IL) carbon nanofiber (CNF)
abstract: High sensitivity and good mechanical strength are required for conductive polymer nano composites (CPNC) based flexible strain sensors. Here we have developed CPNC membranes using PVDF as a base polymer along with carbon nanofiber (CNF) and ionic liquid (IL) as conducting fillers exhibiting good thermal stability, high sensing voltage, and mechanical performance for strain sensors. The IL infiltration in PVDF and CNFs composition resulted in micro porous morphology that exhibited stretchability (maximum elongation 5.8 mm) and a high gauge factor (4.08) (property of a good strain sensor) Further, infiltration of IL in PVDF/CNF membrane brings microstructural changes (a to b phase) of PVDF and provides an electrolyte mixture of CNF and IL for the facile flow of ions through it. The CNFs in CPNC having IL helped in maintaining the crack initiation during strain. Hence, the deformed CNFs across the pores or within the PVDF act as an interlinking agent and provides an electrical conduction pathway in the shrink lattice of the composite.

title: Density functional theory studies on PVDF/ionic liquid composite systems
abstract: Density functional theory calculations with and without dispersion correction were performed to describe the effect of the addition of ionic liquids (ILs) to polyvinylidene fluoride (PVDF) molecules. All the calculations were carried out for four monomer units of \upalpha $a and \upbeta $b PVDF and 1 n alkyl 3 methylimidazolium tetrafluoroborate \hbox {C}_{\mathrm{n}\hbox {MIM}$CnMIM] \hbox {BF}_{4}$BF4] (n 2, 4, 6, 8, 10) ionic liquids. Dispersion correction is found to be essential to describe ion pair (within the IL molecule) interaction and polymer ionic liquid interaction. Frontier orbitals (HOMO, LUMO) compositions and energies were obtained for individual PVDF molecules, ionic liquids and ionic liquid added polymer complexes to demonstrate the variation in different chemical parameters like hardness, softness, chemical potential, electronegativity, the electron affinity of the systems. Mulliken and atomic dipole moment corrected Hirschfeld population analyses were carried out to provide a quantitative analysis of partial atomic charge distribution. Molecular electrostatic potential plots, mapped on to total electron density surfaces, are provided to depict the reactive parts of the molecules under study. Natural bond orbital analysis was also carried out to quantify the extent of electron delocalization caused by PVDF IL anion and PVDF IL cation weak interactions. Dispersion corrected DFT studies were performed to show why the addition of ionic liquids (IL) help in polar \upbeta $b PVDF crystallization. Analyses were carried out for 1 n alkyl 3 methylimidazolium tetrafluoroborate \hbox {C}_{\mathrm{n}\hbox {MIM}$CnMIM]\hbox {BF}_{4}$BF4] n 2,4,6,8,10) ILs and four monomer units of \upalpha $a and \upbeta $b PVDF using 6 311+G(d,p)/B3LYP D. Obtained results suggest ILs show better interaction with \upbeta $b PVDF than \upalpha $a PVDF.

title: Effect of annealing treatment on crystalline and dielectric properties of PVDF/PEG containing ionic liquid composites
abstract: To investigate the effect of poly(ethylene glycol) containing ionic liquid (IL) and thermal annealing treatment on crystallization and dielectric relaxation behavior of poly(vinylidene fluoride) (PVDF) a series of PVDF/IL composites have been prepared using a solution cast method. The interaction between imidazolium cation of ILs and >CF2 groups of PVDF can transfer nonpolar a phase to polar b and g phase as a template at the primary crystallization, and then the interaction between PEG of ILs and >CF2 groups of PVDF can facilitate the PVDF chains in amorphous region to bring more polar phase and decrease the degree of crystallization for PVDF composites according to the template under thermal annealing treatment. The experimental dielectric data were analyzed within the formalisms of complex permittivity and electric modulus. In the frequency spectra of PVDF composites, dc conductivity, electrode and Maxwell Wagner Sillars (MWS) interfacial polarization resulted in high values of dielectric permittivity. The incorporation of ILs into the matrix and thermal annealing treatment can accelerate dc conductivity. The temperature dependence of relaxation time of dc conductivity follows the Arrhenius equation. The effect of annealing treatment on charge carrier movement mechanism was resulted from the increase of ion mobility induced by polymer chain segmental motion and polar phase crystals.

title: Effect of SiO2 Nanoparticles on the Performance of PVdF HFP/Ionic Liquid Separator for Lithium Ion Batteries
abstract: Safety concerns related to the use of potentially explosive, liquid organic electrolytes in commercial high power lithium ion batteries are constantly rising. One promising alternative is to use thermally stable ionic liquids (ILs) as conductive media, which are however, limited by low ionic conductivity at room temperature. This can be improved by adding fillers, such as silica or alumina nanoparticles (NPs) in the polymer matrix that hosts the IL. To maximize the effect of such NPs, they have to be uniformly dispersed in the matrix while keeping their size as small as possible. In this work, starting from a water dispersion of silica NPs, we present a novel method to incorporate silica NPs at the nanoscale level <200 nm) into PVdF HFP polymer clusters, which are then blended with the IL solution and hot pressed to form separators suitable for battery applications. The effect of different amounts of silica in the polymer matrix on the ionic conductivity and cyclability of the separator is investigated. A membrane containing 10 wt. of silica (with respect to the polymer) was shown to maximize the performance of the separator, with a room temperature ionic conductivity of of 1.22 mS cm 1. The assembled half coin cell with LiFePO4 and Li as the cathode and the anode exhibited a capacity retention of more than 80% at a current density of 2C and 60 C.

title: PVdF HFP and Ionic Liquid Based, Freestanding Thin Separator for Lithium Ion Batteries
abstract: Lithium ion batteries are the key for modern electricity based transportation systems and more generally for sustainable large scale energy applications. However, typical commercial batteries seldom meet safety regulations because of the presence of organic, flammable, and volatile liquid electrolytes, and viable alternatives need to be found. Ionic liquids (IL) are considered to be one of the most promising candidates, when combined with a polymer matrix to form the so called gel polymer electrolyte, working as separator. Along this line, a new, purely water based methodology has been developed in this work to produce thin separators. This involves the formation of fractal polymer clusters (PCs) through intense shear driven gelation of poly(vinylidenefluoride co hexafluoropropylene) (PVdF HFP) nanoparticles in water, impregnation of the IL (Pyr13TFSI LiTFSI) solution into the dried PCs, and hot pressing to form continuous, porous, and transparent membranes. Because of the large amount of pores generated

title: PVDF ionic liquid modified clay nanocomposites: Phase changes and shish kebab structure
abstract: Crystalline behaviour of PVDF nanocomposite with 1 alkyl 3 methylimidazolium modified montmorillonite clay was analyzed. The phase change from a to b increased with alkyl chain length of the organic modifier in the filler; 1 alkyl 3 methylimidazolium clay and maximum conversion (99% was observed for PVDF 1 hexadecyl 3 methylimidazolium modified clay composite with 2% loading. The phase conversion was evident from X ray diffraction, DSC analysis and improved electrical properties. AFM analysis of PVDF 1 butyl 3 methylimidazolium montmorillonite clay composite (PVDF C4) showed a shish kebab structure while pristine PVDF and all other composites showed spherulite structures. Computational studies revealed that the extended chain a phase forms the 'shish' the back bone and folded chain b phase forms the 'kebab' This was further supported by the superior mechanical properties for PVDF C4 composite. Present work shows that introducing ionic liquid modified MMT clay within the PVDF matrix enables nucleation of electroactive b phase and the presence of equal content of a and b phases can lead to the formation of self reinforced shish kebab structures in PVDF.

title: Improving supercapacitor capacitance by using a novel gel nanocomposite polymer electrolyte based on nanostructured SiO2, PVDF and imidazolium ionic liquid
abstract: The data presented in this work show the preparation of an electrochemical double layer capacitor with improved capacitance employing an ionic liquid based composite gel polymer electrolyte containing nanostructured SiO 2 The composite gel electrolyte has good self standing characteristics, conductivity, electrochemical window and high thermal stability. The use of this electrolyte promotes an increase of about 72% in the device capacitance compared to a capacitor prepared with the gel electrolyte without SiO 2 at ambient temperature. The cell is very stable when cycled at a high current density (1.0 A g 1 since it loses only 9% of its initial capacitance after 2000 cycles, with values of energy and power density of 32.2 Wh kg 1 and 0.9 kW kg 1 respectively. Additionally, the SiO 2 based electrolyte allows the capacitor to be used at high temperature (100 degC) with a superior performance without ionic liquid leakage. Therefore, the use of such composite gel electrolyte makes possible the construction of miniaturized, safe and completely solid state devices.

title: Effect of EMIMBF4 ionic liquid addition on the structure and ionic conductivity of LiBF4 complexed PVdF HFP polymer electrolyte films
abstract: New polymer electrolyte films of lithium tetrafluoroborate (LiBF4) complexed poly(vinylidene fluoride co hexafluoropropylene) (PVdF HFP) embedded with different quantities of 1 ethyl 3methylimidazolium tetrafluoroborate (EMIMBF4) ionic liquid were prepared by solution casting. The prepared films were characterized using various techniques: X ray diffraction, scanning electron microscopy, impedance spectroscopy and electrochemical measurements. The pure PVdF HFP possessed a semi crystalline structure and its amorphicity increased with the addition of LiBF4 salt and EMIMBF4 ionic liquid. The size and interconnection of pores in the films were enhanced by EMIMBF4. Impedance measurements indicated that the room temperature ionic conductivity of the films increased with increasing EMIMBF4 concentration until 15 wt. being up to 0.202 x 10 4 S cm 1, and then decreased with further increasing EMIMBF4 concentration. In addition, the temperature dependent ionic conductivity of the polymer electrolyte films followed an Arrhenius relation and the 15 wt. EMIMBF4 incorporated gel polymer electrolyte film exhibited a low activation energy for ionic conduction, being about 0.28 eV. Finally, the electrochemical stability window of the 85PVdF HFP:15LiBF4+15 EMIMBF4 gel polymer electrolyte films was evaluated as approximately 4.4 V, which is a promising value for ion battery applications.