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Solid‐state‐batteries employing lithium metal anodes promise high theoretical energy and power densities. However, morphological instability occurring at the lithium/solid–electrolyte interface when stripping and plating lithium during cell cycling needs to be mitigated. Vacancy diffusion in lithium metal is not sufficiently fast to prevent pore formation at the interface above a certain current density during stripping. Applied pressure of several MPa can prevent pore formation, but this is not conducive to practical application. This work investigates the concept of ionic liquids as "self‐adjusting" interlayers to compensate morphological changes of the lithium anode while avoiding the use of external pressure. A clear improvement of the lithium dissolution process is observed as it is possible to continuously strip more than 70 μm lithium (i. e., 15 mAh cm−2 charge) without the need for external pressure during assembly and electrochemical testing of the system. The impedance of the investigated electrodes is analyzed in detail, and contributions of the different interfaces are evaluated. The conclusions are corroborated with morphology studies using cryo‐FIB‐SEM and chemical analysis using XPS. This improves the understanding of the impedance response and lithium stripping in electrodes employing liquid interlayers, acting as a stepping‐stone for future optimization. [ABSTRACT FROM AUTHOR]

In search of energy storage solutions, polymer electrolytes are particularly interesting, owing to their high intrinsic safety. We show for the first time a lithium metal polymer battery working with a polymer electrolyte based on poly(lactic acid), exhibiting a remarkably low charge-transfer resistance. This polymer is produced from lactic acid, which can be obtained from waste and renewable sources. Thus, a significant fraction of fossil-based raw materials could be eliminated from the production of battery components. By incorporation of the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethane-sulfonyl) imide (Pyr14TFSI), fully amorphous, solvent-free, very low-volatile solid polymer electrolytes (SPEs) are obtained, which are shown to be thermally and electrochemically stable electrolytes in lithium metal polymer batteries. A lithium metal polymer battery with a composite lithium iron phosphate (LFP) cathode was successfully cycled with this electrolyte, showing its potential for applications. We conclude that alternatives to the benchmark poly(ethylene oxide), like ionic liquid plasticized polyester, are worthy of attention because of the low charge-transfer resistance with lithium metal. [ABSTRACT FROM AUTHOR]

As existing battery technologies struggle to meet the requirements for widespread use in the field of large-scale energy storage, novel concepts are urgently needed concerning batteries that have high energy densities, low costs, and high levels of safety. Here, a novel eco-friendly energy storage system (ESS) using seawater and an ionic liquid is proposed for the first time; this represents an intermediate system between a battery and a fuel cell, and is accordingly referred to as a hybrid rechargeable cell. Compared to conventional organic electrolytes, the ionic liquid electrolyte significantly enhances the cycle performance of the seawater hybrid rechargeable system, acting as a very stable interface layer between the Sn-C (Na storage) anode and the NASICON (Na3Zr2Si2PO12) ceramic solid electrolyte, making this system extremely promising for cost-efficient and environmentally friendly large-scale energy storage. [ABSTRACT FROM AUTHOR]

The Front Cover picture shows the novel sodium/seawater rechargeable energy storage system, which can be considered as a hybrid between a battery and a fuel cell. The system comprises a positive seawater electrode (open to air) and a sealed negative tin‐carbon (Sn–C) composite electrode in contact with environmental‐friendly, highly stabile ionic liquid‐based anolyte. The anode compartment is separated from the cathode compartment by the NASICON solid electrolyte. Upon electrochemical discharge, Na+ ions that are released from the Sn–C anode migrate through the anolyte and the solid electrolyte to reach the cathode compartment where they form sodium hydroxide with the reduction product of water and oxygen (from seawater). More details can be found in the Full Paper by Kim et al. on page 42 in Issue 1, 2016 (DOI: 10.1002/cssc.201501328). [ABSTRACT FROM AUTHOR]

Abstract: In this work is described an innovative synthesis route for hydrophobic ionic liquids (ILs) composed of N-methyl-N-alkylpyrrolidinium (or piperidinium) or imidazolium or tetralkylammonium cations and (perfluoroalkylsulfonyl)imide, ((C n F2n+1SO2)(C m F2m+1SO2)N−), anions. This synthesis does not require the use of any environmental unfriendly solvent such as acetone, acetonitrile or halogen-containing compounds, which is not welcome in industrial applications. Only water is used as the process solvent throughout the entire process. In addition, the commonly used iodine-containing reagents were replaced by the cheaper, more chemically stable and less toxic bromine-containing compounds. A particular care was devoted to the development of the purification route, which is especially important for ILs to be used in high-energy electrochemical devices such as high voltage supercapacitors and lithium batteries. The effect of the reaction temperature, the time and the stoichiometry in the various steps of the synthesis have been investigated in detail. This novel procedure allowed obtaining ultrapure (>99.9wt.%), clear, colourless, inodorous ILs with an overall yield above 92wt.% and moisture content below 1ppm. NMR measurements were run to confirm the chemical structure whereas elemental analysis and electrochemical tests were performed to check the purity of the synthesized ILs. [Copyright &y& Elsevier]

Polymer electrolytes – solid polymeric membranes with dissolved salts – are being intensively studied for use in all-solid-state lithium-metal-polymer (LMP) batteries to power consumer electronic devices. The low ionic conductivity at room temperature of existing polymer electrolytes, however, has seriously hindered the development of such batteries for many applications. The incorporation of salts molten at room temperature (room temperature ionic liquids or RTILs) into polymer electrolytes may be the necessary solution to overcoming the inherent ionic conductivity limitations of ‘dry’ polymer electrolytes. [Copyright &y& Elsevier]

Abstract In this work, we report novel room temperature ionic liquid (RTIL)-based electrolytes to be used with high-energy cathode, lithium-rich nickel manganese cobalt oxide (Li[Li 0.2 Mn 0.56 Ni 0.16 Co 0.08 ]O 2 , LiR-NMC) in Li-ion batteries. The physical and electrochemical characteristics of the newly developed materials are thoroughly detailed, also by means of post-cycling electrochemical impedance spectroscopy (EIS) analysis of the resulting lab-scale lithium cells upon long-term, constant-current cycling (>1200 cycles). In addition, an innovative polymer electrolyte is developed encompassing the best performing RTIL-based electrolyte mixture, which is investigated in terms of its physico-chemical features, ion transport and electrochemical behaviour by EIS, cyclic voltammetry and constant-current (galvanostatic) cycling. The polymer electrolyte is obtained via facile, rapid and easily up-scalable UV-induced free radical polymerization (UV curing) technique, being a low-cost and solvent-free approach compared to other existing film formation techniques. The versatile fabrication method along with the use of appropriate materials may turn high-voltage, solid state and ageing resistant batteries into industrial reality in the coming years, as underlined by the excellent electrochemical response of the lithium polymer cell. Highlights • Novel RTIL-based electrolytes for Li-rich nickel manganese cobalt oxide. • Very high ionic conductivity and wide electrochemical stability. • Stable cycling in Li/LiR-NMC cells at 45 °C for > 1200 cycles. • Simple, cheap thermal polymerization approach for Li polymer batteries. • Innovative RTIL-based green polymer electrolytes with safe characteristics. [ABSTRACT FROM AUTHOR]

A cross-linked polymer membrane formed by poly(ethylene oxide) (PEO), N -methoxyethyl- N -methylpyrrolidium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (Pyr 12O1 FTFSI) ionic liquid and LiFTFSI salt is proposed as the electrolyte for lithium-metal batteries. The ternary membrane has a PEO:Pyr 12O1 FTFSI:LiFTFSI composition of 20:6:4 by mole, which ensures thermal stability up to 220 °C, overall ionic conductivity of 10 − 3 S cm − 1 at 40 °C and suitable Li + transport properties. Combined with the LiFePO 4 composite electrode, whose pores are filled with the Pyr 12O1 FTFSI:LiFTFSI electrolyte, and Li-metal anode, it yields Li/LiFePO 4 cells delivering at 40 °C stable capacity (150 mAh g − 1 or 0.7 mAh cm − 2 ) with coulombic efficiency higher than 99.5%. Impedance spectroscopy measurements reveal low resistance of the electrode/electrolyte interface at both the anode and the cathode. Preliminary results at 20 °C indicates a capacity of 130 mAh g − 1 at C/10 rate (17 mA g − 1 ) with coulombic efficiency higher than 99.5%, thereby suggesting PEO:Pyr 12O1 FTFSI:LiFTFSI as suitable electrolyte for lithium-metal polymer batteries for stationary storage applications, coupled for example with PV and wind generation. [ABSTRACT FROM AUTHOR]

A new ionic liquid formed by coupling 4,5-dicyano-2-(trifluoromethyl)imidazole (TDI − ) anion with N- butyl -N- methyl-pyrrolidinium (Pyr 14 + ) cation is successfully synthesized and characterized by Raman spectroscopy, thermal and rheological analyses, as well as electrochemical techniques. The Pyr 14 TDI-LiTDI mixture, melting at 49 °C, shows remarkable stability within the 50–250 °C range, as well as suitable ionic conductivity, lithium ion transport, and electrochemical stability window. Thus, it is proposed for application at 60 °C in a lithium cell with stable LiFePO 4 cathode. At this temperature, the electrolyte has viscosity of 65.8 mPa s, ionic conductivity of the order of 5 mS cm −1 , and limiting current density of 10 −2 mA cm −2 . Lithium metal/LiFePO 4 cells with such an electrolyte offer promising results in terms of stable LiFePO 4 /electrolyte interface, investigated by impedance spectroscopy, as well as delivered capacity above 160 mAh g −1 with 81% of retention after 80 galvanostatic cycles. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of a superporous activated carbon (named as ANK3) with a tailored porosity (high apparent specific surface area and a high volume of micropores with an average pore size of around 1.4 nm) is analysed in different non-aqueous electrolytes. ANK3 shows very high capacitance (higher than 160 F g −1 ) values in solvent-free electrolytes at different temperatures (20, 40 and 60 °C) as well as in 1 M Et 4 N BF 4 /PC, 1 M PYR 14 BF 4 /PC and 1 M PYR 14 TFSI/PC. The tailored porosity of the ANK3, makes possible to obtain very high capacitance values, making this superporous activated carbon a promising candidate to be used as electrode for electrochemical capacitors using both organic and ionic liquid electrolytes. It is also confirmed that several parameters, such as the ion/pore size ratio, the ion shape, the ion solvation and the conductivity and viscosity of the electrolyte have a strong influence on the electrochemical behaviour of the ANK3. [ABSTRACT FROM AUTHOR]

The development of high voltage electrolytes is one of the key aspects for increasing both energy and power density of electrochemical double layer capacitors (EDLCs). The usage of blends of ionic liquids and organic solvents has been considered as a feasible strategy since these electrolytes combine high usable voltages and good transport properties at the same time. In this work, the ionic liquid 1-butyl-1-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl}imide ([Pyrr 14 ][TFSI]) was mixed with two nitrile-based organic solvents, namely butyronitrile and adiponitrile, and the resulting blends were investigated regarding their usage in electrochemical double layer capacitors. Both blends have a high electrochemical stability, which was confirmed by prolonged float tests at 3.2 V, as well as, good transport properties. In fact, the butyronitrile blend reaches a conductivity of 17.14 mS·cm −1 and a viscosity of 2.46 mPa·s at 20 °C, which is better than the state-of-the-art electrolyte (1 mol·dm −3 of tetraethylammonium tetrafluoroborate in propylene carbonate). [ABSTRACT FROM AUTHOR]

In an attempt to realize sodium-ion batteries with enhanced safety, we report herein the utilization of ionic liquid (IL)-based electrolytes for cycling nanoparticulate anatase TiO 2 as sodium-ion anode material. The use of the IL-based electrolyte results in the highly stable cycling performance of anatase TiO 2 -based electrodes, providing an initial specific capacity of 159 mAh g −1 when applying a specific current of 33.5 mA g −1 , and still 155 mAh g −1 after 80 full (dis-)charge cycles. Moreover, a very promising rate performance is obtained with specific capacities of 108 and 78 mAh g −1 for specific currents of 335 and 670 mA g −1 , respectively. Indeed, the excellent electrochemical performance, and high coulombic efficiency, as well as the electrochemical impedance spectroscopy results indicate the highly beneficial impact of the IL-based electrolyte on the formation of a stabilized solid electrolyte interphase (SEI). [ABSTRACT FROM AUTHOR]

Li metal polymer batteries incorporating crosslinked ternary PEO/PYR 14 TFSI/LiTFSI solid polymer electrolyte (SPE) have been prepared, using V 2 O 5 as active cathode material. As a result of the optimization of the SPE as well as the cell assembly and cycling conditions, V 2 O 5 lithium metal polymer batteries allow reaching 796 Wh kg −1 (of V 2 O 5 ) at C/10 at 40 °C and maintaining 663 Wh kg −1 after 200 cycles at 40 °C. This is higher than the theoretical specific energy of LiCoO 2 vs. Li of 609 Wh kg −1 . Cycling at 80 °C allows reaching 270 mAh g −1 at C/2 and 210 mAh g −1 at 1 C, while at 20 °C it is still possible to reach a discharge capacity of almost 100 mAh g −1 at low rates. Post-cycling SEM and EDX imaging showed that, after 200 cycles at 40 °C, if the plating of Li is not fully homogeneous, no sign of dendrite growth nor obvious vanadium dissolution and redeposition on the anode side occurred. [ABSTRACT FROM AUTHOR]

The chemical–physical properties of a ternary solid polymer electrolyte (SPE) system consisting of poly(ethylene oxide) and two salts, namely lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and the ionic liquid N-methyl-N-butyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI), are reported in this work. The ternary phase diagram shows the composition limits of the thermodynamically stabilized amorphous phase where the polymer electrolyte achieved the maximum conductivity. The important conductivity threshold of 10−3 Scm−1 at 40°C is exceeded for these compositions. Two reasons for the high conductivity are identified; the decreased overall coordination to the Li+-ion and a T g as low as −67°C. Also presented is the thermal stability characterization of such polymer electrolytes. The amorphous phase seems to be thermodynamically unfavored; however, the recrystallization process is slow. [ABSTRACT FROM AUTHOR]

Abstract: 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide (VEIMTFSI) monomer was polymerized by dispersion polymerization in water in presence of an imidazolium-based ionic liquid crosslinker, leading to crosslinked polymeric ionic liquid nanoparticles. These nanoparticles were used as nanolatex binder to process Li-ion battery electrodes. Graphite electrodes were tested in half-cells vs lithium and showed excellent cycling performance for more than 7 months, although the irreversible capacity remained high in the initial cycles as compared with commercial electrodes. Sub-micrometric particles of ca. 200–300 nm of both carbon coated LiFePO4 (LFP) and Li4Ti5O12 (LTO) were also processed, leading to high coulombic efficiencies, although only the LTO electrodes allowed very stable cycling as well as practical performances. [Copyright &y& Elsevier]

Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI) (1:9 in molar ratio) is successfully tested as electrolyte for the high voltage LiMO2–Li2MnO3 (cathode)/lithium (anode) cells at elevated temperature (40 °C). Compared to conventional electrolytes, such as 1 M LiPF6 solution in the mixed solvent of ethylene and dimethyl carbonate (EC:DMC = 1:1), the use of PYR14FSI–LiTFSI electrolyte results in a net improvement of LiMO2–Li2MnO3 cycling stability while granting comparable initial capacity. In addition, the ionic conductivity of the ionic liquid-based electrolyte at 40 °C is high enough to sustain the excellent rate capability of this cathode material. Li/LiMO2–Li2MnO3 cells delivered initial capacity exceeding 200 mA h g−1 at high current rate (2 C) while retaining 94% of the initial capacity after 100 cycles. Differential capacity versus potential analysis and post-mortem characterization by scanning electron microscope, X-ray diffraction and were carried out to explain the improved performance of LiMO2–Li2MnO3 in the IL-based electrolyte. [ABSTRACT FROM AUTHOR]

Abstract: Four room-temperature ionic liquids (RTILs) based on N-methyl-N-methoxyethylpyrrolidinium (PYR12O1 +) and fluorinated sulfonylimides, bis(fluorosulfonyl)imide (FSI−), bis(trifluoromethanesulfonyl)imide (TFSI−), bis(pentafluoroethylsulfonyl)imide (BETI−) and (trifluoromethanesulfonyl) (nonafluorobutanesulfonyl)imide (IM14 −) anion have been synthesised and intensively investigated from an electrochemical and physico-chemical point of view, including thermal behaviour, viscosity, conductivity and electrochemical stability. The prepared ionic liquids are thermally stable (over 200°C in N2 and over 180°C in O2 atmosphere) and electrochemically stable with electrochemical stability windows on platinum in the range from 4.7V (PYR12O1FSI) to 5.4V (PYR12O1IM14). Conductivity decreases in the series FSI-TFSI-BETI-IM14 according to the viscosity increase. DSC measurements showed no crystallisation down to −150°C for PYR12O1TFSI and PYR12O1IM14. [Copyright &y& Elsevier]

Abstract: An advanced electrochemical characterization of cross-linked ternary solid polymer electrolytes (SPEs), prepared by a solvent-free hot-pressing process, is reported. Ionic conductivity, electrochemical stability window and limiting current measurements were performed as a function of the temperature by using both potentiodynamic and galvanostatic techniques. Additionally, the lithium cycleability was evaluated with respect to its dependence on both the operating temperature and the current density by using a new multi-rate Li-stripping-plating procedure. The results clearly indicate the beneficial effect of higher operating temperatures on the rate-capability, without major degradation of the electrochemical stability of the SPE. All-solid-state lithium metal polymer batteries (LMPBs), comprising a lithium metal anode, the cross-linked ternary solid polymer electrolyte and a LiFePO4 composite cathode, were manufactured and investigated in terms of the interdependencies of the delivered capacity, operating temperature and discharge rate. The results prove quite exceptional delivered capacities both at medium current densities at ambient temperatures and even more impressive capacities above 160mAhg−1 at high discharge rates (1C) and temperatures above 60°C. [Copyright &y& Elsevier]

Abstract: Different compositions of a ternary solid polymer electrolyte (SPE) system consisting solely of poly(ethylene oxide), lithium bis(trifluoromethansulfonyl)imide (LiTFSI) and the ionic liquid N-methyl-N-butyl-pyrrolidinium bis(trifluoromethane-sulfonyl) imide (Pyr14TFSI) were tested. Differential scanning calorimetry shows that a few ternary polymer electrolytes with selected salt and ionic liquid contents are amorphous at room temperature. The Li+ coordination in the ternary electrolytes was analyzed by Raman spectroscopy while the Li+ transport properties were investigated by means of pulsed-field-gradient NMR (PFG-NMR), impedance spectroscopy and DC methods. [Copyright &y& Elsevier]

Abstract: Solutions of LiTFSI in organic solvents such as carbonates, do not display the ability to prevent the aluminum corrosion and for this reason cannot be conveniently used as electrolytes in LIBs. However, addition of PYR14TFSI to PC–LiTFSI strongly suppresses the aluminum corrosion process, both at 20 °C and 60 °C. At 60 °C, in a mixture PC–PYR14TFSI–LiTFSI containing 50% of IL, the charge involved in the corrosion process is one order of magnitude lower than that observed in PC–LiTFSI. The suppression of the corrosion process by PYR14TFSI might be related to the reduced solubility of Al(TFSI)3 in PYR14TFSI compared to PC. Al(TFSI)3 is formed on the Al surface in electrolytes containing LiTFSI, and the low solubility of this compound in PYR14TFSI contributes to the formation of a stable protective layer on the Al surface, which in turn reduces the corrosion process. Thanks to their ability to suppress the Al corrosion, PC–PYR14TFSI–LiTFSI mixtures can be conveniently used as electrolytes in LIBs, both at room temperature and 60 °C. [Copyright &y& Elsevier]

Abstract: In this paper we report the results about the use of ternary room temperature ionic liquid–lithium salt mixtures as electrolytes for lithium-ion battery systems. Mixtures of N-methyl-N-propyl pyrrolidinium bis(fluorosulfonyl) imide, PYR13FSI, and N-butyl-N-methylpyrrolidinium bis(trifluoromethansulfonyl) imide, PYR14TFSI, with lithium hexafluorophosphate, LiPF6 and lithium bis(trifluoromethansulfonyl) imide, LiTFSI, containing 5wt.% of vinylene carbonate (VC) as additive, have been used in combination with a commercial graphite, KS6 TIMCAL. The performance of the graphite electrodes has been considered in term of specific capacity, cycling efficiency and cycling stability. The results clearly show the advantage of the use of ternary mixtures on the performance of the graphite electrode. [Copyright &y& Elsevier]

Abstract: In this paper we report the results of chemical-physical investigation performed on ternary room temperature ionic liquid–lithium salt mixtures as electrolytes for lithium-ion battery systems. The ternary electrolytes were made by mixing N-methyl-N-propyl pyrrolidinium bis(fluorosulfonyl) imide (PYR13FSI) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR14TFSI) ionic liquids with lithium hexafluorophosphate (LiPF6) or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The mixtures were developed based on preliminary results on the cyclability of graphite electrodes in the IL-LiX binary electrolytes. The results clearly show the beneficial synergic effect of the two ionic liquids on the electrochemical properties of the mixtures. [Copyright &y& Elsevier]

Abstract: The effect of the alkyl side group on the synthesis and the electrochemical properties of N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR1ATFSI) ionic liquids (ILs) is reported. The investigation was focused on the PYR1ATFSI ionic liquid family because of the interesting electrochemical properties of the members with propyl and butyl side chains. Side alkyl groups (A=C n H2n+1 with n ranging from 1 to 10) of different length and structure were used for the synthesis of PYR1ATFSI materials. NMR and DSC have shown that the ionic liquids were correctly synthesized with the exception of the compounds with tertiary side chains. Most of the materials exhibited a conductivity higher than 10−3 Scm−1 already at 12°C. In the molten state a moderate conductivity decrease was observed with increasing the length and the branching of the side chain (C2H2n+1) group according with the change of viscosity of the ionic liquids. Most of the PYR1ATFSI samples exhibited an electrochemical stability window exceeding 5V. [Copyright &y& Elsevier]

Abstract: Although research in the field of ionic liquids for electrochemical applications has led to a deeper knowledge in their electrochemical properties, doubts in the interpretation of the experimental results are still encountered in the literature due to the poor control of the experimental conditions and/or to the limited number of experiments conducted. In this work, the effect of water and oxygen traces on the cathodic stability window of hydrophobic, air-stable ionic liquids composed of N-alkyl-N-methylpyrrolidinium (PYR1A +) cations and bis(trifluoromethanesulfonyl)imide (TFSI−) anion, is reported. The extensive investigation performed by linear sweep voltammetry (LSV) and cyclic voltammetry (CV) indicates that the TFSI− anion is cathodically stable if the ionic liquid is pure and dry. The N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquids investigated showed featureless cathodic linear sweep voltammetry curves before the massive cation decomposition took place at very low potentials. [Copyright &y& Elsevier]

Abstract: A new ternary polymer electrolyte based on thermally cross-linked poly(urethane acrylate) (PUA), lithium bis(trifluoromethansulfonyl)imide (LiTFSI) and the ionic liquid N-butyl-N-methylpyrrolidinium TFSI (PYR14TFSI) was developed and tested for application in LMP batteries. The polymer electrolyte was a transparent yellow self-standing material with quite good mechanical properties, i.e., comparable to that of a flexible rubber. The room temperature ionic conductivity of the dry polymer electrolyte was found to be as high as 0.1mScm−1 for the compound containing 40wt% of ionic liquid (PYR14TFSI) and a O/Li ratio of 15/1 (Li+ from LiTFSI). The thermal analysis of the new cross-linked electrolyte showed that it was homogeneous, amorphous and stable over a wide temperature range extending from −40°C to 100°C. The homogeneity of the polymer electrolyte was also confirmed by SEM analysis. [Copyright &y& Elsevier]

Abstract: The electrical properties of solvent-free, PEO–LiTFSI solid polymer electrolytes (SPEs), incorporating different N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, PYR1ATFSI, ionic liquids (ILs), are reported. For this purpose, PYR1ATFSI materials containing side alkyl groups with different chain-length and branching, i.e., n-propyl, sec-propyl, n-butyl, iso-butyl, sec-butyl and n-pentyl, were properly synthesized and homogeneously incorporated into the SPE samples without phase separation. The addition of ILs to PEO–LiTFSI electrolytes results in a large increase of the conductivity and in a decrease of the interfacial resistance with the lithium metal anode. Most of the PEO–LiTFSI–PYR1ATFSI samples showed similar ionic conductivities (>10−4 Scm−1 at 20°C) and stable interfacial resistance values (400Ωcm2 at 40°C and 3000Ωcm2 at 20°C) upon several months of storage. Preliminary battery tests have shown that Li/P(EO)10LiTFSI+0.96PYR1ATFSI/LiFePO4 solid-state cells are capable to deliver a capacity of 125mAhg−1 and 100mAhg−1 at 30°C and 25°C, respectively. [Copyright &y& Elsevier]

Abstract: The cycle behaviour and rate performance of solid-state Li/LiFePO4 polymer electrolyte batteries incorporating the N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13TFSI) room temperature ionic liquid (IL) into the P(EO)20LiTFSI electrolyte and the cathode have been investigated at 40°C. The ionic conductivity of the P(EO)20LiTFSI+PYR13TFSI polymer electrolyte was about 6×10−4 Scm−1 at 40°C for a PYR13 +/Li+ mole ratio of 1.73. Li/LiFePO4 batteries retained about 86% of their initial discharge capacity (127mAhg−1) after 240 continuous cycles and showed excellent reversible cyclability with a capacity fade lower than 0.06% per cycle over about 500 cycles at various current densities. In addition, the Li/LiFePO4 batteries exhibited some discharge capability at high currents up to 1.52mAcm−2 (2C) at 40°C which is very significant for a lithium metal-polymer electrolyte (solvent-free) battery systems. The addition of the IL to lithium metal-polymer electrolyte batteries has resulted in a very promising improvement in performance at moderate temperatures. [Copyright &y& Elsevier]

Abstract: A long cycle-life, high-voltage supercapacitor featuring an activated carbon//poly(3-methylthiophene) hybrid configuration with N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid, a solvent-free green electrolyte, was developed. The cyclability of a laboratory scale cell with electrode mass loading sized for practical uses was tested at 60°C over 16,000 galvanostatic charge–discharge cycles at 10mAcm−2 in the 1.5 and 3.6V voltage range. The reported average and maximum specific energy and power, specific capacitance and capacity, equivalent series resistance and coulombic efficiency over cycling demonstrate the long-term viability of this ionic liquid as green electrolyte for high-voltage hybrid supercapacitors. [Copyright &y& Elsevier]

Abstract: In this work, the characterization regarding the stability of aluminum current collectors in the ionic liquid (IL) N-butyl-N-methylpyrrolidinium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (PYR14FTFSI) by cyclic voltammetry (CV), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) is reported. ILs based on this anion are of great interest because they usually show a good combination of properties when compared with those ILs based on other bis[(perfluoroalkyl)sulfonyl]imide anions. In particular, ILs based on FTFSI− show higher conductivities and lower viscosities than those based on the well-known bis(trifluoromethanesulfonyl)imide (FTFSI−) anion. Furthermore, PYR14FTFSI was tested as electrolyte for high voltage double layer capacitors via constant voltage (float) tests. [Copyright &y& Elsevier]

• The combination of LIG and ionic liquid is proposed to fabricate flexible and high temperature micro-supercapacitor. • This flexible device demonstrates excellent stability even at high bending condition and at 100 °C. • The proposed de-rated voltage analysis define a safe procedure to characterize supercapacitor at high temperature. • This approach will allow to avoid the deterioration of the system performance. Herein we report the fabrication and electrochemical characterization of a novel type of supercapacitor composed of laser-induced graphene (LIG) electrodes, achieved by the laser-writing of polyimide foils, and 1-Butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid as electrolyte. This combination allows the development of a flexible microsupercapacitor suitable for harsh environment application. The influence of several parameters is evaluated with the aim of maximizing the performance of the flexible pouch-bag devices, such as the laser-writing conditions, type of electrode layout and amount of nitrogen-doping. Among them, the laser writing conditions are found to strongly influence the areal capacitance allowing to achieve about 4 mF cm−2, as measured from the galvanostatic charge-discharge measurement at 10 µA cm−2, with a maximum operating potential range of 3 V at 25 °C. In order to probe the potential application of such device, i) flexible pouch architecture and ii) high temperature measurements (considering harsh environment field) are investigated. This type of flexible device exhibits energy and power density as high as 4.5 µWh cm−2 and 90.5 µW cm−2, respectively, high cycling stability as well as acceptable coulombic efficiency above 97% demonstrating good stability even at high bending condition (1.25 cm of bending radius). The electrochemical measurements increasing temperature up to 100 °C reveal a 300% of rise in capacitance and 43% of increment in energy density at de-rated voltage. The obtained energy storage performance are comparable to the best data ever reported for a microsupercapacitor for high temperature application. Moreover, a de-rated voltage analysis (DVA) is proposed as a safe procedure to characterize an energy storage device in an extended temperature range without compromising the system performances. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract: Ionic conductivity is a fundamental property of ionic liquids with its origin and exact nature under debate. Using a specially selected system of pyrrolidinium cations (PYR1x , x =3,4) and sulfonylimide anions (FSI, TFSI, BETI, and IM14)-based ionic liquids we observe a simple and accurate connection between ab initio computed cation and anion volumes and measured molar ionic conductivities. [Copyright &y& Elsevier]