High Capacity Utilization Research Articles

A high-performance Te@CMK-3 composite negative electrode for Na rechargeable batteries

We report a new class of high-capacity chalcogen–carbon composite negative electrodes for Na rechargeable batteries, consisting of tellurium-infiltrated ordered mesoporous carbon CMK-3. Its unparalleled electric conductivity makes Te a promising electrode material with high-capacity utilization. The rechargeable cell Na/Te@CMK-3, using a carbonate-based electrolyte, exhibited a large stable capacity of ~ 320 mA h (g-Te)−1 at 0.2 C with an excellent rate capability (55% of the theoretical specific capacity at 2 C-rate), and long-term cyclability (> 500 cycles), as well as 100% coulombic efficiency. Our study evidences the great potential of mesoporous carbon-encapsulated Te materials concepts as a new class of high-performance chalcogen-based electrode materials for Na rechargeable batteries.

Dynamic airspace sectorisation for flight-centric operations

Today’s air traffic operations follow the paradigm of ‘flow follows structure’, which already limits the operational efficiency and punctuality of current air traffic movements. Therefore, we introduce the dynamic airspace sectorisation and consequently change this paradigm to the more appropriate approach of ‘structure follows flow’. The dynamic airspace sectorisation allows an efficient allocation of scarce resources considering operational, economic and ecological constraints in both nominal and variable air traffic conditions. Our approach clusters traffic patterns and uses evolutionary algorithms for optimisation of the airspace, focusing on high capacity utilisation through flexible use of airspace, appropriate distribution of task load for air traffic controllers and fast adaptation to changed operational constraints. We thereby offer a solution for handling non-convex airspace boundaries and provide a proof of concept using current operational airspace structures and enabling a flight-centric air traffic management. We are confident that our developed dynamic airspace sectorisation significantly contributes to the challenges of future airspace by providing appropriate structures for future 4D aircraft trajectories taking into account various operational aspects of air traffic such as temporally restricted areas, limited capacities, zones of convective weather or urban air mobility. Dynamic sectorisation is a key enabling technology in the achievement of the ambitious goals of Single European Sky and Flightpath 2050 through a reduction in coordination efforts, efficient resource allocation, reduced aircraft emissions, fewer detours, and minimisation of air traffic delays.

Lithium–Iron (III) Fluoride Battery with Double Surface Protection

AbstractLithium–metal fluoride batteries promise significantly higher energy density than the state‐of‐the‐art lithium‐ion batteries and lithium–sulfur batteries. Unfortunately, commercialization of metal fluoride cathodes is prevented by their high resistance, irreversible structural change, and rapid degradation. In this study, a substantial boost in metal fluoride (MF) cathode stability by designing nanostructure with two layers of protective shells—one deposited ex situ and the other in situ is demonstrated. Such methodology achieves over 90% capacity retention after 300 charge–discharge cycles, producing the first report on FeF3 as a cathode material, where a very high capacity utilization in combination with excellent stability is approaching the level needed for practical applications of FeF3. The cathode solid electrolyte interphase (CEI) containing lithium oxalate and BF bond containing anions is found to effectively protect the cathode material from direct contact with electrolytes, thus greatly suppressing the dissolution of Fe. Quantum chemistry and molecular dynamics calculations provide unique insights into the mechanisms of CEI layer formation. As a result, this work not only demonstrates unprecedented performance, but also provides the reader with a better fundamental understanding of electrochemical behavior of MF cathodes and the positive impact observed with the application of a lithium bis(oxalato)borate salt in the electrolyte.

Exploration of the Evolution of Airport Ground Delay Programs

This study introduces a novel method of merging disparate but complementary datasets and applying machine learning techniques to ground delay program (GDP) data. More specifically, it aims to characterize GDPs with respect to changing weather forecasts, GDP plan parameters, and operational performance. The analysis aims to gain insights into GDP usage patterns (implementation and revisions), with respect to these key dimensions. It also aims to gain insights into how GDP cancelations and revisions correlate with operational efficiency and predictability. The results could be used to help traffic managers and air carriers understand complex patterns in the evolution of GDPs, so that they might, for example, better anticipate or even plan a response to a change in weather conditions. The focus is on GDPs at Newark Liberty International Airport (EWR), from 2010 through 2014. A master dataset was generated by merging several datasets on GDPs, weather forecasts, and individual flight information. Several scenarios of GDP evolution were then identified by reducing the dimensionality of the master GDP dataset, then applying cluster analysis on the lower dimensional data. It was found that GDPs at EWR can be categorized into 10 types based on weather forecasts, realized weather, GDP scope, arrival rates, and duration. The characteristics of these 10 GDP clusters were further explored by examining the relationships between GDP scenarios and their performance. It was found that GDPs under stable, low-severity weather and with large scope may score higher on the efficiency metric than expected. When GDPs called in the same weather conditions have high program rates, medium durations, and narrow scopes, capacity utilization was higher than expected—less affected flights lead to fewer cancelations and more arrivals (albeit delayed), and therefore, higher capacity utilization. Results also suggest that program rates are set more conservatively than needed for some poor weather conditions that end earlier than expected. GDPs with fewer revisions were associated with a higher predictability score but lower efficiency score. These findings can provide greater insights and knowledge about GDPs for future planning purposes. More specifically, the findings could, for example, be used to support discussion around, or even future guidance regarding, how to set and adjust GDP program rates. In future work additional data could be utilized to provide a more comprehensive operational picture of GDPs, and a wider range of performance metrics could be considered. It is also recommended that the patterns of how GDPs evolve over their lifetimes be further explored using other machine learning techniques that may provide new and useful insights.

Self-Stabilized Solid Electrolyte Interface on a Host-Free Li-Metal Anode toward High Areal Capacity and Rate Utilization

Lithium metal has long been regarded as a promising anode for its high energy density and low reduction potential. However, infinite volume change and undesired lithium dendrite and parasitic reactions still block the practical application of lithium-metal anodes, despite persistent research. To address these tough issues, a self-stabilized solid electrolyte interface (SEI) formed in lithium bis(trifluoromethane sulphonyl)imide-vinylene carbonate electrolyte with high ionic conductivity, mechanical strength, and compact structure is reported for the first time, delivering rapid lithium-ion diffusion and suppressed anode/electrolyte interfacial reactions. This excellent SEI contributes to homogeneous lithium plating/stripping and a constant voltage over 4000 h even under harsh conditions. High rate performance with a current density of 20 mA cm–2 and an areal capacity of 40 mA h cm–2 has also been achieved. The self-stabilized SEI provides a promising strategy to tackle the challenges raised by the intrins...

Spontaneous repairing liquid metal/Si nanocomposite as a smart conductive-additive-free anode for lithium-ion battery

Silicon is a promising candidate for negative electrodes due to its high theoretical specific capacity (~ 3579 mA h g−1) and low lithiation potential (~ 0.40 V vs. Li). However, its practical applications in battery have been inhibited by the large volume change (~ 400%) induced by Li+-insertion into Si lattices. Here, we attempt to resolve this issue at a fundamental level, and report for the first time a novel liquid metal (LM)-mediated spontaneous repairing conductive-additive-free Si anode for Li-ion battery. The fluidity of LM ensures the eternal contact between Si and the conducting-network during its repeated electrochemical reactions. The as-prepared nano-composite of LM/Si leads to superior performances as characterized by high capacity utilization (2300 mA h g−1 at 500 mA g−1), long-term stability (968 mA h g−1 after 1500 charge-discharge cycles at 8 A g−1 with 81.3% retention), high rate capability (360 mA h g−1 at 20 A g−1, equivalence of 55 C, or full charge/discharge in 65 s), and, in particular, an extra-ordinarily high initial coulombic efficiency (95.92%), which is not only the highest reported for Si to the best of our knowledge, but also higher than the mature graphitic carbon anodes. The unique approach described in this work not only resolves the basic stress challenges faced by the promising but often problematic alloy-type materials; in broader context it also provides a universal inspiration to all electrode materials whose electric properties suffer from extreme mechanic upheavals induced by the electrochemical strains during the cell reactions.

Analytical Model for Predicting the Discharge Performance of Thick Battery Electrodes

There is an increasing interest in using thick electrodes in Li-ion batteries to improve the energy density and lower the cost by reducing the amount of inactive components. However, increasing electrode thickness usually leads to inferior rate performance. Currently there lacks a quantitative understanding of the trade-off between the power and energy density for thick electrodes, which is essential for optimizing electrode structures for specific applications and developing novel thick electrode designs. Addressing this deficiency, here we present a simple and yet accurate analytical model for predicting the discharge performance of battery cells containing thick electrodes. Compared to the traditional porous electrode simulations, this model offers a more transparent understanding of the kinetic limitations of thick electrode configurations and the effects of various cell-level structural parameters on battery performance. Computation-wise, the model is substantially more efficient than the numerical pseudo-2D discharge simulation, and provides a powerful tool for performing the optimization of thick electrodes within the multi-dimensional design space. Our model is motivated by two important observations from numerical simulations and experiments, namely, the capacity utilization of thick electrodes is limited by electrolyte transport and a pseudo-steady state of electrolyte transport is established during discharge. Accordingly, we derived analytical expressions for the electrolyte distribution across the electrode and the discharge capacity at termination based on the steady state assumption. As shown in Figure 1a, the predicted distribution of Li ion concentration in electrolyte agrees well with the numerical simulation. The depth of discharge (DoD) calculated from the analytical model provides excellent approximations to the simulation results for various electrode thickness and cell configurations (half vs full cells) without any adjustable parameters, Figure 1b. This model is generally applicable to electrodes that display solid-solution intercalation behavior such as the layer oxide cathodes paired with the graphite anode at low to moderately high discharge rates. An important insight we obtained from the analytical model is that the discharge capacity of half and full cells exhibit qualitatively different scaling relation with electrode thickness and discharge current. As such, the half cell configuration with Li metal anode exhibits markedly improved DoD at large electrode thickness over full cells containing the graphite anode. This finding explains the seemingly scattered results from various thick electrode experiments reported in literature. It cautions against the practice of using the half cell testing as an indicator of the rate performance of full cells with thick electrodes. On the other hand, it suggests that the combination of a thick cathode with a high capacity anode such as Li metal, silicon and tin is an effective strategy to enable thick electrode designs with higher capacity utilization. Figure 1: a) Li ion concentration distribution in electrolyte during discharge calculated from the porous electrode simulation (solid lines) and steady-state analytical model (dashed line). Figure 1

Evaluation of Continuous Membrane Chromatography Concepts with an Enhanced Process Simulation Approach.

Modern biopharmaceutical products strive for small-scale, low-cost production. Continuous chromatography has shown to be a promising technology because it assures high-capacity utilization, purity and yield increases, and lower facility footprint. Membrane chromatography is a fully disposable low-cost alternative to bead-based chromatography with minor drawbacks in terms of capacity. Hence, continuous membrane chromatography should have a high potential. The evaluation of continuous processes goes often along with process modeling. Only few experiments with small feed demand need to be conducted to estimate the model parameters. Afterwards, a variety of different process setups and working points can be analyzed in a very short time, making the approach very efficient. Since the available modeling approaches for membrane chromatography modules did not fit the used design, a new modeling approach is shown. This combines the general rate model with an advanced fluid dynamic distribution. Model parameter determination and model validation were done with industrial cell cultures containing Immunoglobulin G (IgG). The validated model was used to evaluate the feasibility of the integrated Counter Current Chromatography (iCCC) concept and the sequential chromatography concept for membrane adsorber modules, starting with a laboratory-type module used for sample preparation. A case study representing a fed-batch reactor with a capacity from 20 to 2000 L was performed. Compared to batch runs, a 71% higher capacity, 48.5% higher productivity, and 38% lower eluent consumption could be achieved.

Operational safety: The hidden cost of supply-demand mismatch in fashion and textiles related manufacturers

Inventory management is a focus for operations management scholars and operations managers. Previous literature mainly investigated the relations between firm's inventory and financial performance. However, the relation between firm's inventory and non-financial performance (e.g., social outcome) is less clear. This study takes a fresh perspective to examine the impacts of supply-demand mismatch on firm's safety performance. Based on a sample set from fashion and textiles related manufacturers, the analysis suggests that supply-demand mismatch (measured by inventory volatility) associates with a higher likelihood of safety incidents. The impact is more salient where the firms are operating in complex (labour intensive) and tightly coupled (high production capacity utilization) environments. This study provides significant contributions to the inventory management literature, occupational health and safety management literature and operational managers.

Productivity and Unemployment in Nigeria

Productivity and employment are issues that are central to the social and economic life of every country. The extant literature refers to productivity and unemployment as constituting a vicious circle that explains the endemic nature of poverty in developing countries. And it has been argued that continuous improvement in productivity is the surest way to breaking this vicious circle. Growth in productivity provides a significant basis for adequate supply of goods and services thereby improving the welfare of the people and enhancing social progress. As pointed out by Dernburg (1985:63), Without it there would be no growth in per capita income, and inflation control would be all the more difficult. In fact, the observation has been made that continuous enhancement of productivity has been very central to the brilliant performance of the Asian Tigers and Japan in recent years (Simbeye, 1992; World Bank 1993). Recent developments in the world economy have also shown that countries with high productivity are not only central to the determination of global balance of powers (e.g Japan and Germany), but also serve as centres of stimulus, where world resources (including labour) are redirected to, as opposed to countries with low or declining productivity. Recent studies, for example, Rensburg and Nande (1999) and Roberts and Tybout (1997) have also shown that high productivity increases competitiveness in terms of penetrating the world market. Thus, a country with high productivity is often characterized by a very high capacity utilization (optimal use of resources), high standard of living, low rate of unemployment and social progress. Unemployment, on the other hand, has been categorized as one of the serious impediments to social progress. Apart from representing a colossal waste of a country's manpower resources, it generates welfare loss in terms of lower output thereby leading to lower income and well-being (Akinboyo, 1987; and Raheem, 1993). Unemployment is a very serious issue in Africa (Vandemoortele, 1991 and Rama, 1998) and particularly in Nigeria (Oladeji, 1994 and Umo, 1996). The need to avert the negative effects of unemployment has made the tackling of unemployment problems to feature very prominently in the development objectives of many developing countries. Incidentally, most of these countries' economies are also characterized by low productivity. Thus, it seems obvious to many policy makers that there must be a straight forward connection between productivity and employment/unemployment. However, the theoretical linkage between productivity and unemployment is yet to be settled in the literature. While some researchers posit that higher productivity may increase unemployment (e.g. Diachavbre, 1991; Krugman, 1994), some others argue that it could increase employment (e.g Yesufu, 1984; Akerele, 1994; CEC, 1993).

Republic of Lithuania: 2018 Article IV Consultation - Press Release; Staff Report; and Statement by the Executive Director for the Republic of Lithuania

This 2018 Article IV Consultation highlights that the economy of Lithuania picked up steam in 2017, following two years of sluggish growth. Real GDP expanded by 3.9 percent largely because of the acceleration of investment, which benefited from credit growth and high capacity utilization. Private consumption remained the main engine of growth, though it was held back by decelerating real wages. The external current account swung to a modest surplus with exports benefiting from past investments in export capacity and improved external demand. Growth in 2018 is projected at 3.2 percent, mainly because of weaker exports after a very strong performance in 2017 and a slowdown of consumption driven by negative employment growth.

Cancellation of delayed trains: passengers’ and capacity points of view

The paper is focused on interface between passenger transport demand after utilization of individual trains influenced by current operational situation (delays, overtaking of trains etc.) and on aspects of capacity utilization of railway line. The research is inspired by an idea (based on UIC 406) to operate rush lines on higher level of capacity utilization due to possibility to cancel delayed trains and make the time schedule more stable in this way. Simulation model of distribution of passengers between trains according to current operational situation is modified and applied for this assessment. The main result is that the effectiveness of this measure (especially in passengers’ point of view) is depended not only on high capacity utilization of railway line, but also on time schedule and a complex of other operational conditions.

From Atoms to Applications and Back

Using lithium metal as the anode in high-energy-density cells remains a highly pursued goal of the battery community, but practical use currently remains out of reach. Described recently in Nano Letters and Science, two teams led by Shirley Meng and Yi Cui, respectively, have developed new capabilities to image cycled lithium metal anodes using cryo-electron microscopy to gain valuable atomic-scale insights. Additionally, in this issue of Joule, Ji-Guang Zhang, Wu Xu, and colleagues characterize the degradation incurred in practical scenarios with high-capacity utilization of lithium metal.

Behavior of Lithium Metal Anodes under Various Capacity Utilization and High Current Density in Lithium Metal Batteries

Summary Lithium (Li) metal batteries (LMBs) have recently attracted extensive interest in the energy-storage field after silence from the public view for several decades. However, many challenges still need to be overcome before their practical application, especially those that are related to the interfacial instability of Li metal anodes. Here, we reveal for the first time that the thickness of the degradation layer on the metallic Li anode surface shows a linear relationship with Li areal capacity utilization up to 4.0 mAh cm −2 in a practical LMB system. The increase in Li capacity utilization in each cycle causes variations in the morphology and composition of the degradation layer on the Li anode. Under high Li capacity utilization, the current density for charge (i.e., Li deposition) is identified to be a key factor controlling the corrosion of the Li metal anode. These fundamental findings provide new perspectives for the development of rechargeable LMBs.

A Freestanding Selenium Disulfide Cathode Based on Cobalt Disulfide-Decorated Multichannel Carbon Fibers with Enhanced Lithium Storage Performance.

SeS2 shows attractive advantages beyond bare S and Se as a cathode material for lithium storage. Here, a freestanding lotus root-like carbon fiber network decorated with CoS2 nanoparticles (denoted as CoS2 @LRC) has been designed and prepared as the SeS2 host for enhancing the lithium storage performance. The integrated electrode is constructed by three-dimensional interconnected multichannel carbon fibers, which can not only accommodate high content of SeS2 (70 wt %), but also promise excellent electron and ion transport for achieving high capacity utilization of 1015 mAh g-1 at 0.2 A g-1 . What is more, there are numerous CoS2 nanoparticles decorated all over the inner walls and surfaces of the carbon fibers, providing efficient sulfiphilic sites for restricting the dissolution of polysulfides and polyselenides during the electrochemical processes, thus successfully suppressing the shuttle effect and maintaining excellent cycling stability over 400 cycles at 0.5 A g-1 .

A Freestanding Selenium Disulfide Cathode Based on Cobalt Disulfide‐Decorated Multichannel Carbon Fibers with Enhanced Lithium Storage Performance

AbstractSeS2 shows attractive advantages beyond bare S and Se as a cathode material for lithium storage. Here, a freestanding lotus root‐like carbon fiber network decorated with CoS2 nanoparticles (denoted as CoS2@LRC) has been designed and prepared as the SeS2 host for enhancing the lithium storage performance. The integrated electrode is constructed by three‐dimensional interconnected multichannel carbon fibers, which can not only accommodate high content of SeS2 (70 wt %), but also promise excellent electron and ion transport for achieving high capacity utilization of 1015 mAh g−1 at 0.2 A g−1. What is more, there are numerous CoS2 nanoparticles decorated all over the inner walls and surfaces of the carbon fibers, providing efficient sulfiphilic sites for restricting the dissolution of polysulfides and polyselenides during the electrochemical processes, thus successfully suppressing the shuttle effect and maintaining excellent cycling stability over 400 cycles at 0.5 A g−1.

In Situ Grown Fe2O3 Single Crystallites on Reduced Graphene Oxide Nanosheets as High Performance Conversion Anode for Sodium-Ion Batteries.

Electrochemical conversion reactions of metal oxides provide a new avenue to build high capacity anodes for sodium-ion batteries. However, the poor rate performance and cyclability of these conversion anodes remain a significant challenge for Na-ion battery applications because most of the conversion anodes suffer from sluggish kinetics and irreversible structural change during cycles. In this paper, we report an Fe2O3 single crystallites/reduced graphene oxide composite (Fe2O3/rGO), where the Fe2O3 single crystallites with a particle size of ∼300 nm were uniformly anchored on the rGO nanosheets, which provide a highly conductive framework to facilitate electron transport and a flexible matrix to buffer the volume change of the material during cycling. This Fe2O3/rGO composite anode shows a very high reversible capacity of 610 mAh g-1 at 50 mA g-1, a high Coulombic efficiency of 71% at the first cycle, and a strong cyclability with 82% capacity retention after 100 cycles, suggesting a potential feasibility for sodium-ion batteries. More significantly, the present work clearly illustrates that an electrochemical conversion anode can be made with high capacity utilization, strong rate capability, and stable cyclability through appropriately tailoring the lattice structure, particle size, and electronic conduction channels for a simple transition-metal oxide, thus offering abundant selections for development of low-cost and high-performance Na-storage electrodes.

Insights into the Ultra-Fast Li Storage Properties of Organic Polymers

Organic materials have long been recognized as resource-abundant, sustainable, and potentially low-cost electrode materials that will handily satisfy the ever-growing demand for batteries. Although once had the reputation as being less stable and kinetically slow compared with their traditional inorganic counterparts, organic materials have been steadily improving on performance to be competent electrode candidates in recent years. We have recently reported a π-conjugated redox polymer with high cycling stability, high capacity utilization, and ultra-fast Li storage kinetics. The polymer delivers 80% of its theoretical capacity at a rate of 50C even with a high active mass ratio of 80 wt.% at practical mass loading, which is unusual for organic electrode materials. There is no established theory as for how such performance can be achieved and optimized via molecular design and microstructure engineering. We set out to scrutinize the charge storage mechanism of polymer electrodes and investigate the influence of molecular electronic structure and electrode microstructure on electrochemical performance. We have designed and synthesized a series of polymers with similar molecular structure but varying degree of conjugation in the backbone. The polymers are evaluated as Li storage electrode materials. The morphology and its evolution, charge transfer process, and state-of-charge-dependent electron and ion transport of the polymer electrodes are monitored and correlated to the cell performance. We found that regardless of the degree of conjugation, the redox reaction and the bulk ionic diffusion in the polymers proceed at comparable rates. We developed a procedure to directly measure the electrical conductivity of electrochemically lithiated polymers. This conductivity increases by 100-fold as the π-conjugation degree of the polymers increases. The structural order and morphology of the polymers differ widely with the conjugation length, leading to significantly different microstructure. The electrochemical surface area of the polymer electrode is continuously altered by the π-conjugation degree, which in turn impacts the ion transport model in the electrode. Overall, our study establishes general analysis tools that elucidate the underlying charge storage mechanism of polymer electrode materials. The results shown here provide guidance for further advancing high-energy/power energy battery based on organic materials.

Statistical investigation on train primary delay based on real records: evidence from Wuhan–Guangzhou HSR

ABSTRACTThe focus of this study was to conduct statistical analysis on primary delays in Wuhan–Guangzhou high-speed railway (HSR). The main statistics of primary delays were investigated, including delay causes, delay frequencies, delays’ temporal and spatial occurrences, affected number of trains, and delay recovery patterns. Models that can illustrate the primary delays duration and the number of affected trains were developed. Namely, the log-normal and the Weibull distributions are tested, and the results affirm that the former one can better approximate the duration of primary delays. Subsequently, a non-linear regression model to fit the distribution of the affected number of trains was presented. The temporal and spatial analysis of primary delays and capacity utilization show that there is a high degree of dependency between the periods with high delay frequency and capacity bottlenecks. Specifically, wherever there is a high capacity utilization rate, there is a high probability of delay occurrence. This study provides insightful findings that help in understanding the primary delays in HSR operation and conducting further research.

An Empirical Analysis of Capacity Costs

This study uses a confidential Census sample of 151,900 U.S. manufacturing plant-years from 1974-2011 to investigate the impact of excluding the costs of unused capacity from key financial indicators, namely product costs and gross margins. We estimate the magnitude of unused capacity cost as a percent of sales to be about 4.8 percent, which for Compustat manufacturing firms in 2011 amounts to $142 billion (by comparison, the well-researched topic of R&D expense totals to $223 billion). We find that excluding the cost of unused capacity decreases product costs by approximately 6 percent and increases gross margins by around 26 percent. These magnitudes are economically significant and pervasive across industries and over time. Excluding the cost of unused capacity also smooths the time-series variation in unitized product costs and gross margins, with the standard deviation of gross margins declining (significantly) by 5 percent. Additional analyses indicate the presence of congestion and other costs at high capacity utilization levels, as predicted by the operations literature.