Michael Talianker | Ben Gurion University of the Negev (original) (raw)
Papers by Michael Talianker
Inorganics
High-energy cathode materials that are Li- and Mn-rich lithiated oxides—for instance, 0.35Li2MnO3... more High-energy cathode materials that are Li- and Mn-rich lithiated oxides—for instance, 0.35Li2MnO3.0.65LiNi0.35Mn0.45Co0.20O2 (HE-NCM)—are promising for advanced lithium-ion batteries. However, HE-NCM cathodes suffer from severe degradation during cycling, causing gradual capacity loss, voltage fading, and low-rate capability performance. In this work, we applied an effective approach to creating a nano-sized surface layer of Li2SO4 on the above material, providing mitigation of the interfacial side reactions while retaining the structural integrity of the cathodes upon extended cycling. The Li2SO4 coating was formed on the surface of the material by mixing it with nanocrystalline Li2SO4 and annealing at 600 °C. We established enhanced electrochemical behavior with ~20% higher discharge capacity, improved charge-transfer kinetics, and higher rate capability of HE-NCM cathodes due to the presence of the Li2SO4 coating. Online electrochemical mass spectrometry studies revealed lower CO...
Materials, 2021
In this work, we continued our systematic investigations on synthesis, structural studies, and el... more In this work, we continued our systematic investigations on synthesis, structural studies, and electrochemical behavior of Ni-rich materials Li[NixCoyMnz]O2 (x + y + z = 1; x ≥ 0.8) for advanced lithium-ion batteries (LIBs). We focused, herein, on LiNi0.85Co0.10Mn0.05O2 (NCM85) and demonstrated that doping this material with high-charge cation Mo6+ (1 at. %, by a minor nickel substitution) results in substantially stable cycling performance, increased rate capability, lowering of the voltage hysteresis, and impedance in Li-cells with EC-EMC/LiPF6 solutions. Incorporation of Mo-dopant into the NCM85 structure was carried out by in-situ approach, upon the synthesis using ammonium molybdate as the precursor. From X-ray diffraction studies and based on our previous investigation of Mo-doped NCM523 and Ni-rich NCM811 materials, it was revealed that Mo6+ preferably substitutes Ni residing either in 3a or 3b sites. We correlated the improved behavior of the doped NCM85 electrode materials ...
Advanced Energy and Sustainability Research, 2021
Materials, 2020
This work continues our systematic study of Li- and Mn- rich cathodes for lithium-ion batteries. ... more This work continues our systematic study of Li- and Mn- rich cathodes for lithium-ion batteries. We chose Li2MnO3 as a model electrode material with the aim of correlating the improved electrochemical characteristics of these cathodes initially activated at 0 °C with the structural evolution of Li2MnO3, oxygen loss, formation of per-oxo like species (O22−) and the surface chemistry. It was established that performing a few initial charge/discharge (activation) cycles of Li2MnO3 at 0 °C resulted in increased discharge capacity and higher capacity retention, and decreased and substantially stabilized the voltage hysteresis upon subsequent cycling at 30 °C or at 45 °C. In contrast to the activation of Li2MnO3 at these higher temperatures, Li2MnO3 underwent step-by-step activation at 0 °C, providing a stepwise traversing of the voltage plateau at >4.5 V during initial cycling. Importantly, these findings agree well with our previous studies on the activation at 0 °C of 0.35Li2MnO3·0....
ACS Applied Energy Materials, 2020
We present in this paper a modification and stabilization approach for the surface of a high spec... more We present in this paper a modification and stabilization approach for the surface of a high specific capacity Ni-rich cathode material LiNi 0.85 Co 0.10 Mn 0.05 O 2 (NCM85) via SO 2 gas treatment at 250-400 C, in order to enhance its electrochemical performance in advanced lithium-ion batteries. It was established that SO 2 interactions with NCM85 result in the formation of a nano-meter size Li 2 SO 4 surface layer on the oxide particles with no impact on the bulk structure of the material and its morphology. We consider the above interactions as oxidationreduction processes resulting in direct oxidation of sulfur and partial reduction of Ni 3+ as revealed by high-resolution XPS and electron paramagnetic resonance studies. The important impacts of the SO 2 treatment are remarkably stable cycling performance of cathodes comprising this material with ~10% increase in capacity retention and lesser voltage hysteresis upon cycling compared to untreated NCM85 cathodes. The SO 2-treated NCM85 material is also significantly thermally stable demonstrating lower heat evolution upon thermal reactions with standard EC-EMC/LiPF 6 solutions by 12-20%, compared to untreated material. The proposed approach to modify the surface of Ni-rich NCM cathode materials by SO 2 treatment is demonstrated to be a promising method to enhance their electrochemical performance. This work demonstrates a leap in performance of Ni-rich NCM cathode materials by increasing the content of nickel compared to any benchmark cathodes and a Promising approach for stabilization by surface modification.
ACS Applied Energy Materials, 2019
The work reported herein is an important continuation of our recent experimental and computationa... more The work reported herein is an important continuation of our recent experimental and computational studies on Li[Ni x Co y Mn z ]O 2 (x + y + z = 1) cathode materials for Li-ion batteries, containing minor amounts of multivalent cationic dopants like Al 3+ , Zr 4+ , W 6+ , Mo 6+. On the basis of DFT calculations for LiNi 0.8 Co 0.1 Mn 0.1 O 2 , it was concluded that Mo 6+ cations preferably substitute Ni cations in the layered structure due to the lowest substitution energy compared to Li, Co, and Mn. It was established that the electrochemical behavior of LiNi 0.8 Co 0.1 Mn 0.1 O 2 as a positive electrode material for Li-ion batteries can be substantially improved by doping with 1−3 mol % of Mo 6+ , in terms of lowering the irreversible capacity loss during the first cycle, increasing discharge capacity and rate capability, decreasing capacity fade upon prolonged cycling, and lowering the voltage hysteresis and chargetransfer resistance. The latter is attributed to the presence of additional conduction bands near the Fermi level of the doped materials, which facilitate Li-ions and electron transfer within the doped material. This is expressed by a lower charge-transfer resistance of Mo-doped electrodes as shown by impedance spectroscopy studies. We also discovered unique segregation phenomena, in which the surface concentration of the transition metals and dopant differs from that of the bulk. This near surface segregation of the Mo-dopant seems to have a stabilization effect on these cathode materials.
Journal of Materials Chemistry A, 2019
The addition of Fe in Li-rich nickel cobalt manganese oxides allows for higher specific charge, p... more The addition of Fe in Li-rich nickel cobalt manganese oxides allows for higher specific charge, potential drop mitigation and enhanced rate capability.
Journal of The Electrochemical Society, 2017
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](ACS applied materials & interfaces, Jan 5, 2018
Doping LiNiCoMnO (NCM523) cathode material by small amount of Mo ions, around 1 mol %, affects pr... more Doping LiNiCoMnO (NCM523) cathode material by small amount of Mo ions, around 1 mol %, affects pronouncedly its structure, surface properties, and electronic and electrochemical behavior. Cathodes comprising Mo-doped NCM523 exhibited in Li cells higher specific capacities, higher rate capabilities, lower capacity fading, and lower charge-transfer resistance that relates to a more stable electrode/solution interface due to doping. This, in turn, is ascribed to the fact that the Mo ions tend to concentrate more at the surface, as a result of a synthesis that always includes a necessary calcination, high-temperature stage. This phenomenon of the Mo dopant segregation at the surface in NCM523 material was discovered in the present work for the first time. It appears that Mo doping reduces the reactivity of the Ni-rich NCM cathode materials toward the standard electrolyte solutions of Li-ion batteries. Using density functional theory (DFT) calculations, we showed that Mo ions are prefera...
Inorganics, 2017
Amongst a number of different cathode materials, the layered nickel-rich LiNi y Co x Mn 1−y−x O 2... more Amongst a number of different cathode materials, the layered nickel-rich LiNi y Co x Mn 1−y−x O 2 and the integrated lithium-rich xLi 2 MnO 3 •(1 − x)Li[Ni a Co b Mn c ]O 2 (a + b + c = 1) have received considerable attention over the last decade due to their high capacities of~195 and~250 mAh•g −1 , respectively. Both materials are believed to play a vital role in the development of future electric vehicles, which makes them highly attractive for researchers from academia and industry alike. The review at hand deals with both cathode materials and highlights recent achievements to enhance capacity stability, voltage stability, and rate capability, etc. The focus of this paper is on novel strategies and established methods such as coatings and dopings.
Advanced Energy Materials, 2017
Since the discovery by Thackeray and Rossouw in 1991 that acid could activate Li 2 MnO 3 , [1] fo... more Since the discovery by Thackeray and Rossouw in 1991 that acid could activate Li 2 MnO 3 , [1] followed by the discovery by Gopukumar and co-workers in 1999 that this inactive phase could be activated electrochemically, [2] interest in integrated Li 2 MnO 3 and composite phases has grown rapidly. [3] The Li 2 MnO 3 phase can deliver a high theoretical capacity based on Li extraction of ≈460 mA h g −1 , though practical realities limit the total extracted capacity to ≈100 mA h g −1 , often with rapid capacity decay. [4] Attempts at stabilizing this material through lattice doping or forming "composites" with alternative materials mirrored struggles seen in the layered transition metal (TM) oxide field. For instance, LiNiO 2 suffers Ni 2+ mixing in the Li + layer that causes dramatically different capacities for different synthesis parameters, [5] and LiMnO 2 does not easily form a layered R-3m structure, [6] rather forming the orthorhombic phase, pmnm with a zigzag structure that causes low rate capability and capacity. [7] Incorporation of other Co, Mn, or Ni into pure lithiated transition metal oxides alleviated problems found with the pure, single LiTMO 2 materials. [8] Using a similar strategy, integration of Li 2 MnO 3 with layered LiMO 2 and spinel components produced electrode materials that could perform >300 mA h g −1 discharge capacity reversibly. [3,9] Subsequent patent applications were granted to Thackeray and co-workers on integrated materials containing Li 2 MnO 3 and both the layered TM oxides [10] and with spinel material. [11] Integrated xLi 2 MnO 3 •yLiNi a Co b Mn c O 2 (x + y = 1, a + b + c = 1) (Li-rich) materials are of particular interest since they have large, stable capacities above 250 mA h g −1 , though initial charging during the activation step can reach much higher, even up to >500 mA h g −1. [12,13] Activation is a complex process involving oxygen release, Li 2 O extraction, and the formation of surface spinel. [13-15] The spinel-phase domains formed can prevent to some extent further oxygen release from the bulk of the material during cycling, something which the material is susceptible to since it is believed that along with TMs, O 2− acts as a Li-rich electrode materials of the family xLi 2 MnO 3 •(1−x)LiNi a Co b Mn c O 2 (a + b + c = 1) suffer a voltage fade upon cycling that limits their utilization in commercial batteries despite their extremely high discharge capacity, ≈250 mA h g −1. Li-rich, 0.35Li 2 MnO 3 •0.65LiNi 0.35 Mn 0.45 Co 0.20 O 2 , is exposed to NH 3 at 400 °C, producing materials with improved characteristics: enhanced electrode capacity and a limited average voltage fade during 100 cycles in half cells versus Li. Three main changes caused by NH 3 treatment are established. First, a general bulk reduction of Co and Mn is observed via X-ray photoelectron spectroscopy and X-ray absorption near edge structure. Next, a structural rearrangement lowers the coordination number of CoO and MnO bonds, as well as formation of a surface spinellike structure. Additionally, Li + removal from the bulk causes the formation of surface LiOH, Li 2 CO 3 , and Li 2 O. These structural and surface changes can enhance the voltage and capacity stability of the Li-rich material electrodes after moderate NH 3 treatment times of 1-2 h.
Journal of Materials Chemistry A, 2016
The high charge-state dopant Zr4+ improves the structural stability and electrochemical behavior ... more The high charge-state dopant Zr4+ improves the structural stability and electrochemical behavior of the lithiated transition metal oxide LiNi0.6Co0.2Mn0.2O2.
The Journal of Physical Chemistry C, 2016
The main goal of this work was to modify activated carbon (AC) with carbon nano-dots (Cdots) and ... more The main goal of this work was to modify activated carbon (AC) with carbon nano-dots (Cdots) and to explore the modified composites as electrode materials for supercapacitors. C-dots were synthesized by sonication of polyethylene glycol followed by sonochemical modification of AC matrices with the pre-prepared C-dots. Sonication introduces the C-dots into the pores of the AC. The effect of the C-dots introduction into the AC and their incorporation into the pores was studied. The porosity of the AC/C-dots and the AC reference materials were explored, as well as the impact of the C-dots loading on the performance of the electrodes comprising these AC/Cdots. It was found that the AC/C-dots electrodes demonstrate a specific capacitance of 0.185 Fcm-2 (per specific electrode area), three times higher than the capacitance of unmodified AC electrodes per specific electrode's area. It was established that the new electrode's material, namely AC/C-dots, exhibits very stable electrochemical behavior. Many thousands of cycles could be demonstrated with stable capacity and a coulombic efficiency of around 100%.
Acta Crystallographica Section A Foundations of Crystallography, 2011
Poster Sessions C698 field E = 1 kV mm-1 , the changes of bond length were (5.2±0.2)10-5 Å and (3... more Poster Sessions C698 field E = 1 kV mm-1 , the changes of bond length were (5.2±0.2)10-5 Å and (3.0±0.8)10-5 Å, respectively. The same measurements on LiH 2 PO 3 (a 1 =11.024, a 2 =5.060, a 3 =5.169, Z=4)[1]are under way and will be compared with the results of LiH 2 PO 4. This will help to understand the relationship between external deformation and the specific response of chemical bonds in ternary compounds.
Journal of The Electrochemical Society, 2015
ABSTRACT
Metallurgical Transactions A, 1990
The phenomenological double-shear theory of martensite crystallography has been applied to the/3 ... more The phenomenological double-shear theory of martensite crystallography has been applied to the/3 ~ a' martensitic transformation in the U-1.6 at. pct Ga alloy. A correspondence matrix for the/3 ~ a' transformation was derived from the experimentally determined/3/a' orientation relationship, and the double lattice invariant shear was considered as a combination of the principal slip (010) [100L with one of the minor slips in the a-uranium structure. The theoretical predictions of the habit plane are in good agreement with the experimental observations. I. INTRODUCTION SINCE the first formulation of the phenomenological theory of martensite crystallography based on the concept of an invariant plane strain (IPS), IL21 many investigations have been carried out in an attempt to evaluate the applicability of the theory to various martensitic transformations. In the early theories, the total shape deformation associated with the phase transformation was resolved into a rotation, a pure strain, and a single lattice invariant shear. The single-shear approach proved to be successful in accounting for the crystallographic characteristics of many martensitic transformations; however, the theoretical predictions, in some cases, were not in good agreement with available experimental observations. [31 This stimulated further theoretical work, and a martensite crystallography theory with a double lattice invariant shear was developed. [4.5,6] Although most of the studies focused on application of theories to the martensitic reactions in steels, it was pointed out [71 that the y ~ a' and the/3 ~ a' martensitic transformations in uranium alloys also provide a good opportunity for testing the crystallographic theories of martensite. The first detailed experimental investigation of the martensite in U-5 at. pct Mo alloy was performed by May, ls~ who proposed the correspondence matrix for the y-* a' transformation. Such correspondence, as well as the elements of lattice invariant shear and the lattice parameters of the parent and product, determines the data required to apply the IPS theories. Later, Crocker and Ross [7] discussed May's correspondence, comparing it with that adopted by Christian. [91 They attempted to account for the habit plane in the 3' ~ a' transformation in U-5 at. pct Mo alloy by using for the computation different possible twinning planes and directions as the elements of lattice invariant shear. However, basing their work on the assumption that only one shear system was operative, they failed to obtain a real solution. Speer and Edmonds I~~ have proposed another lattice correspondence for the 3' ~ a' transformation. In their D.
Materials Science and Engineering: A, 1996
The influence of retrogression and reaging (RR) treatment on the resistance to stress-corrosion c... more The influence of retrogression and reaging (RR) treatment on the resistance to stress-corrosion cracking of a commercial AI-Li 8090 alloy was investigated. The retrogression was performed for various times at temperatures in the range 200-260°C. The reaging treatment was carried out at 170°C. Stress corrosion tests were performed using C-ring specimens and by alte~ate immersion. Changes in the microstructure of the material near the grain boundaries were studied by transmission electron microscopy. It was shown that RR treatment substantially improved the resistance to SCC of the alloy. As with 7000 type "A1 alloys, the RR treatment brings about the dissipation of dislocations; the greater the extent of dissipation of dislocations, the greater the resistance to SCC. Another factor which, possibly, affects the sensitivity to stress-corrosion in this alloy is the presence of the 8' precipitates near the grain boundaries. The best results on SCC resistance were obtained for retrogression performed for 30 min at 260°C followed by reaging. For such treatment a zone completely free of fi' precipitates was developed near the grain boundaries.
Materials Science and Engineering: A, 2003
ABSTRACT The paper considers the stability of the phases formed in alloys of aluminum with transi... more ABSTRACT The paper considers the stability of the phases formed in alloys of aluminum with transition metals (TM) in terms of the theory of coordination compounds. The structural stability is related to the degree of distortion of the first-neighbor coordination icosahedra commonly found around TM atoms. Changes in the symmetry of coordination polyhedrons are explained in terms of the Jahn–Teller theorem. The stability of the structures may be correlated with the effective charge of the TM atom and with the electronegativity of its neighbors: the phase transforms to the structure with lower symmetry when the electronegativity or effective charge decrease.
Materials Science and Engineering: A, 1989
Abstract The submicrometre dispersoids containing iron in the aged AlLiCuMgZr alloy have been... more Abstract The submicrometre dispersoids containing iron in the aged AlLiCuMgZr alloy have been investigated by transmission electron microscopy combined with energy dispersive microprobe analysis. The dispersoids were identified as monoclinic Al 3 Fe phase. They grow as elongated plates or may appear as randomly shaped particles. They are not single crystals but consist of two (or more) small grains, thus exhibiting complex selected area diffraction patterns owing to the superposition of several reflecting zones arising from different grains.
Journal of The Electrochemical Society, 2012
We investigated the structural characteristics of Li-rich xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O... more We investigated the structural characteristics of Li-rich xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 cathode material (x around 0.5, y:z:w around 2:2:1) and its electrochemical performance in lithium cells at 30 and 60 • C. It was established that nanoparticles of the xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 compound are intergrown on the nano-scale and are built of thin plates of 40-50 Å. We demonstrated that xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 electrodes exhibited at 60 • C high capacities of ∼270 and ∼220 mAh/g at 1C and 2C rates, respectively. They can be cycled effectively at 30 and 60 • C providing capacity ∼250 mAh/g in the initial cycles, but it fades upon prolonged cycling due, to some extent, to increasing the electrode impedance (charge-transfer resistance) especially at the elevated temperature. The effective chemical diffusion coefficient of Li + in these electrodes measured during charge to 4.7 V by potentiostatic intermittent titration technique (PITT) was found to be ∼10 −10 cm 2 /s. From convergent beam electron diffraction and Raman spectroscopy studies we established, for the first time, that partial structural transition from layered-type to spinel-type ordering in xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 electrodes occurred in the initial charge to 4.7 V and even at the early stages of charging at 4.1 V-4.4 V. The thermal behavior of the xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 material and electrodes are also discussed.
Inorganics
High-energy cathode materials that are Li- and Mn-rich lithiated oxides—for instance, 0.35Li2MnO3... more High-energy cathode materials that are Li- and Mn-rich lithiated oxides—for instance, 0.35Li2MnO3.0.65LiNi0.35Mn0.45Co0.20O2 (HE-NCM)—are promising for advanced lithium-ion batteries. However, HE-NCM cathodes suffer from severe degradation during cycling, causing gradual capacity loss, voltage fading, and low-rate capability performance. In this work, we applied an effective approach to creating a nano-sized surface layer of Li2SO4 on the above material, providing mitigation of the interfacial side reactions while retaining the structural integrity of the cathodes upon extended cycling. The Li2SO4 coating was formed on the surface of the material by mixing it with nanocrystalline Li2SO4 and annealing at 600 °C. We established enhanced electrochemical behavior with ~20% higher discharge capacity, improved charge-transfer kinetics, and higher rate capability of HE-NCM cathodes due to the presence of the Li2SO4 coating. Online electrochemical mass spectrometry studies revealed lower CO...
Materials, 2021
In this work, we continued our systematic investigations on synthesis, structural studies, and el... more In this work, we continued our systematic investigations on synthesis, structural studies, and electrochemical behavior of Ni-rich materials Li[NixCoyMnz]O2 (x + y + z = 1; x ≥ 0.8) for advanced lithium-ion batteries (LIBs). We focused, herein, on LiNi0.85Co0.10Mn0.05O2 (NCM85) and demonstrated that doping this material with high-charge cation Mo6+ (1 at. %, by a minor nickel substitution) results in substantially stable cycling performance, increased rate capability, lowering of the voltage hysteresis, and impedance in Li-cells with EC-EMC/LiPF6 solutions. Incorporation of Mo-dopant into the NCM85 structure was carried out by in-situ approach, upon the synthesis using ammonium molybdate as the precursor. From X-ray diffraction studies and based on our previous investigation of Mo-doped NCM523 and Ni-rich NCM811 materials, it was revealed that Mo6+ preferably substitutes Ni residing either in 3a or 3b sites. We correlated the improved behavior of the doped NCM85 electrode materials ...
Advanced Energy and Sustainability Research, 2021
Materials, 2020
This work continues our systematic study of Li- and Mn- rich cathodes for lithium-ion batteries. ... more This work continues our systematic study of Li- and Mn- rich cathodes for lithium-ion batteries. We chose Li2MnO3 as a model electrode material with the aim of correlating the improved electrochemical characteristics of these cathodes initially activated at 0 °C with the structural evolution of Li2MnO3, oxygen loss, formation of per-oxo like species (O22−) and the surface chemistry. It was established that performing a few initial charge/discharge (activation) cycles of Li2MnO3 at 0 °C resulted in increased discharge capacity and higher capacity retention, and decreased and substantially stabilized the voltage hysteresis upon subsequent cycling at 30 °C or at 45 °C. In contrast to the activation of Li2MnO3 at these higher temperatures, Li2MnO3 underwent step-by-step activation at 0 °C, providing a stepwise traversing of the voltage plateau at >4.5 V during initial cycling. Importantly, these findings agree well with our previous studies on the activation at 0 °C of 0.35Li2MnO3·0....
ACS Applied Energy Materials, 2020
We present in this paper a modification and stabilization approach for the surface of a high spec... more We present in this paper a modification and stabilization approach for the surface of a high specific capacity Ni-rich cathode material LiNi 0.85 Co 0.10 Mn 0.05 O 2 (NCM85) via SO 2 gas treatment at 250-400 C, in order to enhance its electrochemical performance in advanced lithium-ion batteries. It was established that SO 2 interactions with NCM85 result in the formation of a nano-meter size Li 2 SO 4 surface layer on the oxide particles with no impact on the bulk structure of the material and its morphology. We consider the above interactions as oxidationreduction processes resulting in direct oxidation of sulfur and partial reduction of Ni 3+ as revealed by high-resolution XPS and electron paramagnetic resonance studies. The important impacts of the SO 2 treatment are remarkably stable cycling performance of cathodes comprising this material with ~10% increase in capacity retention and lesser voltage hysteresis upon cycling compared to untreated NCM85 cathodes. The SO 2-treated NCM85 material is also significantly thermally stable demonstrating lower heat evolution upon thermal reactions with standard EC-EMC/LiPF 6 solutions by 12-20%, compared to untreated material. The proposed approach to modify the surface of Ni-rich NCM cathode materials by SO 2 treatment is demonstrated to be a promising method to enhance their electrochemical performance. This work demonstrates a leap in performance of Ni-rich NCM cathode materials by increasing the content of nickel compared to any benchmark cathodes and a Promising approach for stabilization by surface modification.
ACS Applied Energy Materials, 2019
The work reported herein is an important continuation of our recent experimental and computationa... more The work reported herein is an important continuation of our recent experimental and computational studies on Li[Ni x Co y Mn z ]O 2 (x + y + z = 1) cathode materials for Li-ion batteries, containing minor amounts of multivalent cationic dopants like Al 3+ , Zr 4+ , W 6+ , Mo 6+. On the basis of DFT calculations for LiNi 0.8 Co 0.1 Mn 0.1 O 2 , it was concluded that Mo 6+ cations preferably substitute Ni cations in the layered structure due to the lowest substitution energy compared to Li, Co, and Mn. It was established that the electrochemical behavior of LiNi 0.8 Co 0.1 Mn 0.1 O 2 as a positive electrode material for Li-ion batteries can be substantially improved by doping with 1−3 mol % of Mo 6+ , in terms of lowering the irreversible capacity loss during the first cycle, increasing discharge capacity and rate capability, decreasing capacity fade upon prolonged cycling, and lowering the voltage hysteresis and chargetransfer resistance. The latter is attributed to the presence of additional conduction bands near the Fermi level of the doped materials, which facilitate Li-ions and electron transfer within the doped material. This is expressed by a lower charge-transfer resistance of Mo-doped electrodes as shown by impedance spectroscopy studies. We also discovered unique segregation phenomena, in which the surface concentration of the transition metals and dopant differs from that of the bulk. This near surface segregation of the Mo-dopant seems to have a stabilization effect on these cathode materials.
Journal of Materials Chemistry A, 2019
The addition of Fe in Li-rich nickel cobalt manganese oxides allows for higher specific charge, p... more The addition of Fe in Li-rich nickel cobalt manganese oxides allows for higher specific charge, potential drop mitigation and enhanced rate capability.
Journal of The Electrochemical Society, 2017
ACS applied materials & interfaces, Jan 5, 2018
Doping LiNiCoMnO (NCM523) cathode material by small amount of Mo ions, around 1 mol %, affects pr... more Doping LiNiCoMnO (NCM523) cathode material by small amount of Mo ions, around 1 mol %, affects pronouncedly its structure, surface properties, and electronic and electrochemical behavior. Cathodes comprising Mo-doped NCM523 exhibited in Li cells higher specific capacities, higher rate capabilities, lower capacity fading, and lower charge-transfer resistance that relates to a more stable electrode/solution interface due to doping. This, in turn, is ascribed to the fact that the Mo ions tend to concentrate more at the surface, as a result of a synthesis that always includes a necessary calcination, high-temperature stage. This phenomenon of the Mo dopant segregation at the surface in NCM523 material was discovered in the present work for the first time. It appears that Mo doping reduces the reactivity of the Ni-rich NCM cathode materials toward the standard electrolyte solutions of Li-ion batteries. Using density functional theory (DFT) calculations, we showed that Mo ions are prefera...
Inorganics, 2017
Amongst a number of different cathode materials, the layered nickel-rich LiNi y Co x Mn 1−y−x O 2... more Amongst a number of different cathode materials, the layered nickel-rich LiNi y Co x Mn 1−y−x O 2 and the integrated lithium-rich xLi 2 MnO 3 •(1 − x)Li[Ni a Co b Mn c ]O 2 (a + b + c = 1) have received considerable attention over the last decade due to their high capacities of~195 and~250 mAh•g −1 , respectively. Both materials are believed to play a vital role in the development of future electric vehicles, which makes them highly attractive for researchers from academia and industry alike. The review at hand deals with both cathode materials and highlights recent achievements to enhance capacity stability, voltage stability, and rate capability, etc. The focus of this paper is on novel strategies and established methods such as coatings and dopings.
Advanced Energy Materials, 2017
Since the discovery by Thackeray and Rossouw in 1991 that acid could activate Li 2 MnO 3 , [1] fo... more Since the discovery by Thackeray and Rossouw in 1991 that acid could activate Li 2 MnO 3 , [1] followed by the discovery by Gopukumar and co-workers in 1999 that this inactive phase could be activated electrochemically, [2] interest in integrated Li 2 MnO 3 and composite phases has grown rapidly. [3] The Li 2 MnO 3 phase can deliver a high theoretical capacity based on Li extraction of ≈460 mA h g −1 , though practical realities limit the total extracted capacity to ≈100 mA h g −1 , often with rapid capacity decay. [4] Attempts at stabilizing this material through lattice doping or forming "composites" with alternative materials mirrored struggles seen in the layered transition metal (TM) oxide field. For instance, LiNiO 2 suffers Ni 2+ mixing in the Li + layer that causes dramatically different capacities for different synthesis parameters, [5] and LiMnO 2 does not easily form a layered R-3m structure, [6] rather forming the orthorhombic phase, pmnm with a zigzag structure that causes low rate capability and capacity. [7] Incorporation of other Co, Mn, or Ni into pure lithiated transition metal oxides alleviated problems found with the pure, single LiTMO 2 materials. [8] Using a similar strategy, integration of Li 2 MnO 3 with layered LiMO 2 and spinel components produced electrode materials that could perform >300 mA h g −1 discharge capacity reversibly. [3,9] Subsequent patent applications were granted to Thackeray and co-workers on integrated materials containing Li 2 MnO 3 and both the layered TM oxides [10] and with spinel material. [11] Integrated xLi 2 MnO 3 •yLiNi a Co b Mn c O 2 (x + y = 1, a + b + c = 1) (Li-rich) materials are of particular interest since they have large, stable capacities above 250 mA h g −1 , though initial charging during the activation step can reach much higher, even up to >500 mA h g −1. [12,13] Activation is a complex process involving oxygen release, Li 2 O extraction, and the formation of surface spinel. [13-15] The spinel-phase domains formed can prevent to some extent further oxygen release from the bulk of the material during cycling, something which the material is susceptible to since it is believed that along with TMs, O 2− acts as a Li-rich electrode materials of the family xLi 2 MnO 3 •(1−x)LiNi a Co b Mn c O 2 (a + b + c = 1) suffer a voltage fade upon cycling that limits their utilization in commercial batteries despite their extremely high discharge capacity, ≈250 mA h g −1. Li-rich, 0.35Li 2 MnO 3 •0.65LiNi 0.35 Mn 0.45 Co 0.20 O 2 , is exposed to NH 3 at 400 °C, producing materials with improved characteristics: enhanced electrode capacity and a limited average voltage fade during 100 cycles in half cells versus Li. Three main changes caused by NH 3 treatment are established. First, a general bulk reduction of Co and Mn is observed via X-ray photoelectron spectroscopy and X-ray absorption near edge structure. Next, a structural rearrangement lowers the coordination number of CoO and MnO bonds, as well as formation of a surface spinellike structure. Additionally, Li + removal from the bulk causes the formation of surface LiOH, Li 2 CO 3 , and Li 2 O. These structural and surface changes can enhance the voltage and capacity stability of the Li-rich material electrodes after moderate NH 3 treatment times of 1-2 h.
Journal of Materials Chemistry A, 2016
The high charge-state dopant Zr4+ improves the structural stability and electrochemical behavior ... more The high charge-state dopant Zr4+ improves the structural stability and electrochemical behavior of the lithiated transition metal oxide LiNi0.6Co0.2Mn0.2O2.
The Journal of Physical Chemistry C, 2016
The main goal of this work was to modify activated carbon (AC) with carbon nano-dots (Cdots) and ... more The main goal of this work was to modify activated carbon (AC) with carbon nano-dots (Cdots) and to explore the modified composites as electrode materials for supercapacitors. C-dots were synthesized by sonication of polyethylene glycol followed by sonochemical modification of AC matrices with the pre-prepared C-dots. Sonication introduces the C-dots into the pores of the AC. The effect of the C-dots introduction into the AC and their incorporation into the pores was studied. The porosity of the AC/C-dots and the AC reference materials were explored, as well as the impact of the C-dots loading on the performance of the electrodes comprising these AC/Cdots. It was found that the AC/C-dots electrodes demonstrate a specific capacitance of 0.185 Fcm-2 (per specific electrode area), three times higher than the capacitance of unmodified AC electrodes per specific electrode's area. It was established that the new electrode's material, namely AC/C-dots, exhibits very stable electrochemical behavior. Many thousands of cycles could be demonstrated with stable capacity and a coulombic efficiency of around 100%.
Acta Crystallographica Section A Foundations of Crystallography, 2011
Poster Sessions C698 field E = 1 kV mm-1 , the changes of bond length were (5.2±0.2)10-5 Å and (3... more Poster Sessions C698 field E = 1 kV mm-1 , the changes of bond length were (5.2±0.2)10-5 Å and (3.0±0.8)10-5 Å, respectively. The same measurements on LiH 2 PO 3 (a 1 =11.024, a 2 =5.060, a 3 =5.169, Z=4)[1]are under way and will be compared with the results of LiH 2 PO 4. This will help to understand the relationship between external deformation and the specific response of chemical bonds in ternary compounds.
Journal of The Electrochemical Society, 2015
ABSTRACT
Metallurgical Transactions A, 1990
The phenomenological double-shear theory of martensite crystallography has been applied to the/3 ... more The phenomenological double-shear theory of martensite crystallography has been applied to the/3 ~ a' martensitic transformation in the U-1.6 at. pct Ga alloy. A correspondence matrix for the/3 ~ a' transformation was derived from the experimentally determined/3/a' orientation relationship, and the double lattice invariant shear was considered as a combination of the principal slip (010) [100L with one of the minor slips in the a-uranium structure. The theoretical predictions of the habit plane are in good agreement with the experimental observations. I. INTRODUCTION SINCE the first formulation of the phenomenological theory of martensite crystallography based on the concept of an invariant plane strain (IPS), IL21 many investigations have been carried out in an attempt to evaluate the applicability of the theory to various martensitic transformations. In the early theories, the total shape deformation associated with the phase transformation was resolved into a rotation, a pure strain, and a single lattice invariant shear. The single-shear approach proved to be successful in accounting for the crystallographic characteristics of many martensitic transformations; however, the theoretical predictions, in some cases, were not in good agreement with available experimental observations. [31 This stimulated further theoretical work, and a martensite crystallography theory with a double lattice invariant shear was developed. [4.5,6] Although most of the studies focused on application of theories to the martensitic reactions in steels, it was pointed out [71 that the y ~ a' and the/3 ~ a' martensitic transformations in uranium alloys also provide a good opportunity for testing the crystallographic theories of martensite. The first detailed experimental investigation of the martensite in U-5 at. pct Mo alloy was performed by May, ls~ who proposed the correspondence matrix for the y-* a' transformation. Such correspondence, as well as the elements of lattice invariant shear and the lattice parameters of the parent and product, determines the data required to apply the IPS theories. Later, Crocker and Ross [7] discussed May's correspondence, comparing it with that adopted by Christian. [91 They attempted to account for the habit plane in the 3' ~ a' transformation in U-5 at. pct Mo alloy by using for the computation different possible twinning planes and directions as the elements of lattice invariant shear. However, basing their work on the assumption that only one shear system was operative, they failed to obtain a real solution. Speer and Edmonds I~~ have proposed another lattice correspondence for the 3' ~ a' transformation. In their D.
Materials Science and Engineering: A, 1996
The influence of retrogression and reaging (RR) treatment on the resistance to stress-corrosion c... more The influence of retrogression and reaging (RR) treatment on the resistance to stress-corrosion cracking of a commercial AI-Li 8090 alloy was investigated. The retrogression was performed for various times at temperatures in the range 200-260°C. The reaging treatment was carried out at 170°C. Stress corrosion tests were performed using C-ring specimens and by alte~ate immersion. Changes in the microstructure of the material near the grain boundaries were studied by transmission electron microscopy. It was shown that RR treatment substantially improved the resistance to SCC of the alloy. As with 7000 type "A1 alloys, the RR treatment brings about the dissipation of dislocations; the greater the extent of dissipation of dislocations, the greater the resistance to SCC. Another factor which, possibly, affects the sensitivity to stress-corrosion in this alloy is the presence of the 8' precipitates near the grain boundaries. The best results on SCC resistance were obtained for retrogression performed for 30 min at 260°C followed by reaging. For such treatment a zone completely free of fi' precipitates was developed near the grain boundaries.
Materials Science and Engineering: A, 2003
ABSTRACT The paper considers the stability of the phases formed in alloys of aluminum with transi... more ABSTRACT The paper considers the stability of the phases formed in alloys of aluminum with transition metals (TM) in terms of the theory of coordination compounds. The structural stability is related to the degree of distortion of the first-neighbor coordination icosahedra commonly found around TM atoms. Changes in the symmetry of coordination polyhedrons are explained in terms of the Jahn–Teller theorem. The stability of the structures may be correlated with the effective charge of the TM atom and with the electronegativity of its neighbors: the phase transforms to the structure with lower symmetry when the electronegativity or effective charge decrease.
Materials Science and Engineering: A, 1989
Abstract The submicrometre dispersoids containing iron in the aged AlLiCuMgZr alloy have been... more Abstract The submicrometre dispersoids containing iron in the aged AlLiCuMgZr alloy have been investigated by transmission electron microscopy combined with energy dispersive microprobe analysis. The dispersoids were identified as monoclinic Al 3 Fe phase. They grow as elongated plates or may appear as randomly shaped particles. They are not single crystals but consist of two (or more) small grains, thus exhibiting complex selected area diffraction patterns owing to the superposition of several reflecting zones arising from different grains.
Journal of The Electrochemical Society, 2012
We investigated the structural characteristics of Li-rich xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O... more We investigated the structural characteristics of Li-rich xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 cathode material (x around 0.5, y:z:w around 2:2:1) and its electrochemical performance in lithium cells at 30 and 60 • C. It was established that nanoparticles of the xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 compound are intergrown on the nano-scale and are built of thin plates of 40-50 Å. We demonstrated that xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 electrodes exhibited at 60 • C high capacities of ∼270 and ∼220 mAh/g at 1C and 2C rates, respectively. They can be cycled effectively at 30 and 60 • C providing capacity ∼250 mAh/g in the initial cycles, but it fades upon prolonged cycling due, to some extent, to increasing the electrode impedance (charge-transfer resistance) especially at the elevated temperature. The effective chemical diffusion coefficient of Li + in these electrodes measured during charge to 4.7 V by potentiostatic intermittent titration technique (PITT) was found to be ∼10 −10 cm 2 /s. From convergent beam electron diffraction and Raman spectroscopy studies we established, for the first time, that partial structural transition from layered-type to spinel-type ordering in xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 electrodes occurred in the initial charge to 4.7 V and even at the early stages of charging at 4.1 V-4.4 V. The thermal behavior of the xLi 2 MnO 3 • (1-x)Li[Mn y Ni z Co w ]O 2 material and electrodes are also discussed.