Valentina Borgel - Academia.edu (original) (raw)
Papers by Valentina Borgel
Journal of Power Sources, Apr 1, 2012
Micro-probe Raman spectroscopy investigation of LiCoPO 4 composite electrodes performed after pro... more Micro-probe Raman spectroscopy investigation of LiCoPO 4 composite electrodes performed after prolonged cycling in LiPF 6 EC/DMC electrolyte solution revealed total structural degradation of the olivine structure of the electrodes. The electrodes cycled in the identical conditions but in the presence of the HF-scavenging glassy fiber (GF) separators retain their olivine structure unchanged. The reasons for this pronounced difference are discussed.
Electrochemistry Communications, Aug 1, 2011
The improved cycling performance of a LiCoPO 4 cathode was observed in a 1 M LiPF 6 ethylene carb... more The improved cycling performance of a LiCoPO 4 cathode was observed in a 1 M LiPF 6 ethylene carbonate (EC)/ dimethyl carbonate (DMC) solution in LiCoPO 4 /Li cells with quartz separators. The reasons for the fast capacity fading of these cells with the ordinary polyethylene (PE) separators are discussed.
Journal of Power Sources, Aug 1, 2011
ABSTRACT The effect of laser power on the Raman spectra of two carbon-coated nano-powders of LiCo... more ABSTRACT The effect of laser power on the Raman spectra of two carbon-coated nano-powders of LiCoPO4 and LiFePO4 olivine cathode materials were investigated. In the ambient atmosphere at a moderate laser power, the phenomenon of the removal of the carbon coating layer from both samples was detected. The olivine structure of LiCoPO4-C powder therefore remains unchanged during the prolonged exposure to a 4.3 mW laser beam. The mild removal of the carbon layer makes it possible to analyze the details of the LiCoPO4 structure in air without interference from carbon.LiFePO4-C powder, together with carbon layer gasification, undergoes oxidative decomposition by the oxygen with the formation of Li3Fe2(PO4)3 and Fe2O3, even at a laser power of 1 mW. Thus, care should be taken when measuring and interpreting the Raman spectra of this material both in air and in an inert atmosphere, as obvious decomposition of the LiFePO4 olivine structure takes place even at a moderate power of the excitation laser.A comparative study of the stability of these two carbon-coated nano powders under laser beam irradiation and heating was carried out with the use of TGA-mass spectrometry.
Journal of The Electrochemical Society, 2014
ACS Applied Materials & Interfaces, Jan 12, 2016
The electrochemical behavior of Na-ion and Li-ion full cells was investigated, using hard carbon ... more The electrochemical behavior of Na-ion and Li-ion full cells was investigated, using hard carbon as the anode material, and NaNi0.5Mn0.5O2 and LiNi0.5Mn0.5O2 as the cathodes. A detailed description of the structure, phase transition, electrochemical behavior and kinetics of the NaNi0.5Mn0.5O2 cathodes is presented, including interesting comparison with their lithium analogue. The critical effect of the hard carbon anodes pretreatment in the total capacity and stability of full cells is clearly demonstrated. Using impedance spectroscopy in three electrodes cells, we show that the full cell impedance is dominated by the contribution of the cathode side. We discuss possible reasons for capacity fading of these systems, its connection to the cathode structure and relevant surface phenomena.
Advanced Energy Materials, Sep 22, 2015
Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is... more Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is proven to be a surprisingly unique, multifunctional binder for high‐voltage Li‐ion batteries. The absence of effective passivation at the interface of high‐voltage cathodes in Li‐ion batteries may negatively affect their electrochemical performance, due to detrimental phenomena such as electrolyte solution oxidation and dissolution of transition metal cations. A strategy is introduced to build a stable cathode–electrolyte solution interphase for LiNi0.5Mn1.5O4 (LNMO) spinel high‐voltage cathodes during the electrode fabrication process by simply using LiPAA as the cathode binder. LiPAA is a superb binder due to unique adhesion, cohesion, and wetting properties. It forms a uniform thin passivating film on LNMO and conducting carbon particles in composite cathodes and also compensates Li‐ion loss in full Li‐ion batteries by acting as an extra Li source. It is shown that these positive roles of LiPAA lead to a significant improvement in the electrochemical performance (e.g., cycle life, cell impedance, and rate capability) of LNMO/graphite battery prototypes, compared with that obtained using traditional polyvinylidene fluoride (PVdF) binder for LNMO cathodes. In addition, replacing PVdF with LiPAA binder for LNMO cathodes offers better adhesion, lower cost, and clear environmental advantages.
Israel Journal of Chemistry, Nov 1, 2015
Electrochemical and Solid State Letters, 2010
ABSTRACT We developed a methodology of in situ Fourier transform infrared (FTIR) measurements of ... more ABSTRACT We developed a methodology of in situ Fourier transform infrared (FTIR) measurements of gaseous products formed in an electrochemical cell upon polarization. LiNi0.8Co0.15Al0.05O2 (NCA) cathodes were explored at potentials of up to 5.5 V vs Li in the ionic liquid (IL)-based electrolyte solution, LiTFSI/N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) amide. The polarization of the NCA electrodes formed CO2 and CO due to the liberation of oxygen and the parallel dissolution of nickel ions, which oxidizes the carbon black in the composite electrode. The oxygen was mostly liberated from the NCA and also due to minor contribution from the surface groups on the carbon black additive.
Electrochimica Acta, Mar 1, 2010
In this work we analyzed the cathodic reactions of an important ionic liquid (IL) based electroly... more In this work we analyzed the cathodic reactions of an important ionic liquid (IL) based electrolyte solution, namely lithium bis(trifluoromethylsulfonyl)imide (LiTFSI)/N-methyl-N-methylpyrrolidinium (BMP) TFSI. In situ FTIR spectroscopy was used for the analysis of gaseous products of the electrochemical decomposition of this IL solution during cathodic polarization of lithium metal and graphite electrodes. The main volatile product of the reductive decomposition of the anion in these BMPTFSI solutions is trifluoromethane. BMP cations decompose to mixtures of tertiary amines and hydrocarbons. The composition of the products is influenced by the nature of the anode material. Graphite possesses a catalytic activity in the electroreduction process of BMP cations which occurs along with their intercalation into the graphite structure. The liquid phase after cathodic polarization of graphite electrodes was analyzed by multinuclear NMR spectroscopy coupled with FTIR spectroscopy. 15 N NMR and FTIR spectra revealed an increase in the Li cations content in the electrolyte solution, as a result of BMP cations decomposition during repeated cycling of graphite electrodes.
ECS Meeting Abstracts, 2010
ECS Meeting Abstracts, 2010
Ionic liquids become more and more important in electrochemistry. There is high incentive to intr... more Ionic liquids become more and more important in electrochemistry. There is high incentive to introduce them to Li ion batteries, because of their wide electrochemical window and apparent promising safety features. However, the limiting anodic & cathodic reactions of important ILs are still not clear at all. In this work, we explored the limiting cathodic reactions of an important IL. We analyzed gaseous decomposition products of LiTFSI/BMPTFSI electrolyte solutions by in situ FTIR measurements during cathodic polarization of Li metal and graphite electrodes. The electrochemical polarization of the electrodes was conducted while the electrochemical cell was connected to an optical FTIR gas measurements cell. The final spectra of the gaseous phase of Li/Li cell and graphite/Li cell, collected after the polarization procedures, are shown in Fig. 1. As is seen, the main volatile product of the reductive decomposition of the anion in these BMPTFSI solutions is trifluoromethane (CHF3). BMP cations decompose to mixtures of tertiary amines and hydrocarbons. The dynamics of accumulation of the main products in the gaseous phase of the graphite/Li cell during a CV cycle is shown in Fig. 2. It is seen that the formation of trifluoromethane, methane and tertiary amines starts immediately at the beginning of the experiments (and the in situ measurements of the FTIR spectra). This is explained by the fact that all of these products can be caused by the decomposition of the components of the electrolyte solution on the Li metal electrode, which serves as the counter electrode in all the experiments carried out herein. (See the inserts in Figs. 2a and b). In contrast, the accumulation of ethylene in the Li/graphite cells starts only after the beginning of the intercalation of the BMP cations into the graphite structure, below about 0.8V vs. Li/Li (see insert in Fig. 9b, black line). These observations indicate that the graphene sheets of graphite possess catalytic activity in the electroreduction process of BMP cations. The following reaction path can be proposed: Fig.1. FTIR spectra of the gaseous phase above the Li/Li and the graphite/Li cells. The low frequency NC-H stretching bands of the tertiary amines are indicated with asterisks. The bands of CHF3 are indicated with dots. 4000 300
Journal of The Electrochemical Society, 2014
ABSTRACT Investigation of the failure mechanisms of Li-ion batteries and the consequences of thei... more ABSTRACT Investigation of the failure mechanisms of Li-ion batteries and the consequences of their failure is of vital importance to the design of durable batteries. In this work, we examined the electrochemical performance of half and full Li-ion battery cells with several cathode materials including LiMn0.8Fe0.2PO4 (LMFP), LiNi0.5Mn1.5O4 (LMNO), and Li[LixNiyCozMn1−x−y−z]O2 Li-rich layered oxides (HC-MNC). In contrast to half cells which demonstrated good cycling performance with more than 90% of their initial capacities retained after 100 cycles, the full cells exhibited severe capacity loss. Based on postmortem analyzes of electrodes from cells cycled at 30 and 60◦C, using electrochemical, spectroscopic, and microscopic techniques, we conclude that the loss of active lithium ions due to parasitic side reactions is a main reason for capacity fading of Li-ion battery full cells. Structural degradation of the electrodes during cycling is at best a second order effect.
ACS applied materials & interfaces, Jan 27, 2016
The electrochemical behavior of Na-ion and Li-ion full cells was investigated, using hard carbon ... more The electrochemical behavior of Na-ion and Li-ion full cells was investigated, using hard carbon as the anode material, and NaNi0.5Mn0.5O2 and LiNi0.5Mn0.5O2 as the cathodes. A detailed description of the structure, phase transition, electrochemical behavior and kinetics of the NaNi0.5Mn0.5O2 cathodes is presented, including interesting comparison with their lithium analogue. The critical effect of the hard carbon anodes pretreatment in the total capacity and stability of full cells is clearly demonstrated. Using impedance spectroscopy in three electrodes cells, we show that the full cell impedance is dominated by the contribution of the cathode side. We discuss possible reasons for capacity fading of these systems, its connection to the cathode structure and relevant surface phenomena.
Israel Journal of Chemistry, 2015
Journal of The Electrochemical Society, 2014
Advanced Energy Materials, 2015
Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is... more Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is proven to be a surprisingly unique, multifunctional binder for high‐voltage Li‐ion batteries. The absence of effective passivation at the interface of high‐voltage cathodes in Li‐ion batteries may negatively affect their electrochemical performance, due to detrimental phenomena such as electrolyte solution oxidation and dissolution of transition metal cations. A strategy is introduced to build a stable cathode–electrolyte solution interphase for LiNi0.5Mn1.5O4 (LNMO) spinel high‐voltage cathodes during the electrode fabrication process by simply using LiPAA as the cathode binder. LiPAA is a superb binder due to unique adhesion, cohesion, and wetting properties. It forms a uniform thin passivating film on LNMO and conducting carbon particles in composite cathodes and also compensates Li‐ion loss in full Li‐ion batteries by acting as an extra Li source. It is shown that these positive rol...
Journal of Power Sources, 2015
Decrease of average cell potential during cycling due to self-discharge of petroleum coke by para... more Decrease of average cell potential during cycling due to self-discharge of petroleum coke by parasitic oxidation products from LMNO Time / h Potential / V LMNO || Petroleum coke full cell (3.50 → 4.68 V) Petroleum coke potential vs. Li LMNO potential vs. Li Increase in average potential of LMNO (charge) Average full cell potential Increase in average potential of petroleum coke (charge) The role of parasitic reactions increases Petroleum coke in half-cell LMNO in half-cell Full LMNO|| Petroleum coke cell
Journal of Power Sources, 2012
Micro-probe Raman spectroscopy investigation of LiCoPO 4 composite electrodes performed after pro... more Micro-probe Raman spectroscopy investigation of LiCoPO 4 composite electrodes performed after prolonged cycling in LiPF 6 EC/DMC electrolyte solution revealed total structural degradation of the olivine structure of the electrodes. The electrodes cycled in the identical conditions but in the presence of the HF-scavenging glassy fiber (GF) separators retain their olivine structure unchanged. The reasons for this pronounced difference are discussed.
Journal of Power Sources, 2009
We examined the possible use of the following ionic liquids all having the same anion, bis(triflu... more We examined the possible use of the following ionic liquids all having the same anion, bis(trifluoromethylsulfonyl)imide (TFSI) and the following cations: 1-hexyl-3-methyl imidazolium (HMITFSI), 1-(2-methoxyethyl)-3-methyl imidazolium (MEMITFSI), N-ethyl-NN-dimethyl-2-methoxyethylammonium (EDMETFSI), 1-methyl-1-butylpyrrolidinium (BMPTFSI), and 1-methyl-1-propylpiperidinium (MPPpTFSI) solutions with LiTFSI (the source of Li ions), as electrolyte systems for 5 V, rechargeable battery systems with Li metal anodes and LiMn 1.5 Ni 0.5 O 4 spinel cathodes. Standard solution based on alkyl carbonates and LiPF 6 was examined in this respect for comparison. The ionic liquids (ILs) based on derivatives of piperidinium and pyrrolidinium demonstrate a very wide electrochemical window (up to 5.5 V) and they can be compatible with lithium metal anodes. At low potentials in the presence of Li ions in solutions (or on Li metal surfaces), TFSI anions are reduced to insoluble Li compounds which passivate Li, noble metal and graphite electrodes in the Li salt/IL solutions. The mechanism, kinetics and effectiveness of electrodes' passivation in these systems depend on the nature of both IL and electrode used. It was possible to demonstrate reversible behavior of Li/LiMn 1.5 Ni 0.5 O 4 cells (4.8 V) with solutions based on BMPTFSI and MPPpTFSI. Possible parasitic anodic reactions upon charging at the high potentials are much lower in the ILs than in standard solutions.
Journal of Power Sources, Apr 1, 2012
Micro-probe Raman spectroscopy investigation of LiCoPO 4 composite electrodes performed after pro... more Micro-probe Raman spectroscopy investigation of LiCoPO 4 composite electrodes performed after prolonged cycling in LiPF 6 EC/DMC electrolyte solution revealed total structural degradation of the olivine structure of the electrodes. The electrodes cycled in the identical conditions but in the presence of the HF-scavenging glassy fiber (GF) separators retain their olivine structure unchanged. The reasons for this pronounced difference are discussed.
Electrochemistry Communications, Aug 1, 2011
The improved cycling performance of a LiCoPO 4 cathode was observed in a 1 M LiPF 6 ethylene carb... more The improved cycling performance of a LiCoPO 4 cathode was observed in a 1 M LiPF 6 ethylene carbonate (EC)/ dimethyl carbonate (DMC) solution in LiCoPO 4 /Li cells with quartz separators. The reasons for the fast capacity fading of these cells with the ordinary polyethylene (PE) separators are discussed.
Journal of Power Sources, Aug 1, 2011
ABSTRACT The effect of laser power on the Raman spectra of two carbon-coated nano-powders of LiCo... more ABSTRACT The effect of laser power on the Raman spectra of two carbon-coated nano-powders of LiCoPO4 and LiFePO4 olivine cathode materials were investigated. In the ambient atmosphere at a moderate laser power, the phenomenon of the removal of the carbon coating layer from both samples was detected. The olivine structure of LiCoPO4-C powder therefore remains unchanged during the prolonged exposure to a 4.3 mW laser beam. The mild removal of the carbon layer makes it possible to analyze the details of the LiCoPO4 structure in air without interference from carbon.LiFePO4-C powder, together with carbon layer gasification, undergoes oxidative decomposition by the oxygen with the formation of Li3Fe2(PO4)3 and Fe2O3, even at a laser power of 1 mW. Thus, care should be taken when measuring and interpreting the Raman spectra of this material both in air and in an inert atmosphere, as obvious decomposition of the LiFePO4 olivine structure takes place even at a moderate power of the excitation laser.A comparative study of the stability of these two carbon-coated nano powders under laser beam irradiation and heating was carried out with the use of TGA-mass spectrometry.
Journal of The Electrochemical Society, 2014
ACS Applied Materials & Interfaces, Jan 12, 2016
The electrochemical behavior of Na-ion and Li-ion full cells was investigated, using hard carbon ... more The electrochemical behavior of Na-ion and Li-ion full cells was investigated, using hard carbon as the anode material, and NaNi0.5Mn0.5O2 and LiNi0.5Mn0.5O2 as the cathodes. A detailed description of the structure, phase transition, electrochemical behavior and kinetics of the NaNi0.5Mn0.5O2 cathodes is presented, including interesting comparison with their lithium analogue. The critical effect of the hard carbon anodes pretreatment in the total capacity and stability of full cells is clearly demonstrated. Using impedance spectroscopy in three electrodes cells, we show that the full cell impedance is dominated by the contribution of the cathode side. We discuss possible reasons for capacity fading of these systems, its connection to the cathode structure and relevant surface phenomena.
Advanced Energy Materials, Sep 22, 2015
Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is... more Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is proven to be a surprisingly unique, multifunctional binder for high‐voltage Li‐ion batteries. The absence of effective passivation at the interface of high‐voltage cathodes in Li‐ion batteries may negatively affect their electrochemical performance, due to detrimental phenomena such as electrolyte solution oxidation and dissolution of transition metal cations. A strategy is introduced to build a stable cathode–electrolyte solution interphase for LiNi0.5Mn1.5O4 (LNMO) spinel high‐voltage cathodes during the electrode fabrication process by simply using LiPAA as the cathode binder. LiPAA is a superb binder due to unique adhesion, cohesion, and wetting properties. It forms a uniform thin passivating film on LNMO and conducting carbon particles in composite cathodes and also compensates Li‐ion loss in full Li‐ion batteries by acting as an extra Li source. It is shown that these positive roles of LiPAA lead to a significant improvement in the electrochemical performance (e.g., cycle life, cell impedance, and rate capability) of LNMO/graphite battery prototypes, compared with that obtained using traditional polyvinylidene fluoride (PVdF) binder for LNMO cathodes. In addition, replacing PVdF with LiPAA binder for LNMO cathodes offers better adhesion, lower cost, and clear environmental advantages.
Israel Journal of Chemistry, Nov 1, 2015
Electrochemical and Solid State Letters, 2010
ABSTRACT We developed a methodology of in situ Fourier transform infrared (FTIR) measurements of ... more ABSTRACT We developed a methodology of in situ Fourier transform infrared (FTIR) measurements of gaseous products formed in an electrochemical cell upon polarization. LiNi0.8Co0.15Al0.05O2 (NCA) cathodes were explored at potentials of up to 5.5 V vs Li in the ionic liquid (IL)-based electrolyte solution, LiTFSI/N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) amide. The polarization of the NCA electrodes formed CO2 and CO due to the liberation of oxygen and the parallel dissolution of nickel ions, which oxidizes the carbon black in the composite electrode. The oxygen was mostly liberated from the NCA and also due to minor contribution from the surface groups on the carbon black additive.
Electrochimica Acta, Mar 1, 2010
In this work we analyzed the cathodic reactions of an important ionic liquid (IL) based electroly... more In this work we analyzed the cathodic reactions of an important ionic liquid (IL) based electrolyte solution, namely lithium bis(trifluoromethylsulfonyl)imide (LiTFSI)/N-methyl-N-methylpyrrolidinium (BMP) TFSI. In situ FTIR spectroscopy was used for the analysis of gaseous products of the electrochemical decomposition of this IL solution during cathodic polarization of lithium metal and graphite electrodes. The main volatile product of the reductive decomposition of the anion in these BMPTFSI solutions is trifluoromethane. BMP cations decompose to mixtures of tertiary amines and hydrocarbons. The composition of the products is influenced by the nature of the anode material. Graphite possesses a catalytic activity in the electroreduction process of BMP cations which occurs along with their intercalation into the graphite structure. The liquid phase after cathodic polarization of graphite electrodes was analyzed by multinuclear NMR spectroscopy coupled with FTIR spectroscopy. 15 N NMR and FTIR spectra revealed an increase in the Li cations content in the electrolyte solution, as a result of BMP cations decomposition during repeated cycling of graphite electrodes.
ECS Meeting Abstracts, 2010
ECS Meeting Abstracts, 2010
Ionic liquids become more and more important in electrochemistry. There is high incentive to intr... more Ionic liquids become more and more important in electrochemistry. There is high incentive to introduce them to Li ion batteries, because of their wide electrochemical window and apparent promising safety features. However, the limiting anodic & cathodic reactions of important ILs are still not clear at all. In this work, we explored the limiting cathodic reactions of an important IL. We analyzed gaseous decomposition products of LiTFSI/BMPTFSI electrolyte solutions by in situ FTIR measurements during cathodic polarization of Li metal and graphite electrodes. The electrochemical polarization of the electrodes was conducted while the electrochemical cell was connected to an optical FTIR gas measurements cell. The final spectra of the gaseous phase of Li/Li cell and graphite/Li cell, collected after the polarization procedures, are shown in Fig. 1. As is seen, the main volatile product of the reductive decomposition of the anion in these BMPTFSI solutions is trifluoromethane (CHF3). BMP cations decompose to mixtures of tertiary amines and hydrocarbons. The dynamics of accumulation of the main products in the gaseous phase of the graphite/Li cell during a CV cycle is shown in Fig. 2. It is seen that the formation of trifluoromethane, methane and tertiary amines starts immediately at the beginning of the experiments (and the in situ measurements of the FTIR spectra). This is explained by the fact that all of these products can be caused by the decomposition of the components of the electrolyte solution on the Li metal electrode, which serves as the counter electrode in all the experiments carried out herein. (See the inserts in Figs. 2a and b). In contrast, the accumulation of ethylene in the Li/graphite cells starts only after the beginning of the intercalation of the BMP cations into the graphite structure, below about 0.8V vs. Li/Li (see insert in Fig. 9b, black line). These observations indicate that the graphene sheets of graphite possess catalytic activity in the electroreduction process of BMP cations. The following reaction path can be proposed: Fig.1. FTIR spectra of the gaseous phase above the Li/Li and the graphite/Li cells. The low frequency NC-H stretching bands of the tertiary amines are indicated with asterisks. The bands of CHF3 are indicated with dots. 4000 300
Journal of The Electrochemical Society, 2014
ABSTRACT Investigation of the failure mechanisms of Li-ion batteries and the consequences of thei... more ABSTRACT Investigation of the failure mechanisms of Li-ion batteries and the consequences of their failure is of vital importance to the design of durable batteries. In this work, we examined the electrochemical performance of half and full Li-ion battery cells with several cathode materials including LiMn0.8Fe0.2PO4 (LMFP), LiNi0.5Mn1.5O4 (LMNO), and Li[LixNiyCozMn1−x−y−z]O2 Li-rich layered oxides (HC-MNC). In contrast to half cells which demonstrated good cycling performance with more than 90% of their initial capacities retained after 100 cycles, the full cells exhibited severe capacity loss. Based on postmortem analyzes of electrodes from cells cycled at 30 and 60◦C, using electrochemical, spectroscopic, and microscopic techniques, we conclude that the loss of active lithium ions due to parasitic side reactions is a main reason for capacity fading of Li-ion battery full cells. Structural degradation of the electrodes during cycling is at best a second order effect.
ACS applied materials & interfaces, Jan 27, 2016
The electrochemical behavior of Na-ion and Li-ion full cells was investigated, using hard carbon ... more The electrochemical behavior of Na-ion and Li-ion full cells was investigated, using hard carbon as the anode material, and NaNi0.5Mn0.5O2 and LiNi0.5Mn0.5O2 as the cathodes. A detailed description of the structure, phase transition, electrochemical behavior and kinetics of the NaNi0.5Mn0.5O2 cathodes is presented, including interesting comparison with their lithium analogue. The critical effect of the hard carbon anodes pretreatment in the total capacity and stability of full cells is clearly demonstrated. Using impedance spectroscopy in three electrodes cells, we show that the full cell impedance is dominated by the contribution of the cathode side. We discuss possible reasons for capacity fading of these systems, its connection to the cathode structure and relevant surface phenomena.
Israel Journal of Chemistry, 2015
Journal of The Electrochemical Society, 2014
Advanced Energy Materials, 2015
Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is... more Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is proven to be a surprisingly unique, multifunctional binder for high‐voltage Li‐ion batteries. The absence of effective passivation at the interface of high‐voltage cathodes in Li‐ion batteries may negatively affect their electrochemical performance, due to detrimental phenomena such as electrolyte solution oxidation and dissolution of transition metal cations. A strategy is introduced to build a stable cathode–electrolyte solution interphase for LiNi0.5Mn1.5O4 (LNMO) spinel high‐voltage cathodes during the electrode fabrication process by simply using LiPAA as the cathode binder. LiPAA is a superb binder due to unique adhesion, cohesion, and wetting properties. It forms a uniform thin passivating film on LNMO and conducting carbon particles in composite cathodes and also compensates Li‐ion loss in full Li‐ion batteries by acting as an extra Li source. It is shown that these positive rol...
Journal of Power Sources, 2015
Decrease of average cell potential during cycling due to self-discharge of petroleum coke by para... more Decrease of average cell potential during cycling due to self-discharge of petroleum coke by parasitic oxidation products from LMNO Time / h Potential / V LMNO || Petroleum coke full cell (3.50 → 4.68 V) Petroleum coke potential vs. Li LMNO potential vs. Li Increase in average potential of LMNO (charge) Average full cell potential Increase in average potential of petroleum coke (charge) The role of parasitic reactions increases Petroleum coke in half-cell LMNO in half-cell Full LMNO|| Petroleum coke cell
Journal of Power Sources, 2012
Micro-probe Raman spectroscopy investigation of LiCoPO 4 composite electrodes performed after pro... more Micro-probe Raman spectroscopy investigation of LiCoPO 4 composite electrodes performed after prolonged cycling in LiPF 6 EC/DMC electrolyte solution revealed total structural degradation of the olivine structure of the electrodes. The electrodes cycled in the identical conditions but in the presence of the HF-scavenging glassy fiber (GF) separators retain their olivine structure unchanged. The reasons for this pronounced difference are discussed.
Journal of Power Sources, 2009
We examined the possible use of the following ionic liquids all having the same anion, bis(triflu... more We examined the possible use of the following ionic liquids all having the same anion, bis(trifluoromethylsulfonyl)imide (TFSI) and the following cations: 1-hexyl-3-methyl imidazolium (HMITFSI), 1-(2-methoxyethyl)-3-methyl imidazolium (MEMITFSI), N-ethyl-NN-dimethyl-2-methoxyethylammonium (EDMETFSI), 1-methyl-1-butylpyrrolidinium (BMPTFSI), and 1-methyl-1-propylpiperidinium (MPPpTFSI) solutions with LiTFSI (the source of Li ions), as electrolyte systems for 5 V, rechargeable battery systems with Li metal anodes and LiMn 1.5 Ni 0.5 O 4 spinel cathodes. Standard solution based on alkyl carbonates and LiPF 6 was examined in this respect for comparison. The ionic liquids (ILs) based on derivatives of piperidinium and pyrrolidinium demonstrate a very wide electrochemical window (up to 5.5 V) and they can be compatible with lithium metal anodes. At low potentials in the presence of Li ions in solutions (or on Li metal surfaces), TFSI anions are reduced to insoluble Li compounds which passivate Li, noble metal and graphite electrodes in the Li salt/IL solutions. The mechanism, kinetics and effectiveness of electrodes' passivation in these systems depend on the nature of both IL and electrode used. It was possible to demonstrate reversible behavior of Li/LiMn 1.5 Ni 0.5 O 4 cells (4.8 V) with solutions based on BMPTFSI and MPPpTFSI. Possible parasitic anodic reactions upon charging at the high potentials are much lower in the ILs than in standard solutions.