Most electrolyte solutions supporting highly reversible Mg deposition/dissolution contain chlorid... more Most electrolyte solutions supporting highly reversible Mg deposition/dissolution contain chlorides. These come as charged or neutral complex species, frequently as Mg-based complex ions, and Lewis-base anions. The electroactive species are usually comprised also of solvent molecules and chlorides as ligands. Numerous studies had shown the critical role of Cl-based species on the electrochemical reaction kinetics, deposition and dissolution overpotentials, electrocrystallization morphology, and many other imperative aspects of the electrochemical responses. Only very few, quite exotic and not fully studied, Cl-free electrolyte solutions have been reported to maintain reversible Mg deposition. Over the years, several compelling theories have been proposed to explain the decisive role of the Cl-containing species on the electrochemical reaction mechanisms during magnesium deposition and dissolution. The role of chlorine-based species in intercalation processes of Mg ions into crystalline hosts was seldom pursued, though. Interestingly, it appears that the Chevrel phase (CP) Mg x Mo 6 S 8 , the main benchmarking Mg intercalation compound, does not intercalate Mg in Cl-free solutions at room temperature (RT). This was established over and again during past decades and recently had been corroborated over a large set of experiments in our lab. Herein, we reveal, via experimental work, that Cl-based species also have a critical role in the electrochemical processes of intercalation. In this work, we studied the function of these during the course of the intercalation process of Mg ions into CP electrodes. We demonstrate that the intercalation process is extremely sluggish, to the point of nonexistent, from Cl-free electrolyte solutions. Quite remarkably, the addition of chlorinecomprising species opens the door to facile magnesium intercalation. On the basis of the numerous experimental results, we suggest a detailed Mg intercalation mechanism into CP. The proposed mechanism emphasizes the importance of the Cl-based species on the charge transfer process across the solid/solution interface. We propose that surface absorbed Cl-containing complexes reduce the activation energy for the interfacial charge transfer stage involving the transport of Mg ions from the solution to the crystalline phase and vice versa. We also propose a relatively simple manner to alleviate the intercalation impediment of Cl-free electrolyte solutions by the cathode's chemical or electrochemical pretreatment. This project has both scientific and applicative significance and may open a hatch for the future development of practical rechargeable Mg batteries (RMBs).
Attempts to use aluminum-based anodes in lithium-ion batteries often fail due to fast capacity fa... more Attempts to use aluminum-based anodes in lithium-ion batteries often fail due to fast capacity fading. Generally, this has been attributed to pulverization of the electrode and the large volume changes associated with the phase transformation between the crystalline α and β phases of Li-Al alloys. In this study, these transformations were investigated in aluminum films that were lithiated either electrochemically or via direct reaction with lithium metal. Scanning electron microscopy was used to image the samples at different stages of (de)lithiation. By imaging the same locations before and after each step, it can be seen that alloying between Li and Al proceeds from distinct nucleation sites. In situ and ex situ observations reveal that the α-to-β phase transformation is highly anisotropic and causes strong distortions of the film morphology, but only a relatively small amount of mechanical damage such as cracks and delamination. Comparisons between films that were lithiated to 70% and 100% of the theoretical capacity of LiAl indicate that the critical, irreversible damage is more dependent on depth of discharge than on the volume contraction caused by delithiation. Our observations challenge the pessimistic view that pulverization is unavoidable during the phase transformations of the Li-Al system.
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...
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.
Energy density is the main property of rechargeable batteries that has driven the entire technolo... more Energy density is the main property of rechargeable batteries that has driven the entire technology forward in past decades. Lithium-ion batteries (LIBs) now surpass other, previously competitive battery types (for example, lead-acid and nickel metal hydride) but still require extensive further improvement to, in particular, extend the operation hours of mobile IT devices and the driving mileages of all-electric vehicles. In this Review, we present a critical overview of a wide range of post-LIB materials and systems that could have a pivotal role in meeting such demands. We divide battery systems into two categories: near-term and long-term technologies. To provide a realistic and balanced perspective, we describe the operating principles and remaining issues of each post-LIB technology, and also evaluate these materials under commercial cell configurations.
Most electrolyte solutions supporting highly reversible Mg deposition/dissolution contain chlorid... more Most electrolyte solutions supporting highly reversible Mg deposition/dissolution contain chlorides. These come as charged or neutral complex species, frequently as Mg-based complex ions, and Lewis-base anions. The electroactive species are usually comprised also of solvent molecules and chlorides as ligands. Numerous studies had shown the critical role of Cl-based species on the electrochemical reaction kinetics, deposition and dissolution overpotentials, electrocrystallization morphology, and many other imperative aspects of the electrochemical responses. Only very few, quite exotic and not fully studied, Cl-free electrolyte solutions have been reported to maintain reversible Mg deposition. Over the years, several compelling theories have been proposed to explain the decisive role of the Cl-containing species on the electrochemical reaction mechanisms during magnesium deposition and dissolution. The role of chlorine-based species in intercalation processes of Mg ions into crystalline hosts was seldom pursued, though. Interestingly, it appears that the Chevrel phase (CP) Mg x Mo 6 S 8 , the main benchmarking Mg intercalation compound, does not intercalate Mg in Cl-free solutions at room temperature (RT). This was established over and again during past decades and recently had been corroborated over a large set of experiments in our lab. Herein, we reveal, via experimental work, that Cl-based species also have a critical role in the electrochemical processes of intercalation. In this work, we studied the function of these during the course of the intercalation process of Mg ions into CP electrodes. We demonstrate that the intercalation process is extremely sluggish, to the point of nonexistent, from Cl-free electrolyte solutions. Quite remarkably, the addition of chlorinecomprising species opens the door to facile magnesium intercalation. On the basis of the numerous experimental results, we suggest a detailed Mg intercalation mechanism into CP. The proposed mechanism emphasizes the importance of the Cl-based species on the charge transfer process across the solid/solution interface. We propose that surface absorbed Cl-containing complexes reduce the activation energy for the interfacial charge transfer stage involving the transport of Mg ions from the solution to the crystalline phase and vice versa. We also propose a relatively simple manner to alleviate the intercalation impediment of Cl-free electrolyte solutions by the cathode's chemical or electrochemical pretreatment. This project has both scientific and applicative significance and may open a hatch for the future development of practical rechargeable Mg batteries (RMBs).
Attempts to use aluminum-based anodes in lithium-ion batteries often fail due to fast capacity fa... more Attempts to use aluminum-based anodes in lithium-ion batteries often fail due to fast capacity fading. Generally, this has been attributed to pulverization of the electrode and the large volume changes associated with the phase transformation between the crystalline α and β phases of Li-Al alloys. In this study, these transformations were investigated in aluminum films that were lithiated either electrochemically or via direct reaction with lithium metal. Scanning electron microscopy was used to image the samples at different stages of (de)lithiation. By imaging the same locations before and after each step, it can be seen that alloying between Li and Al proceeds from distinct nucleation sites. In situ and ex situ observations reveal that the α-to-β phase transformation is highly anisotropic and causes strong distortions of the film morphology, but only a relatively small amount of mechanical damage such as cracks and delamination. Comparisons between films that were lithiated to 70% and 100% of the theoretical capacity of LiAl indicate that the critical, irreversible damage is more dependent on depth of discharge than on the volume contraction caused by delithiation. Our observations challenge the pessimistic view that pulverization is unavoidable during the phase transformations of the Li-Al system.
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...
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.
Energy density is the main property of rechargeable batteries that has driven the entire technolo... more Energy density is the main property of rechargeable batteries that has driven the entire technology forward in past decades. Lithium-ion batteries (LIBs) now surpass other, previously competitive battery types (for example, lead-acid and nickel metal hydride) but still require extensive further improvement to, in particular, extend the operation hours of mobile IT devices and the driving mileages of all-electric vehicles. In this Review, we present a critical overview of a wide range of post-LIB materials and systems that could have a pivotal role in meeting such demands. We divide battery systems into two categories: near-term and long-term technologies. To provide a realistic and balanced perspective, we describe the operating principles and remaining issues of each post-LIB technology, and also evaluate these materials under commercial cell configurations.
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Papers by Doron Aurbach