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Durability of high-energy throughput batteries is a prerequisite for electric vehicles to penetrate the market. Despite remarkable progresses in silicon anodes with high energy densities, rapid capacity fading of full cells with silicon–graphite anodes limits their use. In this work, we unveil degradation mechanisms such as Li+ crosstalk between silicon and graphite, consequent Li+ accumulation in silicon, and capacity depression of graphite due to silicon expansion. The active material properties, i.e. silicon particle size and graphite hardness, are then modified based on these results to reduce Li+ accumulation in silicon and the subsequent degradation of the active materials in the anode. Finally, the cycling performance is tailored by designing electrodes to regulate Li+ crosstalk. The resultant full cell with an areal capacity of 6 mAh cm−2 has a cycle life of >750 cycles the volumetric energy density of 800 Wh L−1 in a commercial cell format. The degradation in silicon-graphite anodes is originated from Li ion crosstalk between silicon and graphite, and the pressure-induced staging transition of the graphite. Here, the authors demonstrate a prismatic cell with improved volumetric energy density and cycle stability by targeted solving above issues.

For Li-ion batteries, AlF3 coating has been known to modify the over-lithiated layered oxide (OLO) cathodes to produce stable cathodes, but during synthesis procedure, the environment of excess amount of Li metal and free-exposed oxygen may cause the formation of Al2O3 and LiF materials, separately. We investigated the possibility of separated coating formation of Al as Al2O3 and F as LiF from AlF3 using density functional theory calculation, which suggests a favorable binding affinity of both Al2O3 and LiF phases to the OLO surface to support the preferable formation of coating layer of Al2O3 and LiF. Meanwhile, we found the well-distributed surface modification with the coating layers and a small amount of AlF3 (

The phase diagram of the Li–Ni–Co–Mn layered oxide pseudoquaternary system is used as starting point to elucidate the influence of transition metal (TM) ordering on the structures and electrochemistry of positive electrode materials with LiNi1–y–xCoyMnxO2 composition. Whereas our obtained phase diagram shows a comprehensive search of the most suitable target compositions for single-phase layered materials with large structural stability and reversible capacity, a detailed analysis of the transition metal ordering tries to fill the gap existing in the literature between transition metal composition and ordering, showing the effect on the electrochemical performance. Our results demonstrate that, in order to achieve high reversible capacities, control of the TM arrangement at the atomic scale seems to be crucial to enhance both ionic and electronic mobilities, thus maximizing the rate capability and structural stability during cycling.

To meet the requirement of large-scale simulation technics for Li-ion battery electrode materials, we introduce the charge-transfer modified embedded-atom method (CT-MEAM) in which the complex nature of the chemical bonding in transition metal (TM) oxides is described as a balance between metallic/covalent and ionic contributions by MEAM and a variable-charge model, respectively. The method is applied to Li 2 MnO 3 , and the parameterization is performed through fitting the energy–strain curves of Li 2 MnO 3 under uniaxial, biaxial and hydrostatic strains to a training set from ab initio density-functional theory calculations. The CT-MEAM prediction of the critical physical properties such as charge states and redox potentials match quite well with the ab initio results in various Li–Mn–O compounds beyond Li 2 MnO 3 . The constructed Li–Mn–O phase diagram is also qualitatively consistent with the ab initio reference work. The excellent transferability ensures use of the present method for a wide range of oxidation states in complex ternary TM oxides. Therefore, it will facilitate large-scale atomistic calculations required for the optimal design of many TM oxide applications including lithium-ion battery cathode materials.

Doping is the most common strategy to suppress the intrinsic structural instability of several families of cathode materials, thus improving their electrochemical performance. During the electrode synthesis, the dopants have a low probability to occupy cationic Li sites, but it is well-known that, during the normal operation of the battery, such probability increases via inter- or intralayer diffusion. In this work, we investigate the effect of 10 Li-site cationic dopants (Mg, Ti, V, Nb, Fe, Ru, Co, Ni, Cu, Al) on the electrochemical properties of Li2MnO3 and LiMnO2 cathode materials using density functional theory. Our results show that, although Mn sites are thermodynamically favorable over Li-site doping, the small thermodynamic barriers between both configurations can be easily overcome during the material synthesis and/or the extraction/insertion of Li during the cycling process of the battery. Also, due to charge balance and diffusion channel opening, some of the Li-site dopants were found to act as...

Thermal stability is one of the critical requirements for commercial operation of high energy lithium-ion batteries. In this study, we use in situ X-ray diffraction technique to elucidate the thermal degradation mechanism of 0.5Li 2 MnO 3 -0.5LiNi 0.33 Co 0.33 Mn 0.33 O 2 lithium rich cathode material in the absence and presence of electrolyte to simulate the real life battery conditions and compare its thermal behavior with the commercial LiNi 0.33 Co 0.33 Mn 0.33 O 2 cathode material. We show that the thermal induced phase transformations in delithiated lithium rich cathode material are much more intense compared to similar single phase layered cathode material in the presence of electrolyte. The structural changes in both cathode materials with the temperature rise follow different trends in the absence and presence of electrolyte between 25 and 600 °C. Phase transitions are comparatively simple in the absence of electrolyte, the fully charged lithium rich cathode material demonstrates better thermal stability by maintaining its phase till 379 °C, and afterwards spinel structure is formed. In the presence of electrolyte, however, the spinel structure appears at 207 °C, subsequently it transforms to rock salt type cubic phase at 425 °C with additional metallic, metal fluoride, and metal carbonate phases.

Due to a high voltage of 4.6 V and large practical capacity of ~260 mAh/g, the over-lithiated-oxides (OLOs) which are often represented as Li2MnO3·LiMO2 (M = Mn, Co, Ni), have been intensely investigated as a promising candidate of the next generation cathode materials for Li-ion battery. The Li2MnO3 composite structure plays an important role in providing high capacity and phase stability to the system. However, during cathode charge-discharge operation, Li2MnO3 is unstable and partly transforms into LiMnO2, indicating that the phase used in practice has mixed both Li2MnO3 and LiMnO2. In this work, the effects of Li-site doping from 10 cationic dopants (Mg, Ti, V, Nb, Fe, Ru, Co, Ni, Cu, Al) on the electrochemical properties of both oxides are studied using density functional theory. The calculations show that, comparing with the Mn-site doped phases, Li-site doping is thermodynamically unstable for the ground states, but the small transition barriers can be easily overcome under high thermal fluctuations during the realistic cathode synthesis process. The redox potentials of both oxides can be lowered by most of the Li-site dopants. For example, Nb strongly lowers the redox potential of the LiMnO2 phase, and Ru shows an unexpected effect on the Li2MnO3 phase: it activates the Li atoms in the Li-layer and, at the same time, it immobilizes the Li atoms in the Li-Mn mixed-layer by increasing the redox potential. These results support the experimental observations about Li-site doping and provide an explanation about the effects of Li-site doping on the electrochemical properties.

For the over-lithiated-oxides (OLOs), a composite of layered Li2MnO3 and LiMO2 (M = Mn, Co, Ni), the Li2MnO3 part is not stable after the 1st charge–discharge cycle and partly transforms into layered LiMnO2, which in practice indicates that the phase used is actually a mixture of both Li2MnO3 and LiMnO2. In the present work, the influence of 10 cationic (Mg, Ti, V, Nb, Fe, Ru, Co, Ni, Cu, and Al) and 2 anionic (N and F) dopants on the phase stability, redox potential, ionic and electronic conductivity of both Li2MnO3 and LiMnO2 is investigated in detail using density functional theory. The calculations show that all the cationic dopants and F can be thermodynamically stable in the layered structures. The redox potential of both oxides is quite sensitive to some of the dopants, like V, Nb, and Ru, due to the appearance of gap states introduced by those dopants. The Jahn–Teller effect has a strong influence on the Li vacancy diffusion behavior in both LiMnO2 and its doped phases. Li vacancy diffusion behavior in Li2MnO3, including both interlayer and intralayer pathways, is relatively more complex and some dopants like Mg, Ti, Nb, and Ru can decrease the barriers of the diffusion paths. The calculations also show the evidence of hole polaron formation in LiMnO2 and electron polaron formation in Li2MnO3 which should be the reason why these phases have low electronic conductivities. Based on these findings, possible ways to improve the electronic conductivity through the doping process are discussed.

Electrochemically active Li 2 MnO 3 nanoparticle dispersed on carbon nanotube (CNT) network has been successfully synthesized by microwave-assisted hydrothermal (MAH) process. To the best of our knowledge, this is the first report showing the formation of Li 2 MnO 3 nanoparticle on CNT network using MnO 2 -coated CNT composite. Appearance of superlattice peak in X-ray diffraction (XRD) pattern and Raman-active modes near the lower wavelength region of Raman spectra reveals the structure transition from spinel LiMn 2 O 4 to layered-type Li 2 MnO 3 phase. The X-ray absorption near edge spectra (XANES) shows increase in average oxidation state of Mn ion from 3.5+ to 4+, and Mn–O and Mn–Mn peak intensity variations observed from extended X-ray absorption fine structure (EXAFS) are well evidenced for the formation of ordered Li 2 MnO 3 structure. Electrochemical performance of Li 2 MnO 3 nanocomposite electrode material prepared from higher LiOH concentration shows much higher capacity than spinel component alone. This synthetic strategy opens a new way for effective synthesis of electrochemically active Li 2 MnO 3 on CNT network, making it suitable for advanced lithium ion battery.

A new synthetic method using biotemplating for fabrication of LiCoO2 (LCO) for batteries of mobile products is developed. The LCO can be manufactured in various forms, and rapidly charged and discharged, even when using a thick electrode. Among three types of candidate biotemplates wood, cotton, and grass pollen, cotton was selected as the biotemplate considering its performance and potential for commercialization. Both the size of the primary particle and the shape of the secondary particle are controllable by using cotton. When using a thin electrode, the difference in capacitance between the LCO fabricated by the general method (solid-LCO) and the LCO made by using cotton (cotton-LCO) is within 3%, regardless of current density. On the other hand, the capacity difference in the case of a thick electrode between two samples is approximately 1.5 times higher than that observed for solid-LCO at very high current density (6C). The capacity retention values are 1.4% and 75.1% at 6C after the 100th cycle for solid-LCO and cotton-LCO, respectively. The superior performance at high current density for the cotton-LCO likely arises from decreasing the distance that the Li+ ion must diffuse in the solid-state by connected nanoparticles.

Direct internal pressure measurements of the cylindrical Li-ion cells with a mixture of LiCoO 2 and Li 1.167 Ni 0.233 Co 0.1 Mn 0.467 Mo 0.033 O 2 (a solid solution between 0.4 Li 2 Mn 0.8 Ni 0.1 Mo 0.1 O 3 and 0.6 LiNi 0.4 Co 0.2 Mn 0.4 O 2 ) as cathode and graphite as anode have been performed during cell charging. Cell internal pressure at the end of charging is greatly reduced from 2.85 to 0.84–1.84 bar by adding a small amount of phosphorus derivatives such as triphenyl phosphine (TPP), ethyl diphenylphosphinite (EDP), and triethyl phosphite (TEP) into a carbonate-based electrolyte. The phosphorus derivatives are supposed to react with O 2 generated from the decomposition of the Li 2 MnO 3 component. The chemical states of additive molecules before and after the charging process have been characterized with a nuclear magnetic resonance (NMR) spectroscopy and gas chromatography–mass spectrometry (GC–MS). It has also been shown that those additives improve the cycle life when applied in coin full cells.

The real time detection of quantitative oxygen release from the cathode is performed by in-situ Gas Chromatography as a tool to not only determine the amount of oxygen release from a lithium-ion cell but also to address the safety concerns. This in-situ gas chromatography technique monitoring the gas evolution during electrochemical reaction presents opportunities to clearly understand the effect of surface modification and predict on the cathode stability. The oxide cathode, 0.5Li2MnO3∙0.5LiNi0.4Co0.2Mn0.4O2, surface modified by amorphous cobalt-phosphate nanoparticles (a-CoPO4) is prepared by a simple co-precipitation reaction followed by a mild heat treatment. The presence of a 40 nm thick a-CoPO4 coating layer wrapping the oxide powders is confirmed by electron microscopy. The electrochemical measurements reveal that the a-CoPO4 coated overlithiated layered oxide cathode shows better performances than the pristine counterpart. The enhanced performance of the surface modified oxide is attributed to the uniformly coated Co-P-O layer facilitating the suppression of O2 evolution and offering potential lithium host sites. Further, the formation of a stable SEI layer protecting electrolyte decomposition also contributes to enhanced stabilities with lesser voltage decay. The in-situ gas chromatography technique to study electrode safety offers opportunities to investigate the safety issues of a variety of nanostructured electrodes.

Lateral meniscus allograft transplantation (LMAT) is a feasible surgical option for young meniscus-deficient patients. Although several studies have explored the factors that contribute to graft extrusion, they have not been fully elucidated. The aim of this study was to determine the various factors that contribute to graft extrusion. Patients with knees that had received LMAT using a keyhole technique (n = 87 knees in 82 patients) were reviewed. The median age of these patients was 22 years (range 19–54 years), and the median postprocedural follow-up interval was 5 days (range 1–136 days). Twelve magnetic resonance imaging (MRI) measurement parameters (axial and coronal location of the bone block) that could potentially influence graft extrusion were evaluated, along with absolute graft extrusion and relative percentage of extrusion (RPE). A significant correlation was found between 8 of the 12 MRI measurement parameters and both the absolute extrusion and RPE (r = 0.241–0.438, p

In this work, we present a density-functional theory (DFT) investigation of the phase stability, electrochemical stability and phase transformation mechanisms of the layered and over-lithiated Mn oxides. This study includes the thermodynamic stability of Li and oxygen vacancies, to examine the electrochemical activation mechanisms of these cathode materials. The DFT calculations provide phase diagrams of the Li-Mn-O system in both physical and chemical potential spaces, including the crystals containing vacancies as independent phases. The results show the ranges of electrochemical activity for both layered LiMnO2 and over-lithiated Li2MnO3. By using a thermodynamic model analysis, we found that the required temperature for oxygen evolution and Li vacancy formation is too high to be compatible with any practical synthesis temperature. Using solid-state transition calculations, we have identified the key steps in the phase transition mechanism of the layered LiMnO2 into the spinel phase. The calculated effects of pH on the Li-Mn-O phase stability elucidated the mechanism of Mn(2+) formation from the spinel phase under acidic conditions.

Recently, composite layered material between Li2MnO3 and LMO2 (where M= Mn, Co, Ni), also known as the lithium rich cathode material, has received pronounced attention and has been considered as promising cathode materials due to their high discharge capacity of ~250 mAh g-1 . However, there are several intrinsic problems associated with this material family that need to be solved; e.g., the voltage as well as the capacity decay during cycling, the high irreversible capacity loss in the first cycle, poor rate capability, and oxygen release during cycling, in order to adopt these materials in practical cells. Thermal stability is another challenge which could greatly impact the safety of lithium-ion batteries. In this study, we use in situ X-ray diffraction technique to elucidate the thermal degradation mechanism of 0.5Li2MnO3-0.5LiNi0.33Co0.33Mn0.33O2 lithium rich cathode material in the absence and presence of electrolyte to simulate the real life battery conditions and compare its thermal behavior with the commercial LiNi0.33Co0.33Mn0.33O2 cathode material. We show that the thermal induced phase transformations in delithiated lithium rich cathode material are much more intense compared to similar single phase layered cathode material in the presence of electrolyte.

Lithium-ion batteries were introduced in 1990 by Sony Corporation. Since its successful debut, various transition metal oxides have been synthesized and investigated as new lithium ion battery electrode materials to fulfill the ever demanding high capacity requirements. Recently, composite layered material between Li2MnO3 and LMO2 (where M= Mn, Co, Ni), also known as the lithium rich cathode material, has received pronounced attention and has been considered as promising cathode materials due to their high discharge capacity of ~250 mAh g-1 [1]. However, there are several intrinsic problems associated with this material family that need to be solved; e.g., the voltage as well as the capacity decay during cycling, the high irreversible capacity loss in the first cycle, poor rate capability, and oxygen release during cycling, in order to adopt these materials in practical cells [2–4]. Thermal stability is another challenge which could greatly impact the safety of lithium-ion batteries, however it has received little attention unlike the widely studied electrochemical performance and reaction mechanism of this material. In this study, we use in situ X-ray diffraction technique to elucidate the thermal degradation mechanism of 0.5Li2MnO3-0.5LiNi0.33Co0.33Mn0.33O2 lithium rich cathode material in the absence and presence of electrolyte to simulate the real life battery conditions and compared its thermal behavior with the commercial LiNi0.33Co0.33Mn0.33O2 cathode material. We show that the thermal induced phase transformations in delithiated lithium rich cathode material are much more intense compared to similar single phase layered cathode material in the presence of electrolyte. The structural changes in both cathode materials with the temperature rise follow different trends in the absence and presence of electrolyte between 25-600 °C. Phase transitions are comparatively simple in the absence of electrolyte, the fully charged lithium rich cathode material demonstrates better thermal stability by maintaining its phase till 379 °C, and afterwards spinel structure is formed. Whereas in the presence of electrolyte, the spinel structure appears at 207 °C, subsequently it transforms to rock salt type cubic phase at 425 °C with additional metallic, metal fluoride, and metal carbonate phases. More detailed discussion will be presented at the time of meeting. [1] M.M. Thackeray, S.-H. Kang, C.S. Johnson, J.T. Vaughey, R. Benedek, S.A. Hackney, J.Mater. Chem. 17 (2007) 3112. [2] Y. Li, M. Bettge, B. Polzin, Y. Zhu, M. Balasubramanian, D.P. Abraham, J. Electrochem.Soc. 160 (2013) A3006. [3] A.R. Armstrong, M. Holzapfel, P. Novák, C.S. Johnson, S.-H. Kang, M.M. Thackeray,P.G. Bruce, J. Am. Chem. Soc. 128 (2006) 8694. [4] X. Yu, Y. Lyu, L. Gu, H. Wu, S.-M. Bak, Y. Zhou, K. Amine, S.N. Ehrlich, H. Li, K.-W.Nam, X.-Q. Yang, Adv. Energy Mater. 4 (2014) 1614.

Thin and uniform carbon coated overlithiated layer oxide (OLO) using 2,3-dihydroxynaphthalene (DN) is prepared. The pristine and DN coated samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). An amorphous nanolayer coating of carbon is obtained on the surface of layered pristine material. The coating layer was confirmed by TEM analysis. The thickness of coating layer was approximately 5 nm, when the content of DN coating was 0.2 wt.%. For optimization of coating condition, the coating weight and the temperature of heat treatment was changed. The 0.1wt% DN coated OLO which was heated at 500oC exhibits the improved electrochemical performance. The initial discharge capacity of 202 mAh·g−1 is obtained at 1C. This capacity is larger of 2% than that of bare OLO. The capacity retention (93.9% at 50th cycle) is also maintained compared to bare OLO (92.3% at 50th cycle). The average voltage drop of coated OLO showed 20mV lower than that of bare sample after 50th cycle. The thin and uniform carbon layer leads to improvement of kinetic and protection of direct contact between cathode and electrolyte. References 1. N. Yabuuchi, K. Yoshii, S. Myung, I Nakai, S. Komaba, J. Am. Chem. Soc. 2011, 133, 4404-4419 2. T. Kwon, H. Nishihara, Y. Fukura, K. Inde, N. Setoyama, Y. Fukushima, T. Kyotani, Figure 1

The over-lithiated-oxides (OLOs), a composite of layered structures of Li2MnO3 and LiMO2 (M = Mn, Fe, Co, Ni), have shown much higher storage capacity than the traditional layered oxides for Li ion battery cathode because of the Li2MnO3 phase. However, Li2MnO3 is not stable after the 1st charge-discharge cycle and will partly transform into layered LiMnO2, which indicates that the practically used phase is a mixture of both Li2MnO3 and LiMnO2. During the subsequent cycles, the OLO voltage decreases due to the phase transition of layered LiMnO2 into spinel. Experimentally, the effective dopants satisfying multiple cathode materials requirements of thermodynamic stability, optimized voltage and improved kinetics based on ionic and electronic conductivities are investigated to overcome the voltage degradation and to improve the power capacity. In this work, redox potential, lithium ion diffusion and charge carrier transportation of both phases are examined in details using the ab initio density-functional theory (DFT) simulations. The calculations find, due to the Jahn-Teller effect of Mn3+ atoms, Li vacancy migration in LiMnO2 has special behaviors and hole polaron and electron polaron will form in LiMnO2 and Li2MnO3 phases, respectively. Based on the understanding of the pure phase properties, the effects of 10 cationic (Mg, Ti, V, Nb, Fe, Ru, Co, Ni, Cu, Al) and 2 anionic (N, F) dopants on the redox potential, ionic and electronic conductivity are investigated. These DFT findings could provide conceptual guidance in the experimental search for the effective dopants enabling the practical application of OLO cathodes. This work was supported by Samsung GRO project.

The over-lithiated-oxides (OLOs) are a composite material of layered structures of Li2MnO3 and LiMO2 (M = Mn, Fe, Co, Ni). Their main advantage over current layered oxides is that they show much higher storage capacity as cathode material for Li-ion batteries, due to the presence of Li2MnO3 phase. However, experimental results indicate that Li2MnO3 is an almost inert material from an electrochemical point of view, and that it partially transforms into layered LiMnO2 after the first charge/discharge cycle, thus forming a phase that is a mixture of both Li2MnO3 and LiMnO2. During the subsequent charging cycles, OLO capacity is known to reduce gradually in connection with Mn spinel phase formation. To improve the OLO cathode material performance, it is desirable to suppress such spinel phase formation. In order to address the stability of Mn layered oxides, we have examined the phase diagram of the Li-Mn-O system on both physical and chemical (as a function of two chemical potentials, μ(Li) and μ(O)) potential space, using ab initio density-functional theory (DFT) simulations. These DFT findings will provide conceptual guidance in the experimental search for the mechanisms driving the structural transformation into the spinel phase, in an attempt to solve such structural instability problem and, thus, improving the performance of the OLO cathode materials. This work was supported by Samsung GRO project.

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Mo doped Li excess transition metal oxides formulated as 0.3Li[Li(0.33)Mn(0.67)]O(2)·0.7Li[Ni(0.5-x)Co(0.2)Mn(0.3-x)Mo(2x)]O(2) were synthesized using the co-precipitation process. The effects of the substitution of Ni and Mn with Mo were investigated for the density of the states, the structure, cycling stability, rate performance and thermal stability by tools such as first principle calculations, synchrotron X-ray diffraction, field-emission SEM, solid state (7)Li MAS nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), elemental mapping by scanning TEM (STEM), inductively coupled plasma atomic emission spectrometry (ICP-AES) and a differential scanning calorimeter (DSC). It was confirmed that high valence Mo(6+) doping of the Li-excess manganese-nickel-cobalt layered oxide in the transition metal enhanced the structural stability and electrochemical performance. This increase was due to strong Mo-O hybridization inducing weak Ni-O hybridization, which may reduce O(2) evolution, and metallic behavior resulting in a diminishing cell resistance.

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