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The present work is aimed at developing the Zn-ion-conducting solid polymer electrolyte (SPE) films based on PVdF-HFP/Zn(Tf)2 complex system via solution casting method. The structural and morphological characteristics of the as-prepared films are elucidated by X-ray diffraction and scanning electron microscopy. Further, impedance spectroscopy and cyclic voltammetry are performed to investigate their electrical and electrochemical properties. The structural analysis confirms that the PVdF-HFP is semi-crystalline and its amorphous domain increases with the addition of Zn(Tf)2 salt. The impedance results reveal that the ionic conductivity of the electrolyte film is raised up to a maximum value of 2.44 × 10–5 S cm−1 at room temperature when the mass ratio of Zn(Tf)2:PVdF-HFP is 0.4 (named as PE/Zn-4). However, further loading of salt degrades the overall properties of the film. Hence, the PE/Zn-4 system is regarded to be the optimal composition for efficient SPE films. Additionally, the PE/Zn-4 electrolyte exhibits sound thermal stability and mechanical properties. The electrochemical stability window of the PE/Zn-4 system is evaluated as approximately 3.45 V, being acceptable for energy storage applications. In addition, the present polymer electrolyte may well suppress the formation of Zn dendrites on Zn electrodes. Conclusively, the development of high-performance SPEs could be potentially very useful for the next-generation Zn-based devices. [ABSTRACT FROM AUTHOR]

A biodegradable gel polymer electrolyte system based on chitosan/magnesium trifluoromethanesulfonate/1-ethyl-3-methylimidazolium trifluoromethanesulfonate (CA/Mg (Tf) 2 /EMITf) is developed. The structure, thermal performance, mechanical properties, ionic conductivity, relaxation time, electrochemical stability and ionic transport number of the membranes are analyzed by various techniques. The ion migration mainly depends on the complexation and decomplexation of Mg 2+ with amine band (NH 2 ) in chitosan. The 90CA-10Mg (Tf) 2 system plasticized with 10% EMITf (relative to the amount of 90CA-10Mg (Tf) 2 ) is identified as the optimum one and the temperature dependence of ionic conductivity obeys the Arrhenius rule. Moreover, the relaxation time of the electrolyte is very short, being just 1.25 × 10 −6 s, and its electrochemical stability window is quite wide, being up to 4.15 V. The anodic oxidation and cathodic reduction of Mg at the Mg-electrode/electrolyte interface is facile, and the ionic transference number of this electrolyte is 0.985, indicating that it could be a potential electrolyte candidate for Mg-ion devices. [ABSTRACT FROM AUTHOR]

The influence of ethylene carbonate (EC) addition on 85poly(ε - caprolactone):15Lithium thiocyanate (85PCL:15LiSCN) polymer electrolyte is investigated using X-ray diffraction, impedance spectroscopy, Wagner's polarization and electrochemical measurements. The results reveal that the amorphicity of the 85PCL:15LiSCN system increases with increase of EC content up to an optimal level of 40 wt.%. This is reflected in the electrical properties of the gel polymer electrolytes, i.e., the 40 wt.% EC-incorporated gel polymer electrolyte exhibits both high amorphicity and high electrical conductivity as compared to the other samples. The EC concentration dependences of dielectric constant and electrical conductivity show a similar trend, indicating that these properties are closely related to each other. The total ionic transference numbers of EC-incorporated gel polymer electrolytes are in the range 0.989–0.993, demonstrating that they are almost completely ionic conductors. The electrochemical stability window of the 40 wt.% EC-incorporated gel polymer electrolyte is ∼4.1 V along with the electrical conductivity of 2.2 × 10 −4 S cm −1 , which is significantly improved as compared to the 85PCL:15LiSCN system (3.0 V and 1.04 × 10 −6 S cm −1 ). Consequently, the addition of EC in the 85PCL:15LiSCN polymer electrolyte leads to a promising improvement in its various properties. [ABSTRACT FROM AUTHOR]

Lithium ion conducting biodegradable gel polymer electrolytes based on a poly (ε-caprolactone):lithium tetrafluoroborate (PCL:LiBF) system doped with various concentrations of 1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF) ionic liquid were prepared by solution cast technique. The gel polymer electrolyte was eco-friendly, flexible, transparent and free-standing. The conductivity and transference number measurements were carried out to investigate ionic conduction and charge transport in the gel polymer electrolytes. The frequency-dependent conductivity results revealed that the room-temperature electrical conductivity increased with increasing EMIMBF concentration. At room temperature, the gel polymer electrolyte with a composition of 85PCL:15LiBF + 40EMIMBF exhibited a high conductivity value of approximately 2.83 × 10 S cm, which was favored by the rich amorphous phase as confirmed with X-ray diffraction analysis. The lithium ion transport number and electrochemical stability of the 40 % EMIMBF gel polymer electrolyte were 0.43 and 3.7 V, respectively. These values are acceptable and quite enough for practical device applications. Consequently, the 40 wt% EMIMBF incorporated gel polymer electrolyte could be used to fabricate lithium ion batteries with a suitable selection of other components of the battery system. [ABSTRACT FROM AUTHOR]

Lithium ion conducting polymer electrolyte films based on biodegradable poly(ɛ-caprolactone) (PCL) complexed with lithium thiocyanate (LiSCN) salt were prepared by solution cast technique. Thermal and electrical properties of the polymer electrolyte films were studied using differential scanning calorimetry (DSC) and ac impedance spectroscopy. In order to investigate the ion conduction mechanism and relaxation behavior of complex polymer electrolyte films, the conductivity, dielectric constant, loss tangent and electric modulus were analyzed as a function of frequency and temperature. The variation of conductivity with frequency obeyed the Johnscher's power law. The dielectric constant exhibited a higher value at a lower frequency and increased with rising temperature due to the polar nature of host polymer. The activation energies for both dc conductivity and relaxation had the same value (∼0.87 eV), implying that the charge carriers responsible for both conduction and relaxation were the same. [ABSTRACT FROM AUTHOR]

In this study, novel ionic liquid-incorporated Zn-ion conducting polymer electrolyte membranes containing polymer matrix poly (vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf), along with zinc trifluoromethanesulfonate Zn(Tf)2, are prepared and investigated. It is ascertained that the optimal membrane ILPE-Zn-4 (the mass ratio of EMITf:Zn(Tf)2:PVDF-HFP is 0.4:0.4:1), with abundant nanopores, exhibits a high amorphousness. At room temperature, the optimized electrolyte membrane offers a good value of ionic conductivity (~1.44 × 10−4 S cm−1), with a wide electrochemical stability window (~4.14 V). Moreover, the electrolyte membrane can sustain a high thermal decomposition temperature (~305 °C), and thus its mechanical performance is sufficient for practical applications. Accordingly, the ionic liquid-incorporated Zn-ion conducting polymer electrolyte could be a potential candidate for Zn-based energy storage applications. [ABSTRACT FROM AUTHOR]

New polymer electrolyte films of lithium tetrafluoroborate (LiBF 4 )-complexed poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) embedded with different quantities of 1-ethyl-3methylimidazolium tetrafluoroborate (EMIMBF 4 ) 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 LiBF 4 salt and EMIMBF 4 ionic liquid. The size and interconnection of pores in the films were enhanced by EMIMBF 4 . Impedance measurements indicated that the room-temperature ionic conductivity of the films increased with increasing EMIMBF 4 concentration until 15 wt.%, being up to 0.202 × 10 −4 S cm −1 , and then decreased with further increasing EMIMBF 4 concentration. In addition, the temperature-dependent ionic conductivity of the polymer electrolyte films followed an Arrhenius relation and the 15 wt.% EMIMBF 4 -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:15LiBF 4 +15 EMIMBF 4 gel polymer electrolyte films was evaluated as approximately 4.4 V, which is a promising value for ion battery applications. [ABSTRACT FROM AUTHOR]

Herein, an environmentally-benign, facile, efficient, low-cost, scalable fabrication process of achieving flexible graphene paper electrode at ambient conditions is reported. By means of high-shear exfoliation of graphite in aqueous polyvinyl alcohol (PVA), the graphene/PVA dispersion is prepared. Various characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, etc.) confirm that the resulting dispersion is with the presence of high-quality, single to few-layered graphene sheets with thickness up to 1.68 nm, lateral size of 0.5–2 μm, and low defect density (I D / I G = 0.09). Further, the applicability of the in-situ exfoliated graphene/PVA dispersion is demonstrated for the fabrication of flexible conductive paper electrodes through a simple intermittent soaking-drying approach. The graphene paper electrode possesses an electrical sheet resistance of 15 Ω sq−1, without any additional annealing treatment and conductive additives. Finally, the graphene paper electrode is integrated with ionic-liquid incorporated PVA polymer electrolyte to develop the all-solid-state supercapacitor. It imparts a considerable specific capacitance of 222.96 F g−1 along with ~60% capacitance retention and ~100% coulombic efficiency after 6000 charge–discharge cycles. Meanwhile, the polymer electrolyte exhibits a remarkable ionic conductivity (4.63 × 10−4 S cm−1) together with a wide electrochemical stability window (5.1 V), favorable for device applications. The unique interwoven nanoporous conductive network of PVA-stabilized exfoliated graphene provides fast diffusion pathways to electrolyte ions, thus significantly enhancing the charge-storage performance. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A sodium-ion conducting poly(vinyl alcohol)-based gel polymer electrolyte membrane is developed by plasticizing with an ionic liquid, for the fabrication of electric double-layer capacitors. Sodium triflate is selected as the sodium salt. 1-Ethyl-3 methylimidazoliumtrifluoromethanesulfonate is employed as the plasticizer. The properties of the electrolyte membranes are analyzed in terms of their crystallinity, morphology, thermal stability, electrochemical stability window, ionic transference number, and ionic conductivity. The composition with poly(vinyl alcohol) - 30% sodium triflate + 10% 1-ethyl-3 methylimidazoliumtrifluoromethanesulfonate shows the optimal performances such as good thermal stability up to 150 °C and wide electrochemical stability window of 4.70 V. It is thus employed in the fabrication of electric double-layer capacitors, serving as both ion-conducting electrolyte and separator. The capacitor shows almost 100% coulombic efficiency and stable charge-discharge cyclic property with almost 100% capacity retention after 1000 cycles, when charging up to 1.6 V and 2.0 V with a specific capacitance of 103.7 and 127.8 F g−1, respectively. It compares well with that made of a liquid electrolyte. This excellent performance is attributed to the sodium triflate with large-sized anions and thus high ionic conductivity (3.8 × 10−3 S cm−1) of the electrolyte membrane. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrolyte membrane can efficiently restrain Zn dendrite growth and HER reaction. • The membrane demonstrates a good flame-retardant performance. • Zn-HS supercapacitor can be operated in a wide temperature range (RT-100 °C). • Supercapacitor exhibits an ultra-long cycling stability over 30,000 cycles at 80 °C. • Flexible supercapacitor offers a high flexible and thermotolerant performance. Hydrogel electrolytes often fail at high temperatures and thus common Zn-ion energy storage devices are rarely employed under high temperature conditions. Herein, a flexible heat-resistant nonflammable polymer electrolyte membrane has been prepared and employed in the fabrication of Zn-ion energy storage devices. The optimum electrolyte membrane exhibits a high room-temperature ionic-conductivity (∼1.52 × 10-3 S cm−1) along with a wide window of electrochemical stability (∼2.5 V). The membrane also shows a high tensile strength (4.3 MPa) and good flame-retardant performance. Moreover, it can effectively restrain the parasitic hydrogen evolution reaction as well as the Zn-dendrite formation. The Zn-ion hybrid supercapacitor (Zn-HS) fabricated with the membrane demonstrates good flexibility and thermotolerant performance. At a current density of 1 A/g, the device possesses a specific capacitance of 162.6 F/g at room temperature, 362.6 F/g at 80 °C, and 404.2 F/g at 100 °C. It also exhibits a long-term cycling capability (up to 30,000 cycles) even at 80 °C. Conclusively, the present work offers a promising way in designing heat-resistant nonflammable polymer electrolytes for flexible energy storage devices suitable for high-temperature applications. [ABSTRACT FROM AUTHOR]

Gel electrolytes currently draw considerable interest for flexible supercapacitors. Conventional hydrogel electrolytes find limited suitability at low/high temperatures as they contain immense water. This hinders their application in supercapacitors under a harsh environment. Herein, a novel gel polymer electrolyte (GPE) membrane based on the PVdF-HFP/EMITf/Al(Tf) 3 system is prepared. The optimized GPE membrane exhibits a high ionic conductivity of ~1.6 × 10−3 S cm−1 at room-temperature with a high value of ~0.8 × 10−3 S cm−1 retained at a freezing temperature of −20 °C. The prepared GPE membrane also offers a wide electrochemical stability window (~5.6–4.2 V) in the temperature range of −20 to 60 °C. The supercapacitor cells designed with GPE membrane and graphene nano-platelet electrode display excellent capacitive performance (323.9 F g−1 at 2 V) and cycling stability (over 50000 cycles) at room-temperature. At −20 °C, the supercapacitor cells still maintain promising capacitive performance and outstanding cycling stability. Moreover, the designed flexible supercapacitors also offer remarkable performance under various bending conditions and maintain low-temperature tolerance. Consequently, it is believed that the low-temperature tolerance GPE membrane based on the PVdF-HFP/EMITf/Al(Tf) 3 system possesses potential applications in flexible supercapacitors under harsh environments. Image 1 • GPE membrane has a high ionic conductivity 0.8 × 10−3 S/cm at −20 °C. • Solid-state supercapacitors display a high specific capacitance 323.9 F/g at 2 V. • The supercapacitors exhibit an ultra-long cycling stability over 50000 cycles. • Flexible supercapacitors offer a high performance in various bending conditions. • Flexible supercapacitors display an excellent anti-freezing performance. [ABSTRACT FROM AUTHOR]