Ionic Liquid-based Polymer Electrolyte Research Articles

Gas-Phase Functionalization of Macroscopic Carbon Nanotube Fiber Assemblies: Reaction Control, Electrochemical Properties, and Use for Flexible Supercapacitors.

The assembly of aligned carbon nanotubes (CNTs) into fibers (CNTFs) is a convenient approach to exploit and apply the unique physico-chemical properties of CNTs in many fields. CNT functionalization has been extensively used for its implementation into composites and devices. However, CNTF functionalization is still in its infancy because of the challenges associated with preservation of CNTF morphology. Here, we report a thorough study of the gas-phase functionalization of CNTF assemblies using ozone which was generated in situ from a UV source. In contrast with liquid-based oxidation methods, this gas-phase approach preserves CNTF morphology, while notably increasing its hydrophilicity. The functionalized material is thoroughly characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy. Its newly acquired hydrophilicity enables CNTF electrochemical characterization in aqueous media, which was not possible for the pristine material. Through comparison of electrochemical measurements in aqueous electrolytes and ionic liquids, we decouple the effects of functionalization on pseudocapacitive reactions and quantum capacitance. The functionalized CNTF assembly is successfully used as an active material and a current collector in all-solid supercapacitor flexible devices with an ionic liquid-based polymer electrolyte.

Ionic Liquid Enhanced Polymer Elcetrolytes for Environmental Friendly Electric Double Layer Capacitors

In this study we perform the preparation and characterization of poly (vinyl alcohol) (PVA)–added ionic liquid based ion conductors. The polymer electrolyte is incorporated with magnesium triflate [Mg(CF3SO3)2 or MgTf] as salt and 1–butyl–3–methylimidazolium bromide (BmImBr) as an environmental friendly ionic liquid. Differential scanning calorimetry (DSC) is carried out to investigate the glass transition temperature (Tg ), which is used to study the plasticizing effect of the ionic liquid. The polymer electrolyte with the lowest Tg gives the highest ionic conductivity value of (1.64±0.01) x 10-3 S cm-1 at 60 wt.% of BmImBr. This is attributed to the plasticizing effect of the ionic liquid, which increases the flexibility of the polymer backbone, hence increasing the ionic mobility and segmental motion of the ions. The highest conducting ionic liquid based polymer electrolyte is used to fabricate electrical double layer capacitors (EDLC). The electrochemical potential window is evaluated using linear sweep voltammetry (LSV). Electrochemical capacitance of the EDLC is evaluated through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). The electrochemical potential window of ionic liquid–added polymer electrolyte is extended from 1.35 V to 2.6 V. Cyclic voltammetry (CV) proves the improvement in specific capacitance of the electrical double layer capacitors (EDLCs) containing ionic liquid–added polymer electrolyte by increasing the specific capacitance from 1.41 Fg-1 in the ionic liquid free polymer electrolyte to 45.95Fg-1 for the 60 wt% ionic liquid added polymer electrolyte. Keywords: Poly(vinyl alcohol); Ionic liquid; Mg(CF3SO3)2 , EDLC; Capacitance

Effect of temperature on electrochemical performance of ionic liquid based polymer electrolyte with Li/LiFePO4 electrodes

Poly ethylene oxide based polymer electrolytes containing salt lithium bis(trifluoromethylsulfonyl)imide and ionic liquid 1-butyl-3-methyl pyridinium bis(trifluoromethylsulfonyl)imide are synthesized. The prepared polymer electrolytes are found to be thermally stable up to 340–360°C. Ionic conductivity is observed ~2.5×10−5Scm−1 at 25°C and 2.3×10−4Scm−1 at 40°C for 30% IL containing polymer electrolyte. Also, ionic transference number>0.99 and cationic transference number ~0.41 with electrochemical window ~5.2V at 25°C is observed for the electrolyte containing 30% IL. The highest Li+ ion conducting polymer electrolyte is further optimised for battery application. The specific discharge capacity of the prepared cell (Li/polymer electrolyte/LiFePO4) is found to be 106mAhg−1 at 25°C and 160mAhg−1 at 40°C up to 25cycles with 0.1C current rate. The increment in discharge capacity at higher temperature may be due to the better electrode-electrolyte contact. Decrement in cell resistance is also observed at higher temperature.

Development of Flexible Energy Storage Device by Using Polymer Electrolyte Based on Ionic Liquid

AbstractA flexible supercapacitor composed of the reduced graphene oxide / acid‐treated single‐wall carbon nanotubes (rGO/ASWCNTs) composite (weight ratio of 1:9) electrode with the polymer based gel electrolyte was fabricated via spray coating technique. The ionic liquid based polymer electrolyte (IL‐b‐PE) was prepared by using polyvinyl alcohol (PVA) and 1‐Butyl‐3‐methylimidazolium tetrafluoroborate (BMIMBF4), which was able to fabricate full device as flexible supercapacitor. The electrochemical performances evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge / discharge (GCD) measurements. The flexible supercapacitor with the ionic liquid based polymer electrolyte (IL‐b‐PE) exhibited enhanced electrochemical performances compared to the flexible supercapacitor with PVA‐H3PO4 gel electrolyte. The electrochemical properties of the flexible supercapacitor assembled by IL‐b‐PE were investigated as a function of bending cycles. The cycling stability of the flexible supercapacitor was analysed as the function of bending test (0∼300) and GCD cycles (0∼4000). The specific capacitance value of the flexible supercapacitor (unbent) was 62.4 F g−1, which decreased to 55.7 F g−1 (89.3% retention after 1000 GCD cycles. The flexible supercapacitor was retained 64.6% (40.3 F g−1) of its initial capacitance value (62.4 F g−1) after 300 bending with application 4000th GCD cycles.

Electrochemical properties of LiMn0.4Fe0.6PO4 with polyimide-based gel polymer electrolyte for high safety and improvement of rate capability

The electrochemical performance of LiMn0.4Fe0.6PO4, prepared by modified mechanical activation, as the cathode active material for lithium batteries was tested with an ionic liquid-based electrolyte using an electrospun polyimide matrix. The ionic liquid electrolyte of 0.5M lithium bis(trifluoromethanesulfonylimide) (LiTFSI) in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) (BMImTFSI) was incorporated in an electrospun polyimide (PI) film to prepare the ionic liquid-based polymer electrolyte (ILPE). This PI-based ILPE exhibited good mechanical strength and high thermal stability. Impedance spectroscopy was applied to investigate the electrolyte/electrode resistance over time. The impedance resistance of a Li/ILPE/Li cell was found to increase over time to 7 days, decreasing thereafter. Impedance experiments further indicated good cycling stability for the cell when tested at room temperature. The cell based on Li/ILPE/LiMn0.4Fe0.6PO4 exhibited an initial discharge capacity of 163.6mAhg−1 at 0.1 C-rate at room temperature. Finally, a high capacity and good cycling performance could be obtained even using the high current density of 2C.

Highly Conductive, Ionic Liquid-Based Polymer Electrolytes

In this manuscript is reported a thermal and impedance spectroscopy investigation carried out on quaternary polymer electrolytes, to be addressed as separators for lithium solid polymer batteries, containing large amount of the N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide ionic liquid. The target is the development of Li+ conducting membranes with enhanced ion transport even below room temperature. Polyethylene oxide and polymethyl methacrylate were selected as the polymeric hosts. A fully dry, solvent-free procedure was followed for the preparation of the polymer electrolytes, which were seen to be self-consistent and handled even upon prolonged storage periods (more than 1 year). Appealing ionic conductivities were observed especially for the PEO electrolytes, i.e., 1.6 × 10−3 and 1.5 × 10−4 S cm−1 were reached at 20 and −20°C, respectively, which are ones the best, if not the best ion conduction, never detected for polymer electrolytes.

Ionic Liquid-Based Polymer Electrolytes via Surfactant-Assisted Polymerization at the Plasma-Liquid Interface.

We first report an innovative method, which we refer to as interfacial liquid plasma polymerization, to chemically cross-link ionic liquids (ILs). By this method, a series of all-solid state, free-standing polymer electrolytes is successfully fabricated where ILs are used as building blocks and ethylene oxide-based surfactants are employed as an assisted-cross-linking agent. The thickness of the films is controlled by the plasma exposure time or the ratio of surfactant to ILs. The chemical structure and properties of the polymer electrolyte are characterized by scanning electron microscopy (SEM), Fourier transformation infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). Importantly, the underlying polymerization mechanism of the cross-linked IL-based polymer electrolyte is studied to show that fluoroborate or halide anions of ILs together with the aid of a small amount of surfactants having ethylene oxide groups are necessary to form cross-linked network structures of the polymer electrolyte. The ionic conductivity of the obtained polymer electrolyte is 2.28 × 10(-3) S·cm(-1), which is a relatively high value for solid polymer electrolytes synthesized at room temperature. This study can serve as a cornerstone for developing all-solid state polymer electrolytes with promising properties for next-generation electrochemical devices.

Performance of solid state supercapacitors based on polymer electrolytes containing different ionic liquids

Abstract Four Ionic Liquid based Polymer Electrolytes (IL-b-PE) were prepared by blending a Polymeric Ionic Liquid, Poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (PILTFSI), with four different ionic liquids: 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) (IL-b-PE1), 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI) (IL-b-PE2), 1-(2-hydroxy ethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HEMimTFSI) (IL-b-PE3), and 1-Butyl-1-methylpyrrolidinium dicyanamide, (PYR14DCA) (IL-b-PE4). Physicochemical properties of IL-b-PE such as ionic conductivity, thermal and electrochemical stability were found to be dependent on the IL properties. For instance, ionic conductivity was significantly higher for IL-b-PE2 and IL-b-PE4 containing IL with small size anions (FSI and DCA) than IL-b-PE1 and IL-b-PE3 bearing IL with bigger anion (TFSI). On the other hand, wider electrochemical stability window (ESW) was found for IL-b-PE1 and IL-b-PE2 having ILs with electrochemically stable pyrrolidinium cation and FSI and TFSI anions. Solid state Supercapacitors (SCs) were assembled with activated carbon electrodes and their electrochemical performance was correlated with the polymer electrolyte properties. Best performance was obtained with SC having IL-b-PE2 that exhibited a good compromise between ionic conductivity and electrochemical window. Specific capacitance (Cam), real energy (Ereal) & real power densities (Preal) as high as 150 F g−1, 36 Wh kg−1 & 1170 W kg−1 were found at operating voltage of 3.5 V.

Ionic liquid enhanced magnesium-based polymer electrolytes for electrical double-layer capacitors

This paper describes the preparation and characterization of poly(vinyl alcohol) (PVA)-added ionic liquid-based ion conductors. The polymer electrolyte is incorporated with magnesium triflate [Mg(CF3SO3)2 or MgTf] as salt and 1-butyl-3-methylimidazolium bromide (BmImBr) as ionic liquid. Differential scanning calorimetry (DSC) is carried out to investigate the glass transition temperature which is used to study the plasticizing effect of the ionic liquid. The highest conducting ionic liquid-based polymer electrolyte is used to fabricate electrical double-layer capacitors (EDLC). The electrochemical potential window is evaluated using linear sweep voltammetry (LSV). The electrochemical capacitance of the EDLC is evaluated through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). The electrochemical potential window of ionic liquid-added polymer electrolyte is extended from 1.35 to 2.6 V. Cyclic voltammetry (CV) proves the improvement in specific capacitance of the electrical double-layer capacitors (EDLCs) containing ionic liquid-added polymer electrolyte.

Isothermal and non-isothermal crystallization kinetics of PVA + ionic liquid [BDMIM][BF4]-based polymeric films

The effect of ionic liquid (IL), 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [BDMIM][BF4], on crystallization behavior of poly(vinyl alcohol) (PVA) has been studied by isothermal and non-isothermal differential scanning calorimetry techniques. The PVA + IL based polymer electrolyte films have been prepared using solution casting technique. To describe the isothermal and non-isothermal crystallization kinetics, several kinetic equations have been employed on PVA + IL based films. There is strong dependence of the peak crystallization temperature (Tc), relative degree of crystallity (Xt), half-time of crystallization (t1/2), crystallization rate constants (Avrami Kt and Tobin AT), and Avrami (n) and Tobin (nT) exponents on the cooling rate and IL loading.

Ionic Liquid based polymer electrolytes for electrochemical sensors

Amperometric NO2 printed sensor with a new type of solid polymer electrolyte and a carbon working electrode has been developed. The electrolytes based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][N(Tf)2], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][CF3SO3] and 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4] ionic liquids were immobilized in poly(vinylidene fluoride) matrix [PVDF]. The analyte, gaseous nitrogen dioxide, was detected by reduction at -500 mV vs. platinum pseudoreference electrode. The sensors showed a linear behavior in the whole tested range, i.e., 0 - 5 ppm and their sensitivities were in order of 0.3 x∙10-6 A/ppm. The sensor sensitivity was influenced by the electric conductivity of printing formulation; the higher the conductivity, the higher the sensor sensitivity. The rise/recovery times were in order of tens of seconds. The use of screen printing technology and platinum pseudoreference electrode simplify the sensor fabrication and it does not have any negative effect on the sensor stability.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7371

100 MeV Si9+ swift heavy ion irradiation induced enhancement in electrochemical properties of electrolyte membrane composites based on ionic liquid-polymer-nanocomposite

In the present study, 100MeV Si9+ swift heavy ion (SHI) irradiation has been used as a tool to enhance the electrochemical properties of ionic liquid based polymer electrolyte nanocomposite membranes and their fluence dependant properties have been investigated. Polyaniline (PAni) nanofibers have been grown inside the interlayer galleries of montmorillonite (MMT) and used as hybrid nanofiller. With increasing fluence interlayer spacing of MMT increases leading to exfoliation of MMT platelets at the fluence of 5×1011ionscm−2 dispersing MMT layers and PAni nanofibers in the polymer matrix as confirmed from HRTEM and XRD studies. DSC results show that the degree of crystallinity decreases with increasing fluence. SEM micrographs reveal that with increasing fluence porosity increases. Contact angle measurements show that SHI irradiation turns the hydrophilic electrolyte membranes to hydrophobic at the fluence of 5×1011ionscm−2. Highest room temperature ionic conductivity of 8.4×10−2Scm−1 has been obtained for the polymer electrolyte nanocomposite membrane irradiated with the highest fluence of 1×1012ionscm−2. Scaling of ac conductivity demonstrates that ion concentration and ion diffusion length change with changing fluence. The nanocomposite electrolyte membranes irradiated with the fluence of 1×1012ionscm−2 are electrochemically stable up to 7.1V.

All-solid state supercapacitors operating at 3.5 V by using ionic liquid based polymer electrolytes

All-solid state supercapacitors (SCs) using Ionic Liquid based Polymer Electrolyte (IL-b-PE) and activated carbon were assembled and characterized electrochemically. IL-b-PE consisted of a binary blend of a polymeric ionic liquid (PIL), poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (pDADMATFSI), and their corresponding ionic liquid (IL), N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR14TFSI) in a ratio of 40:60,w/w respectively. Assembling of supercapacitors simply consists of facing two impregnated electrodes without the need of additional separator. Several all-solid state SCs with impregnation ratios (IL-b-PE mass/active material mass) ranging from 5 to 18 were characterized. An all-solid state SC with impregnation ratio of 7 showed the best performance with specific capacitance (Cam) and real energy (Ereal) of 100 F g−1 and 32 Wh kg−1, respectively. After increasing temperatures to 60 °C, the performance of SCs further improved exhibiting Ereal values of 42 Wh kg−1 at 1 mA cm−2. These figures of merit are only slightly lower than those obtained for convectional SCs using pure PYR14TFS and much higher as compared with other solid SCs based on conventional polymer electrolytes. This is mainly due to the high electrochemical stability of this IL-b-PE that allows these solid SCs to operate at maximum voltages as high as 3.5 V for the first time.

Towards a fully printed electrochemical NO2 sensor on a flexible substrate using ionic liquid based polymer electrolyte

An electrochemical amperometric nitrogen dioxide sensor with solid polymer electrolyte was fabricated by means of screen printing technology on both rigid and flexible substrates. The sensor concept is based on a semi-planar, three-electrode topology that enables low power, high performance, thin, and selective gas sensors to be produced on poly(ethylene terephthalate) (PET) and/or Kapton foil. The sensor response mechanism, i.e. the reduction of nitrogen dioxide at the boundary of a solid polymer electrolyte/working electrode/gas analyte, was predicted by using a Langmuir adsorption isotherm. It was demonstrated that a new platform for the electrochemical NO2 sensor can be completely manufactured by screen printing, which allows the fabrication of a flexible and low cost device suitable for mass production. Further, it was demonstrated that the fully printed sensor can be fabricated without using metal-based printing pastes, which is important from the point of view of the environment. The fully-printed, metal-free electrochemical sensor exhibited a linear response in the range of 0–10ppm, fast response/recovery times (70/60s, respectively), a resolution of 0.2ppm, and a sensitivity of 590nA/ppm, which enables the sensor to be used for both the monitoring of NO2 exposure in the workplace as well as environmental air pollution.

Enhancement in electrochemical properties of ionic liquid-based nanocomposite polymer electrolytes by 100 MeV Si9+ swift heavy ion irradiation

Swift heavy ion (SHI) irradiation has been used as a tool to enhance the electrochemical properties of ionic liquid-based nanocomposite polymer electrolytes dispersed with dedoped polyaniline (PAni) nanorods; 100 MeV Si9+ ions with four different fluences of 5 × 1010, 1 × 1011, 5 × 1011, and 1 × 1012 ions cm−2 have been used as SHI. XRD results depict that with increasing ion fluence, crystallinity decreases due to chain scission up to fluence of 5 × 1011 ions cm−2, and at higher fluence, crystallinity increases due to cross-linking of polymer chains. Ionic conductivity, electrochemical stability, and dielectric properties are enhanced with increasing ion fluence attaining maximum value at the fluence of 5 × 1011 ions cm−2 and subsequently decrease. Optimum ionic conductivity of 1.5 × 10−2 S cm−1 and electrochemical stability up to 6.3 V have been obtained at the fluence of 5 × 1011 ions cm−2. Ac conductivity studies show that ion conduction takes place through hopping of ions from one coordination site to the other. On SHI irradiation, amorphicity of the polymer matrix increases resulting in increased segmental motion which facilitates ion hopping leading to an increase in ionic conductivity. Thermogravimetric analysis (TGA) measurements show that SHI-irradiated nanocomposite polymer electrolytes are thermally stable up to 240–260 °C.

Preparation and characterization of low environmental humidity sensitive ionic liquid polymer electrolytes

ABSTRACTMethyl 3‐(3‐(2‐hydroxyethyl)imidazole‐1‐yl)propanoate chloride salt (IL‐Cl), methyl 3‐(3‐(2‐hydroxyethyl)imidazole‐1‐yl)propanoate bromate salt (IL‐Br), and their derivatives modified by polyethylene glycol (PEG) through ester‐exchange reaction (IL‐PEGs) were synthesized. First, the properties of those materials, especially their conductivity, have been extensively studied. Second, using the IL‐PEG with the highest conductivity as a plasticizer and electrolyte, a series of gel polymer electrolytes were successfully fabricated from polyurethane, poly‐1,4‐butylene adipate glycol 2000, and IL‐PEGs by melting blends with different mass ratios in a Haake torque rheometer. The surface morphology, thermal properties, and the surface resistivity of gel polymer electrolytes were studied by scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and surface resistivity test, respectively. Scanning electron microscopy pictures showed that the surface of polymer electrolyte is smoother than that without added IL‐PEGs. Thermogravimetric analysis results revealed that the polymer electrolytes will not decompose when the processing temperature is below 275°C. It was found that the surface resistivity of polymer electrolytes can be below 109 Ω, showing a good antistatic property, and it changes slightly as the relative humidity decreases from 40% to 0.1%, indicting that the material has low humidity sensitivity. This study is a new demonstration and development in ionic liquid based polymer electrolyte. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40675.

Scaling of AC conductivity, electrochemical and thermal properties of ionic liquid based polymer nanocomposite electrolytes

In the present study, polyaniline nanofibers have been grown inside the interlayer galleries of montmorillonite clay to form effective hybrid nanofillers. The effect of nanofillers on the properties of ionic liquid based polymer electrolytes has been investigated by varying the nanofiller concentration systematically. The dispersion of the hybrid nanofillers effectively enhances the ionic conductivity, electrochemical stability and the thermal stability. Scaling of AC conductivity shows that ion concentration and ion diffusion length change with changing nanofiller concentration. The dispersion of nanofillers increases free volume of the electrolyte to facilitate the ion hopping that result in increased ionic conductivity. Highest room temperature ionic conductivity of 7.7×10−3 S cm−1 is achieved at 7.5wt. % of the nanofiller content. Electrochemical stability increases with increase in nanofiller concentration attaining a maximum value of 5.8V at 7.5wt. % of nanofillers concentration. The thermal stability is enhanced on the addition of nanofillers as they act as heat and mass transport barrier for volatile species.

Ionic liquid based polymer electrolyte dispersed with dedoped polyaniline nanorods

Abstract Studies on a novel nanocomposite polymer electrolyte based on ionic liquid 1-butyl-3-methylimidazolium bromide incorporated with dedoped polyaniline (PAni) nanorods as a filler has been reported. The effect of different concentrations of dedoped PAni nanorods on the properties of nanocomposite electrolytes has been studied for applications in rechargeable batteries. XRD and FTIR studies show that substantial conformational changes take place in the incorporation of dedoped PAni nanorods which increases the amorphicity for up to 5 wt.% of nanorod content. Room temperature ionic conductivity also increases with increasing nanorod content and becomes maximum at a value of 2.3 × 10 − 3 S cm − 1 at 5 wt.% of nanorod content. Beyond 5 wt.%, phase separation takes place as evident from XRD and SEM studies and the conductivity decreases. Studies on AC electrical response show that the conductivity mechanism follows jump relaxation model. The nanocomposite electrolyte with 5 wt.% of dedoped PAni nanorods offers electrochemical stability of 5.3 V which is adequate for practical applications. The electrolyte system is thermally stable for up to 260 °C showing practical applicability.

Study of Ion Diffusional Motion in Ionic Liquid-Based Polymer Electrolytes by Simultaneous Solid State NMR and DTA

Polymer electrolytes containing ionic liquid (IL), 2-methyl-1,3-dipropylimidazolium dihydrogenphosphate (MDPImH2PO4) have been studied by (1)H solid state NMR and differential thermal analysis (DTA) simultaneously by using a specially designed probe. To the best of our knowledge, this is the first report of its kind for IL based polymer electrolytes. The variation of NMR line width with temperature for the IL and polymer electrolytes shows line narrowing at the glass transition and melting temperature. The onset of long-range ion diffusional motion also takes place at these temperatures and is accompanied by a sudden increase in ionic conductivity value by 2-3 orders of magnitude. The presence of amorphous and crystalline phases in IL-based polymer electrolytes has been observed from X-ray diffraction (XRD) studies, and the amorphous phase is the high conducting phase in these polymer electrolytes. The IL-based polymer electrolytes have been observed to be thermally stable up to 200 °C. The results obtained from ion transport studies have also been supported by Fourier transform infrared (FTIR), XRD, and cyclic voltammetry (CV) studies.

Characterization of N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide-based polymer electrolytes for high safety lithium batteries

Poly(vinylidene difluoride-co-hexafluoropropylene) (PVdF-HFP) membrane was prepared by electrospinning. The membranes served as host matrices for the preparation of ionic liquid-based polymer electrolytes (ILPEs) by activation with non-volatile, highly thermally stable, and safe room temperature ionic liquid (RTIL) electrolytes; N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Py14TFSI) complexed with 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). In this work, the first combination of electrospun PVdF-HFP fiber polymer host and pyrrolidinium-based ionic electrolyte was employed for highly stable lithium batteries. The ILPE exhibited low Li+–TFSI coordination, low crystallinity, high thermal stability, high electrochemical stability, and high ionic conductivity with a maximum of 1.1 × 10−4 S cm−1 at 0 °C. The ILPE exhibited good compatibility with a LiFePO4 electrode on storage and good charge–discharge performance in Li/ILPE/LiFePO4 cells at room temperature, delivering specific capacities of 143 and 115 mA h g−1 at 0.1 and 1 C-rates. The ILPE also exhibited stable cycle properties and have therefore been demonstrated to be suitable for lithium battery applications.