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Room temperature ionic liquids (RTILs) attract much attention as a new type of environmentally benign electrolytes for Li-ion batteries due to their numerous interesting physicochemical properties. Here, in this paper, Li intercalation/deintercalation in presence of the N -butyl- N -methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR 14 TFSI) and N -methyl- N -propylpyrrolidinium bis(fluorosulfonyl)imide (PYR 13 FSI) containing 0.3 M LiTFSI, was evaluated in a thin 100 nm layer of V 2 O 5 deposited on Al substrate by atomic layer deposition. Potentiodynamic tests performed in LiTFSI/Pyr 14 TFSI show a quasi-reversible Li intercalation during 10 cycles (between 2.4 and 5 V) with an average coulombic efficiency of 99%. The capacity, calculated from the 1st cycle, is found to be 182 mAh g −1 , about 19% (±2%) higher than the theoretical capacity reported for V 2 O 5 (147 mAh g −1 ). X-ray photoelectron spectroscopy analysis confirms that the intercalation of more than 1 mol of Li + per V 2 O 5 is achieved as also the possible presence of a solid permeable interface (SPI) layer on the V 2 O 5 surface. Likewise, the Li + in-depth distribution on the V 2 O 5 layer after intercalation in RTILs measured by time-of-flight secondary ion mass spectrometry ion depth profiles, show small irreversible electrode modifications with the presence of lithium through the entire V 2 O 5 layer with significant lithium trapping at the V 2 O 5 layer/Al substrate interface. [ABSTRACT FROM AUTHOR]

The ionic liquid (IL) N -Methyl- N -methoxymethylpyrrolidinium bis(fluorosulfonyl)amide ([Pyr 1,1O1 ][FSA]) was synthesized, and its physicochemical and electrochemical properties were investigated with respect to its application as an electrolyte in lithium-ion secondary batteries operating over a wide temperature range. [Pyr 1,1O1 ][FSA]/Li salt (0.34 mol kg −1 ) composites were prepared by adding lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) into the IL. [Pyr 1,1O1 ][FSA] and [Pyr 1,1O1 ][FSA]/LiTFSA exhibited melting temperatures ( T m ) below −30 °C. [Pyr 1,1O1 ][FSA] exhibited a higher ionic conductivity value as compared with that of the corresponding IL with only alkyl substituents. The electrochemical window for both [Pyr 1,1O1 ][FSA] and [Pyr 1,1O1 ][FSA]/LiTFSA was 5.1 V. Stable lithium deposition and dissolution occurred on a Ni electrode at 25 °C. [ABSTRACT FROM AUTHOR]

Rechargeable Li–S batteries have suffered several technical obstacles, such as rapid capacity fading and low coulombic efficiency. To overcome these problems, we design new electrolytes containing N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide (Pyr 1,2O1 TFSI) and tri(ethylene glycol)dimethyl ether (TEGDME) in mass ratio of 7:3. Moreover, Lithium difluoro(oxalate)borate (LiODFB) is introduced for the modification. Although the addition of LiODFB as additive lead to extremely high viscosity of electrolyte and inferior performance of the cells, the electrolyte containing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 0.84 nm) and LiODFB (0.60 nm) mixture with a total molar concentration of 0.4 mol kg −1 as binary lithium salt shows excellent electrochemical performance. The Pyr 1,2O1 TFSI/TEGDME electrolyte with LiTFSI/LiODFB binary lithium salts in mole ratio of 6:4 is obtained after optimizing ratio. The Li–S cells containing this electrolyte system show excellent capacity and cycle performance, whose initial discharge capacity is 1264.4 mAh g −1 , and retains 911.4 mAh g −1 after 50 cycles with the coulombic efficiency more than 95%. It can be attributed the solid-electrolyte interphase (SEI)-forming ability of LiODFB which protect Li anode from suffering lithium dendrites and prevent the shuttle phenomenon. The novel electrolytes provide good cycling stability and high coulombic efficiency for the Li–S batteries, which is suggested as a promising electrolyte for Li–S batteries. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the structure and physical properties of Li-ion conducting polymer gel electrolytes functionalized with ionic liquid/lithium salt mixtures. The membranes are based on poly(vinylidene fluoride-co-hexafluoropropylene) copolymer, PVdF-HFP, and two ionic liquids: pyrrolidinium cations, N-butyl-N-methylpyrrolidinium (PyR14 +), N-butyl-N-ethylpyrrolidinium (PyR24 +), and bis(trifluoromethanesulfonyl)imide anion (TFSI). The ionic liquids where doped with 0.2 mol kg−-1 LiTFSI. The resulting membranes are freestanding, flexible, and nonvolatile. The structure of the polymer and the interactions between the polymer and the ionic liquid electrolyte have been studied using Raman spectroscopy. The ionic conductivity of the membranes has been studied using dielectric spectroscopy whereas the thermal properties were investigated using differential scanning caloriometry (DSC). These results show that there is a weak, but noticeable, influence on the physical properties of the ionic liquid by the confinement in the membrane. We observe a change in the Li-ion coordination, conformation of the anion, the fragility and a slight increase of the glass transition temperatures for IL/LiTFSI mixtures in the membranes compared to the neat mixtures. The effect can be related to the confinement of the liquid in the membrane and/or to interactions with the PVdF-HFP polymer matrix where the crystallinity is decreased compared to the starting polymer powder. [Copyright &y& Elsevier]

Abstract: Perfluorinated sulfonyl fluoride (PFSF) resin, the precursor of perfluorinated sulfonic acid (PFSA) ionomer is successfully dissolved in perfluorinated solvents, and its hydrophobic nature is utilized to resolve the difficulty of impregnating hydrophilic PFSA solution into hydrophobic porous expanded polytetrafluoroethylene (ePTFE). The composite membrane fabricated through such simple but effective method is well impregnated, leading to better ionic conductivity and lower gas permeability. The fuel cell constructed with PFSF solution based membranes shows superior performance as compared to that of its aqueous PFSA solution based counterpart, which is comparable to that of commercial Nafion® 211. [Copyright &y& Elsevier]

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 hexafluorophosphate (LiPF6) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are used as Li salts in butylmethylpyrrolidinium–bis(trifluoromethanesulfonyl)imide (BMP–TFSI) ionic liquid (IL) electrolyte for Li/LiFePO4 cells. This kind of IL electrolyte shows high thermal stability (>400°C) and non-flammability, and is thus ideal for high-safety applications. At 25°C, a maximum capacity of 113mAhg−1 (at 0.1 C) is found for LiFePO4 in the IL with 0.5M LiTFSI. An excessive LiTFSI concentration leads to a capacity decrease due to reduced electrolyte ionic conductivity. At 50°C, the measured capacity and rate capability are significantly improved compared to those at 25°C. With 1M LiTFSI-doped IL electrolyte (the optimum concentration at 50°C), a capacity of 140mAhg−1 is found at 0.1 C and 45% of the capacity can be retained when the rate increases to 5 C, values which are comparable to those found in a traditional organic electrolyte. In the IL electrolyte, the LiFePO4 electrode shows better cyclic stability at 50°C than it does at 25°C; this trend is opposite to that found in the organic electrolyte. At 50°C, there is negligible capacity loss of LiFePO4 after 100 charge–discharge cycles in 1M LiTFSI-doped BMP–TFSI IL electrolyte. [ABSTRACT FROM AUTHOR]

Abstract: Li-air battery using ionic liquids, N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) amide (DEME-TFSA) and N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)amide (PP13-TFSA), as the solvents for electrolyte have been studied. A significant improvement of discharge capacity has been observed for DEME-TFSA (4315 mAh g−1-electrode at current density of 0.1 mA cm−2), compared with PP13-TFSA. As a discharged product, aggregates reaching 4 μm diameter in size are formed on the surface of cathode, almost 80% of the products are decomposed after charge. By using Raman spectroscopy, two typical peaks attributed to Li2O2 were detected from the discharged aggregates. From the cross sectional SEM images, vacancy occupation ratios of discharged and charged electrodes are estimated, and they are in good agreement with the theoretical calculations. The discharged products formed inside of the cathode are not decomposed completely by charge. [Copyright &y& Elsevier]

Abstract: “Dual-graphite” cells use graphite as intercalation host at both electrodes, where the energy storage mechanism is based on the intercalation of lithium ions into the negative and the intercalation of electrolyte anions into the positive electrode. In this contribution, the electrochemical intercalation of bis(trifluoromethanesulfonyl)imide (TFSI) anions from an ionic liquid-based electrolyte (Pyr14TFSI) into graphite was studied using ex situ and in situ X-ray diffraction. We prove that the TFSI intercalated graphite exists in a series of staged phases. As for this electrode material the discharge capacity can be strongly influenced by the cut-off potential and temperature, the stage transitions and compositions of the TFSI intercalated graphite were determined in dependency of different temperatures and cut-off potentials. From the experimental data, the periodic repeat distance of the graphite intercalation compound, the TFSI gallery height and the maximum stoichiometries of TFSI− at these different conditions are calculated and discussed. [Copyright &y& Elsevier]

Abstract: The availability of safer electrolytes is an important target in the development of the new lithium batteries. The use of Li-doped mixtures based on ionic liquids and organic carbonates seems to be a very promising approach, because it allows to balance the non-flammability, high conductivity, low viscosity and good electrochemical stability. Here, we reported on the characterization of electrolytes solutions based on N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide (PYR1,2O1TFSI), EC/DEC binary system and LiTFSI, as potential safe electrolytes for lithium batteries. The mixtures were studied in terms of flammability tests, thermal features, physical properties, namely conductivity and viscosity, and electrochemical performances. We also carried out a comparison with the pure IL–Li salt system as well as with the standard electrolyte 1.0 M LiPF6 EC–DEC. The best solution showed ionic conductivity exceeding 7 mS cm−1 at 20 °C, room temperature viscosity lower of about 25 cPs and an overall electrochemical window of 4.5 V. With respect to the pure LiTFSI–IL electrolyte, a very stable interface with Li anode was also observed in at least for 20 storage days. This mixture was tested in a LiFePO4-based cell, and showed good performances at 1 C, assuring electrochemical stability for about 250 cycles with ∼100% efficiency. [Copyright &y& Elsevier]

Abstract: Development of lithium–sulfur (Li–S) batteries has suffered from insufficient capacity and poor cycle-life. One of the reasons for these drawbacks is loss of active material, which is associated with the rapid diffusion of highly soluble lithium polysulfides formed as intermediates of discharge products in organic electrolytes, resulting in internal shuttling of lithium polysulfides. The diffusion of lithium polysulfides is determined largely by the physicochemical properties of electrolytes. Therefore, design of the physicochemical properties of the electrolyte to restrain the internal shuttling is vital to promote high performance for Li–S batteries. Here we present a newly designed room temperature ionic liquid (RTIL)-based organic electrolyte for Li–S battery. Our electrolyte provides a trade-off between solubility and diffusion rate of lithium polysulfides by mixing very different physicochemical properties of two solvents: high lithium polysulfide solubility of 1,2-dimethoxyethane (DME), and high viscosity of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI). An adequate composition ratio of mixed PP13-TFSI/DME afforded large capacity, high Coulombic efficiency, improved capacity retention, and suppressed internal shuttling. [Copyright &y& Elsevier]

Abstract: Although lithium bis(trifluoromethanesulfonyl imide) (LiTFSI) has a high thermal stability and fine tolerance to water and is an outstanding candidate as an electrolyte, there is an urgent need to control aluminum corrosion. Here, we explain how we suppressed aluminum corrosion by controlling the LiTFSI concentration. SEM observations and XPS depth profiles of the electrode at high LiTFSI electrolyte concentrations showed that stable passivation film composed of LiF was formed on an aluminum electrode, which prevented the continuous decomposition reaction of the LiTFSI electrolyte. As a result, a lithium-ion battery with LiTFSI demonstrated excellent properties for several cycles without aluminum corrosion, which should accelerate progress in its applications to industry. [Copyright &y& Elsevier]

Abstract: We evaluated the charge–discharge behavior of a graphite electrode in a 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI) ionic liquid. According to the charge–discharge tests, the graphite negative electrode exhibited a high rate of performance in LiTFSI/EMImFSI (TFSI− = bis(trifluoromethylsulfonyl)imide) in the voltage range of 0.005–1.5 V (vs. Li/Li+), and the performance was comparable to that in a conventional organic solution-based electrolyte, LiPF6/EC+DMC. Moreover, the addition of LiBOB (=lithium bis(oxalato)borate) improved the rate capability and low-temperature operation of the graphite negative electrode, most likely owing to the low-resistivity solid electrolyte interface (SEI) derived from LiBOB. These results suggest that EMImFSI is a suitable electrolyte for lithium-ion batteries utilizing graphite negative electrodes and that optimization of the electrolyte composition with an additive can improve battery performance. [Copyright &y& Elsevier]

Abstract: In this paper we report a poly(ethylenglycol)dimethylether–lithium bis(trifluoromethanesulfonyl) imide (PEG500DME–LiTFSI) as high viscosity, safe electrolyte for lithium ion batteries. The high molecular weight of the end-capped ether solvent is reflected as low vapor pressure and excellent thermal stability of the electrolyte, as demonstrated by thermogravimetry, this resulting in remarkable safety content. The electrochemical impedance spectroscopy study of the electrolyte demonstrates a Li-transference number of 0.48, a conductivity of the order of 10−3 S cm−1, and a high interphase stability with the lithium metal, the linear sweep voltammetry indicates an electrochemical stability window extending up to 4.8 V vs. Li/Li+. Furthermore, promising electrochemical performances in terms of reversibility, cycling stability and low charge–discharge polarization are observed using the electrolyte in lithium and in lithium ion batteries using lithium cobalt oxide (LCO) as cathode and titanium dioxide (TiO2) as anode. Hence, this electrolyte is a promising candidate for applications in safe, high performance lithium ion batteries. [Copyright &y& Elsevier]

Abstract: 1-Ethyl-1-methyl piperidinium bis(trifluoromethanesulfonyl)imide (EMP-TFSI) is an ionic liquid with a melting temperature of 85 °C. Although it is a solid salt, it shows good miscibility with carbonate solvents, which allows EMP-TFSI to be used as a co-solvent in these systems. Ethylene carbonate is another solid co-solvent used in Li-ion batteries. Due to its smaller cationic size, EMP-TFSI provides better conductivity as a co-solvent than 1-methyl-1-propyl piperidinium bis(trifluoromethanesulfonyl)imide (MPP-TFSI), which is the smallest room-temperature piperidinium liquid salt known. In cells with 50 wt% IL and 50 wt% carbonate electrolyte, an EMP-TFSI mixed electrolyte performs better than an MPP-TFSI mixed electrolyte. Additionally, the discharge capacity values obtained from rate capability tests carried out with mixed EMP-TFSI are as good as those conducted with a pure carbonate electrolyte. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: The lab-scale manufacturing of Li/LiFePO4 and Li4Ti5O12/LiFePO4 stacked battery prototypes and their performance characterization are described here. The prototypes were realized in the frame of an European Project devoted to the development of greener and safer lithium batteries, based on ionic liquid electrolytes, for integration with photovoltaic panels. N-Butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) and N-butyl-N-methylpyrrolidinium bis(fluoro-methanesulfonyl)imide (PYR14FSI), selected as the ionic liquids (ILs), were used to formulate the poly(ethylene oxide)-LiN(SO2CF3)2-PYR14TFSI (PEO-LiTFSI-PYR14TFSI) polymer electrolyte and the LiTFSI-PYR14FSI liquid electrolyte, which were employed to produce lithium metal and lithium-ion prototypes, respectively. The composite electrodes for the lithium metal and lithium-ion prototypes were prepared through, respectively, a solvent-free and a water-based procedure route. The performance of the lithium battery prototypes was evaluated in terms of specific capacity, energy, cycle life and coulombic efficiency at different current densities. The results have indicated high reproducibility and the feasibility of scaling-up solvent-free, lithium batteries based on ionic liquids for low and mid rate applications such as renewable energy storage. [Copyright &y& Elsevier]

Lithium bis (trifluoromethane sulfonyl) imide (Li-TFSI) and 4- tert -butyl pyridine (TBP) doped 2,2′,7,7′-tetrakis (N, N - p -dimethoxy-phenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD) is the most commonly used hole-transporter in perovskite solar cells (PSCs). Although the introduction of both Li-TFSI and TBP can significantly enhance the conductivity of spiro-OMeTAD and thereby improve the power conversion efficiencies (PCEs) of PSCs, the dopants unfortunately render hysteresis and reduce stabilities of PSCs. In this paper, we have synthesized hydrophobic p-type PbS nanocrystals and prepared a binary hole-transporter by mixing PbS and Spiro-OMeTAD (PbS/Spiro-OMeTAD), which therefore avoids the use of traditional hygroscopic Li-TFSI and volatile TBP dual additives. The PbS/Spiro-OMeTAD exhibits excellent conductivity and well-matched valence band with that of perovskite. PSCs incorporating PbS/Spiro-OMeTAD as the hole transporting layer (HTL) can obtain a highest PCE of 20.11% and show excellent long-term stability, which is much better than the controlled device with Li-TFSI and TBP doped Spiro-OMeTAD as the HTL. • A binary hole-transporter is prepared with undoped Spiro-OMeTAD and PbS nanocrystals. • The binary hole-transporter avoids the Li-TFSI and TBP additives. • The binary hole-transporter has a well-matched energy level with perovskite. • The corresponding devices achieve 20.11% PCE and excellent long-term stability. [ABSTRACT FROM AUTHOR]