The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Enn Lust - One of the best experts on this subject based on the ideXlab platform.
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use of Organic esters as co solvents for electrical double layer capacitors with low temperature performance
Journal of Electroanalytical Chemistry, 2006Co-Authors: Alar Janes, Enn LustAbstract:The electrochemical characteristics of the electrical double layer capacitor (EDLC) single cell based on the nanoporous carbon electrode in 1 M (C2H5)3CH3NBF4 (TEMA) solution in various non-aqueous Organic Carbonate and Organic ester binary, ternary and quaternary solvent systems (ethylene Carbonate (EC), dimethyl Carbonate (DMC), ethyl methyl Carbonate (EMC), diethyl Carbonate (DEC), methyl formate (MF), methyl acetate (MA) and ethyl acetate (EA)) mixed in the x:y, x:y:z and x:y:z:f volume ratios, respectively) have been studied using the cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS) methods. The specific capacitance, phase angle, series and parallel resistance values dependent on the solvent system used have been calculated. The region of ideal polarisability of nanoporous carbon electrodes ΔE ⩾ 3.0 V for 1 M TEMA in various binary, ternary and quaternary non-aqueous solvent systems has been achieved. Specific conductivity values for 1 M TEMA solution in various Organic Carbonate – Organic ester based electrolytes have been obtained at −40 °C < T < 50 °C and compared with electrochemistry data.
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Organic Carbonate Organic ester based non aqueous electrolytes for electrical double layer capacitors
Electrochemistry Communications, 2005Co-Authors: Alar Janes, Enn LustAbstract:The electrical characteristics of the electrical double layer capacitors based on the nanoporous carbon|1 M triethylmethylammonium tetrafluoroborate in ethylene Carbonate mixed with dimethyl Carbonate, ethyl methyl Carbonate, diethyl Carbonate, methyl formate, methyl acetate and ethyl acetate in the 1:1 volume ratio have been studied using the cyclic voltammetry and the electrochemical impedance spectroscopy methods. The specific series and parallel capacitances, phase angle, time constant, series and parallel resistances dependent on the binary solvent system used have been established. The region of ideal polarisability of nanoporous carbon electrodes ΔE ⩾ 3.0 V for 1 M (C2H5)3CH3NBF4 in various binary non-aqueous solvent systems has been achieved. Specific conductivity values for 1 M TEMA solution in various Organic Carbonate-based electrolytes have been obtained at −40 °C < T < 50 °C and compared with the electrochemical data.
Andrea Balducci - One of the best experts on this subject based on the ideXlab platform.
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the influence of the electrochemical and thermal stability of mixtures of ionic liquid and Organic Carbonate on the performance of high power lithium ion batteries
Electrochimica Acta, 2013Co-Authors: Sebastian Menne, Rubensimon Kuhnel, Andrea BalducciAbstract:Abstract In this work we report on the use of 0.3 M LiTFSI in PC–PYR14TFSI (50:50 wt.%) as electrolyte in lithium-ion batteries (LIBs). Conductivity, viscosity and electrochemical stability of this electrolyte were investigated and compared with those of the electrolytes 1 M LiPF6 in PC and 0.3 M LiTFSI in PC. The thermal stability of these electrolytes at 60 °C was also investigated. LIBs containing LTO as anode and LFP as cathode were assembled and tested in the three electrolytes at room temperature and 60 °C. The results of these tests show that the use of 0.3 M LiTFSI in PC–PYR14TFSI (50:50 wt.%) allows the realization of LIBs able to deliver high capacity and to display high cycling stability at both temperatures.
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high voltage electrochemical double layer capacitor containing mixtures of ionic liquids and Organic Carbonate as electrolytes
Electrochemistry Communications, 2011Co-Authors: A Krause, Andrea BalducciAbstract:Abstract Using a mixture of PC/PYR 14 TFSI as electrolyte, EDLCs with an operative voltage of 3.5 V and ESR comparable with that of conventional electrolyte have been realized. The combination of high operative voltage and low ESR enable the realization of EDLCs with high energy and high power. Moreover, the use of PC/PYR 14 TFSI mixture also guarantees a remarkable cycling stability, as evidenced by a capacitance loss of only 5% after 100,000 cycles carried out at 3.5 V.
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mixtures of ionic liquid and Organic Carbonate as electrolyte with improved safety and performance for rechargeable lithium batteries
Electrochimica Acta, 2011Co-Authors: Rubensimon Kuhnel, Stefano Passerini, Martin Winter, Nils Bockenfeld, Andrea BalducciAbstract:Abstract In this paper we report the results of physical–chemical and electrochemical investigations performed on ternary mixtures of the room temperature ionic liquid (IL) N -butyl- N -methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 14 TFSI), propylene Carbonate (PC), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as electrolyte for lithium-ion batteries. The thermal stability, ionic conductivity, viscosity and electrochemical stability windows of all considered mixtures were investigated and compared with those of electrolytes based on the pure PYR 14 TFSI and PC. The mixtures were also used as electrolyte in combination with LiFePO 4 -based electrodes. The specific capacity and cycling stability of these systems were investigated at different C-rates, both at room temperature and 60 °C.
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mixtures of ionic liquid in combination with graphite electrodes the role of electrolyte additives and li salt
Meeting Abstracts, 2009Co-Authors: Simon F Lux, Stefano Passerini, Martin Winter, Martin Schmuck, Barbara Rupp, Wolfgang Kern, Giovanni Battista Appetecchi, Andrea BalducciAbstract:Presently, commercially available lithium-ion batteries use graphite based anodes in combination with Organic Carbonate (e.g. Propylene Carbonate, PC, Ethylene Carbonate, EC) electrolytes. In this kind of Li-ion batteries the solid electrolyte intephase (SEI) formation process on the surface of graphite is crucial since it strongly influence the performances of the batteries systems [1]. It is known that the use of electrolyte additives (e.g. containing vinylene groups) improves the design of the resulting SEI on the graphite and leads to more efficient cycling of the material [2]. For that, several types of additives have been already studied and tested and intense research is now focused on the optimization of their design for a more effective film-forming efficiency. Ionic Liquids (ILs), room temperature molten salts typically showing a very low vapor pressure, high thermal stability, wide electrochemical windows and good conductivity at room and sub-room temperatures [3-4]. These properties make them very attractive candidates for the use as electrolytes in electrochemical devices such as batteries, particularly to increase the safety and the operative temperature range. So far, different types of ILs have been already used in combination with graphite electrodes with promising results [5-7]. However, only few reports studied the SEI formation process on graphite electrodes when ILs are used in the electrolytes as well as the contribution of additives to the SEI formation in such electrlytes [8]. Recently, we investigated the role of the additive Vinylene Carbonate (VC) in ILs-based electrolyte. The results of our studies indicated that when ultrapure ILs are used as electrolytes in combination with graphite electrodes, the need of additives in the electrolyte solution is strictly related to the film-forming ability of the ILs [9] themselves. For instance, in electrolyte solution based on the ultrapure ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethansulfonyl)imide (PYR14TFSI) the use of VC appears to be indispensable because such IL does not display film-forming ability. To the contrary, in electrolyte solution based on the ultrapure N-methyl-Npropylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI) the presence of VC was not strictly required because this IL displays film-forming ability. In order to investigate the film-forming ability of PYR13FSI and the possibility of using this IL as additive or co-solvent in pure IL-based solutions, we prepare different mixture of PYR13FSI -PYR14TFSI with and without VC. These solutions have been used in combination with the graphite electrode and their influence on the specific capacity, the cycling efficiency and the cycling stability of the electrodes have been investigated. As example, Fig. 1 shows the cyclic voltammetry at 50 μV sec of graphite electrode in 0.3 M LiTFSI + PYR14TFSI + 5%wt. VC (A); 0.3 M LiTFSI + PYR14TFSI [50%] PYR13FSI [50%] + 5%wt. VC (B) and 0.3 M LiTFSI + PYR13FSI + 5%wt. VC (C). Also the influence of two different Lithium salt (Lithium bis(trifluoromethansulfonyl)imide, LiTFSI and Lithium exafluophosphate, LiPF6) on the performance of graphite electrode in the mixtures of PYR13FSI PYR14TFSI has been investigated. These studies clearly evidence that the Li-salt strongly influence the performance of graphite electrode in combination with ILs-based solutions.
Stefano Passerini - One of the best experts on this subject based on the ideXlab platform.
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safer electrolytes for lithium ion batteries state of the art and perspectives
Chemsuschem, 2015Co-Authors: Julian Kalhoff, Dominic Bresser, Gebrekidan Gebresilassie Eshetu, Stefano PasseriniAbstract: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. Language: en
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development of gas chromatographic methods for the analyses of Organic Carbonate based electrolytes
Journal of Power Sources, 2014Co-Authors: Lydia Terborg, Stefano Passerini, Martin Winter, Sascha Weber, Uwe Karst, Sascha NowakAbstract:Abstract In this work, novel methods based on gas chromatography (GC) for the investigation of common Organic Carbonate-based electrolyte systems are presented, which are used in lithium ion batteries. The methods were developed for flame ionization detection (FID), mass spectrometric detection (MS). Further, headspace (HS) sampling for the investigation of solid samples like electrodes is reported. Limits of detection are reported for FID. Finally, the developed methods were applied to the electrolyte system of commercially available lithium ion batteries as well as on in-house assembled cells.
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the mechanism of hf formation in lipf6 based Organic Carbonate electrolytes
Electrochemistry Communications, 2012Co-Authors: Stefano Passerini, Simon F Lux, Ivan T Lucas, Elam Pollak, Michael Winter, Robert KosteckiAbstract:The mechanism of HF formation in LiPF6-based Organic Carbonate electrolytes S.F. Lux 1,2 , I.T. Lucas 2 , E. Pollak 2 , S. Passerini 1 , M. Winter 1 and R. Kostecki 2 University of Munster, Institute of Physical Chemistry, MEET laboratories, Corrensstr. 46, 48149 Munster, Germany Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA ABSTRACT Spectroscopic ellipsometry was used to study the time-dependent formation of HF upon the thermal degradation of LiPF 6 at 50°C in a lithium ion battery electrolyte containing ethylene Carbonate and diethyl Carbonate. The generated HF was monitored by following the etching rate of a 300 nm thick SiO 2 layer, grown on both sides of a silicon wafer substrate, as a function of the immersion time in the electrolyte at 50°C. It was found that the formation of HF starts after 70 hours of exposure time and occurs following several different phases. The amount of generated HF was calculated using an empirical formula correlating the etching rate to the temperature. Combining the results of the HF formation with literature data, a simplified mechanism for the formation of the HF involving LiPF 6 degradation, and a simplified catalytical reaction pathway of the formed HF and silicon dioxide is proposed to describe the kinetics of HF formation. KEYWORDS Lithium ion batteries, hydrofluoric acid, spectroscopic ellipsometry, LiPF 6 degradation Corresponding authors: Corresponding author: Simon Franz Lux
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mixtures of ionic liquid and Organic Carbonate as electrolyte with improved safety and performance for rechargeable lithium batteries
Electrochimica Acta, 2011Co-Authors: Rubensimon Kuhnel, Stefano Passerini, Martin Winter, Nils Bockenfeld, Andrea BalducciAbstract:Abstract In this paper we report the results of physical–chemical and electrochemical investigations performed on ternary mixtures of the room temperature ionic liquid (IL) N -butyl- N -methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 14 TFSI), propylene Carbonate (PC), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as electrolyte for lithium-ion batteries. The thermal stability, ionic conductivity, viscosity and electrochemical stability windows of all considered mixtures were investigated and compared with those of electrolytes based on the pure PYR 14 TFSI and PC. The mixtures were also used as electrolyte in combination with LiFePO 4 -based electrodes. The specific capacity and cycling stability of these systems were investigated at different C-rates, both at room temperature and 60 °C.
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mixtures of ionic liquid in combination with graphite electrodes the role of electrolyte additives and li salt
Meeting Abstracts, 2009Co-Authors: Simon F Lux, Stefano Passerini, Martin Winter, Martin Schmuck, Barbara Rupp, Wolfgang Kern, Giovanni Battista Appetecchi, Andrea BalducciAbstract:Presently, commercially available lithium-ion batteries use graphite based anodes in combination with Organic Carbonate (e.g. Propylene Carbonate, PC, Ethylene Carbonate, EC) electrolytes. In this kind of Li-ion batteries the solid electrolyte intephase (SEI) formation process on the surface of graphite is crucial since it strongly influence the performances of the batteries systems [1]. It is known that the use of electrolyte additives (e.g. containing vinylene groups) improves the design of the resulting SEI on the graphite and leads to more efficient cycling of the material [2]. For that, several types of additives have been already studied and tested and intense research is now focused on the optimization of their design for a more effective film-forming efficiency. Ionic Liquids (ILs), room temperature molten salts typically showing a very low vapor pressure, high thermal stability, wide electrochemical windows and good conductivity at room and sub-room temperatures [3-4]. These properties make them very attractive candidates for the use as electrolytes in electrochemical devices such as batteries, particularly to increase the safety and the operative temperature range. So far, different types of ILs have been already used in combination with graphite electrodes with promising results [5-7]. However, only few reports studied the SEI formation process on graphite electrodes when ILs are used in the electrolytes as well as the contribution of additives to the SEI formation in such electrlytes [8]. Recently, we investigated the role of the additive Vinylene Carbonate (VC) in ILs-based electrolyte. The results of our studies indicated that when ultrapure ILs are used as electrolytes in combination with graphite electrodes, the need of additives in the electrolyte solution is strictly related to the film-forming ability of the ILs [9] themselves. For instance, in electrolyte solution based on the ultrapure ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethansulfonyl)imide (PYR14TFSI) the use of VC appears to be indispensable because such IL does not display film-forming ability. To the contrary, in electrolyte solution based on the ultrapure N-methyl-Npropylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI) the presence of VC was not strictly required because this IL displays film-forming ability. In order to investigate the film-forming ability of PYR13FSI and the possibility of using this IL as additive or co-solvent in pure IL-based solutions, we prepare different mixture of PYR13FSI -PYR14TFSI with and without VC. These solutions have been used in combination with the graphite electrode and their influence on the specific capacity, the cycling efficiency and the cycling stability of the electrodes have been investigated. As example, Fig. 1 shows the cyclic voltammetry at 50 μV sec of graphite electrode in 0.3 M LiTFSI + PYR14TFSI + 5%wt. VC (A); 0.3 M LiTFSI + PYR14TFSI [50%] PYR13FSI [50%] + 5%wt. VC (B) and 0.3 M LiTFSI + PYR13FSI + 5%wt. VC (C). Also the influence of two different Lithium salt (Lithium bis(trifluoromethansulfonyl)imide, LiTFSI and Lithium exafluophosphate, LiPF6) on the performance of graphite electrode in the mixtures of PYR13FSI PYR14TFSI has been investigated. These studies clearly evidence that the Li-salt strongly influence the performance of graphite electrode in combination with ILs-based solutions.
Robert Kostecki - One of the best experts on this subject based on the ideXlab platform.
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kerr gated raman spectroscopy of lipf6 salt and lipf6 based Organic Carbonate electrolyte for li ion batteries
Physical Chemistry Chemical Physics, 2019Co-Authors: Laura Cabofernandez, Robert Kostecki, Alex R Neale, Filipe Braga, Igor V Sazanovich, Laurence J HardwickAbstract:Fluorescent species are formed during cycling of lithium ion batteries as a result of electrolyte decomposition due to the instability of the non-aqueous electrolytes and side reactions that occur at the electrode surface. The increase in the background fluorescence due to the presence of these components makes it harder to analyse data due to the spectroscopic overlap of Raman scattering and fluorescence. Herein, Kerr gated Raman spectroscopy was shown to be an effective technique for the isolation of the scattering effect from the fluorescence enabling the collection of the Raman spectra of LiPF6 salt and LiPF6-based Organic Carbonate electrolyte, without the interference of the fluorescence component. Kerr gated Raman was able to identify POF3 on the LiPF6 particle surface, after the addition of trace water.
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interfacial side reactions at a lini0 5mn1 5o4 electrode in Organic Carbonate based electrolytes
Electrochemistry Communications, 2013Co-Authors: Nick S Norberg, Simon Franz Lux, Robert KosteckiAbstract:Abstract Interfacial side-reactions at a LiNi 0.5 Mn 1.5 O 4 spinel electrode in LiPF 6 /Organic Carbonate-based electrolyte were investigated using FTIR and fluorescence spectroscopy. In situ measurements at a carbon- and binder-free LiNi 0.5 Mn 1.5 O 4 electrode showed formation of fluorescent species that coincides with the oxidation of Ni II + in LiNi 0.5 Mn 1.5 O 4 . The majority of these electrolyte oxidation products diffuse away into the electrolyte but fluorescence images of cycled LiNi 0.5 Mn 1.5 O 4 composite electrodes also show fluorescent residues at the surface of the electrode. FTIR and Raman spectra of the surface layer indicate formation of metal-ion doped Organic and inOrganic compounds upon electrolyte oxidation at potentials above 4.2 V.
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the mechanism of hf formation in lipf6 based Organic Carbonate electrolytes
Electrochemistry Communications, 2012Co-Authors: Stefano Passerini, Simon F Lux, Ivan T Lucas, Elam Pollak, Michael Winter, Robert KosteckiAbstract:The mechanism of HF formation in LiPF6-based Organic Carbonate electrolytes S.F. Lux 1,2 , I.T. Lucas 2 , E. Pollak 2 , S. Passerini 1 , M. Winter 1 and R. Kostecki 2 University of Munster, Institute of Physical Chemistry, MEET laboratories, Corrensstr. 46, 48149 Munster, Germany Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA ABSTRACT Spectroscopic ellipsometry was used to study the time-dependent formation of HF upon the thermal degradation of LiPF 6 at 50°C in a lithium ion battery electrolyte containing ethylene Carbonate and diethyl Carbonate. The generated HF was monitored by following the etching rate of a 300 nm thick SiO 2 layer, grown on both sides of a silicon wafer substrate, as a function of the immersion time in the electrolyte at 50°C. It was found that the formation of HF starts after 70 hours of exposure time and occurs following several different phases. The amount of generated HF was calculated using an empirical formula correlating the etching rate to the temperature. Combining the results of the HF formation with literature data, a simplified mechanism for the formation of the HF involving LiPF 6 degradation, and a simplified catalytical reaction pathway of the formed HF and silicon dioxide is proposed to describe the kinetics of HF formation. KEYWORDS Lithium ion batteries, hydrofluoric acid, spectroscopic ellipsometry, LiPF 6 degradation Corresponding authors: Corresponding author: Simon Franz Lux
Martin Winter - One of the best experts on this subject based on the ideXlab platform.
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tetrahydrothiophene 1 oxide as highly effective co solvent for propylene Carbonate based electrolytes
Journal of Power Sources, 2019Co-Authors: Kristina Oldiges, Julian Michalowsky, Mariano Grunebaum, Natascha Von Aspern, Isidora Cekiclaskovic, Jens Smiatek, Martin WinterAbstract:Abstract Propylene Carbonate (PC) together with cyclic sulfur compounds such as tetrahydrothiophene 1-oxide (THT1oxide) as co-solvent and lithium hexafluorophosphate (LiPF6) as conducting salt are introduced as new aprotic liquid electrolytes for lithium-ion batteries. Starting with the single solvent electrolyte LiPF6 in PC, by addition of THT1oxide, the ion transport properties even at temperatures down to −20 °C are improved by the different solvation behavior of Li+ ions due to the high Li+ ion affinity of the sulfinyl (-S=O) group and by the resulting decrease of the Li+ ion complex size. Electrolytes that contain Li+ ion complexes with both PC and THT1oxide molecules in the solvation shell are able to form protective interphase layers on graphite and NCM111 (LiNi1/3Co1/3Mn1/3O2) electrodes that are both permeable for Li+ ions while ensuring good electronic insulation, thus enabling stable cycling in lithium-ion cells with only minor capacity fading. THT1oxide/PC-based electrolytes afford better long-term as well as low temperature cycling behavior compared to established state-of-the-art (SOTA) Organic Carbonate-based electrolytes. The obtained results allow for the design of new co-solvents for PC and comparable cyclic Organic Carbonates, and provide a non-toxic and cheap alternative to crown ethers without affecting the Li+ ion transference/transport numbers.
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a fluoride selective electrode fse for the quantification of fluoride in lithium ion battery lib electrolytes
Analytical Methods, 2016Co-Authors: Andrea Wilken, Vadim Kraft, Martin Winter, Sabrina Girod, Sascha NowakAbstract:In this work, a fluoride-selective electrode (FSE) was applied with regard to the analysis of fluoride in lithium hexafluorophosphate-based lithium-ion battery (LIB) electrolytes. The influence of linear Organic Carbonate solvents dimethyl Carbonate (DMC), ethyl methyl Carbonate (EMC) and diethyl Carbonate (DEC) which are used as co-solvents in battery electrolytes was investigated. The developed FSE method for the analysis of battery electrolytes was comprehensively validated in view of the (1) trueness and recovery rates (nominal vs. actual comparison; influence of different amounts of electrolytes on the performance of the electrode; recovery rates of defined differences in concentration), (2) precision (intra-day precision and inter-day precision), (3) selectivity (influence of the Carbonate solvents on different fluoride concentrations; interferents) and (4) linearity and range. Statistical analysis was performed to evaluate the data and to characterize the reproducibility of the method. The determination of the commercially available LP30 (1 mol LiPF6 and ethylene Carbonate/dimethyl Carbonate (EC : DMC, 50 : 50 wt%)) electrolyte stored over 47 days and at 80 °C, by the FSE technique was compared to the fluoride analysis by ion chromatography (IC). While interferences in the IC method resulted in false-high concentrations, the FSE operated free from interferences, selective and specific. The validation of the method was successfully carried out and enables new areas of application.
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Ion and gas chromatography mass spectrometry investigations of organophosphates in lithium ion battery electrolytes by electrochemical aging at elevated cathode potentials
Journal of Power Sources, 2016Co-Authors: Waldemar Weber, Vadim Kraft, Benjamin Streipert, Ralf Wagner, Martin Winter, Sascha NowakAbstract:The electrochemical aging of commercial non-aqueous lithium hexafluorophosphate (LiPF6)/Organic Carbonate solvent based lithium ion battery electrolyte has been investigated in view of the formation of ionic and non-ionic alkylated phosphates. Subject was a solvent mixture of ethylene Carbonate/ethyl methyl Carbonate EC:EMC (1:1, by wt.) with 1 M LiPF6(LP50 Selectilyte™, BASF). The analysis was carried out by ion chromatography coupled with electrospray ionization mass spectrometry (ESI-MS) for ionic compounds and (headspace) gas chromatography mass spectrometry ((HS)-GC-MS) for non-ionic compounds. The electrochemical aging was performed by galvanostatic charge/discharge cycling and potentiostatic experiments with LiNi0.5Mn1.5O4(LMNO) as cathode material at increased cut-off potentials (>4.5 V vs. Li/Li+). A strong dependence of the formation of organophosphates on the applied electrode potential was observed and investigated by quantitative analysis of the formed phosphates. In addition, new possible "fingerprint" compounds for describing the electrolyte status were investigated and compared to existing compounds.
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development of gas chromatographic methods for the analyses of Organic Carbonate based electrolytes
Journal of Power Sources, 2014Co-Authors: Lydia Terborg, Stefano Passerini, Martin Winter, Sascha Weber, Uwe Karst, Sascha NowakAbstract:Abstract In this work, novel methods based on gas chromatography (GC) for the investigation of common Organic Carbonate-based electrolyte systems are presented, which are used in lithium ion batteries. The methods were developed for flame ionization detection (FID), mass spectrometric detection (MS). Further, headspace (HS) sampling for the investigation of solid samples like electrodes is reported. Limits of detection are reported for FID. Finally, the developed methods were applied to the electrolyte system of commercially available lithium ion batteries as well as on in-house assembled cells.
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mixtures of ionic liquid and Organic Carbonate as electrolyte with improved safety and performance for rechargeable lithium batteries
Electrochimica Acta, 2011Co-Authors: Rubensimon Kuhnel, Stefano Passerini, Martin Winter, Nils Bockenfeld, Andrea BalducciAbstract:Abstract In this paper we report the results of physical–chemical and electrochemical investigations performed on ternary mixtures of the room temperature ionic liquid (IL) N -butyl- N -methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 14 TFSI), propylene Carbonate (PC), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as electrolyte for lithium-ion batteries. The thermal stability, ionic conductivity, viscosity and electrochemical stability windows of all considered mixtures were investigated and compared with those of electrolytes based on the pure PYR 14 TFSI and PC. The mixtures were also used as electrolyte in combination with LiFePO 4 -based electrodes. The specific capacity and cycling stability of these systems were investigated at different C-rates, both at room temperature and 60 °C.