Investigation of ionic conduction in PEO–PVDF based blend polymer electrolytes

Abstract

We investigate the effect of blend host polymer on solid polymer electrolyte (SPE) films doped with ammonium iodide (NH4I) salt using a variety of experimental techniques. Structural studies on the composite SPEs show that the blending of Poly(ethylene oxide) (PEO)–Poly(vinylidene fluoride) (PVDF) polymers in a suitable ratio enhances the amorphous fraction of the polymer matrix and facilitates fast ion conduction through it. We observe that the addition of a small amount of PVDF in the PEO host polymer enhances the ion – polymer interaction leading to more ion dissociation. As a result, the effective number of mobile charge carriers within the polymer matrix increases. Systematic investigation in these blend SPEs shows that the maximum conductivity (1.01 × 10–3 S/cm) is obtained for PEO – rich (80 wt. % PEO, 20 wt. % PVDF) composites at 35 wt. % NH4I concentration at room temperature. Interestingly, at higher salt concentrations (above 35 wt. %), the conductivity is found to decrease in this system. The reduction of conductivity at higher salt concentrations is the consequence of decrease in the carrier concentration due to the formation of an ion pair and ion aggregates. PVDF–rich compositions (20 wt. % PEO and 80 wt. % PVDF), on the other hand, show a very complex porous microstructure. We also observe a much lower ionic conductivity (maximum ∼ 10–6 S/cm at 15 wt. % salt) in these composite systems relative to PEO-rich composites.

Dielectric polarization and relaxation processes of the lithium-ion conducting PEO/PVDF blend matrix-based electrolytes: effect of TiO2 nanofiller

“…Each arc represents the equivalent parallel combination circuit of an energy storing element C p and a dissipating element R p . The shapes of these impedance plots are found in good resemblance with that of the several similar types of electrolyte [14,26,30,32,35,43,69]. Further, the shape of the Nyquist plot of NSPE20 film indicates that the arc and spike parts in the plot are not clearly separable as usually noted for the other electrolytes which reflect that there may be few stiffer domains on the film surfaces resulting in poor electrode/electrolyte contact [70].…”

“…The micrograph of NSPE0 film (Fig. 1a) shows that there are macro-sized spherulites (some are encircled) which represent the crystallites of PEO blended with PVDF [42], although, the pristine PEO and PVDF films exhibit highly distinguishable spherulites surrounded by the amorphous amount of these polymers [14,42,72]. The interconnected spherulites of the NSPE0 film evidence cross-linked chain structures of the blended polymers through ion-dipole complexes due to which a large amount of these polymers crystals turn into amorphous content.…”

“…Many approaches such as the use of polymer blends as promising host matrices [13][14][15][16][17][18][19], inclusion of inorganic and organic nanofillers for improving thermal, mechanical, and ion transportation properties [20][21][22][23], the addition of various ionic liquid and/or dipolar liquid plasticizers for increasing degree of salt dissociation and reducing the crystallinity of polymer matrix [24][25][26][27], and consideration of different preparation methods suitable from the industrial point of view [28][29][30][31][32][33]. Furthermore, some combinations of these different approaches have also been taken into consideration for exploiting different kinds of SPE materials with a variety of appealing properties [17,20,26,34].…”

“…Among these approaches, the blending of polymers and their use as host matrices for the preparation of appropriate properties SPEs is a valid and more feasible green chemistry process that has been exemplified by various research groups [10, 17-21, 26, 29, 32]. The blending process not only suppresses the unwanted properties of individual polymers but also enhances the required superior properties that can be engineered through an appropriate compositional weight ratio of the blended polymers [14,17,18,35,36]. The addition of nano-sized fillers in the host polymer matrix is also a widely popular and efficient strategy to get improved physicochemical properties of the prepared NSPE materials [6,10,18,22,30,37].…”

The synergistic effect of the PEO–PVA–PESf composite polymer electrolyte for all-solid-state lithium-ion batteries

“…[5][6][7][8][9] However, the low room temperature conductivity (10 À7 to 10 À6 S cm À1 ), narrow electrochemical windows and inferior mechanical properties of PEO are the main obstacles for further development. 4,7,9 Blending is one of the valid approaches to ameliorate the properties of PEO, such as with PVP, 10 PVDF, 11 and PMMA; 12 this can decrease crystallization and enhance the fractional movement of polymer chains and the migration amount of Li + . 13 Similar to PEO, polyvinyl alcohol (PVA) is another semicrystalline polymer with the fascinating properties of nontoxic, water solubility and biocompatibility; it has been under the spotlight and applied as an electrolyte in supercapacitors on a large scale.…”