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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]

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]

With 1-methyl-2-pyrrolidinone (NMP) as the solvent, the biodegradable gel polymer electrolyte films are prepared based on poly(vinyl alcohol) (PVA), lithium bis(trifluoromethane)sulfonimide (LiTFSI), and 1-ethyl-3 methylimidazoliumbis(trifluoromethylsulfonyl)imide (EMITFSI) by means of solution casting. The films are characterized to evaluate their structural and electrochemical performance. The 60PVA-40LiTFSI + 10 wt.% EMITFSI system exhibits excellent mechanical properties and a high ionic transference number (0.995), indicating primary ionic conduction in the film. In addition, because of the flexibility of polymer chain segments, its relaxation time is as low as 5.30 × 10−7 s. Accordingly, a high ionic conductivity (3.6 × 10−3 S cm−1) and a wide electrochemical stability window (~5 V) are obtained. The electric double-layer capacitor (EDLC) based on this electrolyte system shows a specific capacitance of 101 F g−1 and an energy density of 10.3 W h kg−1, even after 1000 charge-discharge cycles at a current density of 0.4 A g−1 under a charging voltage of 2 V. All these excellent properties imply that the NMP-soluble 60PVA-40LiTFSI + 10 wt.% EMITFSI gel polymer electrolyte could be a promising electrolyte candidate for electrochemical device applications. [ABSTRACT FROM AUTHOR]

Polymeric ionic liquid-based gel electrolyte films are a new generation of electrolyte materials for flexible energy storage device applications. In this work, Li-ion conducting gel electrolyte films are prepared with the polymeric ionic liquid poly(diallydimethylammonium) bis(trifluoromethane sulfonyl)imide (poly(DADMATFSI)) as the host polymer and the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt as the dopant. The crystalline nature, thermal stability, ionic conductivity and electrochemical stability window of the polymeric electrolyte films are analyzed by various characterization techniques. It is found that the polymeric electrolyte films exhibit high flexibility and excellent thermal stability. Their room-temperature electrical conductivity increases with increasing LiTFSI concentration and reaches a high value of 1.00 × 10 −3 S cm −1 at 20 wt% LiTFSI. The ionic transference numbers of the polymeric electrolyte films are in the range of 0.98–0.99, indicating that they are perfect ion conductors. Finally, the electrochemical stability window of the 20 wt% LiTFSI-doped polymeric electrolyte film is determined as approximately 6 V, which is a promising value for flexible energy storage device 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]

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]

The highly stretchable pure poly(vinyl alcohol) (PVA) membranes with high amorphicity and large ductility are prepared based on an N-methylpyrrolidone (NMP) solution. Meanwhile, the PVA based gel electrolyte membranes doped with magnesium trifluoromethanesulfonate (Mg(Tf) 2 ) and plasticized with 1-ethyl-3-methylimidazoliumtrifluoromethanesulfonate (EMITf) are fabricated with the NMP as the solvent. For the plasticized membranes, the 60PVA-40Mg(Tf) 2 + 10EMITf electrolyte system exhibits the highest room-temperature ionic conductivity (1.2 ×10 −3 S cm −1 ), excellent thermal performance and satisfying strength and flexibility. This system is applied for the fabrication of electric double-layer capacitors (EDLCs), acting as both separator and electrolyte. The EDLC shows a specific capacitance of 118 F g −1 with an excellent stability and almost 100% coulombic efficiency over 1000 charge-discharge cycles when charging at 0.85 V under a current density of 313 mA g −1 . When the charging voltage is increased to 2 V, the stability of the EDLC somewhat decreases but the coulombic efficiency is still near 100%. Additionally, the CV curves exhibit symmetrical and ideal rectangular shapes without the presence of redox peaks at low scan rates even for 1000 cycles. Consequently, this polymer electrolyte system should be an excellent candidate for ion device 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]