Targeting adequate thermal stability and fire safety in selecting ionic liquid-based electrolytes for energy storage

CAPLUS AN 2014:16740(Journal; Online Computer File)International audienceThe energy storage market relating to lithium based systems regularly grows in size and expands in terms of a portfolio of energy and power demanding applications. Thus safety focused research must more than ever accompany related technological breakthroughs regarding performance of cells, resulting in intensive research on the chemistry and materials science to design more reliable batteries. Formulating electrolyte solutions with nonvolatile and hardly flammable ionic liquids instead of actual carbonate mixtures could be safer. However, few definitions of thermal stability of electrolytes based on ionic liquids have been reported in the case of abuse conditions (fire, shortcut, overcharge or overdischarge). This work investigates thermal stability up to combustion of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C1C4Im][NTf2]) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([PYR14][NTf2]) ionic liquids, and their corresponding electrolytes containing lithium bis(trifluoromethanesulfonyl)imide LiNTf2. Their possible routes of degradation during thermal abuse testings were investigated by thermodynamic studies under several experimental conditions. Their behaviours under fire were also tested, including the analysis of emitted compounds

Determination of an implantation area for interstitial fluid extraction in cows and feasibility of adapted microneedles

International audienceWe present a preliminary study of a wearable system to monitor biomarkers for dairy and suckling cattle. Finding the optimal location on the cow body (ears) and designing the adapted microneedles to reach the interstitial fluids underneath the cow skin are the two points addressed here.For the selection of the location, 4 breeds of suckling cows (Aubrac, Charolaise, Lim-ousine, Salers) and 3 breeds of dairy cows (Abondance, Montbe ⠁liarde, Holstein) were chosen. Measurements of the thickness of the ear tissues were conducted on three areas of the ear (top, apex and base of the pinna), on the external and internal sides. Results show that the apex of the pinna, external side, is the best area for microneedle implantation with an implantation window of 1403 +/- 589 mm (DeepDe), considering all breeds. To reach this implantation window located between the stratum corneum and the cartilage, the microneedle has to pass through 1323 +/- 404 mm of tissues (SupDe), considering all breeds. From these results, a microneedle design was made on SolidWorks. With a conical shape 2.89 mm in height and a conical channel 300 mm in diameter (at the tip of the microneedle), the model was made using 3D printing. The resulting microneedles respect the SolidWorks design with fair accuracy. They were connected to a microfluidic channel for sampling or releasing fluids

Ionic liquids for energy storage applications, imidazolium or pyrrolidinium ?

Due to environmental and energy concerns, batteries for electric vehicles are highly studied and developed. Previously they were based on Lead, Nickel-Cadmium and Nickel metal hydride technologies, but at the present Li-ion are considered more efficient in energy density. Unfortunately, these batteries use carbonated solvents as electrolytes which lead to safety issues because of their high tlammability and low flash points. The replacement of these electrolytes by ionie liquids (ILs) is now widely considered as they have low vapour pressure and high flash point. They are also good ionie conductors, and present wide electrochemical window and high decomposition temperature (Td). But little information is available on their behaviour under abusive conditions like car crashes or any abnormal use (shortcut, overheat). In order to begin the understanding of the possible degradation of Ils du ring abusive tests a thermodynamic study of these compounds was carried out. A first approach is a criticalliterature study of the Td determined by thermogravimetric analysis (TGA). This study lead to the definition of adapted experimental parameters, and consequent experiments highlighted the stability of the NTf2 anion combined with two cation families: imidazolium and pyrrolidinium. Several trends were subsequently obtained, depending on the anion, the alkyl chain length, the functionalities and the c2-H substitution. But TGA does not give information on the nature of volatile emissions, so the comparison between c1c4ImNTf2 and PYR14 NTf2 with in situ and ex situ techniques has been carried out. Diffuse reflectance infra red spectroscopy associated with gas chromatography and mass spectroscopy was used to determine the decomposition products after two hours heating at 250 and 350°C. The flammability and heat of combustion will also be reported. The second part of the work is dedicated to the electrochemical stability of c1 c4 ImNTf2 and PYR14 NTf2, in the presence of lithium salt LiNTf2 and electrodes (Li4 Ti5o12 and LiNixMnxCox02, x=0.33). Cycling tests are performed on specifie designed cells to allow the in operando analysis of the emitted gases by mass spectrometry

Fabrication of modern lithium ion batteries by 3D inkjet printing: opportunities and challenges

International audienc

Ionic liquid-based electrolytes for lithium-ion batteries: review of performances of various electrode systems

CAPLUS AN 2015:1834179(Journal; General Review; Online Computer File)A review. Lithium-ion cells based on Graphite/LiFePO4 (Cgr/LFP), Li4Ti5O12/LiFePO4 (LTO/LFP) and Li4Ti5O12/LiNi1/3Mn1/3Co1/3O2 (LTO/NMC), using [C1CnIm][NTf2]- and [C1C1CnIm][NTf2] (n = 4 and 6)-based electrolytes with different lithium salts such as Li[N(SO2CF3)2] (LiNTf2), Li[N(SO2F)2] (LiFSI) and LiPF6 were tested at 333 K and compared to a com. carbonate-based electrolyte [EC:DEC][LiPF6]. The impact of different factors such as length of side-alkyl chain on imidazolium ring or its C2-H substitution with CH3 group was studied, and the influence of the presence of org. additives as well as the value of the nominal voltage of the systems, was also reported. Finally, common trends for all these IL-based electrolyte systems were discussed. [on SciFinder(R)

Thermal stability and fire safety of ionic liquid-based electrolytes for lithium-ion batteries

Due to environmental and energy concerns, batteries for electric vehicles are highly studied and developed. They are mainly based on lithium-ion technology, considered more efficient in energy density. Carbonate mixtures used as electrolyte solvents could lead to safety issues due to their high flammability and low flash points. Formulating electrolyte solutions with nonvolatile and nonflammable ionic liquids (ILs) instead of carbonate mixtures could be safer as they have low vapour pressure and high flash point. Moreover, they are good ionic conductors, present wide electrochemical window and high decomposition temperature (Td). But little information is available on their behaviour under abuse conditions like car crashes or any abnormal use (shortcut, overheat). In order to understand the possible decomposition mechanisms of ILs and their mixture with lithium salt during abuse tests, a thermodynamic study of these compounds was carried out. A critical literature study of the Td determined by thermogravimetric analysis (TGA) and consequent experiments highlighted the stability of the NTf2 anion combined with two cationic families: imidazolium and pyrrolidinium. We chose 1-butyl-3-methylimidazolium [C1C4Im] and 1-butyl-1-methylpyrrolidinium [PYR14] cations, bis(trifluoromethanesulfonyl)imide [NTf2] anion. The electrolytes were composed of their mixture with 1 mol.L-1 of LiNTf2 andreferred to as [C1C4Im][Li][NTf2]and [PYR14][Li][NTf2]. Nevertheless, TGA does not give sufficient information on the nature of volatile emissions, so the thermal decomposition of [C1C4Im][NTf2] and [PYR14][NTf2] and their corresponding electrolytes was studied. Long term experiments with different techniques (2 to 15 h at 350°C) showed the highest stability of imidazolium-based solutions (Figure 1). For both families, the volatile decomposition products were mainly identified as butene isomers. Recombined alkyl cations (e.g. C1Im, C4Im, C4C4Im and C1C1Im) were detected in the residual liquid phases, implying that a degradation with no mass loss occurred. Figure 1: Long term stability test by TGA of IL-based electrolytes, neat ILs and lithium salt at 350 °C for 15 h Flammability and heat of combustion were studied with a fire propagation apparatus. The solutions were found very weakly combustible, and LiNTf2 showed a flame retardant effect. Flammable gases were emitted due to cation decomposition, and the anion decomposition formed toxic effluents. Figure 2: Heat release rate profiles of neat ILs and corresponding electrolytes showing good resistance to ignition ( ca.5 min) Then the electrolytes [C1C4Im][Li][NTf2]and [PYR14][Li][NTf2] were used in batteries constituted of Li4Ti5O12 and LiNi1/3Co1/3Mn1/3O2 electrodes. The cells were submitted to abuse tests such as shortcut or overcharge. A specific setup coupled with a mass spectrometer was developed to analyse in situ the gaseous emissions. All these points will be developed during the communication

Are ionic liquid-based electrolytes so safe ?

Due to environmental and energy concerns, batteries for electric vehicles are highly studied and developed. They are mainly based on lithium-ion technology, considered more efficient in terms of energy density. But carbonate mixtures used as electrolyte solvents could lead to safety issues, due to their high flammability and low flash points. Formulating electrolytes with negligible volatility and reduced flammability such as ionic liquids (ILs) could be safer. Ionic liquids have low vapour pressure, high flash point, wide electrochemical window, good ionic conductivity and high decomposition temperature (Td). But little information is available on their behaviour under abuse conditions, such as car crashes or any abnormal use (shortcut, overheat). From the literature, imidazolium and pyrrolidinium cations associated to bis(trifluoromethanesulfonyl)imide anion [NTf 2] display the highest thermal stability (Figure 1, left) and the best performances as electrolyte solvents for lithium-ion batteries. We investigated through several techniques (dynamic and long term TGA, …) the thermal decomposition of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C1C4Im][NTf2], 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide [PYR14][NTf2] and their corresponding lithium ion conductive electrolyte solutions, resulting from their mixture with 1 mol.L-1 of LiNTf2 ([C1C4Im][Li][NTf2] and [PYR14][Li][NTf2] respectively). Long term experiments (2 to 15 h at 350°C) revealed the highest thermal stability for imidazolium-based solutions. For both families, the major volatile decomposition products were identified as butene isomers. Recombined alkyl cations (e.g. C1Im, C4Im, C4C4Im and C1C1Im) were detected in the residual liquid phases, implying no mass loss during degradation. Flammability and heat of combustion were studied with a fire propagation apparatus (ISO12136). The solutions were found very weakly combustible (Figure 1, right), and LiNTf2 showed a flame retardant effect in the case of [PYR14][Li] [NTf2]. Flammable gases were emitted due to cation decomposition, while toxic effluents result from the anion decomposition. [C1C4Im][Li][NTf2],[PYR14][Li][NTf2] and commercial carbonates were used as electrolytes in the batteries (coin cells and pouch cells), with Li4Ti5O12 and LiNi1/3Co1/3Mn1/3O2as negative and positive electrodes respectively. Batteries were submitted to cycling and overcharge. After any experiment, the gaseous phases of the batteries were analysed with a specific setup coupled with a mass spectrometer

Erratum: PtxCoy Catalysts Degradation in PEFC Environments: Mechanistic Insights II. Preparation and Characterization of Particles with Homogeneous Composition [J. Electrochem. Soc., 157, B943 (2010)]

International audienc

Complementary Ion Beam Analysis and Raman Studies for Investigation of the Carbon Coating Impact on Li Insertion/Deinsertion Process at LiFePO4_4/C Electrodes

International audienceElectrode materials were prepared using two commercial C-LiFePO$_4$ powders (called hereafter LFP-A and LFP-B). The nature and the thickness of carbon coating have been characterized by Raman spectroscopy and Transmission Electron Microscopy. The carbon coating of the LFP-B is more graphitized than LFP-A, which appears amorphous. The lithium distribution of these electrodes is investigated using ion beam techniques as a function of its state of charge (SOC). The nuclear microanalyses reveal the presence of different dopings in the active materials (Ti or V). A layer richer in carbon (in addition to the composite electrode) is systematically observed on LFP-A pristine and cycled electrodes. In both materials, immobilization of lithium is visible. Higher content of lithium was observed for the LFP-B electrode

Transient Multi-Scale Modeling of PtxCoy Catalysts Degradation in PEFC Environments

International audienceIn this paper we focus on the understanding of the PtxCoy catalysts degradation in PEFC environments. A multiscale atomistic/kinetic model is derived providing new mechanistic insights on the impact of clusters nanostructure and operating conditions on PtxCoy materials durability. On the basis of ab initio (AI) data, we identify favorable pathways of the ORR on PtxCoy clusters and of the competitive Pt-Co dissolution in acidic media. The derived AI-kinetics is coupled to a description of the atomic reorganisation at the cluster level as function of the cumulated Pt and Co mass losses. This interfacial model is coupled with a transport microscale model of charges and O2 through the PEFC cathode, and simulation sensitivity studies to operating conditions and initial compositions/morphologies are performed. Experiments on DLIMOCVD-elaborated model electrodes are carried out by using RDE and half-cells: degradation structural changes are characterized by using TEM, XRD and XPS complementing the modeling studies