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The room-temperature molten salt mixture of N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis(trifluoromethanesulfonyl) imide ([DEME][TFSI]) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt is herein reported as electrolyte for application in Li-O 2 batteries. The [DEME][TFSI]-LiTFSI solution is studied in terms of ionic conductivity, viscosity, electrochemical stability, and compatibility with lithium metal at 30 °C, 40 °C, and 60 °C. The electrolyte shows suitable properties for application in Li-O 2 battery, allowing a reversible, low-polarization discharge-charge performance with a capacity of about 13 Ah g-1carbon in the positive electrode and coulombic efficiency approaching 100 %. The reversibility of the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) is demonstrated by ex situ XRD and SEM studies. Furthermore, the study of the cycling behavior of the Li-O 2 cell using the [DEME][TFSI]-LiTFSI electrolyte at increasing temperatures (from 30 to 60 °C) evidences enhanced energy efficiency together with morphology changes of the deposited species at the working electrode. In addition, the use of carbon-coated Zn 0.9 Fe 0.1 O (TMO-C) lithium-conversion anode in an ionic-liquid-based Li-ion/oxygen configuration is preliminarily demonstrated., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The use of ionic liquids (ILs) as advanced electrolyte components in electrochemical energy-storage devices is one of the most appealing and emerging options. However, although ILs are hailed as safer and eco-friendly electrolytes, to overcome the limitations imposed by the highly volatile/combustible carbonate-based electrolytes, full-scale and precise appraisal of their overall safety levels under abuse conditions still needs to be fully addressed. With the aim of providing this level of information on the thermal and chemical stabilities, as well as actual fire hazards, herein, a detailed investigation of the short- and long-term thermal stabilities, biodegradability, and combustion behavior of various pyrrolidinium-based ILs, with different alkyl chain lengths, counteranions, and cations, as well as the effect of doping with lithium salts, is described., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work, the individual and combined effects of an ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and ceramic filler silicon dioxide on the thermal and electrochemical properties of poly(ethylene oxide) electrolytes have been investigated. The electrolyte containing both components has the lowest glass transition (-60 °C) and melting temperatures (27 °C), the highest conductivity at any investigated temperature, and the highest limiting current density (at 40 °C). This solid polymer electrolyte also exhibits the best long-term cycling performance in Li/LiFePO4 cells., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 (Na3 Zr2 Si2 PO12) ceramic solid electrolyte, making this system extremely promising for cost-efficient and environmentally friendly large-scale energy storage., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The characterization of separators for Li-ion or Li-metal batteries incorporating hydrophobic ionic liquid electrolytes is reported herein. Ionic liquids made of N-butyl-N-methylpyrrolidinium (PYR14+) or N-methoxyethyl-N-methylpyrrolidinium (PYR12O1+), paired with bis(trifluoromethanesulfonyl)imide (TFSI-) or bis(fluorosulfonyl)imide (FSI-) anions, were tested in combination with separators having different chemistries and morphologies in terms of wetting behavior, Gurley and McMullin number, as well as Li/(Separator+Electrolyte) interfacial properties. It is shown that non-functionalized microporous polyolefin separators are poorly wetted by FSI--based electrolytes (contrary to TFSI--based electrolytes), while the ceramic coated separator Separion® allows good wetting with all electrolytes. Furthermore, by comparing the lithium solid electrolyte interphase (SEI) resistance evolution at open circuit and during cycling, depending on separator morphologies and chemistries, it is possible to propose a scale for SEI forming properties in the order: PYR12O1FSI>PYR14FSI>PYR14TFSI>PYR12O1TFSI. Finally, the impact the separator morphology is evidenced by the SEI resistance evolution and by comparing Li electrodes cycled using separators with two different morphologies.

In this work, the electrochemical stability and lithium plating/stripping performance of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) are reported, by investigating the behavior of Li metal electrodes in symmetrical Li/electrolyte/Li cells. Electrochemical impedance spectroscopy measurements and galvanostatic cycling at different temperatures are performed to analyze the influence of temperature on the stabilization of the solid electrolyte interphase (SEI), showing that TFSI-based ionic liquids (ILs) rank among the best candidates for long-lasting Li-air cells.

Aluminum−sulfur (Al−S) batteries are promising energy storage devices due to their high theoretical capacity, low cost, and high safety. However, the high viscosity and inferior ion transport of conventionally used ionic liquid electrolytes (ILEs) limit the kinetics of Al−S batteries, especially at sub‐zero temperatures. Herein, locally concentrated ionic liquid electrolytes (LCILE) formed via diluting the ILEs with non‐solvating 1,2‐difluorobenzene (dFBn) co‐solvent are proposed for wide‐temperature‐range Al−S batteries. The addition of dFBn effectively promotes the fluidity and ionic conductivity without affecting the AlCl4−/Al2Cl7− equilibrium, which preserves the reversible stripping/plating of aluminum and further promotes the overall kinetics of Al−S batteries. As a result, Al−S cells employing the LCILE exhibit higher specific capacity, better cyclability, and lower polarization with respect to the neat ILE in a wide temperature range from −20 to 40 °C. For instance, Al−S batteries employing the LCILE sustain a remarkable capacity of 507 mAh g−1 after 300 cycles at 20 °C, while only 229 mAh g−1 is delivered with the dFBn‐free electrolyte under the same condition. This work demonstrates the favorable use of LCILEs for wide‐temperature Al−S batteries. [ABSTRACT FROM AUTHOR]

Lithium metal is a promising anode material for next‐generation high‐energy‐density batteries but suffers from low stripping/plating Coulombic efficiency and dendritic growth particularly at sub‐zero temperatures. Herein, a poorly‐flammable, locally concentrated ionic liquid electrolyte with a wide liquidus range extending well below 0 °C is proposed for low‐temperature lithium metal batteries. Its all‐anion Li+ solvation and phase‐nano‐segregation solution structure are sustained at low temperatures, which, together with a solid electrolyte interphase rich in inorganic compounds, enable dendrite‐free operation of lithium metal anodes at −20 °C and 0.5 mA cm−2, with a Coulombic efficiency of 98.9 %. As a result, lithium metal batteries coupling thin lithium metal anodes (4 mAh cm−2) and high‐loading LiNi0.8Co0.15Al0.05O2 cathodes (10 mg cm−2) retain 70 % of the initial capacity after 100 cycles at −20 °C. These results, as a proof of concept, demonstrate the applicability of locally concentrated ionic liquid electrolytes for low‐temperature lithium metal batteries. [ABSTRACT FROM AUTHOR]

Non‐flammable ionic liquid electrolytes (ILEs) are well‐known candidates for safer and long‐lifespan lithium metal batteries (LMBs). However, the high viscosity and insufficient Li+ transport limit their practical application. Recently, non‐solvating and low‐viscosity co‐solvents diluting ILEs without affecting the local Li+ solvation structure are employed to solve these problems. The diluted electrolytes, i.e., locally concentrated ionic liquid electrolytes (LCILEs), exhibiting lower viscosity, faster Li+ transport, and enhanced compatibility toward lithium metal anodes, are feasible options for the next‐generation high‐energy‐density LMBs. Herein, the progress of the recently developed LCILEs are summarised, including their physicochemical properties, solution structures, and applications in LMBs with a variety of high‐energy cathode materials. Lastly, a perspective on the future research directions of LCILEs to further understanding and achieve improved cell performances is outlined. [ABSTRACT FROM AUTHOR]

X-ray scattering measurements were utilized to probe the effects of pressure on a series of ionic liquids, N-alkyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr1A-TFSI) (A = 3, 6, and 9), along with mixtures of ionic liquid and 30 mol.% lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. No evidence was found for crystallization of the pure ionic liquids or salt mixtures even at pressures up to 9.2 GPa. No phase separation or demixing was observed for the ionic liquid and salt mixtures. Shifts in the peak positions are indicative of compression of the ionic liquids and mixtures up to 2 GPa, after which samples reach a region of relative incompressibility, possibly indicative of a transition to a glassy state. With the application of pressure, the intensity of the prepeak was found to decrease significantly, indicating a reduction in cation alkyl chain aggregation. Additionally, incompressibility of the scattering peak associated with the distance between like-charges in the pure ionic liquids compared to that in mixtures with lithium salt suggests that the application of pressure could inhibit Li+ coordination with TFSI to form Li[TFSI2] complexes. This inhibition occurs through the suppression of TFSI in the trans conformer, in favor of the smaller cis conformer, at high pressures. [ABSTRACT FROM AUTHOR]

Lithium metal batteries (LMBs) with nickel‐rich cathodes are promising candidates for next‐generation, high‐energy batteries. However, the highly reactive electrodes usually exhibit poor interfacial compatibility with conventional electrolytes, leading to limited cyclability. Herein, a locally concentrated ionic liquid electrolyte (LCILE) consisting of lithium bis(fluorosulfonyl)imide (LiFSI), 1‐ethyl‐3‐methylimidazolium bis(fluorosulfonyl)imide (EmimFSI), and 1,2‐difluorobenzene (dFBn) is designed to overcome this challenge. As a cosolvent, dFBn not only promotes the Li+ transport with respect to the electrolyte based on the ionic liquid only, but also has beneficial effects on the electrode/electrolyte interphases (EEIs) on lithium metal anodes (LMAs) and LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. As a result, the developed LCILE enables dendrite‐free cycling of LMAs with a coulombic efficiency (CE) up to 99.57% at 0.5 mA cm−2 and highly stable cycling of Li/NMC811 cells (4.4 V) at C/3 charge and 1 C discharge (1 C = 2 mA cm−2) for 500 cycles with a capacity retention of 93%. In contrast, the dFBn‐free electrolyte achieves lithium stripping/plating CE, and the Li/NMC811 cells' capacity retention of only 98.22% and 16%, respectively under the same conditions. The insight into the coordination structure, promoted Li+ transport, and EEI characteristics gives fundamental information essential for further developing (IL‐based) electrolytes for long‐life, high‐energy LMBs. [ABSTRACT FROM AUTHOR]

To tackle the poor chemical/electrochemical stability of Li1+xAlxTi2‐x(PO4)3 (LATP) against Li and poor electrode|electrolyte interfacial contact, a thin poly[2,3‐bis(2,2,6,6‐tetramethylpiperidine‐N‐oxycarbonyl)norbornene] (PTNB) protection layer is applied with a small amount of ionic liquid electrolyte (ILE). This enables study of the impact of ILEs with modulated composition, such as 0.3 lithium bis(fluoromethanesulfonyl)imide (LiFSI)‐0.7 N‐butyl‐N‐methylpyrrolidinium bis(fluoromethanesulfonyl)imide (Pyr14FSI) and 0.3 LiFSI‐0.35 Pyr14FSI‐0.35 N‐butyl‐N‐methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI), on the interfacial stability of PTNB@Li||PTNB@Li and PTNB@Li||LiNi0.8Co0.1Mn0.1O2 cells. The addition of Pyr14TFSI leads to better thermal and electrochemical stability. Furthermore, Pyr14TFSI facilitates the formation of a more stable Li|hybrid electrolyte interface, as verified by the absence of lithium "pitting corrosion islands" and fibrous dendrites, leading to a substantially extended lithium stripping‐plating cycling lifetime (>900 h). Even after 500 cycles (0.5C), PTNB@Li||LiNi0.8Co0.1Mn0.1O2 cells achieve an impressive capacity retention of 89.1 % and an average Coulombic efficiency of 98.6 %. These findings reveal a feasible strategy to enhance the interfacial stability between Li and LATP by selectively mixing different ionic liquids. [ABSTRACT FROM AUTHOR]

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]

FSI−‐based ionic liquids (ILs) are promising electrolyte candidates for long‐life and safe lithium metal batteries (LMBs). However, their practical application is hindered by sluggish Li+ transport at room temperature. Herein, it is shown that additions of bis(2,2,2‐trifluoroethyl) ether (BTFE) to LiFSI‐Pyr14FSI ILs can effectively mitigate this shortcoming, while maintaining ILs′ high compatibility with lithium metal. Raman spectroscopy and small‐angle X‐ray scattering indicate that the promoted Li+ transport in the optimized electrolyte, [LiFSI]3[Pyr14FSI]4[BTFE]4 (Li3Py4BT4), originates from the reduced solution viscosity and increased formation of Li+‐FSI− complexes, which are associated with the low viscosity and non‐coordinating character of BTFE. As a result, Li/LiFePO4 (LFP) cells using Li3Py4BT4 electrolyte reach 150 mAh g−1 at 1 C rate (1 mA cm−2) and a capacity retention of 94.6% after 400 cycles, revealing better characteristics with respect to the cells employing the LiFSI‐Pyr14FSI (operate only a few cycles) and commercial carbonate (80% retention after only 218 cycles) electrolytes. A wide operating temperature (from −10 to 40 °C) of the Li/Li3Py4BT4/LFP cells and a good compatibility of Li3Py4BT4 with LiNi0.5Mn0.3Co0.2O2 (NMC532) are demonstrated also. The insight into the enhanced Li+ transport and solid electrolyte interphase characteristics suggests valuable information to develop IL‐based electrolytes for LMBs. [ABSTRACT FROM AUTHOR]

Cyano‐based ionic liquids (ILs) are prime candidates for the manufacturing of cheaper and safer batteries due to their inherently low‐volatility and absence of expensive fluorinated species. In this work, N‐methyl‐N‐butylpyrrolidinium (Pyr14)‐based ILs featuring two different cyano‐based anions, i.e., dicyanamide (DCA) and tricyanomethanide (TCM), and their mixture with the respective Li salts (1:9 salt:IL mole ratio), alongside their combination (DCA–TCM), are evaluated as potential electrolytes for lithium metal batteries (LMBs). The electrolytes display significant ionic conductivity at room temperature (5 mS cm−1) alongside an electrochemical stability window up to 4 V, suitable for low‐voltage LMBs such as Li–sulfur, as well as promising cycling stability. In addition to the detailed physicochemical (viscosity, conductivity) and electrochemical (electrochemical stability window, stripping/plating, and impedance test in symmetrical Li cells) characterization, the solid electrolyte interphase (SEI) formed in this class of ionic liquids is studied for the first time. X‐ray photoelectron spectroscopy (XPS) provides evidence for an SEI dominated by a polymer‐rich layer including carbon–nitrogen single, double, and triple bonds, which provides high ionic conductivity and mechanical stability, leading to the aforementioned cycling stability. Finally, a molecular insight is achieved by density functional theory (DFT) and classic molecular dynamics simulations both supporting the experimental evidence. [ABSTRACT FROM AUTHOR]

Electrolyte chemistry is critical for any energy‐storage device. Low‐cost and sustainable rechargeable batteries based on organic redox‐active materials are of great interest to tackle resource and performance limitations of current batteries with metal‐based active materials. Organic active materials can be used not only as solid electrodes in the classic lithium‐ion battery (LIB) setup, but also as redox fluids in redox‐flow batteries (RFBs). Accordingly, they have suitability for mobile and stationary applications, respectively. Herein, different types of electrolytes, recent advances for designing better performing electrolytes, and remaining scientific challenges are discussed and summarized. Due to different configurations and requirements between LIBs and RFBs, the similarities and differences for choosing suitable electrolytes are discussed. Both general and specific strategies for promoting the utilization of organic active materials are covered. [ABSTRACT FROM AUTHOR]

An innovative one‐pot synthetic process that uses water as the only processing solvent was used to obtain ionic liquids (ILs) in a yield of approximately 95 mol % and purity greater than 99.3 wt % (<2 ppm each of lithium, bromide and moisture) in a processing time of 1 h. Since no heating is needed for carrying out the reaction and no purification through sorbents is required, energy, time and chemicals can be saved to minimize waste production. The physicochemical and electrochemical validation, including tests in batteries, reported herein shows that the above‐mentioned ILs have properties analogous to those of ILs prepared by standard reported procedures and show high performance without any further purification step through sorbents. These characteristics, in combination with low cost, easy execution and scale‐up, sustainability and versatility, make the one‐pot process even more appealing, especially for industrial‐scale applications. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) have been widely explored as alternative electrolytes to combat the safety issues associated with conventional organic electrolytes. However, hindered by their relatively high viscosity, the electrochemical performances of IL‐based cells are generally assessed at medium‐to‐high temperature and limited cycling rate. A suitable combination of alkoxy‐functionalized cations with asymmetric imide anions can effectively lower the lattice energy and improve the fluidity of the IL material. The Li/Li1.2Ni0.2Mn0.6O2 cell employing N‐N‐diethyl‐N‐methyl‐N‐(2‐methoxyethyl)ammonium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (DEMEFTFSI)‐based electrolyte delivered an initial capacity of 153 mAh g−1 within the voltage range of 2.5–4.6 V, with a capacity retention of 65.5 % after 500 cycles and stable coulombic efficiencies exceeding 99.5 %. Moreover, preliminary battery tests demonstrated that the drawbacks in terms of rate capability could be improved by using Li‐concentrated IL‐based electrolytes. The improved room‐temperature rate performance of these electrolytes was likely owing to the formation of Li+‐containing aggregate species, changing the concentration‐dependent Li‐ion transport mechanism. [ABSTRACT FROM AUTHOR]

Here we report on the complex nature of the phase diagram of N-alkyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide ionic liquids using several complementary techniques and on their structural order in the molten state using small-wide angle x-ray scattering. The latter study indicates that the piperidinium aliphatic alkyl chains tend to aggregate, forming alkyl domains embedded into polar regions, similar to what we recently highlighted in the case of other ionic liquids. [ABSTRACT FROM AUTHOR]

Owing to their exceptional electrochemical stability, ionic liquids (ILs) are highly promising electrolytes for high voltage electrochemical double layer capacitors (EDLCs). However, these molten salts often suffer from high viscosity and low conductivity, strongly affecting their application at room temperature. In this work the potential role of N‐butyl‐N‐methyl‐pyrrolidinium 4,5‐dicyano‐2‐(trifluoromethyl) imidazole (Pyr14TDI) as electrolyte component is evaluated for the first time. Although it is classified as an IL, its melting point at 48 °C hinders the use of the pure IL as solvent‐free electrolyte at medium‐to‐low temperatures. For this reason, mixtures with propylene carbonate (PC) are investigated to widen its temperature operation range (−30 to 60 °C). Different Pyr14TDI:PC ratios are investigated, from diluted solution (1 : 3 w/w) to solvent‐in‐salt (3 : 1 w/w). The properties of such electrolytes are determined in terms of viscosity, density, flash point, ionic conductivity, and electrochemical performance in EDLC. By proper electrode balancing, a maximum cell voltage of 3.3 V is achieved in case of PC:Pyr14TDI (1 : 3). However, despite the voltage limitation to 3 V, the highest specific energy and power values are obtained with the most diluted solution (3 : 1). Binary mixtures of N‐butyl‐N‐methyl‐pyrrolidinium 4,5‐dicyano‐2‐(trifluoromethyl) imidazole (Pyr14TDI) and propylene carbonate (PC) are studied as electrolytes for high voltage electrochemical double layer capacitors (EDLC). By tuning the composition of the solution, extended liquid range and conductivity can be achieved. A maximum cell voltage as high as 3.3 V and promising stability represent a substantial improvement compared to current state‐of‐the‐art EDLC electrolytes. [ABSTRACT FROM AUTHOR]

Aluminum, a cost‐effective and abundant metal capable of alloying with Li up to around 1000 mAh g−1, is a very appealing anode material for high energy density lithium‐ion batteries (LIBs). However, despite repeated efforts in the past three decades, reports presenting stable cycling performance are extremely rare. This study concerns recent findings on the highly reversible (de)lithiation of a micro‐sized Al anode (m‐Al) by using bis(fluorosulfonyl)imide (FSI)‐based electrolytes. By using this kind of electrolyte, m‐Al can deliver a specific capacity over 900 mAh g−1 and superior Coulombic efficiency (96.8 %) to traditional carbonate‐ and glyme‐based electrolytes (87.8 % and 88.1 %, respectively), which represents the best performance ever obtained for an Al anode without sophisticated structure design. The significantly improved electrochemical performance, which paves the way to realizing high‐performance Al‐based high energy density LIBs, can be attributed the peculiar solid–electrolyte interphase (SEI) formed by the FSI‐containing electrolyte. A better electrolyte for Al anode: This study concerns recent findings on the highly reversible (de)lithiation of a micro‐sized Al anode (m‐Al) by using bis(fluorosulfonyl)imide‐based electrolytes. By using this kind of electrolyte, m‐Al can deliver a specific capacity over 900 mAh g−1 and superior Coulombic efficiency (96.8 %) to traditional electrolytes. The significantly improved electrochemical performance is attributed to the peculiar solid–electrolyte interphase (SEI). [ABSTRACT FROM AUTHOR]

In binary ionic liquid/Li salt mixtures with the novel asymmetric anion FTFSI, electrophoretic mobility μi values of all ion species were determined using electrophoretic NMR. Li was determined to migrate in negatively charged Li-anion clusters towards the anode. This vehicular transport mechanism was shown to have decreasing relevance at elevated salt concentrations. [ABSTRACT FROM AUTHOR]

Abstract: Cathode configurations reported herein are alternative to the most diffused ones for application in lithium‐oxygen batteries, using an ionic liquid‐based electrolyte. The electrodes employ high surface area conductive carbon as the reaction host, and polytetrafluoroethylene as the binding agent to enhance the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) reversibility. Roll‐pressed, self‐standing electrodes (SSEs) and thinner, spray deposited electrodes (SDEs) are characterized in lithium‐oxygen cells using an ionic liquid (IL) based electrolyte formed by mixing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt and N,N‐diethyl‐N‐(2‐methoxyethyl)‐N‐methylammonium bis(trifluoromethanesulfonyl)imide (DEMETFSI). The electrochemical results reveal reversible reactions for both electrode configurations, but improved electrochemical performance for the self‐standing electrodes in lithium‐oxygen cells. These electrodes show charge/discharge polarizations at 60 °C limited to 0.4 V, with capacity up to 1 mAh cm−2 and energy efficiency of about 88 %, while the spray deposited electrodes reveal, under the same conditions, a polarization of 0.6 V and energy efficiency of 80 %. The roll pressed electrode combined with the DEMETFSI‐LiTFSI electrolyte and a composite LixSn‐C alloy anode forms a full Li‐ion oxygen cell showing extremely limited polarization, and remarkable energy efficiency. [ABSTRACT FROM AUTHOR]

This study is essentially based on innovative electrolytes such as the organic salt N-methyl-N-butylpyrrolidinium tetrafluoroborate (Pyr14BF4) dissolved in propylene carbonate (PC) and the pure ionic liquid (N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) and its solution in PC. Activated carbon cloths were used as self-standing binder-free electrodes. It is found that the presence of impurities in carbon electrodes may lead to electrolyte decomposition and electrode degradation which notably affect the electrochemical double-layer capacitor (EDLC) performance. Such processes greatly depend on the composition of both the electrode and the electrolyte, being much less significant with solvent-containing electrolytes. By raising the operation temperature to 60 °C, the EDLC performance in the ionic liquid Pyr14TFSI is notably improved due to a relevant decrease in the viscosity and increase in ionic conductivity. By contrast, the presence of impurities, e.g., Zn and Al, in the electrodes remarkably reduces the electrolyte stability and a thick layer of decomposition products completely covers the carbon fibers after cycling at high temperature. The ionic liquid in solution maintains the high maximum operative voltage of the net ionic liquid whereas its viscosity and ionic conductivity are close to those of the conventional Et4NBF4/PC. Furthermore, the presence of propylene carbonate as solvent prevents to some extent the ionic liquid degradation. [ABSTRACT FROM AUTHOR]

Vanadium oxide is an attractive high-capacity cathode material for metal batteries, but it is affected by severe capacity fading upon cycling in conventional electrolytes. In this manuscript, it is shown that the cycling ability of vanadium oxide (V2O5) aerogel cathodes can be substantially improved by using properly designed electrolytes. In particular, the electrochemical characterization of V2O5 aerogel, in combination with room-temperature ionic liquid-based electrolytes, demonstrates cycling stabilities above 600 cycles with capacity retentions higher than 80 %. Furthermore, the ionic liquid-based electrolytes grant cyclability and safety in lithium-metal batteries even above room temperature. [ABSTRACT FROM AUTHOR]

A new lithium-ion battery chemistry is presented based on a conversion-alloying anode material, a carbon-coated Fe-doped ZnO (TMO-C), and a LiNi1/3Mn1/3Co1/3O2 (NMC) cathode. Both electrodes were fabricated using an environmentally friendly cellulose-based binding agent. The performance of the new lithium-ion battery was evaluated with a conventional, carbonate-based electrolyte (ethylene carbonate:diethyl carbonate-1 m lithium hexafluorophosphate, EC:DEC 1 m LiPF6) and an ionic liquid (IL)-based electrolyte ( N-butyl- N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide-0.2 m lithium bis(trifluoromethanesulfonyl)imide, Pyr14TFSI 0.2 m LiTFSI), respectively. Galvanostatic charge/discharge tests revealed a reduced rate capability of the TMO-C/Pyr14TFSI 0.2 m LiTFSI/NMC full-cell compared to the organic electrolyte, but the coulombic efficiency was significantly enhanced. Moreover, the IL-based electrolyte substantially improves the safety of the system due to a higher thermal stability of the formed anodic solid electrolyte interphase and the IL electrolyte itself. While the carbonate-based electrolyte shows sudden degradation reactions, the IL exhibits a slowly increasing heat flow, which does not constitute a serious safety risk. [ABSTRACT FROM AUTHOR]

A CuO-Carbon anode storing lithium through a conversion mechanism is electrochemically studied in cells employing Pyr14TFSI-LiTFSI electrolyte [Pyr14: N-butyl-N-methylpyrrolidinium], [TFSI: bis(trifluoromethanesulfonyl) imide]. The electrode delivers a specific capacity as high as 580 mAh g−1 with a coulombic efficiency exceeding 98 %. The combination of CuO-carbon with a high-voltage LiNi0.5Mn1.5O4 cathode in the ionic liquid electrolyte produces a Li-ion battery with an average operating voltage of 3 V and specific capacity of approximately 120 mAh g−1. The cell, employing easily-prepared electrodes and a safe ionic liquid electrolyte, represents a good candidate for use in sustainable power sources. [ABSTRACT FROM AUTHOR]

In this paper, we report an advanced long-life lithium ion battery, employing a Pyr14TFSI-LiTFSI non-flammable ionic liquid (IL) electrolyte, a nanostructured tin carbon (Sn-C) nanocomposite anode, and a layered LiNi1/3Co1/3Mn1/3O2 (NMC) cathode. The IL-based electrolyte is characterized in terms of conductivity and viscosity at various temperatures, revealing a Vogel-Tammann-Fulcher (VTF) trend. Lithium half-cells employing the Sn-C anode and NMC cathode in the Pyr14TFSI-LiTFSI electrolyte are investigated by galvanostatic cycling at various temperatures, demonstrating the full compatibility of the electrolyte with the selected electrode materials. The NMC and Sn-C electrodes are combined into a cathode-limited full cell, which is subjected to prolonged cycling at 40 °C, revealing a very stable capacity of about 140 mAh g−1 and retention above 99 % over 400 cycles. The electrode/electrolyte interface is further characterized through a combination of electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) investigations upon cell cycling. The remarkable performances reported here definitively indicate that IL-based lithium ion cells are suitable batteries for application in electric vehicles. [ABSTRACT FROM AUTHOR]

We report a systematic investigation of Na-based electrolytes that comprise various NaX [X=hexafluorophosphate (PF6), perchlorate (ClO4), bis(trifluoromethanesulfonyl)imide (TFSI), fluorosulfonyl-(trifluoromethanesulfonyl)imide (FTFSI), and bis(fluorosulfonyl)imide (FSI)] salts and solvent mixtures [ethylene carbonate (EC)/dimethyl carbonate (DMC), EC/diethyl carbonate (DEC), and EC/propylene carbonate (PC)] with respect to the Al current collector stability, formation of soluble degradation compounds, reactivity towards sodiated hard carbon (Na x-HC), and solid-electrolyte interphase (SEI) layer formation. Cyclic voltammetry demonstrates that the stability of Al is highly influenced by the nature of the anions, solvents, and additives. GC-MS analysis reveals that the formation of SEI telltales depends on the nature of the linear alkyl carbonates and the battery chemistry (Li+ vs. Na+). FTIR spectroscopy shows that double alkyl carbonates are the main components of the SEI layer on Na x-HC. In the presence of Na salts, EC/DMC and EC/DEC presented a higher reactivity towards Na x-HC than EC/PC. For a fixed solvent mixture, the onset temperature follows the sequence NaClO4646

We study the liquid mixture of sodium bis(trifluoromethanesulfonyl)imide in N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr 14 TFSI-NaTFSI) for application in sodium-ion batteries. The ionic liquid-based electrolyte is characterized in terms of electrochemical and thermal properties. Ionic conductivity and electrochemical stability windows are evaluated through electrochemical impedance spectroscopy (EIS) measurements and voltammetry tests, respectively. The thermal stability is evaluated by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Moreover, the suitability of the IL-electrolyte is preliminary verified in half and in full-cells at room temperature, using P2-Na 0.6 Ni 0.22 Fe 0.11 Mn 0.66 O 2 layered oxide cathode and nanostructured Sb–C composite anode. The cell shows promising characteristics with a working voltage of about 2.7 V and a delivered capacity of about 100 mAh g −1 . Despite requiring further optimization in terms of cycle life and energy density, the data here reported suggest the suitability of the ionic liquid electrolyte for application in sodium-ion battery. [ABSTRACT FROM AUTHOR]

The advent of solid-state polymer electrolytes for application in lithium batteries took place more than four decades ago when the ability of polyethylene oxide (PEO) to dissolve suitable lithium salts was demonstrated. Since then, many modifications of this basic system have been proposed and tested, involving the addition of conventional, carbonate-based electrolytes, low molecular weight polymers, ceramic fillers, and others. This Review focuses on ternary polymer electrolytes, that is, ion-conducting systems consisting of a polymer incorporating two salts, one bearing the lithium cation and the other introducing additional anions capable of plasticizing the polymer chains. Assessing the state of the research field of solid-state, ternary polymer electrolytes, while giving background on the whole field of polymer electrolytes, this Review is expected to stimulate new thoughts and ideas on the challenges and opportunities of lithium-metal batteries. [ABSTRACT FROM AUTHOR]

Despite the considerable initial optimism behind its development and prospective commercialization, the Li/air battery chemistry has now reached a mature stage of development, which has served to highlight the main underlying technological limitations, as well as what can realistically be expected from it. One of the main challenges is the control of the discharge product morphology, that is, Li2O2, onto the positive electrode. In this article, we show how the three-phase configuration required to ensure cell operation can be induced in a two-phase system made of mesoporous carbon and an ionic liquid electrolyte [ N-butyl- N-methylpyrrolidinium bis(trifluoromethane sulfonyl)imide, Pyr14TFSI] by means of an oxygen-bubbling device (OBD) and a peristaltic pump. The use of a non-flammable, non-volatile electrolyte ensures long-term, extensive discharging (up to 4.78 mAh cm−2), as well as operation at temperatures higher than room temperature. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are becoming increasingly important for electrifying the modern transportation system and, thus, hold the promise to enable sustainable mobility in the future. However, their large-scale application is hindered by severe safety concerns when the cells are exposed to mechanical, thermal, or electrical abuse conditions. These safety issues are intrinsically related to their superior energy density, combined with the (present) utilization of highly volatile and flammable organic- solvent-based electrolytes. Herein, state-of-the-art electrolyte systems and potential alternatives are briefly surveyed, with a particular focus on their (inherent) safety characteristics. The challenges, which so far prevent the widespread replacement of organic carbonate-based electrolytes with LiPF6 as the conducting salt, are also reviewed herein. Starting from rather "facile" electrolyte modifications by (partially) replacing the organic solvent or lithium salt and/or the addition of functional electrolyte additives, conceptually new electrolyte systems, including ionic liquids, solvent-free, and/or gelled polymer-based electrolytes, as well as solid-state electrolytes, are also considered. Indeed, the opportunities for designing new electrolytes appear to be almost infinite, which certainly complicates strict classification of such systems and a fundamental understanding of their properties. Nevertheless, these innumerable opportunities also provide a great chance of developing highly functionalized, new electrolyte systems, which may overcome the afore-mentioned safety concerns, while also offering enhanced mechanical, thermal, physicochemical, and electrochemical performance. [ABSTRACT FROM AUTHOR]

The advent of ionic liquids (ILs) as eco-friendly and promising reaction media has opened new frontiers in the field of electrochemical energy storage. Beyond their use as electrolyte components in batteries and supercapacitors, ILs have unique properties that make them suitable as functional advanced materials, media for materials production, and components for preparing highly engineered functional products. Aiming at offering an in-depth review on the newly emerging IL-based green synthesis processes of energy storage materials, this Review provides an overview of the role of ILs in the synthesis of materials for batteries, supercapacitors, and green electrode processing. It is expected that this Review will assess the status quo of the research field and thereby stimulate new thoughts and ideas on the emerging challenges and opportunities of IL-based syntheses of energy materials. [ABSTRACT FROM AUTHOR]

The characterization of separators for Li-ion or Li-metal batteries incorporating hydrophobic ionic liquid electrolytes is reported herein. Ionic liquids made of N-butyl-N- methylpyrrolidinium (PYR14+) or N-methoxyethyl-N-methylpyrrolidinium (PYR12O1+), paired with bis(trifluoromethanesulfonyl)imide (TFSI-) or bis(fluorosulfonyl)imide (FSI-) anions, were tested in combination with separators having different chemistries and morphologies in terms of wetting behavior, Gurley and McMullin number, as well as Li/(Separator + Electrolyte) interfacial properties. It is shown that non-functionalized microporous polyolefin separators are poorly wetted by FSI--based electrolytes (contrary to TFSI--based electrolytes), while the ceramic coated separator Separion® allows good wetting with all electrolytes. Furthermore, by comparing the lithium solid electrolyte interphase (SEI) resistance evolution at open circuit and during cycling, depending on separator morphologies and chemistries, it is possible to propose a scale for SEI forming properties in the order: PYR12O1FSI > PYR14FSI > PYR14TFSI > PYR12O1TFSI. Finally, the impact the separator morphology is evidenced by the SEI resistance evolution and by comparing Li electrodes cycled using separators with two different morphologies. [ABSTRACT FROM AUTHOR]

We report a new class of quaternary polymer electrolyte membranes that comprise poly(ethylene oxide) (PEO), lithium trifluoromethanesulfonylimide (LiTFSI), N-alkyl- N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PyrA,4TFSI) as an ionic liquid, and a SiO2 filler. The results of differential scanning calorimetry indicate that the addition of SiO2 and different ionic liquids induces a decrease in the PEO melting enthalpy, which thereby increases the ionic conductivity and the Li transference number. The electrochemical stability is proved by using impedance spectroscopy and cyclic voltammetry. Galvanostatic cycling of Li/LiFePO4 cells, which comprise the quaternary polymer electrolytes, revealed their superior performance compared to conventional PEO-Li salt electrolytes. In the course of this investigation, a synergistic effect of the combined ionic liquid-ceramic filler modification could be proved at temperatures close to 50 °C. [ABSTRACT FROM AUTHOR]

Dual-graphite cells have been proposed as electrochemical energy storage systems using graphite as both, the anode and cathode, whereas the electrolyte cations intercalate into the negative electrode and the electrolyte anions intercalate into the positive electrode during charge. On discharge, cations and anions are released back into the electrolyte. In this contribution, we present highly promising results for "dual-ion cells" based on intercalation of bis(trifluoromethanesulfonyl)imide anions into a graphite cathode from an ionic liquid-based electrolyte, namely N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI). As the compatibility of this ionic liquid with graphitic anodes is relatively poor, metallic lithium and lithium titanate (Li4Ti5O12) are used as anode. As both cations and anions participate in the charge/discharge reaction and other anode materials than graphite are possible, we propose the name "dual-ion cells" for these systems. The cell performance was studied in terms of cut-off voltage, temperature, cycling stability, self-discharge and rate performance. Depending on the cut-off voltage and temperature, coulombic efficiencies of more than 99 % and specific discharge capacities exceeding 100 mAh g -1(based on graphite cathode weight) were achieved. Furthermore, this system provides an excellent cycling stability and capacity retention above 99 % after 500 cycles, outperforming reported organic solvent-based dual-graphite or dual-ion cells. [ABSTRACT FROM AUTHOR]

The possibility to electrodeposit silicon directly on a copper current collector out of organic electrolyte and ionic liquid was investigated with the aim to alloy the deposited silicon with lithium to prove the possible use as negative electrode in lithium ion batteries. Cyclovoltammetric analyses have shown in comparison to electrodes containing high crystalline silicon similar behaviour during the electrochemical alloying and dealloying process. SEM analyses have shown a particle size of the deposited silicon in submicron range. [ABSTRACT FROM AUTHOR]

In this paper we report on the use of the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethansulfonyl)imide, PYR14TFSI, in combination with a graphite and silicon electrodes at room temperature. The performance of the investigated electrodes has been considered in terms of specific capacity, cycling efficiency and cycling stability. The influence of two different binders on the performance of graphite electrode has also been considered. The results show that in electrolytic solutions based on PYR14TFSI the addition of an electrolyte additive is necessary for the formation of the solid electrolyte interphase (SEI). The reported results show also that the selection of the binder is important for the increase of the performance in graphite electrodes. Finally, the comparison of the performance of the investigated electrodes showed that silicon electrodes display higher compatibility with PYR14TFSI with respect to graphite electrodes. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Herein, we report on the theoretical and experimental investigation of the chemical equilibrium in a Ethylammonium Nitrate (EAN)/1,4-Diaminobutane (DAB) binary mixture displaying a significant excess of the latter component (namely, a 1:9 mole ratio). Both the neutral compounds, i.e., ethylamine (EtNH2) and DAB, present very similar chemical properties, especially concerning their basic strength, resulting in a continuous jump of the proton from the ethylammonium to the diamine (and vice-versa). Due to the significant excess of DAB, the proton is (statistically) expected to be bound to one of its nitrogen atoms, leading to the formation of a new (ternary) mixture containing DAB (ca. 80%), ethylamine (ca. 10%) and 4-amino-1-butylammonium nitrate (ABAN, ca. 10%). This is probed by means of SAXS measurements, showing LqE (low q excess) that increases over time. This feature tends to stabilize after approximately one day. When the measurement is repeated after one year, the LqE feature shows an increased intensity. Based on the results of our simulations, we suggest that this phenomenon is likely due to partial ethylamine evaporation, pushing the equilibrium toward the formation of ABAN. [ABSTRACT FROM AUTHOR]

Li+-conducting polyethylene oxide-based membranes incorporating N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide are used as electrolyte separators for all-solid-state lithium polymer batteries operating at medium-high temperatures. The incorporation of the ionic liquid remarkably improves the thermal, ion-transport and interfacial properties of the polymer electrolyte, which, in combination with the wide electrochemical stability even at medium-high temperatures, allows high current rates without any appreciable lithium anode degradation. Battery tests carried out at 80 °C have shown excellent cycling performance and capacity retention, even at high rates, which are never tackled by ionic liquid-free polymer electrolytes. No dendrite growth onto the lithium metal anode was observed. [ABSTRACT FROM AUTHOR]

Back Cover: Quaternary polymer electrolytes, containing PEO, LiTFSI, ionic liquid and ceramic filler, show higher limiting current density, conductivity and improved cycling performance in lithium metal/solid polymer electrolyte/LiFePO4 cells with respect to ternary electrolytes with either ionic liquid or ceramic filler. Further details can be found in the article by V. Sharova, G.‐T. Kim, G. A. Giffin, A. Lex‐Balducci,* and S. Passerini* on page 1188. [ABSTRACT FROM AUTHOR]

Li Batteries: Safety, Long Life, and High Energy Safety and non ‐ flammability, as well as high energy content and long life, may be achieved by combining advanced lithium ‐ ion electrodes in ionic liquid electrolyte. Such an appealing lithium ‐ ion battery involves pyrrolidinium ‐ based IL, alloying anode and layered ‐ structure cathode. The energy storage system actually represents an ideal candidate for a safe employment in modern electronic devices and electric vehicles. For more details, see the Full Paper by S. Passerini, J. Hassoun et al. on page 6808 ff. [ABSTRACT FROM AUTHOR]

Go with the Flow: The need for better batteries has fueled research in high‐risk/high‐reward cell chemistries such as lithium/air. This technology has the potential to enable a new generation of electric vehicles that can travel long distances while keeping the dimensions of the battery pack reasonably small. Before Li/air batteries can make it onto the market though, several fundamental questions need to be addressed, such as the (electro)chemical stability of their components during cycling and the evaporation of the electrolyte (cell drying), which can expose the reactive lithium metal to the atmosphere. The authors have tried to address all of the above‐mentioned points by developing and scaling up a novel two‐phase Li/O2 flow battery. This device can operate under mild conditions thanks to the use of a non‐volatile ionic‐liquid‐based electrolyte, and its performance can be improved by raising the temperature up to 60 °C, without incurring any decomposition or cell drying. With the aid of an oxygen‐bubbling device, the flow cell design keeps the O2 concentration constant, thereby obviating diffusion‐related limitations, as well as ensuring that the whole cathode active area is effectively participating in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes. Moreover, the high mass loadings attained with the use of purpose‐designed mesoporous carbons helps achieve high areal capacities (up to 4.78 mAh cm‐2), which, together with the self‐contained configuration, make the Li/O2 flow cell an appealing configuration for automotive applications. More details can be found in the Full Paper by Grande et al. from Helmholtz Institute Ulm and several other institutes in Germany, Italy, and Spain on page 85 in Issue 1, 2016 (DOI: 10.1002/ente.201500247). [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]

A correction to the article "Safer Electrolytes for Lithium-Ion Batteries: State of the Art and Perspectives" by J. Kalhoff and colleagues which appeared in a 2015 issue of the journal is presented.