Elena Levi - Academia.edu (original) (raw)
Papers by Elena Levi
Acta Crystallographica Section A Foundations of Crystallography, 1981
Advanced Energy Materials, 2016
MRS Proceedings, 1997
ABSTRACTThis paper reports on electroanalytical studies of the intercalation-deintercalation of l... more ABSTRACTThis paper reports on electroanalytical studies of the intercalation-deintercalation of lithium into lithiated transition metal oxides which are used as cathodes for Li ion batteries. These include LixCoO2 LixNiO2 and LixMn2O4 spinel. The basic electroanalytical response of these systems in LiAsF6 1M/EC-DMC solutions was obtained from the simultaneous use of slow and fast scan cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT) (from which D vs. E was calculated), and impedance spectroscopy (EIS). Surface sensitive FTIR spectroscopy and XRD were also used for surface and 3D characterization, respectively. A large and important denominator was found in the electrochemical behavior of lithium intercalation-deintercalation into these transition metal oxides and graphite. The use of the electroanalytical response of these systems as a tool for the study of stabilization and failure mechanisms of these materials as cathodes in rechargeable Li batteries is demo...
The Journal of Physical Chemistry B, 1999
ABSTRACT
Solid State Ionics, 2005
The absence of Mg-ion trapping in selenium-based Chevrel phase (in contrast to charge trapping in... more The absence of Mg-ion trapping in selenium-based Chevrel phase (in contrast to charge trapping in MgxMo6S8) was carefully monitored using a combination of three electroanalytical tools: SSCV, PITT and EIS. We discuss the difference between MgxMo6S8 and MgxMo6Se8 (0<x<2) in terms of the higher polarizability of the host's Se2− anions framework, compared to that of S2−, in sulfur-based Chevrel phase,
Journal of Power Sources, 2001
Journal of The Electrochemical Society, 2004
ABSTRACT
This paper describes several general phenomena which relate to Li insertion electrodes. The theme... more This paper describes several general phenomena which relate to Li insertion electrodes. The theme of this work was to look for common denominators in the electrochemical behavior of a variety of Li insertion electrodes, both anodes and cathodes. Taking into account the fact that these are composite electrodes containing active mass in additives (binder, conducting powder), we studied the role of the electrodes' structure vs. the intrinsic properties of the active mass in determining their performance. We found common models which fit a wide variety of Li insertion electrodes. An important point that was explored was the importance of Li insertion via formation of solid solution or via phase transitions in terms of capacity, stability and rate. We also found common failure mechanisms for both anodes and cathodes. These involve the formation of inactive interphase at the boundary between the active mass and the solution, which considerably slows down the electrodes' kinetics. ...
This paper reports on electroanalytical studies of the intercalation-deintercalation of lithium i... more This paper reports on electroanalytical studies of the intercalation-deintercalation of lithium into lithiated transition metal oxides which are used as cathodes for Li ion batteries. These include Li{sub x}CoO{sub 2} Li{sub x}NiO{sub 2} and Li{sub x}Mn{sub 2}O{sub 4} spinel. The basic electroanalytical response of these systems in LiAsF{sub 6} 1M/EC-DMC solutions was obtained from the simultaneous use of slow and fast scan cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT) (from which D vs. E was calculated), and impedance spectroscopy (EIS). Surface sensitive FTIR spectroscopy and XRD were also used for surface and 3D characterization, respectively. A large and important denominator was found in the electrochemical behavior of lithium intercalation-deintercalation into these transition metal oxides and graphite. The use of the electroanalytical response of these systems as a tool for the study of stabilization and failure mechanisms of these materials as catho...
Journal of Power Sources, 2001
Journal of The …, 2001
Comparison Between the Electrochemical Behavior of Disordered Carbons and Graphite Electrodes in ... more Comparison Between the Electrochemical Behavior of Disordered Carbons and Graphite Electrodes in Connection with Their Structure. [Journal of The Electrochemical Society 148, A525 (2001)]. JS Gnanaraj, MD Levi, E. Levi ...
Journal of power …, 1999
Li x Mn 2 O 4 spinels were synthesized in different ways, leading to different particle morpholog... more Li x Mn 2 O 4 spinels were synthesized in different ways, leading to different particle morphologies and different electrochemical behavior. Two types of Li x Mn 2 O 4 electrodes comprised of active mass synthesized in two different ways were investigated in a standard solution (ethylene ...
Solid State Ionics, 2005
The absence of Mg-ion trapping in selenium-based Chevrel phase (in contrast to charge trapping in... more The absence of Mg-ion trapping in selenium-based Chevrel phase (in contrast to charge trapping in MgxMo6S8) was carefully monitored using a combination of three electroanalytical tools: SSCV, PITT and EIS. We discuss the difference between MgxMo6S8 and MgxMo6Se8 (0<x<2) in terms of the higher polarizability of the host's Se2− anions framework, compared to that of S2−, in sulfur-based Chevrel phase,
Journal of Solid State Chemistry, 2006
ABSTRACT
Crystal Growth & Design
Steric and electrostatic effects affect the strength, energy and reactivity of chemical bonds, bu... more Steric and electrostatic effects affect the strength, energy and reactivity of chemical bonds, but their quantification by density functional theory is not straightforward, even for simple molecules. In the previous works devoted to compounds with metal-metal bonds we showed that these effects can be easily and properly described by the difference between formal and effective bond orders; the latter being calculated from the experimental bond lengths using exponential correlations and empirical bond valence parameters. This work applies for the first time the same method to halides with Z-centered M6-clusters (Z are main group elements like Be, B, C and N or transition metals like Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt; M = Sc, Zr, Y, and Gd). It was shown that a spatial inconsistency between short M-Z bonds and relatively rigid anion close-packing results in the high strains in the individual bonds, but the total bond order sums calculated for the M atom in most of the halides are close to the number ...
ACS Applied Materials & Interfaces, 2016
Li- and Mn-rich transition-metal oxides of layered structure are promising cathodes for Li-ion ba... more Li- and Mn-rich transition-metal oxides of layered structure are promising cathodes for Li-ion batteries because of their high capacity values, ≥250 mAh g(-1). These cathodes suffer from capacity fading and discharge voltage decay upon prolonged cycling to potential higher than 4.5 V. Most of these Li- and Mn-rich cathodes contain Ni in a 2+ oxidation state. The fine details of the composition of these materials may be critically important in determining their performance. In the present study, we used Li1.2Ni0.13Mn0.54Co0.13O2 as the reference cathode composition in which Mn ions are substituted by Ni ions so that their average oxidation state in Li1.2Ni0.27Mn0.4Co0.13O2 could change from 2+ to 3+. Upon substitution of Mn with Ni, the specific capacity decreases but, in turn, an impressive stability was gained, about 95% capacity retention after 150 cycles, compared to 77% capacity retention for Li1.2Ni0.13Mn0.54Co0.13O2 cathodes when cycled at a C/5 rate. Also, a higher average discharge voltage of 3.7 V is obtained for Li1.2Ni0.27Mn0.4Co0.13O2 cathodes, which decreases to 3.5 V after 150 cycles, while the voltage fading of cathodes comprising the reference material is more pronounced. The Li1.2Ni0.27Mn0.4Co0.13O2 cathodes also demonstrate higher rate capability compared to the reference Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. These results clearly indicate the importance of the fine composition of cathode materials containing the five elements Li, Mn, Ni, Co, and O. The present study should encourage rigorous optimization efforts related to the fine composition of these cathode materials, before external means such as doping and coating are applied.
Advanced Materials, 2003
There is no doubt that one of the greatest challenges of modern electrochemistry is the developme... more There is no doubt that one of the greatest challenges of modern electrochemistry is the development of high energy density, rechargeable batteries, which are composed of mate-rials as environmentally and abandon-friendly as possible. An excellent candidate as an anode material for ...
Inorganic Chemistry
Pauling's principles developed later in the bond valence model (BVM) are fundamental in descr... more Pauling's principles developed later in the bond valence model (BVM) are fundamental in description of bonding in ionic solids and surface phenomena on metals, but applicability of these principles to the metal-metal bonds in the bulk compounds was demonstrated only recently, with a spotlight on the bond valence-bond length correlations. This work is focused on the bond order conservation in cluster compounds and determination of empiric bond valence parameters for the metal-metal bonds, which ensure very simple and reasonably accurate bonding analysis, with zero cost, in any complex cluster compound. Such peculiarities of cluster compounds as matrix effect and nonuniform distribution of the ionic charges (bond valence sums) on the ligands around metal clusters, as well as other important examples of the BVM application to compounds with metal-metal bonds, are discussed.
Acta Crystallographica Section A Foundations of Crystallography, 1981
Advanced Energy Materials, 2016
MRS Proceedings, 1997
ABSTRACTThis paper reports on electroanalytical studies of the intercalation-deintercalation of l... more ABSTRACTThis paper reports on electroanalytical studies of the intercalation-deintercalation of lithium into lithiated transition metal oxides which are used as cathodes for Li ion batteries. These include LixCoO2 LixNiO2 and LixMn2O4 spinel. The basic electroanalytical response of these systems in LiAsF6 1M/EC-DMC solutions was obtained from the simultaneous use of slow and fast scan cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT) (from which D vs. E was calculated), and impedance spectroscopy (EIS). Surface sensitive FTIR spectroscopy and XRD were also used for surface and 3D characterization, respectively. A large and important denominator was found in the electrochemical behavior of lithium intercalation-deintercalation into these transition metal oxides and graphite. The use of the electroanalytical response of these systems as a tool for the study of stabilization and failure mechanisms of these materials as cathodes in rechargeable Li batteries is demo...
The Journal of Physical Chemistry B, 1999
ABSTRACT
Solid State Ionics, 2005
The absence of Mg-ion trapping in selenium-based Chevrel phase (in contrast to charge trapping in... more The absence of Mg-ion trapping in selenium-based Chevrel phase (in contrast to charge trapping in MgxMo6S8) was carefully monitored using a combination of three electroanalytical tools: SSCV, PITT and EIS. We discuss the difference between MgxMo6S8 and MgxMo6Se8 (0&amp;amp;lt;x&amp;amp;lt;2) in terms of the higher polarizability of the host&amp;#39;s Se2− anions framework, compared to that of S2−, in sulfur-based Chevrel phase,
Journal of Power Sources, 2001
Journal of The Electrochemical Society, 2004
ABSTRACT
This paper describes several general phenomena which relate to Li insertion electrodes. The theme... more This paper describes several general phenomena which relate to Li insertion electrodes. The theme of this work was to look for common denominators in the electrochemical behavior of a variety of Li insertion electrodes, both anodes and cathodes. Taking into account the fact that these are composite electrodes containing active mass in additives (binder, conducting powder), we studied the role of the electrodes' structure vs. the intrinsic properties of the active mass in determining their performance. We found common models which fit a wide variety of Li insertion electrodes. An important point that was explored was the importance of Li insertion via formation of solid solution or via phase transitions in terms of capacity, stability and rate. We also found common failure mechanisms for both anodes and cathodes. These involve the formation of inactive interphase at the boundary between the active mass and the solution, which considerably slows down the electrodes' kinetics. ...
This paper reports on electroanalytical studies of the intercalation-deintercalation of lithium i... more This paper reports on electroanalytical studies of the intercalation-deintercalation of lithium into lithiated transition metal oxides which are used as cathodes for Li ion batteries. These include Li{sub x}CoO{sub 2} Li{sub x}NiO{sub 2} and Li{sub x}Mn{sub 2}O{sub 4} spinel. The basic electroanalytical response of these systems in LiAsF{sub 6} 1M/EC-DMC solutions was obtained from the simultaneous use of slow and fast scan cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT) (from which D vs. E was calculated), and impedance spectroscopy (EIS). Surface sensitive FTIR spectroscopy and XRD were also used for surface and 3D characterization, respectively. A large and important denominator was found in the electrochemical behavior of lithium intercalation-deintercalation into these transition metal oxides and graphite. The use of the electroanalytical response of these systems as a tool for the study of stabilization and failure mechanisms of these materials as catho...
Journal of Power Sources, 2001
Journal of The …, 2001
Comparison Between the Electrochemical Behavior of Disordered Carbons and Graphite Electrodes in ... more Comparison Between the Electrochemical Behavior of Disordered Carbons and Graphite Electrodes in Connection with Their Structure. [Journal of The Electrochemical Society 148, A525 (2001)]. JS Gnanaraj, MD Levi, E. Levi ...
Journal of power …, 1999
Li x Mn 2 O 4 spinels were synthesized in different ways, leading to different particle morpholog... more Li x Mn 2 O 4 spinels were synthesized in different ways, leading to different particle morphologies and different electrochemical behavior. Two types of Li x Mn 2 O 4 electrodes comprised of active mass synthesized in two different ways were investigated in a standard solution (ethylene ...
Solid State Ionics, 2005
The absence of Mg-ion trapping in selenium-based Chevrel phase (in contrast to charge trapping in... more The absence of Mg-ion trapping in selenium-based Chevrel phase (in contrast to charge trapping in MgxMo6S8) was carefully monitored using a combination of three electroanalytical tools: SSCV, PITT and EIS. We discuss the difference between MgxMo6S8 and MgxMo6Se8 (0<x<2) in terms of the higher polarizability of the host's Se2− anions framework, compared to that of S2−, in sulfur-based Chevrel phase,
Journal of Solid State Chemistry, 2006
ABSTRACT
Crystal Growth & Design
Steric and electrostatic effects affect the strength, energy and reactivity of chemical bonds, bu... more Steric and electrostatic effects affect the strength, energy and reactivity of chemical bonds, but their quantification by density functional theory is not straightforward, even for simple molecules. In the previous works devoted to compounds with metal-metal bonds we showed that these effects can be easily and properly described by the difference between formal and effective bond orders; the latter being calculated from the experimental bond lengths using exponential correlations and empirical bond valence parameters. This work applies for the first time the same method to halides with Z-centered M6-clusters (Z are main group elements like Be, B, C and N or transition metals like Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt; M = Sc, Zr, Y, and Gd). It was shown that a spatial inconsistency between short M-Z bonds and relatively rigid anion close-packing results in the high strains in the individual bonds, but the total bond order sums calculated for the M atom in most of the halides are close to the number ...
ACS Applied Materials & Interfaces, 2016
Li- and Mn-rich transition-metal oxides of layered structure are promising cathodes for Li-ion ba... more Li- and Mn-rich transition-metal oxides of layered structure are promising cathodes for Li-ion batteries because of their high capacity values, ≥250 mAh g(-1). These cathodes suffer from capacity fading and discharge voltage decay upon prolonged cycling to potential higher than 4.5 V. Most of these Li- and Mn-rich cathodes contain Ni in a 2+ oxidation state. The fine details of the composition of these materials may be critically important in determining their performance. In the present study, we used Li1.2Ni0.13Mn0.54Co0.13O2 as the reference cathode composition in which Mn ions are substituted by Ni ions so that their average oxidation state in Li1.2Ni0.27Mn0.4Co0.13O2 could change from 2+ to 3+. Upon substitution of Mn with Ni, the specific capacity decreases but, in turn, an impressive stability was gained, about 95% capacity retention after 150 cycles, compared to 77% capacity retention for Li1.2Ni0.13Mn0.54Co0.13O2 cathodes when cycled at a C/5 rate. Also, a higher average discharge voltage of 3.7 V is obtained for Li1.2Ni0.27Mn0.4Co0.13O2 cathodes, which decreases to 3.5 V after 150 cycles, while the voltage fading of cathodes comprising the reference material is more pronounced. The Li1.2Ni0.27Mn0.4Co0.13O2 cathodes also demonstrate higher rate capability compared to the reference Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. These results clearly indicate the importance of the fine composition of cathode materials containing the five elements Li, Mn, Ni, Co, and O. The present study should encourage rigorous optimization efforts related to the fine composition of these cathode materials, before external means such as doping and coating are applied.
Advanced Materials, 2003
There is no doubt that one of the greatest challenges of modern electrochemistry is the developme... more There is no doubt that one of the greatest challenges of modern electrochemistry is the development of high energy density, rechargeable batteries, which are composed of mate-rials as environmentally and abandon-friendly as possible. An excellent candidate as an anode material for ...
Inorganic Chemistry
Pauling's principles developed later in the bond valence model (BVM) are fundamental in descr... more Pauling's principles developed later in the bond valence model (BVM) are fundamental in description of bonding in ionic solids and surface phenomena on metals, but applicability of these principles to the metal-metal bonds in the bulk compounds was demonstrated only recently, with a spotlight on the bond valence-bond length correlations. This work is focused on the bond order conservation in cluster compounds and determination of empiric bond valence parameters for the metal-metal bonds, which ensure very simple and reasonably accurate bonding analysis, with zero cost, in any complex cluster compound. Such peculiarities of cluster compounds as matrix effect and nonuniform distribution of the ionic charges (bond valence sums) on the ligands around metal clusters, as well as other important examples of the BVM application to compounds with metal-metal bonds, are discussed.